A team of scientists in Germany have unearthed the remains of an ancient ancestor of the horse with its unborn foal still inside its womb.
The well-preserved fossil belonged to a Eurohippus messelensism, a horse-like mammal that lived around 48 million years ago. It was found at an old shale quarry known as the Messel Pit located near the city of Darmstadt.
Scientists from the Senckenberg Research Institute in Frankfurt, led by Dr. Jens Franzen, examined the prehistoric specimen and discovered that animal had already been in the advanced stages of its pregnancy when it died. However, the fetus as well as some of the tissues from the animal's placenta and uterus remained in good condition.
Despite the fetus' skull having been crushed, the researchers were able to reconstruct its original position using most of its bones present at the site.
The team believes that the ancient mare died moments before it was about to give birth but said the cause of its death was not related to the birth. It was more likely that the animal met its end after drinking contaminated water from a prehistoric lake.
Franzen and his colleagues made use of high resolution X-rays and electron miscropy scanning in order to examine the fossil of the Eurohippus messelensism.
They noted how the placenta and uterus of the ancient animal closely resembled those of present-day mares, which suggests that pregnancies among mammals changed little over the past millions of years.
Franzen said that the Eurohippus messelensis specimen is the oldest and best preserved primitive equoid fetus they have found.
Franzen added that the postcranial skeleton of the ancient mare was virtually complete and well-articulated, allowing the researchers to reconstruct the fetus' original position. This showed that the unborn foal was normal and corresponded to the late stages of gestation of present-day horses.
The Eurohippus messelensism fossil was discovered by Senckenberg researchers 15 years ago, but it was only recently studied fully through the use of micro X-ray.
The findings suggest that despite the significant differences in the shape and size of prehistoric mares from their modern counterparts, both species have relatively similar reproduction.
The Senckenberg Research Institute study is featured in the journal Public Library of Science One.
Photo: Senckenberg Research Institute
