The oldest known aquatic reptiles, the mesosaurs, in all probability spent business office of their life on land, reveals a novel study published inwards Frontiers inwards Ecology in addition to Evolution. The fossilized bones of adult Mesosaurus portion similarities amongst land-dwelling animals, which - coupled amongst the relative scarcity of land-weathered fossilized remains of large specimens - suggests that older mesosaurs were semi-aquatic, whereas juveniles spent most of their fourth dimension inwards the water. This novel interrogation emphasizes the importance of thoroughly analyzing fossilized remains from across all stages of a reptile's life to larn a total appreciation of its lifestyle in addition to behavior.
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| Drawing of Mesosaurus [Credit: Roman Yevseyev & Graciela Piñeiro] |
Since the uncovering of unusually large Mesosaurus bones inwards the Mangrullo Formation of Uruguay, Piñeiro in addition to her international squad of colleagues wondered why the larger, presumably adult specimens, roughly 2 meters inwards length, were non equally abundant equally mesosaur skeletons of roughly ninety cm.
"The larger specimens, at to the lowest degree twice the length of the to a greater extent than commonly reported Mesosaurus fossils, could merely last exceptionally large individuals. However, the environmental conditions of the Mangrullo lagoon of where they lived were harsh, making it hard for the occasional mesosaur to achieve such a relatively large size in addition to age," explains Piñeiro.
She continues, "We in addition to thence realized that inwards comparing to the smaller, better-preserved specimens, larger Mesosaurus fossils were most ever disarticulated, real weathered in addition to badly preserved. This suggested these larger specimens had extended exposure to the air when they died."
During the reconstruction of a Mesosaurus skeleton in addition to analysis of skeletons representing dissimilar life stages of this ancient reptile, the researchers examined the remains for show of a terrestrial, land-dwelling existence.
Terrestrial, semi-aquatic in addition to aquatic animals demonstrate a clear deviation inwards os profiles, thence they used morphometrics to analyze the shape of the fossilized bones. Forty Mesosaurus specimens, from juveniles to adults, were examined in addition to their os profiles compared to those of like reptiles known to last aquatic or semi-aquatic, such equally crocodiles in addition to marine iguanas.
"The adult mesosaur tarsus (a cluster of bones inwards the talocrural articulation region) suggests a to a greater extent than terrestrial or amphibious locomotion rather than a fully aquatic guide equally widely suggested before," says Pablo Núñez, besides based at Universidad de la República. "Their caudal vertebrae, the tail bones, besides showed similarities to semi-aquatic in addition to terrestrial animals. This supports the hypothesis that the oldest in addition to largest mesosaurs spent to a greater extent than fourth dimension on land, where fossil preservation is non equally expert equally inwards the subaquatic domain."
Published equally business office of a special article collection on Mesosaurs, these findings accept broader implications - both for futurity interrogation on early on prehistoric animals that seat eggs amongst embryonic membranes in addition to for the agreement of reptile evolution.
Piñeiro explains, "Our study emphasizes the importance of working amongst fossils representing an entire population of a species, including a broad hit of juveniles in addition to adults, before establishing paleobiological interpretations on their lifestyle in addition to behavior."
She continues, "These findings besides accept of import implications on the inferred lifestyle of species closely related to mesosaurs, peculiarly inwards the context of the evolution of the amniotic egg. For instance, thank yous to our previous uncovering of a mesosaur egg in addition to embryos within the mother's body, our novel findings tin hit back upward to before hypotheses suggesting that the amniotic egg mightiness accept appeared inwards aquatic or semiaquatic animals equally a strategy to larn out the H2O to avoid predation."
Source: Frontiers [September 19, 2018]
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