SKULL MAMMALS 



207 



Edentata (Bruta). — The old order of Edentates was largely based on dental 

 deficiencies, though most of its members had homodont teeth, from which, except 

 in a few fossils, enamel is lacking. All agree in a cranium rounded above, a 

 sagittal crest being rare, and all, except Bradyous, have a separate optic foramen. 

 Recent studies regard the group as polyphyletic and as formed of three separate 

 orders: Tubulidentata (aard vark of Africa); Phohdota {Manis, old world 

 anteaters); and Xenarthra (Edentates of America). 



Tubulidentata have the facial part of the skull very long; the zygomatic 

 arch complete, the zygomatic bone large; orbit and temporal fossa confluent, 

 there being a slight postorbital process. The occiput is nearly vertical and the 

 supraoccipital just enters the cranial roof, the greater part of which is formed 

 by the parietals. The nasals are long, the nares terminal, while nasals and 

 maxillae separate the small premaxillae from the frontals. The lacrimal has 

 a large facial portion which contains the foramen, and the optic foramen is 



Fig. 218. — Cranium of Orycteropus ("Weber, '04). a, alisphenoid ; /, frontal; 

 I, lacrimal; m, maxilla; n, nasal; o, orbitosphenoid; p, parietal; pi, palatine; pi, ptery- 

 goid; s, supraoccipital; sq, squamosal; /, tympanic; s, zygomatic. 



present. The order is separated from other Edentates by the presence of an 

 interparietal and a tympanohyal. The tympanic bone is open above and is not 

 ankylosed with the adjacent bones. The mandible is slender, highest behind, 

 and has a slender coronoid process and a small oval condyle. 



Pholidota (Effodentia). — The skull is much like that of Myrmecophaga 

 {infra) both having similar food (ants). It is long conical, rounded dorsally, 

 with orbit and temporal fossa continuous and shallow, and the zygomatic arch is 

 incomplete, the zygomatic bone being but a small remnant on the maxilla. 

 The supraoccipital extends on the cranial roof beyond the Hmit of the cerebellum, 

 the parietals forming most of the roof. The toothless maxillae do not meet the 

 frontals. The lacrimal, sometimes fused with the maxilla, is imperforate, the 

 lacrimal duct opening between the frontal and palatine. The squamosal has a 

 large air-filled vesicle above the tympanum, its cavities opening in front and 

 behind. The tympanic forms no part of the osseous meatus. The lower jaw is 

 reduced to a slender bar with condyloid and coronoid processes weaker than 

 in Echidna. 



Xenarthra. — The shape of the skull varies, the facial part being long in 

 Myrmecophaga (fig. 219), short in other genera, and the cranial cavity is long and 

 narrow. Only armadillos and Megatherium have a complete zygoma, it being 

 interrupted in others; but in all the zygomatic bone is large and in sloths has an 

 enormous ventral process (fig. 220). The supraoccipital enters the cranial roof 



