''Quilmesaurus'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of carnivorous

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 ...

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

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 ...

n Upper

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 ...

(

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 ...

stage Stage or stages may refer to: Acting * Stage (theatre), a space for the performance of theatrical productions * Theatre, a branch of the performing arts, often referred to as "the stage" * ''The Stage'', a weekly British theatre newspaper * Sta ...

) 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 ...

. It was a member of Abelisauridae, closely related to genera such as ''Carnotaurus''. The only known remains of this genus are leg bones which share certain similarities to a variety of abelisaurids. However, these bones lack unique features, which may render ''Quilmesaurus'' a ''nomen vanum'' (more commonly known as a ''

nomen dubium In binomial nomenclature, a ''nomen dubium'' (Latin for "doubtful name", plural ''nomina dubia'') is a scientific name that is of unknown or doubtful application. Zoology In case of a ''nomen dubium'' it may be impossible to determine whether a s ...

'', or "dubious name").

Discovery and naming

During the late 1980s, a field crew from the Universidad Nacional Tucumán, led by Jaime Powell, uncovered forty kilometres south of Roca City, in

Río Negro province Río Negro (, ''Black River'') is a province of Argentina, located in northern Patagonia. Neighboring provinces are from the south clockwise Chubut, Neuquén, Mendoza, La Pampa and Buenos Aires. To the east lies the Atlantic Ocean. Its capit ...

, southern Argentina, the remains of a theropod near the Salitral Ojo de Agua. In 2001, Rodolfo Aníbal Coria named and described 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 ...

''Quilmesaurus curriei''. The genus name is derived from the Quilme, a

Native American people Native Americans, also known as American Indians, First Americans, Indigenous Americans, and other terms, are the Indigenous peoples of the mainland United States (Indigenous peoples of Hawaii, Alaska and territories of the United States are ...

, and the specific name honours Dr.

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 ...

, a

Canadian Canadians (french: Canadiens) are people identified with the country of Canada. This connection may be residential, legal, historical or cultural. For most Canadians, many (or all) of these connections exist and are collectively the source of ...

theropod specialist. 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 ...

and currently only specimen was designated the collection number MPCA-PV-100, in the Museo Provincial "Carlos Ameghino". It consists of the

distal Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position pro ...

(lower or outermost) half of the right

femur The femur (; ), or thigh bone, is the proximal bone of the hindlimb in tetrapod vertebrates. The head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates with ...

(thighbone), and a complete 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 ...

(inner shinbone), collected from the

Allen Formation The Allen Formation is a geological formation in Argentina whose strata date back to the Late Cretaceous (middle Campanian to early Maastrichtian.Salgado et al., 2007 Dinosaur remains are among the fossils that have been recovered from the formati ...

of the

Malargüe Group The Malargüe Group is a group of geologic formations of the Neuquén Basin of the Mendoza, Neuquén, Río Negro and La Pampa Provinces in northern Patagonia, Argentina. The formations of the Malargüe Group range in age between the middle Camp ...

in the

Neuquén Basin Neuquén Basin ( es, Cuenca Neuquina) is a sedimentary basin covering most of Neuquén Province in Argentina. The basin originated in the Jurassic and developed through alternating continental and marine conditions well into the Tertiary. The bas ...

. These deposits date from the

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 ...

. The specimen came from the

fluvial In geography and geology, fluvial processes are associated with rivers and streams and the deposits and landforms created by them. When the stream or rivers are associated with glaciers, ice sheets, or ice caps, the term glaciofluvial or fluviog ...

sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates) ...

s at the bottom of the Allen Formation. The

taxon In biology, a taxon (back-formation from ''taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular nam ...

is notable as it represents one of the youngest records of a non-

avian Avian may refer to: *Birds or Aves, winged animals *Avian (given name) (russian: Авиа́н, link=no), a male forename Aviation *Avro Avian, a series of light aircraft made by Avro in the 1920s and 1930s *Avian Limited, a hang glider manufacture ...

theropod from Patagonia.

Description

Quilmesaurus and Carnotaurus distal femora

The preserved portion of femur is robust and boxy in shape. The rear face of the tip of the bone possessed prominent

condyles A condyle (;Entry "condyle"
in
lateral condyle (which connected to the fibula) is slightly lower from front-to-back compared to the medial condyle (which connected to the tibia), but it is also wider from side-to-side. An additional finger-like bone spur (an

epicondyle An epicondyle () is a rounded eminence on a bone that lies upon a condyle ('' epi-'', "upon" + ''condyle'', from a root meaning "knuckle" or "rounded articular area"). There are various epicondyles in the human skeleton, each named by its anatomic ...

