December 12, 2013
Scientists Discover 4M-Year-Old Horse Fossil In Ethiopia
Lee Rannals for redOrbit.com - Your Universe Online
Scientists have discovered a new species of a small horse that lived 4.4 million years ago in Ethiopia.
The Eurygnathohippus woldegabrieli fossils were found in the Gona area of the Afar region in 2001. The ancient horse was among a diverse array of animals that lived in the same areas as the ancient human ancestor Ardipithecus ramidus, or Ardi.
The ancient horse species was about the size of a small zebra and had three-toed hooves. Scientists say the E. woldegabrieli grazed the grasslands and shrubby woods.
Scott Simpson, professor of anatomy at Case Western Reserve's School of Medicine, said the horse fills in a gap in the evolution of horses. He added this is an important discovery for documenting how old a fossil locality is and in reconstructing habitats of human forebears of the time.
"This horse is one piece of a very complex puzzle that has many, many pieces,” Simpson, who is co-author of the study published in the Journal of Vertebrate Paleontology, said in a statement. "The fossil search team spreads out to survey for fossils in the now arid badlands of the Ethiopian desert. Among the many fossils we found are the two ends of the foreleg bone—the canon—brilliant white and well preserved in the red-tinted earth."
The researchers also found part of the connecting shaft, which was split lengthwise but provided the crucial full length of the bone. The bone indicates this species was an adept runner, similar to modern zebras. Researchers also performed analysis of the teeth, revealing the species relied heavily on eating grasses.
The horse had longer legs than other ancestral horses that lived and fed in forests about six million to 10 million years ago. This evolutionary change helped the horse cover longer distances and flee from predators like sabre-tooth cats and hyenas.
The teeth are taller than their descendants and have crowns that are worn flatter, which is a sign the horses adapted to a grazing lifestyle. An analysis of the isotopic composition of the enamel confirmed the horse subsisted on grass.
"Grasses are like sandpaper," Simpson said. "They wear the teeth down and leave a characteristic signature of pits and scratches on the teeth so we can reliably reconstruct their ancient diets."
The remains showed this horse was a significantly different animal than the horses from earlier than five million years ago, as well as those from later than 3.5 million years ago. The researchers said members of the youngest group are taller and have longer noses, which are even more beneficial characteristics for open grassland living.