Chinese researchers say a newly discovered fish species that lived more than 400 million years ago may represent a bridge between two vertebrate lineages.
The creature -- found in Yunnan, China -- combines features shown by ray-finned bony fishes, which include the majority of modern fish species, and by lobe-finned bony fishes, the group that spawned the ancestors of today's land vertebrates.
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. But the fine features of its anatomy may also shed light on the evolutionary origin of cosmine -- a hard surface-tissue found in many fossil sarcopterygians, the fish that later gave rise to land vertebrates.
Cosmine is characterized by a network of pores and canals in the tissue, overlaid by a single enamel-based layer, reported Min Zhu and colleagues at the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing.
They detail the unusual fish in this week's issue of Nature.
Copyright 2006 by United Press International
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