New goniopholidid specimens from the Lower Cretaceous Kitadani Formation, Tetori Group, Japan

Abstract

New crocodyliform fossils have been discovered from the Lower Cretaceous Kitadani Formation of the Tetori Group, Fukui, Japan. They include skull elements (premaxilla, maxilla, parietal, quadrate and dentary), postcranium elements (dorsal vertebra, caudal vertebra, femur and osteoderm) and isolated teeth, and are described as goniopholidid crocodyliforms. Phylogenetic analysis resulted in nesting the Kitadani goniopholidid at the basal position of Goniopholididae and one autapomorphy is recognized: presence of the parietal sagittal crest. In addition, the narrow snout and a heterodont dentition in jaws of this goniopholidid is a unique combination of rostral morphology among Goniopholididae. Generally, the basal taxa bear a narrow snout with homodont dentition, and the heterodont dentition is seen in derived broad-snouted taxa. Judging from those rostral shape and dentitions, the Kitadani form possessing acute caniniform and blunt teeth tends to be more opportunistic as foraging strategy than other basal narrow-snouted goniopholidids with only acute caniniforms throughout. Our new discovery is the first osteological report of Japanese Cretaceous crocodyliform. Siamosuchus phuphokensis from the Early Cretaceous Sao Khua Formation, Khorat Group also shows combination of basal and derived cranial characters. Transitional species from Asia suggest allopatric speciation of goniopholidid in geographically intermediate Asian area.