Encontraram mais um elo perdido que preenche a lacuna na árvore da família Dino

quarta-feira, abril 13, 2011

New Species of Dinosaur Bridges Gap in Dinosaur Family Tree

ScienceDaily (Apr. 13, 2011) — A team of scientists led by the Smithsonian Institution has discovered a fossilized dinosaur skull and neck vertebrae that not only reveal a new species, but also an evolutionary link between two groups of dinosaurs. The new species, Daemonosaurus chauliodus, was discovered at Ghost Ranch, N.M. The team's findings are published in theProceedings of the Royal Society B on April 13.

This rendering of Daemonosaurus chauliodus shows its size relative to an American quarter. The species name chauliodus is derived from the Greek word for "buck-toothed" and refers to the species' big slanted front teeth. (Credit: Jeffrey Martz)

The oldest known dinosaurs walked or ran on their hind legs and included early predatory species such as Herrerasaurus. They existed in what are now Argentina and Brazil early in the Late Triassic Period, approximately 230 million years ago. The evolutionary position of these early predatory dinosaurs was contentious because there was a gap in the fossil record between them and later theropod dinosaurs. The team's discovery of Daemonosaurus chauliodus helps fill in this gap.

Because only the skull and neck of Daemonosaurus were found, the total length of the new species is unknown. The dinosaur's skull, however, is narrow and relatively deep, measuring 5.5 inches long from the tip of its snout to the back of the skull and has proportionately large eye sockets. The upper jaw has large, forward-slanted front teeth. It is this feature that helped the scientists name the species. The name Daemonosaurus is based on the Greek words "daimon" meaning evil spirit (because it was found at Ghost Ranch), and "sauros" meaning lizard or reptile. The species name chauliodus is derived from the Greek word for "buck-toothed" and refers to the species' big slanted front teeth.

Daemonosaurus, a basal (primitive) theropod species, was dated to the latest part of the Triassic Period approximately 205 million years ago, just before the beginning of the Jurassic Period. This altered the previous belief that all basal dinosaurs had vanished millions of years earlier. The skull and neck vertebrae of Daemonosaurus also revealed several features similar to those in neotheropods -- the succeeding group of dinosaurs on the evolutionary timeline. 


Read more her/Leia mais aqui: Science Daily

A late-surviving basal theropod dinosaur from the latest Triassic of North America

Hans-Dieter Sues1,*, Sterling J. Nesbitt2, David S Berman3 and Amy C. Henrici3

Author Affiliations

1Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, MRC 121, PO Box 37012, Washington, DC 20013-7012, USA
2Department of Biology, University of Washington, Seattle, WA 98195-1800, USA
3Section of Vertebrate Paleontology, Carnegie Museum of Natural History, 4400 Forbes Avenue, Pittsburgh, PA 15213-4080, USA
*Author for correspondence (suesh@si.edu).


The oldest theropod dinosaurs are known from the Carnian of Argentina and Brazil. However, the evolutionary diversification of this group after its initial radiation but prior to the Triassic–Jurassic boundary is still poorly understood because of a sparse fossil record near that boundary. Here, we report on a new basal theropod, Daemonosaurus chauliodus gen. et sp. nov., from the latest Triassic ‘siltstone member’ of the Chinle Formation of the Coelophysis Quarry at Ghost Ranch, New Mexico. Based on a comprehensive phylogenetic analysis, Daemonosaurus is more closely related to coeval neotheropods (e.g. Coelophysis bauri) than to Herrerasauridae and Eoraptor. The skeletal structure of Daemonosaurusand the recently discovered Tawa bridge a morphological gap betweenEoraptor and Herrerasauridae on one hand and neotheropods on the other, providing additional support for the theropod affinities of both Eoraptor and Herrerasauridae and demonstrating that lineages from the initial radiation of Dinosauria persisted until the end of the Triassic. Various features of the skull of Daemonosaurus, including the procumbent dentary and premaxillary teeth and greatly enlarged premaxillary and anterior maxillary teeth, clearly set this taxon apart from coeval neotheropods and demonstrate unexpected disparity in cranial shape among theropod dinosaurs just prior to the end of the Triassic.

Dinosauria, Theropoda, Late Triassic, Chinle Formation, New Mexico

Received February 23, 2011.
Accepted March 21, 2011.
This Journal is © 2011 The Royal Society