diets, habitat preferences, and niche differentiation of ... · florida cenozoic sirenians 299...

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Paleobiology, 30(2), 2004, pp. 297–324

Diets, habitat preferences, and niche differentiation of Cenozoicsirenians from Florida: evidence from stable isotopes

Bruce J. MacFadden, Pennilyn Higgins, Mark T. Clementz, and Douglas S. Jones

Abstract.—Cenozoic sediments of Florida contain one of the most highly fossiliferous sequences ofextinct sirenians in the world. Sirenians first occur in Florida during the Eocene (ca. 40 Ma), havetheir peak diversity during the late Oligocene–Miocene (including the widespread dugongid Me-taxytherium), and become virtually extinct by the late Miocene (ca. 8 Ma). Thereafter during thePliocene and Pleistocene, sirenians are represented in Florida by abundant remains of fossil man-atees (Trichechus sp.). Stable isotopic analyses were performed on 100 teeth of fossil sirenians andextant Trichechus manatus from Florida in order to reconstruct diets (as determined from d13C val-ues) and habitat preferences (as determined from d18O values) and test previous hypotheses basedon morphological characters and associated floral and faunal remains. A small sample (n 5 6) ofextant Dugong dugon from Australia was also analyzed as an extant model to interpret the ecologyof fossil dugongs.

A pilot study of captive manatees and their known diet revealed an isotopic enrichment («*) ind13C of 14.0‰, indistinguishable from previously reported «* for extant medium to large terrestrialmammalian herbivores with known diets. The variation in d18OV-SMOW reported here is interpretedto indicate habitat preferences, with depleted tooth enamel values (ø25‰) representing freshwaterrivers and springs, whereas enriched values (ø30‰) indicate coastal marine environments. Takentogether, the Eocene to late Miocene sirenians (Protosirenidae and Dugongidae) differ significantlyin both d13C and d18O from Pleistocene and Recent manatees (Trichechidae). In general, Protosirenand the fossil dugongs from Florida have carbon isotopic values that are relatively positive (meand13C 5 20.9‰) ranging from 24.8‰ to 5.6‰, interpreted to represent a specialized diet of pre-dominantly seagrasses. The oxygen isotopic values (mean d18O 5 29.2‰) are likewise relativelypositive, indicating a principally marine habitat preference. These interpretations correlate wellwith previous hypotheses based on morphology (e.g., degree of rostral deflection) and the knownecology of modern Dugong dugon from the Pacific Ocean. In contrast, the fossil and extant Trichechusteeth from Florida have relatively lower carbon isotopic values (mean d13C 5 27.2‰) that rangefrom 218.2‰ to 1.7‰, interpreted as a more generalized diet ranging from C3 plants to seagrasses.The relatively lower oxygen isotopic values (mean d18O 5 28.1‰) are interpreted as a more diversearray of freshwater and marine habitat preferences than that of Protosiren and fossil dugongs. Thisstudy of Cenozoic sirenians from Florida further demonstrates that stable isotopes can test hy-potheses previously based on morphology and associated floral and faunal remains. All these datasets taken together result in a more insightful approach to reconstructing the paleobiology of thisinteresting group of ancient aquatic mammalian herbivores.

Bruce J. MacFadden, Pennilyn Higgins, and Douglas S. Jones. Florida Museum of Natural History, Uni-versity of Florida, Gainesville, Florida 32611. E-mail: [email protected], E-mail: [email protected], and E-mail: [email protected]

Mark T. Clementz.* Department of Earth Sciences, University of California, Santa Cruz, California 95064.

Accepted: 15 August 2003

Introduction

Extant sirenians are fully aquatic mamma-lian herbivores that constitute the Order Sir-enia. One of the two modern sirenian families,the Dugongidae, with an extant monotypicgenus of hypergrazer, the dugong (Dugong du-gon), is widely distributed in coastal marine

* Present address: Smithsonian Marine Station at FortPierce, 701 Seaway Drive, Fort Pierce, Florida 34949.E-mail: [email protected]

waters throughout the subtropical and tropi-cal Pacific and Indian Oceans (Walker 1975;Husar 1978a). The second family, the Tri-chechidae, consists of a single genus, Triche-chus, the manatee, a mixed-feeding herbivorewith three species distributed throughout riv-ers, estuaries, and coastal marine areas of thetropical and subtropical Atlantic Ocean. Ofrelevance to the present study, the manateenative to Florida is referred to T. manatus lati-rostrius, the West Indian Manatee (Walker

298 BRUCE J. MACFADDEN ET AL.

1975; Husar 1978b). Despite this limited mod-ern diversity and disjunct distribution, whichis further threatened by human impact, sire-nians have had a rich and fascinating macro-evolutionary history of diversification and ad-aptation over the past 50 million years sincetheir split from the basal Tethytheria (a cladealso including proboscideans [McKenna andBell 1997]).

One of the richest and most extensive fossilrecords of sirenians occurs in the nearshore,shallow marine and estuarine sediments ex-posed throughout Florida (Hulbert 2001), andthis sequence is critical to understanding thediversification of this order. The systematics,morphology, and adaptive hypotheses con-cerning these sirenians have been treated ex-tensively in earlier descriptions (e.g., Simpson1932; Reinhart 1976) and in a series of morerecent papers by Domning (e.g., 1988, 1989a,b,1990, 1994, 1997a).

In addition to developing a modern system-atic framework for the Sirenia, Domning (e.g.,1981, 2001a) has developed hypotheses aboutthe diet and ecology of extinct dugongs andmanatees based on those of modern sirenians,morphological correlates in the fossil record,and associated geological and paleontologicalevidence. Domning (2001a) defines the‘‘aquatic megaherbivore adaptive zone’’ andexplains how different sirenians partitionfood resources and other aspects of individualspecies niches. Modern dugongs are predom-inantly grazers, feeding on seagrasses (Hy-drocharitaceae and Potamogetonaceae), al-though they also eat algae when seagrassesare limited or unavailable. These sirenians arecharacterized by bunodont (bulbous-cusped)cheek teeth with limited tooth replacementand a high degree of rostral deflection (Fig.1E), which indicates the use of the down-turned snout for digging up seagrasses, in-cluding their rhizomes. This high degree ofrostral deflection (up to 708 [Domning 1977])can be traced back into the fossil record to themiddle Eocene, and for extinct dugongs islikewise interpreted as an adaptation to feed-ing on ancient seagrasses. Paleontological ev-idence suggesting the long-standing sea cowand seagrass plant-animal coevolutionary in-terrelationship first comes from the middle

Eocene of Florida (Ivany et al. 1990), demon-strating very well preserved seagrass beds(with Thalassia-like taxa similar to those of theCaribbean basin today) associated with fossilsirenian bones referable to Protosiren sp.(Domning et al. 1982; Hulbert 2001).

In contrast to the specialized seagrass graz-ing of dugongs, manatees are considerablymore generalized mixed-feeders, with Triche-chus manatus latirostrius reported to consumeover 60 plant species in Florida (Ames et al.1996). In addition to seagrasses, the diet of Tri-chechus can consist of an array of freshwaterand marshy vegetation, including a consider-able proportion of true grasses (Poaceae) suchas Distichlis, Spartina, Paspalum, and Panicum(Domning 1982, 2001a). The rostral deflectionangle of Trichechus is relatively weak (,408;Fig. 1F; Domning 2001a). With the exceptionof the earliest trichechid Potamosiren magdalen-sis from the middle Miocene of Colombia(Domning 1997b), other manatees have rela-tively short-crowned teeth that are shed andcontinually replaced ‘‘conveyor-belt’’-stylefrom back to front throughout ontogeny. Thiscontinuous source of teeth is interpreted as aninitial adaptation to feeding on abrasive grass-es (Domning 1982, 1997b, 2001b), althoughmore recently manatees have adapted to amore diverse herbivorous diet.

Within the past decade, stable isotopes havebecome increasingly useful in reconstructingthe paleoecology and paleoenvironment of ex-tinct vertebrates. The original literature onthis subject is expanding rapidly (see, e.g.,Koch 1998 for recent review). These geochem-ical studies have allowed (1) testing of previ-ously existing hypotheses based on more tra-ditional (i.e., morphological) data, and (2) re-construction of various aspects of aut- andsynecology of vertebrate species and com-munities not previously discernable with con-ventional data. Studies of stable carbon iso-topes preserved in tooth enamel carbonatehave mostly concentrated on terrestrial ver-tebrates and communities in an attempt to re-construct ancient herbivore diets and theirfeeding adaptations on C3 or C4 plants. Stableoxygen isotopes, which have been used exten-sively in ancient marine ecosystems, havebeen more difficult to apply to terrestrial set-

299FLORIDA CENOZOIC SIRENIANS

FIGURE 1. Comparisons of degree of rostral deflection in extant and fossil sirenians. A, Primitive morphology inProrastomus sirenoides from the middle Eocene of Jamaica (adapted from Savage et al. 1994). B, Protosiren fraasi fromthe middle Eocene of Egypt (adapted from Domning 2001b). C, High degree of rostral deflection in Metaxytheriumfloridanum from the early Miocene Lower Bone Valley Formation, Florida (adapted from Domning 1988). D, Rela-tively little rostral deflection seen in Metaxytherium crataegense from the middle Miocene of Florida (adapted fromSimpson 1932). E, Extant Dugong dugon. F, Extant Trichechus manatus .

tings because of the high degree of variabilityof meteoric waters and the many factors influ-encing the ultimate oxygen isotopic compo-sition of tooth enamel carbonate. Some recentstudies have used stable oxygen isotopes tointerpret evolutionary transitions between ter-restrial versus marine habitats, e.g., the adap-tive radiation in Eocene whales (Roe et al.1998).

Current hypotheses about the evolution ofdiets and related functional adaptations of ex-tinct sirenians have been extensively de-scribed in the existing literature (see Domningreferences cited above). Of particular rele-vance here, stable isotopes of carbon and ox-ygen can be used to test the following hy-potheses about the diets and habitats of ex-tinct sirenians of Florida:

1. The relative degree of rostral deflection in-dicates dietary adaptations, with increasedflexure indicating a specialized seagrassdiet.

2. Like modern dugongs, extinct Florida pro-tosirenids and dugongs inhabited relative-ly marine waters, whereas Florida mana-tees have inhabited a broader range ofaquatic environments, including coastalmarine as well as freshwater, inland rivers.

Sequence of Cenozoic Sirenians fromFlorida

Taken together, all four sirenian families arerepresented in the nearshore marine and con-tinental deposits of Florida (Table 1). Al-though mention will be made of other sireni-ans, this discussion will principally focus on


TABLE 1. Fossil and extant Sirenia known from Florida. Taxa analyzed during the present study are presented inboldface, with the number of individual bulk samples analyzed in parentheses (also see Appendix). (Compiled fromDomning 1994, 2001a and Hulbert 2001).

Order Sirenia†Family Prorastomidae

Genus and species indeterminant

†Family ProtosirenidaeProtosiren sp., middle Eocene (Clairbornian); ?early Oligocene (4)

Family Dugongidae†Subfamily Halitheriinae

Metaxytherium sp., very late OligoceneMetaxytherium crataegense, late early to middle Miocene (3)Metaxytherium floridanum, middle to late Miocene (23)

Subfamily DugonginaeUndescribed small dugongid, middle MioceneCrenatosiren olseni, very late Oligocene to very early MioceneDioplotherium manigaulti, very late Oligocene to middle MioceneDioplotherium allisoni, early PlioceneCorystosiren varguezi, early Pliocene (1)Undescribed genera and species, Pliocene

Family TrichechidaeTrichechus sp., ?late Pliocene, early to late Pleistocene (45)Trichechus manatus latirostris, West Indian Manatee, the late Pleistocene (Rancholabrean) to Recent (18

wild, 6 captive)

those taxa for which stable isotopic results arepresented below. This discussion is separatedinto temporal intervals that represent theavailable isotopic samples, and not naturalphylogenetic groups.

Eocene to Early Oligocene (40–35 Ma). Theearliest and most primitive sirenian group,Family Prorastomidae, although better knownfrom the early to middle Eocene of Jamaica(Savage et al. 1994; Domning 2001c), is rep-resented by extremely fragmentary material(vertebrae) from the late Eocene of Florida thatwas not amenable to stable isotopic analysis.Prorastomidae are, so far as is known, char-acterized by a relatively flat rostral morphol-ogy (Fig. 1A) indicating little of the deflectionseen in other sirenians. Savage et al. (1994)speculated that Prorastomus was a selectivebrowser feeding on floating and emergentaquatic plants, and to a lesser degree, sea-grasses.

