Cephalic arterial pattern in New World edentates and Old World pangolins with special reference to their phylogenetic...

The cephalic arterial pattern in edentates and pangolins is described on the basis of 9 corrosion specimens, representing all the classical superfamilies, with special reference to their phylogenetic relationship and taxonomy. In this respect, the importance of the manner in which the external carotid artery system annexes the stepedial area of supply and of the course of the internal carotid artery in relation to the tympanic cavity is emphasized. The investigation does not indicate any special relationship between the New World edentates and the Old World pangolins, whereas the marked difference in the course of the internal carotid artery in recent edentates stresses the independent development of the South American anteaters compared with that of the two other edentate groups (armadillos and tree sloths). Most probably the edentates were divided very early into two main lines which have evolved independently since the early Tertiary, i.e. one for the anteaters and one for the tree sloths and armadillos, indicating a probable subdivision of the true edentates into two suborders. This subdivision is markedly different from the classical two-fold division of the edentates.