New species of Isisfordia from the Upper Cretaceous (Cenomanian) of Lightning Ridge, NSW

24 June 2019

A new species of the Cretaceous crocodilian genus Isisfordia has been described from opalised fossils found at Lightning Ridge in NSW, Australia.  Another fossil found more than a century ago, also from Lightning Ridge, has also been assigned to Isisfordia.

Dating back to 96–100 million years ago, the new species Isisfordia molnari is one of the oldest known direct ancestors of today’s living crocodylians. The species was named after Dr Ralph Molnar, a palaeontologist whose many valuable contributions to Australian science include research on fossil crocodiles. This is the second species of Isisfordia discovered, with Isisfordia duncani named in 2006 from fossils found near the Queensland outback town of IsisfordA partial upper jaw, also from Lightning Ridge, and previously known as Crocodilus (Bottosaurus) selaslophensis, has been assigned to Isisfordia selaslophensis

Isisfordia molnari fossils
Photos of the partial braincase (left) of the new crocodile species, Isisfordia molnari, alongside the upper jaw (right) of Isisfordia selaslophensis, both from Lightning Ridge, NSW. (Not to scale). Photographs by Lachlan Hart.

Both Isisfordia molnari and I. selaslophensis grew to between 1.5 and 2 metres in length and is thought to have been semi-aquatic ambush predators, similar to modern crocodiles, alligators and caimans. But unlike today's crocs, their prey probably included small dinosaurs such as Weewarrasaurus pobeni .

Lead researcher Lachlan Hart, a Master of Science student at the University of New England in Armidale, explained how new crocs were discovered.

“The first crocodile fossil from Lightning Ridge, a partial jaw bone with teeth, was discovered in 1917, at a time when little was known about fossil crocodiles from the Australia's age of dinosaurs. It found its way to the Australian Museum and was given a name that turned out to be incorrect. Then in the early 2000s, opal buyers Peter and Lisa Carroll found a piece of fossil crocodile braincase (the rear section of the skull) from Lightning Ridge and sold it to the Australian Museum; but still there were so few Australian crocodile fossils known of this age, scientists also found this new piece difficult to interpret.

“After Isisfordia duncani was discovered in Queensland in 2006, it allowed us to make more sense of the earlier Lightning Ridge discoveries. Although they were similar, we found several differences which set the Lightning Ridge species apart.”

parts of Isisfordia molnari
The skull of Isisfordia duncani (from Salisbury et al. 2006), shown from above and underneath, highlighting the location of the fossils known for Isisfordia molnari (left) and Isisfordia selaslophensis (right).

Like other fossils from Lightning Ridge, the Isisfordia molnari and I. selaslophensis fossils are opalised, meaning that the original bone and tooth material has been replaced by opal. Other famous opalised fossils from Lightning Ridge include those of the recently-announced herbivorous dinosaurs Fostoria dhimbangunmal and Weewarrasaurus pobeni, fossils of which are at the Australian Opal Centre, a public museum that earlier in 2019 secured $20 million to construct a new building at Lightning Ridge for its world-leading collections and programs.

"Lightning Ridge is one of the most important fossil sites in Australia," said Australian Opal Centre palaeontologist and Special Projects Officer Jenni Brammall. "This new research is adding to a complex and intriguing picture not only of the dinosaurs of the time, but the animals and plants they lived with and the ecosystems they were part of."

The new crocodile species were published in the journal PeerJ, by scientists from the University of New England, Australian Opal Centre and The University of Queensland's Dinosaur Lab.

In brief:

  • A new species of extinct crocodile, Isisfordia molnari, has been described from fossils discovered at the outback town of Lightning Ridge.
  • Material previously known as Crocodilus (Bottosaurus) selaslophensis has been reassigned to Isisfordia selaslophensis
  • The fossils, a partial braincase and partial upper jawbone, come from the Cretaceous period about 100 million years ago.
  • Both Isisfordia molnari and I. selaslophensis grew to between 1.5 – 2 metres in length and were probably semi-aquatic ambush predators, preying on small dinosaurs and other animals.
  • The 'new' species were identified from fossils discovered respectively 20 and 100 years ago, thanks to recent advances in knowledge about fossil crocodiles in Australia.
Artist’s reconstruction of Isisfordia molnari. Image by Josè Vitor Silva.

Media contact: Lachlan Hart,, 0402 170 301;  Jenni Brammall,, 0427 904 587

Hart, L.J., Bell, P.R., Smith, E.T. and Salisbury, S.W. 2019. Isisfordia molnari sp. nov., a new basal eusuchian from the mid-Cretaceous of Lightning Ridge, Australia. PeerJ. 7:e7166

Hart, L.J. 2020. Taxonomnic clarification concerning the crocodyliform genus Isisfordia. Peer J. 8:e8630.