Rostral bone
The term rostral bone, often shortened to simply rostral, refers to a number of bones present in the snout region of some vertebrates. The term "rostral" means referring to the rostrum, or snout. The term is used to refer to several non-homologous bones present in various vertebrate groups.
Evolution
[edit]"True" rostral bones
[edit]The rostral bones are dermal bones present in the front part of the skull of many fishes, where they sit between the nasals, anterior to the parietals, and posterior to the premaxillae. They are divided into the medial rostrals, intermediate rostrals, and lateral rostrals.[1][2] The rostral bones are believed to be derived from the premedian plate and rostral plate of placoderms.[3]
Rostral bones are ancestrally present among actinopterygians. The medial rostrals, which can be paired or single, are absent in most teleosts, but are present in elopomorphs where they are anteriorly fused to the internasal. Intermediate rostrals are similarly absent in many teleosts. The lateral rostral is more commonly present, and has historically been confused with the ethmoid region. [1][2]
The intermediate rostrals are absent in sarcopterygians.[1] In the clade Choanata (including tetrapods), the median rostral becomes fused to the premaxilla. The lateral rostral is believed to be homologous with the septomaxilla and is therefore retained in many tetrapods.[4]
Other bones called the rostral
[edit]
An unpaired median rostral is present in the frog Triprion. In this taxon it is a dermal bone and a neomorph anterior to the premaxilla.[5]
A similar neomorphic dermal bone is present at the tip of the snout in ceratopsian dinosaurs. In this clade, the bone opposes the predentary of the mandible, and would have been covered in a keratinous sheath forming a beak in life.[6]
Among pigs, a midline bone referred to as the rostral bone, also called the prenasal bone, is present in the snout, where it spans the external nares from the nasal to the premaxilla at the anterior end of the cartilaginous nasal septum. It forms the base of the disc-like mobile snout, and is thought to aid in rooting for food.[7] In peccaries and piglets, the element is cartilaginous, making it a rare example of a so-called "rostral" bone which is endochondral, not dermal. In elderly pigs the nasal septum may ossify, causing the rostral to become immobile; it is not known to fuse with the premaxilla.[8] A similar ossification has also been found in the water buffalo, where it forms a thin sword-like element.[9]
References
[edit]- 1 2 3 Jollie, Malcolm (1986). "A primer of bone names for the understanding of the actinopterygian head and pectoral girdle skeletons". Canadian Journal of Zoology. 64 (2). NRC Research Press: 365–379. doi:10.1139/z86-058. ISSN 0008-4301.
- 1 2 Kardong, Kenneth (2015). Vertebrates: Comparative Anatomy, Function (7th ed.). McGraw-Hill.
- ↑ Zhu, Min; Yu, Xiaobo; Ahlberg, Per Erik; Choo, Brian; Lu, Jing; Qiao, Tuo; Qu, Qingming; Zhao, Wenjin; Jia, Liantao; Blom, Henning; Zhu, You’an (2013). "A Silurian placoderm with osteichthyan-like marginal jaw bones". Nature. 502 (7470). Nature Publishing Group: 188–193. doi:10.1038/nature12617. ISSN 1476-4687.
- ↑ "3. Description and Systematics of Panderichthyid Fishes with Comments on Their Relationship to Tetrapods", Origins of the Higher Groups of Tetrapods, Cornell University Press, pp. 68–109, 2018-12-31, doi:10.7591/9781501718335-005, retrieved 2026-09-17
- ↑ Trueb, Linda (1993). "Patterns of cranial diversity in Lissamphibia". In Hanken, J.; Hall, B.K. (eds.). The skull: Patterns of Structural Diversity. Chicago: University of Chicago Press.
- ↑ Nabavizadeh, Ali (2023). "How Triceratops got its face: An update on the functional evolution of the ceratopsian head". The Anatomical Record. 306 (7): 1951–1968. doi:10.1002/ar.25196. ISSN 1932-8494.
- ↑ Owen, Joseph Thomas David (2013). Morphological Variation in Wild and Domestic Suids (Doctoral thesis). Durham University.
- ↑ Herring, Susan W. (1972-05-01). "The facial musculature of the suoidea". Journal of Morphology. 137 (1). John Wiley & Sons, Ltd: 49–62. doi:10.1002/jmor.1051370104. ISSN 1097-4687.
- ↑ B.v, Prakruthi; H.s, Patki; K.p, Surjith; C.v, Rajani; V.r, Indu; S, Maya; Abraham, John; P.s, Navya (2024-07-19). "Occurrence of Os Rostrale in a Buffalo (Bubalus bubalis) Skull". Uttar Pradesh Journal of Zoology. doi:10.56557/upjoz/2024/v45i154267.
