{"id":87137,"date":"2023-11-20T15:05:12","date_gmt":"2023-11-20T20:05:12","guid":{"rendered":"https:\/\/naturalsciences.org\/calendar\/?post_type=news&p=87137"},"modified":"2023-11-20T15:20:55","modified_gmt":"2023-11-20T20:20:55","slug":"triassic-archosaur-had-armored-plates-above-its-backbone","status":"publish","type":"news","link":"https:\/\/naturalsciences.org\/calendar\/news\/triassic-archosaur-had-armored-plates-above-its-backbone\/","title":{"rendered":"Armored archosaur discovery reveals complexity of dinosaur origins"},"content":{"rendered":"

Original news story published August 3, 2023. Updated November 20, 2023.<\/em><\/p>\n

\"IllustrationIllustration of Mambachiton fiandohana<\/em> as it may have looked in life, showing the characteristic paired scutes along its back. Art by Matt Celeskey.<\/span><\/p>\n

A team of American and Malagasy researchers, including NCMNS Research Curator of Paleontology Dr. Christian Kammerer<\/strong>, have discovered a new species of prehistoric reptile that provides important information on the early history of the dinosaur lineage. The new species, Mambachiton fiandohana<\/em>, was discovered during fieldwork in the Morondava Basin in southwestern Madagascar. It dates back to the Triassic Period, roughly 235 million years ago. Mambachiton<\/em> would have been a long-necked, quadrupedal animal, and is estimated to have been 4\u20136 feet (1.5\u20132 meters) long and weighed between 25\u201345 pounds (10\u201320 kilograms).<\/p>\n

\"SilhouetteSilhouette reconstruction of Mambachiton fiandohana<\/em>, showing the recovered bones of this species in blue (neck vertebrae-preserving armor) and pink.<\/span><\/p>\n

The most interesting aspect of this new species is the presence of bony armor plates, called osteoderms or scutes, atop its vertebrae. Although armor is known in a variety of dinosaurs, it is usually considered a relatively late innovation in dinosaur evolution, first appearing in the Jurassic Period. Previously, all known specimens of Triassic dinosaurs and their close relatives were unarmored, a feature distinguishing them from their distant living relatives the crocodiles. Mambachiton<\/em> shows that the common ancestor of both dinosaurs (including birds) and crocodiles was armored, and that the presence of armor had a complex evolutionary history in the larger dinosaur-crocodile lineage (called archosaurs). Ancestrally present in animals like Mambachiton<\/em>, it was lost for most of early dinosaur history, then re-appeared independently in some later dinosaur groups.<\/p>\n

\u201cThe loss and re-evolution of armor is an important aspect of the story of dinosaur evolution\u2014freeing them from some of the biomechanical body constraints of ancestral archosaurs and potentially contributing to some of the locomotor shifts as dinosaurs diversified into a dizzying array of different ecologies and body forms,\u201d said Dr. Kammerer.<\/p>\n

\u201cMambachiton<\/em> demonstrates that retention of ancestral features or acquisition of new traits depend on interactions within the ecosystem,\u201d said project co-leader Dr. Lovasoa Ranivoharimanana of the University of Antananarivo in Madagascar. \u201cWhen a character is essential, it is retained, but when it is no longer useful, it disappears.\u201d<\/p>\n

Mambachiton<\/em> is the latest addition to an extremely rich fauna of Triassic animals from southwestern Madagascar. Other fossil species found at this locality include Kongonaphon<\/em>, a squirrel-sized, bipedal archosaur related to the flying pterosaurs, the beaked, plant-eating reptile Isalorhynchus<\/em>, and a variety of synapsids, the group including animals and their extinct relatives. \u201cFossils from Madagascar are very important for our understanding of what is happening globally during the Triassic\u201d, said Dr. Kammerer. \u201cMost fossils of this age come from South America, making it hard to tell if the observed faunas there are typical of the time period as a whole, or are unique to one region. Fieldwork in understudied regions with Triassic outcrops are vital to reconstructing the evolutionary history of a variety of animal groups\u2014dinosaurs, crocodiles, mammals\u2014around the time of their origination.\u201d<\/p>\n

Co-authors on the study included Sterling Nesbitt from Virginia Tech, Emily Patellos from the University of Southern California and Virginia Tech, John Flynn from the American Museum of Natural history, and Andr\u00e9 Wyss from the University of California, Santa Barbara.<\/p>\n

Funding or other support was provided in part by the National Geographic Society (grant #s 5957-97, 6271-98, and 7052-01); World Wide Fund for Nature\/World Wildlife Fund, Madagascar; the Division of Paleontology at the American Museum of Natural History; and the Field Museum of Natural History Meeker Family Fellowship. The joint Madagascar-U.S. paleontological exploration, research, and education program was supported by the Universit\u00e9 d\u2019Antananarivo, Minist\u00e8re de L\u2019En\u00e9rgie et des Mines, and ICTE\/MICET (Madagascar), and the American Museum of Natural History, Field Museum of Natural History, and University of California-Santa Barbara (U.S.).<\/p>\n

Link to paper: https:\/\/doi.org\/10.1093\/zoolinnean\/zlad038<\/a><\/p>\n

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