''Murusraptor'' ("wall thief") is a genus of carnivorous

megaraptora Megaraptora is a clade of carnivorous Tetanurae, tetanuran theropod dinosaurs with controversial relations to other theropods. Its Derived (phylogenetics), derived members, the Megaraptoridae are noted for their elongated hand claws and proporti ...

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 ...

from the Sierra Barrosa Formation, part of the

Neuquén Group The Neuquén Group is a group of geologic formations found in Argentina. Rocks in the Neuquén Group fall within the Cenomanian to early Campanian stages of the Late Cretaceous Period. It overlies the older Lohan Cura Formation and is itself over ...

Patagonia Patagonia () refers to a geographical region that encompasses the southern end of South America, governed by Argentina and Chile. The region comprises the southern section of the Andes Mountains with lakes, fjords, temperate rainforests, and gl ...

, in

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 ...

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the southe ...

. It is known from a single specimen that consists of a partial skull, ribs, partial pelvis, leg and other assorted skeletal elements.

Description

The holotype of ''Murusraptor'' is estimated to be , but is considered to be an immature specimen, as the

cranial sutures In anatomy, fibrous joints are joints connected by fibrous tissue, consisting mainly of collagen Collagen () is the main structural protein in the extracellular matrix found in the body's various connective tissues. As the main component of c ...

in its

braincase In human anatomy, the neurocranium, also known as the braincase, brainpan, or brain-pan is the upper and back part of the skull, which forms a protective case around the brain. In the human skull, the neurocranium includes the calvaria or skul ...

have not yet disappeared; this indicates it would have been potentially larger. Analysis of the skeleton further revealed anatomical features as-yet unseen in Megaraptora, particularly in the

skull The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, the ...

and

hips In vertebrate anatomy, hip (or "coxa"Latin ''coxa'' was used by Celsus in the sense "hip", but by Pliny the Elder in the sense "hip bone" (Diab, p 77) in medical terminology) refers to either an anatomical region or a joint. The hip region is ...

. Analysis of the posterior of the skull indicates that, possibly like the related ''

Megaraptor ''Megaraptor'' () is a genus of large theropod dinosaur that lived in the ages of the Late Cretaceous. Its fossils have been discovered in the Patagonian Portezuelo Formation of Argentina, South America. Initially thought to have been a giant dr ...

'', ''Murusraptor'' likely had an elongated and narrow snout. The sacral ribs are hollow. Coria & Currie established some distinguishing traits of ''Murusraptor''. The front branch of the lacrimal is longer than the descending branch is high. In the lower jaw, the surangular shows a bone shelf at its outer side, under the groove between the front surangular opening and the notch for the upper rear branch of the dentary, contributing to the side joint. The sacral ribs are hollow and tube-like. The ischia are short, transversely flattened and vertically slightly widened. These last two traits are unequivocal

autapomorphies In phylogenetics, an autapomorphy is a distinctive feature, known as a derived trait, that is unique to a given taxon. That is, it is found only in one taxon, but not found in any others or outgroup taxa, not even those most closely related to t ...

, unique derived qualities, as they are unique within the entire

Theropoda 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 ca ...

Furthermore, a unique combination of traits is present that are in themselves not unique. In the braincase, the ''processus basipterygoidei'' are situated at the front underside of the basisphenoid while the entrance of the deep depression of the ''recessus basisphenoideus'' is directed obliquely upwards and to the rear. The basisphenoid shows a shallow wide notch between the ''tubera basilaria'' and the ''processus basipterygoidei''. The chevron bones are rather straight. The braincase of ''Murusraptor'' shows more similarities to non-maniraptoran

coelurosaurs 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, tyran ...

, particularly

tyrannosaurids Tyrannosauridae (or tyrannosaurids, meaning "tyrant lizards") is a family (biology), family of coelurosaurian Theropoda, theropod dinosaurs that comprises two subfamilies containing up to thirteen genus, genera, including the eponymous ''Tyrannos ...

, than to non-coelurosaurs such as

allosaurids Allosauridae is a family of medium to large bipedal, carnivorous allosauroid theropod dinosaurs from the Late Jurassic. Allosauridae is a fairly old taxonomic group, having been first named by the American paleontologist Othniel Charles Marsh i ...

or ceratosaurids, although its Reptile Encephalization Quotient was nonetheless within the range of allosauroids such as ''

Allosaurus ''Allosaurus'' () is a genus of large carnosaurian theropod dinosaur that lived 155 to 145 million years ago during the Late Jurassic epoch (Kimmeridgian to late Tithonian). The name "''Allosaurus''" means "different lizard" alluding to ...

'', ''

Giganotosaurus ''Giganotosaurus'' ( ) is a genus of theropod dinosaur that lived in what is now Argentina, during the early Cenomanian age of the Late Cretaceous period, approximately 99.6 to 95 million years ago. The holotype specimen was discovered in the ...

