Transitions Of Reptiles To Mammals

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(but often not
exactly) in the expected order. However, usually there are still gaps between
each of the groups. Sometimes the individual specimens are not thought to be
directly ancestral to the next-youngest fossils (e.g. they may be "cousins"" or
"uncles" rather than "parents"). However they are assumed to be closely related
to the actual ancestor, since the have similar intermediate characteristics.

Where Does It All Begin ?

Mammals were derived during the Triassic Period ((from 245 to 208
million years ago) It began with relatively warm and wet conditions, but as it
progressed conditions became increasingly hot and dry.) from members of the
reptilian order Therapsida. The therapsids, members of the subclass Synapsida
(sometimes called the mammal-like reptiles),generally were unimpressive in
relation to other reptiles of their time. Synapsids were present in the
Carboniferous Period (about 280 to 345 million years ago) and are one of the
earliest known reptilian groups. ...

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from a species belonging to different, older taxon. There is
nothing magical about this. The first members of the new group are not bizzare,
they are simply a new, slightly different species, barely different from the
parent species. Eventually they give rise to a more different species, which in
turn gives rise to a still more different species, and so on, until the
descendents are radically different from the original parent. For example, the
Order Perissodactyla (horses) and the Order Cetacea (whales) can both be traced
back to early Eocene animals that looked only marginally different from each
other, and didn't look at all like horses or whales. (They looked more like
small, dumb ...

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