Tiny Ontario fossil fish takes a big evolutionary bite
Fossil donated to ROM for Research and Display
425-million-year-old discovery-- most complete early ‘spiny shark’ known in the World
A new discovery contributing to our understanding of the early evolution of jaw-bearing vertebrates has been made, after the most complete, early acanthodian (or ‘spiny shark’) anywhere in the world was found in the Silurian Bertie Formation Konservat-Lagerstätte in Ontario. The findings, co-authored by the ROM’s David Rudkin, Assistant Curator of Invertebrate Palaeontology, will be published in the August 5, 2014 edition of the journal PLOS ONE.
The fish, assigned to the species Nerepisacanthus denisoni, is approximately 425 million years old. Its fossil remains consist of tiny mineralized body scales, larger fin spines, and tooth-bearing jaw bones, arrayed along a slender body. Like other acanthodians, the internal skeleton was not bony and would have consisted instead of cartilage, like sharks and their relatives. This feature, along with a generally streamlined body shape and the rigid fin-supporting spines, has given rise to their colloquial group name – ‘spiny sharks’. This new fossil, consisting of part and counterpart on opposing faces of a rock split, measures just 112 millimetres in length, from the front of the jaws almost to the end of the tail fin and likely represents an immature fish.
This recent discovery is the first known intact vertebrate fossil from this formation and geographical location. “Until now, most of what we knew about acanthodians was based on relatively rare, but far more complete, fossils from geologically younger freshwater deposits of Devonian and Carboniferous age,” says David Rudkin. “This unique new specimen, generously donated to the Royal Ontario Museum by its discoverer, represents the only near-complete acanthodian from pre-Devonian rocks anywhere in the world, and provides the oldest clear ‘road map’ of how all the dispersed elements of these very early jawed fishes fit together into a compact swimming predator.”
Journal Article: http://dx.plos.org/10.1371/journal.pone.0104171
Digital Resources
A ROMblog, further describing the significance of this discovery can be found at www.rom.on.ca/en/blog/a-silurian-shark-tale. YouTube videos are available for media to embed in their digital content.