298 annual report Smithsonian institution, 1952 



Fishes: Bowfin (Amia). 



Amphibians: Salamanders and their relatives (Urodela). 



Reptiles: Lizards (Lacertilia). 



Birds: Tinamous (Tinamidae). 



Mammals: Insectivores (Insectivora, especially the Tenrecoidea). 



Under the present highly diversified conditions on the earth the 

 mammals, the most adaptable of the vertebrates, are the dominant 

 type. The mammals are independent of external water, bright illu- 

 mination, and heat from the sun ; they have an insulating covering of 

 hair (or blubber) and sweat glands; all the senses are highly devel- 

 oped ; they have powerful limbs adapted for walking, running, jump- 

 ing, climbing, swimming, or flying, and strong jaws with diversified 

 teeth. Mammals are viviparous, the female in most cases raising the 

 young in a nest or den and always feeding them with a secretion from 

 her body. In the marsupials the young are born in a very undevel- 

 oped condition and find their own way to the mother's pouch where 

 they attach themselves to a nipple ; there is therefore no necessity for 

 a resting period for the females while producing young. The mar- 

 supials are thus especially well adapted to survive in areas subject to 

 drought or other adverse conditions when the daily feeding range of 

 the individuals must be greatly increased. The rodents are small, 

 and most of them very prolific. This enables them to withstand ad- 

 verse conditions, for they can become restricted to very small areas 

 and when conditions improve promptly spread out again. The young 

 of the hoofed mammals, the cetaceans, and some others are born essen- 

 tially as small adults so that they are able from the first to accompany 

 the mother, or the herd, in its wanderings. 



Quite as successful as the mammals are the birds. Ecologically the 

 birds are complementary to the mammals rather than competitors. 

 Birds and mammals agree in being warm-blooded with an insulating 

 coating of feathers or hair; in being independent of a continuous 

 supply of external moisture ; in having usually more or less helpless 

 young that require feeding and tending; and in being largely plant 

 feeders, at least as adults. Birds differ from mammals in their de- 

 pendence on strong illumination, in possessing the power of flight 

 (shared, however, with the bats), in being oviparous, in feeding the 

 young, though with material collected by the adults instead of with 

 a secretion from the mother, and in being toothless, which somewhat 

 limits their feeding range as compared, for instance, with rodents, 

 the dominant mammals. 



Whereas mammals are predominantly ground feeders with a few 

 arboreal, aerial, and aquatic types, birds feed mainly in bushes and 

 trees though many feed on the ground or in water, and some are aerial 

 feeders. Except for the large herbivorous types mammals are mainly 

 nocturnal, birds wholly diurnal or crepuscular. The bats consume the 



