Kerygmachelidae is a family of gilled lobopodians (stem-

arthropods Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a Segmentation (biology), segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and Arth ...

with flapping trunk appendages and radial mouths) from the

Cambrian The Cambrian Period ( ; sometimes symbolized C with bar, Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million ...

period. Currently three genera are included in the family: '' Kerygmachela'' from the lower Cambrian of Greenland, ''

Utahnax ''Utahnax vannieri'' is a genus of kerygmachelid lobopodian from the Drumian of Utah, either from the Marjum or Wheeler formation. Description ''Utahnaxs preserved section is roughly long, with at least eight pairs of ventral flaps simila ...

'' from the middle Cambrian of Utah, and '' Mobulavermis'' from the lower-middle Cambrian of Nevada. These animals are characterized by well developed frontal appendages similar to other dinocaridids like the

radiodonts Radiodonta is an extinct order of stem-group arthropods that was successful worldwide during the Cambrian period. They may be referred to as radiodonts, radiodontans, radiodontids, anomalocarids, or anomalocaridids, although the last two origi ...

, except the ones present in these genera are horizontal to one another, and do not curve downward. These animals were most likely nektonic predators, using their large trunk flaps to swim in the water column, and using their frontal appendages to grab small-sized prey. Unlike other groups referred to as Lobopodians, this family lacks the distinctive legs (lobopods) that are usually seen in Lobopodian groups.

References

Cambrian arthropods Dinocaridida Prehistoric arthropod families Cambrian arthropods of North America {{paleo-arthropod-stub