The Family Protosirenidae is somewhat bet-ter represented in Florida relative to the Pro-rastomidae, and an intimate association withfossil seagrasses has been observed. Ivany etal. (1990) described a diverse assemblage ofwell-preserved seagrass communities fromDolime Quarry, middle Eocene Avon Park

Formation of central Florida (Fig. 2). Theseseagrasses consist of Thalassodendron and Cy-modocea, genera believed to be very closely re-lated to the common Florida seagrass, Thal-assia (Ivany et al. 1990). Sirenian fossils re-ferred to Protosiren sp. are found in direct as-sociation with these seagrasses and aplant-herbivore interaction is implied. In con-trast to the more primitive condition seen inProrastomus, Florida Protosiren sp. is character-ized by a rostral deflection of 35–408 (Domn-ing et al. 1982) (Fig. 1B), implying increasedforaging on seagrasses.

It also should be noted that during the lateOligocene through early Miocene, several du-gongid species were present in Florida (Hul-bert 2001), including three (Metaxytherium sp.,Crenatosiren olseni, and Dioplotherium mani-gaulti) that coexisted at some localities (Domn-ing 1989a). Although diverse, teeth for thesesirenians are both rare and difficult to identifytaxonomically. Consequently these extinct du-gongids were unavailable for isotopic analy-sis.

Middle to Late Miocene (ca. 17–8 Ma). By farthe most common Miocene sirenian in theworld was Metaxytherium (Fig. 1C,D), and thisalso was the case in Florida (Domning 1988).


FIGURE 2. Map of localities discussed in text, including those from which specimens were sampled for this study.

The oldest records of this genus analyzed hereare from the early part of the middle Miocene,including (1) the La Camelia Mine, Haw-thorne Formation in the Florida panhandle(Bryant 1991); and (2) lowermost units of theBone Valley phosphate mines of central Flor-ida (Fig. 2). Both of these localities are Barsto-vian land mammal age (sensu Tedford et al.1987; this North American Land Mammal‘‘Age’’ [NALMA] is estimated to range fromabout 16 to 11.5 Ma). These oldest specimensare referred to Metaxytherium crataegense (Fig.1D) (Domning 1988; Bryant 1991; Hulbert2001). Thereafter, the extensive open-pit phos-phate mines of central Florida contain abun-dant sirenian remains in the Lower Bone Val-ley Formation, which Domning (1988) con-cluded are all referable to Metaxytherium flor-idanum (Fig. 1C). These fossils come from thelater part of the middle Miocene Agricola Fau-na and, according to land mammal biochro-nology, are early Clarendonian NALMA inage (Morgan 1994), ca. 12 Ma. Thereafter, du-gongs occur rarely in younger deposits in theBone Valley district, from localities such asNichols Mine, which are probably early Hem-phillian in age (Hulbert 1988). In north Flori-da, various creeks in the Gainesville area con-tain dugong remains of a form slightly differ-

ent from the Bone Valley Metaxytherium thatDomning (1988) refers to M. cf. floridanum. Me-taxytherium floridanum is characterized by arelatively high degree of rostral deflection(ø758, Fig. 1C), suggesting specialization onseagrasses (Domning 1988).

Late Miocene/Early Pliocene (7–4 Ma). TheMiocene/early Pliocene was a pivotal time inFlorida sirenian evolution. Unfortunately thefossil record of this interval is notably lacking.The diversity seen during the late Oligoceneand early Miocene drops, and dugongs areapparently not well represented after the mid-dle Miocene. The latest Miocene–early Plio-cene (late Hemphillian) Upper Bone ValleyFormation (ca. 5 Ma), which produces exten-sive interbedded terrestrial and marine mam-malian faunal assemblages (the Palmetto Fau-na [Morgan 1994; Hulbert 2001]), demon-strates a conspicuous absence of dugongs,probably representing a local near extinctionof sirenians. Two notable exceptions to the to-tal extirpation of Florida sirenians during thelate Miocene include an early Hemphillian oc-currence of Corystosiren varguei (also seeDomning 1990) and undescribed late-surviv-ing dugongids (Domning 2001a; Hulbert2001) from the late Miocene and early Plio-cene. It is indeed unfortunate that the fossil re-


cord of late Miocene–early Pliocene dugon-gids is not better represented, because this isthe time that most dugongids became extinctin the Atlantic and Caribbean, and the tri-chechids presumably radiated from SouthAmerica into this biogeographic province.This poor record of sirenian evolutionary his-tory in the Atlantic/Caribbean region has re-sulted in speculative hypotheses either aboutthe competitive superiority of manatees rela-tive to dugongs or, if they did not indeed co-exist and compete, about the manatees fillingthe aquatic megaherbivore niche vacated bythe regional extinction of dugongs in the At-lantic Ocean (Domning 1982, 2001a).

Early Pleistocene Through Recent (1.5 Ma to thePresent). So far as can be determined fromthe available fossil record, the Trichechidaeprobably arose in South America and is firstrepresented by Potamosiren magdalensis fromthe middle Miocene La Venta Fauna of Colom-bia (Domning 1997b). The dental morphologyof P. magdalensis indicates that the teeth werenot replaced continually during ontogeny asin more-derived manatees. Domning (1982,1997b) suggests that the diet of this mostprimitive known manatee consisted of softervegetation but did not include the abrasivetrue grasses (Poaceae) known to be part of thediet of the extant manatee Trichechus manatus.

Although there have been suggestions thatmanatees are first known in the middle Plio-cene (Blancan NALMA) of northern Floridaabout 2.5 million years ago (Domning 1982),for example from the Santa Fe River, more re-cent interpretations suggest that this faunalassemblage is mixed with Pleistocene (Ran-cholabrean) mammals; therefore, a definitiveolder, middle Pliocene, date cannot be deter-mined unambiguously (R. C. Hulbert person-al communication 2001). The first definitive, insitu record of Florida manatees is representedby Trichechus sp. from the 1.5-Ma IrvingtonianLeisey Shell Pit south of Tampa (Morgan andHulbert 1995). Having been derived from aSouth American ancestor (Domning 1982,1997b), the extinct Florida fossil manatees aremorphologically close to both T. manatus andthe West African T. senegalensis, and may rep-resent a distinct species. Pleistocene and Ho-locene Florida manatees are characterized by

horizontally replaced teeth that are continu-ally shed during ontogeny. These teeth arevery abundant in river localities from north-ern Florida of this age. Domning (1982, 2001a)suggests that late Pleistocene Trichechus sp.from Florida does not represent temporallysuccessive populations, but may instead rep-resent a sequence of genetically independent,multiple dispersal events into this region.Modern Florida manatees, Trichechus manatus,are characterized by a moderate degree of ros-tral deflection (Fig. 1F), indicating some sea-grass preference, although this species isknown to have a generalized diet (Ames et al.1996; Domning 1982, 2001a). Modern mana-tees are known to exist in a wider range ofhabitats than dugongs, with the former rang-ing from full marine on one hand to fresh-water rivers on the other (Husar 1978b).

In summary, the sequence of fossil sireniansin Florida, although discontinuous, coverssome very important stages in the evolution ofthis order. As will be demonstrated below, iso-topic analysis of specimens from this se-quence offers some interesting results and in-sights relative to previous hypotheses aboutancient diets and habitat preferences.

Stable Isotopes, Plant Foods, and HabitatReconstruction

Within the past few decades, stable isotopeshave become widespread as proxies for inter-preting and reconstructing the paleoecologyof extinct vertebrates (e.g., Koch 1998). Carbonand oxygen isotopes will be used here to re-construct, respectively, the diet and habitat ofsirenians from Florida. The conventional delta(d) notation is used here for carbon (d13C) andoxygen (d18O), where d (parts per mil, ‰) 5[(Rsample/Rstandard) 2 1] 3 1000, and R 5 13C/12C or 18O/16O. The data from the unknown(fossil) are compared relative to internation-ally accepted standards, which for d13C is V-PDB (Pee Dee Belemnite) and for d18O report-ed here relative to V-SMOW (Standard MeanOcean Water, both following Vienna conven-tion, hence ‘‘V-’’ [e.g., Coplen 1994]).

Carbon (d13C) and Ancient Diets. Plants frac-tionate carbon with one of three different pho-tosynthetic pathways. Most plants use theCalvin Cycle, in which carbon is incorporated


into three-carbon chain compounds, hence theterm ‘‘C3.’’ C3 plants include trees; shrubs;cool-growing-season, high-altitude and high-latitude grasses; and many aquatic plants, andrepresent about 85% of the world’s plant bio-mass. Tropical and temperate grasses, whichaccount for about 10% of terrestrial plant bio-mass, fractionate carbon into four-carbonchain compounds (as an intermediate productof photosynthesis), and hence the term ‘‘C4’’plants. Of relevance here, grasses that livealong the land/water interface photosynthe-size carbon by using either the C3 or C4 path-way depending upon species. The third pho-tosynthetic pathway, CAM (CrassulaceanAcid Metabolism), exemplified by Cactaceae(cactus) and Euphorbiaceae (euphorbia), con-stitutes the remaining percentage of plantphotosynthesis (Ehleringer et al. 1991). Inview of the fact that CAM plants do not con-stitute a part of the known diet of sirenians,particularly in Florida, this photosyntheticpathway is not considered further. In terres-trial ecosystems, C3 plants have a mean d13Cvalue of 227‰ and a broad range of 232‰to 223‰, whereas C4 plants have a mean d13Cof 213‰ with a narrower range of 215‰ to210‰ (Dienes 1980; Farquhar et al. 1989;Boutton 1991). Most fully marine plants (in-cluding seagrasses) fractionate carbon by us-ing the C3 pathway, although because the car-bon source in the oceans can be derived frombicarbonate as well as atmospheric CO2, thed13C values of C3 marine plants can be moreenriched than their terrestrial counterparts(Boutton 1991; Keeley and Sandquist 1992;Hemminga and Mateo 1996). The d13C ofcoastal aquatic plants is more complicated be-cause of the multiple sources of carbon fromwhich plants draw and fractionate (Boutton1991; Keeley and Sandquist 1992).

As mentioned above, the modern manateeTrichechus manatus eats more than 60 species ofaquatic (marine/freshwater) plants and thesespan a wide range of d13C values, approxi-mately 23‰ to 235‰ (Ames et al. 1996).Nevertheless, the diet of Trichechus manatusfrom Florida consists predominantly of sea-grasses (mostly Thalassia, Syringodium, Halo-dule, Halophila, Diplanthera, and Ruppia [Ameset al. 1996]), which have a mean d13C that

mostly falls into a narrow range between210‰ and 211‰ (Boutton 1991; Hemmingaand Mateo 1996), and Hydrilla, with a d13C of213‰ to 226‰ (Ames et al. 1996). It is im-portant to note here that Hydrilla is a non-na-tive species in Florida, introduced in the 1950s(Langeland 1990), and was not a major dietarycomponent for any of the sirenians examinedin this study. The remaining plant species inthe diet of T. manatus from Florida include(Ames et al. 1996) terrestrial C3 and C4 grass-es, macroalgae, mangroves, cattail (Typha sp.),and water hyacinth (Eichhomia), which togeth-er range widely in their d13C values (about25‰ to 235‰), but all of these are in rela-tively minor quantities.

When isotopes of carbon are incorporatedinto skeletal tissues, there is an isotopic en-richment («*) relative to the plant foods (i.e.,13C is selectively incorporated into skeletal tis-sues, resulting in a higher d13C value). For me-dium to large terrestrial modern mammals, «*is 14.1‰ (Cerling and Harris 1999), althoughlittle was previously known about this enrich-ment in marine mammals (also see discussionbelow).

Oxygen (d18O) and Habitat Preference. Incontrast to the relatively straightforward in-terpretation of carbon uptake and fraction-ation, and corresponding d13C values of toothenamel carbonate, understanding the array offactors affecting the isotopic fractionation ofoxygen in the environment and how oxygenis then metabolized by mammals is more com-plex. Thus, the inherent assumptions about in-terpreting the source and history of oxygen,and how it can be used to interpret ancient en-vironments, requires multiple assumptionsthat are difficult to unambiguously control. Itis well known that the fractionation of oxygenisotopes in the environment is a function oftemperature, and thus the classic use of d18Oas a paleothermometer. However, becausemammals maintain a constant body temper-ature, variation in enamel d18O values is notjust a result of temperature, but is influencedby physiological processes within the bodyand the d18O composition of various environ-mental sources of oxygen.

