New three-metre croc described

These days, as a rule, new species discoveries aren’t news – in spite of the vast number of organisms still to be found and described.

Creatures unknown tend to be on the small side, and are often hard to find: think insects, small cryptic mammals, or Antarctic crustaceans.

So it’s cause for notice when someone turns up a new type of crocodile that grows to a difficult-to-disguise three metres in length.

The new croc, Crocodylus halli, is from southern Papua New Guinea (PNG), where it shares territory with Crocodylus porosus – the fearsome estuarine crocodile. This makes C. halli the second crocodile species unique to PNG, alongside the New Guinea crocodile, Crocodylus novaeguineae.

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A skull from Crocodylus halli. Credit: American Society of Ichthyologists and Herpetologists

C. novaeguineae was first described in 1928 but ever since researchers had wondered if the northern and southern populations were actually two separate species.

A University of Florida, USA, researcher named Philip Hall spent time in the 1980s investigating distinctions between the northern and southern populations, but he died before reaching a conclusion.

In 2014, Chris Murray, an Assistant Professor at Southeastern Louisiana University, and Field Museum, Illinois, scientist Caleb McMahan attended a talk that was essentially soliciting help to carry on Hall’s unfinished investigation.

Hall had noticed differences in the way the two groups of crocs nest and mate. His work caught the interest of McMahan and Murray, whose research focuses more on animals’ skeletal variations than behaviour.

The two understand that analysis of small details can reveal a big enough difference between animals to separate them as species.

“Chris does a lot of work on crocodilians, and I do a lot of evolutionary work, often with morphology, or the animals’ physical features,” says McMahan.

“Chris studies morphology too, so it was continuing along with a lot of the projects we were doing, but then lo and behold, it’s this brand new crocodile species

Murray and McMahan examined 51 PNG croc skulls – all believed at the outset to be C. novaeguineae – and analysed differences between those from PNG’s north and those from the south. The skulls were held in seven different museum collections, all in the US except for the Queensland Museum in Australia.

Murray notes that access to these collections “highlights the beauty of natural history museums”.

“We didn’t have to go to Papua New Guinea and collect a bunch of specimens, which would have been incredibly difficult anyhow, and very expensive.”

“There are new species out there but a lot of them are sitting in drawers and cabinets in museums, and it just takes time to look at them and figure that out,” adds McMahan.

The research team capped off their skull analysis with a visit to the St. Augustine Alligator Farm Zoological Park, in Florida. 

“They have live individuals of what’s called novaeguineae, and we were able to look at those and say, ‘Oh yeah, this matches the north and this matches the south!’ I thought that was super cool,” says McMahan.

The researchers were keen to honour Hall, the scientist who’d started the investigation, so the name Crocodylus halli came easily.

“I think it was really special for me in particular, I’ve been reading his work since the beginning of my career in academia, in my first year as a Master’s student, so to come full circle and help contribute to his work was meaningful,” says Murray.

“Being able to name the thing that he initially pondered after him was even more meaningful.”

The team notes that they were motivated by curiosity about new questions and methodology of research rather than the expectation of a new species discovery.

The description of C. halli has been published in the journal Copeia.

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