The Scenario

This scene depicts a muddy estuary that occupied what is now southern Quebec, about 370 million years ago. On the left, a group of Cheirolepis (primitive ray-finned fishes) is being followed by Eusthenopteron, a large lobe-finned relative of the tetrapods seen in the center. In the upper left, an early lungfish called Scaumenacia rises to the surface in order to gulp air. In the lower center, box-like armored placoderms belonging to the genus Bothriolepis cruise slowly over the muddy bottom in order to feed on detritus. One of the last armored jawless fishes, Alaspis (an ostracoderm related to Cephalaspis), is also feeding on bottom detritus, at the lower right. To the far right is the fish Elpistostege, an extinct relative of tetrapods.

The Environment

These fossils are preserved in sandy and silty sediments of the Escuminac Bay Formation, in what is now Quebec, Canada. In these coarse sediments, fossil fishes are frequently accompanied by terrestrial plant fossils, suggesting that storms or strong temporary currents probably were responsible for much of the sediment formation. Many of the fishes are preserved in three dimensions, suggesting that they were overwhelmed and buried quickly. For most of the time, however, conditions in the estuary probably were clear and quiet, with much slower rates of sediment accumulation. Waters in the estuary were probably warm, and supported a rich and taxonomically diverse population of fishes.