In terrestrial mammals, the two principalsources of oxygen are contained in the ani-


mals’ drinking water and in plant water. Thesetwo categories of ingested water frequentlyhave different isotopic values within the sameecosystem that can introduce a significantamount of variation in d18O values among in-dividuals in a population. Likewise, a varietyof physiological processes, including meta-bolic rate, sweating, panting, and excretion,can alter the magnitude and fractionation ofoxygen fluxes entering and leaving a mam-mal’s body water pool (Bryant and Froelich1995; Kohn 1996). These factors further in-crease the d18O values among individuals andpotentially complicate intraspecific and inter-specific comparisons of d18O values.

Fortunately, among aquatic species, the fac-tors affecting body water d18O values aregreatly reduced. Observations of captive ma-rine species suggest that the majority (.98%)of oxygen flux is the result of passive diffusionof environmental water across the skin (Hui1981; Andersen and Nielsen 1983). Therefore,the d18O value of an aquatic mammal’s bodywater should correlate strongly with the d18Ovalue of the environmental waters in which itlives (Yoshida and Miyazaki 1991), and pop-ulations of aquatic mammal species living inwaters of relatively homogeneous isotopiccomposition should yield low d18O variationamong individuals. The d18O value of anaquatic mammal’s body water is therefore la-beled by the d18O value of the water in whichit lives, and populations migrating betweenwaters of different d18O values should exhibithigher variation in d18O values than popula-tions remaining in a single, localized waterbody (Clementz and Koch 2001).

Ultimately, the ingested oxygen is in isoto-pic equilibrium with body tissues, includingthe hydroxylapatite of teeth. Tooth enamel ac-cretes during a small portion of an animal’slife span, on the order of months (dependingupon factors such as size). Enamel d18O valuesthereby serve as an archive of fluctuations in amammal’s body water d18O values during thetime of tooth mineralization (Bryant and Froe-lich 1995; Kohn 1996). This temporal variationwithin a tooth can introduce additional dif-ferences among individual d18O values basedupon the amount of enamel that is sampled.The d18O measured from tooth enamel of

modern mammals therefore represents theend result of all of these potential sources ofvariation. A similar interpretation is made forfossil teeth, with the additional considerationof possible secondary alteration of the initiald18O signature during fossilization. Despitethe possibility of diagenesis and earlier claimsto the contrary (particularly for fossil bone[Schoeninger and DeNiro 1982]), tooth enam-el d18O has been used for paleoenvironmentalinterpretations (e.g., Bocherens et al. 1996;Cerling and Sharp 1997; and MacFadden et al.1999).

Mean tooth enamel d18O values of modernand fossil sirenians are used as a proxy for re-constructing their habitat preferences throughtime, based upon the following model for d18Oof environmental water. Modern seawater hasa global average d18OV-SMOW value of 0.0‰ (bydefinition) and is relatively homogeneousworldwide (Hoefs 1997). Nevertheless, someof the greatest variations in seawater d18O areobserved in marginal marine settings wherethey result from the combined effects of fac-tors such as evaporation, continental runoff,upwelling, and ocean currents. Except in es-tuarine environments, measurements indicatethat the shallow marine coastal waters ofcoastal Florida are slightly enriched in 18Ocompared with the global mean (Swart et al.1996). Seawater from St. Augustine Beach(used as an internal standard in the Stable Iso-tope Laboratory of the Department of Geolog-ical Sciences, University of Florida) has amean d18O of 0.7‰. This supports the obser-vation of Swart et al. (1996) that the d18O ofFlorida ocean water lies between 0 and 1‰and is strongly influenced by the strength ofthe Loop Current output from the MississippiRiver as well as by evaporation (Ortner et al.1995).

In contrast, Florida freshwater settings gen-erally exhibit relatively depleted d18O values.Most rivers display a range of d18O values thatgenerally decrease with increasing distanceinland from the coast as a result of evapora-tion and fractionation during precipitation(Coplen and Kendall 2000). The isotopic com-position of precipitation, a major contributorto the riverine water budget, is highly variableacross Florida but generally averages about


FIGURE 3. Simple box model of potential d13C and d18Oend-member values of tooth enamel used to interpret,respectively, the diets and habitats of extinct Florida si-renians.

23‰ (Swart et al. 1989). Springs represent an-other important source of water for manyFlorida rivers and are frequently sought outby manatees during the colder months of theyear. Year-round monitoring of d18O during1998–99 at a typical spring (Hart Springs) lo-cated in north-central Florida recorded rela-tively depleted values; mean d18O 5 24.0‰,with monthly values ranging between 23.6‰and 24.4‰ (Jones and Quitmyer unpublisheddata). A U.S. Geological Survey analysis of sixFlorida rivers from different geographic re-gions within the state revealed mean d18O val-ues ranging from 20.1 to 23.9‰ (Coplen andKendall 2000). In a seventh river system, theEconlockhatchee from central Florida, themean d18O was 22.0‰ (Gremillion 1994).

Not all of Florida’s freshwater environ-ments, however, are characterized by low d18Ovalues. For instance, the large standing bodyof water that makes up the Everglades is iso-topically enriched in 18O (0 to 2‰) as a resultof sustained evaporation (Meyers et al. 1993;Swart et al. 1996). Fortunately, such exceptionsdo not appear to play a major role in the en-vironmental life history of Florida sirenians,past or present.

It is well documented that the d18O value ofglobal seawater has varied throughout the Ce-nozoic from 21.2‰ during the ‘‘greenhouse’’world of the Paleocene and early Eocene, tomodern values consistent with the late Ceno-zoic ‘‘icehouse’’ (Zachos et al. 2001). New geo-chemical proxies for seawater paleotempera-tures have allowed investigators to assess therelative contributions of temperature and icevolume to the global d18O record of marinecarbonates and thereby reconstruct seawaterd18O evolution during the Cenozoic (Lear et al.2000; Billups and Schrag 2002). On a regionalscale, the local d18O variations along Florida’sancient coasts and rivers remain poorly con-strained throughout the Cenozoic. However,these factors do not diminish the robustness ofthe present-day model; i.e., the d18O values offreshwater are depleted relative to seawater,and hence enamel d18O values of freshwater si-renians (see below) are lower than for theirmarine counterparts. We assert that this mod-el can be applied throughout the Cenozoic,particularly when anchored to the global sea-

water d18O curve (Lear et al. 2000; Billups andSchrag 2002), and can be used in the recon-struction of ancient habitat preference. Wetherefore use it to differentiate marine andfreshwater habitats for fossil sirenians fromFlorida.

A simple conceptual model with four the-oretical end-members (Fig. 3) is used below tointerpret the carbon and oxygen isotopic datafor the fossil sirenians from Florida. Thesedata are also compared with those from mod-ern sirenians with known diets and habitatpreferences. The abscissa is calibrated by end-members ranging from a specialized seagrassfeeder (tooth enamel d13C ø 4‰) to a predom-inantly C3 feeder (tooth enamel d13C ø213‰). The ordinate is calibrated by end-members ranging from individuals living inrelatively freshwater habitats (tooth enameld18O ø 25‰) to those inhabiting marine sea-water (d18O ø 30‰). Thus, starting in the up-per right-hand corner of the model, individ-uals with relatively positive d13C and d18Oend-member values are interpreted to feedmainly on seagrass and live in principally ma-rine habitats. A modern analog for this is thedugong (Dugong dugon) from the PacificOcean (Husar 1978a). In the lower right-handcorner, individuals with relatively positived13C and negative d18O values would be inter-preted to feed mostly on seagrass and mainlylive in freshwater habitats. This combinationof diet and habitat is rare in nature becauseseagrasses are primarily marine, but perhaps


was represented in the past. In the lower lefthand corner, individuals with relatively neg-ative d13C and d18O values are interpreted tofeed principally on C3 aquatic plants and livein predominantly freshwater habitats. Popu-lations of the extant West Indian manatee (Tri-chechus manatus) from Florida are known totrend towards this kind of diet and habitat(Husar 1978b; Ames et al. 1996). In the upperleft-hand corner, individuals with more neg-ative d13C and more positive d18O valueswould be interpreted to have a diet of mainlyC3 plants (i.e., excludes seagrasses) and live inmarine habitats. A potential sub-Recent ana-log within the Sirenia for this marine C3 feederend-member is the Steller’s Sea Cow (Hydro-damalis gigas) from the North Pacific Oceanthat principally ate kelp (mean d13C of 219‰6 1‰ [compiled from Hobson et al. 1994; Si-menstad et al. 1993]) and was hunted to ex-tinction in 1768 (Domning 1999).

Materials and Methods

Stable Isotope Sample Acquisition (Teeth, Food,and Water). Six naturally shed teeth of live,captive Florida manatees collected from thebottom of their enclosures were borrowed foranalysis from the Mote Marine Laboratory,Sarasota (‘‘Hugh’’ or ‘‘Buffett’’; also see Ameset al. 1996), and from the South Florida Mu-seum (‘‘Snooty’’) in accordance with a U.S.Fish and Wildlife Service permit. Hugh andBuffett, two male manatees, were born at theMiami Seaquarium (Hugh, 28 June 1984; Buf-fett, 16 May 1987) and have spent their entirelives in captivity. Although both manatees arenearly the same length (298 and 313 cm re-spectively), Buffett is much heavier, weighingabout 660 kg to Hugh’s 535 kg (D. Colbert per-sonal communication 2001). Because Hughand Buffett share the same enclosure, it is notpossible to determine from which individualthe shed teeth were derived. Snooty is anothermale manatee that has also spent his entire lifein captivity. He is the oldest manatee in cap-tivity and was born 21 July 1948, at the MiamiAquarium. Snooty weighs about 455 kg (C.Audette personal communication 2001). Man-atee food and water were collected from theirtanks for isotopic analysis.

Eighteen tooth samples of the extant West

Indian Manatee, Trichechus manatus, from Flor-ida cataloged in the skeletal collection of theFlorida Museum of Natural History MammalCollection (abbreviation ‘‘UF M’’; Appendix)were analyzed in accordance with the U.S.Fish and Wildlife Service permit. With the ex-ception of one specimen from La Venta, Co-lombia (see further discussion below), all iso-topic analyses of fossil sirenians are from Flor-ida, with 67 specimens from the Florida Muse-um of Natural History Vertebrate PaleontologyCollection (abbreviation ‘‘UF’’) and nine speci-mens from the private fossil collection of JohnWaldrop (abbreviation ‘‘JW’’) of Lake Wales,Florida. Residual sample powders of the JWspecimens used for isotopic analysis are ar-chived in the UF collection.

Tusk samples of six modern dugongs werecollected from populations within the TorresStraits off the coast of Australia by the Schoolof Tropical Environment Studies and Geog-raphy at James Cook University in Queens-land, Australia. This dugong population wasselected as a modern analog because it hasbeen studied extensively by researchers atJames Cook University, providing a long re-cord of observational data on the ecology ofthis population (Marsh et al. 1984; Nietsch-mann 1984; Marsh 1986; Marsh and Saalfield1991). These studies confirm that dugongs arestrictly marine mammals specializing on sea-grasses with only minor amounts of marinealgae in their diet. Most importantly, no re-cords suggest any habitation of freshwatersites or inclusion of freshwater plants in theirdiets.

Isotope Sample Preparation, Analyses, Stan-dardization, and Conventions. Bulk sampleswere mechanically drilled from teeth, by us-ing either a Foredomy variable speed drill ora Dremely tool. Sirenians other than dugongs(see below) were sampled by collecting asmall sample of powdered enamel from somepoint along the tooth. The exact sample loca-tion was based on tooth preservation, ease insampling, and minimizing destruction of di-agnostic morphology. Serial samples were re-moved from one Metaxytherium tooth, onecaptive Trichechus tooth, and two fossil Triche-chus teeth to assess the isotopic variation alongthe length of a tooth. Dugong tusks (Dugong


dugon) from Australia were sectioned longi-tudinally and bulk samples were collected bydrilling the edge of the tusk across severalsuccessive growth bands. This method al-lowed homogenization of several years ofgrowth and provides a robust estimate of theaverage isotopic values for each individual.Sample sizes prior to preparation were char-acteristically about 100–300 mg for off-line ex-traction and 10–25 mg for on-line extraction.

