''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 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 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. It is known from the holotype UFRGS PV393P, a nearly complete skull. The type species ''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. NYTimes.com. “Fearsome Fangs, for a Plant-Eater.” Bhando. March 25, 2011.
/ref> The single fragmented holotype skull is short and robust at about in length. The most prominent features of ''Tiarajudens'' are its two large saber-like

canine Canine may refer to: Zoology and anatomy * a dog-like Canid animal in the subfamily Caninae ** '' Canis'', a genus including dogs, wolves, coyotes, and jackals ** Dog, the domestic dog * Canine tooth, in mammalian oral anatomy People with the ...

teeth. These teeth are unlike the tusks of dicynodonts, 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 type species 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 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