Presence of punctae in the 'plectorthoidean' brachiopod Famatinorthis turneri (Middle Ordovician) from western Argentina: implications for early diversification of punctate orthides

BENEDETTO, J.L.

LETHAIA

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2013 vol. 42 p. 170 - 179

0024-1164

Famatinorthis Levy & Nullo is a distinctive orthide brachiopod of Dapingian age from the volcanoclastic rocks of the Famatina Range of western Argentina. Although it was classified originally among the plectorthoideans, a new collection from the La Escondida Formation yielded exceptionally well-preserved moulds of Famatinorthis turneri on which silicified infillings of punctae are clearly visible, which lead to it being reassigned to the dalmanellidines. In this paper, phylogenetic analysis is used to determine the evolutionary relationships of Famatinorthis, the Tremadocian linoporellid Lipanorthis, and other Ordovician Gondwanan genera. The placement of plectorthoideans in the same major clade as linoporellids, and the separation of dalmanellidines as an independent clade are the more important features of all shortest trees, supporting the idea that linoporellids may originate from a plectorthoid ancestor. Cladistic analysis reveals that Lipanorthis lies close to the ancestry of the linoporellid lineage, and Famatinorthis cluster within the more derived taxa of the clade to which shares a large septalium. It seems that presence of endopunctae in the orthides does not necessarily indicate close phylogenetic relationships as it could have occurred at different times in different clades. If the homoplasic nature of endopunctae in the order Orthida is supported by further morphologic and phylogenetic studies, then the fundamental division of orthides in non-punctate (Orthidina) and punctate (Dalmanellidina) may need revision.