Introduction

ABEL (1916) was the first to show a strong corres-pondence and interaction between the environmentand the newly evolving shapes, morphologies and struc-tures of cephalopods. That seminal paper on thepalaeobiology of cephalopods underlined that cephalo-pod evolution is typically closely related with changingenvironmental conditions in the sea. It is evident todaythat the different fields treated by cephalopod workerslike evolution, biodiversity, ecology and palaeobiologyare blending into one another. Evolution moulds thegenetic programming of cephalopods and, in doing so,also moulds the potential for adaptation (YOUNG et al.1998; YACOBUCCI 1999). Adaptation is the major mo-tor for evolution, a situation recognized by ABEL (1916)when he erected the new field known as palaeobiology.Palaeobiology shows how important the animal-envi-ronment interaction is for promoting evolution.

Do ammonoids speciate profusely because internalfactors enhance variability and reproductive success?Or do ammonoids respond passively to environmentalchanges and therefore react after changes of the envi-ronment? These questions go beyond the scope of thispaper, but the problems associated with these major is-sues in cephalopod research can be highlighted by di-verse papers expressing different points of views. Theadoption of new habits interacts with long-lasting mor-

phological change and therefore appears as a new evo-lutionary trend. Radial or linear evolutions are themain evolutionary directions and pathways, but are on-ly descriptive mirrors for more important processes thatmore cephalopod workers should recognize (see HOUSE& SENIOR 1980). Spectacular evolutionary radiationand steps forward mostly took place when the environ-ment changed drastically. The present paper examinesthe problem of ammonoid evolution from a palaeobio-logical point of view, using two cephalopod case studiesfrom the Early Cretaceous of Upper Austria. Theseshow striking evidence for the evolution of new formsdue to environmental changes or due to adaption ofhabit to the preferred habitat. The adaptive strategy isclearly proven by the change of morphology in the fos-sil record and the embedding fauna.

Case study 1 shows the Early Cretaceous mass-occur-rence (KB1 A = Klausrieglerbach 1, section A, TernbergNappe, of the Northern Calcareous Alps - NCA; UpperAustria) with dominating Olcostephanus (Olcostephanus)guebhardi KILIAN morph. querolensis BULOT, from theSaynoceras verrucosum Zone (Late Valanginian)(LUKENEDER 2004; LUKENEDER & HARZHAUSER 2003).

Case study 2 shows an Early Cretaceous mass-occur-rence of ammonoids in the Ternberg Nappe of the NCA(Upper Austria), which is described for the first time.The mass-occurrence (section KB1 B = Klausrieglerbach

Cephalopod evolution: A new perspective –Implications from two Early Cretaceous ammonoid

suborders (Northern Calcareous Alps, Upper Austria)

A . L U K E N E D E R

Abstract: The status of two Early Cretaceous ammonoid groups from Upper Austria (Northern Calcareous Alps) is examined withrespect to the evolution of their shape as well as to their morphology and environmental preference. The Valanginian Olcoste-phanus guebhardi (Verrucosum Zone, 137 mya) shows the evolutionary separation of sex in two different environments and hasadapted its shape to the somewhat different environmental conditions. The heteromorph Barremian ammonoid Karsteniceras tern-bergense (Coronites Zone, 124 mya) is shown to have evolved during times with intermittent oxygen-depleted conditions associa-ted with stable, salinity-stratified water masses. Based on lithological and geochemical analysis combined with investigations oftrace fossils, microfossils and macrofossils, an invasion of an opportunistic (r-strategist) Karsteniceras biocoenosis during unfavou-rable conditions is assumed. Both examples are chosen to demonstrate evolutionary trends in the Early Cretaceous which can beobserved in the cephalopod group as a whole.

Key words: Evolution, ammonoids, palaeobiology, Northern Calcareous Alps, Early Cretaceous.

Denisia 20,zugleich Kataloge deroberösterreichischen

LandesmuseenNeue Serie 66 (2007):

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1, section B) dominated by Karsteniceras ternbergenseLUKENEDER is of Early Barremian age (Coronite darsiZone) (LUKENEDER 2003; LUKENEDER & TANABE 2002).

The main aim of this contribution is to show thesignificant effect of synecological stress, caused either byenvironmental changes of abiotic factors such as oxygencontent, salinity and depth, or by autecological stress as-sociated with biotic competitors occupying the same en-vironment.

Material and methods

Section KB1 A. The olcostephanid-dominated ma-terial originates from section KB1 A in the LosensteinSyncline. Ammonoids represent almost the totality ofthe macrofauna (98 per cent). The very abundant butgenerally poorly preserved Late Valanginian assemblagesconsist of 9 genera. About 200 specimens of Ol-costephanus guebhardi (BULOT) between 10 and 102 mmin maximum diameter were investigated. Many of thespecimens are fragmented. Two groups of varying maxi-mum size and different apertures are distinguishable. Thesmaller group represents the microconchs (up to 42mm), whereas the larger specimens are macroconchs (upto 102 mm). Due to the large number of specimens, ex-traordinarily well-preserved specimens (e.g. lappets ofmicroconchs) could be collected. Their casts (sculpturemoulds), with perfectly preserved sculpture, are usuallycompressed. No suture lines are visible on the steinkerns.

Section KB1 B. About 300 specimens ofKarsteniceras ternbergense LUKENEDER between 5 and 37mm in diameter were investigated from the KB1 B sec-tion. Most of the specimens are observable on one sideonly; most are entire and show no fragmentation. Juve-nile stages and the ventral area are visible in just a fewspecimens. Two groups showing thick main ribs but dif-ferent maximum size are distinguishable. The veryabundant small heteromorphs are generally poorly pre-served. Their casts (sculpture moulds), with perfectlypreserved sculpture, are usually pyritized.

