Talenkauen
Encyclopedia
Talenkauen is a genus
of basal
iguanodont
dinosaur
from the Maastrichtian
-age Upper Cretaceous Pari Aike Formation
of Lake Viedma
, Santa Cruz
, Argentina
. It is based on
MPM-10001, a partial articulated skeleton missing the rear part of the skull, the tail, and the hands. Its most unusual feature is the presence of several thin mineralized plates along the sides of the ribs.
in shape and build, but with a proportionally longer neck. The full length of the body is estimated at no more than 4 meters (13 ft). Unlike more derived
iguanodontians, it still had teeth
in the tip of the beak
(premaxilla
ry teeth), and a first toe
. More derived
iguanodonts lose this toe, retaining only the three middle toes. The humerus
has reduced areas for muscle attachment, a featured shared with other South America
n ornithopods like Notohypsilophodon
and Anabisetia
. This and other similarities to South American ornithopods suggests that there may have been a distinct Southern Hemisphere
ornithopod group, but the authors cautioned that all of the evidence together does not permit such an interpretation. The authors, through cladistic analysis, found the new genus to be more basal
than Dryosaurus and Anabisetia, but more derived than Tenontosaurus
and Gasparinisaura
. More recently, the describers of Macrogryphosaurus
found their genus and Talenkauen to be related, and coined the clade
Elasmaria for the two genera.
plates found along the side of the rib cage
. These plates can be long (180 millimeters, or 7.1 in), but are very thin (only 3 millimeters thick [0.1 in]). They were present with at least the first eight rib
s, attaching along the middle portion of a rib and lying flat. Several other dinosaurs are known to have had similar plates, including Hypsilophodon
, Othnielosaurus
, Parksosaurus
, Thescelosaurus
, and Macrogryphosaurus (also from Argentina, but from somewhat older rocks), which may have been related. Because of the fragility of the plates, and the fact that they may not have always turned to bone
in the living animal, they may have been more widespread than currently known. Novas and colleagues suggested that the plates may be homologous
to uncinate process
es, strip-like bony projections found on the ribs of a variety of animals including the tuatara
, crocodile
s, bird
s, and some maniraptora
n theropod dinosaurs. In birds, uncinate processes help to ventilate the lungs, working with rib cage muscles, and Novas and colleagues proposed a similar function for the plates of Talenkauen. This homology was rejected in a more recent study by Richard Butler and Peter Galton because of the plates' form
. The plates were too thin and limited in location to have been very useful as defensive devices.
. Other dinosaurs from the Pari Aike Formation include the giant titanosaurid Puertasaurus
and the predatory neovenatorid Orkoraptor
.
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...
of basal
Basal (phylogenetics)
In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...
iguanodont
Iguanodont
Iguanodonts were herbivorous dinosaurs that lived from the mid-Jurassic to Late Cretaceous. Some members include Camptosaurus, Callovosaurus, Iguanodon, Ouranosaurus, and the hadrosaurids or "duck-billed dinosaurs". Iguanodonts were one of the first groups of dinosaurs to be found...
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 Maastrichtian
Maastrichtian
The Maastrichtian is, in the ICS' geologic timescale, the latest age or upper stage of the Late Cretaceous epoch or Upper Cretaceous series, the Cretaceous period or system, and of the Mesozoic era or erathem. It spanned from 70.6 ± 0.6 Ma to 65.5 ± 0.3 Ma...
-age Upper Cretaceous Pari Aike Formation
Pari Aike Formation
The Pari Aike Formation is a Mesozoic geologic formation. Dinosaur remains are among the fossils that have been recovered from the formation....
of Lake Viedma
Lake Viedma
Viedma Lake , approximately 50 miles long in southern Patagonia near the border between Chile and Argentina...
, Santa Cruz
Santa Cruz Province (Argentina)
Santa Cruz is a province of Argentina, located in the southern part of the country, in Patagonia. It borders Chubut province to the north, and Chile to the west and south. To the east is the Atlantic Ocean...
, 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 is based on
Holotype
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...
MPM-10001, a partial articulated skeleton missing the rear part of the skull, the tail, and the hands. Its most unusual feature is the presence of several thin mineralized plates along the sides of the ribs.
