Ben Creisler
Some recent non-dino papers:
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Stable isotopes allow understanding palaeobiology and lifestyle of Permian tetrapods.
Oxygen stable isotopes indicate Endothiodon was more water-dependent than Tropidostoma.
Carbon Stable isotopes reveal dicynodont Endothiodon fed on riverine vegetation.
Stable carbon isotopes show diet of juvenile Endothiodon probably included insects.
Abstract
The late Permian dicynodont Endothiodon is characterized by its specialized feeding system, most notably manifested in its long rows of post-canine teeth and corresponding keratinous surfaces. This specialisation has fuelled discussion of not only the masticatory biomechanics in Endothiodon but also of its diet and ecology. To shed light on the latter two, we compared the oxygen (Î18Op) and carbon (Î13Cc) stable isotope compositions of Endothiodon tooth and bone apatite with those of the co-occurring dicynodont Tropidostoma, another late Permian dicynodont of similar size. Preliminary results indicate that Endothiodon had significantly lower ratios for stable isotopes of both oxygen and carbon. The Î18Op values from Endothiodon suggest that its lifestyle was more water-dependent (i.e. obligate drinker) than Tropidostoma, pointing to the possibility of a semi-aquatic ecology, whereas Î13Cc values suggest that Endothiodon had a diet primarily comprising riverine vegetation, with the possibility that juveniles consumed terrestrial insects. The data suggest a negligible role for roots, seeds, or algae in the diet of Endothiodon.
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Free pdf:
Carla Cicero, Nicholas A. Mason, Lauryn Benedict & James D. Rising (2020)
Behavioral, morphological, and ecological trait evolution in two clades of New World Sparrows (Aimophila and Peucaea, Passerellidae)
PeerJ 8:e9249
doi: Â
https://doi.org/10.7717/peerj.9249https://peerj.com/articles/9249/Â
The New World sparrows (Passerellidae) are a large, diverse group of songbirds that vary in morphology, behavior, and ecology. Thus, they are excellent for studying trait evolution in a phylogenetic framework. We examined lability versus conservatism in morphological and behavioral traits in two related clades of sparrows (Aimophila, Peucaea), and assessed whether habitat has played an important role in trait evolution. We first inferred a multi-locus phylogeny which we used to reconstruct ancestral states, and then quantified phylogenetic signal among morphological and behavioral traits in these clades and in New World sparrows more broadly. Behavioral traits have a stronger phylogenetic signal than morphological traits. Specifically, vocal duets and song structure are the most highly conserved traits, and nesting behavior appears to be maintained within clades. Furthermore, we found a strong correlation between open habitat and unpatterned plumage, complex song, and ground nesting. However, even within lineages that share the same habitat type, species vary in nesting, plumage pattern, song complexity, and duetting. Our findings highlight trade-offs between behavior, morphology, and ecology in sparrow diversification.
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Free pdf:
Jainemys pisdurensis comb. nov. is an extinct pleurodiran turtle from the Late Cretaceous (Maastrichtian) of India, previously referred to Carteremys and Shweboemys. The holotype, an eroded skull, had been collected near the village of Pisdura, south of Nagpur, in Maharashtra State, while all referred shell material originates from coeval sediments exposed at the nearby village of Dongargaon. Initial estimates believed this turtle to either be an early representative of Podocnemididae or a basal representative of Pelomedusoides.
Methods
We here figure and describe all specimens that had previously been referred to Jainemys pisdurensis comb. nov. We furthermore re-evaluate the validity of this fossil turtle and explore its phylogenetic relationships within Pleurodira.
Results
The holotype of Jainemys pisdurensis comb. nov. displays a morphology that differs substantially from that originally reported. Most notably, the palatines only have a minor contribution to the broad triturating surfaces but have a broad midline contact with each other, the pterygoids only have a midline contact of intermediate length and do not contact the opisthotics posteriorly, the basisphenoid is broad and short, and the opisthotics do not contribute to the flooring of the cavum acustico-jugulare. The referred shell material also displays a morphology different from that reported originally, in particular in that vertebral I does not contribute to the anterior margin of the carapace while the nuchal does. Phylogenetic analysis places the cranial material within the bothremydid clade Kurmademydini, while the shell material is placed in an unresolved polytomy at the base of this clade. Jainemys pisdurensis is confirmed to be a valid species of pleurodiran turtle, but the high diversity of coeval kurmademydines in India demands removal of the postcranial remains from this taxon. The realization that all valid species of Late Cretaceous (Maastrichtian) turtles from India form a clade supports the hypothesis that India was physically separated from the rest of Gondwana at this time.
