A new species of armored reptile that lived around the time of the earliest dinosaurs is discovered. This newly described archosaur fossil is adorned with bony plates along its backbone and offers intriguing insights into the evolution of armor in the dinosaur and pterosaur lineage.
While the group's ancestors were initially equipped with armor, this characteristic was lost over time, only to re-emerge independently in specialized dinosaurs like ankylosaurs and stegosaurs.
Newly Described Archosaur Species
The findings of the study, published in the Zoological Journal of the Linnean Society, shed light on the diverse array of dinosaur-like creatures that inhabited Earth prior to the rise of true dinosaurs.
Archosaurs, a group of reptiles, can be divided into two main branches: the bird-line, which includes pterosaurs and dinosaurs (including modern birds), and the crocodilian line, which encompasses crocodiles, alligators, caimans, and gharials.
Science Daily reported that scientists recently described a new archosaur species named Mambachiton fiandohana in the study, representing the earliest divergence in the bird-line of archosaur evolution.
The fossil, dating back approximately 235 million years, was unearthed in Madagascar back in 1997 by a team led by John Flynn, the Frick Curator of Fossil Mammals at the Museum, in close collaboration with researchers and students from the University of Antananarivo in Madagascar.
This discovery holds significant importance for understanding the Triassic period when dinosaurs first emerged, as the fossil record of this time interval is limited in other regions. The Madagascar-U.S. research and education partnership spanning a quarter-century has proven to be invaluable in advancing our knowledge of this critical period in Earth's history.
M. fiandohana, the newly described species, was a four-legged, long-tailed predecessor to dinosaurs and pterosaurs. It was estimated to be about 4-6 feet long and weighed between 25-45 pounds.
Surprisingly, the species possessed an extensive series of bony plates called osteoderms along its backbone. While osteoderms are common in crocodilians and their relatives, they are relatively rare among bird-line archosaurs, except for certain dinosaurs such as stegosaurs, ankylosaurs, titanosaur sauropods, and at least one theropod.
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Bird-Line Archosaur Ancestry Was Armored
Mambachiton's discovery confirms that the bird-line archosaur group originally possessed armor, Earth.com reported. However, during the evolution of dinosaurs and pterosaurs, this armor was lost. Interestingly, it re-emerged independently multiple times within the dinosaur lineage, indicating a fascinating pattern of armor's disappearance and reappearance.
Christian Kammerer, a former Gerstner Scholar at the Museum and a research curator in paleontology at the North Carolina Museum of Natural Sciences, emphasizes that the loss and subsequent re-evolution of armor played a crucial role in the story of dinosaur evolution.
This transformation freed dinosaurs from certain biomechanical constraints imposed by their ancestral archosaur features and might have contributed to the diverse locomotor adaptations seen as dinosaurs diversified into various ecological niches and body forms.
Lovasoa Ranivoharimanana from the University of Antananarivo, a co-leader of the project, explains that Mambachiton's findings highlight how the retention or acquisition of traits is influenced by interactions within the ecosystem. If a specific characteristic proves essential for survival, it will persist; but if it becomes less advantageous, it may gradually disappear over time.
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