Bed-by-bed collecting and a systematic-taxonomicstudy provide the basic data for statistical analysis of theammonite faunas from KB1 A and KB1 B. Palaeonto-

logical, palaeoecological and sedimentological investi-gations, combined with studies of lithofacies in thin sec-tions, peels from polished rock surfaces and geochemicalinvestigations (CaCO3, TOC, S), yielded informationabout the environmental conditions in the area of dep-osition. In particular, ‘parameters’ such as oxygen-level(deduced not measured), total organic carbon (TOC)content and sulphide contents help to solve the ques-tion of autochthonous versus allochthonous depositionof the ammonite shells. Sulphur analyses confirm the re-sults of many other methods used to test for anoxic oroxic conditions (e.g. TOC, HI). Thus, the sulphuranalysis methods developed by KOMA (1978) and othersappear to be applicable for the study of anoxic-dysoxicevent beds elsewhere.

The total sulphur content (weight per cent) of sam-ples from the KB1 section was analysed using X-ray flu-orescence and wet methods. All the chemical analyseswere carried out in the Laboratory of the Institute ofForest Ecology at the University of Vienna. Calciumcarbonate content was determined using the carbonatebomb technique. Total carbon content was determinedusing a LECO WR-12 analyser. Total organic carbon(TOC) content was calculated as the difference be-tween total carbon and carbonate carbon, assuming thatall carbonate is pure calcite.

Geographical setting

Both occurrences are located within the same logKB1. The section is situated in the Ternberg Nappe inUpper Austria. The exact position is about 7 km west ofLosenstein, 1 km south of Kienberg and 500 m south-west of the Klausriegler inn (652 m, ÖK 1:50000, sheet69 Großraming, Fig. 1). The stream outcrop fixed byGPS data (global positioning system: N 47°54’32“, E14°21’10“) crosses the western part of the east-weststriking Losenstein Syncline at a line between theKreuzmauer (853 m) to the north and the Pfaffenmauer(1218 m) to the south. For detailed descriptions of theinvestigation area see LUKENEDER (1997, 1998, 1999).This section was the starting point for a lateral analysisof the distribution of the reported ammonite mass-oc-currence.

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Fig. 1: Locality map of Upper Austriashowing the outcrop of Lower Cretaceous

sediments (black) around the sectioninvestigated within the Northern

Calcareous Alps. Positions of the synclinesare given in the tectonic map on the left.

(1) Losenstein Syncline, (2) SchneebergSyncline, (3) Anzenbach Syncline, (4)

Ebenforst Syncline. The position of the KB1A (blue) and KB1 B (yellow) section is

marked by a cross (x).

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The Olcostephanus occurrence (KB1 A) is situatedin the uppermost part of the KB1 ravine (800 m). Thefossiliferous limestone, comprising the Olcostephanus-bearing interval, is located on the left wall of the gorge(dipping 080/70). The Karsteniceras occurrence (KB1 B)is situated in the middle of the KB1 ravine (717 m, dip-ping 080/70).

Geological setting

The Losenstein Syncline is situated in the southern-most part of the Ternberg Nappe of the Northern Cal-careous Alps. This is followed directly to the south bythe Schneeberg Syncline, the Anzenbach Syncline andthen the Ebenforst Syncline of the Reichraming Nappe(Northern Calcareous Alps), all of which are constitut-ed by Lower Cretaceous sediments. At the section in-vestigated, the Early Cretaceous is represented by fourformations, from bottom to top the Steinmühl Forma-tion (c. 20 m, Early Berriasian to late Early Valangin-ian), the Schrambach Formation (c. 160-200 m, LateValanginian to Late Barremian), and the TannheimFormation (c. 40 m, Early Aptian to Late Aptian) andthe Losenstein Formation (c. 20 m, Albian (Fig. 2).

The investigated ammonite ‘mass-occurrences’, rep-resenting the Olcostephanus Level and the KarstenicerasLevel, are situated in the lowermost part (KB1 A, Ol-costephanus, Late Valanginian) and the upper part (KB1B, Karsteniceras, Early Barremian) of the SchrambachFormation (LUKENEDER 1997, 1998) (Fig. 3).

Case study 1: KB1 A

Facies-related evolution andsexual dimorphic pairs

The mass-occurrence of Olcostephanus (Olcostepha-nus) guebhardi morph. querolensis (Fig. 4) over an intervalof almost 3 metres (KB1 A) is interpreted to be the resultof a combination of a long-term accumulation from thewater column (autochthonous parts) during a favourabletime interval and redepositonal phases (allochthonousparts) of the Late Valanginian (S. verrucosum Zone,LUKENEDER 2004). The abundant olcostephanids reflectless offshore influences and nearness of shallow environ-ments. Parts of the Olcostephanus mass-occurrence (accu-mulation beds) show some similarities to a ‘Kondensat-Lagerstätte’. An enrichment by redeposition, currents orturbidites is proposed for only a few marly layers with ac-cumulated fragmented olcostephanids. The ol-costephanids were deposited within a phyllocrinid-ophi-urid association. Irregular echinoids proved soft bottomconditions of the secondary allochthonous depositionalenvironment (LUKENEDER 2004). The abundance of Ol-costephanus at the KB1 A section seems to be related to

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Fig. 2: Position of the outcrop at the KB1 section (centre), situated in theSchrambach Formation, with indicated exposure of the investigated detailedlogs KB1 A (top photo) and KB1 B (bottom photo).

