Here's a great work that describes the first chordate found in the Burgess Shale. It describes the decades of study by three very dedicates scientists on the Burgess Shale fossils
• 542,000,000 B.C. - • 488,300,000 B.C. - The Cambrian Era
The Cambrian Explosion
“Refers to the geologically sudden appearance of many new animal body plans about 530 million years ago. At this time, at least nineteen, and perhaps as many as thirty-five phyla of forty total, made their first appearance on earth within a narrow five- to ten-million-year window of geologic time. The Cambrian explosion thus marked a major episode of morphogenesis in which many new and disparate organismal forms arose in a geologically brief period of time.” - Stephen C. Meyer
Here's a great work that describes the first chordate found in the Burgess Shale. It describes the decades of study by three very dedicates scientists on the Burgess Shale fossils