Tiarajudens

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Tiarajudens
Temporal range: Capitanian
~260  Ma
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Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Chordata
Order: Therapsida
Clade: Anomocephaloidea
Genus: Tiarajudens
Cisneros et al., 2011
Species:
T. eccentricus
Binomial name
Tiarajudens eccentricus
Cisneros et al., 2011

Tiarajudens ("Tiaraju tooth") is an extinct genus of saber-toothed herbivorous anomodonts which lived during the Middle Permian period (Capitanian stage) in what is now Rio Grande do Sul, Brazil. It is known from the holotype UFRGS PV393P, a nearly complete skull. The type species T. eccentricus was named in 2011. [1]

Contents

Description

Restoration Tiarajudens NT.jpg
Restoration

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. [2] The single fragmented holotype skull is short and robust at about 22.5 centimetres (8.9 in) in length. The most prominent features of Tiarajudens are its two large saber-like canine teeth. These teeth are unlike the tusks of dicynodonts, 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. Wide palatal 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.

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

Phylogeny

Cladogram after Cisneros et al., 2011: [1]

Therapsida

Tetraceratops

Raranimus

Lycosuchus

Biarmosuchus

Gorgonops

Herpetoskylax

Estemmenosuchus

Tapinocaninus

Titanophoneus

Syodon

Anomodontia

Biseridens

Anomocephaloidea

Tiarajudens

Anomocephalus

Galechirus

Venyukovioidea

Otsheria

Suminia

Ulemica

Patranomodon

Galeops

Eodicynodon

Diictodon

Robertia

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. [4] [7] The teeth are even larger than those of the carnivorous therapsid Inostrancevia , one of the largest members of Gorgonopsia, a group characterized by the presence of long canines. [4] 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 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 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. [1]

See also

Related Research Articles

Dinocephalia suborder of mammals (fossil)

Dinocephalia is a clade of large-bodied early therapsids that flourished for a brief time in the Middle Permian between 270 and 260 million years ago (Ma), but became extinct, leaving no descendants. Dinocephalians included herbivorous, carnivorous, and omnivorous forms. Many species had thickened skulls with many knobs and bony projections. Dinocephalian fossils are known from Russia, China, Brazil, South Africa, Zimbabwe, and Tanzania.

Gorgonopsia suborder of synapsids (fossil)

Gorgonopsia is an extinct clade of non-mammalian synapsids from the Permian period. Gorgonopsians were quadrupedal predators with prominent canine teeth, and the largest species were the apex predators of their ecosystems. Like other non-mammalian synapsids, gorgonopsians were once described as "mammal-like reptiles", due to their mix of mammalian and reptilian traits. However, this description is no longer considered accurate as they are not reptiles. Rather, as therapsids, they are closely related to mammals. Gorgonopsian fossils have been found in Russia and Africa.

Anteosauridae family of mammals (fossil)

Anteosauridae is an extinct family of large carnivorous dinocephalian therapsids that are known from the Middle Permian of Asia, Africa, and South America.These animals were by far the largest predators of the Permian period, with skulls reaching 80 cm in length in adult individuals, far larger than the biggest gorgonopsian.

Theriodont taxon of mammals (fossil)

The theriodonts or Theriodontia are a major group of therapsids. They can be defined in traditional, Linnaean terms, in which case they are a suborder of synapsids that lived from the Middle Permian to the Middle Cretaceous, or in cladistic terms, in which case they include not only the traditional theriodonts but also their descendants the mammals as well.

Dromasauria infraorder of mammals (fossil)

Dromasaurs are a paraphyletic group of anomodont therapsids from the Middle Permian. They were small with slender legs and long tails. Their skulls were short, but the eye sockets were large. Dromasauria was once considered to be a major group of basal anomodonts along with the infraorder Venyukovioidea. It includes the genera Galepus, Galechirus, and Galeops, all from southern Africa. Below is a cladogram based on Modesto and Rubidge (2000), Liu et al. (2009) and Cisneros et al. (2011):

<i>Eodicynodon</i> genus of mammals (fossil)

Eodicynodon is an extinct genus of dicynodont therapsids, a highly diverse group of herbivorous synapsids that were widespread during the middle-late Permian and early Triassic. As its name suggests, Eodicynodon is the oldest and most primitive dicynodont yet identified, ranging from the middle to late Permian and possessing a mix of ancestral Anomodont/therapsid features and derived dicynodont synapomorphies.

