Noasaurus

*Noasaurus leali*

***Noasaurus*** ("Northwestern Argentina lizard") is the name given to a carnivorous dinosaur genus of the late Campanian-Maastrichtian (Late Cretaceous). It was a small (less than eight feet long) theropod, specifically a ceratosaur, discovered by Jaime Powell and José Bonaparte in northwestern Argentina. It was originally thought to have had a toe claw similar to that of dromaeosaurs, but independently developed, but this is now discredited: the "toe claw" was probably actually on the animal's hand.

## Discovery and naming

In the mid-seventies, a fragmentary small theropod skeleton was discovered by Jaime Eduardo Powell and José Fernando Bonaparte at the Estancia El Brete-site. In 1977, the discovery was reported in the scientific literature. The type species, *Noasaurus leali*, was named and described by Bonaparte and Powell in 1980. The generic name begins with a usual abbreviation of noroeste Argentina, "northwest Argentina". The specific name honours the owner of the site, Fidel Leal.

The holotype, PVL 4061, was found in a layer of the Lecho Formation of Salta Province, Argentina, dating from the late Cretaceous period, more precisely the early Maastrichtian stage, about seventy million years ago. It consists of a partial skeleton with skull. It contains the maxilla, the quadrate bone, two neck vertebrae, two neck ribs, the centrum of a back vertebra, two hand claws, a finger phalanx and the second right metatarsal bone. One of the hand claws was initially identified as a second toe claw. In 2004, it was recognised as a hand claw, at which occasion the second hand claw was referred.

In 1999, a neck vertebra found at the site, specimen MACM 622, was identified as oviraptorosaurian, a rare proof that the Oviraptorosauria had invaded the Gondwanan continents. In 2007 however, it was reidentified as a noasaurid vertebra, probably belonging to the *Noasaurus* holotype.

## Description

Compared to those avian-theropods, *Noasaurus* is old fashioned. It is likely a close relative of the larger abelisaurs that shared its habitat; they are both derived from the same *Ceratosaurus*-type basal ceratosaurian ancestor. The discovery of *Masiakasaurus*, a closely related animal from Madagascar, provides evidence for this new theory: it doesn't have a dromaeosaur-style toe claw.

The type species, *Noasaurus leali*, was described by Bonaparte and Powell in 1980.

## Classification

Noasaurus is today considered to be a member of the Ceratosauria. Originally, it was seen as a member of the Coelurosauria. Bonaparte and Powell assigned it to a family of its own, the Noasauridae. In 1988, Gregory S. Paul saw them as members of the Abelisauridae and coined a Noasaurinae within that group. He also incorrectly thought they were Megalosauria. Later, the noasaurids were recognised as close relatives of the larger abelisaurids; they are both derived from the same basal abelisauroid ancestor.

The following cladogram is based on the phylogenetic analysis conducted by Rauhut and Carrano in 2016, showing the relationships of Elaphrosaurus among the noasaurids:

## Paleobiology

In 1980, it was thought that the presumed foot claw functioned as a sickle claw. Paul in 1988 saw the noasaurines as the South-American counterparts of the Asian and North-American dromaeosaurids, in a process of convergent evolution. Noting that abelisaurids tend to have very short arms, he wondered whether the forelimbs of Noasaurus were of limited length also, forcing the animal to employ a kicking technique instead of grasping the back of a victim in order to disembowel it with the foot claws, a method he assumed the dromaeosaurids used. This hypothesis was undermined when it was determined that the foot claw was in fact a hand claw.

In 2001, a more complete genus of noasaurid, Masiakasaurus was discovered. This genus had an unusual down-turned jaw and protruding front teeth which would have been well suited to grasping, and Masiakasaurus may have consumed small vertebrates, fish, or invertebrates. Noasaurus may have been similar in appearance and lifestyle.

## JPInstitute.com Description

Noasaurus was a small South American meat-eater. It lived a time when some of the biggest dinosaurs ever to live were roaming South America. Although it had some of the same characteristics as raptors that lived in North America and Asia, it was not a close relative. This little hunter is a good example of how dinosaurs filled lots of roles in the environment. Not only were dinosaurs the biggest hunters, they were also among the smallest.

When initially described in 1980, this dinosaur was assigned to the Noasauridae. In 1991 this assignation was deemed invalid and it was determined that Noasaurus belonged to the Abelisauridae. Its unique foot claw has caused a great deal of discussion regarding the evolutionary lineage of this dinosaur. It was assigned to the Abelisauridae primarily on the resemblance of its lower jaw to that of the less gracile jaw of Abelisaurus.

## Links

https://web.archive.org/web/20030405100339/http://www.jpinstitute.com/dinopedia/dinocards/dc\_xxxnoasa.html
https://web.archive.org/web/20080706033013/http://kids.yahoo.com/dinosaurs/398--Noasaurus