Crassigyrinus

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Crassigyrinus
Temporal range:
Ma
3D skull reconstruction
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Sarcopterygii
Clade: Tetrapodomorpha
Clade: Stegocephali
Family: †Crassigyrinidae
von Huene, 1948
Genus: †Crassigyrinus
Watson, 1929
Type species
†Crassigyrinus scoticus
Watson, 1929

Crassigyrinus (from

Early Carboniferous Limestone Coal Group of Scotland and possibly Greer, West Virginia.[1]

Discovery

The type specimen was originally described as Macromerium scoticum and lacked a complete

paleontologists for decades with its apparent fish-like and tetrapod features.[2] It was traditionally placed within the group Labyrinthodontia along with many other early tetrapods. Some paleontologists have even considered it as the most basal crown group tetrapod, while others hesitate to even place it within the Tetrapoda superclass.[citation needed
]

Description

Life restoration

Crassigyrinus had a streamlined body up to 2 meters in length. Its limbs were tiny and virtually useless, implying that the animal was almost completely aquatic. Crassigyrinus had unusually large jaws, equipped with two rows of sharp

teeth, the second row having a pair of palatal fangs. Studies have shown that Crassigyrinus may have been able to open its mouth as wide as 60 degrees, which suggests that it was a powerful predator with a strong bite.[2]
This strongly suggests that it was ideally suited for catching fish, and the animal was probably a fast-moving predator.

Skull diagram

Several thickened bony ridges ran along the dorsal midline of the snout and between the eyes, and several paleontologists have suggested that they helped the skull to withstand stress when the animal bit prey. Crassigyrinus had large eyes, suggesting that it was either nocturnal, or lived in very murky water.[3] It possessed large otic (spiracular) notches, probably accommodating a spiracle rather than a tympanic membrane.[4]

Its peculiar stunted forelimbs were tiny and the humerus was only 35 mm long (the whole animal was about 1.5 m long). Various

lobe-finned fishes like Eusthenopteron.[5][6] The hindlimbs were much larger than the forelimbs, and in the pelvis the ilium lacked a bony connection to the vertebral column (a classic feature of aquatic tetrapods). Although there is evidence that the Crassigyrinus eventually lost its limbs,[7] there is counterevidence in that it used its limbs for movement,[8] as proven by healing in the bones in case of injury.[9] The fact that there is a need to heal the limbs must mean there was an importance of the limbs at some point, and was then lost. The tail, only known from a few vertebrae fragments, is assumed to have been long and laterally compressed.[2]

A crushed skull from the Dora bonebed near Cowdenbeath was described by Panchen (1985).[5] The skull was redescribed by Porro et al. (2023), based on a digital reconstruction derived from CT scans. The 1985 reconstruction of the skull was much taller and narrower than in most early tetrapods, though the 2023 reconstruction is relatively low and broad.[10]

Paleobiology

Crassygyrinus was an aquatic predator. It was capable of opening its jaws widely at a 60 degree angle, with a powerful bite with rapid jaw closure, allowing it to grasp and consume relatively large prey items.[10]

References

  1. ^ Godfrey, S. J. 1988. Isolated tetrapod remains from the Carboniferous of West Virginia. Kirtlandia 43, 27-36.
  2. ^
    Jennifer A. Clack, Indiana University Press 2002, from Google Books
  3. ISBN 1-84028-152-9
    .
  4. Vertebrate Palaeontology
    3rd edition. Blackwell Publishing
  5. ^ a b Panchen, A. L. 1985. On the amphibian Crassigyrinus scoticus Watson from the Carboniferous of Scotland. Philosophical Transactions of the Royal Society of London B 309, 505-568.
  6. ^ Panchen, A. L. 1991. The early tetrapods: classification and the shapes of cladograms. In Schultze, H.-P. & Trueb, L. (eds) Origins of the Higher Groups of Tetrapods, Controversy and Consensus. Comstock/Cornell University Press (Ithaca and London), pp. 110-144.
  7. ISSN 0008-4077
    .
  8. S2CID 225160164
    .
  9. S2CID 204145235
    .
  10. ^
    S2CID 258475146
    .

External links
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