Sexual dimorphism in a new species of the actinopterygian Peltopleurus from the Triassic of northern Italy

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Abstract

The new species Peltopleurus nuptialis is described on the basis of several well preserved specimens from the uppermost Ladinian Kalkschieferzone of Ca’ del Frate. This new species is characterized by small size and the presence of hook-like fulcra on all fins except the caudal, and by tubercles on the rostral and nasal bones interpreted as secondary sexual traits. There is also a modified anal fin in supposed males, which probably acted as a gonopodium, pointing to a strong sexual dimorphism. A distinctive morphological variability seems to characterize peltopleurids: a comparison with groups of living fishes also showing morphological plasticity and sexual dimorphism is given in order to hypothesize similar behaviours and adaptations in the fossil forms.

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