noun, plural: chelicerae
Either of the first set of appendages of the chelicerates (e.g. arachnids, horseshoe crabs, etc.)
Chelicerates, such as arachnids, sea spiders, and horseshoe crabs, are known for having segmented bodies with paired jointed limbs or appendages. The first pair of these appendages is termed chelicerae, which etymologically means jaws or horns and from where the name of this group is derived.
Chelicera pertains to any of the two in a pair of appendages that arise from segment two of chelicerates. They are typically found ahead of the mouth. Most chelicerae are made up of three sections except for spider chelicerae that are comprised of only two sections. There are three kinds of chelirae: (1) jackknife chelicerae (as seen in Tetrapulmonata species), (2) scissor chelicerae (such as those in Pseudoscorpiones and Solfifugae), and (3) 3-segmented chelate chelicerae (such as those in Scorpiones and Opiliones).1
Certain spiders, particularly the venomous kinds, have chelicerae that contain or are connected to venom glands. These spiders use them to inject venom for protection against a perceived threat or for capturing prey.
Word origin: Ancient Greek khēlḗ (“jawbone”) + kéras (“horn”)
1 Rainer F. Foelix (1996). Biology of Spiders (2nd ed.).Oxford University Press.