Description
Talenkauen was rather like DryosaurusDryosaurus
Dryosaurus is a genus of an ornithopod dinosaur that lived in the Late Jurassic period. It was an iguanodont . Fossils have been found in the western United States, and were first discovered in the late 19th century...
in shape and build, but with a proportionally longer neck. The full length of the body is estimated at no more than 4 meters (13 ft). Unlike more derived
Derived
In phylogenetics, a derived trait is a trait that is present in an organism, but was absent in the last common ancestor of the group being considered. This may also refer to structures that are not present in an organism, but were present in its ancestors, i.e. traits that have undergone secondary...
iguanodontians, it still had teeth
Tooth
Teeth are small, calcified, whitish structures found in the jaws of many vertebrates that are used to break down food. Some animals, particularly carnivores, also use teeth for hunting or for defensive purposes. The roots of teeth are embedded in the Mandible bone or the Maxillary bone and are...
in the tip of the beak
Beak
The beak, bill or rostrum is an external anatomical structure of birds which is used for eating and for grooming, manipulating objects, killing prey, fighting, probing for food, courtship and feeding young...
(premaxilla
Premaxilla
The incisive bone is the portion of the maxilla adjacent to the incisors. It is a pair of small cranial bones at the very tip of the jaws of many animals, usually bearing teeth, but not always. They are connected to the maxilla and the nasals....
ry teeth), and a first toe
Toe
Toes are the digits of the foot of a tetrapod. Animal species such as cats that walk on their toes are described as being digitigrade. Humans, and other animals that walk on the soles of their feet, are described as being plantigrade; unguligrade animals are those that walk on hooves at the tips of...
. More derived
Derived
In phylogenetics, a derived trait is a trait that is present in an organism, but was absent in the last common ancestor of the group being considered. This may also refer to structures that are not present in an organism, but were present in its ancestors, i.e. traits that have undergone secondary...
iguanodonts lose this toe, retaining only the three middle toes. The humerus
Humerus
The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow....
has reduced areas for muscle attachment, a featured shared with other South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
n ornithopods like Notohypsilophodon
Notohypsilophodon
Notohypsilophodon was a genus of hypsilophodont ornithopod dinosaur. It was described as the only hypsilophodont known from South America, although this assessment is not universally supported, and Gasparinisaura is now believed to have been a hypsilophodont as well...
and Anabisetia
Anabisetia
Anabisetia is a genus of ornithopod dinosaur from the Late Cretaceous Period of Patagonia, South America. It was a small bipedal herbivore, almost seven feet long....
. This and other similarities to South American ornithopods suggests that there may have been a distinct Southern Hemisphere
Southern Hemisphere
The Southern Hemisphere is the part of Earth that lies south of the equator. The word hemisphere literally means 'half ball' or "half sphere"...
ornithopod group, but the authors cautioned that all of the evidence together does not permit such an interpretation. The authors, through cladistic analysis, found the new genus to be more basal
Basal (phylogenetics)
In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...
than Dryosaurus and Anabisetia, but more derived than Tenontosaurus
Tenontosaurus
Tenontosaurus is a genus of medium- to large-sized ornithopod dinosaur. The genus is known from the late Aptian to Albian ages of the middle Cretaceous period sediments of western North America, dating between 115 to 108 million years ago...
and Gasparinisaura
Gasparinisaura
Gasparinisaura is a genus of ornithopod dinosaur from the Late Cretaceous. Its fossils were found in Argentina. The type species, Gasparinisaura cincosaltensis, was described in 1996 by Coria and Salgado. Originally classified as an iguanodont, recent research indicates it is more basal...
. More recently, the describers of Macrogryphosaurus
Macrogryphosaurus
Macrogryphosaurus is a genus of basal iguanodont dinosaur from the Turonian-early Coniacian age Upper Cretaceous Portezuelo Formation of Patagonia, Argentina. It was described by Jorge Calvo and colleagues, with M...
found their genus and Talenkauen to be related, and coined the clade
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...
Elasmaria for the two genera.
Mineralized plates
Talenkauens most distinct feature is a set of smooth, ovoidOval
An oval is any curve resembling an egg or an ellipse, such as a Cassini oval. The term does not have a precise mathematical definition except in one area oval , but it may also refer to:* A sporting arena of oval shape** a cricket field...
plates found along the side of the rib cage
Rib
In vertebrate anatomy, ribs are the long curved bones which form the rib cage. In most vertebrates, ribs surround the chest, enabling the lungs to expand and thus facilitate breathing by expanding the chest cavity. They serve to protect the lungs, heart, and other internal organs of the thorax...
