Machaeroprosopus Fossil Tooth Phytosaur Crocodile Thecodon Prehistoric Reptile Triassic Collection (2)

Rare Fossil Tooth Phytosaur Crocodile mm 2.5 x 2 Prehistoric Thecodont Machaeroprosopus andersoni Extinct Armored Reptiles Mesozoic Triassic Collecting Paleontology Museum, in plexiglas box diam. 3 cm.

Pleasant collectible fossil specimen, difficult to find, of a young phytosaur, complete and in good condition, with excellent front and rear surface details, with evident serration and perfectly preserved enamel.

Machaeroprosopus is an extinct genus of Pseudopalatinae Phytosauridae of the late Triassic of the southwestern United States. M. andersoni was first described and named by Maurice G. Mehl in 1922, based on the chromype FMNH UC 396, a partial skull collected from the Bull Canyon Formation in the county of Guadalupe, New Mexico. It reached a length of about 2 meters.
M. validus, once considered the type of Machaeroprosopus, was named in 1916 on the basis of three complete skulls of Chinle Formation, Arizona. The skulls have been lost since the 50s and a dashed drawing in the original 1916 description is the only visual testimony of the specimen.
Another species, M. andersoni, was named in 1922 by New Mexico and the species M. adamanensis, M. gregorii, M. lithodendrorum, M. tenuis and M. zunii were named in 1930. Most species it has been reassigned to the genera Smilosuchus, Rutiodon, Pseudopalatus or Phytosaurus. Until recently, M. validus was considered the only species that had not been reassigned. Thus, Machaeroprosopus was considered a "nomen dubium" (dubious name) due to the lack of diagnostic samples that may support its distinction from other kinds of phytosaurs. However, a taxonomic review of Machaeroprosopus, conducted by Parker et al., Reconfirmed the genus Machaeroprosopus, while the name Pseudopalatus should be considered a synonym. This new taxonomy has already been accepted in several studies.

Thecodonts ("teeth infixed in the alveoli"), are primitive diapsid reptiles that appeared in the upper Permian and spread during the Triassic period. The group includes the ancestors of dinosaurs (including birds), crocodiles and pterosaurs, as well as a number of species (e.g. Euparkeria) that have become extinct without leaving descendants.

Phytosaur are an extinct group of Late Triassic Archosauriphormes reptiles, largely semi-aquatic. They belong to the Phytosauridae family, order Phytosauria. They are generally considered the most basic group of Crurotarsa Pseudosuchia, an archosaur clade that includes crocodiles and their extinct relatives. Phytosaurs are often excluded from a clade called Suchia, which usually includes all the other cruel, including Aetosauria, Rauisuchia and Crocodilomorpha. Some recent studies on the evolutionary relationships of early archosauriforms suggest that phytosaurs evolved before the separation between crocodiles and birds.
The phytosaurs were heavily armored animals, with a remarkable resemblance to modern crocodiles in terms of size, appearance and lifestyle, as an example of evolutionary convergence. The name phytosaurus means "plant reptile", since it was mistakenly thought that the first phytosaur fossils belonged to plant eaters. The name is misleading because the sharp teeth in the phytosaur jaws clearly show that they were predators.
The phytosaurs had an almost global distribution during the Triassic, which means that the phytosaurs had dispersed throughout the Pangea due to the absence of true geographical barriers; only in the most southern regions are rare, probably due to greater aridity. Their fossil remains were in fact found in Europe, North America, India, Morocco, Thailand, Brazil, Greenland and Madagascar, up to the Triassic-Jurassic time boundary, when, together with many other large reptiles crying, they were killed by the great extinction of the Triassic, around 200 million years ago.
The phytosaurs have a marked morphological variability, in particular with very different cranial forms, due to nutrition and lifestyle habits. Those with a long, slender muzzle with many identical tapered teeth were probably piscivorous. The forms with short, massive and broad snouts had very strong skulls and jaws with diversified heterodon teeth, as they fed on terrestrial animals that approached the water to drink. Then there are intermediate forms. Modern crocodiles exhibit a similar morphological diversity, like the alligator and the gavial.
Despite their great similarities in appearance and lifestyle, there are some small differences that distinguish phytosaurs from true crocodiles, such as the primitive structure of the ankle, the absence of the secondary bone palate (perhaps they had fleshy) that allows crocodiles to breathe even when the mouth is full of water. They were more armored than crocodiles, protected by heavy scales of bone, with the belly reinforced by a dense arrangement of abdominal ribs. Furthermore, and most notably, the phytosaurs had the nostrils positioned near or above the level of the eye, in contrast to the crocodiles where the nostrils are near the end of the snout, to allow them to breathe while the rest of the body remains submerged. Unlike most of the crocodiles, finally, the phytosaurs had finely and imperceptibly serrated teeth: this seems to suggest that they did not perform the typical screwing to dismember the prey, like crocodiles and alligators.