Acanthambonia COOPER , 1956

Mergl, Michal, 2012, Lingulate And Craniate Brachiopods From The Top Of The Králův Dvůr Formation (Latest Katian) And Their Contribution To Palaeogeography, Acta Musei Nationalis Pragae Series B 68 (1 - 2), pp. 35-46 : 39

Genus Acanthambonia COOPER, 1956

Type species. – Acanthambonia minutissima COOPER, 1956 ; Middle Ordovician , Alabama, USA .

Acanthambonia (?) sp.

Text-figs 2 S-U

1982 1989

Acanthambonia sp. Havlíček and Mergl, p. 39. Acanthambonia sp. Štorch and Mergl, table 2.

M a t e r i a l: One dorsal valve ( MM 027).

D e s c r i p t i o n: Ventral valve unknown. Dorsal valve is 4 mm wide, subcircular, thin-shelled, and despite the deformation due to its collapse, it displays considerable convexity. The dorsal apex is marginal and gently extended posteriorly. Exterior lacks prominent growth lamellae. The valve shows prominent, short, tapering and radially arranged hollow spines of almost uniform size along anteri- or, lateral and posterolateral margins. Shorter spines direct- ed posteriorly are tightly spaced just laterally to the dorsal apex. Valve interior is unknown, but the bases of spines are distinct as a fine internal pustulation. However, this feature may be of a taphonomic origin.

Ventral valve is unknown.

R e m a r k s: The record of Upper Ordovician siphonotretids is scarce. Acanthambonia COOPER, 1956 and Multispinula ROWELL, 1962 are only known from the late Katian. The new shell is referred to Acanthambonia because Multispinula has strong concentric ornamentation. It is stratigraphically the youngest siphonotretid known from the Ordovician of Bohemia.

O c c u r r e n c e: Very rare at Jezerka.