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But in the Amniotes these primitive kidneys cease to act at an early stage of embryonic life, and their function is taken up by the permanent or secondary kidneys, which develop from the terminal section of the prorenal ducts. The sole surviving proreptile.
It is impossible to entertain the idea that all the living and extinct Mammals come from a number of separate roots. As we have already seen, this root-form developed from the primitive Proreptile stem in a totally different direction from the birds, and soon separated from the main stem of the reptiles.
Homoeosaurus pulchellus, a Jurassic proreptile from Kehlheim. 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.
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