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

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of saber-toothed

herbivorous A herbivore is an animal anatomically and physiologically evolved to feed on plants, especially upon vascular tissues such as foliage, fruits or seeds, as the main component of its diet. These more broadly also encompass animals that eat n ...

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. Anomodonts were very diverse during the Middle Pe ...

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 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 t ...

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 s ...

Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

. It is known from the

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

UFRGS PV393P, a nearly complete

skull The skull, or cranium, is typically a bony enclosure around the brain of a vertebrate. In some fish, and amphibians, the skull is of cartilage. The skull is at the head end of the vertebrate. In the human, the skull comprises two prominent ...

. The

type species In International_Code_of_Zoological_Nomenclature, 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 spe ...

''T. eccentricus'' was named in

2011 The year marked the start of a Arab Spring, series of protests and revolutions throughout the Arab world advocating for democracy, reform, and economic recovery, later leading to the depositions of world leaders in Tunisia, Egypt, and Yemen ...

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. Anomodonts were very diverse during the Middle Pe ...

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

herbivore A herbivore is an animal anatomically and physiologically evolved to feed on plants, especially upon vascular tissues such as foliage, fruits or seeds, as the main component of its diet. These more broadly also encompass animals that eat ...

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 Suidae, suid native to much of Eurasia and North Africa, and has been introduced to the Americas and Oceania. The speci ...

. 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 herbivores that typically bore a pair of tusks, hence their name, which means 'two dog tooth'. Members of the group possessed a horny, t ...

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 sepa ...

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 discipline that builds and organises knowledge in the form of testable hypotheses and predictions about the universe. Modern science is typically divided into twoor threemajor branches: the natural sciences, which stu ...

'' 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, Brazil, South Region of Brazil. The official name is Rio do Rasto, although in some publications it appears as ''Rio do Rastro''. The strata were d ...

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

Google Earth Google Earth is a web mapping, web and computer program created by Google that renders a 3D computer graphics, 3D representation of Earth based primarily on satellite imagery. The program maps the Earth by superimposition, superimposing satelli ...

. 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 language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...

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

Inostrancevia ''Inostrancevia'' is an extinction, extinct genus of large carnivorous therapsids which lived during the Late Permian in what is now European Russia and Southern Africa. The first-known fossils of this gorgonopsian were discovered in the context ...

'', one of the largest members of

Gorgonopsia Gorgonopsia (from the Greek Gorgon, a mythological beast, and 'aspect') is an extinct clade of Saber-toothed predator, sabre-toothed therapsids from the Middle Permian, Middle to the Upper Permian, roughly between 270 and 252 million years ago. ...

, 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 species native to Korea and China. Its prominent tusks, similar to those of musk deer, have led to both subspecies being colloquially named vampire deer in English-speaking areas to which t ...

and

musk deer Musk deer can refer to any one, or all eight, of the species that make up ''Moschus'', the only extant genus of the family (biology), family Moschidae. Despite being commonly called deer, they are not true deer belonging to the family Cervidae, b ...

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. Human dentition is heterodont and diphyodont as an example. In vertebrates, heterodont pertains to animals wher ...

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. Human dentition is heterodont and diphyodont as an example. In vertebrates, heterodont pertains to animals where ...

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

Notes

References