) would have also been present on the lateral condyle, although this spur is broken off in the only known ''Quilmesaurus'' femur. Just above the medial condyle is a low yet noticeable ridge which juts away from the rest of the bone, towards the midline of the animal's body. This ridge is known as a mesiodistal crest. The area immediately above the condyles possesses a shallow yet wide lowered area known as an extensor groove. Overall the femur is almost identical to that of other abelisaurids. Quilmesaurus curriei

The

proximal Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position pro ...

(upper or innermost) part of the tibia possesses a myriad of complex features. A large and hatchet-shaped structure known as a

cnemial crest The cnemial crest is a crestlike prominence located at the front side of the head of the tibiotarsus or tibia in the legs of many mammals and reptiles (including birds and other dinosaurs). The main extensor muscle of the thigh In human anatomy ...

points forwards at the proximal portion of the tibia. The tip of the cnemial crest is hooked due to the presence of a downward pointing spur, known as a ventral process. Although Coria (2001) considered a hooked cnemial crest to be unique to ''Quilmesaurus'', Valieri ''et al.'' (2007) noted that this structure was also possessed by ''

Aucasaurus ''Aucasaurus'' is a genus of medium-sized abelisaurid theropod dinosaur from Argentina that lived during the Late Cretaceous (Santonian to Campanian stage) of the Anacleto Formation. It was smaller than the related ''Carnotaurus'', although more ...

'' and ''

Majungasaurus ''Majungasaurus'' (; ) is a genus of abelisaurid theropod dinosaur that lived in Madagascar from 70 to 66 million years ago, at the end of the Cretaceous Period (geology), Period, making it one of the last known non-avian dinosaurs that went ex ...

'', as well as the ambiguous abelisaurid ''

Genusaurus ''Genusaurus'' ( ; meaning "knee lizard") is a genus of abelisauroid dinosaur from the Early Cretaceous. Its fossils were found in France. ''Genusaurus'' is believed to have lived during the Albian stage, around 112-100 million years ago. D ...

''. The distal part of the tibia possesses its own projections for connecting to ankle bones, known as

malleoli A malleolus is the bony prominence on each side of the human ankle. Each leg is supported by two bones, the tibia on the inner side (medial) of the leg and the fibula on the outer side (lateral) of the leg. The medial malleolus is the promine ...

. This part has the form of an asymmetrical triangle when seen from the front, with the massive lateral malleolus projecting further distally than the smaller medial malleolus. This combination of distal tibia features was also once presumed to have been unique to ''Quilmesaurus''. However, Valieri ''et al.'' (2007) note that the distal tibia of ''

Rajasaurus ''Rajasaurus'' (meaning "princely lizard") is a genus of carnivorous abelisaurid theropod dinosaur from the Late Cretaceous of India, containing one species: ''Rajasaurus narmadensis''. The bones were excavated from the Lameta Formation in the ...

'' was very similar to that of ''Quilmesaurus''. In 2016, ''Quilmesaurus'' was estimated to have measured in length. This would have made it among the smallest derived abelisaurids, although its legs were proportionally robust like those of ''

Pycnonemosaurus ''Pycnonemosaurus'' (meaning 'dense forest lizard') is a genus of carnivorous theropod dinosaur that belonged to the family Abelisauridae. It was found in the Upper Cretaceous red conglomerate sandstones of the "Cabembe Unit", Mato Grosso, Brazil ...

'', one of the largest members of the family.

Classification

When originally described, Coria could not find a more precise placement for ''Quilmesaurus'' than Theropoda. The presence of a notch in the distal articular surface of the tibia was cited by him as evidence of a possible relationship with basal

Tetanurae Tetanurae (/ˌtɛtəˈnjuːriː/ or "stiff tails") is a clade that includes most theropod dinosaurs, including megalosauroids, allosauroids, tyrannosauroids, ornithomimosaurs, compsognathids and maniraptorans (including birds). Tetanurans are ...

