Just in time for National Fossil Day, researchers discovered the earliest-known lamprey larvae dating back at least 125 million years.
The findings mark the "oldest identified fossils displaying the creatures in the early stages of metamorphosis and premetamorphosis," the University of Kansas reported.
The larvae's developmental stage looks almost identical to modern specimens, which is interesting to scientists.
"Among animals with backbones, everything, including us, evolved from jawless fishes," said Desui Miao, University of Kansas Biodiversity Institute collection manager. "To understand the whole arc of vertebrate evolution, we need to know these animals. The biology of the lamprey holds a molecular clock to date when many evolutionary events occurred."
Features of the human body are believed to have come from similar jawless fish, which often has parasitic traits and has been on Earth for about 400 million years. Lampreys have seven pairs of gill arches, which may have evolved into human jaws and ear bones. Lampreys are believed to have played a huge role in the development of vertebrates, but the larva themselves are soft and fleshy.
"They just don't have hard parts," Miao said. "Even fully developed fossil lampreys are rare because they lack skeletons. Most fossil fishes are bony fishes -- fish we eat and leave bones on the plate. But lampreys don't have bones or teeth that can be preserved as fossils."
Despite their difficult-to-preserve bodies, these creatures were plentiful in the freshwater lakes of ancient Inner Mongolia, and many have been pristinely preserved in the region's late-Cretaceous shale.
"This type of rock preserves very fine details of fossils," Miao said. "The same rock preserved evidence of dinosaur feathers from this era. The lamprey larvae were found by local people and some by our Chinese colleagues who specialize in early fishes."
The findings were published Oct. 14 in the journal Proceedings of the National Academy of Sciences.
