calcareous algae (dasycladales, udoteaceae) from … · calcareous algae (dasycladales, udoteaceae)...

ACTA PALAEONTOLOGICA ROMANIAE (2014) V. 10 (1-2), P. 15- 24

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1Lerchenauerstr. 167, 80935 Munich, Germany, [email protected] 15 2Senckenberg Naturhistorische Sammlungen, Königsbrücker Landstraße 159, 01109 Dresden, Germany, [email protected]

CALCAREOUS ALGAE (DASYCLADALES, UDOTEACEAE) FROM THE

CENOMANIAN ALTAMIRA FORMATION OF NORTHERN CANTABRIA, SPAIN

Felix Schlagintweit1 & Markus Wilmsen2

Received: 15 April 2014 / Accepted: 13 June 2014 / Published online: 17 September 2014

Abstract An assemblage of calcareous algae (Dasycladales, Udoteaceae) is described from the upper Lower to

Middle Cenomanian Altamira Formation of the North Cantabrian Basin, northern Spain. The algae occur in bioclastic

for-algal grain-/packstones and near-reefal rudstones of an external carbonate platform facies. An equivalent

assemblage is known from the late Albian of the Pyrenees and the Basco-Cantabrian Chains. One new species is

introduced as Boueina iberica n. sp.

Keywords: Calcareous Algae, Dasycladales, Udoteaceae, Boueina, Systematics, Cenomanian

INTRODUCTION

Mid-Cretaceous (Albian–Cenomanian) sediments are

widespread and superbly exposed in coastal sections of

the North Cantabrian Basin in northern Spain (Wiedmann

et al., 1983; Reitner, 1987; Wilmsen, 1996, 1997, 2000).

Shallow water carbonates with larger benthic

foraminifera (orbitolinids) and calcareous algae are well

represented by the Lower–Middle Cenomanian Altamira

Formation of Cantabria, representing the deposits of the

shelf-attached Altamira Platform. In the present

contribution, the inventory of calcareous green algae

coming from three coastal sections of the Altamira

Formation is presented.

GEOLOGICAL SETTING

The study area is located in the northern part of the

Spanish province of Cantabria, along the coast of the Bay

of Biscay (Fig. 1). Due to opening of the Biscay Ocean in

Cretaceous times (e.g., Olivet, 1996), numerous

sedimentary (intra-shelf) basins developed in the North

Iberian passive margin, often in halfgraben settings due to

the tilting of fault blocks.

The North Cantabrian Basin (NCB, Wiese & Wilmsen,

1999) represents one of these extensional basins, which

developed as an independent tectono-sedimentary unit in

the mid-Valanginian (Wilmsen, 1997, 2000, 2005).

During the mid-Cretaceous (Aptian–Cenomanian), the

NCB was an E–W-elongated, gulf-like embayment

opening to the strongly subsiding Basque Basin/Navarro-

Cantabrian Ramp in the east, and the basin progressively

shallowed to the west. Wet (sub-)tropical climatic

conditions in a palaeo-latitude of about 30oN prevailed

(Rat, 1989; Philip & Floquet, 2000), and the mid-

Cretaceous (Aptian–Turonian) depositional history of the

NCB has been discussed in considerable detail by

Wilmsen et al. (1996), Wiese (1995, 1997), Wilmsen

(1997, 2000, 2005), Wiese and Wilmsen (1999) and

Najarro et al. (2011).

The studied thin-sections have been prepared from

rock specimens sampled from the Cenomanian Altamira

Formation (Fig. 2). Previous studies of this unit

concentrated on isolated sections or on special features

such as hardgrounds or patch reefs (Reitner, 1987, 1989;

Reitner, et al., 1995; Wilmsen, 1996). The first detailed

study based on numerous measured sections resulted in a

regional integrated stratigraphic framework of the

Fig. 1 Locality map of the study area with indication of the Liencres (Playa de Somocuevas),

Cobreces–Toñanes and La Rabia sections (modified from Wiese, 1997).

mailto:[email protected]

Felix Schlagintweit & Markus Wilmsen

16

complete Cenomanian succession (Wilmsen, 1997).

The well-known Cenomanian transgression was

subdivided by Wilmsen (2000) into an earlier

constructive phase and a later destructive phase,

separated by a significant low sea-level stand in the Early

to Middle Cenomanian boundary interval. In a first step,

the Cenomanian sea inundated a deltaic system of latest

Albian to earliest Cenomanian age (Bielba Formation,

lower member; see Fig. 2).

