Mapusaurus
Encyclopedia
Mapusaurus was a giant carnosauria
n dinosaur
from the early Late Cretaceous
(Cenomanian
stage) of what is now Argentina
. It was similar in size to its close relative Giganotosaurus
, with the largest known individuals estimated as over 10.2 metres (33.5 ft) in length and weighing approximately 3 metric tons (3.3 ST). Mapusaurus was excavated between 1997 and 2001, by the Argentinian-Canadian Dinosaur Project, from an exposure of the Huincul Formation
(Rio Limay Group, Cenomanian
) at Canadon de Gato. It was described and named by paleontologists Rodolfo Coria
and Phil Currie
in 2006.
The name Mapusaurus is derived from the Mapuche
word Mapu, meaning 'of the Land' or 'of the Earth' and the Greek
sauros, meaning 'lizard
'. The type species
, Mapusaurus roseae, is named for both the rose
-colored rocks, in which the fossils were found and for Rose Letwin
, who sponsored the expeditions which recovered these fossil
s.
Cladistic analysis carried out by Coria and Currie definitively showed that Mapusaurus is nested within the clade
Carcharodontosauridae
. The authors noted that the structure of the femur
suggests a closer relationship with Giganotosaurus than either taxon
shares with Carcharodontosaurus
. They created a new monophyletic taxon based on this relationship, the subfamily
Giganotosaurinae, defined as all carcharodontosaurids closer to Giganotosaurus and Mapusaurus than to Carcharodontosaurus. They tentatively included the genus Tyrannotitan
in this new subfamily, pending publication of more detailed descriptions of the known specimens of that form.
remains of Mapusaurus were discovered in a bone bed
containing at least seven individuals of various growth stages
. Coria and Currie speculated that this may represent a long term, possibly coincidental accumulation of carcasses (some sort of predator trap
) and may provide clues about Mapusaurus behavior. Other known theropod bone beds include the Allosaurus
-dominated Cleveland Lloyd Dinosaur Quarry
of Utah
, an Albertosaurus
bone bed from Alberta
and a Daspletosaurus
bone bed from Montana
.
Paleontologist Rodolfo Coria, of the Museo Carmen Funes
, contrary to his published article, repeated in a press-conference earlier suggestions that this congregation of fossil bones may indicate that Mapusaurus hunted in groups and worked together to take down large prey, such as the immense sauropod Argentinosaurus
. If so, this would be the first substantive evidence of gregarious behavior by large theropods other than Tyrannosaurus
, although whether they might have hunted in organized packs (as wolves do) or simply attacked in a mob, is unknown. The authors interpreted the depositional environment
of the Huincul Formation at the Canadon de Gato locality as a freshwater paleochannel deposit, "laid down by an ephemeral or seasonal stream in a region with arid or semi-arid climate". This bone bed is especially interesting, in light of the overall scarcity of fossilized bone within the Huincul Formation.
for the genus
and type species
, Mapusaurus roseae, is an isolated right nasal (MCF-PVPH-108.1, Museo Carmen Funes, Paleontología de Vertebrados, Plaza Huincul, Neuquén). Twelve paratypes have been designated, based on additional isolated skeletal elements. Taken together, the many individual elements recovered from the Mapusaurus bone bed represent most of the skeleton.