<i>Tapinocaninus</i> Species of mammal (fossil)

Tapinocaninus is an extinct genus of therapsids in the family Tapinocephalidae, in which it is the most basal member. Only one species is known, Tapinocaninus pamelae .Living during the Middle Permian.

<i>Endothiodon</i> genus of mammals (fossil)

Endothiodon is an extinct genus of large dicynodont from the Late Permian. Like other dicynodonts, Endothiodon was an herbivore, but it lacked the two tusks that characterized most other dicynodonts. The anterior portion of the upper and lower jaw are curved upward, creating a distinct beak that is thought to have allowed them to be specialized grazers.

<i>Anomocephalus</i> genus of mammals (fossil)

Anomocephalus is an extinct genus of primitive anomodonts and belongs to the clade Anomocephaloidea. The name is said to be derived from the Greek word anomos meaning lawless and cephalos meaning head. The proper word for head in Greek is however κεφαλή (kephalē). It is primitive in that it retains a complete set of teeth in both jaws, in contrast to its descendants, the dicynodonts, whose dentition is reduced to only a single pair of tusks, with their jaws covered by a horny beak similar to that of a modern tortoise. However, they are in no way closely related.

<i>Biseridens</i> genus of mammals (fossil)

Biseridens is an extinct genus of anomodont therapsid, and one of the most basal anomodont genera known. Originally known from a partial skull misidentified as an 'eotitanosuchian' in 1997, another well-preserved skull was found in the Xidagou Formation, an outcropping in the Qilian Mountains of Gansu, China, in 2009 that clarified its relationships to anomodonts, such as the dicynodonts.

<i>Dimacrodon</i> Genus of extinct therapsid

Dimacrodon is an extinct genus of non-mammalian synapsid from the latest Early Permian San Angelo Formation of Texas. It is distinguished by toothless, possibly beaked jaw tips, large lower canines and a thin bony crest on top of its head. Previously thought to be an anomodont therapsid related to dicynodonts, it was later found to lack any diagnostic features of anomodonts or even therapsids and instead appears to be a 'pelycosaur'-grade synapsid of uncertain classification.

<i>Scymnosaurus</i> genus of mammals (fossil)

Scymnosaurus is now considered a nomen dubium.

Bauriidae family of mammals (fossil)

Bauriidae is an extinct family of therocephalian therapsids. Bauriids were the latest-surviving group of therocephalians after the Permian–Triassic extinction event, going extinct in the Middle Triassic. They are among the most advanced eutherocephalians and possess several mammal-like features such as a secondary palate and wide postcanine teeth at the back of the jaws. Unlike other therocephalians, bauriids were herbivorous. They were also smaller than earlier members of the group. Two subfamilies are classified within Bauriidae: Nothogomphodontinae and Bauriinae.

Chainosauria taxon of mammals (fossil)

Chainosauria is a large clade of anomodont therapsids. It includes dicynodonts, dromasaurians and the basal taxa Patranomodon.

Abrahamskraal Formation

The Abrahamskraal Formation is a geological formation and is found in numerous localities in the Northern Cape, Western Cape, and the Eastern Cape of South Africa. It is the lowermost formation of the Adelaide Subgroup of the Beaufort Group, a major geological group that forms part of the greater Karoo Supergroup. It represents the first fully terrestrial geological deposits of the Karoo Basin. Outcrops of the Abrahamskraal Formation are found from the small town Middelpos in its westernmost localities, then around Sutherland, the Moordenaarskaroo north of Laingsburg, Williston, Fraserburg, Leeu-Gamka, Loxton, and Victoria West in the Western Cape and Northern Cape. In the Eastern Cape outcrops are known from Rietbron, north of Klipplaat and Grahamstown, and also southwest of East London.