Fig. 2 Lithostratigraphy of the uppermost Albian and

Cenomanian in the study area (after Wilmsen, 1997).

This flooding of the north Iberian continental margin

in the earliest Early Cenomanian promoted the

establishment of a carbonate ramp (Bielba Formation,

upper member), evolving into a shelf-attached platform

(lower Altamira Formation) during the remaining part of

the Early Cenomanian. A major sea-level fall at the

Early/Mid-Cenomanian boundary exposed the Altamira

Platform and ended the constructive phase. During the

Middle to early Late Cenomanian destructive phase, the

platform drowned, first in the eastern part of the NCB,

later in the west (Wilmsen, 2000). An associated Fe-rich,

diachronous (Middle to early Late Cenomanian),

condensed discontinuity surface known as “Nivel

ferruginizado” or “Hardground 99” caps the Altamira

Formation, forming the drowning unconformity of a

stepwise platform drowning event (Wilmsen, 2000: fig.

3).

The algae-bearing samples studied are from the

following sections (Fig. 1):

a) The Liencres section, ca. 10 km west of Santander

(standard succession).

Base of the section: 43° 28' 11.58'' N, 3° 56' 39.79" W

Top of the section: 43° 28' 10.68'' N, 3° 56' 11.85" W

The Liencres section represents the standard for the

Cenomanian in the North Cantabrian Basin (Wilmsen et

al., 1996). The ca. 205-m-thick succession is exposed at

the coast of the Bay of Biscay, north of Liencres, in the

eastern part of Playa de Somocuevas. It comprises the

uppermost Albian to lowermost Cenomanian Bielba

Formation (ca. 130 m) and the ca. 75 m thick Altamira

Formation (Lower to lower Middle Cenomanian; see also

Wilmsen, 1997: pp. 37–51, figs 18, 20). The algal-

bearing samples (samples S 133, S 135, S 176, S 178 and

S 180) are from the upper part of the formation. One

additional sample (AM 2), likewise from the upper part

of the formation, is from a nearby section east of Playa de

Las Dunas, ca. 1 km to the southwest of Playa de

Somocueveas (43° 27' 46.69" N, 3° 57' 0.07" W).

b) The Cobreces-Toñanes section.

Base of the section: 43° 23' 46.59" N, 4° 13' 5.05" W

Top of the section: 43° 23' 54.69" N, 4° 11' 53.98" W

This 330-m-thick section is exposed along the coast

between the villages of Cobreces and Toñanes. At this

section, the Bielba Formation has a thickness of 195 m

and the Altamira Formation of 135 m. The succession

that has been described in detail by Wilmsen (1997, pp.

88–97, detailed log in fig. 46) includes a patch reef

complex (Wilmsen 1996). Samples Co 33, 35, 37 and 41

are from the upper Lower Cenomanian (below the patch

reefs).

c) The La Rabia section, ca. 2 km west of Comillas.

Base of the section: 43° 23' 30.51'' N, 4° 18' 41.15" W

Top of the section: 43° 23' 26.34'' N, 4° 19' 03.46" W

The ca. 300-m-thick La Rabia section is exposed along

the coast east of the mouth of the small river Rio Turbio.

The section commences above the Upper Albian Caprina

Limestones with the Bielba Formation (ca. 160 m thick),

followed by the Altamira Formation (ca. 140 m). A

comprehensive description and detailed log has been

published by Wilmsen (1997: pp. 97–105, fig. 49).

Samples LR 110, LR 149, LR 170, LR 198, LR 202, LR -

5 and LR-2 have been taken from the interval between

185 m (LR 110, lowermost sample) und 297 m (sample

LR-2), corresponding to the Lower (LR 110, 149) and

Middle Cenomanian, respectively.

MICROFACIES, MICROPALAEONTOLOGY,

STRATIGRAPHY

The samples mostly comprise bioclastic grain- to

packstones with foraminifers, echinoderm fragments and

fine-grained debris of corals and sponges (Fig. 3a). Apart

from a diverse assemblage of trocholinids, benthic

foraminifers include subordinate miliolids (e.g.