Coria and Currie diagnosed Mapusaurus as follows: "Mapusaurus n. gen. is a carcharodontosaurid
theropod whose skull
differs from Giganotosaurus in having thick, rugose unfused nasals that are narrower anterior to the nasal/maxilla
/lacrimal
junction; larger extension of the antorbital fossa
onto maxilla; smaller maxillary fenestra; wider bar (interfenestral strut) between antorbital and maxillary fenestrae; lower, flatter lacrimal horn
; transversely wider prefrontal in relation to lacrimal width; ventrolaterally curving lateral margin of the palpebral
; shallow interdental plate
s; higher position of Meckelian canal; more posteriorly sloping anteroventral margin of dentary. Mapusaurus roseae is unique in that the upper quadratojugal
process of jugal
splits into two prongs; small anterior mylohyoid
foramen
positioned above dentary contact with splenial
; second and third metacarpals fused; humerus
with broad distal end and little separation between condyles; brevis fossa of ilium extends deeply into excavation dorsal to ischial peduncle. It also differs from Giganotosaurus in having conical
, slightly curving cervical
epipophyses that taper distally; axial posterior zygapohyses joined on midline; smaller and less elaborate prespinal lamina
on midline of cervicals; remarkably sharp dorsal
margin of cervical neural spines; tall, wider neural spines; curved ischiatic shaft; more slender fibula."
Carnosauria
Carnosauria is a group of large predatory dinosaurs that lived during the Jurassic and Cretaceous periods. While it originally contained a wide assortment of giant theropods that were not closely related, the group has since been defined to encompass only the allosaurs and their closest kin...
n dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
from the early Late Cretaceous
Late Cretaceous
The Late Cretaceous is the younger of two epochs into which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...
(Cenomanian
Cenomanian
The Cenomanian is, in the ICS' geological timescale the oldest or earliest age of the Late Cretaceous epoch or the lowest stage of the Upper Cretaceous series. An age is a unit of geochronology: it is a unit of time; the stage is a unit in the stratigraphic column deposited during the corresponding...
stage) of what is now Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
. It was similar in size to its close relative Giganotosaurus
Giganotosaurus
Giganotosaurus is a genus of carcharodontosaurid dinosaur that lived around 97 million years ago during the early Cenomanian stage of the Late Cretaceous Period. It included some of the largest known terrestrial carnivores, slightly larger than the largest Tyrannosaurus, but smaller than the...
, with the largest known individuals estimated as over 10.2 metres (33.5 ft) in length and weighing approximately 3 metric tons (3.3 ST). Mapusaurus was excavated between 1997 and 2001, by the Argentinian-Canadian Dinosaur Project, from an exposure of the Huincul Formation
Huincul Formation
The Huincul Formation is a geologic formation that outcrops in Río Negro and Neuquén provinces of Argentina. It is the second formation in the Río Limay Subgroup, the oldest subgroup within the Neuquén Group...
(Rio Limay Group, Cenomanian
Cenomanian
The Cenomanian is, in the ICS' geological timescale the oldest or earliest age of the Late Cretaceous epoch or the lowest stage of the Upper Cretaceous series. An age is a unit of geochronology: it is a unit of time; the stage is a unit in the stratigraphic column deposited during the corresponding...
) at Canadon de Gato. It was described and named by paleontologists Rodolfo Coria
Rodolfo Coria
Dr. Rodolfo Coria is an Argentine paleontologist.He is best known for having directed the field study and co-naming of the Argentinosaurus in 1993, and the Giganotosaurus , in 1996 among other landmark South American dinosaurs...
and Phil Currie
Phil Currie
Philip John Currie, AOE 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 2006.
The name Mapusaurus is derived from the Mapuche
Mapuche
The Mapuche are a group of indigenous inhabitants of south-central Chile and southwestern Argentina. They constitute a wide-ranging ethnicity composed of various groups who shared a common social, religious and economic structure, as well as a common linguistic heritage. Their influence extended...
word Mapu, meaning 'of the Land' or 'of the Earth' and the Greek
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...
sauros, meaning 'lizard
Lizard
Lizards are a widespread group of squamate reptiles, with nearly 3800 species, ranging across all continents except Antarctica as well as most oceanic island chains...
'. The type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
, Mapusaurus roseae, is named for both the rose
Rose
A rose is a woody perennial of the genus Rosa, within the family Rosaceae. There are over 100 species. They form a group of erect shrubs, and climbing or trailing plants, with stems that are often armed with sharp prickles. Flowers are large and showy, in colours ranging from white through yellows...
