Fossil ancestor shows sharks have a bony past

Fossil ancestor shows sharks have a bony past
Professor John Long with the Gogo shark (Gogoselachus) fossil in 2005

Most people know that sharks have a distinctive, all-cartilage skeleton, but now a fossil from Western Australia has revealed a surprise 'missing link' to an earlier, more bony form of the fish.

Published today in the scientific journal PLOS One, research by Flinders University palaeontologist Professor John Long substantially strengthens the theory that the modern shark is less primitive than previously believed.

In testing fossil remains discovered by Professor Long in July 2005 at Gogo in the Kimberley in Western Australia, detailed CT scanning analysis has shown that the three-dimensional remnant skeleton contains a small proportion of as well as cartilage.

Professor Long said the fossil, which dates from the Devonian Period (380 million years old), reveals an ancient shark caught in evolutionary transition.

Because and rays have entirely cartilaginous skeletons, Professor Long said it was traditionally thought that they were part of a primitive evolutionary pathway, and that bone in other fish was the more advanced condition.

But a series of discoveries in recent years has suggested that sharks are "more evolutionarily derived", and are likely to be descended from bony ancestors.

Fossil ancestor shows sharks have a bony past
Preparation of Gogoselachus lynbeazleyae WAM 09.6.145, Gogo Formation, Western Australia. (A) Meckel's cartilage as exposed on collection, before acetic acid etching. (B) specimen during early acid preparation. (C) Meckel's cartilages WAM 09.6.145–001 (left), WAM 09.6.145–002 (right) after full preparation, shown articulated in dorsal view. Credit: doi:10.1371/journal.pone.0126066.g001

"Our shark more or less nails that theory, because here we have a heavily mineralised type of cartilage in the skeleton, which contains remnant bone cells," Professor Long said.

"It's almost a missing link condition showing that early sharks had a lot more bone in their skeleton, and that just before modern sharks evolved they lost the bone, with only the soft cartilage remaining."

Professor Long said the research indicates a direction in their evolution that shows that sharks to be much more specialised than previously thought.

The Gogo formation, which is the remains of a tropical reef now located far inland, has proved to be one of the most important sources of Devonian fossil fish in the world.

Professor Long said sharks are poorly known from the Devonian period, with research heavily reliant on fossil teeth. The rarity makes the Gogo shark all the more remarkable, Professor Long said.

"This is a partial articulated skeleton, with the jaws and shoulder and all the teeth and scales, but best of all, we have acid-etched the fossils out of the rock, so they are three-dimensional, uncrushed and perfect," he said. "It's the first time a shark of that age has been prepared in that manner."

"This is a really interesting discovery," said Professor Per Ahlberg, a palaeontologist at Uppsala University in Sweden, which was not involved in the study.

"The new Gogo shark shows what seems to be an early version of prismatic calcified cartilage: unlike the modern kind, the gaps between the prisms contain cells that resemble bone cells. This may help to explain the relationship between prismatic calcified cartilage and bone."

The find also represented a breakthrough in that it was the first specimen of a shark discovered at the Gogo site in 60 years of investigation.

"It means that we can go back and find more sharks with continued collecting," said Professor Long, who will head back to the site later this year.

Explore further

Ancient shark fossil reveals new insights into jaw evolution

More information: "First Shark from the Late Devonian (Frasnian) Gogo Formation, Western Australia Sheds New Light on the Development of Tessellated Calcified Cartilage." PLoS ONE 10(5): e0126066. DOI: 10.1371/journal.pone.0126066
Journal information: PLoS ONE

Citation: Fossil ancestor shows sharks have a bony past (2015, May 29) retrieved 18 August 2019 from
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.

Feedback to editors

User comments

May 29, 2015
The Cambrian explosion of multicelllar life has already been upset; the sponges first thought as original life have been replaced by comb jellies. Now sharks using calcium in other than teeth. Seems like the oceans were flooded with calcium and all life made use of it.

May 31, 2015
Seems all life shares the common molecular mechanisms of nutrient-dependent RNA-directed DNA methylation that links amino acids substitutions to the stability of organized genomes.

Neural crest cells (NCCs) comprise a multipotent, migratory cell population that generates a diverse array of cell and tissue types during vertebrate development. These include cartilage and bone, tendons, and connective tissue, as well as neurons, glia, melanocytes, and endocrine and adipose cells; this remarkable lineage potential persists into adult life. Taken together with a limited capacity for self-renewal, neural crest cells bear the hallmarks of stem and progenitor cells and are considered to be synonymous with vertebrate evolution. The neural crest has provided a system for exploring the mechanisms that govern developmental processes such as morphogenetic induction, cell migration, and fate determination.

May 31, 2015
all life shares a common ancestor--

There, I fixed for ya.

Jun 01, 2015
How does touting pseudoscientific nonsense fix anything for intelligent people?

A universal trend of amino acid gain and loss in protein evolution http://www.nature...306.html

Excerpt: "We cannot conceive of a global external factor that could cause, during this time, parallel evolution of amino acid compositions of proteins in 15 diverse taxa that represent all three domains of life and span a wide range of lifestyles and environments. Thus, currently, the most plausible hypothesis is that we are observing a universal, intrinsic trend that emerged before the last universal common ancestor of all extant organisms."

Why does the biologically uninformed science idiot, Stephen Taylor (aka Vietvet) think he is qualified to comment on every attempt I make to intelligently discuss what is known to serious scientists?

Jun 01, 2015
"...substitution of glycine for a chiral amino acid in GnRH during evolution allows a more constrained conformation for receptor binding and that this subtle single amino acid substitution in a site remote from the ligand functional domains has marked effects on its structure and activity." http://www.ncbi.n...16157590

"The discovery of the fact that one decapeptide molecule, among the GnRHs, was constructed perfectly at the beginning of 400 million years evolution and that it is not possible to improve its physiological potency using the any natural amino acid is, in my opinion, important, fascinating and beautiful." http://www.cabdir...798.html

Discovery of the "re-evolved" bacterial flagellum, links the four days it took for the organisms to adapt from RNA-mediated amino acid substitutions to cell type differentiation in all genera via the physiology of their reproduction and fixation of the amino acid substitutions.

Jun 01, 2015
Re: Physiological potency that arises from use of one natural amino acid is
...important, fascinating and beautiful.

That's why what is known about how RNA-mediated events, which link metabolic networks and genetic networks to physiological potency threatens biologically uninformed science idiots, like Stephen Taylor.

When serious scientists realize that no experimental evidence of biologically-based cause and effect explains cell type differentiation in all genera via evolutionary theory, they dismiss the basis for his comments: IGNORANCE! Indeed, most people dismiss the comments of all biologically uninformed science idiots.

We will, however, no doubt, continue to see their comments here on, where the moderators seem to encourage them. I think the moderators must want to expose ignorance.

They may be concerned that Stephen Taylor is not doing a great job of that on his own.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more