''Tiarajudens'' (" Tiaraju tooth") is an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

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 saber-toothed herbivorous

anomodont Anomodontia is an extinct group of non-mammalian therapsids from the Permian and Triassic periods. By far the most speciose group are the dicynodonts, a clade of beaked, tusked herbivores.Chinsamy-Turan, A. (2011) ''Forerunners of Mammals: Ra ...

s which lived during the

Middle Permian The Guadalupian is the second and middle series/epoch of the Permian. The Guadalupian was preceded by the Cisuralian and followed by the Lopingian. It is named after the Guadalupe Mountains of New Mexico and Texas, and dates between 272.95 ± 0. ...

period ( Capitanian stage) in what is now

Rio Grande do Sul Rio Grande do Sul (, , ; "Great River of the South") is a Federative units of Brazil, state in the South Region, Brazil, southern region of Brazil. It is the Federative_units_of_Brazil#List, fifth-most-populous state and the List of Brazilian st ...

Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...

. It is known from 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 ...

UFRGS PV393P, a nearly complete

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 ...

. 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 ...

''T. eccentricus'' was named in

2011 File:2011 Events Collage.png, From top left, clockwise: a protester partaking in Occupy Wall Street heralds the beginning of the Occupy movement; protests against Libyan dictator Muammar Gaddafi, who was killed that October; a young man celebrate ...

Description

''Tiarajudens'' is a member of

Anomodont Anomodontia is an extinct group of non-mammalian therapsids from the Permian and Triassic periods. By far the most speciose group are the dicynodonts, a clade of beaked, tusked herbivores.Chinsamy-Turan, A. (2011) ''Forerunners of Mammals: Ra ...

ia, a suborder of therapsids. Like other anomodonts, it was a quadrupedal

herbivore A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthpart ...

about the size of a

wild boar The wild boar (''Sus scrofa''), also known as the wild swine, common wild pig, Eurasian wild pig, or simply wild pig, is a suid native to much of Eurasia and North Africa, and has been introduced to the Americas and Oceania. The species is ...

. NYTimes.com. “Fearsome Fangs, for a Plant-Eater.” Bhando. March 25, 2011.
/ref> The single fragmented

skull is short and robust at about in length. The most prominent features of ''Tiarajudens'' are its two large saber-like canine teeth. These teeth are unlike the tusks of

dicynodont Dicynodontia is an extinct clade of anomodonts, an extinct type of non-mammalian therapsid. Dicynodonts were herbivorous animals with a pair of tusks, hence their name, which means 'two dog tooth'. Members of the group possessed a horny, typicall ...

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.

History

The

of ''Tiarajudens'', ''T. eccentricus'', was described in the journal ''

Science Science is a systematic endeavor that builds and organizes knowledge in the form of testable explanations and predictions about the universe. Science may be as old as the human species, and some of the earliest archeological evidence for ...

'' 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 the Middle Permian

Rio do Rasto Formation The Rio do Rasto Formation is a Late Permian sedimentary geological formation in the South Region of Brazil. The official name is Rio do Rasto, although in some publications it appears as ''Rio do Rastro''. Geography It is found mainly in the B ...

in Rio Grande do Sul. Paleontologists found the location using satellite photographs from

Google Earth Google Earth is a computer program that renders a 3D computer graphics, 3D representation of Earth based primarily on satellite imagery. The program maps the Earth by superimposition, superimposing satellite images, aerial photography, and geog ...

. 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

Cladogram 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 ''

Titanoides ''Titanoides'' is an extinct genus of pantodont mammal that lived in North Dakota and as far north as central Alberta. They were up to long and up to in weight, being the largest mammals of their habitat, a tropical swampland where the main pr ...

'', which lived around 60 million years ago. The teeth are even larger than those of the carnivorous therapsid ''

Inostrancevia ''Inostrancevia'' is an extinct genus of carnivorous therapsids, containing the largest members of gorgonopsians, predators characterized by long, saber-tooth-like canines. The various species inhabited European Russia during the Upper Tatarian ...

'', 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 Musk deer can refer to any one, or all seven, of the species that make up ''Moschus'', the only extant genus of the family Moschidae. Despite being commonly called deer, they are not true deer belonging to the family Cervidae, but rather their fa ...

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 In anatomy, a heterodont (from Greek, meaning 'different teeth') is an animal which possesses more than a single tooth morphology. In vertebrates, heterodont pertains to animals where teeth are differentiated into different forms. For example, ...

dentition, is common in mammals. While most other Permian therapsids had

homodont In anatomy, a heterodont (from Greek, meaning 'different teeth') is an animal which possesses more than a single tooth morphology. In vertebrates, heterodont pertains to animals where teeth are differentiated into different forms. For example ...

dentitions (teeth of the same shape), ''Tiarajudens'' is one of the earliest therapsids to have a heterodont dentition.

Notes

References