-colored rocks, in which the fossils were found and for Rose Letwin
Gordon Letwin
James Gordon Letwin is an American software developer and one of the original twelve Microsoft employees.Prior to joining Microsoft, he worked for Heathkit, on HDOS and Benton Harbor Basic....
, who sponsored the expeditions which recovered these fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
s.
Classification
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
Carcharodontosauridae
Carcharodontosauridae
Carcharodontosaurids were a group of carnivorous theropod dinosaurs. In 1931 Ernst Stromer named Carcharodontosauridae as a family, in modern paleontology this name indicates a clade within Carnosauria...
. The authors noted that the structure of the femur
Femur
The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...
suggests a closer relationship with Giganotosaurus than either taxon
Taxon
|thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...
shares with Carcharodontosaurus
Carcharodontosaurus
Carcharodontosaurus was a gigantic carnivorous carcharodontosaurid dinosaur that lived around 100 to 93 million years ago, during the late Albian to early Cenomanian stages of the mid-Cretaceous Period...
. They created a new monophyletic taxon based on this relationship, the subfamily
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Giganotosaurinae, defined as all carcharodontosaurids closer to Giganotosaurus and Mapusaurus than to Carcharodontosaurus. They tentatively included the genus Tyrannotitan
Tyrannotitan
Tyrannotitan is a genus of huge bipedal carnivorous dinosaur of the carcharodontosaurid family from the Aptian stage of the early Cretaceous period, discovered in Argentina. It is closely related to other giant predators like Giganotosaurus and Carcharodontosaurus...
in this new subfamily, pending publication of more detailed descriptions of the known specimens of that form.
Paleobiology
The fossilFossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
remains of Mapusaurus were discovered in a bone bed
Bone bed
A bone bed is any geological stratum or deposit that contains bones of whatever kind. Inevitably, such deposits are sedimentary in nature. Not a formal term, it tends to be used more to describe especially dense collections...
containing at least seven individuals of various growth stages
Ontogeny
Ontogeny is the origin and the development of an organism – for example: from the fertilized egg to mature form. It covers in essence, the study of an organism's lifespan...
. Coria and Currie speculated that this may represent a long term, possibly coincidental accumulation of carcasses (some sort of predator trap
Predator trap
A predator trap is a natural hazard such as a tar pit. Predators would become attracted to struggling animals that have become entrapped in viscous or glutinous material, such as a heavy sedimentary deposit or tar and, in the process, become entrapped themselves...
) and may provide clues about Mapusaurus behavior. Other known theropod bone beds include the Allosaurus
Allosaurus
Allosaurus is a genus of large theropod dinosaur that lived 155 to 150 million years ago during the late Jurassic period . The name Allosaurus means "different lizard". It is derived from the Greek /allos and /sauros...
-dominated Cleveland Lloyd Dinosaur Quarry
Cleveland Lloyd Dinosaur Quarry
The Cleveland Lloyd Dinosaur Quarry National Natural Landmark, located in The San Rafael Swell, near Cleveland, Utah contains the densest concentration of Jurassic dinosaur fossils ever found. Well over 15,000 bones have been excavated from this Jurassic 'predator trap' and there are many...
of Utah
Utah
Utah is a state in the Western United States. It was the 45th state to join the Union, on January 4, 1896. Approximately 80% of Utah's 2,763,885 people live along the Wasatch Front, centering on Salt Lake City. This leaves vast expanses of the state nearly uninhabited, making the population the...
