Glanosuchus

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Glanosuchus
Temporal range: Late Permian
Skulls in side view, including that of the holotype (A-B)
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Synapsida
Clade: Therapsida
Clade: †Therocephalia
Family: †Scylacosauridae
Genus: †Glanosuchus
Broom, 1904
Species:
†G. macrops
Binomial name
†Glanosuchus macrops
Broom, 1904
Synonyms[1]
Genus synonymy
  • Cynariognathus
    Broom, 1931
  • Walteria
    Brink & Kitching, 1951
  • Ptomalestes
    Boonstra, 1954
  • Karroowalteria
    Kuhn, 1958
  • Crapartinella
    Mendrez, 1975
Species synonymy
  • Pristerognathus platyrhinus
    Broom, 1912
  • Cynariognathus platyrhinus
    Broom, 1931
  • Walteria skinneri
    Brink & Kitching, 1951
  • Cynariognathus paucioridens
    Boonstra, 1954
  • Ptomalestes avidus
    Boonstra, 1954
  • Alopecognathus skinneri
    Boonstra, 1969
  • Crapartinella croucheri
    Mendrez, 1975

Glanosuchus is a

endothermic
metabolism similar to modern mammals.

Description

Illustration of the skull from 1904

Glanosuchus macrops was first described in 1904 by South African paleontologist Robert Broom, who named the genus and species on the basis of a nearly complete holotype skull. The skull has been distorted during fossilization and the bone is indistinguishable from the surrounding matrix in some parts. In illustrating the holotype, Broom chose to reconstruct the skull of the species rather than draw the actual specimen.[2]

The skull of Glanosuchus is about 12 inches (30 cm) long.

canine teeth. The incisor teeth at the front of the upper jaw are also large and blade-like. There are six incisors on either side of the upper jaw, the furthest one being noticeably smaller than the rest. Five small pointed teeth are located behind each canine. The snout is wider in the front than it is behind, a usual feature among therapsids but present in several other related therocephalians. The nostrils are positioned at the tip of the snout and directed forward.[2]

Paleobiology

Hearing

Glanosuchus represents an early stage in the development of the mammalian

anular ligament, a ring-like structure that forms a seal between the end of the stapes and the rim of the vestibular foramen, was probably held in place by cartilage. The transfer of sound between the thin bony plate and the vestibular foramen in Glanosuchus was not as effective as it is in mammals, meaning that the animal had a less acute sense of hearing.[4]

Metabolism

Skulls shown from above, including that of the holotype (C)

Glanosuchus may have been one of the first therapsids to achieve endothermy, or warm-bloodedness. Endothermy is seen today in mammals, the only living group of therapsids.

synapsids sometime in the Permian or Triassic.[5]

While fur, commonly accepted as a clear indication of endothermy, has not been found in non-mammalian therapsids,[6] some skeletal features preserved in therapsid remains may be an indication of the metabolic rates of these animals. Modern mammals possess maxilloturbinates, which are a type of concha (shelf of bone) in the nasal cavity that collect moisture from inhaled air. As endotherms, mammals must breathe rapidly to supply enough oxygen for their high metabolisms. As oxygen passes into and out of the nasal cavity, it dries out the surrounding tissue. Water from inhaled air condenses on the maxilloturbinates, preventing the drying out of the nasal cavity and allowing mammals to inhale enough oxygen to support their high metabolisms.[3]

Reptiles and more primitive synapsids have conchae, but these plates of bone are involved in sensing smell rather than preventing desiccation.

cartilaginous. The possibility has also been raised that these ridges are associated with an olfactory epithelium rather than turbinates.[7] Nonetheless, the possible presence of maxilloturbinates suggests that Glanosuchus may have been able to rapidly breathe without drying out the nasal passage, and therefore could have been an endotherm.[3][5][7]

Glanosuchus is the earliest known therapsid to possess maxilloturbinates, but it shares features with reptiles that suggest it was not fully endothermic.

cynodonts, indicating that the two groups were convergently acquiring mammalian characteristics in the Permian and Triassic.[8] Although therocephalians died out by the Middle Triassic, cynodonts continued to diversify, giving rise to fully endothermic mammals in the Late Triassic.[5]

References

  1. ISSN 2410-4418
    .
  2. ^
    doi:10.1080/21560382.1904.9626433
    .
  3. ^ a b c d Zimmer, C. (1994). "The Importance of Noses". Discover. 15 (8).
  4. doi:10.1002/mmng.20020050119
    .
  5. ^
    PMID 28568303
    .
  6. ^
    doi:10.1093/icb/40.4.585
    .
  7. ^
    doi:10.1111/j.1096-3642.2006.00226.x
    .
  8. doi:10.1111/j.1439-0469.1996.tb00805.x
    .
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