Showing posts with label dyrosaurid mesoeucrocodylians. Show all posts
Showing posts with label dyrosaurid mesoeucrocodylians. Show all posts

Thursday, September 15, 2011

Acherontisuchus guajiraensis Hastings et al. 2011 - A New Fossil Crocodilian

Acherontisuchus may have looked like this in its natural setting. Titanoboa
is shown in the background. Artist credit: Florida Museum of Natural History,
 illustration by Danielle Byerley.
Fossils of dyrosaurid mesoeucrocodylians are known from Africa, Eurasia, North America and South America and distributed from the Late Cretaceous to the late Eocene, a time span of about 65 MYA, and evidence that the clade survived the K-T extinction. Only three South America dryosaurids are known but Hastings et al. (2011) have added another in the last few days - Acherontisuchus guajiraensis from the Cerrejon Formation of northwest Columbia. The new species is based on three partial mandibles, maxillary fragments, teeth, and some postcranial material. Acherontisuchus' morphology suggests it may have may have inhabited slow moving rivers. Most dyrosaurids have been thought to be shallow, near-shore marine inhabitants that use axial swimming that is typical of living crocodilians, but they may have differed from modern species with greater tail undulatory frequency and more powerful forward thrust provided by expanded tail muscles. The authors estimate it was between 4.66 and 6.46 m in adult body length, while Cerrejonisuchus improcerus another dryosaurid that lived at the same locality, at the same time, was only about 2.2 m in length. Cerrejonisuchus had a more generalized bodied and may have preyed upon small vertebrates, while Acherontisuchus was more specialized and the authors suggest it preyed upon dipnoan and elopomorph fishes have been have also been found at the Cerrejon location. Also of interest, these dryosaurids lived at a time and place that was shared with the largest known snake, Titanoboa, a possible predator for both of these dryosaurids. The entire article is available on-line.

Hastings, A.K., Bloch, J. I., & Jaramillo, C.A. (2011). A new longirostrine dyrosaurid (Crocodylomorpha, Mesoeucrocodylia) from the Paleocene of north-eastern Colombia: biogeographic and behavioural implications for New-World Dyrosauridae Palaeontology, 54, 1095-1116.doi10.1111/j.1475-4983.2011.01092.