Following standard protocol (e.g., as de-scribed in MacFadden and Cerling 1996), sam-ples were pulverized by using a mortar andpestle, then treated with either NaOCl or 30%H2O2 overnight to remove any surficiallybound organic compounds and then with 1 Nor 0.1 N acetic acid (some were also bufferedfollowing recommendations in Koch et al.1997). For off-line extractions (done at the Uni-versity of Utah), approximately 50–100 mg ofthe treated powders was reacted with H3PO4

for 40–48 hours at 258C. The evolved CO2 sam-ples were then purified and extracted follow-ing standard cryogenic laboratory procedures(McCrea 1950). Previous analyses of toothenamel carbonates have demonstrated thepresence of a contaminant, probably SO2 (e.g.,MacFadden et al. 1996), that will significantlyaffect the carbon and oxygen isotopic valuesof the tooth enamel carbonate sample. Accord-ingly, all off-line enamel CO2 samples werecollected in sample tubes containing Ag wooland then heated for at least 24 hours at 508C.This essentially removes this contaminantfrom the purified sample. Off-line extractedsamples were measured on a Finnigan massspectrometer in the Department of BiologySIRFER laboratory at the University of Utah.

For on-line extractions, approximately 1 mgwas weighed and loaded into an Isocarb ex-traction carousel (University of California-Santa Cruz) or individual reaction vessels ona multiprep device at the UF. The sampleswere reacted with H3PO4 (for varying timesand temperatures, depending on instrumentand inlet system used) and then purified andextracted for analysis on either a VG Prism(UF) or a Micromass Optima mass spectrom-eter (UCSC).

The diet of the captive manatees used in thisstudy consists principally of romaine lettuce.

Hugh and Buffett also are fed a large quantityof kale. Other foods added to supplementtheir diet are relatively minor (,1% each).Samples of all foodstuffs consumed by thesemanatees were collected for isotopic analysis.All samples were dried in an oven and theneach was pulverized. The carbon isotopes foreach of these organic samples were measuredwith the Carlo Erba CNS Analyzer in the Uni-versity of Florida Department of GeologicalSciences. Water samples were collected by dip-ping samples from the surface of the tank andalso directly from the fill spigot for each of thetwo tanks housing captive manatees. Watersamples were equilibrated with CO2 at 458Cfor 5 hours before CO2 is drawn into and mea-sured by the VG Prism mass spectrometer atthe University of Florida.

In all cases, unknown sample analyses werecalibrated to either internal laboratory stan-dards (TEC-CC, Carrera Marble, MEme, orUCSC elephant enamel) or NBS-19, and ulti-mately back to the V-PDB or V-SMOW stan-dards (Coplen 1994). Analytical precision foreach mass spectrometer is characteristicallybetter than about 0.1‰ for d13C and 0.2‰ ford18O.

Results and Discussion

Isotopic Fractionation in Modern Sirenian Food,Water, and Tooth Enamel Carbonate. Previousstudies have shown that tooth enamel d13Cvalues of mammalian herbivores are enrichedrelative to ingested plant foods. For mammalsin general, this isotopic enrichment has beenstated to be approximately 12–14‰ (e.g., Kochet al. 1992) for medium to large mammalianherbivores. Body size may be a contributingsource of variation. Ambrose (1998) found thatsmall mammals, i.e., lab rats, have a signifi-cantly lower mean isotopic enrichment of9.4‰. Using extensive analytical data from awide variety of extant medium to large mam-malian herbivores with known diets, Cerlingand Harris (1999) calculated that the meanisotopic enrichment («*) for tooth enamel car-bonate relative to diet is 14.1 6 0.5‰. As mostprevious studies have dealt with terrestrialmammalian herbivores, little is known aboutthe corresponding «* for marine mammals, in-cluding sirenians. Ames et al. (1996) analyzed


TABLE 2. Stable isotopic composition (d13CV-PDB) of manatee food and isotopic enrichment (e*, sensu Cerling andHarris 1999) for Hugh/Buffett and Snooty.

Sample number Material Amount d13C (‰)

Mote Marine Laboratory, Hugh/BuffettPH 01–06PH 01–07PH 01–08PH 01–09PH 01–10PH 01–11

RomaineKaleMonkey biscuitCarrotAppleBeet

96 heads/day/2 manatees12 heads/day/2 manatees12–16/day

K1%K1%K1%weighted mean1 5

227.8230.7221.3227.8224.7226.7227.9

South Florida Aquarium, SnootyPH 01–12PH 01–13PH 01–14PH 01–15PH 01–16PH 01–17PH 01–18

RomaineRomaineMonkey chowElephant chowAppleBroccoliSweet potato

200 lbs/day/2 manatees200 lbs/day/2 manatees

3%K1%K1%K1%K1%weighted mean2 5

227.8228.1219.8226.5224.4225.7223.7227.4

Isotopic enrichment between food and tooth enamel carbonate d13C:d13C values (Appendix) used to calculate mean enrichment e* include Hugh/Buffett (5 samples) and Snooty (1sam-ple) each subtracted from weighted mean of food source above yields isotopic enrichment of 14.0‰.

1 Approximate d13C for average daily intake of Hugh and Buffett, where for total diet, romaine 5 85%, kale 5 11%, monkey biscuit 5 3%, and all otherfoods ø 1%.

2 Approximate d13C for average daily intake of Snooty, where for total diet, romaine 5 96%, monkey biscuit 5 3%, and all other foods ø 1%.

the d13C values of known plant food and softtissues (liver, kidney, blubber, and skin) ofHugh and Buffett, then at the Lowry Park Zoo,Tampa (later moved to Mote Marine Labora-tory), but no teeth were analyzed during thatstudy.

Given the lack of existing data from whichto model the «* of modern sirenians, and thenby inference, fossil sirenians from Florida,known food and naturally shed teeth ofHugh/Buffett and Snooty were analyzed. Apotential source of error is introduced fromteeth that were shed and collected from thebottom of the manatee’s tanks prior to the timethat we actually collected the plant foods forisotopic analysis. Therefore, the assumption isthat the carbon isotopic values of the diet in-corporated into the teeth were relatively con-stant over the time interval between which theteeth were mineralized and shed and the dietwas analyzed. Information provided by theanimal keepers (also see Ames et al. 1996) in-dicated that the diet remained constant, con-sisting principally of romaine lettuce (.96%),with the remaining 4% including kale, carrots,apples, beets, broccoli, sweet potato, and com-mercially available monkey biscuits and ele-phant chow. Our analytical results (Table 2)

indicate that the mean d13C value of ingestedfoodstuffs was 227.9‰ for Hugh/Buffett and227.4‰ for Snooty, both of which are close tothe mean d13C value for C3 terrestrial plants(Dienes 1980; Farquhar et al. 1989; Boutton1991). Using five teeth from Hugh/Buffettand one tooth from Snooty (Appendix), andwith the known isotopic composition of thefood, we report here the calculated isotopicenrichment («*) of 14.0‰. This is essentiallythe same value determined for terrestrialmammalian herbivores (14.2‰ [Cerling andHarris 1999]), and is the model used to inter-pret the isotopic enrichment between fossil si-renians from Florida and their ancient diets.

Eight water samples, representing eithertap fill or tank water, were analyzed from theenclosures containing the captive manatees toattempt a calculation of an enrichment factorbetween d18O of environmental water andtooth enamel. For Hugh/Buffett the mean fillwater d18O is 22.1‰ (n 5 2) and 21.0‰ (n 52) for the tank water. For Snooty the mean fillwater is 20.3‰ (n 5 2) and 0.0‰ (n 5 2) forthe tank water. Despite the fact that these wa-ter samples are nonsaline, their isotopic valueslie close to expected values for marine water.We interpret the slightly more positive tank


TABLE 3. Stable isotopic values indicating intra-tooth variation in teeth of fossil and extant Florida sirenians.

Approximate position from base of enamel, mm(proportion with respect to tooth height) d13C (‰) d18O (‰)

Metaxytherium floridanum, UF JW F6912, Bone Valley-Kingsford-0, ca. 10 Ma14.5 mm (0.86)11.5 mm (0.64)8.5 mm (0.47)4.5 mm (0.25)

Mean, Standard Deviation, range

20.421.121.421.6

21.1, 0.5, 1.2

30.128.628.927.7

28.8, 1.0, 2.4

Hugh or Buffett, Trichechus manatus , captive, UF uncataloged, Recent5.5 mm (0.61)3.5 mm (0.39)1.5 mm (0.17)

Mean, Standard Deviation, range

215.0214.4213.5

214.3, 0.8, 1.5

27.026.926.8

26.9, 0.1, 0.2

Trichechus sp., Oklawaha River I, UF uncataloged, ca. 0.025 Ma7.5 mm (0.83)6 mm (0.67)

4.5 mm (0.50)3 mm (0.33)

1.5 mm (0.17)Mean, SD, range

1.31.21.11.52.6

1.5, 0.6, 1.5

31.030.430.230.332.2

30.8, 0.8, 2.0

Trichechus sp., Oklawaha River I, UF uncataloged, ca. 0.025 Ma8 mm (0.98)

6.5 mm (0.72)4.5 mm (0.50)3 mm (0.33)

1.5 mm (0.17)Mean, Standard Deviation, range

211.0211.7210.229.728.2

210.1, 1.4, 3.5

30.530.030.430.530.9

30.4, 0.3, 0.9

water to represent the effect of evaporation.Given the small sample size and ambiguousresults, these data are not used either to rep-resent a good model for the d18O of Floridanatural freshwater or to calculate an enrich-ment factor between the d18O of tooth enamelrelative to environmental water.

Isotopic Variation along the Sirenian ToothCrown. Most specimens analyzed duringthis study consisted of one bulk sample re-moved from an individual tooth. Recent stud-ies have shown that isotopic variation alongthe crown of modern and fossil mammal teethcan be used to explore climatic and dietaryvariation over the period of time during whichthe tooth mineralizes (e.g., Bryant et al. 1996;Cerling and Sharp 1997). The actual time ofmineralization of individual sirenian teeth ispoorly known (D. Domning personal com-munication 2003), but judging from eruptionsequence (Domning and Hayek 1984) andtooth development in other medium-sizedmammals (references in Bryant et al. 1996),this probably occurs over a period of many

months to about a year in manatees and othersirenians.

To understand isotopic variation in Floridasirenians, we selected four teeth for serialsampling. Three of these represent Trichechus(one extant captive and two late Pleistocenespecimens) and the fourth represents MioceneMetaxytherium (Table 3). We selected the teethfrom the captive individuals (Hugh/Buffett),realizing that these manatees are fed on anisotopically monotonous diet and live in anenclosure with an isotopically homogeneouswater source. We therefore predicted relative-ly little variation in tooth enamel d13C or d18O.In contrast, the late Pleistocene Trichechusfrom the Oklawaha River and Miocene Metax-ytherium should demonstrate isotopic varia-tion representing diets and habitat of wildpopulations as archived within individuals.

The stable isotopic data for the captive Tri-chechus, i.e., Hugh/Buffett, show relatively lit-tle variation in both d13C (range 1.5‰) andd18O (range of 0.2‰). This would be expectedgiven both the monotonous diet (Table 2) and


source of water used for the tank enclosure.The data for the fossil specimens demonstratemore variation in d13C and d18O as might bepredicted from diversity in diets and probablehabitats. The dugongid Metaxytherium is gen-erally believed to have had a specialized diet,corroborated by the narrow range (1.2‰) ofd13C values. The corresponding d18O valuesshow a 2.4‰ range, indicating some slightvariability in habitat, ranging from relativelymarine (30.1‰) to more mixed, or freshwater(27.7‰). The late Pleistocene Trichechus spec-imens indicate a wide range of diets amongindividuals (a mean of 1.5‰ indicates sea-grasses feeding in one individual, whereas amean of 210.1‰ indicates a diet of principal-ly C3 plants in the other). The mean d18O val-ues of 30.8 and 30.4‰ suggest relatively ma-rine environments and the narrow range (2.0and 0.9‰) suggests that the manatees inhab-ited these environments for the time that theteeth were mineralized. Several major pointsare evident from the data from the serial anal-yses: (1) the small amount of isotopic variationpredicted from the captive manatee fed on amonotonous diet and living in a constantsource of water is corroborated; (2) the extinctdugongid and fossil manatee Trichechus dem-onstrated more isotopic variation, but this isno more than 1.5‰ for d13C and 2‰ for d18O.This suggests that the far greater degree of to-tal isotopic variation (22.3‰ for d13C and9.2‰ for d18O; Table 4, Appendix) seen in thebulk sample data presented elsewhere in thispaper cannot be accounted for within thedemonstrated limits of individual isotopicvariation that would be expected during thetime interval when the tooth mineralized.

