Tritylodon - AbsoluteAstronomy.com

Trityldon was a genus of tritylodont

Tritylodontidae

Tritylodontids were small to medium-sized, highly specialized and extremely mammal-like cynodonts. They were the last family of the non-mammalian synapsids. One of the last cynodont lines to appear, the Tritylodontidae descended from a Cynognathus-like cynodont...

, one of the most advanced group of cynodont

Cynodont

Cynodontia or cynodonts are a taxon of therapsids which first appeared in the Late Permian and were eventually distributed throughout all seven continents by the Early Triassic . This clade includes modern mammals and their extinct close relatives. They were one of the most diverse groups of...

therapsids. They lived in the Early Jurassic

Early Jurassic

The Early Jurassic epoch is the earliest of three epochs of the Jurassic period...

and possibly Late Triassic periods along with dinosaur

Dinosaur

Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...

s. They also shared a lot of characteristics with mammal

Mammal

Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...

s, and were once considered mammals because of overall skeleton construction. That was changed due to them retaining the vestigial reptilian jawbones and a different skull structure. Trityldons are now regarded as synapsid

Synapsid

Synapsids are a group of animals that includes mammals and everything more closely related to mammals than to other living amniotes. They are easily separated from other amniotes by having an opening low in the skull roof behind each eye, leaving a bony arch beneath each, accounting for their name...

s (often called "mammal-like reptiles").

Characteristics

If a living Tritylodon were to be seen today, it would look a lot like a large rodent. They were about 1 foot (0.3 m) long but there is no certainty about the exact weight. Also the way they ate was much like a rodent, doing a grinding motion with the bottom teeth sliding against the top teeth. The bottom teeth were much like a set of cusps and the top teeth were a set of matching grooves that matched perfectly allowing this motion. There were large incisors at the very front of their mouth separated by a gap from the rest of the teeth. Even with their mouth closed the incisors would still stick out slightly visible. The legs were directly beneath the body like mammals, unlike the earlier therapsids with sprawling limbs.

These animals were burrowers; the structure of the shoulder and front limbs show this. Also the large front incisors worked very well with helping digging and getting buried plant parts. Tritylodons were strictly herbivores based on the way they ate and shape of teeth are proof. Any of the Tritylodonts including Tritylodon were warm-blooded

Warm-blooded

The term warm-blooded is a colloquial term to describe animal species which have a relatively higher blood temperature, and maintain thermal homeostasis primarily through internal metabolic processes...

or endothermic. Another interesting thing about them was that they were oviviparous

Oviparity

Oviparous animals are animals that lay eggs, with little or no other embryonic development within the mother. This is the reproductive method of most fish, amphibians, reptiles, all birds, the monotremes, and most insects, some molluscs and arachnids....

Intermediate species

With partial reptile characteristics and mammal characteristics, the Tritylodon part of the Tritylodont family could be part of the link between reptiles and mammals. Some argue that Tritylodonts were too specialized, and were outcompeted by carnivorous archosaurs and other newly evolving early mammals, to become such a link. There is some possible evidence of a link to the group multituberculata. The features of the multituberculata group do match a lot of characteristics of the order Monotremata which includes the egg laying mammals: the duck-billed platypus

Platypus

The platypus is a semi-aquatic mammal endemic to eastern Australia, including Tasmania. Together with the four species of echidna, it is one of the five extant species of monotremes, the only mammals that lay eggs instead of giving birth to live young...

and echidna

Echidna

Echidnas , also known as spiny anteaters, belong to the family Tachyglossidae in the monotreme order of egg-laying mammals. There are four extant species, which, together with the platypus, are the only surviving members of that order and are the only extant mammals that lay eggs...

Habitat

The Tritylodons habitat was limited to the forests of south Africa, with other fossils found in the Mount Kirkpatrick Formation

Mount Kirkpatrick Formation

The Mount Kirkpatrick Formation is one of only two major dinosaur-bearing rock formations yet found on the continent of Antarctica; the other is the Santa Marta Formation from the Late Cretaceous...

of Antarctica. When the species originated, about 200 million years ago, the African area was dryer and hotter. But for most of their existence the climate was tropical and wetter.

Fossils

The Tritylodon fossils in south Africa are found concentrated mainly in an area about 11,000 km² (4,250 mi²). They have been found in floodplain deposits of the Lower Jurassic Elliot Formation (upper Karoo Supergroup). In this area there have been so many findings it has been named the Tritylodon Acme Zone. The fossil findings have all been in the Orange Free State of South Africa

Orange Free State

The Orange Free State was an independent Boer republic in southern Africa during the second half of the 19th century, and later a British colony and a province of the Union of South Africa. It is the historical precursor to the present-day Free State province...

.

The genus Tritylodon of the Tritylodonts is restricted to the south African forms: Tritylodon longaevus and Tritylodon maximus. It is suggested that T. maximus is either a large T. longeavus or a closely related species. If it is a closely related species it could possiby be ecological succession since the larger T. maximus fossils have been dated in the Sinemurian–Pleisbachian mainly less than 190 million years ago and the T. longaevus in the Hettangian–Sinemurian mainly more than 190 million years ago. With the fossil findings of each species overlapping in Sinemurian stage, the fossils show two differences, T. maximus being larger and having nine upper postcanines (neither species had canine teeth) instead of the seven teeth like T. longeavus. All other structures of the two Tritylodon species were the same.

Cladogram

External links

http://fossils.valdosta.edu/fossil_pages/fossils_jur/t64.html
http://www.britannica.com/EBchecked/topic/606062/tritylodont
http://home.arcor.de/ktdykes/jtherap.htm#tritylodon
http://www.dinosaurden.co.uk/dinosaurs_A-D.html
http://www.ncbi.nlm.nih.gov/pubmed/12097908?dopt=Abstract
http://tritylodontidae.totallyexplained.com/
http://www.enchantedlearning.com/subjects/dinosaurs/mesozoic/jurassic/

for an image of what the continents looked like at the time when the tritylodons lived click this link: http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookPaleo5.html

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