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transgressive facies, presumably associated with sea-levelrises.

Lithological differences observed around the Ol-costephanus-Level are clearly consequences of an alteredpalaeooceanography and therefore reflect sea-level fluc-tuations during the Early Cretaceous, especially withinthe Berriasian and Valanginian stages (LUKENEDER &

REHÁKOVÁ 2004). ‘Faunal turnover’, ‘mass-occurrence’,and ‘migrations’ have always been considered to be con-trolled by transgressive and regressive cycles in variousEarly Cretaceous ammonite groups (RAWSON 1981,HOEDEMAEKER 1990).

A huge rise in sea level took place in the LateValanginian (Verrucosum Zone) succession (HOEDE-MAEKER 1990) of the lowermost Schrambach Formation(KB1), containing the Olcostephanus Level, which isdominated by the migrated genus Olcostephanus. Thepresence of Olcostephanus in the Losenstein Synclineand especially at the KB1-A section is apparently relat-ed to transgressive facies, presumably associated withsea-level rises.

This was probably within the Late Valanginiantrangression phase, which also led to a world-wide (e.g.Argentina, Mexico, Colombia, Spain, France, Italy,Switzerland, N. Germany, Austria, Czech Republic, Ro-mania, Bulgaria, Russia, Tunisia, Algeria, South Africa,Madagascar, Pakistan) spreading or even explosion andoccupation of new regions (e.g. Boreal Realm) by theOlcostephanus group. This mostly reflects the creation orrenewal of sea-ways. Comparing field evidence and pub-lished data from the Vocontian Trough (e.g. BULOT1993) supports the proposal of a facies dependence (e.g.depth, outer-inner shelf) of Olcostephanus (Ol-costephanus) guebhardi morph. querolensis also for theAustrian KB1-A occurrence (Fig. 5). The descendantsare most probably inhabitants of the outer shelf and re-lated areas. It is also suggested that Olcostephanus (Ol-costephanus) guebhardi morph. querolensis has its acmewithin the S. verrucosum Zone, whereas the ancient Ol-costephanus (Olcostephanus) guebhardi s. str. is mostabundant in the latest Early Valanginian (InostranzewiZone) (BULOT 1992; LUKENEDER 2004).

Among ammonoid genera of Tethyan origin, Ol-costephanus (which apparently originated in the westernMediterranean area during the Early Valanginian) wasdispersed over many parts of the world by the mid-Valanginian sea-level rise, when the ‘guebhardi chrono-cline’ extended to Mexico, Argentina, the AntarcticPeninsula, South Africa, Madagascar, and into the Bo-real Realm (especially the West European Province)(BULOT 1990), although it never penetrated into trulyboreal areas (RAWSON 1993).

On the northern margin of the Tethys the ammoniteassemblages of the outer platform areas in southernSpain and Provence (southern France) are dominated byOlcostephanus and by Neocomitidae (COMPANY 1987;BULOT 1993; REBOULET 1996). BULOT (1993) has showndistinct geographic distributions in some species of theOlcostephanidae in platform or basin environments.

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Fig. 3: Stratigraphic log of theinvestigated section, consisting ofthe Steinmühl-, the Schrambach-and the Tannheim formations,indicating the position of the KB1 Aand KB1 B sections.

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Studies carried out in south-east France providedgood evidence of ammonite distribution linked to facies.Among the Ammonitina, the Olcostephaninae and theNeocomitidae yielded the best examples of faunal assem-blage variations between the basin and outer shelf (BU-LOT 1993; REBOULET 1996; REBOULET & ATROPS 1997).During most of the Valanginian, Olcostephanus was splitinto two different ‘lineages’: Olcostephanus (Ol-costephanus) guebhardi (KILIAN) and related species arerestricted to the outer shelf facies, while Olcostephanus(Olcostephanus) tenuituberculatus (BULOT) and its de-scendants correspond to the basin facies (BULOT 1993).

The splitting into two facies-linked olcostephanidlineages during the Valanginian clearly shows the evo-lution within the olcostephanids. Starting from theBerriasian uni-facial, deeper-water genus Spiticeras (e.g.S. multiforme DJANÉLIDZÉ), followed by the still uni-fa-cial olcostephanid ancestor Olcostephanus (O.) drumen-sis KILIAN in the earlymost Valanginian, the key evolu-tionary point follows in the middle Early Valanginian.The evolutionarily important split into a deep-waterlineage and a more shallow-water lineage within the ol-costephanids markedly changes the picture of ol-costephanid distribution and systematics.

One lineage evolved the shelf forms from EarlyValanginianOlcostephanus guebhardi s. str., over the LateValanginian Olcostephanus guebhardi morph. typequerolensis up to Hauterivian species like Olcostephanusdensicostatus (WEGNER).

The second lineage inhabited the basins and evolvedfrom Olcostephnaus drumensis, continuing over the EarlyValanginian Olcostepanus stephanophorus (MATHERON)into the Late Valanginian species of Olcostephanus tenu-ituberculatus (BULOT), Olcostephanus balestrai (RODI-GHIERO) and Olcostephanus nicklesi WIEDMANN & DIENI.This lineage ends with the end of the Valanginian.

This differentation in Olcostephanus ended in theEarly Hauterivian with evolving species linked to bothbasin and shelf facies. These are Olcostephanus densi-costatus and its descendants Olcostephanus astierianus(ORBIGNY), Olcostpephanus sayni KILIAN and Jeanno-ticeeas jeannoti (ORBIGNY) for the Early Hauterivian.Other data from various places of the western Tethysconfirm this facies-linked distribution of Olcostephanus(Northern Caucasus, KVANTALIANI & SAKHAROV 1986;Spain, COMPANY 1987; Switzerland, BULOT 1989, 1992)and therefore underline a general trend for the entireTethys Realm (BULOT & COMPANY 1990).

