Exquisite ancient horse fossil preserves uterus with unborn foal

November 6, 2014

A specimen of the ancient horse Eurohippus messelensis has been discovered in Germany that preserves a fetus as well as parts of the uterus and associated tissues. It demonstrates that reproduction in early horses was very similar to that of modern horses, despite great differences in size and structure. Eurohippus messelensis had four toes on each forefoot and three toes on each the hind foot, and it was about the size of a modern fox terrier. The new find was unveiled at the 2014 Annual Meeting of the Society of Vertebrate Paleontology in Berlin.

"Almost all of the bones of the fetus are still articulated in their original position. Only the skull is crushed," said Dr. Jens Lorenz Franzen of the Senckenberg Research Institute, lead author of the study. The study's co-authors are Dr. Jörg Habersetzer, also of the Senckenberg Research Institute, and Dr. Christine Aurich of the University of Veterinary Medicine at Vienna and head of the Graf Lehndorff Institute of Equine Sciences.

The specimen was discovered by a team from the Senckenberg Research Institute nearly 15 years ago, but its extent was not fully appreciated until it was studied using micro x-ray. The micro x-ray analysis revealed a structure known as the broad ligament that connects the uterus to the backbone and helps support the developing foal. Remnants of the wrinkled outer uterine wall became visible after the specimen was prepared, a feature shared between Eurohippus and modern horses. The placenta in this specimen is only the second one that has been described for a fossil placental mammal.

The oil shales at Grube Messel have long been known for their marvelous fossils. These oil shales formed at the bottom of ancient Lake Messel and preserve the remains of mammals, birds, and other animals that were living near what is now Darmstadt, Germany about 47 million years ago (the Eocene epoch). No oxygen was present at the bottom of the lake when the dead animals sank down and finally became embedded in the muddy sediments. There, anaerobic bacteria immediately began to decompose skin, muscles, and other soft tissues. As a result, the bacteria produced carbondioxid, which in turn precipitated iron ions present in the lake water. In this way, the bacteria petrified themselves, developing only a very thin bacterial lawn depicting the soft tissue as black shadow. Consequently, Messel fossils preserve these remains not directly, but as images.

The size of the fetus and the presence of fully developed milk teeth indicate that it was close to term when it and its mother died. Nevertheless, its position in the uterus indicates that the two did not die during the birthing process. The was upside down rather than right side up, and its front legs were not yet extended as they should be just before birth.

Explore further: New record set for wingspan with discovery of bird fossil in Chile

Related Stories

Palaeontologists catch turtles in flagrante

June 19, 2012

German palaeontologists have dug up the remains of nine turtle pairs that died while mating some 47 million years ago, sinking into poisonous waters while locked in a final embrace, a report said Wednesday.

Iron preserves, hides ancient tissues in fossilized remains

November 26, 2013

New research from North Carolina State University shows that iron may play a role in preserving ancient tissues within dinosaur fossils, but also may hide them from detection. The finding could open the door to the recovery ...

Ancient rhino-relatives were water-loving

October 8, 2014

The discovery of new bones from a large land mammal that lived about 48 million years ago has led scientists to identify a new branch of mammals closely related to modern horses, rhinos, and tapirs, according to a study published ...

Recommended for you

Reconstructing the sixth century plague from a victim

August 30, 2016

Before the infamous Black Death, the first great plague epidemic was the Justinian plague, which, over the course of two centuries, wiped out up to an estimated 50 million (15 percent) of the world's population throughout ...

New species of pterosaur discovered in Patagonia

August 30, 2016

Scientists today announced the discovery of a new species of pterosaur from the Patagonia region of South America. The cranial remains were in an excellent state of preservation and belonged to a new species of pterosaur ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.