Isogramma Meek & Worthe, 1870 (Dictyonellida, Brachiopoda) from the Pennsylvanian of the Cantabrian Mountains (N Spain)

Resumen

Isogramma is one of the strangest and easiest to recognize brachiopod genera. Its shells is very transverse, flattened, oval, ornamented with strong concentric ridges which cover the whole exterior of both valves, apart from a smooth triangular depressed area, extending from the beak of the ventral valve forward to beyond the umbo, the colleplax. The sell is strongly punctate which gives it a spongy structure. In this paper, the morphology and shell structure of the genus are discussed, and the species from the Catabrian Mountains assigned to the genus are revised. The species Isogramlma davidsoni, the only one thus far described for the region, is discussed and three new species are described for the Pennsylvanian of Asturian and León: Isogramma wagneri, I. casina and I. demuesensis