Researchers first discovered fossils of a giant predator on the island over a decade ago. At the time, scientists believed they had discovered a large predator from the Jurassic period and they named the creature Razanandrongobe sakalavae, meaning “giant lizard ancestor from Sakalava region.”
However, while scientists knew they had discovered a new, ancient predatory species, where it sat in the evolutionary tree of life remained unclear—it shared features of crocodylomorphs, a group that includes crocodilians and their extinct relatives, and theropods, the group of dinosaurs to which T-Rex belongs.
Now, scientists from France and Italy have re-examined the fossils, along with five cranial fragments that were found at the same site, which they “tentatively” refer to as coming from the same taxon.
Their findings, published in the journal PeerJ, place the fossils in the suborder Notosuchia. These crocodylomorphs lived during the Cretaceous period and researchers have found fossils in Africa, Asia, Europe and South America.
However, scientists believed Notosuchia’s evolutionary lineage started far earlier, during the Middle Jurassic, between 174 to 163 million years ago. But because there was no fossil evidence of it, it was known as a ghost lineage.
Cristiano Dal Sasso, from the Natural History Museum of Milan, Italy, and colleagues have now placed R. sakalavae in the Nortosuchia family tree, calling it the oldest and potentially largest of the suborder ever discovered. It predates other Nortosuchias by 42 million years.
While the scientists are tentative in estimating its exact size due to limited fossil evidence, they say it was likely bigger than Sarcosuchus imperator, which could reach up to 39ft in length, and Purussaurus brasilensis, which was around 34ft long.
“Like these and other gigantic crocs from the Cretaceous, ‘Razana’ could outcompete even theropod dinosaurs, at the top of the food chain”, Dal Sasso said in a statement.
The team says the size of R. sakalavae’s teeth indicate it fed on hard tissues, such as bone, and that it would have been one of the top land predators in the area at the time—the point at which Madagascar began to separate from the supercontinent Gondwana.
Study co-author Simone Maganuco said: “Its geographic position during the period when Madagascar was separating from other landmasses is strongly suggestive of an endemic lineage. At the same time, it represents a further signal that the Notosuchia originated in southern Gondwana.”
Concluding, the team writes that their analysis shows R. sakalavae is a “valid species well-distinct from any other currently known member of Notosuchia.”
“It contributes to filling in a gap in the group’s evolution, which contains a long ghost lineage in the Jurassic,” they continue. “It documents a dramatic, somewhat unexpected, size increase in the early history of the group.”