Meandrospira washitensis Loeblich & Tappan,

Epistomina sp., Gavelinella sp., Lenticulina sp.,

Dictyopsella cf. libanica Saint-Marc), small nezzazatids,

Phenacophragma cf. assurgens Applin, Loeblich &

Tappan, Altamirella biscayana Schlagintweit, Rigaud &

Wilmsen and orbitolinids such as Orbitolina concava

(Lamarck), Conicorbitolina corbarica (Schroeder), and

Conicorbitolina conica (d´Archiac). Planktonic

foraminifera are represented by the finely pustulose tests

of Favusella washitensis (Carsey) and more rarely

specimens of Rotalipora. The observed calcareous algae

are clearly dominated by dasycladaleans (Dissocladella,

Trinocladus, Neomeris) and halimedaceans, and very rare

Calcareous algae (Dasycladales, Udoteaceae) from the Cenomanian Altamira Formation of northern Cantabria, Spain

17

gymnocodiaceans (genus Permocalculus). Rhodophycean

algae only include some fragments of solenoporaceans

and Marinella lugeoni Pfender. Another microfacies type

is represented by wacke- to packstones, sometimes

floatstones, with reddish matrix and iron-stained oncoidal

crusts enveloping the bioclasts (Fig. 3b-c). The

microfauna is dominated by an assemblage of orbitolinids

and large-sized trocholinids, the microflora by

Trinocladus tripolitanus Raineri and debris of Halimeda.

It cooresponds to the middle Cenomanian “arenite-oncoid

facies” described by Reitner (1987, e.g., pl. 44, fig. 8)

from the Basco – Cantrabian Basin, comprising also the

area of Tonanes (locality b, see above) (Figs. 3b–c).

This microfacies is furthermore characterized by

excellent preservation of microstructural details of

primary aragonitic foraminifera (trocholinids,

epistominids) and some algae (Fig. 4). Some of the algae-

bearing samples can be classified as near-reefal rudstones

with large metazoan bioclasts [corals, sponges, e.g.,

Spirastrella (Acanthochaetetes) sp.] (Fig. 3d). A

characteristic floral element of these rudstones (that is

lacking in the grainstones) is Frederica aff.

conicoconvexa Dieni, Massari & Radoičić. We also

observed the encrusting arcervulinid Menaella

Fig. 3 Microfacies of the Cenomanian algal-bearing carbonates (Altamira Formation) of Cantabria, Spain. a

Packstone with benthic foraminifera, e.g., Lenticulina sp. (L), trocholinids (t), and calcareous algae

Dissocladella? n. sp. 1 Conrad & Peybernès (D). b-c Wackestone with trocholinids, orbitolinids [Conicorbitolina

(C) in c], Trinocladus tripolitanus Raineri (T), Neomeris cf. mokragorensis Radoičić & Schlagintweit (N). Note

the oblique section of Coscinoconus indet. showing the complex canal system (arrow). d Reefal rudstone with

Spirastrella (Acanthochaetetes) sp. and some trocholinids (circles). Thin-sections: S 180 (a), Co 35 (b), Co 41

(c), AM 2 (d). Scale bars 1.0 mm.

Fig. 4 Examples of preservation of primary aragonitic microfossils (benthic foraminifera and algae). a-b

Coscinoconus sp. and Epistomina sp. showing lamellar microstructure. c Halimeda sp. 1. Thin-sections: Co 41 (a-

b), LR 110 (c). Scale bars 0.2 mm.


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bustamantei described by Cherchi and Schroeder (2005)

from the uppermost Albian of the Caniego Limestone of

northern Spain. The bioclastic grain-/packstones and the

rudstones are laterally associated as evidenced by the

more or less equivalent micropaleontological associations

of algae and foraminifera and interfingering in the field.

The orbitolinids indicate early and mid-Cenomanian ages

(e.g., Schroeder & Neumann, 1985). It is worth to

mention that the above listed foraminifera do not occur

all together but represent the observed spectrum in this

interval.

SYSTEMATICS

The thin-sections studied are housed in the

Palaeozoological collection of the Senckenberg

Naturhistorische Sammlungen Dresden (repository SpK).

The samples from Liencres (Playa des Somocuevas) are

abbreviated with S, from La Rabia with LR, from

Cobreces with Co, from Cabo Toñanes with CT, and

those from Las Dunas with AM. The calcareous algae

listed below are described and the semi-quantitative

abundances in the studied thin-sections (X = rare, XX =

common, XXX = abundant) are indicated just for general

orientation.

