Monday, 16 April 2012

A Heterodontosaurid Dinosaur from the Late Jurassic of Colorado.

Heterodontosaurid Dinosaurs were an early group of Ornithischians that appeared in the Late Triassic in Gondwanaland and spread across the globe during the Early Jurassic, surviving into the Early Cretaceous. They were probably the smallest of the Ornithischians, typically under a meter in length, and gain their name from their dentition; they had different shaped teeth in different parts of the jaw, as with modern mammals, which is unusual in dinosaurs, though it has been observed in other Ornithischians.

Fruitadens haagarorum is a Late Jurassic Heterodontosaurid Dinosaur known from a number of fragmentary skeletons from the Upper Jurassic Morrison Formation of the Fruita Paleontological Area, northwest of Grand Junction, Colorado, USA. It is generally considered to be the smallest known Ornithischian Dinosaur, at only 65-75 cm in length and weighing 500-750 grams.

Reconstruction of Fruitadens haagarorum, and the location of the site where it was found. Butler et al. (2010).

In a paper published in the journal PLoS One on 11 April 2012, a team of scientists lead by Richard Butler of the Bayerische Staatssammlung für Paläontologie und Geologie and the GeoBio-Center at Ludwig-Maximilians-Universität München discuss a new reconstruction of the head of Fruitadens haagarorum, and the implications of this for our understanding of the evolution and ecology of Heterodontosaurid Dinosaurs.

Reconstruction of the head of Fruitadens haagarorum. Butler et al. (2012).

Butler et al. conclude that compared that compared to reconstructions of earlier Heterodontosaurid Dinosaurs, Fruitadens haagarorum appears to have been less well suited to tearing at tough vegetation, but much better adapted to making sudden, and repeated, snapping motions with widely opened jaws. From this they conclude that while all Heterodontosaurids were probably omnivorous, the earlier forms probably ate more vegetation, whereas Fruitadens haagarorum, probably ate mostly insects or other invertebrates, with a smaller amount of plant material being consumed, probably on a selective basis.

They furthermore note that Heterodontosaurid Dinosaurs tended to become smaller throughout their evolutionary history. In modern lizards, which also tend to be omnivorous, larger species tend to consume more plant material, whereas smaller species tend to consume more insects. Combining this observation with the new reconstruction of Fruitadens haagarorum, Butler et al. suggest that the Heterodontosaurids probably originated as general omnivores consuming a lot of tough plant material, but over time came to incorporate a lot more non-plant material into their diet, and became more selective about what plant material they would take.

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