Amniotes

One of the most salient characteristics of the Amniotes is the complete loss of the gills.

The Evolution of Man — Volume 2 Ernst Heinrich Philipp August Haeckel 1876

One striking embryonic character of the Amniotes is the great curve of the head and neck in the embryo.

The Evolution of Man — Volume 2 Ernst Heinrich Philipp August Haeckel 1876

Modern Reptiles are derived from the Ancestral Amniotes, just as are Modern Mammals.

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They share many characteristic of the Ancestral Amniotes, but do not (generally) share the derived characteristics.

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Hence Hatteria is the phylogenetically oldest of all living reptiles, an isolated survivor from the Permian period, closely resembling the common ancestor of the Amniotes.

The Evolution of Man — Volume 2 Ernst Heinrich Philipp August Haeckel 1876

We also find an advance in the structure of several of the internal organs of the Amniotes which raises them above the highest of the anamnia.

The Evolution of Man — Volume 2 Ernst Heinrich Philipp August Haeckel 1876

The instructive group of the Permian Tocosauria, the common root from which the divergent stems of the Sauropsids and mammals have issued, merits our particular attention as the stem-group of all the Amniotes.

The Evolution of Man — Volume 2 Ernst Heinrich Philipp August Haeckel 1876

But in many of the fishes and amphibia, which are viviparous, there is a direct conveyance of the male sperm into the female body; and this is the case with all the Amniotes (reptiles, birds, and mammals).

The Evolution of Man — Volume 2 Ernst Heinrich Philipp August Haeckel 1876

All the Amniotes known to us -- all reptiles, birds, and mammals

The Evolution of Man — Volume 2 Ernst Heinrich Philipp August Haeckel 1876

But in the Amniotes there is a considerable curve in the brain along with the bending of the head and neck; the whole of the upper dorsal surface of the brain develops much more than the under ventral surface.

The Evolution of Man — Volume 2 Ernst Heinrich Philipp August Haeckel 1876