, which would be surprising as ''Quilmesaurus'' lived during a time when South American theropod assemblages were dominated by

s and carcharodontosaurs. Other theropod material has been recovered from within these same

strata In geology and related fields, a stratum ( : strata) is a layer of rock or sediment characterized by certain lithologic properties or attributes that distinguish it from adjacent layers from which it is separated by visible surfaces known as ei ...

and has in 2005 also provisionally been referred to the

. However, in a 2004 abstract (and later a 2007 full paper), Rubén Juárez Valieri ''et al.'' concluded that ''Quilmesaurus'', in view of the hatchet-shaped cnemial crest, was a member 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 ...

. Unlike members of

Megalosauroidea 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 sha ...

, the tibia of ''Quilmesaurus'' does not possess a noticeable anteromedial buttress, and instead it includes a large cnemial crest. ''Quilmesaurus'' is also not a

coelurosaur 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 ...

due to the distal part of the tibia being asymmetrical in shape as well as having a socket for the

astragalus ''Astragalus'' is a large genus of over 3,000 species of herbs and small shrubs, belonging to the legume family Fabaceae and the subfamily Faboideae. It is the largest genus of plants in terms of described species. The genus is native to tempe ...

which is lower than that of coelurosaurs. Finally, the shallow and wide (rather than deep and thin) extensor groove excludes ''Quilmesaurus'' from

Carnosauria 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 ''Gig ...

, as does the possession of parallel upper and lower edges of the cnemial crest. However, some features do support its placement within Ceratosauria. These include a pronounced cnemial crest of the tibia and large mesiodistal crest of the femur. The asymmetrical distal part of the tibia and small socket for the astragalus specifically place it within the family Abelisauridae. The preserved bones share features with various abelisaurid taxa throughout the family, although such similarities are widespread and seemingly pop up at random among the taxa, thus making more specific placement difficult. The hook-like shape of the cnemial crest suggests that ''Quilmesaurus'' was a member of the subfamily

Carnotaurinae Carnotaurinae is a subfamily of the theropod dinosaur family Abelisauridae. It includes the dinosaurs ''Aucasaurus'' (from Argentina), ''Carnotaurus'' (from Argentina). The group was first proposed by American paleontologist Paul Sereno in 1998 ...

, which Sereno (1998) defined to include all abelisaurids closer to ''Carnotaurus'' than to ''Abelisaurus''. Carnotaurini sizes updated

However, the validity of Carnotaurinae has been debated. Although Valieri ''et al.'' (2007) considered the subfamily to include taxa such as ''Majungasaurus'', ''Carnotaurus'', ''Aucasaurus'', and ''Rajasaurus'', other studies have found different results. Tortosa ''et al. (''2014) found that Carnotaurinae was an invalid group, as very few abelisaurids could actually apply to the definition set forth by Sereno. According to their analysis, ''Aucasaurus'' and ''Carnotaurus'' were actually closer to ''Abelisaurus'' than they were to ''Majungasaurus'' and ''Rajasaurus'', thus forcing the latter two taxa to be excluded from the subfamily. ''Quilmesaurus'' was retained as close to ''Aucasaurus'' and ''Carnotaurus'', although Sereno's name and definition of Carnotaurinae was completely demolished. In its place the tribe Carnotaurini was used, which includes all abelisaurids descended from the last common ancestor of ''Aucasaurus'' and ''Carnotaurus''. Tortosa ''et al.'' (2014)'s result has largely been supported over that of Valieri et al. (2007). Filippi ''et al.'' (2016) created a new clade, Furileusauria, to include abelisaurids more closely related to ''Carnotaurus'' than to ''

Ilokelesia ''Ilokelesia'' is an extinct genus of abelisaurid theropod,Coria, R.A.; Salgado, L. & Calvo, J.O. (1991) "Primeros restos de dinosaurios Theropoda del Miembro Huincul, Formación Río Limay (Cretácico Tardío Presenoniano), Neuquén, Argentina." ...

'', ''

Skorpiovenator ''Skorpiovenator'' ("scorpion hunter") is a genus of abelisaurid theropod dinosaur from the Late Cretaceous (Cenomanian to Turonian) Huincul Formation of Argentina. It is one of the most complete and informative abelisaurids yet known, described ...

'', or ''Majungasaurus''. They included ''Quilmesaurus'' among the furileusaurians. Valieri ''et al.'' (2007) were unable to establish a single

autapomorphy 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 ...

(distinctive or unique trait) of the taxon, concluding that ''Quilmesaurus'' were a '' nomen vanum''.