, an Albertosaurus
Albertosaurus
Albertosaurus is a genus of tyrannosaurid theropod dinosaur that lived in western North America during the Late Cretaceous Period, more than 70 million years ago. The type species, A. sarcophagus, was apparently restricted in range to the modern-day Canadian province of Alberta, after which...
bone bed from Alberta
Alberta
Alberta is a province of Canada. It had an estimated population of 3.7 million in 2010 making it the most populous of Canada's three prairie provinces...
and a Daspletosaurus
Daspletosaurus
Daspletosaurus is a genus of tyrannosaurid theropod dinosaur that lived in western North America between 77 and 74 million years ago, during the Late Cretaceous Period. Fossils of the only named species were found in Alberta, although other possible species from Alberta and Montana await...
bone bed from Montana
Montana
Montana is a state in the Western United States. The western third of Montana contains numerous mountain ranges. Smaller, "island ranges" are found in the central third of the state, for a total of 77 named ranges of the Rocky Mountains. This geographical fact is reflected in the state's name,...
.
Paleontologist Rodolfo Coria, of the Museo Carmen Funes
Museo Carmen Funes
Museo Municipal Carmen Funes, or, the Carmen Funes Municipal Museum, is a museum of paleontology in Plaza Huincul, Neuquén Province, Argentina...
, contrary to his published article, repeated in a press-conference earlier suggestions that this congregation of fossil bones may indicate that Mapusaurus hunted in groups and worked together to take down large prey, such as the immense sauropod Argentinosaurus
Argentinosaurus
Argentinosaurus is a genus of titanosaur sauropod dinosaur first discovered by Guillermo Heredia in Argentina. The generic name refers to the country in which it was discovered...
. If so, this would be the first substantive evidence of gregarious behavior by large theropods other than Tyrannosaurus
Tyrannosaurus
Tyrannosaurus meaning "tyrant," and sauros meaning "lizard") is a genus of coelurosaurian theropod dinosaur. The species Tyrannosaurus rex , commonly abbreviated to T. rex, is a fixture in popular culture. It lived throughout what is now western North America, with a much wider range than other...
, although whether they might have hunted in organized packs (as wolves do) or simply attacked in a mob, is unknown. The authors interpreted the depositional environment
Sedimentary depositional environment
In geology, sedimentary depositional environment describes the combination of physical, chemical and biological processes associated with the deposition of a particular type of sediment and, therefore, the rock types that will be formed after lithification, if the sediment is preserved in the rock...
of the Huincul Formation at the Canadon de Gato locality as a freshwater paleochannel deposit, "laid down by an ephemeral or seasonal stream in a region with arid or semi-arid climate". This bone bed is especially interesting, in light of the overall scarcity of fossilized bone within the Huincul Formation.
Technical description and diagnosis
The designated holotypeHolotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
for the genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
and type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
, Mapusaurus roseae, is an isolated right nasal (MCF-PVPH-108.1, Museo Carmen Funes, Paleontología de Vertebrados, Plaza Huincul, Neuquén). Twelve paratypes have been designated, based on additional isolated skeletal elements. Taken together, the many individual elements recovered from the Mapusaurus bone bed represent most of the skeleton.
Coria and Currie diagnosed Mapusaurus as follows: "Mapusaurus n. gen. is a carcharodontosaurid
Carcharodontosauridae
Carcharodontosaurids were a group of carnivorous theropod dinosaurs. In 1931 Ernst Stromer named Carcharodontosauridae as a family, in modern paleontology this name indicates a clade within Carnosauria...
theropod whose skull
Skull
The skull is a bony structure in the head of many animals that supports the structures of the face and forms a cavity for the brain.The skull is composed of two parts: the cranium and the mandible. A skull without a mandible is only a cranium. Animals that have skulls are called craniates...
differs from Giganotosaurus in having thick, rugose unfused nasals that are narrower anterior to the nasal/maxilla
Maxilla
The maxilla is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible , which is also a fusion of two halves at the mental symphysis. Sometimes The maxilla (plural: maxillae) is a fusion of two bones along the palatal fissure that form the upper...
