New fossils from the Devonian of Peru shed light on the unusual “dental” structure of the stem chondrichthyan Pucapampella

Pucapampella represents an enigmatic genus of non-acanthodian stem chondrichthyans known from the Lower to Middle Devonian (Emsian–Eifelian) of South America, particularly from Bolivia and Peru. Pucapampellids display a mosaic of primitive and derived traits. One of the most distinctive features concerns the structure of the dentition, which is unusual compared to other chondrichthyans. They possess “teeth” that are neither arranged into replacement tooth families (as in most crown chondrichthyans) nor part of dentigerous jaw bones or tooth whorls (as in acanthodians). Instead, their mandibular arches have been described as bearing a single series of sharp “teeth” supported directly by cartilage, without any intervening dermal bone. Paleontological fieldwork conducted in recent years in Devonian strata of the Puno region (southwestern Peru), near Lake Titicaca at an altitude of about 4,200 meters above sea level, has yielded a rich assemblage of new pucapampellid fossils, including exceptionally preserved mandibular remains. These specimens are preserved within phosphatic nodules embedded in grey shales from the upper part of the Chagrapi Formation, which records cyclic successions of dark and grey shales with fine sandstones deposited in a delta-influenced infralittoral marine setting. The upper member, rich in organic matter and phosphatic nodules, indicates episodes of deepening and anoxic conditions. Pucapampellid remains occur in Eifelian-aged levels containing a more diverse vertebrate fauna. Specimens were analyzed using synchrotron PPC-SRµCT, synchrotron μXRF elemental mapping, and paleohistological thin sections. Preliminary results reveal a unique dental architecture unlike any previously described in vertebrates. These findings suggest that the dental structures of pucapampellids represent tooth-like elements that are not homologous to the “true” teeth of other gnathostomes.

Abstract of an Oral Presentation or a Poster