Various evidence points to the fact that the evolu-tion of the Early Cretaceous olcostephanids was closelylinked to the evolution and concurrent appearance ofthe neocomitids. Olcostephanids had their widest distri-

bution when neocomitids (e.g. Neocomites appears inthe Early Valanginian) were rare or absent in the samearea, which leads to the well-known “bottle neck“ ef-fects in the evolution of the olcostephanid group. Theolcostephanids may have inhabited more shallow seasthan the neocomitids. In contrast, the neocomitids wereable to live in deeper areas. The living realm of bothammonoid groups were therefore shifted against eachother. Due to the ecological stress caused by the otherammonoid genus, the different ammonoids evolved in-to free niches of the shallower or deeper sea. The latterfact most probably explains why we can observe onlyone genus (Olcostephanus) in the shallowest facies, al-though this situation requires further investigation.

Sexual dimorphism in ammonoid cephalopods isdiscussed in detail for example by DAVIS et al. (1996)and COOPER (1981). The latter author precisely de-scribed sexual dimorphism in Olcostephanus. In Ol-costephanus, as in other ammonoids, the ontogenetic de-velopment of the shell is similar in both antidimorphs(sensu DAVIS 1972) until the onset of maturity.

Within the KB1-A olcostephanid fauna, sexual di-morphism is very apparent due to the unusually largesize attained by the macroconch forms (M; measuredspecimens = adult size), some of which exceed 102 mmin diameter. In contrast, the largest confirmed micro-conch (m) so far recorded from these beds measures on-ly slightly more than 42 mm in diameter, with the aver-age being far less (LUKENEDER 2004). The macroconchsrange in size from 82 to 100 mm and the microconchs20 to 42 mm, indicating a size overlap between antidi-morphs of approximately 20 % of the total combinedsize range of the two antidimorphs. The microconchsshow at the aperture a final constriction coupled withlateral lappets, whereas the macroconchs have only a fi-nal constriction. In Olcostephanus guebhardi, sexual di-morphism is expressed by differences not only in adultshape, size and ornament but also in the form of theapertural margin (Fig. 4).

Case study 2: KB1 B

Oxygen as impulse for evolution inheteromorph r-strategists

About 300 specimens of Karsteniceras ternbergense be-tween 5 mm and 37 mm in diameter were investigated.Juveniles, adults, including micro- and macroconchs,could be separated. A sexual dimorphism in Karstenicerascan be observed. An enrichment by redeposition throughcurrents or turbidites can be clearly ruled out based onthe autochthonous character of the nearly monospecificbenthic macrofauna (e.g. Inoceramus, Propeamussium),the preservation of fragile parts and the extraordinary

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preservation of in situ aptychi within the body chambersof Karsteniceras ternbergense (Fig. 4).

The geochemical results indicate that the assem-blage was deposited under conditions of intermittentoxygen-depletion associated with stable water masses.The rhythmicity of laminated black shale layers and

light-grey bioturbated, organic-depleted limestones sug-gests that the oxic and dysoxic conditions episodicallychanged. A highly dynamic environment, controlled byshort- and long-term fluctuations in oxygen levels, andpoor circulation of bottom-water currents within an iso-lated, basin-like region, led to the accumulation of theKarsteniceras Level. The lamination generally indicatesa very quiet depositional environment, which was notdisturbed by currents (LUKENEDER 2003).

Within the Schrambach Formation, dysaerobic (notanaerobic) conditions prevailed, allowing endobenthiccolonization of the incompletely bioturbated sedimentby Chondrites (accompanied by Planolites in some beds).Increasing levels of dissolved oxygen in bottom watersover time are suggested by well-bioturbated, pale greylimestone beds, whereas dysaerobic conditions are ex-pressed through thin, black, laminated limestones(‘black shales’). The Karsteniceras mass-occurrence issituated in the laminated horizons. The following fea-tures are observable: (1) high TOC, (2) high sulphurcontent, (3) concentrations of pyrite, (4) phosphatic si-phuncle structures, (5) indistinct lamination, (6) almostmonospecific trace fossil community (e.g. Chondrites),(7) fish remains, (8) extremely rare benthos (e.g. inoce-ramids, ‘paper pectens’), (9) rare microfauna, (10)‘mass-mortality’ of Karsteniceras, very abundant andsmall in size, (11) nearly ‘monospecific’ faunal spectrumand (12) in situ aptychi.

It is assumed that, based on the described featuresfrom KB1 B and literature data, Karsteniceras most prob-ably had an opportunistic (r-strategist) mode of life andwas adapted to dysaerobic sea-water. These ancylocer-atids most likely inhabited regions reaching from the seafloor to at least a few tens of meters into the overlyingwater-column, based on the in situ aptychi and thenearly monospecific faunal assemblage of small hetero-morphs. Most of the associated other ammonoids (e.g.Barremites cf. difficilis) show different overgrowth stages(serpulids). These can be explained as a reflection of lifein the upper, oxygenated water-column, with subse-quent sinking to the sea floor or drifting after death.Karsteniceras probably inhabited areas of water stagna-tion with low dissolved oxygen, showing abundancepeaks during times of oxygen depletion, which hinderedother invertebrates from colonising such environments.The described autochthonous Karsteniceras mass-occur-rence features fit well into the scheme of a ‘KonservatLagerstätte’ (LUKENEDER 2003).

