First fossil occurrence of the bryozoan genus Burdwoodipora (Early Miocene, Argentine Patagonia)

PÉREZ, L.M.; LÓPEZ GAPPA, J.

Otro; 1ª Reunión Virtual de Comunicaciones de la Asociación Paleontológica Argentina; 2020

Asociación Paleontológica Argentina

The cheilostome genus Burdwoodipora was recently erected to accommodate its type species, B. paguricola, an obligate symbiont of gastropod shells occupied by the hermit crab Pagurus comptus. B. paguricola, currently the only species in this genus, is distributed in the Burdwood Bank, the Patagonian shelf, and around Tierra del Fuego, between 28 and 199 m deep. The aim of this study is to report the finding of a second species of Burdwoodipora in the Monte León Formation (early Miocene, Santa Cruz Province), also associated with pagurized gastropod shells. it shares with B. paguricola the presence of a frontal shield uniformly perforated by pseudopores, basal walls with characteristic uncalcified areas, and a peculiar cleithridiate orifice with a pair of robust condyles and a proximal arrow-shaped sinus. The main difference between both species is the location of the adventitious avicularia, which are only latero-oral in the Miocene fossil, instead of being usually proximal to the orifice and mounted on a huge umbo as in B. paguricola. ovicells and ancestrula were absent in the analyzed fossil fragments. The presence of another species of Burdwoodipora in the Monte León Formation increases the known bryozoan biodiversity of this unit and completes the geographic distribution of the genus between its northernmost and southernmost records in Patagonia. The appearance of this new species in a neogene formation confirms the presence of Burdwoodipora in the southern Southwest Atlantic since the early Miocene.