Paleoecology

The Allen Formation is believed to have been a humid coastal environment which gradually transitioned from a freshwater floodplain to marshy estuaries and then shallow lagoons as sea levels rose. A diverse assemblage of aquatic life inhabited the area, including various

fish Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of li ...

frog A frog is any member of a diverse and largely Carnivore, carnivorous group of short-bodied, tailless amphibians composing the order (biology), order Anura (ανοὐρά, literally ''without tail'' in Ancient Greek). The oldest fossil "proto-f ...

s, and

turtle Turtles are an order of reptiles known as Testudines, characterized by a special shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira (side necked turtles) and Cryptodira (hidden necked tu ...

s. More recent intervals of the formation even include a few marine reptiles, such as various

plesiosaurs The Plesiosauria (; Greek: πλησίος, ''plesios'', meaning "near to" and ''sauros'', meaning "lizard") or plesiosaurs are an order or clade of extinct Mesozoic marine reptiles, belonging to the Sauropterygia. Plesiosaurs first appeared ...

including

elasmosaurids Elasmosauridae is an extinct family of plesiosaurs, often called elasmosaurs. They had the longest necks of the plesiosaurs and existed from the Hauterivian to the Maastrichtian stages of the Cretaceous, and represented one of the two groups of p ...

and

polycotylids Polycotylidae is a family of plesiosaurs from the Cretaceous, a sister group to Leptocleididae. Polycotylids first appeared during the Albian stage of the Early Cretaceous, before becoming abundant and widespread during the early Late Cretaceous ...

. Plant life includes

palm trees Palm most commonly refers to: * Palm of the hand, the central region of the front of the hand * Palm plants, of family Arecaceae **List of Arecaceae genera * Several other plants known as "palm" Palm or Palms may also refer to: Music * Palm (ba ...

and

conifers Conifers are a group of cone-bearing seed plants, a subset of gymnosperms. Scientifically, they make up the division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a single extant class, Pinopsida. All extan ...

of the family Podocarpeaceae ("plum pines"), which formed dense forests and wetlands. Quilmesaurus hunting Bonapartesaurus

Remains of land animals were also common in this formation. An indeterminate

rhynchocephalia Rhynchocephalia (; ) is an order of lizard-like reptiles that includes only one living species, the tuatara (''Sphenodon punctatus'') of New Zealand. Despite its current lack of diversity, during the Mesozoic rhynchocephalians were a diverse g ...

n is known, as well as numerous

snake Snakes are elongated, Limbless vertebrate, limbless, carnivore, carnivorous reptiles of the suborder Serpentes . Like all other Squamata, squamates, snakes are ectothermic, amniote vertebrates covered in overlapping Scale (zoology), scales. Ma ...

taxa including the madtsoiids '' Patagoniophis'' and ''

Alamitophis ''Alamitophis'' is a genus of fossil snakes in the extinct family of Madtsoiidae. Its length is estimated at and it probably fed on frogs, lizards, and small mammals. It is found in Australia (Tingamarra Fauna, after which ''A. tingamarra'' is n ...

.'' Other non-dinosaur animals in the area include the

pterosaur Pterosaurs (; from Greek ''pteron'' and ''sauros'', meaning "wing lizard") is an extinct clade of flying reptiles in the order, Pterosauria. They existed during most of the Mesozoic: from the Late Triassic to the end of the Cretaceous (228 to ...

Aerotitan ''Aerotitan'' is a genus of large azhdarchid pterosaur known from the Late Cretaceous period (Maastrichtian stage) of what is now the Allen Formation of the Neuquén Basin in northern Patagonia, Argentina. Discovery and naming The type species ...

'' and a variety of mammals. Dinosaur remains recovered from the Allen Formation include a diverse and abundant assortment of

titanosaur Titanosaurs (or titanosaurians; members of the group Titanosauria) were a diverse group of sauropod dinosaurs, including genera from all seven continents. The titanosaurs were the last surviving group of long-necked sauropods, with taxa still th ...

s (''

Saltasaurus ''Saltasaurus'' (which means "lizard from Salta") is a genus of saltasaurid dinosaur of the Late Cretaceous period of Argentina. Small among sauropods, though still heavy by the standards of modern creatures, ''Saltasaurus'' was characterized by ...

Aeolosaurus ''Aeolosaurus'' (; "Aeolus' lizard") is a genus of titanosaurian sauropod dinosaur from the Late Cretaceous Period of what is now South America. Like most sauropods, it would have been a quadrupedal herbivore with a long neck and tail. ''Aeolosau ...

