(CNN)A unique species of crocodile lives in New Guinea, but in 1989, a researcher suspected that there may be more to the story on the tropical island.
Philip Hall, the University of Florida researcher investigating if the island's crocodiles belonged to two different species, died before he could finish his work.
Now, researchers have finished up the work that Hall began and their new study shows that he was right. Their study published Thursday in the journal Copeia.
The New Guinea Crocodile was discovered in 1928. But the large island north of Australia is divided by a mountain range, creating distinct habitats in the north and south. The researchers wondered how different the crocodiles might be in these environments.
In 2014, Chris Murray, assistant professor at Southeastern Louisiana University, and Caleb McMahan, a scientist at the Field Museum in Chicago, were at a conference discussing the differences in reptile skulls. They attended a talk that raised Hall's research and asked for help to finish the investigation distinguishing between the New Guinea crocodiles.
Hall's work had noted differences in the way the crocodiles nested and mated. McMahan and Murray were more focused on skeletal differences. Together, the information could paint a bigger picture that would differentiate between species.
"Philip Hall really provided the interesting baseline work on these crocodiles, especially for ecological data," McMahan said. "Our work adds to this with additional morphological insight into how distinctive these two species of crocodiles."
They analyzed 51 skulls belonging to the New Guinea Crocodile to look for differences between ones that lived in the north of the island versus the south. They studied specimens from seven different museum collections. Many of the skulls were 90 years old. And the crocodiles they belonged to could reach ten feet in length.