. Bulletin of the Natural Histort Museum. Geology series. 25 b. 25c Fig. 25 Zalvera Sp. from early Upper Moscovian rocks north of Bran- cosera, Palencia, Spain. 25a,b, apical and lateral views of the speci- men (X1) showing an 'umbonal' region (arrowed). 25c, an enlargement (x3) of 25b showing pseudopunctate shell (arrowed) and the layered nature of the valve, each with thin sediment between. National Museum of Natural History, Leiden, WAG 77. Winkler Prins (personal communication, September 1993) as Pwlegiiliferma sp. from Austria are not Zalvera. but are more like an early form of the Permia
. Bulletin of the Natural Histort Museum. Geology series. 25 b. 25c Fig. 25 Zalvera Sp. from early Upper Moscovian rocks north of Bran- cosera, Palencia, Spain. 25a,b, apical and lateral views of the speci- men (X1) showing an 'umbonal' region (arrowed). 25c, an enlargement (x3) of 25b showing pseudopunctate shell (arrowed) and the layered nature of the valve, each with thin sediment between. National Museum of Natural History, Leiden, WAG 77. Winkler Prins (personal communication, September 1993) as Pwlegiiliferma sp. from Austria are not Zalvera. but are more like an early form of the Permian teguliferinid Acritosia. The two Moscovian specimens from northern Spain resemble Z. sihciica closely, but appear to differ in having well flattened apices, suggesting closer attachment to the substrate than seen in the specimens from the Urals. Both specimens show signs of the subparallel internal ridges, the apical internal microtuberculation and both have comparable external irregular rugae. These similarities between the Spanish and Russian specimens reinforce the concept of widespread marine faunas in Eurasia during Upper Carboniferous times. Present evidence, therefore, indicates two almost contemporaneous stocks in the early to mid Upper Carboniferous, one in North America which evolved into the Richthofeniidae, the other in Russia which, although considered as belonging in the Richthofenioidea, was an early 'experimental' stock which lost its spines early in ontogeny and lived on relatively soft substrates, unlike the American forms Figs 22-24 Za/vera iZ/'fl/ca gen. et sp. nov. from late Bashkirian to early Moscovian rocks in the southern Urals, Russia. 22, a cut and lightly etched section through a ventral valve just distal to the inter- I nal thickening against which the dorsal valve rested. Apex to the top j right, exterior to the left. Irregularities in the laminae are oblique sec- , tions through pseudopunctae, apparently with taleolae (arrows), BD9669a, x 160. 2
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