a long boring read, lots of techno words needs work on footnotes and references
Transitions of Reptiles to Mammals
A long long time ago, in a galaxy not too far away, was a little blue planet called
Earth, and on this world not a single mammal lived. However a lot of time has past since
then and we now have lots of furry creatures that are collectively called mammals. How
did they get their? Where did they come from? These are the kinds of questions that led
me to my subject of choice. I will endeavor to provide examples, using specific
transitional fossils, to show that mammals have evolved from a group of reptiles and were
simply not placed here by unknown forces.
Before I begin, I would like to define some terms so that nobody gets left in the
dust. The term transitional fossil can be used in conjunction with the term general
lineage, together they help explain the how one species became another.
This is a sequence of similar genera or families, linking an older to a very different younger
group. Each step in the sequence consists of some fossils that represent certain genus or
family, and the whole sequence often covers a span of tens of millions of years. A lineage
like this shows obvious intermediates for every major structural change, and the fossils
occur roughly (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 ?...