Recently,
this dichotomy has been explained as being linked to Jurassic–
Pliocene biogeography. These two onychophoran groups
diverged some 200 mya, when a vast desert separated the northern
and southern groups on the ancient southern continental
mass called Gondwana. Contemporary distribution of onychophorans
corresponds to the modern separated continental remnants
of Gondwana. In fact, the fossil record of onychophorans,
which traces from the middle Cambrian period, has been used
to reassemble the historical pattern of drifting continents.