Anteosaurinae suborder of mammals (fossil)

Anteosaurinae is an extinct subfamily of dinocephalian therapsids. It is one of two subfamilies in the family Anteosauridae, the other being Syodontinae.

Blattoidealestes is an extinct genus of therocephalian therapsid from the Middle Permian of South Africa. The type species Blattoidealestes gracilis was named by South African paleontologist Lieuwe Dirk Boonstra from the Tapinocephalus Assemblage Zone in 1954. Dating back to the Middle Permian, Blattoidealestes is one of the oldest therocephalians. It is similar in appearance to the small therocephalian Perplexisaurus from Russia, and may be closely related.

Venyukoviamorpha is an extinct superfamily of anomodont therapsids under the superorder Venyukovoidea. While the exact placement of many genera within the basal anomodonts is contentious, it is generally accepted that the Venyukoviamorpha represent a monophyletic clade.

Anomocephaloidea is a clade of anomodont therapsids that existed in Gondwana during the Middle Permian and includes two species, Anomocephalus africanus from South Africa and Tiarajudens eccentricus from Brazil, both of which are characterized by large body size and teeth that fit tightly together or occlude. Anomocephaloidea is among the most basal groups of anomodonts, the other being Venyukovioidea, which differs in being a Laurasian clade of mostly small-bodied species. Anomocephaloidea was named in 2011 with the discovery of Tiarajudens; Anomocephalus had been known since 1999, but was unique among anomodonts until Tiarajudens was described. Both Anomocephalus and Tiarajudens were herbivores, although the latter possessed a pair of saber-like canine teeth that may have been used in display or combat with other individuals of the same species. Although Anomocephaloidea was short-lived and had a limited geographic distribution, it was part of a larger evolutionary radiation of anomodonts in the Middle Permian characterized by the evolution of a diverse array of new morphological characteristics and ecological roles, and that would later lead to the rise of Dicynodontia, the largest clade within Anomodontia and one of the most successful groups of tetrapods in the Permian.

<i>Abdalodon</i> genus of therapsids

Abdalodon is an extinct genus of late Permian cynodonts, known by its only species A. diastematicus.Abdalodon together with the genus Charassognathus, form the clade Charassognathidae. This clade represents the earliest known cynodonts, and is the first known radiation of Permian cynodonts.

References

  1. 1 2 3 Cisneros, J.C.; Abdala, F.; Rubidge, B.S.; Dentzien-Dias, D.; Bueno, A.O. (2011). "Dental Occlusion in a 260-Million-Year-Old Therapsid with Saber Canines from the Permian of Brazil". Science. 331: 1603–1605. doi:10.1126/science.1200305. PMID   21436452.
  2. NYTimes.com. “Fearsome Fangs, for a Plant-Eater.” Bhando. March 25, 2011.
  3. Fröbisch, J. (2011). "On Dental Occlusion and Saber Teeth". Science. 331: 1525–1528. doi:10.1126/science.1204206.
  4. 1 2 3 4 Harmon, Katherine (25 March 2011). "What was a South American herbivore doing with saber teeth?". Observations. Scientific American. Archived from the original on August 26, 2012. Retrieved 25 March 2011.
  5. Viegas, Jennifer (24 March 2011). "Saber-Toothed Vegetarian Had Threatening Mouthful". Discovery News . Archived from the original on March 18, 2012. Retrieved 25 March 2011.
  6. 1 2 Choi, C.Q. (24 March 2011). "Odd Ancient Beast Was Saber-Toothed Vegetarian". LiveScience . Retrieved 25 March 2011.
  7. Handwerk, B. (24 March 2011). "Odd Saber-Toothed Beast Discovered—Preyed on ... Plants?". National Geographic Daily News . Retrieved 24 March 2011.