Fossil May Lie Near Root of Fish, Land Animal Lineages
 

A newly discovered fish species that lived more than 400 million years ago may represent a bridge between modern fish and land animals, scientists say.

Found in Yunnan, China, the creature combines features of ray-finned bony fishes, which include the majority of modern fish species, and lobe-finned bony fishes, the group that spawned the ancestors of today’s land vertebrates, the researchers reported.

Thus, the creature would be closely related to the common ancestor of the two vertebrate lineages that went on to dominate the modern world.

Vertebrates are animals with a bony or cartilaginous skeleton and a segmented spinal column.

The ancient fish, represented by chunks from four separate skulls, has a skull roof much like that of actinopterygians, the group that includes most modern fish, the researchers explained.

But the fine features of its anatomy may also shed light on the evolutionary origin of a substance called cosmine, they added.

Cosmine is a hard surface-tissue found in many fossil sarcopterygians, the fish that later gave rise to land vertebrates. Sarcopterygians are believed to include Tiktaalik, a 375-million-year-old species reported last month as a possible “missing link” that could represent the first fish capable of walking on land.

Cosmine has a network of pores and canals under an enamel-based layer, said the scientists who reported the new find. The researchers, Min Zhu of the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing and colleagues, described the unusual fish in this week’s issue of the research journal Nature.


Researchers placed Meemannia near the root of the family tree that comprises modern fish and land animals.

The 405-million-year-old fossil possessed several such layers over the pore-canal network, suggesting that the cosmine arose after all but one of these layers disappeared, they added. They dubbed the fish Meemannia eos, after the prominent paleontologist Meemann Chang and the Greek eos, meaning dawn.