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Free pdf:
Among turtles, cases of "gigantism" occur mostly in pleurodiran Pelomedusoides and cryptodirans, but are infrequent among pleurodiran chelids, which are mostly small-medium sized turtles. Yaminuechelys spp. are extinct South American long-necked chelids (from the Late Cretaceousâearly Paleocene of Patagonia, Argentina) with caparaces almost three times larger than their extant sister taxon, Hydromedusa tectifera. Since evolutionary changes in size can be analyzed based on growth dynamics, we studied growth strategies from an osteohistological point of view. We sampled both extinct (Yaminuechelys maior) and extant (H. tectifera) species, in order to test hypotheses related to the mechanisms involved in the macroevolution of size within this clade. For this purpose, thin sections of long bone (humerus and femur) shafts of specimens of different ontogenetic stages for these species were prepared. The osteohistological study reveals a similar growth dynamic in both taxa, with a poorly vascularized cortex dominated by parallel- fibered bone and interrupted by lines of arrested growth (LAGs). The huge body size of Y. maior appears to be a consequence of the prolongation of the growth phase, suggesting that it had a longer lifespan than H. tectifera, allowing to reach greater sizes. In this way, and assuming that there is no displacement at the beginning of development (e.g., a delay in the earliest stages of growth) in H. tectifera, the acquisition of a large size in Yaminuechelys would be explained by hypomorphosis of the former or hypermorphosis of the latter, depending on the reconstruction of the ancestral condition of this clade.
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Non-fossil, but important...
Free pdf:
Craig B. Stanford, John B. Iverson, Anders G.J. Rhodin, Peter Paul van Dijk, Russell A. Mittermeier, Gerald Kuchling, Kristin H. Berry, Alberto Bertolero, Karen A. Bjorndal, Torsten E.G. Blanck, Kurt A. Buhlmann, Russell L. Burke, Justin D. Congdon, Tomas Diagne, Taylor Edwards, Carla C. Eisemberg, Josh R. Ennen, GermÃn Forero-Medina, Matt Frankel, Uwe Fritz, Natalia Gallego-GarcÃa, Arthur Georges, J. Whitfield Gibbons, Shiping Gong, Eric V. Goode, Haitao T. Shi, Ha Hoang, Margaretha D. Hofmeyr, Brian D. Horne, Rick Hudson, James O. Juvik, Ross A. Kiester, Patricia Koval, Minh Le, Peter V. Lindeman, Jeffrey E. Lovich, Luca Luiselli, Timothy E.M. McCormack, George A. Meyer, Vivian P. PÃez, Kalyar Platt, Steven G. Platt, Peter C.H. Pritchard, Hugh R. Quinn, Willem M. Roosenburg, Jeffrey A. Seminoff, H. Bradley Shaffer, Ricky Spencer, James U. Van Dyke, Richard C. Vogt & Andrew D. Walde (2020)
Turtles and Tortoises Are in Trouble.
Current Biology 30(12): PR721-R735
DOI:
https://doi.org/10.1016/j.cub.2020.04.088https://www.cell.com/current-biology/fulltext/S0960-9822(20)30636-9
Free pdf:
Turtles and tortoises (chelonians) have been integral components of global ecosystems for about 220 million years and have played important roles in human culture for at least 400,000 years. The chelonian shell is a remarkable evolutionary adaptation, facilitating success in terrestrial, freshwater and marine ecosystems. Today, more than half of the 360 living species and 482 total taxa (species and subspecies combined) are threatened with extinction. This places chelonians among the groups with the highest extinction risk of any sizeable vertebrate group. Turtle populations are declining rapidly due to habitat loss, consumption by humans for food and traditional medicines and collection for the international pet trade. Many taxa could become extinct in this century. Here, we examine survival threats to turtles and tortoises and discuss the interventions that will be needed to prevent widespread extinction in this group in coming decades.
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Anne-Claire Fabre, Carla Bardua, Margot Bon, Julien Clavel, Ryan N. Felice, Jeffrey W. Streicher, Jeanne Bonnel, Edward L. Stanley, David C. Blackburn & Anjali Goswami (2020)
Metamorphosis shapes cranial diversity and rate of evolution in salamanders.
Nature Ecology & Evolution (2020)
DOI: 10.1038/s41559-020-1225-3
https://www.nature.com/articles/s41559-020-1225-3
Metamorphosis is widespread across the animal kingdom and induces fundamental changes in the morphology, habitat and resources used by an organism during its lifetime. Metamorphic species are likely to experience more dynamic selective pressures through ontogeny compared with species with single-phase life cycles, which may drive divergent evolutionary dynamics. Here, we reconstruct the cranial evolution of the salamander using geometric morphometric data from 148 species spanning the orderâs full phylogenetic, developmental and ecological diversity. We demonstrate that life cycle influences cranial shape diversity and rate of evolution. Shifts in the rate of cranial evolution are consistently associated with transitions from biphasic to either direct-developing or paedomorphic life cycle strategies. Direct-developers exhibit the slowest rates of evolution and the lowest disparity, and paedomorphic species the highest. Species undergoing complete metamorphosis (biphasic and direct-developing) exhibit greater cranial modularity (evolutionary independence among regions) than do paedomorphic species, which undergo differential metamorphosis. Biphasic and direct-developing species also display elevated disparity relative to the evolutionary rate for bones associated with feeding, whereas this is not the case for paedomorphic species. Metamorphosis has profoundly influenced salamander cranial evolution, requiring greater autonomy of cranial elements and facilitating the rapid evolution of regions that are remodelled through ontogeny. Rather than compounding functional constraints on variation, metamorphosis seems to have promoted the morphological evolution of salamanders over 180 million years, which may explain the ubiquity of this complex life cycle strategy across disparate organisms.
News:
New study reveals how metamorphosis has shaped the evolution of salamanders
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