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Hence it has not yet been possible to arrange these important fossils with any confidence in the ancestral series that descend from the Protamniotes to the Sauropsids on the one side and the Mammals on the other. Opinions are particularly divided as to the place in classification and the phylogenetic significance of the remarkable Theromorpha.
Another branch of the same order lived on the southern continent, Gondwana Land, and has left numerous remains in South Africa. The Diapsids are chiefly interesting, however, as the reputed ancestors of the colossal reptiles of the Jurassic age and the birds. * These Synapsid reptiles are more commonly known as Pareiasauria or Theromorpha.
As a matter of fact, the Theromorpha are nearer to the Mammals in the chief points of structure than any other reptiles. The whole structure of their pelvis and hind-feet has attained the same form as in the Monotremes, the lowest Mammals. The formation of the scapula and the quadrate bone shows an approach to the Mammals such as we find in no other group of reptiles.
The teeth also are already divided into incisors, canines, and molars. Nevertheless, it is very doubtful whether the Theromorpha really are in the ancestral line of the Sauromammals, or lead direct from the Tocosauria to the earliest Mammals.
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