Fossils of the world's most primitive modern crocodilian have been discovered near the outback town of Isisford, in central-western Queensland, Australia. Discovered by former Deputy Mayor of Isisford, Ian Duncan, after whom the new species has been named, the first fossils of Isisfordia were found in the mid-1990s in a dried-up creek bed on the outskirts of town.
Living 98-95 million years ago, Isisfordia predates the first recorded appearance of alligators and gharials by almost 20 million years, and the first true crocodiles by over 30 million.
An international team of palaeontologists, headed by Dr Steve Salisbury from The University of Queensland's (UQ) School of Integrative Biology Published a paper in the Proceedings of the Royal Society B (pdf).
While the crocodyliform lineage extends back over 200 million years (Myr) to the Late Triassic, modern forms—members of Eusuchia—do not appear until the Cretaceous. Eusuchia includes the crown group Crocodylia, which comprises Crocodyloidea, Alligatoroidea and Gavialoidea. Fossils of non-crocodylian eusuchians are currently rare and, in most instances, fragmentary. Consequently, the transition from Neosuchia to Crocodylia has been one of the most poorly understood areas of crocodyliform evolution. Here we describe a new crocodyliform from the mid-Cretaceous (98–95Myr ago; Albian–Cenomanian) Winton Formation of Queensland, Australia, as the most primitive member of Eusuchia. The anatomical changes associated with the emergence of this taxon indicate a pivotal shift in the feeding and locomotor behaviour of crocodyliforms—a shift that may be linked to the subsequent rapid diversification of Eusuchia 20Myr later during the Late Cretaceous and Early Tertiary. While Laurasia (in particular North America) is the most likely ancestral area for Crocodylia, the biogeographic events associated with the origin of Eusuchia are more complex. Although the fossil evidence is limited, it now seems likely that at least part of the early history of Eusuchia transpired in Gondwana.
Link to a pdf of the entire paper; Proceedings of the Royal Society B (pdf)
University of Queensland press release
View proof images of Isisfordia and stills from the field and lab work.