Saturday, March 21, 2015

[Paleontology • 2015] Carnufex carolinensis • Early Crocodylomorph increases Top Tier Predator Diversity During Rise of Dinosaurs

Carnufex carolinensis  Zanno, Drymala, Nesbitt & Schneider, 2015

Triassic predatory guild evolution reflects a period of ecological flux spurred by the catastrophic end-Permian mass extinction and terminating with the global ecological dominance of dinosaurs in the early Jurassic. In responding to this dynamic ecospace, terrestrial predator diversity attained new levels, prompting unique trophic webs with a seeming overabundance of carnivorous taxa and the evolution of entirely new predatory clades. Key among these was Crocodylomorpha, the largest living reptiles and only one of two archosaurian lineages that survive to the present day. In contrast to their existing role as top, semi-aquatic predators, the earliest crocodylomorphs were generally small-bodied, terrestrial faunivores, occupying subsidiary (meso) predator roles. Here we describe Carnufex carolinensis a new, unexpectedly large-bodied taxon with a slender and ornamented skull from the Carnian Pekin Formation (~231 Ma), representing one of the oldest and earliest diverging crocodylomorphs described to date. Carnufex bridges a problematic gap in the early evolution of pseudosuchians by spanning key transitions in bauplan evolution and body mass near the origin of Crocodylomorpha. With a skull length of >50 cm, the new taxon documents a rare instance of crocodylomorphs ascending to top-tier predator guilds in the equatorial regions of Pangea prior to the dominance of dinosaurs.


Figure 1: Three dimensional skull reconstruction and representative elements of Carnufex carolinensis (NCSM 21558).

Systematic Paleontology
Archosauria Cope, 1869. Pseudosuchia Zittel, 1887–1890. 

Crocodylomorpha Walker, 1968 sensu Nesbitt 2011. 

Carnufex carolinensis gen. et sp. nov.

Etymology: Carnufex (Latin) butcher; carolinensis, in reference to the region of discovery.

Figure 2: Evolutionary relationships, chronostratigraphic distribution, and estimated body size for putatively terrestrial, carnivorous archosaurians of the Triassic and earliest Jurassic.
(a) Chronostratigraphically calibrated strict consensus tree showing taxonomy and relationships of the pseudosuchian clade Loricata. Carnufex carolinensis posited as a basalmost crocodylomorph. (b) Chronostratigraphically calibrated, bivariate plots of body size in terrestrial carnivorous archosaur clades with clade-specific temporal distributions summarized on the y-axis, and Triassic and earliest Jurassic body size ranges summarized on lower and upper x-axes, respectively. (c) Body size distribution in the Triassic divided by proto-Laurasia and proto-Gondwana. (d) Tetrapod composition of the Carnian-aged Pekin Formation (~231 Ma) to scale. Size estimates based on the proxy femur length (FL) in mm. Error bars denote stratigraphic and FL uncertainty.

Lindsay E. Zanno, Susan Drymala, Sterling J. Nesbitt and Vincent P. Schneider. 2015. Early Crocodylomorph increases Top Tier Predator Diversity During Rise of Dinosaurs. Scientific Reports. 5, Article number: 9276 doi: 10.1038/srep09276

Carnivorous Croc Cousin Stalked the Triassic Carolinas   @ngphenomena