Tiarajudens
Encyclopedia
Tiarajudens is an extinct genus
of saber-toothed herbivorous anomodont
which lived during the middle Permian
period (Capitanian
stage) in what is now Rio Grande do Sul
, Brazil
. It is known from the holotype
UFRGS PV393P, a nearly complete skull
. The type species
T. eccentricus was named in 2011
.
teeth. These teeth are unlike the tusks of dicynodont
s, a later group of anomodonts. Twenty-one high-crowned
teeth are present on either side of the upper jaw, including spoon-shaped incisors. Wide palatal
teeth are also present. The top and bottom sets of teeth fit closely together, much like the teeth of mammals, allowing it to easily chew plants.
of Tiarajudens, T. eccentricus, was described in the journal Science
in 2011. It was named by Juan Carlos Cisneros, Fernando Abdala, Bruce S. Rubidge, Paula Camboim Dentzien-Dias, and Ana de Oliveira Bueno. The skull was found in Middle Permian-age deposits in Rio Grande do Sul. Paleontologists found the location using satellite photographs from Google Earth
. The locality was identified as a clearing within a thickly vegetated area. The degree of erosion and the color of the rocks were an indication of the locality's age and likelihood of preserving fossils.
after Cisneros et al., 2011:
, which lived around 60 million years ago. The teeth are even larger than those of the carnivorous therapsid Inostrancevia
, one of the largest members of Gorgonopsia
, a group characterized by the presence of long canines. The large canines of Tiarajudens were likely used as a defense against predators or as a means of fighting for mates; living mammals such as the water deer
and musk deer
use their saber teeth for these purposes. The palatal teeth are broad and fit tightly together, an adaptation to consuming fibrous plants. This variation in tooth shape, known as a heterodont
dentition, is common in mammals. While most other Permian therapsids had homodont dentitions (teeth of the same shape), Tiarajudens is one of the earliest therapsids to have a heterodont dentition.
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 saber-toothed herbivorous anomodont
Anomodont
The Anomodontia were a major group of therapsids, an extinct group of animals commonly known as "mammal-like reptiles." They were mostly toothless herbivores. During the Middle Permian they were very diverse, including groups like the Venyukovioidea, the Dromasauria, the Dicynodontia, and early...
which lived during the middle Permian
Permian
The PermianThe term "Permian" was introduced into geology in 1841 by Sir Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil; Murchison asserted in 1841 that he named his "Permian...
period (Capitanian
Capitanian
In the geologic timescale, the Capitanian is an age or stage of the Permian. It is also the uppermost or latest of three subdivisions of the Guadalupian epoch or series. The Capitanian lasted between and...
stage) in what is now Rio Grande do Sul
Rio Grande do Sul
Rio Grande do Sul is the southernmost state in Brazil, and the state with the fifth highest Human Development Index in the country. In this state is located the southernmost city in the country, Chuí, on the border with Uruguay. In the region of Bento Gonçalves and Caxias do Sul, the largest wine...
, Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
. It is known from the holotype
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...
UFRGS PV393P, a nearly complete 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...
. 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...
T. eccentricus was named in 2011
2011 in paleontology
-Lobopods:-Arachnids:-Insects:-Newly named jawless vertebrates:-Newly named acanthodian:-Newly named cartilaginous fishes:-Newly named bony fishes:-Newly named lepospondyls:-Newly named temnospondyls:-Newly named lissamphibians:...
.
Description
Tiarajudens is a member of Anomodontia, a suborder of therapsids. Like other anomodonts, it was a quadrupedal herbivore about the size of a wild boar. The single fragmented holotype skull is short and robust at about 22.5 centimetres (8.9 in) in length. The most prominent features of Tiarajudens are its two large saber-like canineCanine
Canine may refer to:* Domestic dog* Animals belonging to the family Canidae, or the sub-family Caninae* Canine tooth* Ralph Canine, American soldier and government administrator* A character in Glenn Martin, DDS...
teeth. These teeth are unlike the tusks of dicynodont
Dicynodont
Dicynodontia is a taxon of anomodont therapsids or mammal-like reptiles. Dicynodonts were small to large herbivorous animals with two tusks, hence their name, which means 'two dog tooth'...
s, a later group of anomodonts. Twenty-one high-crowned
Crown (tooth)
In dentistry, crown refers to the anatomical area of teeth, usually covered by enamel. The crown is usually visible in the mouth after developing below the gingiva and then erupting into place.-References:...
teeth are present on either side of the upper jaw, including spoon-shaped incisors. Wide palatal
Palate
The palate is the roof of the mouth in humans and other mammals. It separates the oral cavity from the nasal cavity. A similar structure is found in crocodilians, but, in most other tetrapods, the oral and nasal cavities are not truly separate. The palate is divided into two parts, the anterior...
teeth are also present. The top and bottom sets of teeth fit closely together, much like the teeth of mammals, allowing it to easily chew plants.