/lacrimal
Lacrimal bone
The lacrimal bone, the smallest and most fragile bone of the face, is situated at the front part of the medial wall of the orbit. It has two surfaces and four borders.-Lateral or orbital surface:...
junction; larger extension of the antorbital fossa
Fossa (anatomy)
In anatomical terminology, fossa has come to mean a depression or hollow, in general, in a bone. Other parts of the body may be involved, for example, the antecubital fossa...
onto maxilla; smaller maxillary fenestra; wider bar (interfenestral strut) between antorbital and maxillary fenestrae; lower, flatter lacrimal horn
Horn (anatomy)
A horn is a pointed projection of the skin on the head of various animals, consisting of a covering of horn surrounding a core of living bone. True horns are found mainly among the ruminant artiodactyls, in the families Antilocapridae and Bovidae...
; transversely wider prefrontal in relation to lacrimal width; ventrolaterally curving lateral margin of the palpebral
Palpebral (bone)
The palpebral bone is a small dermal bone found in the region of the eye socket in a variety of animals, including crocodilians and ornithischian dinosaurs. In ornithischians, it can form a prong that projects from the front upper corner of the orbit...
; shallow interdental plate
Interdental plate
The interdental plate refers to the bone-filled mesial-distal region between the teeth. The word "interdental" is a combination of "inter" + "dental" which originated in approximately 1870...
s; higher position of Meckelian canal; more posteriorly sloping anteroventral margin of dentary. Mapusaurus roseae is unique in that the upper quadratojugal
Quadratojugal
The quadratojugal is a small jaw bone that is present in most amphibians, reptiles, and birds, but has been lost in mammals. It is connected to the jugal as well as other bones, though these may vary with species....
process of jugal
Jugal
The jugal is a skull bone found in most reptiles, amphibians, and birds. In mammals, the jugal is often called the malar or Zygomatic. It is connected to the quadratojugal and maxilla, as well as other bones, which may vary by species....
splits into two prongs; small anterior mylohyoid
Mylohyoid
Mylohyoid can refer to:* Mylohyoid muscle* Mylohyoid line* Mylohyoid nerve* Mylohyoid branch of inferior alveolar artery* Mylohyoid groove...
foramen
Foramen
In anatomy, a foramen is any opening. Foramina inside the body of humans and other animals typically allow muscles, nerves, arteries, veins, or other structures to connect one part of the body with another.-Skull:...
positioned above dentary contact with splenial
Splenial
The splenial is a small bone in the lower jaw of reptiles, amphibians and birds, usually located on the lingual side between the angular and suprangular....
; second and third metacarpals fused; humerus
Humerus
The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow....
with broad distal end and little separation between condyles; brevis fossa of ilium extends deeply into excavation dorsal to ischial peduncle. It also differs from Giganotosaurus in having conical
Cone (geometry)
A cone is an n-dimensional geometric shape that tapers smoothly from a base to a point called the apex or vertex. Formally, it is the solid figure formed by the locus of all straight line segments that join the apex to the base...
, slightly curving cervical
Neck
The neck is the part of the body, on many terrestrial or secondarily aquatic vertebrates, that distinguishes the head from the torso or trunk. The adjective signifying "of the neck" is cervical .-Boner anatomy: The cervical spine:The cervical portion of the human spine comprises seven boney...
epipophyses that taper distally; axial posterior zygapohyses joined on midline; smaller and less elaborate prespinal lamina
Lamina of the vertebral arch
The laminæ are two broad plates, extending dorsally and medially from the pedicles, fusing to complete the roof of the vertebral arch.Their upper borders and the lower parts of their anterior surfaces are rough for the attachment of the ligamenta flava....
on midline of cervicals; remarkably sharp dorsal
Dorsum (biology)
In anatomy, the dorsum is the upper side of animals that typically run, fly, or swim in a horizontal position, and the back side of animals that walk upright. In vertebrates the dorsum contains the backbone. The term dorsal refers to anatomical structures that are either situated toward or grow...
margin of cervical neural spines; tall, wider neural spines; curved ischiatic shaft; more slender fibula."