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Palaeocene
animals
The Palaeocene comes after the K-T extinction that
killed off the dinosaurs (except for the birds) and
the flying reptiles. It lasted from 65 to 56 million years
ago. So it With the sudden demise of
these kingpin creatures, vast niches became vacant, and waiting to be exploited
by whoever could expand into them fast enough.
The winners were the mammals and the birds. The mammals had the land (although the birds
didn’t give it up without a fight as we’ll see).
The mammals that came through the extinction seem to
have been small rat-sized animals. They
were a primitive form of ungulate. We know ungulates as hoofed animals such as
horses, cows and such. But these early
ungulates had claws. They rapidly
expanded into every one of the niches left vacant by the departing dinosaurs. They were tree 
climbers
and all sorts. This picture of a
‘chriacus’ comes from “Illustrated encyclopaedia of dinosaurs and prehistoric
animals” (1988) edited by B. Cox. A
happy little chap isn’t he? His total
length including his tail was about a metre.
Most of the evidence for the ubiquity of these early
ungulates (or condylarths) comes from
Palaeocene mammals were pretty primitive compared with
their modern descendents. And it took a
drastic weeding-out at the end of the period to prepare the way for kind of
mammals that we are used to.
The birds had the air.
We’ve discussed elsewhere that birds are
flying dinosaurs anyway (or ‘descended from’ … if you prefer). I’ve read that the dino-era birds were pretty
poor flyers, and spent much time on the ground.
The air was the property of the flying
reptiles. So the niches available to
these early birds didn’t involve serious flying. Perhaps they were similar to that of the
modern owl – though probably including reaching fruits and seeds inaccessible
to land dwellers. Even after the Event, the
birds didn’t give up the land without a fight.
During the Palaeocene, there were huge flightless birds around. And of course we still have smaller
flightless birds around now, in certain places.
But the birds were the only animals able to expand into
the completely vacant aerial niche. And
many of them did so with a vengeance.
However the early ones weren’t at all like modern birds, or so I’ve read
though I’m not sure that everybody agrees.
The owl
Apparently the owl was the first recognisably modern
bird to appear, towards the end of the period.
Now the following turns into a bit of a cautionary
tale, so be warned.
To a one-time aerodynamicist like me, this wasn’t at
all surprising. An owl’s face looks as
though it was designed for ‘maximum drag’.
It wasn’t of course. But most
other birds show every sign of having been honed in a wind tunnel (which in a
sense they have) to enable them to cleave through the air with minimum
effort.
This may suggest that the owl took a different path
very early on. It found a niche that
didn’t need good aerodynamics. It’s
patch was local. Dusk was a good time to
hunt. Silent flying was what most owls
down the ages have needed, not speed or endurance. They also needed good eyesight and good
hearing. Part of the owl’s
non-aerodynamic appearance probably concerns adaptations to improve its
binocular vision and its hearing.
A nice simple theory wouldn’t you say? Suitable for the physics envious. (You don’t believe that anybody is silly
enough to be envious of physics? Click
on the link and be wised up.)
Unfortunately there are two snags.
First the experts tell me that long-eared and short-eared owls migrate
many hundreds of miles every winter.
They don’t migrate thousands of miles though, as the really good flyers
do. The second snag is that another
expert tells me that an owl’s skull is very similar to a hawk’s. The rest is just feathers. I would like to think that my theory has some
truth in it though. As I keep saying,
don’t expect things to be simple in this game.
Crocodiles
We shouldn’t ignore the ‘crocodilians’, those distant
descendants of the weird animals of the
Triassic period. A few of these came
through too.
For a comprehensive study of animals around the time
of the Palaeocene, visit Martin Jehle’s “Palaeocene mammals of the world” at www.paleocene-mammals.de
© C B Pease, Oct 07