October 13, 2006
Director of Media Relations
AMHERST, Mass.—The notion that an animal would need a hard skeleton to leave behind a fossil imprint is something of a fossil itself, according to Whitey Hagadorn, an assistant professor of geology at Amherst College. Hagadorn is the lead author of a paper titled “Cellular and Subcellular Structure of Neoproterozoic Animal Embryos” in the latest issue of Science magazine (Vol. 314, no. 5796). Hagadorn and a team of researchers from the U.S., U.K., China, Sweden, Switzerland and Australia, among them Matthew McFeely, a 2005 graduate of Amherst College, demonstrate that “the earliest animal fossils are nothing more than ancestral sponge-like animals,” Hagadorn says.
Hagadorn, McFeeley and their colleagues also document the first fossil example of cells about to undergo division. Fossilized embryos predating the “Cambrian Explosion” by 10 million years provide evidence that early animals had already begun to adopt some of the structures and processes seen in today’s embryos. The article reports the first direct evidence that primitive animals 550 million years ago were capable of asynchronous cell division during embryonic development.
The researchers also believe they’ve identified specialized structures inside the cells, such as bubble-like vesicles that the cells might have used to transport, store or metabolize molecules. Slight aberrations during the fossilization of dead embryonic cells even reveal what appear to be dividing nuclei. It was assumed such structures existed in early animals, but until now, no known fossils of the structures existed.
The research uncovered 162 fossils of animal embryos from the Doushantuo Formation of south central China, still encased in a fertilization envelope, a protective husk that likely aided the preservation of the embryos long enough for fossilization to occur.
Hagadorn’s and McFeeley’s co-authors are Stefan Bengtson (Swedish Museum of Natural History), Philip Donoghue, Neil Gostling and Maria Pawlowska (University of Bristol, England), Kenneth Nealson (University of Southern California), Marco Stampanoni (Paul Scherrer Institut, Switzerland), F. Rudolf Turner and Rudolf Raff (Indiana University Bloomington) and Shuhai Xiao (Virginia Tech).
The project was funded by the National Science Foundation, the National Geographic Society, NASA, the National Natural Science Foundation (China), the Natural Environment Research Council (U.K.), the National Endowment for Science, Technology and the Arts (U.K.), the Mellon Foundation, the Trustees of Amherst College, the Swedish Research Council and the Chinese Academy of Geological Sciences.
A member of the Amherst faculty since 2002, Hagadorn studies the earliest known marine animal communities—“paleocommunities” exposed in the sedimentary rocks in mountain ranges created about 500-550 million years ago in the southwestern U.S. and northwestern Mexico. Sedimentary structures and fossils provide clues about the nature of ancient seafloor environments, as well as the animals that lived there. Hagadorn was educated at the University of Pennsylvania (B.A. degree) and the University of Southern California (M.S. and Ph.D. degrees.