Ben Creisler
Some new non-dino papers:
Adam P. Cossette & Christopher A. Brochu (2018)
A new specimen of the alligatoroid Bottosaurus harlani and the early history of character evolution in alligatorids.
Journal of Vertebrate Paleontology e1486321
DOI:10.1080/02724634.2018.1486321.
Cranial and postcranial elements attributed to the alligatoroid Bottosaurus harlani Meyer, 1832, are described from the Rowan Fossil Quarry, a CretaceousâPaleogene locality in Mantua Township, New Jersey, U.S.A. This specimen (NJSM 11265) represents the most complete individual attributable to the species and includes significant postcranial elements not found in other specimens. Posterior elements of the skull are described for the first time, and the species is placed into a phylogenetic context. Aspects of the skull table, including constricted supratemporal fenestrae, a linear frontoparietal suture, and a large trapezoidal dorsal supraoccipital exposure, are similar to those of caimans. Bottosaurus harlani is included within Caimaninae due to its possession of a linear frontoparietal suture between the supratemporal fenestrae. Optimal trees from phylogenetic analysis recover B. harlani in three different positions, as a sister either to the modern dwarf caimans (Paleosuchus), to living species of Paleosuchus, or to both. That a substantial stratigraphic gap separates B. harlani from both species of Paleosuchus, which first appears in the Miocene, along with low character and nodal support, raises questions about this relationship. The phylogenetic placement of B. harlani may reflect incomplete knowledge of the taxon, and further study might support placement outside of Caimaninae. More complete analyses of B. harlani and other CretaceousâPaleogene alligatoroids will help to illuminate the relationships among these forms and their living relatives.
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Gianfrancis D. Ugalde, Rodrigo T. MÃller ORCID Icon, HermÃnio Ismael de AraÃjo-JÃnior, SÃrgio Dias-da-Silva & Felipe L. Pinheiro (2018)
A peculiar bonebed reinforces gregarious behaviour for the Triassic dicynodont Dinodontosaurus.Â
Historical Biology (advance online publication)
DOI: 10.1080/08912963.2018.1533960
The discovery and study of bonebeds can provide unique information on the biology of extinct animals. Here we interpret the taphonomic history of a monotypic bonebed composed by several individuals attributable to the dicynodont Dinodontosaurus sp. collected in a classic locality from the Dinodontosaurus Assemblage Zone (Middle Triassic of Brazil). Following the estimation of the minimal number of individuals, we analyzed several biostratinomic processes, such as transport and fragmentation. The assemblage is composed of at least six individuals, all of which are juveniles (although of different sizes), packed in close association and displaying different articulation levels, which indicates a moderate time of subaerial exposure before burial. The dispersion is comprised of bone elements of different Voorhies Groups, indicating the absence of hydraulic selection by transport and a short distance from the death site. The hypothesis of trampling is not discarded, as some bones show pre-burial cracks and fractures. The association of juveniles suggests that factors like insufficient nutrition, abandonment, and diseases could be the cause of death. The monotypic nature of the assemblage, when analyzed together with its possible taphonomic history, allows us to infer gregarious behaviour in Dinodontosaurus.
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Marcello Ruta, Jonathan Krieger, Kenneth D. Angielczyk and Matthew A. Wills (2018)Â
The evolution of the tetrapod humerus: morphometrics, disparity, and evolutionary rates.
Earth and Environmental Science Transactions of The Royal Society of Edinburgh (advance online publication)
The present study explores the macroevolutionary dynamics of shape changes in the humeri of all major grades and clades of early tetrapods and their fish-like forerunners. Coordinate point eigenshape analysis applied to humeral outlines in extensor view reveals that fish humeri are more disparate than those of most early tetrapod groups and significantly separate from the latter. Our findings indicate sustained changes in humeral shape in the deepest portions of the tetrapod stem group and certain portions of the crown. In the first half of sampled tetrapod history, subclades show larger than expected humeral disparity, suggesting rapid diffusion into morphospace. Later in tetrapod evolution, subclades occupy smaller and non-overlapping morphospace regions. This pattern may reflect in part increasing specialisations in later tetrapod lineages. Bayesian shifts in rates of evolutionary change are distributed discontinuously across the phylogeny, and most of them occur within rather than between major groups. Most shifts with the highest Bayesian posterior probabilities are observed in lepospondyls. Similarly, maximum likelihood analyses of shifts support marked rate accelerations in lepospondyls and in various subclades within that group. In other tetrapod groups, rates either tend to slow down or experience only small increases. Somewhat surprisingly, no shifts are concurrent with structural, functional, or ecological innovations in tetrapod evolution, including the origin of digits, the waterâland transition and increasing terrestrialisation. Although counterintuitive, these results are consistent with a model of continual phenotypic innovation that, although decoupled from key evolutionary changes, is possibly triggered by niche segregation in divergent clades and grades of early tetrapods.