Three dimensional angel shark jaw elements (Elasmobranchii, Squatinidae) from the Miocene of Southern Argentina

Abstract

Endoskeletal fossil remains of sharks are rare due to its cartilaginous nature. Great part of the skeleton is tessellated cartilage, comprised of a cortex of mineralized blocks called tesserae, lying just beneath the fibrous perichondrium and overlying a core of unmineralized extracellular matrix. The preservation of cartilage is not very common, particular conditions are needed. The most common elements found in the fossil record are teeth; scales and vertebrae, because they are more resistant to taphonomic processes than others. In this contribution, we report an elasmobranch fossil jaw found in Late Miocene strata of the Puerto Madryn Formation, cropping out near the city of Puerto Madryn (65°06?W, 42°46?S). The material consists of a right incomplete palatoquadrate and a right fragmentary Meckel's cartilage. In both, the central core is completely filled by a sandy matrix and the tessellated tissue is very well preserved, indicating minimal transportation and rapid burial. The general morphology and the presence of a small and triangular dorsal process in the palatoquadrate, allow us to assign it to the genus Squatina Dumeril. Although teeth of Squatina sp. have already been recorded from Puerto Madryn Formation as well as in the Late Miocene Paraná Formation, this finding represents the first record of endoskeletal fossil remains of elasmobranchs from the Cenozoic of Argentina.