PALEOZOIC SARCOPTERYGIANS OF ARGENTINA: SCALES AND BONES FROM THE CARBONIFEROUS-PERMIAN OF SAN JUAN AND CHUBUT PROVINCES

GOUIRIC-CAVALLI, SOLEDAD; CONDE, OSVALDO; CORREA, GUSTAVO ALEJANDRO; SUSANA DAMBORENEA; MIGUEL O. MANCEÑIDO; ALEJANDRA PAGANI; BALARINO, M. LUCÍA

Jornada; XXXV Jornadas Argentinas de Paleontología de Vertebrados; 2022

The Paleozoic sarcopterygian fossil record in South America is represented mainly by isolated scales retrieved from the Permian of Bolivia, Brazil, and Uruguay, being the oldest records those of the Late Carboniferous of Brazil consisting of isolated and incomplete scales. Hence, any new finding of Paleozoic sarcopterygians in South America is relevant to the understanding of ancient ichthyofaunas diversity and ecosystems. Here we report material from the Carboniferous?Permian of the Del Salto, Tres Saltos and/or Pituil formations, San Juan Province, and Pampa de Tepuel and Mojón de Hierro formations in Chubut Province, Argentina. Part of the specimens ?those from San Juan Province? were previously reported but never studied in detail. The reported material is relatively well-preserved and consists mainly of isolated completely preserved scales and a few isolated and unidentified dermal bones. Scale morphologies vary from rounded to ovoid; most have the exposed (posterior) field ornamented with several closely packed and elongated coarse ridges that seem to be coated with enamel, occasionally coarse tubercles are also present. The unexposed (anterior) field bears parallel and concentric growth lines. Scale sizes vary ca. 1 to 2.5 cm in length. The ornamentation pattern observed on the scales is consistent with those present in many coelacanths ??which is uniformly maintained from the Paleozoic to Recent. Thus, the scale material is interpreted as belonging to coelacanth (Sarcopterygii, Actinistia) fishes. Early coelacanth material is rare in South America and generally poorly preserved; thus, scale descriptions of many Paleozoic South American taxa seem to be incomplete, dealing mostly with external morphology and most of the studied specimens lack paleohistological information. The material found in Argentina would provide an additional source for comparative paleohistological studies. Through this study, we report a broader distribution of coelacanths involving the centro-western and southwestern of Argentina. The material reported is among the oldest actinistians from South America. Detailed anatomical and paleohistological studies of the material are necessary to improve description, further comparisons and its paleobiogeographical implications.