June 21 () –
The distant ancestors of modern horses had hoof-like toes instead of a single hoof, that disappeared over timeconfirms a new study.
Animals, such as the Eocene Hyracotherium, had feet like a modern tapir: four toes in front and three behind.each with individual hooves and an underlying pad.
By contrast, modern equids, such as horses, donkeys, and zebras, have only one toe, the third toe over the original on each foot, enclosed in a thick-walled, keratin-like hoof. with a frog -a part in the inner area of the hoof-triangular underlying the sole that acts as a shock absorber
An international team of scientists, from the UK, the US and the Netherlands, analyzed the hoof prints and foot bones of modern horses and fossil records to find out what happened to the missing toes.
The author, Professor Christine Janis, from the University of Bristol’s School of Earth Sciences, explained it’s a statement: “The upper parts, the remains of the additional hand and foot bones, remain as ‘slat bones’ fused to the remaining central one, but where are the toes of the fore and hind feet?”
“In later fossil horses, there were only three toes on the front and rear. The extra toes, known as lateral toes, on these horses were smaller and shorter than on a tapir, and probably did not touch the ground under normal circumstances. , but they may have provided support in rare situations, such as sliding or forceful impact.”
In the findings, published in Royal Society Open Science, confirms the older notion that these toes really were completely lost to evolution, they were not somehow kept inside the hull, as proposed in another recent article published in the same magazine in 2018.
Lead author Professor Alan Vincelette, from St. John’s Seminary, Camarillo, California, said: “Although remnants of the proximal parts (upper parts) of the lateral toes appear to have been preserved in modern horses, as claimed by the previous article from 2018, the distals (lower portions or toes) they have simply been lost.
The 2018 paper proposed that in modern horses, these lateral toes are retained within the hoof of the middle toe, contributing in part to frogging, although there are no actual bones within the frog.
This was partially based on an interpretation of the hoof prints of an extinct three-toed horse, Hipparion (not in direct line with modern horses) from Laetoli in Tanzania 3.7 million years ago, the same site that produced the famous footprints of the hominid Australopithecus. These hoof prints apparently lacked a frogand this added weight to the idea that the lateral toes of horses like Hipparion now contribute to the nut of modern horses.
While not all hoof prints of modern frogged horses record their presence, an undoubted frog can be seen in many hoof prints known to have been made by three-toed horses. These observations cast doubt on the notion that the modern horse’s hoof frog formed from the lateral toes of tridactyl equids.
Author Professor Christine Janis, from the University of Bristol’s School of Earth Sciences, said: “While the notion that modern horses have retained all their original toes as remnants within the hoof is novel and therefore So attractive enough, it can be shown to be wrong.”
Alan Vincelette added: “The horse’s hoof frog evolved independently of the lateral toes as a unique structure that provides shock absorption and traction during locomotion”.
The team also shows that the feet of one-toed horses have a different shape from the main toe of three-toed horses, being round rather than oval, a difference that may be related to differences in the distribution of the toe. weight and/or habitat.