If you are going to count what isn't there so am I- and I'll say there are millions of transition species we have not found.
It is amazing we have as many fossils as we do (imo). I'm not sure what you know about fossilization, but it is a relatively rare event:
colostate.edu
If a transition species lasted for only a short time, it would stirke me as very odd that we did find it. On the other hand, many transition species have been found (species that managed to hang around for a while)- you may simply be unaware of their existence:
talkorigins.org
A nice example of transitions:
Condylarths, the first hoofed animals
Protungulatum (latest Cretaceous) -- Transitional between earliest placental mammals and the condylarths (primitive, small hoofed animals). These early, simple insectivore- like small mammals had one new development: their cheek teeth had grinding surfaces instead of simple, pointed cusps. They were the first mammal herbivores. All their other features are generalized and primitive -- simple plantigrade five-toed clawed feet, all teeth present (3:1:4:3) with no gaps, all limb bones present and unfused, pointy-faced, narrow small brain, eyesocket not closed.
Within a few million years the condylarths split into several slightly different lineages with slightly different teeth, such as oxyclaenids (the most primitive), triisodontines, and phenacodonts (described in other sections). Those first differences amplified over time as the lineages drifted further and further apart, resulting ultimately in such different animals as whales, anteaters, and horses. It's interesting to see how similar the early condylarth lineages were to each other, in contrast to how different their descendants eventually, slowly, became. Paleontologists believe this is a classic example of how 'higher taxa" such as families and orders arise.
On the presence of transitional fossils also see:
tim-thompson.com |
