Splenial

The splenial is a small bone in the lower jaw of reptiles, amphibians and birds, usually located on the lingual side (closest to the tongue) between the angular and surangular.^[1]^[2] The splenial and coronoid are together known as the paradental elements.^[3] In non-tetrapod vertebrates, the splenial is known as the first infradentary and forms part of the infradentary series along with the postsplenial and angular.^[4]^[5] The earliest known taxon with infradentary bones is the placoderm Entelognathus, while they were absent in the earlier-diverging Qilinyu.^[6] Splenials are present in non-mammalian synapsids, but lost in mammals, though there are some claims of a vestigial splenial in some early mammals.^[3]

Skull and jaws diagram of the primitive synapsid *Dimetrodon*, showing location of the splenial

References

↑ Romer, A. S. (1956). Osteology of the Reptiles. 772 pp. Chicago & London.
↑ Watson, D. M. S. (1912). LXVII.—On some reptilian lower jaws. Journal of Natural History, 10(60), 573-587.
1 2 Rougier, Guillermo W.; Martinelli, Agustín G.; Forasiepi, Analía M.; Novacek, Michael J. (2007). "New Jurassic Mammals from Patagonia, Argentina: A Reappraisal of Australosphenidan Morphology and Interrelationships". American Museum Novitates. 3566 (1): 1. doi:10.1206/0003-0082(2007)507[1:NJMFPA]2.0.CO;2. ISSN 0003-0082.
↑ Jeffery, Jonathan E (2003). "Mandibles of rhizodontids: anatomy, function and evolution within the tetrapod stem-group". Transactions of the Royal Society of Edinburgh: Earth Sciences. 93: 255–276.
↑ Zhu, You-An; Ahlberg, Per A.; Zhu, Min (2018-12-31). "The Evolution of Vertebrate Dermal Jaw Bones in the Light of Maxillate Placoderms". In Johanson, Zerina; Underwood, Charlie; Richter, Martha (eds.). Evolution and Development of Fishes (1 ed.). Cambridge University Press. pp. 71–86. doi:10.1017/9781316832172.005. ISBN 978-1-316-83217-2.
↑ Zhu, Min; Ahlberg, Per E.; Pan, Zhaohui; Zhu, Youan; Qiao, Tuo; Zhao, Wenjin; Jia, Liantao; Lu, Jing (2016-10-21). "A Silurian maxillate placoderm illuminates jaw evolution". Science. 354 (6310): 334–336. doi:10.1126/science.aah3764. eISSN 1095-9203. ISSN 0036-8075.

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[Romer1956-1] Romer, A. S. (1956). Osteology of the Reptiles. 772 pp. Chicago & London.

[Watson1912-2] Watson, D. M. S. (1912). LXVII.—On some reptilian lower jaws. Journal of Natural History, 10(60), 573-587.

[Rougier2007-3] 1 2 Rougier, Guillermo W.; Martinelli, Agustín G.; Forasiepi, Analía M.; Novacek, Michael J. (2007). "New Jurassic Mammals from Patagonia, Argentina: A Reappraisal of Australosphenidan Morphology and Interrelationships". American Museum Novitates. 3566 (1): 1. doi:10.1206/0003-0082(2007)507[1:NJMFPA]2.0.CO;2. ISSN 0003-0082.

[Jeffrey2003-4] Jeffery, Jonathan E (2003). "Mandibles of rhizodontids: anatomy, function and evolution within the tetrapod stem-group". Transactions of the Royal Society of Edinburgh: Earth Sciences. 93: 255–276.

[Zhu2018-5] Zhu, You-An; Ahlberg, Per A.; Zhu, Min (2018-12-31). "The Evolution of Vertebrate Dermal Jaw Bones in the Light of Maxillate Placoderms". In Johanson, Zerina; Underwood, Charlie; Richter, Martha (eds.). Evolution and Development of Fishes (1 ed.). Cambridge University Press. pp. 71–86. doi:10.1017/9781316832172.005. ISBN 978-1-316-83217-2.

[Zhu2016-6] Zhu, Min; Ahlberg, Per E.; Pan, Zhaohui; Zhu, Youan; Qiao, Tuo; Zhao, Wenjin; Jia, Liantao; Lu, Jing (2016-10-21). "A Silurian maxillate placoderm illuminates jaw evolution". Science. 354 (6310): 334–336. doi:10.1126/science.aah3764. eISSN 1095-9203. ISSN 0036-8075.

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