Squamates (lizards and snakes) are highly successful modern vertebrates, with over 10 000 species. Squamates have a long history, dating back to at least 240 million years ago (Ma), and showing increasing species richness in the Late Cretaceous (84 Ma) and Early Palaeogene (66-55 Ma). We confirm that the major expansion of dietary functional morphology happened before these diversifications, in the mid-Cretaceous, 110-90 Ma. Until that time, squamates had relatively uniform tooth types, which then diversified substantially and ecomorphospace expanded to modern levels. This coincides with the Cretaceous Terrestrial Revolution, when angiosperms began to take over terrestrial ecosystems, providing new roles for plant-eating and pollinating insects, which were, in turn, new sources of food for herbivorous and insectivorous squamates. There was also an early Late Cretaceous (95-90 Ma) rise in jaw size disparity, driven by the diversification of marine squamates, particularly early mosasaurs. These events established modern levels of squamate feeding ecomorphology before the major steps in species diversification, confirming decoupling of diversity and disparity. In fact, squamate feeding ecomorphospace had been partially explored in the Late Jurassic and Early Cretaceous, and jaw innovation in Late Cretaceous squamates involved expansions at the extremes of morphospace.
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Cutting-edge analysis of prehistoric teeth sheds new light on the diets of lizards and snakes
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Sauropterygia was a diverse clade of secondary aquatic reptiles, which represented one of the most important vertebrate groups in the shallow marine communities during the Triassic. However, despite the long history of collection and examination of sauropterygian remains, previous studies have indicated that the fossil record of this group is incomplete, making the understanding of their palaeobiogeographic relations difficult. Here we describe new sauropterygian remains from the Middle Triassic (Ladinian) Templomhegy Dolomite Member (VillÃny, southern Hungary), which were unearthed during systematic fieldwork of previous years. Among several non-diagnostic sauropterygian remains, this material contains isolated bones belonging to Nothosaurus sp., Simosauridae indet. and a small-sized nothosaurid. The known faunal composition from VillÃny is similar to what was described from the Middle Triassic of the Germanic Basin and Bihor Mountains (northwestern Romania). Besides isolated elements, a probably associated skeleton of a small-sized eosauropterygian specimen of unknown affinities is also reported here. This locality widens our knowledge on Triassic sauropterygian distribution and provides new information about the previously not well-known Middle Triassic vertebrate fauna of the one-time southern Eurasian shelf region.
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Jordi Estefa, Paul Tafforeau, Alice M Clement, Jozef Klembara, Grzegorz NiedÅwiedzki, Camille Berruyer & Sophie Sanchez (2021)
New light shed on the early evolution of limb-bone growth plate and bone marrow.
eLife 10:e51581
DOI: 10.7554/eLife.51581
https://elifesciences.org/articles/51581
The production of blood cells (haematopoiesis) occurs in the limb bones of most tetrapods but is absent in the fin bones of ray-finned fish. When did long bones start producing blood cells? Recent hypotheses suggested that haematopoiesis migrated into long bones prior to the water-to-land transition and protected newly-produced blood cells from harsher environmental conditions. However, little fossil evidence to support these hypotheses has been provided so far. Observations of the humeral microarchitecture of stem-tetrapods, batrachians, and amniotes were performed using classical sectioning and three-dimensional synchrotron virtual histology. They show that Permian tetrapods seem to be among the first to exhibit a centralised marrow organisation, which allows haematopoiesis as in extant amniotes. Not only does our study demonstrate that long-bone haematopoiesis was probably not an exaptation to the water-to-land transition but it sheds light on the early evolution of limb-bone development and the sequence of bone-marrow functional acquisitions.
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Ancient fossils give clues as to when features of modern tetrapod bones emerged.
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New light shed on the early evolution of limb bone marrow
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