A spectacular new fossil of a tiny ancient horse
helped to shed new light on the evolution of equines.
It was discovered that a developing foal inside
the pregnant mare had been been preserved in remarkable detail. The
fossil was found at the Messel open-pit mine in Germany, where more
than seventy specimens of ancient horses had been unearthed by
Dr Stephan Schaal of the Senckenberg Research
Institute, Germany, said that the find of the adult horse included
the best preserved foetus ever discovered in Messel. Compared to
other Messel horses, it had impressive preservation of the complete
jaws with its teeth.
These forest-dwelling horses came from the Eocene
Optimum, 49 million years ago, a period in which tropical forests
stretched right to the poles, little or no ice was present on the
planet, and temperatures at the poles varied less from the equatorial
norm than they do today.
The largest of these early horse-like mammals were
about the size of a pig, and giant stalking birds, Gastornis,
took the role of top predators. Gastornis was a giant of its
time, one of the largest animals of the Eocene at two metres tall.
It is thought to have been a predator because its huge beak would
have been far too powerful for simply crushing nuts and other
vegetation, and it also had impressive talons on its toes.
Two species of the tiny forest-dwelling horses,
Propalaeotherium, are known from fossil evidence at Eocene sites
in Germany. These little forest animals had four small hooves on
their front feet and three on the back. They walked on the pads of
their feet, like cats and dogs.
The smallest of the samples found was the size of
a fox terrier, and the largest about the size of a German shepherd
dog. The stomach contents of most specimens show that they ate foliage,
but one was full of fruit - a grape similar to that used to make
Scientists believed the mammals browsed on whatever
they could, including fallen fruit when it was available. This fossil
also helped to shed light on how these ancient horses raised their
young. All of the ten fossils of pregnant mares found at Messel were
carrying one foal.
Running with the herd
This was evidence, according to palaeontologist Dr
Jens Franzen, that even primitive horses had an evolutionary strategy
of raising one or two offspring. That would point to some kind of
special care of the offspring and would indicate that there was a
herd involved in joint care.
The horses had just begun to diverge away from the
group of odd-toed mammals, or perissodactyls, that were the common
ancestors of living horses, rhinos, and tapirs. They had five toes
which, over the course of evolution, fused into the one hoof found
in modern-day horses.