{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,8]],"date-time":"2026-10-08T07:20:56Z","timestamp":1791444056624,"version":"4.3.3"},"reference-count":52,"publisher":"PeerJ","license":[{"start":{"date-parts":[[2022,9,16]],"date-time":"2022-09-16T00:00:00Z","timestamp":1663286400000},"content-version":"unspecified","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001659","name":"German Research Foundation","doi-asserted-by":"crossref","award":["DFG FR 2457\/6-1"],"award-info":[{"award-number":["DFG FR 2457\/6-1"]}],"id":[{"id":"10.13039\/501100001659","id-type":"DOI","asserted-by":"crossref"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"abstract":"<jats:p>\n                    Mesosaurs are the first secondarily aquatic amniotes and one of the most enigmatic clades of reptiles from the early Permian. They have long puzzled paleontologists with their unique morphologies: possessing an elongated skull with thin needle-like teeth, a long neck, large webbed hindlimbs, banana-shaped pachyosteosclerotic ribs, and a long tail. Here, we look at a large dataset of morphometric measurements from 270 mesosaur specimens in collections around the world. These measurements characterize skull, tooth, and limb proportions and their variation with size. This data presents evidence of surprising ontogenetic changes in these animals as well as new insights into their taxonomy. Our results support the recent hypothesis that\n                    <jats:italic>Mesosaurus tenuidens<\/jats:italic>\n                    is the only valid species within Mesosauridae and suggest that \u201c\n                    <jats:italic>Stereosternum tumidum<\/jats:italic>\n                    \u201d and \u201c\n                    <jats:italic>Brazilosaurus sanpauloensis<\/jats:italic>\n                    \u201d represent immature stages or incomplete specimens of\n                    <jats:italic>Mesosaurus<\/jats:italic>\n                    by showing that all three species occupy an incomplete portion of the overall size range of mesosaurs. Under the single-species hypothesis, we highlight a number of ontogenetic trends: (1) a reduction in skull length accompanied by an elongation of the snout within the skull, (2) an elongation of teeth, (3) a reduction in hind limb length, and (4) a reduction in manus length. Concurrent with these changes, we hypothesize that mesosaurs went through a progressive ecological shift during their growth, with juveniles being more common in shallow water deposits, whereas large adults are more frequent in pelagic sediments. These parallel changes suggest that mesosaurs underwent a diet and lifestyle transition during ontogeny, from an active predatory lifestyle as juveniles to a more filter-feeding diet as adults. We propose that this change in lifestyle and environments may have been driven by the pursuit of different food sources, but a better understanding of the Irati Sea fauna will be necessary to obtain a more definitive answer to the question of young mesosaur diet.\n                  <\/jats:p>","DOI":"10.7717\/peerj.13866","type":"journal-article","created":{"date-parts":[[2022,9,16]],"date-time":"2022-09-16T05:32:36Z","timestamp":1663306356000},"page":"e13866","source":"Crossref","is-referenced-by-count":4,"title":["Ontogenetic, dietary, and environmental shifts in Mesosauridae"],"prefix":"10.7717","volume":"10","author":[{"given":"Antoine","family":"Verri\u00e8re","sequence":"first","affiliation":[{"name":"Museum f\u00fcr Naturkunde, Leibniz-Institut f\u00fcr Evolutions- und Biodiversit\u00e4tsforschung und Institut f\u00fcr Biologie, Berlin, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"J\u00f6rg","family":"Fr\u00f6bisch","sequence":"additional","affiliation":[{"name":"Museum f\u00fcr Naturkunde, Leibniz-Institut f\u00fcr Evolutions- und Biodiversit\u00e4tsforschung und Institut f\u00fcr Biologie, Berlin, Germany"},{"name":"Institut f\u00fcr Biologie, Humboldt-Universit\u00e4t zu