Stable Isotopes, Ancient Diets, and Habitat Pref-erences. To determine differences in habitatas represented by d13C and d18O data, we usedANOVA to compare four groups of toothenamel data for Florida sirenians: (1) Eocene–early Oligocene Protosiren (n 5 4); (2) MioceneMetaxytherium, including all samples of M.crataegense, M. floridanum, and M. cf. floridanum(n 5 26); (3) extinct ?Plio-Pleistocene Triche-chus sp. (n 5 45); and (4) modern wild T. man-atus (n 5 18) (Table 4; see raw data in Appen-dix). One specimen, Corystosiren varguezi (UF18826), from the early Hemphillian Waccasas-

sa River, was not analyzed as part of the AN-OVA because its statistical ‘‘group’’ representsa sample size of one. The captive manatees (n5 6) also were not analyzed in this ANOVA.The ANOVA results indicate significant dif-ferences in the four statistical populations,both for d13C (n 5 93, df 5 89, F 5 12.2, Fcritical

5 2.71, p K 0.001) and d18O (n 5 93, df 5 89;F 5 9.0, Fcritical 5 2.71, p K 0.001). The statis-tical differences in both d13C and d18O aretherefore interpreted to have paleobiologicalsignificance related to, respectively, diets andhabitat preferences.

Extant Sirenians: Wild Populations and CaptiveSpecimens of Trichechus manatus and Wild Du-gong dugon. Carbon isotopic values for Re-cent, wild manatees have a mean d13C of25.7‰ and broad range between 213.9‰and 0.5‰ (Table 4), indicating a mixed diet.The corresponding d18O mean is 29.1‰ witha range between 27.3‰ and 31.2‰, indicatinga mixture of freshwater to marine habitats.These data demonstrate that modern Triche-chus manatus from Florida fills a broad ecolog-ical niche ranging from marine with a sea-grass diet, to freshwater with a C3 diet (Figs.3, 4). Captive Trichechus marks an end-mem-ber, admittedly unnatural for a freshwater, C3

feeder (Fig. 3), although some specimens ap-proach marine d18O values owing to the prob-able enrichment of water in 18O from highevaporation rates in the shallow tanks.

For modern wild Australian dugongs, themean d13C of 1.2‰ and narrow range (20.6‰to 1.7‰) indicate a specialized seagrass diet(Table 4, Fig. 4), as is also empirically knownfrom studies of dugong diets (Walker 1975;Husar 1978a; Marsh et al. 1984; Neitschmann1984). Likewise, the mean d18O of 29.8‰ andnarrow range (29.6 to 30.1‰) suggest a pre-dominantly marine environment. These val-ues for water and diet can be assumed to rep-resent an end-member, given that dugongsgenerally are strictly marine and predomi-nantly eat seagrasses (Fig. 3).

The d13C and d18O values from tooth enamelcarbonate indicate that Recent dugongs andmanatees demonstrate a broad range of iso-topic variation that correlates with known di-ets and habitat preferences of these extant si-renians. Along with the conceptual model


TABLE 4. Univariate statistical data (n, mean, standard deviation, range) for different subsets of bulk sample stablecarbon and oxygen isotopic data (as discussed in the text) for the fossil and extant sirenians from Florida. SeeAppendix for raw data.

Group n d13C (‰) d18O (‰)

Eocene–early Oligocene ProtosirenAll Metaxytherium

M. crataegenseAgricola M. floridanumGainesville M. cf. floridanumLater Bone Valley M. floridanum

426

385

10

3.4, 1.0, 1.9 to 4.121.7, 4.1, 213.1 to 2.821.4, 1.5, 23.0 to 20.121.0, 1.9, 24.8 to 0.9

0.1, 1.0, 21.0 to 1.223.4, 6.1, 213.1 to 2.8

30.2, 1.6, 28.3 to 32.229.3, 1.6, 25.1 to 31.028.0, 2.2, 25.4 to 29.629.1, 2.3, 25.1 to 30.730.7, 0.3, 30.4 to 31.029.0, 0.5, 28.3 to 29.9

All Florida Protosirenidae and Dugongidae?Plio-Pleistocene Trichechus sp.

LeiseySanta Fe River sitesRock SpringsOklawaha River

31*45

325

512

20.9, 4.3, 213.1 to 5.627.7, 5.5, 218.2 to 1.726.2, 2.3, 27.7 to 23.529.9, 5.3, 218.2 to 1.725.9, 7.3, 214.3 to 0.124.4, 3.5, 211.4 to 20.3

29.2, 1.9, 23.0 to 32.227.7, 1.6, 24.7 to 32.127.8, 1.7, 26.5 to 29.727.3, 1.6, 24.7 to 32.129.1, 1.1, 28.1 to 30.427.7, 1.6, 25.8 to 30.4

Recent, wild Trichechus manatusAll Florida fossil and wild TrichechusCaptive Trichechus manatusWild Dugong dugon

1863

66

25.7, 5.1, 213.9 to 0.527.2, 5.4, 218.2 to 1.7

213.8, 0.9, 214.9 to 212.31.2, 0.9, 20.6 to 1.7

29.1, 0.9, 27.3 to 31.228.1, 1.6, 24.7 to 32.126.5, 1.4, 25.1 to 28.529.8, 0.2, 29.6 to 30.1

* Includes one specimen of late Miocene Corystosiren varguezi, UF 18826 (Appendix).

FIGURE 4. Plot of d13C versus d18O for all modern sirenians sampled in this study. All measurements were madefrom tooth enamel carbonate. Different ecologies grade between modeled end-members of ecological variation.Modern Dugong (white diamonds) is known to be a strictly marine, seagrass feeder, and captive Trichechus (blackdiamonds) are strictly freshwater, C3 feeders. Wild Trichechus (gray diamonds) is known to live in either habitat,i.e., ranging between the two end-members.

(Fig. 3), these data are used below as the ref-erence model of extant analogs to interpret thediets and habitat preferences of fossil sireni-ans from Florida. (These data are also plottedin the background of Figures 5–7 along withthose for fossil sirenians as a means of inter-preting the paleoecology of the extinctgroups.)

Eocene-Oligocene Protosiren sp. (ca. 40 to 35Ma). The primitive dugongid Protosiren isrelatively rare in the middle Cenozoic lime-stones of Florida. Only four individual toothspecimens were available for isotopic analy-ses. The three Eocene Protosiren species andone early Oligocene cf. Protosiren species havea combined mean d13C value of 3.4‰ with a


FIGURE 5. Plot of d13C against d18O for all teeth of Protosiren sampled in this study. Data from recent sirenians arealso plotted for comparison. All measurements were made from tooth enamel carbonate.

narrow observed range (Table 4, Fig. 4). Giventhe isotopic enrichment factor calculated forsirenians of 14.0‰, these data indicate thatFlorida Protosiren sp. fed on vegetation with amean isotopic value of about 211‰, suggest-ing that their diet consisted principally of sea-grasses. These results support previous obser-vations (Ivany et al. 1990) of a direct associa-tion with Thalassia-like seagrasses and Proto-siren sp. from the Dolime Quarry, middleEocene Avon Park Formation of northern pen-insular Florida (Fig. 2).

The mean d18O value of 30.2‰ (range 28.3–32.2‰) for these same four Protosiren speci-mens indicates an environmental water sourceenriched in 18O, an observation made all themore significant in light of the relatively de-pleted global ocean d18O interpreted for Eo-cene seawater (Zachos et al. 2001). In compar-ison with the data for recent sirenians, Proto-siren plots near the values for modern du-gongs (Fig. 5), suggesting that Protosiren livedand fed in environments similar to that ofmodern dugongs. The isotopic data indicatethese early sirenians were principally marine(also like extant dugongs) and confirm pre-vious hypotheses that early during their his-tory, dugongs specialized on seagrasses (e.g.,Domning 1981, 2001a; Ivany et al. 1990). Al-

though a specialized diet and habitat are in-dicated from the isotopic data, this interpre-tation may be an artifact of the small samplesize available for analyses. Well-preserved cra-nia of Florida Protosiren do not exist, but ifthey did, it is predicted that they would havea relatively well developed flexure consistentwith a seagrass diet (Domning 2001a), prob-ably similar to Protosiren fraasi from the mid-dle Eocene of Egypt (Fig. 1B).

Middle to Late Miocene Metaxytherium (Bar-stovian to ?early Hemphillian, ca. 16–9 Ma) andCorystosiren (early Hemphillian, ca. 8 Ma).Samples of Metaxytherium were analyzed fromfour different localities during this study (Ta-ble 4, Appendix). The mean carbon isotopicvalues and very small observed ranges forthree of these samples, i.e., Barstovian M. cra-taegense (mean d13C 5 21.4‰), early Claren-donian M. floridanum from the Bone ValleyAgricola mine (mean d13C 5 21.0‰), and lateClarendonian M. cf. floridanum from theGainesville creeks (mean d13C 5 0.1‰) indi-cate that these Metaxytherium were specializedfeeders with a diet predominantly consistingof seagrasses. Most plot very close to moderndugongs (Fig. 6). The carbon isotopic data forClarendonian/early Hemphillian M. floridan-um from the later Bone Valley sequence sug-


FIGURE 6. Plot of d13C against d18O for all teeth of Metaxytherium sampled in this study. Metaxytherium data areseparated according to locality and/or age of the fossils. Data from recent sirenians are also plotted for comparison.All measurements were made from tooth enamel carbonate.

gest a more diverse diet for this fourth suiteof samples. The mean d13C is more negative(mean d13C 5 23.4‰) than for the precedingsamples of Metaxytherium and the observedrange is very interesting. Seven of the speci-mens have d13C values close to 0‰ (Fig. 6), in-dicating a diet of seagrasses. This is consistentwith previous hypotheses about the diet ofMetaxytherium based on its dentition and highdegree of rostral deflection (e.g., Domning1988, 2001a); (Fig. 1C). However, the remain-ing three specimens, with d13C values of 210.9(JW F7502), 212.4 (JW F7407E), and 213.1‰(JW F7405A2) (Fig. 6, Appendix) indicate asignificantly different diet. Using the isotopicenrichment of 14.0‰ presented above, andtaking the mean for these three specimens(212.1‰), then the mean value of the ingest-ed plant foods would be 226.1‰, indicatinga diet consisting predominantly of C3 plants.From the isotopic results alone, and in the ab-sence of other corroborating evidence, it is notpossible to further identify what specifickinds of C3 plants these Metaxytherium indi-viduals ate when their tooth enamel mineral-ized.

The oxygen data for all four Metaxytherium

samples yield a mean d18O of 29.3‰ (Table 4).Relative to the extant Trichechus specimens an-alyzed here, these data indicate an isotopicallyenriched water source, suggesting a principal-ly marine habitat. The majority of the data, asindicated by the large grouping of individualpoints between approximately 28‰ and 31‰(Fig. 6), support this interpretation. However,three data points, i.e., 25.4‰ (UF 36446) for M.crataegense from the Barstovian Palmetto mine,and 25.1 and 25.8‰ (UF 206653, 206655) forM. floridanum from the early ClarendonianAgricola Fauna, are among the lowest d18Ovalues observed during this study and aresimilar to those for the captive manateesknown to live in full freshwater (Fig. 5).

Given the morphology of other fossil du-gongs, and known diet and habitat preferenc-es of extant Dugong dugon, it is perhaps notsurprising that for the most part, Metaxyther-ium from the Miocene of Florida was a spe-cialized seagrass feeder and lived in marinewaters. Exceptions to this general pattern in-clude (1) three specimens indicating a diet ofC3 plants; and (2) three other specimens livingin more freshwater habitats, although grazingpredominantly on seagrasses.


FIGURE 7. Plot of d13C versus d18O for all fossil teeth of Trichechus sampled in this study. Fossil Trichechus are sep-arated according to the locality from which the fossil was collected. Data from recent sirenians are also plotted forcomparison. All measurements were made from tooth enamel carbonate.

Corystosiren is a late-surviving dugong at atime when sirenian fossils are exceedinglyrare in Florida. A single specimen of C. var-guezi from the early Hemphillian WaccasassaRiver yielded a relatively enriched d13C valueof 5.6‰ and a very depleted d18O value of23.0‰ (Fig. 6 [lower right corner], Appendix).These data suggest that this dugong was feed-ing on seagrasses, but living in predominantlyfreshwater. If so, then this ecological niche isnot commonly found in other fossil or extantdugongs. It is obvious that a single data pointmay not be representative of the overall aut-ecology of this species. Unfortunately, morespecimens of the rare C. varguezi are not avail-able for additional isotopic analyses.

