Editing Onychophora (section)

=== Mouth and jaws ===
On the belly side of the second head segment is the labrum, a mouth opening surrounded by sensitive "lips". In the velvet worms, this structure is a muscular outgrowth of the [[throat]], so, despite its name, it is probably not [[Homology (biology)|homologous]] to the labrum of the Arthropoda and is used for feeding. Deep within the oral cavity lie the sharp, crescent-shaped "jaws", or [[mandible (arthropod mouthpart)|mandibles]], which are strongly hardened and resemble the claws of the feet, with which they are serially homologous;<ref name="Mayer2015" /> early in development, the jaw appendages have a position and shape similar to the subsequent legs.<ref name="Eriksson2003">{{cite journal |last1=Eriksson |first1=B. Joakim |last2=Tait |first2=Noel N. |last3=Budd |first3=Graham E. |date=January 2003 |title=Head development in the onychophoran ''Euperipatoides kanangrensis'' with particular reference to the central nervous system |journal=Journal of Morphology |volume=255 |issue=1 |pages=1–23 |doi=10.1002/jmor.10034 |pmid=12420318 |s2cid=42865895 |doi-access=free}}</ref> The jaws are divided into internal and external mandibles and their concave surface bears fine denticles. They move backward and forward in a longitudinal direction, tearing apart the prey, apparently moved in one direction by musculature and the other by hydrostatic pressure.<ref name="Mayer2015" /> The claws are made of sclerotised α-chitin, reinforced with phenols and quinones, and have a uniform composition, except that there is a higher concentration of calcium towards the tip, presumably affording greater strength.<ref name="Mayer2015" />

The surface of the mandibles is smooth, with no ornamentation.<ref name="Wright1989">{{cite journal |last1=Wright |first1=Jonathan C. |last2=Luke |first2=Barbara M. |year=1989 |title=Ultrastructural and histochemical investigations of ''peripatus'' integument |journal=Tissue & Cell |volume=21 |issue=4 |pages=605–25 |doi=10.1016/0040-8166(89)90012-8 |pmid=18620280}}</ref> The cuticle in the mandibles (and claws) is distinct from the rest of the body. It has an inner and outer component; the outer component has just two layers (whereas body cuticle has four), and these outer layers (in particular the inner epicuticle) are dehydrated and strongly tanned, affording toughness.<ref name="Wright1989" />