Interbedding of sediments alternately rich and poorin organic matter can be the result of either differentialpreservation of organic matter, differential rates of sup-ply of organic matter, different sources of primary pro-duction, and/or differential sedimentation rates. Differ-

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Fig. 4: Karstenicerasternbergense

specimens from casestudy 2 (KB1 B): (A)

NHMW2001z0170/0002, x 1;(B) holotype, NHMW2001z0170/0001, x 1;

(C) NHMW2001z0170/0004, x 1;

(D) NHMW2001z0170/0003, x 1;

(E) NHMW2001z0170/0005, x 1;

(F) NHMW2001z0170/0007, x 1.

Olcostephanus(Olcostephanus)

guebhardi morph. typequerolensis specimensfrom case study 1 (KB1

A): (G) macroconch,2002z0070/0001, x 1;

(H) microconch,2002z0070/0002, x 1,

(I) macro- andmicroconch

2002z0070/0003, x 1.

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ent preservation can result if bottom waters at the accu-mulation site are alternately oxic and dysoxic (or near-anoxic). Cyclic variation in the amount of organic mat-ter accumulating at a continental margin site may beexplained by cyclic fluctuations in the thickness and in-tensity of a midwater oxygen-minimum layer. Both de-positional models (basin deoxygenation as well as ex-pansion and establishment of an oxygen-minimum lay-er) have been proposed to explain the accumulation oforganic carbon-rich strata.

Oxygen is a bio-limiting element for metazoans andis among the key factors influencing species diversityand abundance in the marine realm. Reduced concen-trations of dissolved oxygen can have disastrous conse-quences for marine life, reducing diversity and ultimate-ly leading to mass-mortality.

Factors associated with low diversity include highstress and ecological immaturity. Most opportunists (r-strategists) are characterized by small size and a shortlife span. The latter facts also hint at positive mutations.The small-sized leptoceratids seem to be resistantagainst oxygen depletion in the sea water. The robustsmall-sized forms evolved morphologies and evolution-ary adaptations which allowed them to inhabit suchhostile environments. They became accustomed to suchconditions, occurring in masses and becoming geo-graphically widespread (LUKENEDER 2003). The bodysize of the leptoceratids was therefore reduced to giverise to other features important for living in oxygen-de-pleted waters, and the opportunistic (r-strategist) modeof life was perfectly adapted to dysaerobic sea-water.This was the sense in which the word “Paläobiologie“was originally meant by its founder O. ABEL (1916). Henoticed almost 100 years ago for the cephalopods ingeneral the same relation shown for the special casespresented herein. The change in body size and morphol-ogy in Karsteniceras is accompanied causally by the spe-cialisation of the animal during environmental changes.

This phenomenon can be detected through thewhole Early Cretaceous. The phylogenetically totallyseparated Berriasian Leptoceratoides (THIEULOY 1966)show the same facies-linked distribution as that of themuch younger Barremian Veveysiceras descendants. Thefavoured sediments are clayey, dark to laminated marlswith increasing content of organic matter and pyrite.

A typical group of such opportunistic small-sizedhetermorph ammonoids is the monophyletic subfamilyLeptoceratoidinae THIEULOY. The latter subfamily is as-signed to the family Ancyloceratidae GILL. Within thelatter, three evolutionary lines are recognized; the here-in-described Karsteniceras ternbergense is a member ofone of these lines. These lineages are separated through

different morphologies and sizes. They all originate fromthe Late Hauterivian genus Veveysiceras VAŠÍČEK &WIEDMANN (VAŠÍČEK & WIEDMANN 1994). The threeimportant lineages are: 1) Karsteniceras (criocone), 2)Hamulinites (ancylocne) and 3) Eoheteroceras (ancylo-cone) together withManoloviceras (slightly curved). Allof these arose in the Early Barremian. Eoheterocerasmostprobably was the ancestor of the Late Barremian Hete-roceras. Karsteniceras forms the central stock, with mostdescendants up into the early Late Barremian.

The phylogenetically and stratigraphically separatedgroup around UHLIG’S (1883) type species Leptocerasbrunneri belongs to an unrelated earlier group from theBerriasian to Valanginian (THIEULOY 1966). No leptocer-atid transitional forms are known from the Hauterivian.

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Fig. 5: The stratigraphic position of the case studies KB1 A (blue) and KB1 B(yellow) within the Early Cretaceous (Valanginian – Barremian) of the KB1 1fauna in the Losenstein Syncline. Table after HOEDEMAEKER et al. (2003, withmodifications).

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The ancestral stock of the second and totally separatedlater micromorph Barremian group the Leptoceratoid-inae (before Veveysiceras), is still obscure. No transitionalforms can be observed and the ancestor is unknown.Veveysiceras occurred first with Pseudothurmannia in thelatest Hauterivian. The evolutionary centre expands in alongitudinal east-west region from central/southeasternEurope to Japan (VAŠÍČEK & WIEDMANN 1994).

In the field, researchers should therefore look forthin, relatively widespread (but isochronous) horizonsdominated by one species of body or trace fossil. Thethin, black laminated layers with mass-occurrences ofKarsteniceras are a case in point. The ‘normal-accumula-tion’ of Karsteniceras within such black, laminated sedi-ments is interpreted to be the result of special palaeoen-vironmental conditions (e.g. poor oxygen, low to nocurrents). Here, Karsteniceras, as a member of an oppor-tunistic (r-strategist) ammonite group, sought the un-favourable, oxygen-limited environmental conditionsthat other ammonite groups were unable to tolerate.

