Let us now look to the mutual affinities of extinct and living species. They
all
fall
into one grand natural system;
and this fact is at once explained on the principle of descent. The more ancient any form is, the more, as a general rule, it differs from living forms. But, as Buckland long ago remarked, all fossils can
be classed either in still existing groups, or between them. That the extinct forms of life help to fill up the wide
intervals between existing genera, families, and orders, cannot be disputed. For if
we confine our attention either to the living or to the extinct alone,
the series is far less perfect than if we combine both into one general system.
With respect to the Vertebrata, whole pages could be filled with striking illustrations from our great palæontologist, Owen, showing how With respect to the Vertebrata, whole pages could be filled with striking illustrations from our great palæontologist, Owen, showing how 1859 1860 1861 |
With respect to the vertebrata, whole pages could be filled with striking illustrations from our great palæontologist, Owen, showing how 1866 |
With respect to the vertebrata, whole pages could be filled with illustrations from Owen, showing how 1869 |
In the writings of Professor Owen we continually meet with the expression of generalised forms, as applied to 1872 |
extinct animals
fall
in between existing groups. Cuvier ranked the Ruminants and Pachyderms, as the two
most distinct orders of mammals;
but Owen has discovered
so many fossil links,
that he
has had to alter the whole classification
of these two orders;
and has placed certain pachyderms in the same sub-order with ruminants:
for example, he dissolves by fine
gradations the apparently wide difference
between the pig and the camel. ↑5 blocks not present in 1859 1860 1861 1866 1869; present in 1872 | The Ungulata or hoofed quadrupeds are now divided into the even-toed or odd-toed divisions; but the Macrauchenia of S. America connects to a certain extent these two grand divisions.
No one will deny that the Hipparion is intermediate between the existing horse and certain older ungulate forms.
What a wonderful connecting link in the chain of mammals is the Typotherium from S. America, as the name given to it by Professor Gervais expresses, and which cannot be placed in any existing order.
The Sirenia form a very distinct group of mammals, and one of the most remarkable peculiarities in the existing dugong and lamentin is the entire absence of hind limbs, without even a rudiment being left; but the extinct Halitherium had, according to Professor Flower, an ossified thigh-bone "articulated to a well-defined acetabulum in the pelvis," and it thus makes some approach to ordinary hoofed quadrupeds, to which the Sirenia are in other respects allied.
The cetaceans or whales are widely different from all other mammals, but the tertiary Zeuglodon and Squalodon, which have been placed by some naturalists in an order by themselves, are considered by Professor Huxley to be undoubtedly cetaceans, "and to constitute connecting links with the aquatic carnivora."
|
↑1 blocks not present in 1859 1860 1861 1866; present in 1869 1872 | Another distinguished palæontologist, M. Gaudry, shows that very
many of the fossil mammals discovered by him in Attica connect in the plainest manner
existing genera.
|
In regard to the Invertebrata, Barrande, and a higher authority could not be named, asserts that he is every day taught
that that 1859 1860 1861 | that, 1866 |
palæozoic animals, though belonging to the same orders, families, or genera with those living at the present day, palæozoic animals, though belonging to the same orders, families, or genera with those living at the present day, 1859 |
Palæozoic animals, though belonging to the same orders, families, or genera with those living at the present day, 1860 1861 |
although palæozoic animals can certainly be classed under existing groups, yet that at this ancient period these groups 1866 |
were not
at this early epoch limited in such distinct groups at this early epoch limited in such distinct groups 1859 1860 1861 |
so distinctly separated from each other 1866 |
as they
now now 1859 1860 1861 | now 1866 |
are. are. 1859 1860 1861 |
are at the present time. 1866 |
↑2 blocks not present in 1859 1860 1861 1866 1869; present in 1872 | Even the wide interval between birds and reptiles has been shown by the naturalist just quoted to be partially bridged over in the most unexpected manner, on the one hand, by the ostrich and extinct Archeopteryx, and on the other hand, by the Compsognathus, one of the Dinosaurians— that group which includes the most gigantic of all terrestrial reptiles.
Turning to the Invertebrata, Barrande asserts, and a higher authority could not be named, that he is every day taught that, although palæozoic animals can certainly be classed under existing groups, yet that at this ancient period the groups were not so distinctly separated from each other as they now are.
|
|