But outside of rare events where entire animal families are fossilized together ... the likely litter size of different mammalian ancestors: What were the odds of a singleton birth for each ...

All modern dogs are descendants of wolves, though this domestication may have happened twice, producing groups of dogs descended from two unique common ancestors. How and when this domestication ...

Even when there are fewer than five digits in the adult animal -- as in horses' hooves ... All tetrapods descended from a common ancestor that just happened to have limbs with five digits.

That individual animal lived not so long before ... which were very common in the Hell Creek fauna. The first alligator ancestors evolved some 245 million years ago. About 80 million years ago ...