26 



The Mammalian Life of the Eocene Period. 



By A. Smith Woodward, LL.D., F.R.S., V.P.Z.S. 



he fossil backboned animals found in the Eocene and Oligocene 



* deposits of the Hampshire Basin are of general interest from 

 several points of view. In the first place, they agree with the plant- 

 remains from the pipe-clays of the Bournemouth cliffs in showing 

 that the climate of this region during the Eocene period was tropical 

 or sub-tropical. Secondly, like the plants, many of them represent 

 forms of life which have survived until the present day only in North 

 America and the warmer parts of South America. Among these 

 may be mentioned the gar-pikes (Lepidosteus), bow-fins {Amid), true 

 alligators, and opossums. Thirdly, they are still more interesting 

 as affording a glimpse of the warm-blooded quadrupeds (mammals) 

 at the time when they first began to flourish and multiply, and when 

 they were just showing signs of development into the several distinct 

 groups or "orders" which characterise the existing world. At the 

 end of the Cretaceous period, for some mysterious reason, the great 

 land-reptiles, sea-reptiles, and flying-reptiles disappeared in every 

 part of the globe. During the succeeding Eocene period the warm- 

 blooded mammals and birds quickly spread and took their place. 



This sudden appearance of the warm-blooded back-boned 

 animals in great numbers at the beginning of the Eocene period 

 both in Europe and in the New World is difficult to understand, 

 because the region in which their ancestors lived has not yet been 

 determined. There is reason to suppose that so far back as Triassic 

 times, when reptiles were just beginning to flourish, a few back-boned 

 animals actually reached the warm-blooded grade, and might indeed 

 be described as mammals and birds. Most of the Triassic reptiles 

 show a much closer approach to one or other of these two higher 

 groups than any which have existed since. It is not yet known, 

 however, to which area of land these fore-runners of the widespread 

 Eocene groups were restricted. It is merely demonstrated by a few 

 little creatures of the size of rats, which occasionally escaped over 

 the sea (perhaps in floating wood), that during the Jurassic and 

 Cretaceous periods, true mammals were living somewhere. The 

 jaws and limb-bones of some of these escapes are found in the 

 Purbeck Beds of Swanage, and teeth occur in the Wealden of Sussex. 



It is probable that most of these early mammals until the 

 Eocene period lived in trees, like the birds. In fact, some of them 

 whose remains occur in the Hordwell cliffs (Adapts), are essentially 



{Abstract of the Presidential Address delivered 20th November, 1909.) 



