A new genus of Triassic actinopterygian with an evaluation of deepened flank scales in fusiform fossil fishes

Abstract

ABSTRACT Revision of the genus Peltoperleidus leads to recognition of a single persisting deepened scale row as the main diagnostic feature for the newly established genus Allisolepis gen. nov. The counts of deepened scale rows are taken to be very consistent in all species assigned to Peltoperleidus and Allisolepis gen. nov., since they can be perfectly matched with skull bone patterns and counts of lepidotrichia. An initial evaluation shows that presence and array of variably deepened flank scales in fusiform fossil fishes have previously been underestimated in terms of their occurrence and as a putatively phylogenetic signal: the counts of deepened flank scales show some negative correlation with body size in fusiform fishes up to a certain standard length only, and occur predominantly in smallest fishes in the Middle Triassic. No significant correlation exists between scale row counts and standard length with respect to taxonomy; although interrelationships of these actinopterygians are still poorly understood, it appears likely that similar patterns of deepened scale rows may have developed independently during the Early-Middle Triassic.