History
The type speciesType 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...
of Tiarajudens, T. eccentricus, was described in the journal Science
Science (journal)
Science is the academic journal of the American Association for the Advancement of Science and is one of the world's top scientific journals....
in 2011. It was named by Juan Carlos Cisneros, Fernando Abdala, Bruce S. Rubidge, Paula Camboim Dentzien-Dias, and Ana de Oliveira Bueno. The skull was found in Middle Permian-age deposits in Rio Grande do Sul. Paleontologists found the location using satellite photographs from Google Earth
Google Earth
Google Earth is a virtual globe, map and geographical information program that was originally called EarthViewer 3D, and was created by Keyhole, Inc, a Central Intelligence Agency funded company acquired by Google in 2004 . It maps the Earth by the superimposition of images obtained from satellite...
. The locality was identified as a clearing within a thickly vegetated area. The degree of erosion and the color of the rocks were an indication of the locality's age and likelihood of preserving fossils.
Phylogeny
CladogramCladogram
A cladogram is a diagram used in cladistics which shows ancestral relations between organisms, to represent the evolutionary tree of life. Although traditionally such cladograms were generated largely on the basis of morphological characters, DNA and RNA sequencing data and computational...
after Cisneros et al., 2011:
Paleobiology
The saber-like teeth of Tiarajudens are unique among anomodonts, a group of entirely herbivorous therapsids. Although large canines are often found in carnivores, the surrounding teeth of Tiarajudens indicate that it was an herbivore. Tiarajudens is one of the earliest herbivores to possess saber-like canines; previously the oldest known saber-toothed herbivores were large extinct mammals such as TitanoidesTitanoides
Titanoides is an extinct genus of pantodont mammal. It was about long and weighed between 200 and 300 pounds.Titanoides was one of the early Tertiary browsing mammals called pantodonts. Their limbs were short and stout, and they were bear-like in appearance. Some were the size of a rhinoceros....
, which lived around 60 million years ago. The teeth are even larger than those of the carnivorous therapsid Inostrancevia
Inostrancevia
Inostrancevia is a genus of gorgonopsid therapsid found in Sokolki, on the Smaller Northern Dvina River near Kotlas in Arkhangelsk Oblast, Russia. The animal lived 251 million years ago during the Late Permian. The species I...
, one of the largest members of Gorgonopsia
Gorgonopsia
Gorgonopsia is a suborder of therapsid synapsids. Their name is a reference to the Gorgons of Greek mythology. Like other therapsids, gorgonopsians were at one time called "mammal-like reptiles"...
, a group characterized by the presence of long canines. The large canines of Tiarajudens were likely used as a defense against predators or as a means of fighting for mates; living mammals such as the water deer
Water Deer
The Water Deer is a small deer superficially more similar to a musk deer than a true deer but it is classified as a cervid despite having tusks instead of antlers and other anatomical anomalies. These unique characteristics have caused it to be classified in its own genus...
and musk deer
Musk deer
Musk deer are artiodactyls of the genus Moschus, the only genus of family Moschidae. They are more primitive than the cervids, or true deer, in not having antlers or facial glands, in having only a single pair of teats, and in possessing a gall bladder, a caudal gland, a pair of tusk-like teeth...
use their saber teeth for these purposes. The palatal teeth are broad and fit tightly together, an adaptation to consuming fibrous plants. This variation in tooth shape, known as a heterodont
Heterodont
The anatomical term heterodont refers to animals which possess more than a single tooth morphology. For example, members of the Synapsida generally possess incisors, canines , premolars, and molars. The presence of heterodont dentition is evidence of some degree of feeding/hunting specialization...
dentition, is common in mammals. While most other Permian therapsids had homodont dentitions (teeth of the same shape), Tiarajudens is one of the earliest therapsids to have a heterodont dentition.