?Late Pliocene and Pleistocene Trichechus sp.The manatees (Family Trichechidae) are be-lieved to have originated in South Americaduring the middle Tertiary (Domning 1982),with the earliest fossil record of this sirenianfamily represented by Potamosiren magdalensis(Domning 1997b) from the late middle Mio-cene (ca. 10 Ma) of Colombia. A single speci-men (INGEOMINAS IGM 250927; isotopicsample BJMacF 96-70) of this early manateefrom the La Venta Fauna yielded a d13C valueof 213.3‰ (Fig. 7), indicating that this indi-

vidual was feeding not on seagrasses (as wassuggested because of its thick enamel), butrather on C3 vegetation. This same sampleyielded a d18O 5 26.3‰, suggesting a princi-pally freshwater habitat.

Representatives of the Family Trichechidaeapparently dispersed into Florida either dur-ing the late Pliocene or early Pleistocene. Thefirst definite, in situ occurrence of manatees,referred to here as Trichechus sp., which isprobably a species different from T. manatus(Domning 1982; Hulbert 2001), comes fromthe 1.5 Ma Irvingtonian Leisey Shell Pit (Fig.2). The mean d13C value of 26.2‰ for LeiseyTrichechus sp. indicates a mixed diet and themean d18O of 27.8‰ indicates mixed fresh-water and marine habitats (Table 4).

A large sample suite (n 5 25) comes fromseveral localities along the bed of the Santa FeRiver in northern Florida. Given the age spanof the associated mammalian fauna, these fos-sils almost certainly represent a temporallymixed assemblage. The age range might be asold as late Pliocene (middle Blancan), but itsurely spans much of the Pleistocene, includ-ing the late Blancan and Irvingtonian NAL-MAs. These samples may represent a mixingof genetically independent populations that


migrated into this region at different times(Domning 1982, 2001a). Some localities alongthe Santa Fe River have better temporal reso-lution than others. Santa Fe River localities aredivided for the purposes of plotting when amore precise age may be estimated, but all areconsidered together in the statistical analysis.The isotopic data have a mean d13C value of29.9‰, but the range is perhaps more inter-esting (Table 4, Fig. 7). At one end of the spec-trum, the minimum d13C value of 218.2‰ isexceedingly depleted and suggests an indi-vidual feeding predominantly on C3 plantsthat lived in closed-canopy communities (ap-proximately 232‰; [van der Merwe and Me-dina 1991]). At the other end of the spectrum,d13C values as enriched as 1.7‰ indicate in-dividuals feeding on seagrasses, a principalfood source similar to that of modern Triche-chus manatus from Florida.

Fossil manatees were analyzed from twoother late Pleistocene sites, Rock Springs andthe Oklawaha River. In contrast to the tem-poral and possible genetic mixing that char-acterize the Santa Fe River specimens, theseother sites seem relatively homogeneous, withRock Springs being about 125,000 years old(Wilkins 1983) and the Oklawaha being latestRancholabrean judging from its associatedfauna (MacFadden personal observation2001). The Rock Springs sample demonstratesa broad range of d13C values from 214.3‰ to0.1‰ that appears to represent a bimodal dis-tribution of values clustering at either extreme(Table 4, Fig. 7). This is interpreted as some in-dividuals feeding on C3 plants whereas otherswere feeding on seagrasses. The Oklawahasample likewise has a broad range of d13C val-ues, from 211.4 to 20.3‰, suggesting bothmixed feeding as well as some specializationon seagrass.

Taken together, the d18O data for fossil andextant wild Trichechus sp. from Florida indi-cates a considerable spread and continuousvariation from 24.7‰ to 32.1‰ (Table 4, Fig.7). These data are interpreted to indicate arange of habitats from full freshwater, pre-sumably peninsular rivers and springs, to fullmarine waters. This range of habitat prefer-ences is similar to that of extant Trichechusmanatus.

Temporal Variation and Evolution of Diet andHabitat. To understand temporal variationand patterns in the stable isotopic data for thesamples of fossil and extant Florida sirenianspresented in this paper, we analyzed themean and individual d13C and d18O data withrespect to time interval or zone. It should benoted that some of the time intervals or zonescontaining sirenian data are approximate andtheir exact ages as plotted represent intervalsin which ages are estimated by stage of evo-lution biochronology within a particularNALMA. As such, these age determinationsshould be considered approximate (to within6105 to 106 years for the pre-Pleistocene dataand 105 to 104 years for Pleistocene data). Also,there are two important intervals in which iso-topic samples were rare and consequently notavailable for this study (ca. 30 to 20 Ma) or itseems that extinct sirenians were exceedinglyrare in the Florida fossil record (ca. 5 to 2 Ma).

The tooth enamel carbon isotopic data forEocene and Oligocene (before 30 Ma on Fig. 8)Protosiren yield relatively enriched d13C valuesinterpreted to represent a specialized seagrassdiet. Likewise, most of the Metaxytheriumspecimens are relatively enriched in d13C, alsoindicating a specialized seagrass diet, consis-tent with the previously observed morpholog-ical adaptation of a high degree of rostral de-flection (e.g., Domning 1977, 2001b). Threespecimens of Metaxytherium that are relativelynegative in d13C indicate individuals feedingon a principally C3 diet. A single specimen ofCorystosiren with a d13C value of 5.6‰ is themost enriched of all values analyzed in thisstudy and likewise suggests a specialized sea-grass diet. The mean d13C values for fossil andextant wild Trichechus are more negative, andthe individual data points have a broaderrange of d13C values indicating a more diversediet relative to Protosiren, Metaxytherium, orextant Dugong.

The tooth enamel oxygen isotopic data forEocene and Oligocene (before 30 Ma on Fig. 9)Protosiren indicate relatively enriched d18O,which, given the estimated values of globalearly Cenozoic seawater (Zachos et al. 2001),indicates that Protosiren was living principallyin marine habitats. This also is the case for the


FIGURE 8. Plot of d13C versus time for the bulk samples of Florida sirenians presented in this paper. This includesmean d13C values (Table 4) for time horizons or intervals represented by large circles and individual d13C data pointspresented (Appendix). Note the change in timescale and intervals for which samples were not available for analysis.A single mean value for age and d13C has been calculated for all Protosiren analyses from the approximately 40 and35 Ma levels.

Miocene (20 to 5 Ma interval) as representedby the majority of the Metaxytherium speci-mens analyzed. On the other hand, three spec-imens of Metaxytherium (different from thethree outliers for the d13C data describedabove) and the one analysis for Corystosirenare relatively depleted in d18O. We interpretthese four data points to represent individualsliving in relatively freshwater environments(although it is possible that these could rep-resent an artifact of diagenesis). For the Pleis-

tocene, as represented by Trichechus, the meanvalues at about 1.5, 1.25, 0.25, 0.1, and 0.025Ma are slightly less positive than for the Eo-cene through Oligocene, but the variancearound the mean is perhaps more informativeand interesting. The broader spread of indi-vidual data points is interpreted as a diversi-fication of habitats ranging from full marine tofull freshwater (spread of approximately 8‰)for Trichechus relative to either Protosiren orMetaxytherium.


FIGURE 9. Plot of d18O versus time for the bulk samples of Florida sirenians presented in this paper. This includesmean d18O values (Table 4) for time horizons or intervals represented by large circles and individual d18O data pointspresented (Appendix). Note the change in time scale and intervals for which samples were not available for analysis.A single mean value for age and d18O has been calculated for all Protosiren analyses from the approximately 40 and35 Ma levels.

Concluding Remarks

Fossil discoveries and morphological inter-pretations over the past several decades havedone much to advance our understanding offossil sirenians, including those from the richCenozoic sequence in Florida. The diet of ex-tinct sirenians previously has been interpretedfrom morphological characters such as the de-gree of rostral deflection (e.g., Domning2001a). The habitat preferences of extinct si-renians have been interpreted from associatedfossils such as Eocene seagrasses from central

Florida (Ivany et al. 1990) and the presence ofshallow marine or estuarine faunas. Stable iso-topic analyses of tooth enamel add anotherline of evidence that allows further testing ofthese paleoecological hypotheses.

The isotopic data presented here (Table 4)for the Eocene to late Miocene Protosiren anddugongs (i.e., extinct species of the Family Du-gongidae; Table 1) from Florida differ signifi-cantly from those of fossil and wild Trichechusfor both d13C (T-statistic 5 5.7, T-critical 5 1.7,p K 0.001) and d18O (T-statistic 5 2.8, T-crit-


ical 5 1.7, p 5 0.006). These isotopic data areinterpreted to represent differences in the eco-logical adaptations of Protosiren and extinctFlorida dugongs relative to extinct and extantmanatees. As a general pattern, Protosiren andthe extinct Florida dugongs had a more spe-cialized diet of seagrass and a predominantlymarine habitat. In contrast, fossil manateesand modern Trichechus manatus in Florida havebeen more generalized feeders, with a broaderisotopic range representing diets of C3 plantsto seagrasses. In general, the isotopic data re-ported here confirmed previous hypothesesbased on morphological and associated faunalevidence. There were, however, a few surpris-es; e.g., Metaxytherium crataegense fed on sea-grass despite a low degree of rostral deflec-tion, and three specimens of M. floridanumprincipally fed on C3 plants.

The results presented here indicate that Pro-tosiren and extinct dugongs from Florida wererelatively conservative in their adaptations,maintaining diet and habitat preferences sim-ilar to those of modern Dugong dugon. In con-trast, Trichechus has been considerably moregeneralized both in diet and habitat prefer-ence since it first appeared in Florida about 2Ma. Both dugongs and manatees have filledthe ‘‘aquatic megaherbivore niche’’ (Domning2001a) or paleoguild (sensu van Valkenburgh1995). It therefore has been interesting to spec-ulate whether these two sirenian groups com-peted, or whether the manatees filled an‘‘empty’’ niche created by the extinction of thelate Miocene dugongs. Although the fossils ofsirenians in Florida are abundant, the criticaltime interval, i.e., late Miocene to Pliocene (ca.10 to 3 Ma) is poorly represented and there-fore does not allow testing of the competitionversus replacement hypotheses for theseaquatic megaherbivores. We suspect, however,that this niche was vacated by dugongs andthen filled several million years later by man-atees. Our reasons for this relate to the factthat Hemphillian marine/terrestrial mam-malian faunas are very well represented in theFlorida sequence, including those of the Up-per Bone Valley (e.g., Palmetto Fauna [Morgan1994]). These faunas contain both diagnosticHemphillian land mammals and a diversemarine mammal fauna (Morgan 1994) but are

conspicuous in their paucity of sirenians. Thisevidence suggests that other than a few rareoccurrences (Corystosiren varguezi and unde-scribed dugongids, sensu Domning 2001a andHulbert 2001), dugongids had essentially be-come extinct in Florida by about 5 Ma (i.e., theage of the Upper Bone Valley Formation).

Despite the rich fossil record of sirenians inFlorida, it also is unfortunately inadequateduring other critical time intervals. The max-imum diversity of dugongs in Florida oc-curred during the late Oligocene and earlyMiocene with three coexisting taxa, Metaxy-therium sp., Crenatosiren olseni, and Dioplother-ium manigaulti, as represented at localitiessuch as White Springs in northern Florida(Domning 1989a). Although all three speciesare considered to have fed principally on sea-grasses, judging from degree of rostral deflec-tion, tusk morphology, and estimated bodysize, Domning (2001a) interprets some nichedifferentiation for Metaxytherium sp., C. olseni,and D. manigaulti. With regard to diet, thesespecializations pertain to the size of the sea-grass rhizome upon which each dugong spe-cies would have fed. If specimens were avail-able for these extinct dugongs, stable carbonisotopes could confirm that they fed upon sea-grasses but would not be able to further re-solve the hypotheses about specific speciali-zation on different-sized rhizomes.

After dugongids became rare in the lateMiocene, there is a roughly 3-Myr gap (ca. 5to 2 Ma) in which sirenians are virtually ab-sent in Florida, despite the presence of appro-priate-aged (Blancan) faunas containingaquatic elements. The available fossil evidenceindicates that primitive trichechids originatedin the New World, with fossil occurrences ofPotamosiren magdalensis from the late MioceneLa Venta Fauna of Colombia and Rhibodonfrom the Pliocene of Argentina and NorthCarolina (Domning 1982, 1997b). By the timethat Trichechus first appears in the Florida se-quence by the early Pleistocene, it is similar toT. manatus, although Domning (1982) consid-ers the fossil manatee a different, heretoforeundescribed species.

