cleithrum

English

Etymology

From Ancient Greek κλεῖθρον (kleîthron).

Noun

cleithrum (plural cleithra)

1. (ichthyology) A large bone in fishes, which extends upward from the base of the pectoral fin and anchors to the cranium above the gills, forming the posterior edge of the gill chamber.
   • 1993, J. J. Videler, Fish Swimming, Springer, page 66:

     The secondary arch consists of four pieces of bone, the posttemporal, supracleithrum, cleithrum and postcleithrum. […] The cleithrum is the largest piece and the other elements are attached to it.

   • 2000, Melanie L. J. Stiassny, “Chapter 6: The Skeletal System”, in Gary Kent Ostrander, editor, The Laboratory Fish, Academic Press, page 116:

     The main components of which are, from dorsal to ventral, the post-temporal, supracleithrum, cleithrum and the postcleithra. […] The cleithra of either side of the body are connected with the pharyngeal jaw apparatus and with the urohyal by the bilateral pharyngocleithralis musculature and the median sternohyoideus muscle.

   • 2012, Jennifer A. Clack, Gaining Ground: The Origin and Evolution of Tetrapods, 2nd edition, Indiana University Press, page 212:

     In Ichthyostega (Figs 5.2, 5.11), Acanthostega (Fig. 5.20), and also in Hynerpeton (Fig. 5.28C, D) and Ventastega, the cleithrum was relatively reduced, though it was still a substantial dorsally extensive blade.

Derived terms

• anocleithrum
• cleithral
• extracleithrum
• postcleithrum
• supracleithrum