A new crocodile displaying extreme constriction of the mandible, from the late Oligocene of Riversleigh, Australia

A new fossil crocodile, <i>Ultrastenos willisi</i>, is described from a cranium and postcranial materials collected from the Riversleigh World Heritage Area, northwestern Queensland, Australia. The mandible displays pronounced anterior constriction, approaching that seen in the extant gharial, <i>Gavialis gangeticus</i>, and false gharial, <i>Tomistoma schlegelii</i>. As such, <i>U. willisi</i> potentially filled the ecomorphological niche associated with longirostry that has been previously unaccounted for in Riversleigh's Oligo–Miocene crocodile fauna. The pronounced constriction and features of the posterior cranium further distinguish <i>U. willisi</i> from all other known crocodiles, including the only reported Australian Oligo–Miocene longirostral crocodile, <i>Harpacochampsa camfieldensis</i>, from Bullock Creek in the Northern Territory. <i>Ultrastenos willisi</i> is recognized as a new genus and species assigned to subfamily Mekosuchinae on the basis of phylogenetic analysis.http://zoobank.org/urn:lsid:zoobank.org:pub:7C6DC891-BD9C-4F84-AF7D-409A4A8C720D SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP Citation for this article: Stein, M., S. J. Hand, and M. Archer. 2016. A new crocodile displaying extreme constriction of the mandible, from the late Oligocene of Riversleigh, Australia. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2016.1179041.