The northernmost occurrence of non-karaurid salamanders (Lissamphibia, Caudata) in the Mesozoic

Abstract

Isolated incompete salamander dentaries from the Lower Cretaceous Teete locality in Yakutia (Eastern Siberia, Russia) represent the northernmost occurrence of non-karaurid salamanders in the Mesozoic and are evidence that small-sized salamanders lived in high latitudes (paleolatitude estimate of N 62°–66.5°) in the Northern Hemisphere in the Early Cretaceous. These gracile and lightly built dentaries are characterized by the presence of numerous slender and closely spaced pedicellate teeth, a sharp ridge along the ventral edge of the postsymphyseal region, numerous neurovascular foramina that open into parallel longitudinal grooves on the labial surface, and a complex neurovascular system. The neurovascular system, which consists of a large longitudinal canal for the ramus mandibularis internus of the trigeminal nerve associated with smaller lateral canals and an entirely separate anterior part of the alveolar canal for the branches of the ramus alveolaris of the facial nerve, is similar to that of the long-lived Juro-Cretaceous small-sized non-karaurid salamanders of the genus Kiyatriton. The Teete faunal association “relic karaurid stem salamander—small-sized non-karaurid salamander” is characteristic for the “Great Siberian refugium” for Jurassic vertebrate relicts that covered the vast northeastern part of the Asiatic continent during the Early Cretaceous.