It seems at the same time almost a certainty
that others of the three-toed impressions of the Connecticut
sandstones were in truth produced by Birds, since it is doubtful
if the bipedal mode of progression was more than an occasional
thing amongst the Deinosaurs, and the greater number of the many
known tracks exhibit no impressions of fore-feet. Upon the whole,
therefore, we may, with much probability, conclude that the great
class of Birds (_Aves_) was in existence in the Triassic period.
If this be so, not only must there have been quite a number of
different forms, but some of them must have been of very large
size. Thus the largest footprints hitherto discovered in the
Connecticut sandstones are 22 inches long and 12 inches wide,
with a proportionate length of stride. These measurements indicate
a foot four times as large as that of the African Ostrich; and the
animal which produced them--whether a Bird or a Deinosaur--must
have been of colossal dimensions.
[Illustration: Fig. 156.--Lower jaw of _Dromatherium sylvestre_.
Trias, North Carolina. (After Emmons.)]
[Illustration: Fig. 157.--a, Molar tooth of _Micro estes antiquus_,
magnified; b, Crown of the same, magnified still further. Trias,
Germany.]
[Illustration: Fig. 158.--The Banded Ant-eater (_Myrmecobius
fasciatus_) of Australia.]
Finally, the Trias completes the tale of the great classes of the
Vertebrate sub-kingdom by presenting us with remains of the first
known of the true Quadrupeds or _Mammalia_.
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