| Tiarajudens | |
|---|---|
 | |
| Diagram skeleton ofT. eccentricus.[a] | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Synapsida |
| Clade: | Therapsida |
| Suborder: | †Anomodontia |
| Clade: | †Anomocephaloidea |
| Genus: | †Tiarajudens Cisneroset al.,2011 |
| Species: | †T. eccentricus |
| Binomial name | |
| †Tiarajudens eccentricus Cisneroset al., 2011 | |
Tiarajudens (tee-AIR-ə-JOO-dens) ("Tiaraju tooth") is anextinctgenus of saber-toothedherbivorousanomodonts which lived during theMiddle Permianperiod (Capitanian stage) in what is nowRio Grande do Sul,Brazil. It is known from theholotype UFRGS PV393P, a nearly completeskull. Thetype speciesT. eccentricus was named in2011.[1]
Tiarajudens is a member ofAnomodontia, a suborder of therapsids. Like other anomodonts, it was a quadrupedalherbivore about the size of awild boar.[2] The single fragmentedholotype skull is short and robust at about 22.5 centimetres (8.9 in) in length. The most prominent features ofTiarajudens are its two large saber-likecanine teeth. These teeth are unlike the tusks ofdicynodonts, a later group of anomodonts.[3][4] Twenty-one high-crowned teeth are present on either side of the upper jaw, including spoon-shaped incisors. Widepalatal teeth are also present.[5] The top and bottom sets of teeth fit closely together, much like the teeth of mammals, allowing it to easily chew plants.
Thetype species ofTiarajudens,T. eccentricus, was described in the journalScience 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 PermianRio do Rasto Formation in Rio Grande do Sul.Paleontologists found the location using satellite photographs fromGoogle Earth.[6] 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.[6]
Cladogram after Cisneroset al., 2011:[1]
The saber-like teeth ofTiarajudens are unique among anomodonts, a group of entirely herbivorous therapsids. Although large canines are often found in carnivores, the surrounding teeth ofTiarajudens 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 asTitanoides, which lived around 60 million years ago.[4][7] The teeth are even larger than those of the carnivorous therapsidInostrancevia, one of the largest members ofGorgonopsia, a group characterized by the presence of long canines.[4] The large canines ofTiarajudens were likely used as a defense against predators or as a means of fighting for mates; living mammals such as thewater deer andmusk deer use their saber teeth for these purposes.[4] The palatal teeth are broad and fit tightly together, an adaptation to consuming fibrous plants. This variation in tooth shape, known as aheterodont dentition, is common in mammals. While most other Permian therapsids hadhomodont dentitions (teeth of the same shape),Tiarajudens is one of the earliest therapsids to have a heterodont dentition.[1]
