April 11, 2016

Titanosaurs, some of history’s largest creatures, may have split off into subspecies when their supercontinent broke apart, according to new research from Ohio University.

The study, conducted by Eric Gorscak and Patrick O’Connor, used recently developed mapping techniques to create a timeline of a species’ genetic history. The pair used this modelling to estimate when titanosaurs roamed the Earth, and why their descendants may have evolved from the family line to form new species.

Titanosaurs, a group of particularly large sauropod dinosaurs, were widespread across the globe during their heyday, before their extinction along with the rest of the dinosaurs 65 million years ago. These long-necked giants account for some of the largest creatures to have ever walked the Earth, some reaching lengths of 40 metres and weighing in at a portly 90,000 kilograms.

The study’s time models place the origins of titanosaurs in South America during the Early Cretaceous, some 135 million years ago.

The researchers observed a rough link between the evolutionary divergence of titanosaur species and the separation of the southerly supercontinent Gondwana during the Cretaceous period.

This mirroring also reflects the various geophysical changes that followed the split, such as the emergence of land bridges.

“Our models estimate that the global distribution of titanosaurians […] follows geophysical patterns of continental separation and isolation throughout the Cretaceous,” the paper reads.

The findings also point to a semi-isolated group of African subspecies that became unique to their area below the equator.

“Recovered divergence dates for South American and African titanosaurian sister lineages follow the gradual northward ‘unzipping’ of these two continents and may have promoted the semi-isolation of subequatorial African faunas,” the paper states.

Gondwana's final separation is estimated at 100 million years ago, creating the distinct continents of Africa, South America, Australia and Antarctica we see today.

This paper was published in Biology Letters.

Amy Middleton is a Melbourne-based journalist.