Similiclypeina langshanensis, Sun & Schlagintweit, 2025

Similiclypeina langshanensis sp. nov.

( Figs 5A, B; 6; 7)

TYPE MATERIAL. — Tibet • Northern Lhasa Terrane, Roma Chambo section . The section crops out along the eastern side of the Roma Chambo river, about 15 km SW of the Lake Dong Co in the Gerze county, Tibet ( China). The coordinates of the section base are c. 32°04’42”N, 84°31’34”E, and encompasses a part of the Langshan Formation with a thickness of 80 m that can be assigned to the Aptian. Holotype: longitudinal thallus section illustrated in Figure 7E; thin-section 21LMC-66F1 stored at the School of Earth Sciences and Resources, China University of Geosciences in Nanjing GoogleMaps .

ETYMOLOGY. — The species name refers to the Lower-mid Cretaceous Langshan Formation cropping out in the Lhasa Terrane of Tibet.

TYPE LOCALITY AND AGE. — Tibet, northern Lhasa Terrane, Roma Chambo section ( Figs 1; 2), late early ( Praeorbitolina cormyi biozone of Schroeder et al. 2010) to early late Aptian.

OCCURRENCE AND STRATIGRAPHY. — The species is widely distributed in the Roma Chambo section spanning an interval from the late early Aptian ( Praeorbitolina biozone) and parts of the late Aptian.

DIAGNOSIS. — Species of Similiclypeina with relatively thick calcareous skeleton exhibiting spinose outer appearance, rather low ratio inner-outer diameter and tilted uncompressed tubular branches.

DIMENSIONS. — See Table 1. View TABLE

DESCRIPTION

Thallus medium-sized, and cylindrical with verticils of primary laterals. Laterals tilted towards the main axis and arranged in quincunxes. The calcification consists of sparry calcite, is variable, and often displays a thick envelope around the main axis resulting in a low d/D ratio (e.g. Fig. 6B, H). Mostly the elongated tubular (uncompressed)laterals (phloiophorous type), 6 to 10 per vertical, are straight and directed away from the main axis, sometimes (top part of thallus?) bending upwards ( Fig. 7F). Along their length, the laterals only slightly widen. The verticils are rather close-set; the individual calcareous coating of the laterals results in a spinose appearance at the distal endings ( Fig. 6A). In these cases, the calcified wall shows a slight concave depression at the thallus surface between the laterals. Transverse sections of the laterals as shown in tangential thallus sections are always rounded. The inner surface (axial cavity) is smooth and well delimited.

COMPARISONS

The main feature that in our opinion justifies the separation of Similiclypeina langshanensis sp. nov. from allied taxa are the shape of the laterals. In Similiclypeina somalica (Conrad, Peybernès & Masse) , the laterals are directed almost perpendicular to the main axis and egg-shaped ( Fig. 8A, B). The laterals of the type-species S. conradi Conrad typically are flattened vertically at their proximal parts and continuously decrease in diameter outwards ( Fig. 8E, F). In addition, the diameter of the laterals is larger in S. conradi ( Table 2 View TABLE ). In Piriferella spinosa Sokač , the laterals are similar to S. somalica ( Fig. 8C, D). The laterals of S. langshanensis sp. nov. attain a length almost double than that reported from S. verrucosa Sokač and also the vertical spacing is distinctly lower ( Fig. 8G, H; Table 2 View TABLE ). For other differences in biometric parameters see Table 2 View TABLE .