A fossil find: early land amphibians.

A fossil find: Early land amphibians 

The brave fish that hauled themselves out of their aquatic homes and onto the new world of land at the end of the Devonian period, some 360 million years ago, radically changed the course of evolution. Unfortunately, the fossil history of their early descendants is fragmented and sparse. The earliest known records of amphibians, the first land vertebrates, date to 360 million years ago, but it is not until the Upper Carboniferous, 50 million years later, that the fossil record becomes plentiful. By then, many important changes in both amphibians and arthropods (invertebrates including insects and crustaceans) had already taken place.

Now paleontologists have a new assemblage of terrestrial animal fossils that will help fill in the gap. Stanley Wood, of Mr. Wood's Fossils in West Lothian, Scotland, and co-workers at The University at Newcastle upon Tyne discovered amphibian, arthropod and plant fossils in the Lower Carboniferous (320 to 360 million years ago) layers of the East Kirkton Limestone in Scotland. The most important find is a 40-centimeter-long, well-preserved, complete amphibian skeleton, the oldest ever discovered. "The specimen is remarkable for the intact preservation of the hands and feet, with ossified carpals and tarsals [wrist and foot bones], and should greatly augment our understanding of the early evolution of the tetrapod [four-footed] limbs,' the researchers write in the March 28 NATURE. Also found was the earliest known fossil harvestman, or daddy longlegs.

The researchers write that the absence of fish fossils suggests that amphibians had become an integral part of terrestial life by that time--and also indicates that Wood's group has found the earliest record of completely land-based vertebrates.