Schizocrania equestra, Mergl & Nolčová, 2016

Mergl, Michal & Nolčová, Lucie, 2016, Schizocrania (Brachiopoda, Discinoidea): Taxonomy, Occurrence, Ecology And History Of The Earliest Epizoan Lingulate Brachiopod, Fossil Imprint 72 (3 - 4), pp. 225-238 : 229

Schizocrania equestra sp. nov.

Pl. 2, Figs 9–19

H o l o t y p e. Dorsal valve figured on Pl. 2, Fig. 11

(PCZCU 2085).

E t y m o l o g y. Latin equestra means rider.

T y p e h o r i z o n a n d l o c a l i t y. Katian, Bohdalec Formation; Praha – Michle, temporary excavations at Chodovská Street (in year 1985).

M a t e r i a l. Four valves attached to incomplete compressed orthocone cephalopod shell and 25 dorsal valves of variable size in black shale.

D i a g n o s i s. Moderately convex Schizocrania with circular outline, low dorsal apex and costellate ornamentation of low rounded costellae as wide as shallow interspaces; 3–4 costellae per 1 mm anteromedianly in large specimens; new costellae rare, intercalated, concentric fila absent.

D e s c r i p t i o n. The shell is almost circular in adults, plano-convex, 17 wide in the largest known specimen. The ventral valve is unknown. The dorsal valve has evenly rounded margins, and moderate convex transverse and lateral profiles. The apex is located near the posterior margin, separated from it by a short band of thickened shell. The visceral area is poorly defined. Ornamentation consists of regular costellae, originating at the dorsal apex. Costellae are straight in midsector, but gently curved in posterolateral parts of the valve. Costellae are always arranged perpendicularly to shell margin and are rounded, gently increasing in size anteriorly, and separated by shallow interspaces of the same size. New costellae originate exclusively by intercalation. Concentric fila are absent, and only weak broad concentric bands (Pl. 2, Fig. 14) indicate irregularity of shell growth.

R e m a r k s. The new species is distinct in its fairly coarse and regular costellate ornamentation, with about half the number of costellae as on comparably sized shells of S. incola ( PERNER, 1903) . Schizocrania hornyi ( HAVLÍČEK, 1972) has a similar density of costellation, but its costellae are coarser, separated by narrower interspaces and the dorsal apex protrudes more posteriorly. Specimens referred to Schizocrania multistriata ( REED, 1905) from the Barrandian area differs from the new species by the less rounded posterior margin of the dorsal valve, and generally finer costellation.

O c c u r r e n c e. Type locality only.