Glanosuchus
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| Glanosuchus | ||||||||||||
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Illustration of the skull of Glanosuchus macrops , 1904 |
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| Temporal occurrence | ||||||||||||
| Upper Perm | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Glanosuchus macrops | ||||||||||||
| Broom , 1904 |
Glanosuchus is a genus ofthe Scylacosauridae family ofthe Late Permian from South Africa . The type species G. macrops was described by Robert Broom in 1904. Glanosuchus had a middle ear structure that can be classified between that of the early therapsids and that of mammals. Ribs in the nasal cavity suggest that Glanosuchus was at least partially endothermic , similar to that of mammals.
description
Glanosuchus macrops was described by Robert Broom in 1904. He named the genus and species on the basis of the almost complete holotype , the skull. The skull was deformed during fossilization and cannot be distinguished from the surrounding matrix in all places . In illustrating the holotype, Broom reconstructed the skull for other skulls as well.
The skull of Glanosuchus is approximately 30 cm long. Glanosuchus was probably 1.8 m long. Like other earlier therocephalia , Glanosuchus had a long, deep snout and large canine teeth . The incisors on the front end of the upper jaw are also large. There are six incisors on each side in the upper jaw. There are five small pointed teeth behind each canine tooth. The snout is wider at the front than at the back, this is a special feature of the Therapsids. The nostrils are located at the tip of the muzzle and point forward.
Paleobiology
Hearing
Glanosuchus represents an early stage in the development of the mammalian middle ear . Modern mammals have three bones in the middle ear that carry sound energy from the eardrum to the fluid in the inner ear. Studies of the bones of Glanosuchus show that Glanosuchus had a cavity with a bone plate that acted like an eardrum; the eardrum transmitted the sound waves into the air-filled cavity. The transmission of sound between the thin bone plate and the vestibular foramen of Glanosuchus is not as effective as in the mammal, which means that the Glanosuchus' sense of hearing was less pronounced than in the mammals.
metabolism
Glanosuchus was probably one of the first warm-blooded therapsids. Endothermia can be observed today in mammals, the only living group of therapsids. Reptiles , the closest living relatives of mammals, are cold-blooded ( ectothermia ). Endothermic therapsids probably developed from more primitive, cold- blooded synapsids in the Permian or Triassic .
While fur, which is commonly considered a clear indicator of endothermia, was not found in "non-mammalian" therapy drugs, some skeletal functions suggest the animals' metabolic rate. Modern mammals have nasal concha , a type of concha (deposit with bones) in the nasal cavity that collects moisture from the air we breathe. As warm-blooded animals, mammals need to breathe faster to provide enough oxygen for their high metabolism. Water from the air we breathe condenses on the maxilloturbinale, preventing the nasal cavity from drying out and allowing mammals to inhale enough oxygen to support their high metabolism.
Glanosuchus has ribs positioned deep in the nasal cavity that indicate that the turbinates were in the direct path of the airflow. The maxilloturbinate has not been preserved because it was either very thin or cartilaginous . The possibility that these ribs are connected to an olfactory epithelium rather than turbinates has also been considered. Nonetheless, the possible presence of the turbinate suggests that Glanosuchus was able to breathe air quickly without drying the nasal passage, and therefore he may have been a warm-blooded animal . Glanosuchus is the oldest known therapside to have a turbinate, but it is believed that it was not entirely endothermic.
Systematics
Glanosuchus is a genus of Scylacosauridae , one of the most primitive family of therocephalia . One of his closest relatives is Pristerognathus . Cladogram according to Huttenlocker et al. (2011):
| Therocephalia |
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Individual evidence
- ↑ a b c R. Broom: On two new therocephalian reptiles ( Glanosuchus macrops and Pristerognathus baini ) . In: Transactions of the South African Philosophical Society . 15, 1904, pp. 85-88.
- ↑ a b c C. Zimmer: The Importance of Noses . In: Discover . 15, No. 8, 1994.
- ^ W. Maier, and Heever, J. van den: Middle ear structures in the Permian Glanosuchus sp. (Therocephalia, Therapsida), based on thin sections . In: Fossil Record . 5, No. 1, 2002, pp. 309-318. doi : 10.1002 / mmng.20020050119 .
- ↑ a b W.J. Hillenius: Turbinates in therapsids: Evidence for Late Permian origins of mammalian endothermy . In: evolution . 48, No. 2, 1994, pp. 207-229.
- ^ JA Ruben, and Jones, TD: Selective factors associated with the origin of fur and feathers . In: American Zoologist . 40, No. 4, 2000, pp. 585-596. doi : 10.1093 / icb / 40.4.585 .
- ↑ a b T.S. Kemp: The origin of mammalian endothermy: a paradigm for the evolution of complex biological structure . In: Zoological Journal of the Linnean Society . 147, 2006, pp. 473-488.
- ^ AK Huttenlocker, Sidor, CA; and Smith, RMH: A new specimen of Promoschorhynchus (Therapsida: Therocephalia: Akidnognathidae) from the Lower Triassic of South Africa and its implications for theriodont survivorship across the Permo-Triassic boundary . In: Journal of Vertebrate Paleontology . 31, No. 2, 2011, pp. 405-421. doi : 10.1080 / 02724634.2011.546720 .