This phylum's members have open circulatory systems containing sinuses that comprise the hemocoel, which became the main body cavity and returns hemolymph to the heart via ostia.
Diversifying both in late Silurian and early Cambrian periods, this taxon arose from the onychophorans, or walking worms. This phylum's members have open circulatory systems containing sinuses that comprise the hemocoel, which became the main body cavity and returns hemolymph to the heart via ostia. Marine gills and terrestrial tracheae lead air from pores in the cuticle into their bodies. They include the millipedes of Diplopoda and centipedes of Chilopoda and grow by molting a chitinous exoskeleton. FTP, name this protostomate phylum that is the largest of the animal kingdom and that contains barnacles, scorpions, crabs, trilobites, and insects.
Diversifying both in late Silurian and early Cambrian periods, this taxon arose from the onychophorans, or walking worms.
Arthropoda (or arthropods)