The stable isotopic analyses were successfulin reconstructing the paleobiology of Floridasirenians. As a modern baseline, studies of


captive Trichechus manatus were important inestablishing a carbon isotopic enrichment val-ue («*) of 14.0‰, essentially the same calcu-lated for medium to large terrestrial mam-malian herbivores (Cerling and Harris 1999).Likewise, the extant sample of Australian Du-gong dugon formed a baseline for comparisonwith extinct Florida dugongs. Carbon isotopicanalyses were useful in interpreting the an-cient diets of extinct sirenians, as describedabove. In addition, although there is a com-plex isotopic source, which is dependent uponseveral environmental and physiological fac-tors, the resulting d18O analyzed in toothenamel can be used to discriminate habitatpreferences. For Florida sirenians, d18O valuesrange from relatively freshwater (depletedd18O), representing inland rivers and springs,to full marine (enriched d18O), representingshallow, coastal habitats.

Although fossils provide unparalleled cluesto ancient life, the fossil record is far fromcomplete, and new discoveries can always ad-vance our understanding of any group. Suchis the case with fossil sirenians from Florida.Additional specimens of the late Oligocene–early Miocene diversity, better knowledge ofthe rare, late-surviving Mio-Pliocene du-gongs, and discovery of in situ Pliocene tri-chechids would all go a long way toward ad-vancing our understanding of the phylogenet-ic history and paleobiogeography of this in-teresting group. In addition, the application ofstable isotopic analyses of tooth enamel car-bonate could be used in conjunction withthese future discoveries to further refine ourunderstanding of the diets and habitat pref-erences of the extinct Sirenia of Florida.

Acknowledgments

Teeth from extant Trichechus manatus, eithernaturally shed or in existing collections, wereanalyzed under the permission of U.S. Fishand Wildlife permit MA033974-0 to the Flor-ida Museum of Natural History (B. J. Mac-Fadden, permit director). We thank M. Farrisfor her assistance with this permit. D. Kwan ofJames Cook University, Townsville, Australia,kindly provided specimens of modern du-gong. A. Ames of the University of South Flor-ida, Tampa, provided us with unpublished

data on the food eaten by Hugh and Buffett.D. Colbert of the Mote Marine Laboratory, Sar-asota, provided samples of naturally shedteeth and food of Hugh and Buffett. S. C.White and C. Audette of the South FloridaMuseum, Bradenton, gave us naturally shedteeth and food of Snooty. Most of the fossilspecimens analyzed here are from the Uni-versity of Florida, Florida Museum of NaturalHistory Vertebrate Paleontology collection. Inaddition, we thank J. Waldrop of Lake Walesand R. Madden, Duke University, for otherfossil sirenian specimens analyzed during thisstudy. We have benefited greatly from the ad-vice, consultations, and assistance of C. A.Beck, U.S. Geological Survey Sirenian Project,Gainesville; T. E. Cerling, C. Cook, and B. Pas-sey, University of Utah; J. Curtis, University ofFlorida; D. P. Domning, Howard University; P.Koch, University of California-Santa Cruz; C.McCaffrey and L. Wilkins, Florida Museum ofNatural History Mammal Collection; and B.Beatty, R. C. Hulbert, and J. O’Sullivan, Flor-ida Museum of Natural History Vertebrate Pa-leontology Collection. Isotope samples wereprepared in the laboratory of T. Cerling (Uni-versity of Utah), D. Dilcher (University of Flor-ida), and P. Koch (University of California-Santa Cruz) and analyzed in the University ofFlorida Department of Geological SciencesStable Isotope Laboratory; SIRFER laboratoryin the Department of Biology, University ofUtah; or Earth Sciences, University of Califor-nia-Santa Cruz. The manuscript was im-proved thanks to the comments from the tworeviewers. This research was partially sup-ported by funds provided from National Sci-ence Foundation grant EAR 0087742 and Geo-logical Society of America grant 1998. This isUniversity of Florida Contribution to Paleo-biology number 529.

Literature Cited

Ambrose, S. 1998. Implications of 24 controlled diet experi-ments for diet reconstruction with carbon isotopes of bonecollagen and carbonate. Journal of Vertebrate Paleontology,Abstracts of Papers 18:24A.

Ames, A. L., E. S. Van Vleet, and W. M. Sackett. 1996. The useof stable carbon isotope analysis for determining the dietaryhabits of the Florida manatee, Trichechus manatus latirostris.Marine Mammal Science 12:555–563.

Andersen, S. H., and E. Nielsen. 1983. Exchange of water be-


tween the harbor porpoise, Phocoena phocoena, and the envi-ronment. Experientia 39:52–53.

Billups, K., and D. P. Schrag. 2002. Paleotemperatures and icevolume of the past 27 Myr revisited with paired Mg/Ca and18O/16O measurements on benthic foraminifera. Paleocean-ography 17:1–11.

Bocherens, H., P. L. Koch, A. Mariotti, D. Geraads, and J.-J. Jae-ger. 1996. Isotope biogeochemistry (13C, 18O) of mammalianenamel from African Pleistocene hominid sites. Palaios 11:306–318.

Boutton, T. W. 1991. Stable carbon isotope ratios of natural ma-terials. II. Atmospheric, terrestrial, marine, and freshwaterenvironments. Pp. 173–195 in D. C. Coleman and B. Fry, eds.Carbon isotope techniques. Academic Press, San Diego.

Bryant, J. D. 1991. New early Barstovian (middle Miocene) ver-tebrates from the upper Torreya Formation, eastern Floridapanhandle. Journal of Vertebrate Paleontology 11:472–489.

Bryant, J. D., and P. N. Froelich. 1995. A model of oxygen isotopefractionation in body water of large mammals. Geochimica etCosmochimica Acta 59:4523–4537.

Bryant, J. D., P. N. Froelich, W. J. Showers, and B. J. Genna. 1996.A tale of two quarries: biological and taphonomic signaturesin the oxygen isotopic composition of tooth enamel phos-phate from modern and Miocene equids. Palaios 11:397–408.

Cerling, T. E., and J. M. Harris. 1999. Carbon isotope fraction-ation between diet and bioapatite in ungulate mammals andimplications for ecological and paleoecological studies. Oec-ologia 120:347–363.

Cerling, T. E., and Z. Sharp. 1997. Stable carbon and oxygen iso-tope analysis of fossil tooth enamel using laser ablation. Pa-laeogeography, Palaeoclimatology, Palaeoecology 126:173–186.

Clementz, M., and P. Koch. 2001. Differentiating aquatic mam-mal habitat and foraging ecology with stable isotopes in toothenamel. Oecologia 129:461–472.

Coplen, T. B. 1994. Reporting of stable hydrogen, carbon, andoxygen isotopic abundances. Pure and Applied Chemistry 66:273–276.

Coplen, T. B., and C. Kendall. 2000. Stable hydrogen and oxygenisotope ratios for selected sites of the U.S. Geological Survey’sNAS-QAN and benchmark surface-water networks. Open-fileReport 00–160. U.S. Geological Survey, Reston, Va.

Dienes, P. 1980. The isotopic composition of reduced organiccarbon. Pp. 329–406 in P. Fritz and J. C. Fontes, eds. Handbookof environmental isotope geochemistry. 1. The terrestrial en-vironment. Elsevier, Amsterdam.

Domning, D. P. 1977. An ecological model for late Tertiary si-renian evolution in the North Pacific Ocean. Systematic Zo-ology 25:352–362.

———. 1981. Sea cows and sea grasses. Paleobiology 7:417–420.———. 1982. Evolution of manatees: a speculative history. Jour-

nal of Paleontology 56:599–619.———. 1988. Fossil Sirenia of the West Atlantic and Caribbean

Region. I. Metaxytherium floridanum. Journal of Vertebrate Pa-leontology 8:395–426.

———. 1989a. Fossil sirenians from the Suwannee River, Floridaand Georgia. Pp. 54–60 in G. S. Morgan, ed. Miocene pale-ontology and stratigraphy of the Suwannee River basin ofnorth Florida and south Georgia. Guidebook 30, SoutheasternGeological Society, Tallahassee.

———. 1989b. Fossil Sirenia of the West Atlantic and CaribbeanRegion. II. Dioplotherium manigaulti Cope, 1883. Journal of Ver-tebrate Paleontology 9:415–428.

———. 1990. Fossil Sirenia of the West Atlantic and CaribbeanRegion. IV. Corystosiren varguezi, gen. et sp. nov. Journal ofVertebrate Paleontology 10:361–371.

———. 1994. A phylogenetic analysis of the Sirenia. In A. Bertaand T. A. Demere, eds. Contributions in marine mammal pa-

leontology honoring Frank C. Whitmore, Jr. Proceedings ofthe San Diego Society of Natural History 29:177–189.

———. 1997a. Sirenia. Pp. 383–391 in R. F. Kay et al., eds. Ver-tebrate paleontology in the Neotropics: the Miocene Fauna ofLa Venta, Colombia. Smithsonian Institution Press, Washing-ton, D.C.

———. 1997b. Fossil Sirenia of the West Atlantic and CaribbeanRegion. VI. Crenatosiren olseni (Reinhart, 1976). Journal of Ver-tebrate Paleontology 17:397–412.

———. 1999. Fossils explained 24: Sirenians (seacows). GeologyToday 15:75–79.

———. 2001a. Evolution of the Sirenia and Desmostylia. Pp.151–168 in J.-M. Mazin and V. de Buffrenil, eds. Secondaryadaptation of tetrapods to life in the water: proceedings of theinternational meeting, Poitiers, 1996. Verlag Dr. FriedrichPfeil, Munich.

———. 2001b. Sirenians, seagrasses, and Cenozoic ecologicalchange in the Caribbean. Palaeogeography, Palaeoclimatolo-gy, Palaeoecology 166:27–50.

———. 2001c. The earliest known fully quadrupedal sirenian.Nature 413:625–627.

Domning, D. P., and L. C. Hayek. 1984. Horizontal tooth re-placement in the Amazonian manatee (Trichechus inunguis).Mammalia 48:105–127.

Domning, D. P., G. S. Morgan, and C. E. Ray. 1982. North Amer-ican Eocene sea cows (Mammalia: Sirenia). Smithsonian Con-tributions to Paleobiology 52:1–69.

Ehleringer, J. R., R. F. Sage, L. B. Flanagan, and R. W. Pearcy.1991. Climate change and the evolution of C4 photosynthesis.Trends in Ecology and Evolution 6:95–99.

Farquhar, G. D., J. R. Ehleringer, and K. T. Hubrick. 1989. Carbonisotope discrimination and photosynthesis. Annual Review ofPlant Physiology and Plant Molecular Biology 40:503–537.

Gremillion, P. T. 1994. Separation of streamflow components inthe Econlockhatchee River System using environmental stableisotope tracers. Ph.D. dissertation. University of Central Flor-ida, Orlando.

Hemminga, M. A., and M. A. Mateo. 1996. Stable carbon iso-topes in seagrasses: variability in ratios and use in stable iso-topes. Marine Ecology Progress Series 140:285–298.

Hobson K. A., J. F. Piatt, and J. Pitocchelli. 1994. Using stableisotopes to determine seabird trophic relationships. Journal ofAnimal Ecology 63:786–798.

Hoefs, J. 1997. Stable isotope geochemistry. Springer, Berlin.Hui, C. A. 1981. Seawater consumption and water flux in the

common dolphin Delphinus delphis. Physiological Zoology 54:430–440.

Hulbert, R. C. 1988. Cormohipparion and Hipparion (Mammalia,Perissodactyla, Equidae) from the late Neogene of Florida.Bulletin of the Florida State Museum (Biological Sciences) 33:229–338.

———, ed. 2001. The fossil vertebrates of Florida. UniversityPress of Florida, Gainesville.

Husar, S. L. 1978a. Dugong dugon. Mammalian Species 88:1–7.———. 1978b. Trichechus manatus . Mammalian Species 93:1–5.Ivany, L. C., R. W. Portell, and D. S. Jones. 1990. Animal-plant

relationships and paleobiogeography of an Eocene seagrasscommunity from Florida. Palaios 5:244–258.

Keeley, J. E., and D. R. Sandquist. 1992. Carbon: freshwaterplants. Plant, Cell and Environment 15:1021–1035.

Koch, P. L. 1998. Isotopic reconstruction of past continental en-vironments. Annual Review of Earth and Planetary Sciences26:573–613.

Koch, P. L., J. C. Zachos, and P. D. Gingerich. 1992. Correlationbetween isotope records in marine and continental carbonreservoirs near the Palaeocene/Eocene boundary. Nature 358:319–322.

