''Noasaurus'' ("Northwestern Argentina lizard") is a genus of

ceratosauria Ceratosaurs are members of the clade Ceratosauria, a group of dinosaurs defined as all theropods sharing a more recent common ancestor with ''Ceratosaurus'' than with birds. The oldest known ceratosaur, ''Saltriovenator'', dates to the earliest ...

theropod Theropoda (; ), whose members are known as theropods, is a dinosaur clade that is characterized by hollow bones and three toes and claws on each limb. Theropods are generally classed as a group of saurischian dinosaurs. They were ancestrally c ...

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

genus from the late

Campanian The Campanian is the fifth of six ages of the Late Cretaceous Epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campanian s ...

Maastrichtian The Maastrichtian () is, in the ICS geologic timescale, the latest age (uppermost stage) of the Late Cretaceous Epoch or Upper Cretaceous Series, the Cretaceous Period or System, and of the Mesozoic Era or Erathem. It spanned the interval from ...

(Late

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...

) of

Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, th ...

. The type and only species is ''N. leali''.

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 In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen ...

, ''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.J. F. Bonaparte and J. E. Powell. 1980. "A continental assemblage of tetrapods from the Upper Cretaceous beds of El Brete, northwestern Argentina (Sauropoda-Coelurosauria-Carnosauria-Aves)". ''Mémoires de la Société Géologique de France, Nouvelle Série'' 139: 19-28 The

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...

, PVL 4061, was found in a layer of the

Lecho Formation The Lecho Formation is a geological formation in the Salta Basin of the provinces Jujuy and Salta of northwestern Argentina. Its strata date back to the Early Maastrichtian, and is a unit of the Salta Group. The fine-grained bioturbated sandston ...

Salta Province Salta () is a province of Argentina, located in the northwest of the country. Neighboring provinces are from the east clockwise Formosa, Chaco, Santiago del Estero, Tucumán and Catamarca. It also surrounds Jujuy. To the north it borders Boliv ...

, dating from the late

period, more precisely the early

stage, about seventy million years ago. It consists of a partial skeleton with skull. It contains the

maxilla The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The t ...

, the

quadrate bone The quadrate bone is a skull bone in most tetrapods, including amphibians, sauropsids (reptiles, birds), and early synapsids. In most tetrapods, the quadrate bone connects to the quadratojugal and squamosal bones in the skull, and forms upper ...

, two neck vertebrae, two neck ribs, the centrum of a back vertebra, two hand claws, a finger phalanx and the second right

metatarsal The metatarsal bones, or metatarsus, are a group of five long bones in the foot, located between the tarsal bones of the hind- and mid-foot and the phalanges of the toes. Lacking individual names, the metatarsal bones are numbered from the med ...

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.Agnolin, F.L., Apesteguia, S. and Chiarelli, P. 2004. "The end of a myth: The mysterious ungual claw of ''Noasaurus leali''". ''Journal of Vertebrate Paleontology''. 24(3): 301A-302A In 1999, a neck vertebra found at the site, specimen MACM 622, was identified as oviraptorosaurian, a rare proof that the

Oviraptorosauria Oviraptorosaurs ("egg thief lizards") are a group of feathered maniraptoran dinosaurs from the Cretaceous Period of what are now Asia and North America. They are distinct for their characteristically short, beaked, parrot-like skulls, with or wit ...

had invaded the

Gondwana Gondwana () was a large landmass, often referred to as a supercontinent, that formed during the late Neoproterozoic (about 550 million years ago) and began to break up during the Jurassic period (about 180 million years ago). The final stages ...

n continents. In 2007 however, it was reidentified as a noasaurid vertebra, probably belonging to the ''Noasaurus'' holotype.Agnolin, F.L. and Martinelli, A.G. 2007. "Did oviraptorosaurs (Dinosauria; Theropoda) inhabit Argentina?", ''Cretaceous Research'', 28(5): 785-790

Description

''Noasaurus'' was a small theropod. Gregory S.Paul estimated its length at 1.5 meters (5 ft), its weight at 15 kg (33 lbs).Paul, G.S., 1988, ''Predatory Dinosaurs of the World''. Simon & Schuster, New York, p 285-286 The maxilla bears at least eleven teeth. The teeth are recurved and have serrations at the front and rear edges. The neck is probably long as the neck vertebrae are very elongated. These vertebrae are also strongly vertically compressed with a low

neural spine The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic i ...

and bear long

epipophyses Epipophyses are bony projections of the cervical vertebrae found in archosauromorphs, particularly dinosaurs (including some basal birds). These paired processes sit above the postzygapophyses on the rear of the vertebral neural arch. Their morp ...

