Hemimandible of Trimerorhachis; the splenial (labeled "sp") is visible on the interior surfaceSkull and jaws diagram of the primitive synapsid Dimetrodon, showing location of the 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]
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.