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Cainotheriidae

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Cainotheriidae is a family of extinct animals called artiodactyls. These animals lived in Europe for a very long time. Their history spans from the Late Eocene to the Middle Miocene. Most of their fossils are found in karstic deposits. These are special types of rock formations. Scientists study these fossils to understand how ancient mammals changed. Cainotheriids are important because they show unique anatomical features. They help us see how different animal groups are related.

The bodies of cainotheriids had several very specific features. Their teeth were highly selenodont. This means their premolars and molars had curved, crescent-shaped cutting edges. This type of tooth is similar to what modern ruminants use. Their skulls were small with short snouts. The orbits, or eye sockets, were located in the center of the skull. The orbits were also closed at the back. One very peculiar feature was the auditory bulla. These are the bony structures that protect the ears. In cainotheriids, these ear bones were very large. This trait is often seen in small mammals living in dry, open environments.

While their heads were advanced, their skeletons were quite primitive. Cainotheriids still had four non-reduced toes on their feet. This was an ancestral condition for all artiodactyls. Their lateral fingers were shorter than the others. These toes ended in long claws, similar to modern rabbits. Their hind legs were much longer than their front legs. This physical difference suggests they were adapted for running and jumping. This combination of primitive and advanced traits makes them very interesting to researchers.

The family of cainotheriids can be divided into different groups. During the Upper Eocene, the subfamily Oxacroninae first developed. This group included the genera Oxacron and Paroxacron. These are considered the first true cainotheriids. Later, during the Oligocene, a different group called Cainotheriinae underwent an evolutionary radiation. This radiation produced rabbit-sized genera like Plesiomeryx and Caenomeryx. The most specialized genus in the family was Cainotherium. This genus was the last to disappear from the fossil record.

Researchers have spent many years classifying these animals. For a long time, scientists placed them near a group called Tylopoda. However, more recent research has changed this view. Most current studies place them closer to Ruminantia. This is the group that includes modern deer and cattle. The classification of related animals has also changed. For example, Robiacina was once part of this family. It lived during the middle and upper Eocene. Now, it is considered a separate family and a sister taxon to Cainotheriidae.

Many different species of cainotheriids lived across Europe. Some notable species include C. laticurvatum and C. miocenicum. There was also a species known as C. bavaricum. These animals remained quite common even at the start of the Miocene. The genus Cainotherium was the last of the group to die out. They disappeared during the Middle Miocene. Their extinction happened because the climate became colder. This change in temperature likely made their environment difficult to survive in.

For many years, scholars believed cainotheriids lived like rabbits. They looked at the small size and long hind legs. They thought the animals survived by leaping through their environment. However, new evidence has changed this idea. Fossil traces were discovered at a location called Salinas de Anana in Spain. These fossils belong to the genus Cainotherium from the lower Miocene. The traces show that their movement was actually quite different from rabbits. Instead, they moved in a way that was very similar to modern small ruminants.

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