MUNICH, Germany, April 30 (UPI) -- There are 1,270 different species of killifish. The colorful, compact swimmers are everywhere -- everywhere except in fossil form, until now.
Researchers at Ludwig Maximilian University of Munich recently identified several dozen killifish fossils among the Tugen Hills, an ancient lake bed which lies along the eastern arm of the East African Rift Valley.
The specimens, embedded in the rock deposits there, are dated at six million years old, most measuring no more than a couple inches in length. They are remarkably well preserved.
"The sample comprises a total of 169 individuals, and 77 of these are complete," Melanie Altner, LMU paleontologist, said in a press release.
In terms of evolution, killifish have been rather prolific. Their speciation is impressive. But understanding their knack for differentiation and evolutionary survival is difficult when an entire lineage is missing from the fossil record.
Researchers hope this new discovery changes that reality, and sparks new research. The fossils have already helped paleontologists piece together disparate portions of the killifish family tree.
"Our fossils exhibit morphological traits that are found in extant African species of killifish," explained Altner. "But they also possess one specific trait that is typical for contemporary rivulids from South America."
"This combination is very unusual, and may indicate that Kenyaichthys is closely related to forms that are now restricted to South America," she added. "Alternatively, this particular character may have been lost in the lineage that gave rise to modern African aprocheiloids."
The research was published in the journal PLOS ONE.