, Laplatasaurus,

Rocasaurus ''Rocasaurus'' (meaning "General Roca lizard") is a genus of titanosaurian sauropod that lived in South America. ''Rocasaurus'' was discovered in Argentina in 2000, within the Allen Formation which is dated to be middle Campanian to early Maastr ...

,'' etc.) and a

hadrosaurid Hadrosaurids (), or duck-billed dinosaurs, are members of the ornithischian family Hadrosauridae. This group is known as the duck-billed dinosaurs for the flat duck-bill appearance of the bones in their snouts. The ornithopod family, which inclu ...

of dubious validity ('' Willinakaqe''). Theropods other than ''Quilmesaurus'' were also present; they include the large

unenlagiine Unenlagiinae is a subfamily of long-snouted paravian theropods. They are traditionally considered to be members of Dromaeosauridae, though some authors place them into their own family, Unenlagiidae, alongside the subfamily Halszkaraptorinae. ...

dromaeosaurid 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 ...

Austroraptor ''Austroraptor'' ( ) is a genus of large dromaeosaurid dinosaur that lived during the Late Cretaceous Period in what is now Argentina. ''Austroraptor'' was a large-sized, moderately-built, ground-dwelling, bipedal carnivore, estimated at in len ...

'', a basal

ornithuran Ornithurae (meaning "bird tails" in Greek) is a natural group which includes the common ancestor of ''Ichthyornis'', ''Hesperornis'', and all modern birds as well as all other descendants of that common ancestor. Classification Ernst Haeckel co ...

bird (''

Limenavis ''Limenavis'' is a prehistoric bird genus from the Late Cretaceous. It lived about 70 million years ago, around the Campanian-Maastrichtian boundary. Known from several broken bones, the remains of the only known species ''Limenavis patagonica'' ...

''), and a cimolopterygid bird (''

Lamarqueavis ''Lamarqueavis'' is an extinct genus of prehistoric birds from the Cimolopterygidae known from Late Cretaceous-aged rocks from Argentina, Canada, and the United States. The type species, ''L. australis'', was named in 2010 and is based on the ho ...

''). A tooth has been referred to the family

Carcharodontosauridae Carcharodontosauridae (carcharodontosaurids; from the Greek καρχαροδοντόσαυρος, ''carcharodontósauros'': "shark-toothed lizards") is a group of carnivorous theropod dinosaurs. In 1931, Ernst Stromer named Carcharodontosauridae ...

; this tooth is one of the most recent carcharodontosaurid fossils found as more well known members of this family (''

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 ...

'', ''

Mapusaurus ''Mapusaurus'' () was a giant carcharodontosaurid carnosaurian dinosaur from the early Late Cretaceous (early Turonian stage), approximately 93.9 to 89.6 million years ago, of what is now Argentina. Discovery ''Mapusaurus'' was excavated be ...

'') lived millions of years earlier in the Cretaceous. Indeterminate

nodosaurid Nodosauridae is a family of ankylosaurian dinosaurs, from the Late Jurassic to the Late Cretaceous period in what is now North America, South America, Europe, and Asia. Description Nodosaurids, like their close relatives the ankylosaurids, wer ...

remains have also been found at this formation, consisting of

vertebra 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 ...

osteoderm Osteoderms are bony deposits forming scales, plates, or other structures based in the dermis. Osteoderms are found in many groups of extant and extinct reptiles and amphibians, including lizards, crocodilians, frogs, temnospondyls (extinct amp ...

s, a femur, and a tooth. The Allen Formation is also notable for the high amount of sauropod eggs discovered there. Nesting grounds have been discovered in the bajo de Santa Rosa area of the upper Allen Formation. Some (but not all) of these eggs were designated as the

oogenus Egg fossils are the fossilized remains of eggs laid by ancient animals. As evidence of the physiological processes of an animal, egg fossils are considered a type of trace fossil. Under rare circumstances a fossil egg may preserve the remains of t ...

'' Sphaerovum''. The structure of their eggshells indicate that they were laid in a very damp environment.

References

{{Taxonbar, from=Q141626 Brachyrostrans Late Cretaceous dinosaurs of South America Cretaceous Argentina Fossils of Argentina Allen Formation Fossil taxa described in 2001 Taxa named by Rodolfo Coria Nomina dubia

Discovery and naming

Description

Classification

Paleoecology

See also

References