Dasycladales

Dissocladella? n. sp. Conrad & Peybernès, 1982

(XXX)

Dissocladella bonardii Radoičić, Conrad &

Carras, 2005 (XX)

Dissocladella? sp. (X)

Neomeris cf. mokragorensis Radoičić &

Schlagintweit, 2007 (X)

Trinocladus tripolitanus Raineri, 1922 (XXX)

Frederica aff. coniconvexa Dieni, Massari &

Radoičić, 1985 (X)

Terquemella sp. (X)

Udoteaceae

Boueina hochstetteri Toula (X)

Boueina iberica n. sp. (XX)

Halimeda sp. 1 (X)

Halimeda sp. 2 (X)

Order Dasycladales Pascher, 1931

Family Dasycladaceae Kützing, 1843

Genus Dissocladella Pia, 1936

Dissocladella? n. sp. 1 Conrad & Pybernès, 1982

Figs. 3a (pars), 5

1982 ?Dissocladella nov. sp. 1 - Conrad & Peybernès, p.

778, pl. 1, figs. 5-10.

1987 Dissocladella n. sp. - Reitner, pl. 21, fig. 4, pl. 27,

figs. 1–3, pl. 36, fig. 5 (Dissocladella sp.).

Description: Rather frequent, discoidal to elliptical

sections (most values between 0.4 and 0.65 mm) can be

observed displaying a large and mostly round, central

pore with diameters from 0.07 to 0.15 mm (Fig. 5b-h).

Rather commonly, the median plane is crossed by a

central canal (diameter ~0.02 to ~0.04 mm). From both,

the central pore and the canal, regularly spaced branching

pores arise (e.g., Fig. 5c). Another type of sections,

interpreted as longitudinal sections, is represented by

cylindrical, bended morphologies of various lengths

depending on state of fragmentation (e.g., Fig. 5i versus

5j). The greatest observed length is about 4.4 mm

provided by a specimen illustrated by Reitner (1987, pl.

27, fig. 1), re-illustrated here in Fig. 5a. This specimen

shows a swollen part which roughly doubles the thickness

of the non-swollen portion. Oblique sections through

such swollen parts may result in the elliptical forms

described above (Figs. 5b-h). In some parts of the non-

swollen portion (diameter: 0.15-0.3 mm), a central canal

occurs discontinuously from which regularly arranged

(vertical spacing h: 0.065-0.08 mm) branching pores arise

from both sides. In tangential sections, a row of pores

arranged in line each with four thin diverging pores, can

be observed (Figs. 5i-l).

Remarks: Already Conrad & Peybernès (1982) remarked

that the thickened parts represent a uncommon feature in

dasycladalean algae that in consequence prevented them

from formally introducing a new species. In fact, these

unusual sections are so frequent that they cannot be

considered as “aberrant” specimens but represent the

“normal” thallus morphology that cannot be

accommodated in the spectrum of standard morphotypes

(e.g., Bassoullet et al., 1975, fig. 1; De Castro, 1997).

From the longitudinal section of Reitner (1987) it can be

deduced that the thallus of Dissocladella? n. sp. 1 was not

straight cylindrical but irregularly bended. In sections,

this obviously leads to a shift from parts cutting the

central canal and parts transecting only the calcareous

skeleton. The swollen, thickened parts might belong to

parts where the thallus displays both a more pronounced

bending and swelling. The swelling obviously went along

with a widening of the main axis in this part. Conrad &

Peybernès (1982) interpreted the large central pore of the

ellipsoidal sections (Figs. 5b-h) as representing fertile

organs. It is here interpreted as thickened part of the main

axis.

Dissocladella bonardii Radoičić, Conrad & Carras, 2005

Figs. 6a-i

*2005 Dissocladella bonardii n. sp. - Radoičić et al., p.

313–316, pl. 1, figs. 4-17 (with synonymy).

2010 Dissocladella sp. - Bucur et al., p. 32, pl. 2, fig. 4.

Description: Thallus small, cylindrical with a rather

smooth main axis. The length of the primary (set

perpendicular to the axis) and the secondary laterals is

almost equal. The secondaries widen distally thus

reaching almost the same diameter as the primaries. In

the studied material, D. bonardii often occurs as core of

oncoids or in lumps displaying oncolithic coatings (Fig.

6d-f, i).

