The earliest stem edestoid (Eugeneodontiformes, Chondrichthyes) from the Viséan (lower Carboniferous) of Tula Region, Central Russia, and a revision of Edestoidea

A new edestoidean chondrichthyan Tuyuria insolita Lebedev, gen. et sp. nov. is described based on tooth elements from the lower Carboniferous (Upper Viséan) of Central Russia. This taxon represents the earliest known member of the superfamily Edestoidei (Eugeneodontiformes, Chondrichthyes). Analysis of external morphology and internal microstructure reveals a suite of features that likely characterize early edestoideans and their precursors. A new family Lestrodontidae Lebedev fam. nov. is established to accommodate Tuyuria Lebedev, gen. nov. Morphological and microCT studies of T uyuria insolita gen. et sp. nov. identify several features unusual for edestoideans. In addition to the typical embracement of successive elements by base processes, the basolingual point of the crown forms an additional point of contact with the labial buttress of the adjacent tooth. Lateral crown processes are absent, the labial canal opens beneath the labial buttress and communicates with the pulp cavity; numerous transverse vascular canals permeate the tooth base. The tooth crowns of Tuyuria insolita gen. et sp. nov. exhibit pronounced lifetime wear facets, atypical among Eugeneodontiformes. These facets suggest either scissor-type shearing between opposing tooth whorls or positioning within the parasymphyseal tooth series. Tooth crown features suggest adaptation for processing hard-shelled prey, such as crustaceans.