IV. VERTEBRATA: MAMMALIA, EDENTATA 



563 



marsupial bones and inflected angle of the jaw. The dentition, on the 

 other hand, has undergone a progressive, divergent development, so that 

 the distinctions are much more pronounced than in the marsupials, and 

 hence of importance in differentiating the orders. 



Order I. Edentata. 



A few families, poor in species, are united as Edentata because teeth are 

 absent or, more usually are markedly degenerate. Persistent functional in- 

 cisors are lacking, canines but rarely occur {Brady pus) ; molars may be present, 

 sometimes in great numbers {Priodon gigas, the large armadillo, has about a 

 hundred molars), but they are poorly rooted, prismatic, without enamel, and 

 usually monophyodont. Since the aardvark (Orycteropus) and Tatusia have 

 a heterodont milk dentition in embryonic life in which incisors occur, and 

 fossil edentates (Entelops) with complete dentition are known, the absence of a 

 replacement of the teeth is to be explained by degeneration. The great number 

 of sacral vertebrfe is striking, being as many as thirteen in some armadillos. 

 The order is essentially tropical, but one species entering the United States. 

 The oldest fossils occur in Patagonia (eocene or oligocene). 



Sub Order I. NOMARTHRA. Old World. FODIENTIA. Animals 

 with strong digging claws, long tail, and long, sticky tongue used in catching 

 insects. Orycteropus, aardvark, long snout, sparse bristly hair. SQUAjMATA. 

 Toothless, body covered with overlapping scales. Manis, pangolins of Asia and 



Fig. 6ii. — Manis longicaudala, pangolin (from Monteiro). 



Africa (fig. 6ii). Sub Order II. XENARTHRA. New World. VERMIL- 

 INGUIA, ant eaters. Resemble manids in toothless jaws, tongues, and claws, 

 but are hairy and lack scales. Myrmecopkaga. TARDIGRADA, sloths. 

 Hairy, rudimentary tail, and few teeth, long strong claws by which they hang 

 back downwards from limbs of trees. Brady pus, nine cervical vertehrx; Cholcrpus, 

 six cervicals. Fossils allied are Megatherium, as large as an elephant, Mylodon, 

 Megahmyx, extending to Pennsylvania. Crypotherium, as large as a cow, has 

 not long been extinct. LORICATA, armadillos. Body with armor of bony 

 plates, insectivorous. In the extinct Glyptodontid^ of South America the 

 plates fused to a continuous armor. One species twelve feet long. Dasy- 

 PODiD^; dermal armor in movable transverse plates; nocturnal. Genera based 

 upon the number of bands; Dasypus; Tatusia novemcincta*. 



