Epipterygoid

Bone of the head or neck

The epipterygoid is a paired cranial bone present in many tetrapods. It acts as a vertical strut connecting the pterygoid bone of the palate to the outer surface of the braincase or the underside of the skull roof. The epipterygoid is an endochondral bone (derived from cartilage), similar to the braincase but unlike most other bones in the skull. In squamates, the epipterygoid generally has a slender rod-like shape, and is also known as the columella cranii.[1] The epipterygoid is considered to be homologous to the alisphenoid bone of mammals.[2] Though present in many extinct archosaurs, it has been independently lost in modern crocodilians and birds.[3][4]

References

  1. ^ Jollie, Malcolm T. (1960). "The head skeleton of the lizard". Acta Zoologica. 41 (1–2): 1–64. doi:10.1111/j.1463-6395.1960.tb00474.x. ISSN 1463-6395.
  2. ^ Hopson, James A.; Rougier, Guillermo W. (1993-01-01). "Braincase structure in the oldest known skull of a therian mammal; implications for mammalian systematics and cranial evolution". American Journal of Science. 293 (A): 268–299. doi:10.2475/ajs.293.A.268. ISSN 0002-9599.
  3. ^ Holliday, Casey M.; Witmer, Lawrence M. (2009-09-12). "The epipterygoid of crocodyliforms and its significance for the evolution of the orbitotemporal region of eusuchians". Journal of Vertebrate Paleontology. 29 (3): 715–733. doi:10.1671/039.029.0330. ISSN 0272-4634.
  4. ^ Clark, James M.; Welman, Johann; Gauthier, Jacques A.; Parrish, J. Michael (1993-03-18). "The laterosphenoid bone of early archosauriforms". Journal of Vertebrate Paleontology. 13 (1): 48–57. doi:10.1080/02724634.1993.10011487. ISSN 0272-4634.
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Bones in the tetrapod skeleton
Skull
Cranium
Skull roof
Composite bones
Braincase
Composite bones
  • Occipital (Supraoccipital+Exoccipital+Basioccipital)
  • Otoccipital (Exoccipital+Opisthotic)
  • Parabasisphenoid (Parasphenoid+Basisphenoid)
  • Petrosal (Prootic+Opisthotic)
  • Temporal (Squamosal+Petrosal+Ectotympanic)
Palate
Mandible
Hyoid
Postcranial skeleton
Axial
Vertebrae
Ribs
Appendicular
Pectoral girdle
Forelimb
Manus
Carpus
Distal carpals
  • Distal carpal 1 (Trapezium)
  • Distal carpal 2 (Trapezoid)
  • Distal carpal 3 (Capitate)
  • Distal carpal 4 (Hamate)
  • Distal carpal 5
Pelvic girdle
Hindlimb
Pes
Tarsus
Proximal tarsals
Centralia
  • Centrale 1
  • Centrale 2
  • Centrale 3
  • Centrale 4
Distal tarsals
Composite tarsals
  • Astragalus (Talus) (Tibiale+Intermedium+Centrale 3+4)
  • Navicular (Centrale 1+2)
  • Cuboid (Distal tarsal 4+5)
Miscellaneous
  • Parentheses denote bones that receive a different name in particular clades
  • Italics denote neomorphic bones present only in particular clades
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