Deliella sp.

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 : 42

Deliella sp.

Text-figs 2M, N

M a t e r i a l: One dorsal valve (PCZCU 1823).

D e s c r i p t i o n: The dorsal valve is tall, conical, 1.1 mm wide, thin-walled, circular, with scalloped outline. It bears 16 coarse radial ribs, a few of them originating by intercalation, remaining extended from the apex. Growth lines are not preserved.

R e m a r k s: The shell most likely represents a young individual. The coarse radial ribbing of the shell is unique among Bohemian Ordovician craniides, which are smooth or have a scalloped surface and therefore have been referred to Petrocrania ( HAVLÍČEK 1994b) . The Katian and Hirnantian costate craniides are generally rare and therefore they are often left in open taxonomic nomenclature. Ordovician craniides with distinct radial ornamentation were attributed by many authors ( Cooper 1956, Bergström 1968, Popov and Pushkin 1986, Havlíček 1994a) to Philhedra KOKEN, 1889 , but Philhedra is an endemic Baltic craniid genus characterised by radial rows of hollow spines (Basset 2000). True Philhedra is pre-Katian in age (Basset 2000).

Halamski (2004) erected the genus Deliella for radially costate craniides. Deliella is known from the Middle Devonian, but these Devonian species ( Halamski 2004, Franke 2012) have unknown Silurian or Ordovician ancestors. However, the similarity in shape and ornamentation of Devonian Deliella species to radially costate Upper Ordovician shells is striking (e.g. Philhedra metatypotheisa HUENE, 1900 ). Therefore the single described shell is referred to Deliella , and the Hirnantian craniides mentioned below may be referred to this genus.

Havlíček (1994a) described and illustrated Philhedra sp. from the top of the Hirnantian in the Prague Basin. Temple (1965) described Philhedra ? stawyensis from the Hirnantion of Poland, but this species clearly shows a different mimic type of coarse ornamentation and should be reassigned to Petrocrania . Bergström (1968) described and illustrated the Hirnantian Philhedra sp. A . from Västergötland, Sweden as having distinct radial ornamentation.

O c c u r r e n c e: Rare at Praha –Řeporyje.