Caipirasuchus attenboroughi sp. nov.
https://repositorio.unesp.br/bitstream/handle/11449/191885/ruiz_jv_me_sjrp_int.pdfSphagesauridae is a group of notosuchian crocodyliforms from the Late Cretaceous of South America characterized by highly specialized jaws and dentition. Here, we describe a new sphagesaurid from the Santo AnastÃcio Formation (Caiuà Group, Bauru Basin), south-east Brazil. The specimen is composed of a partial palate, neurocranium, mandible and fragmentary teeth. It represents a new species that can be assigned to Caipirasuchus due to the presence of a lateromedially narrow and anteroposteriorly long mandibular symphyseal region, apicobasal ridges on the posterior teeth, a diastema between D5 and D6, and a linear row of large neurovascular foramina on the lateral surface of the dentary. It differs from previously described Caipirasuchus species based on a ventrolaterally inclined surface of the dentaries posterior to the tooth row, a connection between the anteroventral margin of the external mandibular fenestra and the floor of the Meckelian canal, and the anterior process of the angular forming a 'V'-shaped suture in its contact with the splenial. The results of a phylogenetic analysis of notosuchians recovered the so-called 'advanced notosuchians' in a clade, for which we propose a phylogenetic definition and erect the name Sphagesauria. We also recovered two more inclusive clades encompassing an array of Mesozoic notosuchians, here named Xenodontosuchia, which includes Sphagesauriaâ+âBaurusuchia, and Eunotosuchia, including Xenodontosuchia, Uruguaysuchidae and other Cretaceous forms.
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Free pdf:
E. Hekkala, J. Gatesy, A. Narechania, R. Meredith, M. Russello, M. L. Aardema, E. Jensen, S. Montanari, C. Brochu, M. Norell & G. Amato (2021)
Paleogenomics illuminates the evolutionary history of the extinct Holocene âhornedâ crocodile of Madagascar, Voay robustus.
Communications Biology 4, Article number: 505
doi:
https://doi.org/10.1038/s42003-021-02017-0https://www.nature.com/articles/s42003-021-02017-0Free pdf:
https://www.nature.com/articles/s42003-021-02017-0.pdf
Ancient DNA is transforming our ability to reconstruct historical patterns and mechanisms shaping modern diversity and distributions. In particular, molecular data from extinct Holocene island faunas have revealed surprising biogeographic scenarios. Here, we recovered partial mitochondrial (mt) genomes for 1300â1400 year old specimens (nâ=â2) of the extinct "horned" crocodile, Voay robustus, collected from Holocene deposits in southwestern Madagascar. Phylogenetic analyses of partial mt genomes and tip-dated timetrees based on molecular, fossil, and stratigraphic data favor a sister group relationship between Voay and Crocodylus (true crocodiles). These well supported trees conflict with recent morphological systematic work that has consistently placed Voay within Osteolaeminae (dwarf crocodiles and kin) and provide evidence for likely homoplasy in crocodylian cranial anatomy and snout shape. The close relationship between Voay and Crocodylus lends additional context for understanding the biogeographic origins of these genera and refines competing hypotheses for the recent extinction of Voay from Madagascar.