Berlin, Berlin, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"4443","published-online":{"date-parts":[[2022,9,16]]},"reference":[{"key":"10.7717\/peerj.13866\/ref-1","first-page":"91","article-title":"Taxonomia e rela\u00e7\u00f5es dos proganosauria da bacia do paran\u00e1","volume":"48","author":"Ara\u00fajo","year":"1976","journal-title":"Anais da Academia Brasileira de Ci\u00eancias"},{"key":"10.7717\/peerj.13866\/ref-2","doi-asserted-by":"publisher","first-page":"303","DOI":"10.3354\/meps07440","article-title":"Ontogenetic changes in diet and habitat use in green sea turtle (Chelonia mydas) life history","volume":"362","author":"Arthur","year":"2008","journal-title":"Marine Ecology Progress Series"},{"key":"10.7717\/peerj.13866\/ref-3","doi-asserted-by":"publisher","first-page":"110103","DOI":"10.1016\/j.palaeo.2020.110103","article-title":"The birth and demise of the vast epicontinental Permian Irati-Whitehill sea: evidence from organic geochemistry, geochronology, and paleogeography","volume":"562","author":"Bastos","year":"2021","journal-title":"Palaeogeography, Palaeoclimatology, Palaeoecology"},{"key":"10.7717\/peerj.13866\/ref-4","doi-asserted-by":"publisher","first-page":"109","DOI":"10.5194\/fr-21-109-2018","article-title":"A case study of developmental palaeontology in Stereosternum tumidum (Mesosauridae, Parareptilia)","volume":"21","author":"Bickelmann","year":"2018","journal-title":"Fossil Record"},{"key":"10.7717\/peerj.13866\/ref-5","doi-asserted-by":"crossref","first-page":"307","DOI":"10.1127\/njgpa\/169\/1985\/307","article-title":"A survey of aquatic locomotion in fishes and tetrapods","volume":"169","author":"Braun","year":"1985","journal-title":"Neues Jahrbuch f\u00fcr Geologie und Pal\u00e4ontologie, Abhandlungen"},{"key":"10.7717\/peerj.13866\/ref-6","doi-asserted-by":"publisher","first-page":"384","DOI":"10.1111\/j.1095-8312.2010.01431.x","article-title":"Evolution of humeral microanatomy and lifestyle in amniotes, and some comments on palaeobiological inferences","volume":"100","author":"Canoville","year":"2010","journal-title":"Biological Journal of the Linnean Society"},{"key":"10.7717\/peerj.13866\/ref-7","volume-title":"Vertebrate paleontology and evolution","author":"Carroll","year":"1988"},{"key":"10.7717\/peerj.13866\/ref-8","doi-asserted-by":"publisher","first-page":"119","DOI":"10.1007\/s13358-013-0055-1","article-title":"The silty shale Taquaral Member of the early Permian Irati Formation (Paran\u00e1 Basin, Brazil). Paleontology and paleoenvironments","volume":"132","author":"Chahud","year":"2013","journal-title":"Swiss Journal of Palaeontology"},{"key":"10.7717\/peerj.13866\/ref-9","first-page":"1","article-title":"A contribution to the vertebrate paleontology of Brazil","volume":"23","author":"Cope","year":"1886","journal-title":"Proceedings of the American Philosophical Society"},{"key":"10.7717\/peerj.13866\/ref-10","doi-asserted-by":"publisher","first-page":"22","DOI":"10.3389\/fevo.2017.00022","article-title":"Mesosaurid swim traces","volume":"5","author":"Da Silva","year":"2017","journal-title":"Frontiers in Ecology and Evolution"},{"key":"10.7717\/peerj.13866\/ref-11","first-page":"171","article-title":"Recherches pal\u00e9ohistologiques sur les os longs des t\u00e9trapodes V. 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Core Team","year":"2021"},{"key":"10.7717\/peerj.13866\/ref-40","article-title":"La dieta de los Mesosauridae (Amniota: Proganosauria) del P\u00e9rmico temprano de Uruguay","author":"Ramos","year":"2015","journal-title":"BS Thesis Thesis"},{"key":"10.7717\/peerj.13866\/ref-41","first-page":"13","article-title":"Studien an Mesosauriern (Amniota inc. sed.: Mesosauridae): 2. Neue Erkenntnisse zur Anatomie, mit Ber\u00fccksichtigung der Taxonomie von Mesosaurus pleurogaster (Seeley)","volume-title":"Advances in vertebrate palaeontology","author":"Rossmann","year":"2000"},{"key":"10.7717\/peerj.13866\/ref-42","doi-asserted-by":"publisher","first-page":"197","DOI":"10.1127\/njgpa\/224\/2002\/197","article-title":"Studien an Mesosauriern (Amniota inc. sed., Mesosauridae): 3. 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