ORDER V EDENTATA 89 



Balaena Linn, are found sparingly in the latest Tertiary deposits and in the 

 Pleistocene of Europe. 



Order V, EDENTATA (Bruta Linn.^) 



Dentition usually consisting only of prismatic cheek teeth without enamel, some- 

 times entirely ivanting. The terminal phalanges are long, pointed and laterally 

 compressed claws, seldom hoof -like. Skin covered with hair, horny or bony plates. 



The Edentata constitute among placental mammals a distinct group and 

 were ranked by Cuvier as parallel to the Ungulates and Unguiculates. The 

 Edentata differ principally from other mammals in that they have (1) a denti- 

 tion, as a rule, monophyodont, consisting of prismatic teeth and lacking 

 incisors and canines; (2) no enamel is present in the teeth of all recent forms; 

 (3) a variable number of dorsal and caudal vertebrae is observed in several 

 genera ; (4) fusion of the ischium and sacral vertebrae occurs ; (5) there is 

 a common urinary and genital duct in the female ; and (6) a very well 

 developed osseous exoskeleton is present in armadillos and their allies. 



As to the origin of the group, Nomarthra are known to have existed in 

 the Eocene or Oligocene of Europe, and armadillos were abundant during the 

 same periods in South America. The Taeniodonta of the North American Lower 

 Eocene have been claimed as ancestors of the Gravigrada. Although the time 

 of their appearance would favour this supposition, there are serious morpho- 

 logical objections, and this view is not generally accepted. The first true 

 Gh'avigrada are found in the Pyrotherium beds (Lower Miocene) of South 

 America. 



The vertebral column consists of well - differentiated cervical, dorsal, 

 lumbar, sacral and caudal regions. As a rule, the cervical vertebrae are 

 7 in number, rarely 9. The number of dorsal vertebrae varies from 

 12 to 24, that of the lumbar from 3 to 9. In the Glyptodontia several 

 of the dorsal vertebrae, together with their spinous processes, are fused 

 to form an immovable tube. This is also the case with the lumbar and 

 post-sacral vertebrae. The posterior caudal vertebrae also become a more or 

 less inflexible mass of bone on account of the anchylosis of the centra ; and 

 the anterior and posterior cervical vertebrae are likewise fused together. 



The skull is often elongated, and at other times very short and deep. 

 In most cases the top of the skull is rounded or flat, and only in the 

 Gravigrada do the parietals sometimes form a small crest. The pre- 

 maxillary bones are very weakly developed in all Edentata, and rarely 

 serve as a lateral boundary of the large nostrils. The zygomatic arch is 



^ Ameghino, Flor., Contribucion al conocimiento de los mamiferos fosiles de la Eepublica 

 Argentina. Aetas Acad. Nac. Cieucias Cordoba, 1889. — Les Edeutes fossiles de France et 

 d'Allemagne. Anal. Mus. Nac. Buenos Aires, vol. xiii., 1905. — Burmeister, H. Anal. Mus. Nac. 

 Buenos Aires, Entrega i-xii. — Cope, E. D., The Edentata of North America. Amer. Naturalist, 

 1889. — Filhol, H. Annales Scienc. Nat., Zoologie et Paleont., vol. xvi., 1894. — Lydekker, R., 

 Paleontologia Argentina, iii. Anal. Mus. La Plata, 1894. — Owen, Richard, Description of the 

 skeleton of an extinct gigantic sloth {Mylodon robiistus), 1842. — On the Megatherium. Philos. 

 Trans., 1851-59.— On Glyptodon. Proc. Geol. Soc, iii., \?>ZQ.—Reinhardt, J. Vetensk. Selsk. 

 Skin. Kj^benhavn., 5. Raekke xi. ; xii. — Scott, W. JR., Reports of the Princeton Univers. Exped. 

 to Patagonia. Palaeontology, vol. v., 1903, 1904. — Brown, Bar7in,m, Brachyostracon, a new 

 genus of Glyptodouts from Mexico. Bull. Amer. Mus. Nat. Hist., 1912, vol. xxxi. 