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Marine reptiles and mammals are phylogenetically so distant from each other that their marine adaptations are rarely compared directly. We reviewed ecophysiological features in extant nonâavian marine tetrapods representing 31 marine colonizations to test whether there is a common pattern across higher taxonomic groups, such as mammals and reptiles. Marine adaptations in tetrapods can be roughly divided into aquatic and haline adaptations, each of which seems to follow a sequence of three steps. In combination, these six categories exhibit five steps of marine adaptation that apply across all clades except snakes: Step M1, incipient use of marine resources; Step M2, direct feeding in the saline sea; Step M3, water balance maintenance without terrestrial fresh water; Step M4, minimized terrestrial travel and loss of terrestrial feeding; and Step M5, loss of terrestrial thermoregulation and fur/plumage. Acquisition of viviparity is not included because there is no known case where viviparity evolved after a tetrapod lineage colonized the sea. A similar sequence is found in snakes but with the haline adaptation step (Step M3) lagging behind aquatic adaptation (haline adaptation is Step S5 in snakes), most likely because their unique method of water balance maintenance requires a supply of fresh water. The same constraint may limit the maximum body size of fully marine snakes. Steps M4 and M5 in all taxa except snakes are associated with skeletal adaptations that are mechanistically linked to relevant ecophysiological features, allowing assessment of marine adaptation steps in some fossil marine tetrapods. We identified four fossil clades containing members that reached Step M5 outside of stem whales, pinnipeds, sea cows and sea turtles, namely Eosauropterygia, Ichthyosauromorpha, Mosasauroidea, and Thalattosuchia, while five other clades reached Step M4: Saurosphargidae, Placodontia, Dinocephalosaurus, Desmostylia, and Odontochelys. Clades reaching Steps M4 and M5, both extant and extinct, appear to have higher species diversity than those only reaching Steps M1 to M3, while the total number of clades is higher for the earlier steps. This suggests that marine colonizers only diversified greatly after they minimized their use of terrestrial resources, with many lineages not reaching these advanced steps. Historical patterns suggest that a clade does not advance to Steps M4 and M5 unless these steps are reached early in the evolution of the clade. Intermediate forms before a clade reached Steps M4 and M5 tend to become extinct without leaving extant descendants or fossil evidence. This makes it difficult to reconstruct the evolutionary history of marine adaptation in many clades. Clades that reached Steps M4 and M5 tend to last longer than other marine tetrapod clades, sometimes for more than 100 million years.
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Silke G. C. Cleuren, David P. Hocking & Alistair R. Evans (2021)
Fang evolution in venomous snakes: adaptation of 3D tooth shape to the biomechanical properties of their prey.
Venomous snakes are among the world's most specialised predators. During feeding, they use fangs to penetrate the body tissues of their prey, but the success of this penetration depends on the shape of these highly specialised teeth. Here, we examined the evolution of fang shape in a wide range of snakes using 3D geometric morphometrics (3DGM) and crossâsectional tooth sharpness measurements. We investigated the relationship of these variables with six diet categories based on the prey's biomechanical properties, and tested for evolutionary convergence using two methods. Our results show that slender elongate fangs with sharp tips are used by snakes that target softâskinned prey (e.g. mammals), while fangs become more robust and blunter as the target's skin becomes scaly (e.g. fish, reptiles) and eventually hardâshelled (e.g. crustaceans), both with and without correction for evolutionary allometry. Convergence in fang shape is present, indicating that fangs of snakes with the same diet are more similar than those of closely related species with different diets. Establishing the relationship between fang morphology and diet helps to explain how snakes became adapted to different lifestyles, while also providing a proxy to infer diet in lesserâknown species or extinct snakes from the fossil record.
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Also:
The Frenchman Formation exposed within Chambery Coulee in southwestern Saskatchewan, Canada, has yielded exceptional vertebrate fauna specimens, including one of the largest known Tyrannosaurus rex individuals. The site has excellent preservation of a rich and diverse paleobotanical assemblage containing amber, which is analyzed in detail and compared to other sources of paleoecological data herein. Fourier-Transform Infrared (FTIR) spectroscopy of the fossil resin suggests a botanical source among the Cupressaceae (cypress trees). The ecological requirements of the crocodilians imply a mean annual temperature of 16ÂC, which is slightly higher than previous estimates based on paleobotanical analyses. Stable isotope analyses of amber in the deposit provided insight into the environment and the ecological conditions at the time of resin secretion. The ÎD values showed a marine enrichment that suggests proximity to oceanic waters, and by extension, strong influence of the Western Interior Seaway in the region during the latest Cretaceous. The carbon isotope composition might also indicate that a potential ecological stress affected the trees such as a drought. These results highlight the interest of including amber in bonebed studies: even in the absence of identifiable inclusions, valuable paleoenvironmental, paleoecological, and even paleogeographic clues can be derived from chemical analyses of fossil resins.