Glanosuchus

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Illustration of the skull of Glanosuchus macrops, 1904

• South Africa

Glanosuchus is a genus of the family of the late Permian Scylacosauridae from South Africa. The type species G. macrops was described by Robert Broom in 1904. Glanosuchus had a middle ear structure that can be sorted between the early therapsids and mammals. Ribs in the nasal cavity suggest that Glanosuchus was at least partially endothermic, similar to mammals.

Description

Glanosuchus macrops was described by Robert Broom in 1904. He named the genus and species based on the nearly complete holotype, skull. The skull was deformed during fossilization and is indistinguishable in all parts of the surrounding matrix. In the illustration of the holotype, Broom reconstructed the skull for other skull.

The skull of Glanosuchus is about 30 cm long. Glanosuchus was probably 1.8 m long. Like other former Therocephalia Glanosuchus had a long, deep snout and large canines. The incisors at the front end of the upper jaw are also large. There are six incisors on each side of the upper jaw. Five small pointed teeth are behind each canine. The muzzle is the front wider than the rear, this is a feature within the therapsids. The nostrils are located at the tip of the snout and directed forward.

Paleobiology

Glanosuchus represents an early stage in the development of the middle ear of mammals. Modern mammals have three bones of the middle ear, which transmits the acoustic energy from the eardrum to the inner ear fluid. Studies show the bones of Glanosuchus that Glanosuchus had a cavity with a bone plate, which acted like a drum; the eardrum transferred the sound waves in the air-filled cavity with. The transmission of sound between the thin bone plate and the vestibular foramen of Glanosuchus is not as effective as in the mammals, which means that the sense of hearing of Glanosuchus was less pronounced than in mammals.

Metabolism

Glanosuchus was probably one of the first warm-blooded therapsids. Endotherm can be observed today in mammals, the only living group of therapsids. Reptiles, the closest living relatives of mammals, are cold-blooded ( Ektothermie ). Endothermic therapsids probably evolved from more primitive, cold-blooded synapsids in the Permian or the Triassic.

While fur, which is generally regarded as a clear indication of endothermy, non- therapsids was found in "non- mammal", suggest some skeletal features attention to the metabolic rate of the animals. Modern mammals have turbinates, these are a type of Concha ( tray with bone ) in the nasal cavity that collect moisture from the air. As a warm-blooded mammals need to breathe faster in order to supply enough oxygen for their high metabolism. Water from the air condenses on the Maxilloturbinates and prevents drying of the nasal cavity and allows mammals for inhaling enough oxygen to support their high metabolism.

Glanosuchus has fins which are positioned deep in the nasal cavity, indicating that the nasal turbinates in the direct path of the air stream were. The Maxilloturbinates is not preserved because it was either very thin or cartilaginous. The possibility that these ribs instead are connected to an olfactory turbinates was also considered. However, the possible presence of turbinate suggests that Glanosuchus was able to quickly breath could have dried breathe without the nasal passage, and therefore he could have been a warm-blooded animal. Glanosuchus is the oldest known Therapside, who had a turbinate, but he was probably not quite endothermic.

System

Glanosuchus is a genus of Scylacosauridae, one of the most primitive family of Therocephalia. One of his next of kin is Pristerognathus. Cladogram after Hutten Locker et al. (2011):

Lycosuchus

Glanosuchus

Ictidosaurus

Pristerognathus

Eutherocephalia