'', and ''

Sinraptor ''Sinraptor'' is a genus of metriacanthosaurid theropod dinosaur from the Late Jurassic. The name ''Sinraptor'' comes from the Latin prefix "Sino", meaning Chinese, and "raptor" meaning robber. The specific name ''dongi'' honours Dong Zhiming. ...

'' and its neurosensorial capabilities were thus most likely inferior to those of tyrannosaurids.

Discovery and naming

In 2001, Sergio Saldivia, preparator at the ''

Museo Carmen Funes Museo Municipal Carmen Funes, or, the Carmen Funes Municipal Museum, is a museum of paleontology in Plaza Huincul, Neuquén Province, Argentina. It is best known for its collection of dinosaur fossils, including the only specimen of the largest re ...

'', thirty kilometres northeast of

Plaza Huincul Plaza Huincul is a small city in Neuquen province, with a population of around 13,000 people, located in southwestern Argentina. It is approximately south-west from the capital, Buenos Aires. Plaza Huincul is located in the middle of the desert ...

in a canyon wall discovered the skeleton of a theropod dinosaur new to science. During that year and 2002 the remains were secured. In 2016, 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 ...

''Murusraptor barrosaensis'' was named and described by Rodolfo Anibal Coria and

Philip John Currie Philip John Currie (born March 13, 1949) is a Canadian palaeontologist and museum curator who helped found the Royal Tyrrell Museum of Palaeontology in Drumheller, Alberta and is now a professor at the University of Alberta in Edmonton. In the ...

. The generic name is a combination of the

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

''murus'', "wall", a reference to the canyon wall, and ''raptor'', "seizer". The specific name refers to the provenance from the Sierra Barrosa Formation. 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 ...

, MCF-PVPH-411, was found in a layer of the Sierra Barrosa Formation dating from the

Coniacian The Coniacian is an age or stage in the geologic timescale. It is a subdivision of the Late Cretaceous Epoch or Upper Cretaceous Series and spans the time between 89.8 ± 1 Ma and 86.3 ± 0.7 Ma (million years ago). The Coniacian is preceded by t ...

. It consists of a partial skeleton with skull, of an immature individual. The skeletal elements recovered for this

type specimen In biology, a type is a particular wiktionary:en:specimen, specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to a ...

of ''Murusraptor'' include a partial skull consisting of a complete braincase with frontals and parietals, right lacrimal, prefrontal, postorbital, quadrate, pterygoid, epipterygoid and ectopterygoid, thirty-one teeth, the rear elements of the right

lower jaw In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bone ...

, twelve vertebrae from the back, sacrum and tail, eleven thoracic ribs, a single haemal arch or chevron bone, several gastralia, a third manual ungual, complete left ilium, part of a right ilium, proximal ends of both

pubic bone In vertebrates, the pubic region ( la, pubis) is the most forward-facing ( ventral and anterior) of the three main regions making up the coxal bone. The left and right pubic regions are each made up of three sections, a superior ramus, inferior ...

s, distal ends of the ischia, the right

tibia The tibia (; ), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outside of the tibia); it connects ...

, and a

calcaneum In humans and many other primates, the calcaneus (; from the Latin ''calcaneus'' or ''calcaneum'', meaning heel) or heel bone is a bone of the tarsus of the foot which constitutes the heel. In some other animals, it is the point of the hock. St ...

Classification

''Murusraptor'' is a megaraptoran, one of a group of large predatory dinosaurs whose exact classification remains disputed. Once believed to be dromaeosaurids, they have since been classified as either

allosauroid Allosauroidea is a superfamily or clade of theropod dinosaurs which contains four families — the Metriacanthosauridae, Allosauridae, Carcharodontosauridae, and Neovenatoridae. Allosauroids, alongside the family Megalosauroidea, were among th ...

carnosaurs Carnosauria is an extinct large group of predatory dinosaurs that lived during the Jurassic and Cretaceous periods. Starting from the 1990s, scientists have discovered some very large carnosaurs in the carcharodontosaurid family, such as ''Gi ...

or as

tyrannosauroid Tyrannosauroidea (meaning 'tyrant lizard forms') is a superfamily (or clade) of coelurosaurian theropod dinosaurs that includes the family Tyrannosauridae as well as more basal relatives. Tyrannosauroids lived on the Laurasian supercontinent b ...

coelurosaurs. While the discovery of ''Murusraptor'' does not clarify as of yet the placement of this group of theropods, the specimen does add further clarity to some aspects of megaraptoran anatomy and potentially, eventual classification of the Megaraptora within the theropod evolutionary tree.

Paleobiology

Pathologies

The type specimen of ''Murusraptor'' shows signs of severe infections around the left side of its braincase. Two tooth marks, likely inflicted by another theropod, are visible in front of and below the nuchal crest on the skull. Due to the infections, the entire left side of the

occiput The occipital bone () is a cranial dermal bone and the main bone of the occiput (back and lower part of the skull). It is trapezoidal in shape and curved on itself like a shallow dish. The occipital bone overlies the occipital lobes of the cereb ...

, the back of the head, was deformed. Some of the ribs were also infected. Whether or not this contributed to the theropod's death remains unknown.

References