Dolphins appear in the Miocene.
Finally, the Edentates (sloths, anteaters, and armadilloes) are
represented in a very primitive form in the early Eocene. They
are then barely distinguishable from the Condylarthra and
Creodonta, and seem only recently to have issued from a common
ancestor with those groups. In the course of the Tertiary we find
them--especially in South America, which was cut off from the
North and its invading Carnivores during the Eocene and
Miocene--developed into large sloths, armadilloes, and anteaters.
The reconnection with North America in the Pliocene allowed the
northern animals to descend, but gigantic sloths (Megatherium)
and armadilloes (Glyptodon) flourished long afterwards in South
America. The Megatherium attained a length of eighteen feet in
one specimen discovered, and the Glyptodon often had a dorsal
shield (like that of the armadillo) from six to eight feet long,
and, in addition, a stoutly armoured tail several feet long.
The richness and rapidity of the mammalian development in the
Tertiary, of which this condensed survey will convey some
impression, make it impossible to do more here than glance over
the vast field and indicate the better-known connections.
Pages:
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410