Brachythyridoidea Frederiks, 1924

Poletaev, Vladyslav, 2024, New and revised taxa of Carboniferous spiriferides (Brachiopoda, Spiriferida) from the Donets Basin (Ukraine) and South Urals (Russia), European Journal of Taxonomy 968, pp. 132-155 : 138-139

Superfamily Brachythyridoidea Frederiks, 1924

Diagnosis emended

Outline commonly ovate; hinge line shorter than width, weakly denticulated; cardinal extremities rounded; lateral slopes usually with few simple coarse ribs or with numerous flat bifurcated ribs. Microornament absent or weakly developed. Delthyrium partially covered by deltidium or stegidial plates; subdelthyrial plates absent; ventral adminicula absent; vascular imprints pinnate or ramiform; miophragm or septum in ventral valve usualy absent. Dorsal adminicula and crural plates absent.

Remarks

The presence of a denticulated hinge line in the ventral interarea of Spirifera ovalis Phillips, 1836 has not yet been demonstrated, but this character has been found and is supported by some other data. Angiolini et al. (2011: 71) revised the Carboniferous brachiopod fauna from historical sections in England.As a result, they established the genus Latibrachythyris Angiolini et al., 2011 . The type species of Latibrachythyris is Spirifer pinguis Sowerby, 1821 and has a denticulated hinge line. Carniti et al. (2022: 865) attributed Spirifer crassus de Koninck, 1883 to Latibrachythyris and, following Angiolini et al. (2011), also Spirifer rotundatus Sowerby, 1825 . There is no doubt that the authors’ definitions of these species are correct, but the exact definition of some Brachythyris -like genera is problematic. An examination of the brachiopod collections of de Koninck (1883, 1887) at the Royal Belgian Institute of Natural Sciences in Brussels, Belgium, in 1992 showed that specimens of Spirifer subrotundatus M’Coy, 1844 (sensu de Koninck, 1887) have a primary median costa in the sulcus and a distinct short septum in the ventral valve. Therefore, this species must now be assigned to Phragmobrachythyris Poletaev 1999 from the family Skelidorygmidae Carter, 1994 ( Carter & Gourvennec 2007). A correct genus definition of all Brachythyris -like spirifers is only possible by using serial cross sections of the apical part of the shell. The data presented above have shown that Latibrachythyris has a weakly denticulated hinge line and Phragmobrachythyris has a miophragm or septum in the ventral valve. Altogether, these data do not allow to assign the families Brachythyrididae Frederiks, 1924 and Skelidorygmidae to the superfamily Martinioidea Waagen, 1883 , as I had done earlier ( Poletaev 2022).

Stratigraphic distribution

Late Devonian to Permian.