Basioccipital

Skull of Plateosaurus in posterior view. Basioccipital is labeled as bo.

The basioccipital is a bone present in the posterior region of the skull in vertebrates. It encloses the ventral margin of the foramen magnum. It is a part of the chondrocranium.

Evolution

Unlike most of the skull, the basioccipital develops from somites, which otherwise develop into the vertebrae. This has led to the hypothesis that the basioccipital has its evolutionary origin as a modified vertebra. However, this hypothesis has been contested on the basis of embryonic evidence in actinopterygian fishes.

The basioccipital is present in basal amniotes, where it forms the majority of the occipital condyle. This is the role it takes in most modern and fossil sauropsids.

In humans, the basioccipital fuses with the supraocipitals and the exoccipitals to form the basilar part of the occipital bone.

References

  1. 1 2 3 Romer, A. S. (1956). Osteology of the Reptiles. University of Chicago Press.
  2. 1 2 Kardong, Kenneth (2015). Vertebrates: Comparative Anatomy, Function (7th ed.). McGraw-Hill.
  3. ↑ Couly, Gérard F.; Coltey, Pierre M.; Douarin, Nicole M. Le (1993-02-01). "The triple origin of skull in higher vertebrates: a study in quail-chick chimeras". Development. 117 (2): 409–429. doi:10.1242/dev.117.2.409. ISSN 0950-1991. PMID 8330517.
  4. ↑ Kant, Rajiv; Goldstein, Ronald S. (1999-12-15). "Plasticity of Axial Identity among Somites: Cranial Somites Can Generate Vertebrae without Expressing Hox Genes Appropriate to the Trunk". Developmental Biology. 216 (2): 507–520. doi:10.1006/dbio.1999.9512. ISSN 0012-1606. PMID 10642789.
  5. ↑ Britz, Ralf; Johnson, G. David (2010). "Occipito-vertebral fusion in actinopterygians: conjecture, myth and reality. Part 1: Non-teleosts". hdl:10088/9748. {{cite journal}}: Cite journal requires |journal= (help)
  6. ↑ Johnson, G. David; Britz, Ralf (2010). "Occipito-vertebral fusion in Actinopterygians: conjecture, myth and reality. Part 2: Teleosts". Origin and Phylogenetic Interrelationships of Teleosts: 95–110.