Taking into account the speculations on ammonoidlife-habitats, the demersal forms, feeding on the seafloor, should be very rare or even absent in the anoxiclevels (BATT 1993). VAŠÍČEK & WIEDMANN (1994) al-ready noted the possibility that the biotope of the Lepto-ceratoidinae was close to stagnant, poorly oxygenatedenvironments, where they usually occurred concentratedin ‘nests’ dominating the faunal spectrum. This has beenrecently interpreted to reflect opportunistic behaviour ofsome taxa (Bochianitidae and leptoceratoids) in un-favourable environments (CECCA 1998). Leptoceratoidand spiroceratid ecology, palaeobiology and life-habitatswere discussed by UHLIG (1883), NIKOLOV (1960),THIEULOY (1966), DIETL (1973, 1978), RIEBER (1977),VAŠÍČEK (1977), WESTERMANN (1990), VAŠÍČEK &WIEDMANN (1994), CECCA (1997) and AVRAM (1999).Summarizing the various opinions on leptoceratoid ecol-ogy, clear differences are evident between those ofTHIEULOY (1966; autochthonous life assemblage),RIEBER (1977; nektonic above anoxic bottom) andLUKENEDER (2003, nektonic in dysoxic water column),WESTERMANN (1990, 1996; distal shelf), and VAŠÍČEK &WIEDMANN (1994; autochthonous between turbidites).

Concluding remarks

This contribution shows the significant effect thatsynecological stress – caused either by environmentalchanges of abiotic factors as oxygen content, salinityand depth or by autecological stress from biotic com-petitors occupying the same environment – has on theshape and morphology of Cretaceous ammonoids. Ex-amples for different Cretaceous ammonoid shapes aregiven in Figure 6.

402

Fig. 6: Cretaceousshape examples for“normal“ coiled am-monoids: (A) phos-

phatized Placenticerasmeeki (BOEHM) withshell preservation,

Campanian, Alberta,Canada, NHMW-

2006z0260/0001 and(B) Placenticeras pla-

centa (DEKAY) showingsuture line, South

Dakota, USA, NHMW-2002z0066/0001.

Heteromorph am-monoids are: (C) Dis-

coscaphites gulosus(MORTON) with shellpreservation, Maas-

trichtian, South Dako-ta, USA, NHMW-

2006z0260/0002, and(D) Didymoceras ne-

brascense (MEEK &HAYDEN) with shell

preservation, Campan-ian, South Dakota,

USA, NHMW1980/0023/0000.

© Biologiezentrum Linz, download unter www.biologiezentrum.at

Two contrary examples (Olcostephanus andKarsteniceras) were selected to show evolutionary trendsin ammonoids. The older case study (Valanginian) dealswith “normal“ coiled Olcostephanus. A number of factsshow that the evolution of the Early Cretaceous ol-costephanids was closely linked to the evolution andconcurrent appearance of the neocomitids. Due to theecological stress generated by the neocomitids, the ol-costephanids evolved into free niches of the shallower ordeeper sea. The split into two facies-linked ol-costephanid lineages during the Valanginian clearlyshows the evolution within this group. The ol-costephanids reacted to the stress created for them byother antagonists (e.g. neocomitids).

The younger case study (Barremian) deals with thehetermorph ammonoid group around Karsteniceras. Re-duced concentrations of dissolved oxygen have obviousconsequences for marine life, reducing diversity but giv-ing rise to new forms which are resistant to oxygen-de-pleted waters. Most opportunists (r-strategists) such asKarsteniceras are characterized by small size and a shortlife span. The robust small-sized forms evolved mor-phologies and evolutionary adaptations which allowedthem to inhabit such hostile environments. They be-came accustomed to such conditions, occurred in mass-es and were geographically widespread. The change inbody size and morphology in Karsteniceras is accompa-nied causally with the specialisation of the animal overthe course of environmental changes.

Zusammenfassung

Der Status zweier Unterkreide Ammoniten Grup-pen aus Oberösterreich (Nördliche Kalkalpen) wird,mit besonderer Rücksicht auf die Evolution ihrer Form,der Morphologie und deren Umwelt-Präferenzen, aufge-zeigt. Olcostephanus guebhardi aus dem Valanginium(Verrucosum Zone, 137 Mio.) zeigt die evolutionäreTrennung der beiden Geschlechter in zwei unterschied-liche Umweltbereiche und deren Anpassung der Forman die verschieden Umweltbedingungen. Es wird ge-zeigt, dass sich der heteromorphe Ammonit Karstenice-ras ternbergense aus dem Barremium (Coronites Zone,124 Mio.) in Perioden zeitweiligen Sauerstoffmangelsgekoppelt mit stabilen, geschichteten Wassermassen,entwickelte. Basierend auf lithologischen und geoche-mischen Analysen, welche mit Untersuchungen vonSpurenfossilien, Mikro- und Makrofossilien gekoppeltwurden, wird eine Invasion einer opportunistischen (r-Strategen) Karsteniceras Biozönose während ungünstigerBedingungen angenommen. Beide Beispiele wurdenausgewählt um evolutionäre Trends in der Unterkreideaufzuzeigen, welche in der gesamten Gruppe der Cepha-lopoden beobachtet werden können.

Acknowledgements

Thanks are due to the Austrian Science Fund(FWF) for financial support (project P16100-Geo.).The author is grateful to Herbert Summesberger andMathias Harzhauser (both Natural History Museum, Vi-enna) for their thoughtful and valuable comments. Pho-tographs were taken by Alice Schumacher (NaturalHistory Museum, Vienna).

ReferencesABEL O. (1916): Paläobiologie der Cephalopodan. Aus der Grup-

pe der Dibranchiaten. — Verlag Gustav Fischer, Jena: 1-281.

