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

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

of saber-toothed

herbivorous 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 mouthpar ...

anomodonts 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 ± ...

period Period may refer to: Common uses * Era, a length or span of time * Full stop (or period), a punctuation mark Arts, entertainment, and media * Period (music), a concept in musical composition * Periodic sentence (or rhetorical period), a concept ...

(

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 million years ago. It was preceded by ...

stage) in what is now Rio Grande do Sul,

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 sever ...

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, th ...

. 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 specime ...

''T. eccentricus'' was named in 2011.

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 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, typic ...

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 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 separ ...

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 Scientific method, builds and organizes knowledge in the form of Testability, testable explanations and predictions about the universe. Science may be as old as the human species, and some of the earli ...

'' 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 Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of foss ...

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.

Phylogeny

Cladogram A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to ...

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 Tatar ...

'', one of the largest members of

Gorgonopsia Gorgonopsia (from the Greek Gorgon, a mythological beast, and 'aspect') is an extinct clade of sabre-toothed therapsids from the Middle to Upper Permian roughly 265 to 252 million years ago. They are characterised by a long and narrow skull, a ...

, 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 The water deer (''Hydropotes inermis'') is a small deer superficially more similar to a musk deer than a true deer. Native to China and Korea, there are two subspecies: the Chinese water deer (''Hydropotes inermis inermis'') and the Korean water ...

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.

Notes

References