Koch, P. L., N. Tuross, and M. L. Fogel. 1997. The effects of sam-


ple treatment and diagenesis on the isotopic integrity of car-bon in biogenic hydroxylapatite. Journal of ArchaeologicalScience 24:417–429.

Kohn, M. J. 1996. Predicting animal d18O: accounting for dietand physiological adaptation. Geochimica et CosmochimicaActa 60:4811–4829.

Langeland, K. A. 1990. Hydrilla: a continuing problem in Floridawaters. Circular No. 884. Cooperative Extension Service/In-stitute of Food and Agricultural Sciences, University of Flor-ida, Gainesville.

Lear, C. H., H. Elderfield, and P. A. Wilson. 2000. Cenozoicdeep-sea temperatures and global ice volumes from Mg/Cain benthic foraminiferal calcite. Science 287:269–272.

MacFadden, B. J., and T. E. Cerling. 1996. Mammalian herbivorecommunities, ancient feeding ecology, and carbon isotopes: a10 million-year sequence from the Neogene of Florida. Journalof Vertebrate Paleontology 16:103–115.

MacFadden, B. J., T. E. Cerling, and J. Prado. 1996. Cenozoic ter-restrial ecosystem evolution in Argentina: evidence from car-bon isotopes of fossil mammal teeth. Palaios 11:319–327.

MacFadden, B. J., T. E. Cerling, J. M. Harris, and J. Prado. 1999.Ancient latitudinal gradients of C3/ C4 grasses interpretedfrom stable isotopes of New World Pleistocene horse (Equus)teeth. Global Ecology and Biogeography 8:137–149.

Marsh, H. 1986. The status of the dugong in Torres Strait. Pp.53–76 in A. K. Haines, G. C. Williams, and D. Coates, eds. Tor-res Straits fisheries seminar, Port Moresby. Australian Gov-ernment Publishing Service, Canberra.

Marsh, H., and W. K. Saalfeld. 1991. The status of the dugongin Torres Strait. In D. Lawrence and T. Cansfield-Smith, eds.Sustainable development of traditional inhabitants of the Tor-res Strait region. GBRMPA Workshop Series 10:187–194.

Marsh, H., G. E. Heinsohn, and L. M. Marsh. 1984. Breeding cy-cle, life history and population dynamics of the dugong, Du-gong dugon (Sirenia: Dugongidae). Australian Journal of Zo-ology 32:767–788.

McCrea, J. M. 1950. On the isotopic chemistry of carbonates anda paleotemperature scale. Journal of Chemical Physics 18:849–857.

McKenna, M. C., and S. K. Bell. 1997. Classification of mammalsabove the species level. Columbia University Press, New York.

Meyers, J., P. K. Swart, and J. Meyers. 1993. Geochemical evi-dence for groundwater behavior in an unconfined aquifer,South Florida. Journal of Hydrology 148:249–272.

Morgan, G. S. 1994. Miocene and Pliocene marine mammal fau-nas from the Bone Valley Formation of central Florida. In A.Berta and T. A. Demere, eds. Contributions in marine mam-mal paleontology honoring Frank C. Whitmore, Jr. Proceed-ings of the San Diego Society of Natural History 29:239–268.

Morgan, G. S., and R. C. Hulbert. 1995. Overview of the geologyand vertebrate biochronology of the Leisey Shell Pit LocalFauna, Hillsborough County, Florida. Bulletin of the FloridaMuseum of Natural History 37:1–92.

Nietschmann, B. 1984. Hunting and ecology of dugongs andgreen turtles, Torres Strait, Australia. National GeographicSociety Research Report 17:625–651.

Ortner, P. B., T. N. Lee, P. J. Milne, R. G. Zidka, M. E. Clarke, G.P. Podesta, P. K. Swart, P. A. Testa, L. P. Atkinson, and W. R.Johnson. 1995. Mississippi River flood waters reached theGulf Stream. Geophysical Research Letters 100:13,595–13,601.

Reinhart, R. H. 1976. Fossil sirenians and desmostylids fromFlorida and elsewhere. Bulletin of the Florida State Museum(Biological Sciences) 20:187–300.

Roe, L. J., J. G. M. Thewissen, J. Quade, J. R. O’Neil, S. Bajpai, A.Sahni, and S. T. Hussain. 1998. Isotopic approaches to under-standing the terrestrial-to-marine transition of the earliestwhales. Pp. 399–422 in J. G. M. Thewissen, ed. The emergenceof whales. Plenum, New York.

Savage, R. J. G., D. P. Domning, and J. G. M. Thewissen. 1994.Fossil Sirenia of the west Atlantic and Caribbean region. V.The most primitive known sirenian, Prorastomus sirenoidesOwen, 1855. Journal of Vertebrate Paleontology 14:427–449.

Schoeninger, M. J., and M. J. DeNiro. 1982. Carbon isotope ratiosof apatite from fossil bone cannot be used to reconstruct dietsof animals. Nature 297:577–578.

Simenstad, C. A., D. O. Duggins, and P. D. Quay. 1993. Highturnover of inorganic carbon in kelp habitats as a cause of d13Cvariability in marine food webs. Marine Biology 116:147–160.

Simpson, G. G. 1932. Fossil Sirenia of Florida and the evolutionof the Sirenia. Bulletin of the American Museum of NaturalHistory 59:419–503.

Swart, P. K., L. Sternberg, R. Steinen, and S. A. Harrison. 1989.Controls on the oxygen and hydrogen isotopic compositionof waters from Florida Bay. Chemical Geology 79:113–123.

Swart, P. K., R. E. Dodge, and H. J. Hudson. 1996. A 240-yearstable oxygen and carbon isotope record in a coral from SouthFlorida: implications for the prediction of precipitation insouthern Florida. Palaios 11:362–375.

Tedford, R. H., M. F. Skinner, R. W. Fields, J. M. Rensberger, D.P. Whistler, T. Galusha, B. E. Taylor, J. R. Macdonald, and S.D. Webb. 1987. Faunal succession and biochronology of theArikareean through Hemphillian interval (late Oligocenethrough earliest Pliocene epochs) in North America. Pp. 153–210 in M. O. Woodburne, ed. Cenozoic mammals of NorthAmerica: geochronology and biostratigraphy. University ofCalifornia Press, Berkeley.

van der Merwe, N. J., and E. Medina. 1991. The canopy effect,carbon isotope ratios and foodwebs in Amazonia. Journal ofArchaeological Science 18:249–259.

van Valkenburgh, B. 1995. Tracking ecology over geologicaltime: evolution within guilds of vertebrates. Trends in Ecol-ogy and Evolution 10:71–75.

Walker, E. P. 1975. Mammals of the world, 3d ed. Johns HopkinsUniversity Press, Baltimore.

Wilkins, K. T. 1983. Pleistocene mammals from the Rock SpringsLocal Fauna, central Florida. Brimleyana 9:69–82.

Yoshida, N., and N. Miyazaki. 1991. Oxygen isotope correlationof cetacean bone phosphate with environmental water. Jour-nal of Geophysical Research 96(C1):815–820.

Zachos, J., M. Pagani, L. Sloan, E. Thomas, and K. Billups. 2001.Trends, rhythms, and aberrations in global climate 65 Ma topresent. Science 292:686–693.


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chee

kto

oth

chee

kto

oth

Ok

law

aha

Riv

er1

Ok

law

aha

Riv

er1

Ok

law

aha

Riv

er1

Ok

law

aha

Riv

er1

Ok

law

aha

Riv

er1

25.

52

8.4

24.

42

3.5

20.

7

27.4

27.5

30.2

28.8

30.4

UF

un

cata

log

edU

Fu

nca

talo

ged

UF

un

cata

log

edU

Fu

nca

talo

ged

UF

un

cata

log

ed

Tric

hech

us

sp.

Tric

hech

us

sp.

Tric

hech

us

sp.

Tric

hech

us

sp.

Tric

hech

us

sp.

chee

kto

oth

chee

kto

oth

chee

kto

oth

chee

kto

oth

chee

kto

oth

Ok

law

aha

Riv

er1

Ok

law

aha

Riv

er1

Ok

law

aha

Riv

er1

Ok

law

aha

Riv

er1

Ok

law

aha

Riv

er1

23.

32

0.3

20.

62

0.7

26.

7

27.8

28.1

26.0

28.0

25.8

UF

un

cata

log

edU

Fu

nca

talo

ged

Tric

hech

us

sp.

Tric

hech

us

sp.

chee

kto

oth

chee

kto

oth

Ok

law

aha

Riv

er1

Ok

law

aha

Riv

er1

26.

92

11.4

29.5

26.9

Rec

ent

(ost

eolo

gica

lan

dn

atu

rall

ysh

edfr

omca

pive

indi

vidu

als)

,0M

aU

FM

1511

0U

FM

1511

3U

FM

1511

4U

FM

1511

5U

FM

1512

0

Tric

hech

us

man

atu

sTr

iche

chu

sm

anat

us

Tric

hech

us

man

atu

sTr

iche

chu

sm

anat

us

Tric

hech

us

man

atu

s

chee

kto

oth

chee

kto

oth

chee

kto

oth

chee

kto

oth

chee

kto

oth

Bre

vard

Cou

nty

St.

Joh

n’s

Riv

erB

reva

rdC

oun

tyD

uva

lC

oun

tyD

uva

lC

oun

ty

23.

62

0.9

20.

12

1.2

20.

7

29.4

31.2

30.4

29.4

29.7

UF

M15

122

UF

M15

141

UF

M15

160

UF

M15

172

UF

M15

173

Tric

hech

us

man

atu

sTr

iche

chu

sm

anat

us

Tric

hech

us

man

atu

sTr

iche

chu

sm

anat

us

Tric

hech

us

man

atu

s

chee

kto

oth

chee

kto

oth

chee

kto

oth

chee

kto

oth

chee

kto

oth

Vol

usi

aC

oun

tyB

reva

rdC

oun

tyL

eeC

oun

tyD

ade

Cou

nty

Dad

eC

oun

ty

211

.02

3.7

211

.0 0.0

25.

9

27.3

28.9

29.1

29.7

29.4

UF

M15

176

UF

M15

195

UF

M15

196

UF

M15

134

Tric

hech

us

man

atu

sTr

iche

chu

sm

anat

us

Tric

hech

us

man

atu

sTr

iche

chu

sm

anat

us

chee

kto

oth

chee

kto

oth

chee

kto

oth

chee

kto

oth

Dad

eC

oun

tyB

row

ard

Cou

nty

Dad

eC

oun

tyC

olli

erC

oun

ty

213

.92

11.9 0.5

29.

9

28.4

28.5

29.5

29.4

UF

M19

135

UF

M20

602

UF

M20

773

UF

M23

993

Tric

hech

us

man

atu

sTr

iche

chu

sm

anat

us

Tric

hech

us

man

atu

sTr

iche

chu

sm

anat

us

chee

kto

oth

chee

kto

oth

chee

kto

oth

chee

kto

oth

Lee

Cou

nty

Bre

vard

Cou

nty

Lak

eC

oun

tyL

ake

Cou

nty

24.

22

2.3

211

.02

12.6

29.4

28.7

28.0

27.9

Hu

ghor

Bu

ffet

tH

ugh

orB

uff

ett

Hu

ghor

Bu

ffet

tH

ugh

orB

uff

ett

Hu

ghor

Bu

ffet

tSn

ooty

Tric

hech

us

man

atu

sTr

iche

chu

sm

anat

us

Tric

hech

us

man

atu

sTr

iche

chu

sm

anat

us

Tric

hech

us

man

atu

sTr

iche

chu

sm

anat

us

Uch

eek

toot

hl

chee

kto

oth

lch

eek

toot

hl

chee

kto

oth

chee

kto

oth

Uch

eek

toot

h

Cap

tive

Cap

tive

Cap

tive

Cap

tive

Cap

tive

Cap

tive

212

.32

14.9

213

.82

14.1

213

.22

14.5

28.5

25.3

25.1

25.5

27.6

27.0

MD

-142

MD

-19

MD

-146

MD

-16

MD

-22

Du

gon

gdu

gon

Du

gon

gdu

gon

Du

gon

gdu

gon

Du

gon

gdu

gon

Du

gon

gdu

gon

tusk

tusk

tusk

tusk

tusk

Au

stra

lia

Au

stra

lia

Au

stra

lia

Au

stra

lia

Au

stra

lia

1.3

20.

61.

71.

61.

5

29.6

29.8

29.9

30.1

29.6

MD

-116

Du

gon

gdu

gon

tusk

Au

stra

lia

1.7

29.8

diets, habitat preferences, and niche differentiation of ... · florida cenozoic sirenians 299...

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