Morphology
The animals of this genus were small in size, they did not exceed 20 cm in height and in terms of length, they measured about 60 cm. They weighed approximately 6 kg. Although it is considered the first ancestor of current horses, it did not have much resemblance to them.
For example, the shape of its head was very different and its muzzle was not that long and extended forward. Likewise, her eyes were not on either side of the head, but had a central position, projected forward.
Bony structure of a Hyracotherium. Source: RobTwoEagle
In regards to the limbs, those of the genus Hyracotherium were quadrupeds. On the front legs they had four toes, each with a hoof, while on the hind legs they had three toes, each with a hoof the same. The middle finger was much longer and wider than the others.
His teeth were adapted to his diet. Her teeth were low-crowned and it is believed that she had a little over 40 teeth in all.
Species
So far and thanks to the fossils that have been collected, only a single species belonging to this genus has been established: Hyracotherium leporinum.
There were other species that at the time were classified within this genus. However, thanks to research and the work of different specialists, these species were relocated to other genera, such as Arenahippus, Sifrihippus and Protorohippus, among others.
Reproduction
Actually, little information is available about this genus in relation to its habits and reproduction.
In this sense, taking into account the similarity that exists between the current horse and its ancestors, among which this genus is counted, it is possible to establish roughly what the reproduction process of these was like.
The first thing that can be established is that these animals reproduced sexually. This implies that there was an exchange of genetic material and the fusion of two sex cells, an egg and a sperm to generate a new individual.
Fertilization
In this type of animals, which belong to the Mammalia class, fertilization is internal. Generally, the male has a copulatory organ through which he deposits sperm inside the female's body. This process had to occur at the moment the female ovulated, that is, the moment her ovaries released an egg.
Now, with regard to the female, it is possible that the moment she was ready for fertilization, she displayed some kind of behavior in which she let the male know that she was ready to mate.
As with a large number of mammals, especially those that are larger, each time this animal ovulated, it was possible that it released a single egg.
Pregnancy and birth
After the egg and sperm joined, a single cell was formed called a zygote. This underwent a series of divisions and transformations until giving rise to a complete individual.
These animals belonged to the placental infraclass, the new being was formed within the body of the female. A connection was established between the mother and the baby through a structure known as the placenta.
Through this, the nutrients reached the fetus, coming directly from the mother's bloodstream. Animals that develop in this way are known as viviparous.
Once the reasonable time had elapsed and the fetus reached its maximum development, delivery occurred. During this process, the formed animal was expelled from the mother's body through the vaginal canal.
The foal (small horse) that was born in this way, had characteristics similar to those of an adult horse, with the exception that it was small, so it still remained for a time under the care of the mother until it was able to fend for yourself.
Nutrition
The animals that belonged to this genus, had a type of diet very similar to that of current horses. They were herbivores, so they fed solely and exclusively on plants. But not just any type of plants, but, thanks to the characteristics of their teeth, they fed on the leaves of shrubs and small trees, mainly the greenest and most appetizing.
Within the group of herbivores there are several types of animals. Members of the genus Hyracotherium belonged to the so-called browsers, because they fed only on leaves.
Digestion
Once the food entered the animal's oral cavity, it mixed with the saliva and began to transform, as a result of the action of the various digestive enzymes that were present in it.
Subsequently, the food, already converted into a food bolus, passed into the esophagus to be taken to the stomach where it was subjected to the action of gastric juices.
Subsequently, at the level of the intestine, the absorption of nutrients and water occurred. However, as with many herbivores today, it is possible that your body was not equipped to digest certain components of the plants you ingested.
Because of this, it is likely that there were bacteria in your intestine to help you with this process.
Finally, the food particles that were not digested were released through the anus as feces.
References
- Arita, H. (2010). The return of the horse: the macro and the micro in evolution. Sciences 97.
- Evolution of the horse. Taken from: britannica.com
- Hooker, JJ (1994). "The beginning of the equoid radiation." Zoological Journal of the Linnean Society 112 (1–2): 29-63
- MacFaden, B. (2005). Fossil horses - evidence for evolution. 307.
- Valentine, R. (1975). The evolution of the horse. Journal of reproduction and fertility supplement. 23 (23).