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The chelicerae (/ k ə ˈ l ɪ s ər iː /) are the mouthparts of the subphylum Chelicerata, an arthropod group that includes arachnids, horseshoe crabs, and sea spiders. Commonly referred to as " jaws ", chelicerae may be shaped as either articulated fangs , or as a type of pincers .
Carnivores have chelicerae that tear and crush prey, whereas herbivores can have chelicerae that are modified for piercing and sucking (as do parasitic species). In sea spiders, the chelicerae (also known as chelifores) are short and chelate and are positioned on either side of the base of the proboscis or sometimes vestigial or absent.
The chelicerae ("claw horns") that give the sub-phylum its name normally consist of three sections, and the claw is formed by the third section and a rigid extension of the second. [ 12 ] [ 19 ] However, spiders' have only two sections, and the second forms a fang that folds away behind the first when not in use. [ 16 ]
The cephalothorax, also called prosoma, is composed of two primary surfaces: a dorsal carapace and a ventral sternum.Most external appendages on the spider are attached to the cephalothorax, including the eyes, chelicerae and other mouthparts, pedipalps and legs.
Close-up of the chelicerae of a harvestman. The chelicerae consist of three segments, with the distal two forming a pincer [3] equipped with a row of teeth. Based on developmental gene expression data, the proximal segment is thought to be homologous to the femur and patella of the legs, the middle segment to the tibia through the tarsus of the legs, and the distal segment to the apotele (the ...
However, the basis of this hypothesis was immediately refuted by subsequent studies using Hox gene expression patterns, demonstrated the developmental homology between chelicerae and chelifores, with chelifore nerves innervated by a deuterocerebrum that has been rotated forwards, which was misinterpreted as protocerebrum by the aforementioned ...
The classical view was that the chelicerae were homologous to the second antennae of crustaceans (i.e., they are innervated from the tritocerebrum), a view based partly on the fact that the chelicerae were innervated from the same ganglion that innervates the labrum, which is the tritocerebrum in crustaceans and insects.
If the proportions between body length and chelicerae match those of its closest relatives, where the ratio between claw size and body length is relatively consistent, the specimen of Jaekelopterus that possessed the chelicera in question would have measured between 233 and 259 centimeters (7.64 and 8.50 ft), an average 2.5 meters (8.2 ft), in ...