Mambachiton fiandohana lived in what is now Madagascar during the Middle-Late Triassic transition, around 235 million years ago — the time of the first appearance of dinosaurs.
Archosaurs are reptiles that are divided into two major branches: the bird-line, which includes pterosaurs and dinosaurs, including living dinosaurs (birds); and the crocodilian line, including crocodiles, alligators, caimans, and gharials.
Mambachiton fiandohana is the earliest diverging member of the bird line of archosaur evolution.
“We are just starting to understand that there were many dinosaur-like creatures across the planet well before dinosaurs evolved,” said Dr. Sterling Nesbitt, a paleontologist at Virginia Tech and the American Museum of Natural History.
“Dinosaurs were latecomers to the Triassic reptile party. They showed up well after many dinosaur-looking reptiles were established across our planet.”
The well-preserved postcranial remains of Mambachiton fiandohana were found in 1997 in the Isalo II/Makay Formation of Madagascar.
“This discovery documents the importance of the southern hemisphere fossil record in understanding this important period of the Triassic, when dinosaurs were first appearing,” said Dr. John Flynn, a paleontologist at the American Museum of Natural History.
Mambachiton fiandohana was between 1.5 and 2 m (5-6.6 feet) long and weighed 10 to 20 kg.
Unexpectedly, the species had an extensive series of bony plates called osteoderms covering its backbone.
Although osteoderms are common in crocodilians and their relatives, they are rare in bird-line archosaurs, with the exception of dinosaurs like stegosaurs, ankylosaurs, titanosaur sauropods, and at least one theropod.
Mambachiton fiandohana shows definitively that the bird-line archosaur group was ancestrally armored.
This armor was lost in the evolution of dinosaurs and pterosaurs but then re-appeared later several times, independently, in the dinosaur lineage.
“The loss and…
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