A new genus and species of Chaperiidae (Bryozoa: Cheilostomata) from the early Miocene of Patagonia (Argentina)

PÉREZ, LEANDRO M.; LÓPEZ-GAPPA, JUAN

AMEGHINIANA

ASOCIACION PALEONTOLOGICA ARGENTINA

Lugar: Buenos Aires; Año: 2019 vol. 56 p. 422 - 429

0002-7014

The family Chaperiidae reaches its highest biodiversityin the southern hemisphere. The main morphological feature characterizing thefamily is a pair of calcareous laminar structures associated with the insertionof the operculum occlusor muscles. The aim of this study is to describe Aluis spinettai gen. et sp. nov., from material collected in the MonteLeón, the Chenque and the Puesto del Museo formations (early Miocene,Patagonia, Argentina). A. spinettaihas erectbilaminar colonies, crenulated sutures between zooids, an extensive cryptocystand spherical ovicells; gymnocyst, oral spines and avicularia are absent. Thenew species exhibits a remarkable morphological convergence with a species of Aspidostoma from the early Miocene (Chenque Formation) of Patagonia.In some areas of the colony, the cryptocysts were pierced by circular drillholes made by an unknown predator. The stratigraphic distribution of A. spinettai ranges from ~19 to 17 Ma (Burdigalian). Its presence suggestsa correlation between the upper levels of the Monte León Formation and thelower levels of the Chenque Formation. The paleogeographic distribution of thisnew species spans at least 500 km along the southern Atlantic coast of South America.The living representatives of the Chaperiidae in the Southwest Atlantic do notseem related with A. spinettai.