Two teams of researchers, including a scientist from Case Western Reserve University, have announced the discovery of a new species of fossil horse from 4.4 million-year-old fossil-rich deposits in Ethiopia.
Filling a gap in horse history
The fossil horse fills a gap in the evolutionary history of horses but is also important for documenting how old a fossil locality is and in reconstructing habitats of human forebears.
About the size of a small zebra, Eurygnathohippus woldegabrieli -- named for geologist Giday WoldeGabriel, who earned his PhD at Case Western Reserve in 1987 -- had three-toed hooves and grazed the grasslands and shrubby woods in the Afar Region, the scientists say in reporting their findings in the November issue of Journal of Vertebrate Paleontology.
The horse fills a gap in the evolutionary history of horses but is also important for documenting how old a fossil locality is and in reconstructing habitats of human forebears of the time, said Scott Simpson, professor of anatomy at Case Western Reserve's School of Medicine, and coauthor of the research. "This horse is one piece of a very complex puzzle that has many, many pieces."
The horse had longer legs than ancestral horses that lived and fed in forests about 6 million to 10 million years ago, Simpson said. The change helped the more recent horses cover long distances as they grazed and flee lions, sabre-tooth cats and hunting hyenas that would run down their prey.
The other fossils they found included teeth, which are taller than their ancestors' and with crowns worn flatter -- more signs the horses had adapted to a grazing life. Analyses of the isotopic composition of the enamel confirmed that E. woldegabrieli 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."
Horse expert Raymond L. Bernor, from the Laboratory of Evolutionary Biology at the Howard University College of Medicine in Washington D.C., led the fossil analysis.
The bones, which remain at the National Museum of Ethiopia in Addis Ababa, Ethiopia, showed this was a significantly different animal than the horses more than 5 million years old, and those 3.5 million years old and younger. Members of the youngest group are taller and have longer noses, further adaptations to the open grasslands, the researchers say.
The team continues to analyze fossil remains they collected at this and nearby sites.
Story is based on materials provided by Case Western Reserve University