Dimensions (data of Radoičić et al., 2005 in brackets):

D: 0.15-0.2 mm (0.14-0.35 mm)

d: 0.06-0.08 mm (0.05-0.13 mm)

d/D: 0.33-0.47 (0.24-0.44)

h: 0.05-0.06 mm (0.037-0.049 mm)

p: 0.015-0.025 mm

p´: ~0.02 mm

w: 6-8 (7; 8 according to Pia, 1936)

Remarks: The species in question was previously

established and subsequently reported (see synonymy in

Radoičić et al., 2005) as Dissocladella undulata (Raineri,

1922). According to the revision of Radoičić et al.

(2005), the species was based on heterogeneous

specimens.


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Therefore, the species D. bonardii was “introduced for

the genuine specimens of Dissocladella, in replacement

of D. undulata” by Radoičić et al. (2005, p. 311). In the

Spanish specimens, an undulation of the main axis (with

widening at the vertical planes) that represents the

original name-giving character (see also Pia, 1936, p. 4,

“constricted between the whorls”) is not detectable. This

diagenetic feature is not necessarily present (e.g.,

Radoičić et al., 2005, pl. 1, fig. 17).

Genus Neomeris Lamouroux, 1816

Neomeris cf. mokragorensis Radoičić & Schlagintweit,

2007

Figs. 3c (pars), 6j-l

1987 Neomeris cretacea - Reitner: pl. 44, fig. 6.

*2007 Neomeris mokragorensis n. sp. - Radoičić &

Schlagintweit, p. 43-44, fig. 7, pls. 1-2, pl. 3, figs. 1-6

(with synonymy).

Remarks: Some thallus fragments displaying

subspherical fertile ampullae and light-brown

preservation are referred to Neomeris mokragorensis,

described from the Albian and Turonian of Serbia

(Radoičić & Schlagintweit, 2007). It co-occurs with

Trinocladus tripolitanus Raineri, Halimeda sp. 1, and a

trocholinid-orbitolinid foraminiferan assemblage

preferentially in the oncolithic wacke-packstones with

iron-impregnated bioclasts.

Genus Trinocladus Raineri, 1922

Trinocladus tripolitanus Raineri, 1922

Figs. 3b-c (pars), 6m-u

*1922 Trinocladus tripolitanus n. gen., n. sp. - Raineri:

79, pl. 3, figs 15-16, Upper Cretaceous of Lybia.

1982 Trinocladus tripolitanus Raineri - Conrad &

Peybernès, p. 777, pl. 1, figs. 1-4.

1983 Trinocladus tripolitanus Raineri - Schroeder &

Willems, figs. 4.11 and 4.12.

1987 Trinocladus tripolitanus Raineri - Reitner, pl. 33,

fig. 4, pl. 44, fig. 2.

Remarks: T. tripolitanus is one of the most common

algae observed in the Altamira Formation. Relying on the

detailed description of Raineri (1922) and Pia (1936), just

a few remarks are given here. First of all, we note the

common occurrence of slightly club-shaped thallus

fragments (Figs. 6r, s), and an occasional occurrence of a

secondary widening of the main axis at the levels of the

laterals (Fig. 6r). In rare cases, the calcareous skeleton

around the primaries is more or less completely dissolved

given the outline of rounded embayments (Fig. 6u). The

main axis may be outlined just by a thin calcareous

envelope.

According to Reitner (1987, fig. 110, and p. 210), T.

tripolitanus is restricted to the reef flat areas, platform

sands (shoals) and the open lagoon of the Albian-

Cenomanian carbonate platforms of northern Spain. It

ranges up to the Santonian–Campanian boundary

(Barattolo, 2002, tab. 2).

Trinocladus sp.

Fig. 6v

Remarks: One transverse section, slightly larger than

most specimens of T. tripolitanus and with a secondarily

widened, undulating axial cavity is here treated as

Trinocladus sp. Concerning the conspicuous dissolution

features, we note similarities to both Trinocladus

undulates (Raineri, 1922) (see Radoičić, Conrad &

Fig. 5 Dasycladalean algae from the Albian (a) and Cenomanian (b-m) of Cantabria, Spain. a-l Dissocladella? n. sp.

1 Conrad & Pybernès, 1982. a from Reitner (1987, pl. 27, fig. 1). Thin-sections: LR 170 (b), S 180 (c), S 176 (d, f),

LR HG-5 (e, g-h), LR 149 (i, l), S 178 (j-k).


