Ben Creisler
Some recent non-dino papers:
Free pdf:
Tiago R Simoes, Oksana Vernygora, Michael W Caldwell & Stephanie E Pierce (2020)
Megaevolutionary dynamics in reptiles and the role of adaptive radiations in evolutionary innovation.
bioRxiv 2020.04.22.055061 (preprint)
doi: https://doi.org/10.1101/2020.04.22.055061
https://www.biorxiv.org/content/10.1101/2020.04.22.055061v1
Adaptive radiations are long believed to be responsible for the origin of phenotypic diversity and new body plans among higher clades in the fossil record. However, few studies have assessed rates of phenotypic evolution and disparity across broad scales of time to understand the evolutionary dynamics behind the origin of major clades, or how they relate to rates of molecular evolution. Here, we provide a total evidence approach to this problem using the largest available data set on diapsid reptiles. We find a strong decoupling between phenotypic and molecular rates of evolution, with many periods of accelerated phenotypic evolution or expansion of phenotypic disparity at the origin of major reptile clades and body plans that do not correspond to periods of adaptive radiation. We find heterogeneous rates of evolution during the acquisition of similarly adapted functional types, and that the origin of snakes is marked by exceptionally high evolutionary rates.
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Thomas MÃrs, Marcelo Reguero & Davit Vasilyan Â(2020)
First fossil frog from Antarctica: implications for Eocene high latitude climate conditions and Gondwanan cosmopolitanism of Australobatrachia
Scientific Reports 10, Article number: 5051
doi: https://doi.org/10.1038/s41598-020-61973-5
https://www.nature.com/articles/s41598-020-61973-5
First fossil frog from Antarctica: implications for Eocene high latitude climate conditions and Gondwanan cosmopolitanism of Australobatrachia
Scientific Reports 10, Article number: 5051
doi: https://doi.org/10.1038/s41598-020-61973-5
https://www.nature.com/articles/s41598-020-61973-5
Cenozoic ectothermic continental tetrapods (amphibians and reptiles) have not been documented previously from Antarctica, in contrast to all other continents. Here we report a fossil ilium and an ornamented skull bone that can be attributed to the Recent, South American, anuran family Calyptocephalellidae or helmeted frogs, representing the first modern amphibian found in Antarctica. The two bone fragments were recovered in Eocene, approximately 40 million years old, sediments on Seymour Island, Antarctic Peninsula. The record of hyperossified calyptocephalellid frogs outside South America supports Gondwanan cosmopolitanism of the anuran clade Australobatrachia. Our results demonstrate that Eocene freshwater ecosystems in Antarctica provided habitats favourable for ectothermic vertebrates (with mean annual precipitation â900âmm, coldest month mean temperature â3.75âÂC, and warmest month mean temperature â13.79âÂC), at a time when there were at least ephemeral ice sheets existing on the highlands within the interior of the continent.
News:
https://www.sciencenews.org/article/first-frog-fossil-antarctica-found-ancient-climate
https://phys.org/news/2020-04-fossil-frogs-insights-ancient-antarctica.html
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Natasha Stepanova & ÂMolly C. Womack (2020)
Anuran limbs reflect microhabitat and distal, laterâdeveloping bones are more evolutionarily labile
Evolution (advance online publication)
doi: https://doi.org/10.1111/evo.13981
https://onlinelibrary.wiley.com/doi/10.1111/evo.13981
Tetrapod limbs have been used as a model system to investigate how selective pressures and constraints shape morphological evolution. Anurans have had many independent transitions to various microhabitats, allowing us to dissect how these factors influence limb morphology. Furthermore, anurans provide a unique system to test the generality of developmental constraints proposed in mammals, namely that laterâdeveloping limb bones are under less constraint and show more variation. We used microâcomputed tomography scans of 236 species from 52 of 55 families, geometric morphometrics, and modern phylogenetic comparative methods to examine how limb bones are related to microhabitat, phylogeny, allometry, and developmental timing. Although there was significant phylogenetic signal, anuran limb shape showed a relationship with microhabitat and to a lesser extent, body size. We found that distal bones had higher evolutionary rates than proximal bones, providing evidence that developmental constraints are reduced in laterâdeveloping bones. Distal bones also showed increased selection related to allometry and microhabitat, providing an additional explanation for higher evolutionary rates. By looking at the evolution of limb shape across a diverse clade, we demonstrated that multiple factors have shaped anuran limbs and that greater evolutionary lability in laterâdeveloping limb bones is likely a general trend among tetrapods.
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Patrick L. Jambura & JÃrgen Kriwet (2020)
Articulated remains of the extinct shark Ptychodus (Elasmobranchii, Ptychodontidae) from the Upper Cretaceous of Spain provide insights into gigantism, growth rate and life history of ptychodontid sharks
PLoS ONE 15(4): e0231544
doi: https://doi.org/10.1371/journal.pone.0231544
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0231544
Due to their cartilaginous endoskeleton and the continuous tooth replacement, the chondrichthyan fossil record predominantly consists of isolated teeth, which offer diagnostic features for taxonomic identifications, but only provide very limited information of an organismâs life history. In contrast, the calcified vertebral centra of elasmobranchs (sharks, skates and rays) yield important information about ecological and biological traits that can be utilized for constructing age-structured population dynamic models of extant species and palaeoecological reconstructions of such aspects in extinct groups. Here, we describe two large shark vertebrae from the Santonian (Upper Cretaceous) of Spain, which show a unique combination of characters (asterospondylic calcification pattern, with concentric lamellae and numerous parallel bands that are oriented perpendicular) that is only known from ptychodontid sharks, a distinct, extinct group of giant durophagous sharks of the Cretaceous era. Based on linear regression models for large extant sharks a total length between 430 and 707cm was estimated for the examined specimen. Our results indicate that ptychodontid sharks were large viviparous animals, with slow growth rates, matured very late and, therefore, show typical traits for K-selected species. These traits combined with a highly specialized feeding ecology might have played a crucial role for the success but also, eventually, extinction of this group.
Articulated remains of the extinct shark Ptychodus (Elasmobranchii, Ptychodontidae) from the Upper Cretaceous of Spain provide insights into gigantism, growth rate and life history of ptychodontid sharks
PLoS ONE 15(4): e0231544
doi: https://doi.org/10.1371/journal.pone.0231544
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0231544
Due to their cartilaginous endoskeleton and the continuous tooth replacement, the chondrichthyan fossil record predominantly consists of isolated teeth, which offer diagnostic features for taxonomic identifications, but only provide very limited information of an organismâs life history. In contrast, the calcified vertebral centra of elasmobranchs (sharks, skates and rays) yield important information about ecological and biological traits that can be utilized for constructing age-structured population dynamic models of extant species and palaeoecological reconstructions of such aspects in extinct groups. Here, we describe two large shark vertebrae from the Santonian (Upper Cretaceous) of Spain, which show a unique combination of characters (asterospondylic calcification pattern, with concentric lamellae and numerous parallel bands that are oriented perpendicular) that is only known from ptychodontid sharks, a distinct, extinct group of giant durophagous sharks of the Cretaceous era. Based on linear regression models for large extant sharks a total length between 430 and 707cm was estimated for the examined specimen. Our results indicate that ptychodontid sharks were large viviparous animals, with slow growth rates, matured very late and, therefore, show typical traits for K-selected species. These traits combined with a highly specialized feeding ecology might have played a crucial role for the success but also, eventually, extinction of this group.
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