AVRAM E. (1999): Some new species of the subfamily ‘Leptocera-

todinae’ (Ancyloceratina, Ammonoidea) in uppermost

Hauterivian and lower Barremian deposits from Rumania.

— Scripta Geol., Spec. 3: 31-43.

BATT R.J. (1993): Ammonite morphotypes as indicators of oxyge-

nation in a Cretaceous epicontinental sea. — Lethaia 26:

49-63.

BULOT L. (1989): Les Olcostephaninae (Ammonitina, Cephalo-

poda) dans le Crétacé inférieur du Jura Suisse et Francais.

— In: DECROUEZ D. (Ed.), Réunion Commune APF-SPS, résu-

més: 1-5.

BULOT L.G. (1990): Révision des types et figures de la collection

Matheron. 2. Olcostephanus (Olcostephanus) perinflatus

(MATHERON, 1878) et Olcostephanus (Olcostephanus) ?mit-

treanus (MATHERON non D’ORBIGNY, 1850). — Mésogée 5: 3-8.

BULOT L. (1992): Les Olcostephaninae Valanginiens et hauteriv-

iens (Ammonitina, Cephalopoda) du JuraFranco-Suisse:

Systematique et interet biostratigraphique. — Rev. Paléo-

bio. 11 (1): 149-166.

BULOT L. (1993): Stratigraphical implications of the reklations-

hips between ammonite and facies: examples taken from

the Lower Cretaceous (Valanginian-Hauterivian) of the

western Tethys. — In: HOUSE M.R. (Ed.), The Ammonoidea:

Environment, ecology and evolutionary change. Syst. Ass.

Spec. Vol. 47: 243-266.

BULOT L. & M. COMPANY (1990): Les Olcostephanus du groupe

atherstoni (Ammonitina, Cephalopoda): potential d’utilisa-

tion pour les correlations biostratigraphiques à longue dis-

tance. — In VI jornadas de la Sociedad Espanola de Paleon-

tologia, résumés: 1-34.

CECCA F. (1997): Late Jurássic and Early Cretaceous uncoiled am-

monites: trophism-related evolutionary processes. — C. R.

Acad. Sci. Paris, sér. II 325: 629-634.

CECCA F. (1998): Hypothesis about the role of the trophism in the

evolution of the uncoiled ammonites: the adaptive radia-

tions of the Ancyloceratina (Ammonoidea) at the end of

the Jurassic and in the Lower Cretaceous. — Rend. Fis. Acc.

Lincei 9. Rom: 213-226.

COMPANY M. (1987): Los Ammonites del Valanginiense del sector

oriental de las Cordilleras Béticas (SE de Espana). — Tesis

Doctorale, Univ. Granada.: 1-294.

COOPER M.R. (1981): Revision of the Late Valanginian Cephalo-

poda from the Sundays river Formation of South Africa,

with special reference on the Genus Olcostephanus. —

Ann. S. Afr. Mus. 83 (7): 147-366.

403

© Biologiezentrum Linz, download unter www.biologiezentrum.at

DAVIS R.A. (1972): Mature modification and dimorphism in se-

lected late Paleozoic ammonoids. — Bull. Am. Pal. 62: 23-130.

DAVIS R.A., LANDMANN N.H., DOMMERGUES J.L., MARCHAND D. & H.BUCHER (1996): Mature modifications and Dimorphism inAmmonoid Cephalopods. — In: LANDMANN N., TANABE K. & A.DAVIS (Eds), Ammonoid Paleobiology, Volume 13 of Topicsin Geobiology, New York, Plenum Press: 463-539.

DIETL G. (1973): Middle Jurassic (Dogger) heteromorph am-monites. — In: HALLAM A. (Ed.), Atlas of palaeobiogeogra-phy. Elsevier, Amsterdam: 283-285.

DIETL G. (1978): Die heteromorphen Ammoniten des Dogger(Stratigraphie, Taxonomie, Phylogenie, Ökologie). — Stutt.Beitr. Naturkunde 33: 1-76.

HOEDEMAEKER P.J. (1990): The Neocomian boundaries of the Te-thyan Realm based on the distribution of ammonites. —Cret. Research 11: 331-342.

HOEDEMAEKER P.J., REBOULET S., AGUIRRE-URRETA M.B., ALSEN P., AOU-TEM M., ATROPS F., BARRAGÁN R., COMPANY M., GONZÁLEZ C.,KLEIN J., LUKENEDER A., PLOCH I., RAISOSSADAT N., RAWSON P., RO-POLO P., VAŠÍČEK Z., VERMEULEN J. & M. WIPPICH (2003): Reporton the 1st International Workshop of the IUGS LowerCretaceous Ammonite Working Group, the ‘Kilian Group’(Lyon, 11 September 2002). — Cret. Research 24: 89-94.

HOUSE M.R. & J.R SENIOR (1980) (Eds): The Ammonoidea. The Evo-lution, Classification, Mode of Life and Geological Useful-ness of a Major Fossil Group. — The Systematics Associati-on, Special Volumes 18, Academic Press, London: 1-593.

KOMA T. (1978): Sulfur content and its environmental significan-ce of Paleogene muddy sediments in a part of the IshikariCoal Field, central Hokkaido, northern Japan. — Jour. Jap.Assoc. Petrol. Technol. 43: 10-18.

KVANTALIANI I.V. & A.S. SAKHAROV (1986): Valanginian Ammonitesof the Northern Caucasus (Russ.). — Geol. Balcanica 163:55-68.

LUKENEDER A. (1997): Zur Unterkreide Stratigraphie der Schram-bachschichten auf Blatt 69 Großraming. — Jb. Geol. B.-A.140 (3): 370-372.