20

Carras, 2005) from the Upper Cretaceous of Lybia and to

specimens of Trinocladus divnae Radoičić illustrated by

Bucur et al. (2010, e.g., pl. 1, fig. 7) from the

Cenomanian of Egypt. T. divnae was described from the

Cenomanian of Serbia (Radoičić, 2006). On the other

hand, comparable diagenetic alterations may also occur in

T. tripolitanus (Fig. 6u).

?Family Polyphysaceae Kützing, 1843

Forma genus Frederica Barta-Calmus, 1967, emend.

Dieni et al., 1985

Frederica aff. coniconvexa Dieni, Massari & Radoičić,

1985

Figs. 7a-d

*1985 Frederica coniconvexa n. sp. - Dieni et al., 9-10,

fig. 4, pl. 2, figs. 47-54.

Remarks: The subconical to roughly triangular-rounded

bodies (diameter: ~0.25-0.4 mm) exhibiting 11 to ~16

densely set peripheral pores (diameter: 0.03-0.05 mm)

were observed in the near-reefal rudstones (Fig. 3d).

Total number of pores cannot be evaluated due to the

poor preservation. The triangular shape is often

transformed into rounded shapes due to marginal erosion.

The Cenomanian forms can be compared with those

described by Dieni et al. (1985) from the Palaeocene of

Sardinia. The genus Frederica Barta-Calmus was so far

only known from Danian–Priabonian strata (Barattolo,

2002, tab. 1). As for Acicularia and Terquemella, also

Frederica represents a form genus as representing

pluricystate fertile ampullae (see diagnosis of Dieni et al.,

1985).

Fig. 6 Dasycladalean algae from the Cenomanian of Cantabria, Spain. a-i Dissocladella bonardii Radoičić, Conrad &

Carras, 2005. j-l Neomeris cf. mokragorensis Radoičić & Schlagintweit, 2007. m-u Trinocladus tripolitanus Raineri. v

Trinocladus sp. ma = main axis, 1-3 = orders of laterals. Thin-sections: LR 198 (a), HG 5 (b), S 176 (c), S 178 (d-j),

Co 41 (k, o, r, u), S 133 (l), LR 110 (m, t), Co 33 (n, q, s), Co 37 (p, v).


21

Fig. 7 Dasycladalean algae from the Cenomanian of Cantabria,

Spain. a-d Frederica aff. coniconvexa Dieni, Massari &

Radoičić, 1985. e-f Terquemella div. sp. Thin-sections AM 2

(a-d, f), S 135 (e).

Forma genus Terquemella Munier-Chalmas ex. Morellet

& Morellet, 1913

Terquemella div. sp.

Figs. 7e-f

Remarks: Different morphotypes of Terquemella were

rarely observed in the near-reefal rudstones (Fig. 3d). For

a recent taxonomic summary, see Bucur et al. (2012).

Order Bryopsidales Schaffner, 1922

Family Udoteaceae (Endlicher) Agardh, 1887-1888

Genus Boueina Toula, 1884

Boueina iberica n. sp.

Figs. 8a-t

Holotype: Specimen in longitudinal section in Fig. 8a,

thin-section LR 202.

Origin of the name: Refers to the occurrence in Spain.

Type locality: La Rabia section, ca. 2 km west of

Comillas (Fig. 1).

Type level: Altamira Formation, middle Cenomanian.

Diagnosis: Small and well calcified representative of

Boueina. Medullary zone broad, with rather thick

filaments (compared to the thallus diameter), subparallely

arranged to the thallus axis. Cortical zone narrow, with

branching filaments smaller in diameter than those of the

medullary zone. Thallus uncompressed, circular in

transverse section.

Description: Thallus fragments (termed segments here)

cylindrical in shape (greatest observed length: 1.8 mm,

holotype specimen in Fig. 8a) and well calcified

comprising both medullary and cortical zones. Transverse

sections of the segments are circular in outline. The outer

part of the segments is often micritized and displays signs

of erosion. The medullary zone comprises about 60 to 70

% of the total diameter and consists of interwoven

filaments arranged subparallel to the longitudinal axis.

The medullary filaments are rather thick compared to the

segment diameter (see Remarks, i.e., differences to other

Boueina species).

The cortical filaments are bended towards the axis. Shape

and order of branching are masked by their poor state of

preservation.