, a typical abelisauroid trait. While originally reported to have a raptorial 'sickle claw' on the foot similar to the claws of the more advanced

dromaeosaurids Dromaeosauridae () is a family of feathered theropod dinosaurs. They were generally small to medium-sized feathered carnivores that flourished in the Cretaceous Period. The name Dromaeosauridae means 'running lizards', from Greek ('), meaning ...

, subsequent studies showed that the claw actually came from the hand.Agnolin, F.L. and Chiarelli, P. (2010).
The position of the claws in Noasauridae (Dinosauria: Abelisauroidea) and its implications for abelisauroid manus evolution
" ''Paläontologische Zeitschrift'', published online 19 November 2009. The claw is exceptionally curved, has parallel base sides in top view, and possesses a deep triangular cavity at the base underside.

Classification

''Noasaurus'' is today considered to be a member of the

Ceratosauria Ceratosaurs are members of the clade Ceratosauria, a group of dinosaurs defined as all theropods sharing a more recent common ancestor with ''Ceratosaurus'' than with birds. The oldest known ceratosaur, ''Saltriovenator'', dates to the earliest ...

. Originally, it was seen as a member of the

Coelurosauria Coelurosauria (; from Greek, meaning "hollow tailed lizards") is the clade containing all theropod dinosaurs more closely related to birds than to carnosaurs. Coelurosauria is a subgroup of theropod dinosaurs that includes compsognathids, tyrann ...

. Bonaparte and Powell assigned it to a family of its own, the

Noasauridae Noasauridae is an extinct family of theropod dinosaurs belonging to the group Ceratosauria. They were closely related to the short-armed abelisaurids, although most noasaurids had much more traditional body types generally similar to other ther ...

. In 1988,

Gregory S. Paul Gregory Scott Paul (born December 24, 1954) is an American freelance researcher, author and illustrator who works in paleontology, and more recently has examined sociology and theology. He is best known for his work and research on theropod dino ...

saw them as members of the

Abelisauridae Abelisauridae (meaning "Abel's lizards") is a family (or clade) of ceratosaurian theropod dinosaurs. Abelisaurids thrived during the Cretaceous period, on the ancient southern supercontinent of Gondwana, and today their fossil remains are found ...

and coined a Noasaurinae within that group. He also incorrectly thought they were

Megalosauria Megalosauroidea (meaning 'great/big lizard forms') is a superfamily (or clade) of tetanuran theropod dinosaurs that lived from the Middle Jurassic to the Late Cretaceous period. The group is defined as ''Megalosaurus bucklandii'' and all taxa ...

. Later, the noasaurids were recognised as close relatives of the larger

abelisaurid Abelisauridae (meaning "Abel's lizards") is a family (or clade) of ceratosaurian theropod dinosaurs. Abelisaurids thrived during the Cretaceous period, on the ancient southern supercontinent of Gondwana, and today their fossil remains are found ...

s; they are both derived from the same basal

abelisaur Abelisauroidea is typically regarded as a Cretaceous group, though the earliest abelisauridae remains are known from the Middle Jurassic of Argentina (classified as the species Eoabelisaurus mefi) and possibly Madagascar (fragmentary remains ...

oid ancestor. The following

cladogram A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to d ...

is based on the phylogenetic analysis conducted by Rauhut and Carrano in 2016, showing the relationships of ''

Elaphrosaurus ''Elaphrosaurus'' ( ) is a genus of ceratosaurian theropod dinosaur that lived approximately 154 to 150 million years ago during the Late Jurassic Period in what is now Tanzania in Africa. ''Elaphrosaurus'' was a medium-sized but lightly built m ...

'' among the noasaurids:Rauhut, O.W.M., and Carrano, M.T. (2016). The theropod dinosaur ''Elaphrosaurus bambergi'' Janensch, 1920, from the Late Jurassic of Tendaguru, Tanzania. ''Zoological Journal of the Linnean Society'', (advance online publication)

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 Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last com ...

. 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 ''Masiakasaurus'' is a genus of small predatory noasaurid theropod dinosaurs from the Late Cretaceous of Madagascar. In Malagasy, ''masiaka'' means "vicious"; thus, the genus name means "vicious lizard". The type species, ''Masiakasaurus knopfl ...

'' was discovered. This genus had an unusual down-turned jaw and protruding front teeth which would have been well suited to grasping, and ''

'' may have consumed small vertebrates, fish, or invertebrates. ''Noasaurus'' may have been similar in appearance and lifestyle.

References

Sources