University of Missouri

MU Researcher Assembles Benchmark Compilation of Research Highlighting the Dawn of Animal Life

Special issue of the Journal of Paleontology may help with future interpretation of early animal evolutionary history

  • Clockwise from lower left: Cambrian Mastigograptus sp. specimen, Utah, USA (LoDuca and Kramer); three Cambrian small shelly Acidocharacus longiconus specimens, Shaanxi Province, China (Moore et al.); three Cambrian possible animal embryos, Hubei Province, China (Broce et al.); Ediacaran Kimberichnus teruzzii excavation trace with associated Kimberella resting trace and nearby Dickinsonia costata, Ediacara Member, south of Brachina Gorge, Australia (Gehling et al.); reconstruction of Ediacaran deep-water ecosystem represented by fossils of the Mackenzie Mountains, northwestern Canada (Peter Trusler illustration; Narbonne et al.).

  • Deep-water Ediacaran fossils from the Mackenzie Mountains, NW Canada (Narbonne et al.). 1. Hiemalora (left) and Aspidella; 2. Namalia germs, 1968; 3. Primocandelabrum Hofmann, O’Brien and King, 2008 with Aspidella-like holdfasts, several of ;which exhibit stems or fronds (arrows); 4. close-up of Primocandelabrum showing an Aspidella-like disc at its base and candelabra-like branches at the distal end of the preserved frond (arrows). Scale bars represent 1 cm or 1-cm increments.

  • Cambrian embryo fossil exposed by acid etching on rock surface. Polygonal structure on surface indicative of blastula stage of development (Broce et al.).

The Cambrian Period is a time when most phyla of marine invertebrates first appeared in the fossil record. Also dubbed the “Cambrian explosion,” the fossil record from this time provides glimpses into evolutionary biology when the world’s ecosystems rapidly changed and diversified. These glimpses of modern animal biology in the Cambrian are predated only by rather alien forms of the Ediacaran Period, an evolutionarily swift ecological makeover that has perplexed scientists ever since Charles Darwin himself.

“The Ediacaran–Cambrian transition represents one of the intellectually richest periods in our record of the history of life,” says James Schiffbauer, assistant professor of geological sciences in the MU College of Arts and Science. “The Cambrian Period, which occurred between 540 million and 485 million years ago, ushered in the advent of shells and more biologically recognizable organisms as compared to the soft-bodied oddities of the Ediacaran Period. In addition, this transition captures major innovations in ecosystem structure and engineering behaviors, such as are recorded as trace fossils. The growing research on this transition has provided scientists with new clues into how our earliest animal ancestors existed and interacted over half a billion years ago. In co-editing this special issue of the Journal of Paleontology (with Shuhai Xiao, professor of geological sciences at Virginia Tech), we wanted to bring together cutting-edge research on life history and behavioral evolution across the Ediacaran–Cambrian transition from leaders of this scientific field.”

The Ediacaran–Cambrian Transitions issue includes 18 contributions, ranging from Guy Narbonne (Queen’s University) and colleagues’ description of a deep-water Ediacaran ecosystem and Dmitriy Grazhdankin’s (Novosibirsk State University) discussion of patterns Ediacaran evolution, to accounts of complex feeding behaviors in the Ediacaran by James Gehling (South Australia Museum) and colleagues and Francis Macdonald (Harvard University) and colleagues.

This special issue is quite timely. Combined with the preceding January issue and accompanying memoir, which included contributions from Shuhai Xiao and colleagues reporting new silicified and phosphatized microfossils, description of mysterious spiral microfossils from Xi-guang Zhang (Yunnan University) and Brian Pratt (University of Saskatchewan), and reports of Ediacaran sediment feeding behaviors from Mary Droser and colleagues (University of California, Riverside), the first issues of the Journal of Paleontology for 2014 bring an enormous amount of new information to the exciting Ediacaran–Cambrian table.   

In addition to the March issue’s introductory contribution, Schiffbauer and his team published two papers in this volume, one describing the preservation of an enigmatic Ediacaran fossil from Namibia (lead by Mike Meyer, Western Carolina University); and another lead by Schiffbauer’s doctoral student, Jesse Broce, a Huggins Scholar in geology, on early Cambrian fossilized embryos providing rare and unique opportunities to study the origins and developmental biology of early animals during the Cambrian explosion.

To access the March 2014 issue of the Journal of Paleontology, published by the Paleontological Society, please click here.

Jeff Sossamon, MU News Bureau
April 8, 2014