LUKENEDER A. (1998): Zur Biostratigraphie der Schrambach For-mation in der Ternberger Decke (O.-Valanginium bis Apti-um des Tiefbajuvarikums-Oberösterreich). — Geol. Palä-ont. Mitteil. Innsbruck 23 (5. Jahrestagung der ÖPG, Lunz1998): 127-128.

LUKENEDER A. (1999): Acrothoracica-Bohrspuren an einem Belem-nitenrostrum (Unterkreide, Obervalanginium; Oberöster-reich). — Ann. Naturhist. Mus. Wien 101 A: 137-143.

LUKENEDER A. (2003): The Karsteniceras Level: Dysoxic ammono-id beds within the Early Cretaceous (Barremian, NorthernCalcareous Alps, Austria). — Facies 49: 87-100.

LUKENEDER A. (2004): The Olcostephanus Level: An Upper Valan-ginian ammonoid mass-occurrence (Lower Cretaceous,Northern Calcareous Alps, Austria). — Acta Geol. Polonica54 (1): 23-33.

LUKENEDER A. & M. HARZHAUSER (2003): Olcostephanus guebhardias cryptic habitat for an Early Cretaceous coelobite-com-munity (Valanginian, Northern Calcareous Alps, Austria).— Cret. Research 24: 477-485.

LUKENEDER A. & D. REHÁKOVÁ (2004): Lower Cretaceous section ofthe Ternberg Nappe (Northern Calcareous Alps, Upper Aus-tria): Facies-changes, biostratigraphy and paleoecology. —Geol. Carpathica 55 (3): 227-237.

LUKENEDER A. & K. TANABE (2002): In situ finds of aptychi in theBarremian of the Alpine Lower Cretaceous (Barremian,

Northern Calcareous Alps, Upper Austria). — Cret. Rea-search 23: 15-24.

NIKOLOV T.G. (1960): La fauna d’ammonites dans le Valanginien

du Prébalkan Oriental. Trav. Géol. Bulgarie. — Série Paléo.

2: 143-264.

RAWSON P.F. (1981): Early Cretaceous ammonite biostratigraphy

and biogeography. — In: HOUSE M.R. & J.R. SENIOR (Eds), The

Ammonoidea, Systematics Association Special Volume,

ASSP 18: 499-529.

REBOULET S. (1996): L’evolution des ammonites du Valanginien-

Hauterinien inférieur du bassin Vocontien et de la plate-

forme provencale (Sud-Est de la France): relations avec la

stratigraphie séquentielle et implications biostratigraphi-

ques. — Doc. Lab. Géo. Lyon 137: 1-371.

REBOULET S. & F. ATROPS (1999): Comments and proposals about

the Valanginian-Lower Hauterivian ammonite zonation of

south-eastern France. — Eclogae Geol. Helv. 92: 183-197.

RIEBER H. (1977): Eine Ammonitenfauna aus der oberen Maiolica

der Breggia-Schlucht (Tessin/Schweiz). — Eclogae geol.

Helv. 70 (3): 777-787.

THIEULOY J.P. (1966): Leptocères berriasiens du massif de la Gran-

de-Chartreuse. — Trav. Lab. Géol. Fac. Sci. l’Univ. Grenoble

42: 281-295.

UHLIG V. (1883): Die Cephalopodenfauna der Wernsdorfer-

schichten. — Denkschr. Österr. Akad. Wiss., math.-natur-

wiss. Kl. 46: 127-290.

VAŠÍČEK Z. (1977): Hukvaldy – die neue makrofaunistische

Lokalität der Schlesischen Einheit (Hauterive). — Cas. Slez.

Muz., Sér. A 26: 129-136.

VAŠÍČEK Z. & J. WIEDMANN (1994): The Leptoceratoidinae: Small

heteromorph ammonites from the Barremian. — Palaeon-

tology 37: 203-239.

WESTERMANN G.E.G. (1990): New developments in ecology of Ju-

rassic-Cretaceous ammonoids. — In: PALLINI G., CELLA F., CRE-

STA S. & M. SANTANTONIO (Eds), Fossili. Evoluzione, Ambiente,

Atti II Convegno Pergola, Tecnostampa, Pergola: 459-478.

WESTERMANN G.E.G. (1996): Ammonoid Life and Habitat. — In:

LANDMAN N.H., TANABE K. & R.A. DAVIS (Eds), “Ammonoid pa-

leobiology“ Topics in Geobiology 13, Plenum Press, New

York: 607-707.

YACOBUCCI M.M. (1999): Plasticity of developmental timing as

underlying cause of high speciation rates in ammonoids. —

In: F. OLORIZ & F.J. RODRÌGUEZ-TOVAR (Eds), Advancing research

on living and Fossil cephalopods. Proceedings of the IV In-

ternational Symposium on cephalopods: Present and Past.

Granada, Spain, Kluwer Academic /Plenum Publishers, New

York, 1999: 59-76.

YOUNG R.E., VECCHIONE M. & D.T. DONOVAN (1998): The evolution

of coloid cephalopods and their present biodiversity and

ecology. — In: PAYNE A.I.L., LIPINSKI M.R., CLARKE M.R. &

M.A.C. ROELEVELD (Eds), cephalopod diversity, Ecology and

Evolution. S. Afr. J. mar. Sci. 20: 393-420.

Address of the author:

Dr. Mag. Alexander LUKENEDERGeological-Palaeontological Department

Natural History Museum ViennaBurgring 7

1010 Vienna, AustriaE-Mail: alexander.lukeneder@nhm-wien.ac.at

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