Paleontologists in Uruguay have discovered a large, poorly preserved and incomplete skull of an ancient aquatic reptile called a mesosaurus, along with some accompanying bones. These new specimens suggest gigantism exists in mature mesosaurs that reach more than twice the size of previously reported adult and typical specimens.
Mesosaurs are small to medium-sized aquatic or semi-aquatic amniotes that lived in Gondwana during the Early Permian Period. Image credit: Roman Yevseyev / Graciela Piñeiro.
mesosaurus A group of small aquatic reptiles that lived in South Africa and South America during the Permian Period, approximately 299 to 270 million years ago.
These creatures were the first known aquatic reptiles to return to aquatic life from apparently terrestrial ancestors.
“Mesosaurs are often described as small to medium-sized aquatic amniotes due to their elongated bodies and long tails that exceed the length of the rest of their bodies,” Graciela Pinheiro of the University of the Republic and colleagues. said.
“Additionally, their long-nosed skulls consist of very thin skulls with numerous needle-like marginal teeth.”
“Despite the fragility of some parts of the skull, mesosaur fossils are abundant in the Percarboniferous shales and silt deposits of Gondwana, including preserved bones with articulated skulls. This includes nearly complete skeletons in good condition, as well as partially preserved specimens that still have recognizable soft tissue.
“This exceptional preservation has led to the designation of the Mangrullo Formation in Uruguay and the Illati Formation in Brazil as part of the Conservat Lagerstätten of Gondwana,” they added.
“Furthermore, mesosaur fossils collected from these units include a variety of ontogenetic stages, from fetuses to juveniles to adults.”
“Thus, the ontogeny of mesoosaurs is well documented, with body length ranging from 10 to 12 centimeters (3.9 to 4.7 inches) in hatchlings to 80 to 90 centimeters (2.6 to 3 feet) in young adults. ”
“The average body length of the middle dragon is about 70 cm (2.3 feet),” the researchers said.
“Previous research suggested that mesosaurs were semi-aquatic amniotes, rather than fully aquatic amniotes.”
Mesosaurus ontogenetic cranial series documented from specimens discovered in the Conservato Lagerstätte, Mangrullo Formation, Uruguay. Scale bar – 1 cm. Image credit: Pinheiro others., doi: 10.3390/fossils3010001.
Dr. Pinheiro and his co-authors discovered and studied the largest known mesosaur fossil ever recorded.
The specimen includes two fragmentary skulls, a dorsal vertebrae, a tail fragment, an isolated rib, and several other bones.
They come from the regions of Picada de Cuero and El Baron. Mangrullo formation Located in northern Uruguay.
Paleontologists compared the new fossil to a larger sample of the same bone.
Mesosaurus tenuidens.
Mesosaurus tenuidens.
Their analysis revealed that the size of mesosaurs in the Mangrullo Formation exceeded the typical size distribution previously recorded. Mesosaurus tenuidens.
These individuals were four to five standard deviations larger than average, with skull lengths of 15 to 20 cm (5.9 to 7.9 inches) and total body sizes of 1.5 to 2.5 m (4.9 to 8.2 ft).
“To explore the importance of such large mesoosaurs in the Mangrullo Formation population, we considered the potential effects of Bergmann dominance,” the researchers said.
“This is a study of isolated populations of the same species or different taxa whose body size may have been affected by changes in temperature or food availability, such as competition for nutrients. Although this is an important paleogeographical principle, it does not explain the presence of such large creatures.'' Mesosaurian specimens from the Mangurlo Formation. ”
“We therefore conclude that the large body size variations observed in mesosaurs correspond to their ontogenetic stages and growth patterns,” the researchers said.
“The smaller body size previously recognized may represent a population dominated by early juveniles, subadults, and young adults, and may be due to normal carcass wasting of animals that died from a variety of causes. It may reflect a catastrophic mass mortality event that impedes the increase.”
“The bentonite layers and gypsum crystals found in the Mangrullo Formation are the result of occasional inflows of ash fall onto the lagoon resulting from increased tectonic activity associated with the Pangea Formation.”
“These volcanic events, combined with the gradual drought and associated desertification observed in the Irati-Whitehill Sea, are the main triggers that may explain the extinction of mesosaurs, at least in the Uruguayan region of the Paraná Basin. It is suggested that
of findings Published in a magazine fossil research.
of findings Published in a magazine fossil research.
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Graciela Pinheiro others. 2025. Largest Mesosaurus Ever Known: Evidence from the Scanti Record. Phos. stud 3(1):1;doi: 10.3390/fossils3010001
Source: www.sci.news
