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[dinosaur] Avian maxillary bone + glyptodont body armor + sabertooth cats






Ben Creisler
bcreisler@gmail.com


Some (sort of) recent non-dino papers that may be of interest:



Gerald Mayr (2018)
Comparative morphology of the avian maxillary bone (os maxillare) based on an examination of macerated juvenile skeletons.
Acta Zoologica (advance online publication)
doi: https://doi.org/10.1111/azo.12268
https://onlinelibrary.wiley.com/doi/10.1111/azo.12268


For the first time, isolated maxillary bones of juvenile neornithine birds are examined and compared. Contrary to the anatomical terminology currently employed, the avian maxillare exhibits five rather than four processes. In addition to the praemaxillary, jugal, nasal, and maxillopalatine processes, all palaeognathous and many neognathous birds also have a palatine process. The occurrence of these processes is, however, variable across different clades and only few taxa exhibit a pentaradiate maxillare with all five processes. Within Neognathae, a great morphological variability exists in the shape of the maxillopalatine process, which is more easily studied in juvenile individuals, in which the bones of the beak and palate are not coâossified. In some Neognathae, a caudally facing recess is situated in the junction of the maxillopalatine and jugal processes, which is likely to be homologous to the pneumatic recess of palaeognathous birds. Several derived morphologies of potential phylogenetic significance for the characterization of neognathous clades are identified and major morphological transformations in the lineage leading towards modern birds are highlighted.


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Anton du Plessis, Chris Broeckhoven, Igor Yadroitsev, Ina Yadroitsava, Stephan Gerhard le Roux (2018)
Analyzing nature's protective design: The glyptodont body armor.
Journal of the Mechanical Behavior of Biomedical Materials 82: 218-223
doi: https://doi.org/10.1016/j.jmbbm.2018.03.037Â
https://www.sciencedirect.com/science/article/pii/S1751616118301656



Many animal species evolved some form of body armor, such as scales of fish and bony plates or osteoderms of reptiles. Although a protective function is often taken for granted, recent studies show that body armor might comprise multiple functionalities and is shaped by trade-offs among these functionalities. Hence, despite the fact that natural body armor might serve as bio-inspiration for the development of artificial protective materials, focussing on model systems in which body armor serves a solely protective function might be pivotal. In this study, we investigate the osteoderms of Glyptotherium arizonae, an extinct armadillo-like mammal in which body armor evolved as protection against predators and/or tail club blows of conspecifics. By using a combination of micro-computed tomography, reverse-engineering, stress simulations and mechanical testing of 3D printed models, we show that the combination of dense compact layers and porous lattice core might provide an optimized combination of strength and high energy absorption.

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Paolo Piras, Daniele Silvestro, Francesco Carotenuto, Silvia Castiglione, Anastassios Kotsakis, Leonardo Maiorino, Marina Melchionna, Alessandro Mondanaro, Gabriele Sansalone, Carmela Serio, Veronica Anna Vero & Pasquale Raia (2018)
Evolution of the sabertooth mandible: A deadly ecomorphological specialization.
Palaeogeography, Palaeoclimatology, Palaeoecology 496: 166-174
doi: https://doi.org/10.1016/j.palaeo.2018.01.034
https://www.sciencedirect.com/science/article/pii/S0031018217310465

Preprint in Research Gate:

https://www.researchgate.net/publication/322895085_Evolution_of_the_sabertooth_mandible_A_deadly_ecomorphological_specialization

Highlights

Sabertoothness evolved at least seven times among carnivorous mammals and mammal-like reptiles.
Sabertooths show highly derived cranial morphology and probably had narrow feeding niches.
Specialization is usually linked to high extinction risk in living and fossil species.
We demonstrated sabertooth evolved at different rates and had higher extinction risk than other members of the cat family.



Abstract

Saber-toothed cats were armed with formidable weapons. They evolved a number of highly derived morphological features, most notably a pair of extremely long upper canines, which makes them unique within the felid family. Although the sabertooth character evolved several times among carnivorous mammals, sabertooth clades mostly had disjunctive occurrences both in space and time, and no sabertooth is alive today. We studied the rates of phenotypic and taxonomic diversification in the mandible of sabertooths, as compared to the rates calculated for both extinct and extant conical toothed cats. We found that the mandible's shape and physical properties in sabertooth clades evolved at distinctly higher rates than the rest of the felid tree. In addition, sabertooths had similar speciation rate to conical toothed cats, but statistically higher extinction rate. The wealth of morphological specializations required to be a sabertooth, and their tendency to focus on large-sized species as prey, was likely responsible for such high extinction rate, and for the peculiar, disjunctive patterns of sabertooth clade occurrence in the fossil record.

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Tomohiro Harano & Nobuyuki Kutsukake (2018)
Journal of Evolutionary Biology (advance online publication)
Directional selection in the evolution of elongated upper canines in clouded leopards and sabreâtoothed cats.
doi: https://doi.org/10.1111/jeb.13309
https://onlinelibrary.wiley.com/doi/10.1111/jeb.13309



Extremely developed or specialized traits such as the elongated upper canines of extinct sabreâtoothed cats are often not analogous to those of any extant species, which limits our understanding of their evolutionary cause. However, an extant species may have undergone directional selection for a similar extreme phenotype. Among living felids, the clouded leopard, Neofelis nebulosa, has exceptionally long upper canines for its body size. We hypothesized that directional selection generated the elongated upper canines of clouded leopards in a manner similar to the process in extinct sabreâtoothed cats. To test this, we developed an approach that compared the effect of directional selection among lineages in a phylogeny using a simulation of trait evolution and approximate Bayesian computation. This approach was applied to analyse the evolution of upper canine length in the Felidae phylogeny. Our analyses consistently showed directional selection favouring longer upper canines in the clouded leopard lineage and a lineage leading to the sabreâtoothed cat with the longest upper canines, Smilodon. Most of our analyses detected an effect of directional selection for longer upper canines in the lineage leading to another sabreâtoothed cat, Homotherium, although this selection may have occurred exclusively in the primitive species. In all the analyses, the clouded leopard and Smilodon lineages showed comparable directional selection. This implies that clouded leopards share a selection advantage with sabreâtoothed cats in having elongated upper canines.