Article: Middle Ordovician bivalves from Spain and their phyletic and palaeogeographic significance

The rich bivalve fauna from the Middle Ordovician of Spain is reviewed, and some new taxa established: Dulcineaia manchegana gen. and sp. nov., Praenucula sharpei sp. nov. and Ekaterodonta hesperica sp. nov. Some palaeotaxodontids probably had archaic characters, such as the dentition of Ekaterodonta and the pedal muscles of Myoplusia. The common trend towards the production of crenulated teeth among actinodonts and their descendants is underlined; Dulcineaia is a new example among Redoniidae. The comparison with the crenulations of some paleotaxodontids does not show any general constraints governing the evolution of microcrenulations. Bivalve distribution within the Selenopeltis province is apparently complex with some endemics during the Middle Ordovician. The Spanish faunas were largely dominated by small endobenthic shells which suggests a cool-water area.