Boueina iberica, Schlagintweit & Wilmsen, 2014

Schlagintweit, Felix & Wilmsen, Markus, 2014, Calcareous Algae (Dasycladales, Udoteaceae) From The Cenomanian Altamira Formation Of Northern Cantabria, Spain, Acta Palaeontologica Romaniae 10 (1 - 2), pp. 1-2 : 21

Boueina iberica n. sp.

Figs. 8 a-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.

Figures

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).

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).