A new neopterygian fish from the Late Jurassic Ameghino (=Nordenskjöld) Formation

ARI IGLESIAS; MARCELO REGUERO; GOURIC-CAVALLI SOLEDAD; BIGURRARENA OJEDA, M.A.; BÁRBARA CARIGLINO

Tasmania

Congreso; SCAR, Scientific Committee on Antarctic Research 'Antarctic Science - Global Connections'. Tasmania; 2020

SCAR, Scientific Committee on Antarctic Research 'Antarctic Science - Global Connections'. Tasmania

A new Jurassic neopterygian fish is presented on the basis of an almost complete specimen from the early Tithonian (Late Jurassic) Ameghino (=Nordenskjöld) Formation in the Argentine Antarctic Sector (Antarctic Peninsula). The specimen was recovered during the 2019/2020 Antarctic Summer field. Analysis of the new material suggests this is a new species of Dapediiformes ?deep-bodied neopterygian fishes?. Dapediids as a whole are yet poorly sampled in formal phylogenetic analyses but to date, they are considered as stemholostean fishes or the sister group of ginglymodians [Semionotiformes + Lepisosteiformes]. Moreover, the establishment of apomorphic characters for the members of the group is difficult. The specimen presented herein shares some similarities with the genus Dapedium (e.g., ellipsoidal to circular body outline, a seamlike dorsal fin, pectoral fin placed high in the body, roughly rectangular scales with a smooth caudal margin, skull bones heavily ornamented with tubercles). Besides its importance as the first Dapediiformes described from Gondwana continents, this specimen adds information relative to the anatomy of this fish group, their diversity, ecology, and paleobiogeography. Furthermore, the study of this fossil will increase the understanding of dapediids anatomy and phylogenetic relationships among neopterygians.