PHYLOGENY, BIOGEOGRAPHY AND REPRODUCTIVE TRENDS IN THE ONYCHOPHORA

A cladistic analysis places the Onychophora between Polychaeta and Art hropoda. The 'Uniramia' concept is not supported. No justification was found for either onychophoran family to be considered ancestral. A cl adogram of fossil genera indicates the common ancestor to have long on copods, armoured plates and an annulated body. Later forms show adapta tions to life in reduced spaces. Physiological data suggest that the O nychophora became adapted to land via the littoral zone, before the La te Ordovician. Adhesive glands evolved for defence on land. Peripatops idae and Peripatidae were distinct by the late Triassic. The occurrenc e of onychophorans probably dates from post-Pliocene in New Guinea and southern Australia, and post-Early Cretaceous in Chile, the southern half of Southeast Asia, Mesoamerica and the Caribbean. After the Early Cretaceous, the peripatids of tropical Africa lost terrestrial contac t with those of South America. A new biogeographic technique, formaliz ed here under the name retrovicariance, indicates that the Peripatidae of Equatorial Africa and the Neotropics are sister-groups. Typical in breeding adaptations found in some onychophorans include: female-biase d sex ratios; gregarious development; relatively constant time of deve lopment and number of offspring in each clutch; male polygamy and shor ter life span; frequent sibmating in the microhabitat of development, and sperm storage by females, so that a single insemination fertilizes all ova.