Dimensions (mm): external diameter (D) = 0.15-0.35

(mean 0.23), diameter of the medullary filaments =

0.015-0.04 mm (mean ~0.025 mm).

Comparisons: B. iberica represents the smallest

representative of the genus. The only species that comes

near in dimensions is Boueina minima Bucur, Rashidi &

Senowbari-Daryan, 2012 from the Barremian - ?lower

Aptian of Iran with diameters from 0.23-0.48 mm (mean:

0.34 mm). Boueina pygmaea from the Upper Cretaceous

of Lybia has segment diameters from 0.5 -0.9 mm (Pia,

1936). For data on dimensions of different Boueina

species, see Bassoullet et al. (1983: Tab. 5) and Bucur et

al. (2012: Tab. 3).

The size ratio of the diameters of the medullary filaments

and the thallus segments represents a further

characteristic of B. iberica. For example the ratio of

diameter segment/diameter medullary filaments (using

mean values) is 0.05 in B. montcharmonti (De Castro et

al., 2008: tab. 1) or ~0.08 in B. minima (see Bucur et al.,

2012) compared to ~0.1 in B. iberica. Whether the thallus

of B. iberica was tree-like branching (see fig. 1 in De

Castro et al., 2008) or simple cylindrical is unknown.

Boueina hochstetteri Toula, 1884

Figs. 8u-w

*1884 Boueina hochstetteri n. gen., n. sp. - Toula: p. 41-

46, pl. 5, figs. 10a-b, pls. 7-9.

1994 Boueina hochstetteri Toula - Bucur: p. 160, pl. 16,

figs. 1-2, 4, 6-14, pl. 7, figs. 1-4, 7-16.

Remarks: Segment fragments of B. hochstetteri are not

as common as B. iberica in the studied thin-sections.

They occur in external platform for-algal packstones. The

diameter of the Cenomanian segments is 0.8 to ~1.0 mm

(Toula, 1884: up to 3.5 mm) and can therefore (without

taking into consideration other features) easily be

differentiated from Boueina iberica.

Genus Halimeda Lamouroux, 1812

Halimeda sp. 1

Figs. 9a-c

Halimeda sp. 2

Fig. 9d

Remarks: Halimeda sp. 1 and sp. 2 are separated mainly

on the base of their utricle structure. In Halimeda sp. 1,

the cortex consists of large subconical primary utricles

bearing short bulbous higher order utricles.

The utricles are arranged more or less perpendicular to

the well calcified medulla. In Halimeda sp. 2, the utricles

of the cortex are slender and bended towards the medulla.

The preservation of the material is insufficient for

specific assignment and biometric measurements. The

medullary zone is generally well calcified in Halimeda

sp. 1 and poorly calcified in the specimen of Halimeda

sp. 2. Whether this is a just an accidental observation is

unknown.


22

CONCLUDING REMARKS

The microfacies inventory of the Lower–Middle

Cenomanian Altamira Formation of northern Cantabria

(Spain) has been studied based on numerous thin-sections

from three sections that have been measured in great

detail. Stratigraphic and micro-/biofacies analyses

indicate that the sediments have been deposited on a

shelf-attached platform (Altamira Platform). The external

platform facies is characterized by a moderately diverse

dasycladalean–udoteacean assemblage. Amongst the

dasycladales, representatives of Trinocladus and

Dissocladella predominate, associated with udoteaceans

(Boueina, Halimeda). One new species of Boueina is

described as B. iberica, characterized (among other

features) by the smallest segment diameters observed in

the genus. Although the Late Albian Caniego Limestone

of southern Cantabria lacks a detailed investigation of its

algal assemblages, the published results available in the

literature suggest a similar microflora as reported from

the Lower–Middle Cenomanian Altamira Formation of

north Cantabria.

Fig. 8 Udoteacean algae from the Cenomanian of Cantabria, Spain. a-t Boueina iberica n. sp. u-w Boueina

hochstetteri Toula. Thin-sections: LR 202 (a), LR HG-5 (b, d-e, g-k, m-t), LR 110 (c), LR 2 (f, l), LR 170 (u, w),

LR 202 (v).


23

ACKNOWLEDGEMENTS

Marc Conrad (Perly) is thanked for inspiring discussion

on ?Dissocladella n. sp. 1. The reviewers Ioan Bucur

(Cluj-Napoca) and Jochen Kuss (Bremen) are thanked for

helpful comments.

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