. These plates can be long (180 millimeters, or 7.1 in), but are very thin (only 3 millimeters thick [0.1 in]). They were present with at least the first eight rib
Rib
In vertebrate anatomy, ribs are the long curved bones which form the rib cage. In most vertebrates, ribs surround the chest, enabling the lungs to expand and thus facilitate breathing by expanding the chest cavity. They serve to protect the lungs, heart, and other internal organs of the thorax...
s, attaching along the middle portion of a rib and lying flat. Several other dinosaurs are known to have had similar plates, including Hypsilophodon
Hypsilophodon
Hypsilophodon is an ornithopod dinosaur genus from the Early Cretaceous period of Europe. It was a small bipedal animal with an herbivorous or possibly omnivorous diet...
, Othnielosaurus
Othnielosaurus
Othnielosaurus is a genus of ornithischian dinosaur that lived about 155 to 148 million years ago, during the Late Jurassic-age Morrison Formation of the western United States. It is named in honor of famed paleontologist Othniel Charles Marsh, and was formerly assigned to the genus...
, Parksosaurus
Parksosaurus
Parksosaurus was a genus of hypsilophodont ornithopod dinosaur from the early Maastrichtian-age Upper Cretaceous Horseshoe Canyon Formation of Alberta, Canada. It is based on most of a partially articulated skeleton and partial skull, showing it to have been a small, bipedal, herbivorous dinosaur...
, Thescelosaurus
Thescelosaurus
Thescelosaurus was a genus of small ornithopod dinosaur that appeared at the very end of the Late Cretaceous period in North America. It was a member of the last dinosaurian fauna before the Cretaceous-Tertiary extinction event around 65.5 million years ago...
, and Macrogryphosaurus (also from Argentina, but from somewhat older rocks), which may have been related. Because of the fragility of the plates, and the fact that they may not have always turned to bone
Ossification
Ossification is the process of laying down new bone material by cells called osteoblasts. It is synonymous with bone tissue formation...
in the living animal, they may have been more widespread than currently known. Novas and colleagues suggested that the plates may be homologous
Homology (biology)
Homology forms the basis of organization for comparative biology. In 1843, Richard Owen defined homology as "the same organ in different animals under every variety of form and function". Organs as different as a bat's wing, a seal's flipper, a cat's paw and a human hand have a common underlying...
to uncinate process
Uncinate process
Uncinate process can refer to:* Uncinate process of ethmoid bone* Uncinate process of vertebra - a hook shaped process on the lateral borders of the superior surface of the vertebral bodies of the third to the seventh cervical vertebrae....
es, strip-like bony projections found on the ribs of a variety of animals including the tuatara
Tuatara
The tuatara is a reptile endemic to New Zealand which, though it resembles most lizards, is actually part of a distinct lineage, order Sphenodontia. The two species of tuatara are the only surviving members of its order, which flourished around 200 million years ago. Their most recent common...
, crocodile
Crocodile
A crocodile is any species belonging to the family Crocodylidae . The term can also be used more loosely to include all extant members of the order Crocodilia: i.e...
s, bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
s, and some maniraptora
Maniraptora
Maniraptora is a clade of coelurosaurian dinosaurs which includes the birds and the dinosaurs that were more closely related to them than to Ornithomimus velox. It contains the major subgroups Avialae, Deinonychosauria, Oviraptorosauria and Therizinosauria. Ornitholestes and the Alvarezsauroidea...
n theropod dinosaurs. In birds, uncinate processes help to ventilate the lungs, working with rib cage muscles, and Novas and colleagues proposed a similar function for the plates of Talenkauen. This homology was rejected in a more recent study by Richard Butler and Peter Galton because of the plates' form
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....
. The plates were too thin and limited in location to have been very useful as defensive devices.
Paleobiology
Talenkauen, as a basal iguanodont, would have been a small, bipedal herbivoreHerbivore
Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...
. Other dinosaurs from the Pari Aike Formation include the giant titanosaurid Puertasaurus
Puertasaurus
Puertasaurus is a genus of titanosaurid sauropod that appeared during the Late Cretaceous. It lived in what is now Patagonia. The type species, Puertasaurus reuili, is named in honor of Pablo Puerta and Santiago Reuil, the co-discoverers in January 2001 of the specimen...
and the predatory neovenatorid Orkoraptor
Orkoraptor
Orkoraptor is a genus of large theropod dinosaur from the late Cretaceous Period of Argentina. It is known from incomplete fossil remains including parts of the skull, teeth, tail vertebrae, and a partial tibia. The specialized teeth resemble those of some maniraptoriform theropods, namely the...
.
External links
- National Geographic news release on Talenkauen; the National Geographic Society was one of the supporters of the research on this dinosaur.