PHYLOGENY 



The cohort Unguiculata ( Latin : having claws or nails ) comprises eight 

 orders, of which two are extinct. Three of the six extant orders are quite 

 familiar: the order Insectivora itself; the order Chiroptera, or bats, which 

 are substantially just flying insectivores; and the order Primates, including 

 lemurs, monkeys, apes, and man. Three less well known orders are the 

 Dermoptera, including only the so called "flying lemur," which is not a 

 lemur and glides rather than flies; the Edentata, including such animals 

 as sloths, anteaters, and armadillos, all of which have rather few, oddly 

 developed teeth; and the Pholidota, including only the pangolin, an Old 

 World anteater which is not at all closely related to the Edentata. Of the 

 other cohorts, the Glires is most easily related to the Insectivora, This 

 cohort includes two very well known orders, the Rodentia, including a 

 great host of widely varied gnawing animals, and the Lagomorpha, in- 

 cluding rabbits, hares, and pikas. These were formerly united in one 

 order, but as long ago as the turn of the century, it was proposed that 

 they ought to be separated on the basis of characters of the skull and 

 teeth. Subsequent studies have consistently supported this decision, and 

 the paleontological record shows that the two orders do not converge as 

 one traces it back further. Hence Simpson has concluded that the inclu- 

 sion of the Rodentia and the Lagomorpha in a single cohort "is permitted 

 by our ignorance rather than sustained by our knowledge." 



The third cohort, the Mutica, includes only the single order Cetacea, 

 including whales and porpoises. This is perhaps the most aberrant of 

 mammalian orders, and its relationships are much befogged. Yet, as has 

 been pointed out in a previous chapter, its skeleton bears clear testimony 

 of descent from land mammals. 



The last cohort, Ferungulata (Latin: Ferae, beasts plus Ungulata, 

 hoofed), includes a large number of diverse orders, most of which are 

 extinct. The living orders of this series are the Carnivora, the Tubuliden- 

 tata, the Proboscidea, the Hyracoidea, the Sirenia, the Perissodactyla, and 

 the Artiodactyla. The first of these and the last two are among the most 

 successful of animals. One of the major characteristics of early mammalian 

 evolution was the development of large herbivores and of carnivores 

 adapted to prey upon these and upon other types of mammals. The latter 

 type is the order Carnivora, comprising such diverse forms as cats, wea- 

 sels, wolves, bears, and seals. Tlie herbivores have diversified into a great 

 many more orders, of which the dominant ones are the Perissodactyla, 

 which includes the horses and their allies with an odd number of toes; 

 and the Artiodactyla including the pigs, camels, deer, cattle, and other 

 hoofed animals with an even number of toes. 



The remaining living orders of ferungulates are represented by only 

 a few living forms. The Tubulidentata includes only the African aardvark, 

 an anteater which is unrelated to the several other animals called ant- 

 eaters. The Proboscidea includes the elephants and their extinct allies, 

 the mammoths. The Hyracoidea includes only the conies, small rabbit-like 

 ungulates of Africa and Asia. Finally, the Sirenia includes only the sea 

 cows. 



At first, the inclusion of the principal carnivores and herbivores within 



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