Caudal rib

A caudal rib is a rib that occurs in the tail of a vertebrate. They are commonly present on the more anterior caudal vertebrae of reptiles and early tetrapods. In many taxa, they are fused with the vertebrae,[1] though they were separate in some early reptiles such as protorothyrids[2] and the suture between the rib and vertebra is sometimes visible in crocodilians.[3] In taxa where the caudal ribs are fused to the vertebrae, the terms "transverse process" and "caudal rib" are sometimes used interchangeably, but the caudal rib may form only part of the transverse process.[4] Some species, such as the tuatara, have fused caudal ribs in the anterior portion of the tail and transverse processes that are simple projections of the vertebra, not separately-ossifying ribs, in the more posterior portion of the tail.[5] Ribs fused to the vertebra may also be called pleurapophyses.[3]

In tetrapodomorph fish such as Eusthenopteron, the ribs do not extend into the tail region. Caudal ribs first appear in Tiktaalik and early tetrapods such as Acanthostega and Ichthyostega.[6]

References

  1. ^ Romer, Alfred Sherwood (1956). Osteology of the Reptiles.
  2. ^ Carroll, R L (1982). "Early evolution of reptiles". Annual Review of Ecology and Systematics. 13 (1): 87–109. doi:10.1146/annurev.es.13.110182.000511. ISSN 0066-4162.
  3. ^ a b Hoffstetter, Robert; Gasc, Jean-Pierre (1969). "Vertebrae and ribs of modern reptiles". In Gans, Carl; Bellairs, Angus d'A.; Parsons, Thomas S. (eds.). Biology of the Reptilia: Volume 1: Morphology A. London and New York: Academic Press. pp. 201–310.
  4. ^ Gallina, Pablo Ariel; Otero, Alejandro (2009-04-30). "Anterior caudal transverse processes in sauropod dinosaurs: morphological, phylogenetic and functional aspects". Ameghiniana. 46 (1): 165–176. ISSN 0002-7014.
  5. ^ Beccari, Victor; Jones, Marc E H; Villa, Andrea; Martino, Roberta; Regnault, Sophie; Glaw, Frank; Rauhut, Oliver W M (2026-04-01). "The axial skeleton of the tuatara (Rhynchocephalia: Sphenodon): insights on intraspecific variability, ontogeny, sexual dimorphism, and remarks on fossil taxa". Zoological Journal of the Linnean Society. 206 (4). doi:10.1093/zoolinnean/zlaf135. ISSN 0024-4082.
  6. ^ Stewart, Thomas A.; Lemberg, Justin B.; Hillan, Emily J.; Magallanes, Isaac; Daeschler, Edward B.; Shubin, Neil H. (2024-04-09). "The axial skeleton of Tiktaalik roseae". Proceedings of the National Academy of Sciences. 121 (15): –2316106121. doi:10.1073/pnas.2316106121. eISSN 1091-6490. ISSN 0027-8424.


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