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

24 June 2019

A new species of crocodilian has been described from opalised fossils found at Lightning Ridge in NSW, Australia.  One of the fossils was found more than a century ago and the second 70 years later.

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 Isisford.

Isisfordia molnari fossils
Photos of the partial braincase (top view) and jawbone of the new crocodile species, Isisfordia molnari, from Lightning Ridge, NSW. (Not to scale). Photographs by Lachlan Hart.

Isisfordia molnari grew to between 1.5 and 2 metres in length and is thought to have been a semi-aquatic ambush predator, similar to modern crocodiles, alligators and caimans. But unlike today's crocs, its 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 the new species was 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

Like other fossils from Lightning Ridge, the Isisfordia molnari 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 was 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.
  • The fossils, a partial braincase and partial upper jawbone, come from the Cretaceous period about 100 million years ago.
  • Isisfordia molnari grew to between 1.5 – 2 metres in length and was probably a semi-aquatic ambush predator, preying on small dinosaurs and other animals.
  • The new species was 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, lhart7@une.edu.au, 0402 170 301;  Jenni Brammall, jbrammall@australianopalcentre.com, 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

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