380 million year old fossil fish is oldest known livebearer

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Australian scientists have discovered a remarkably well-preserved 380 million year old fossil fish that represents the oldest known live bearing vertebrate.

The fossil, identified as a new genus and species of placoderm fish, represents a pregnant adult female with embryo inside its body cavity, connected by what strongly resembles an umbilical cord.

The preserved embryo was discovered inside the body cavity of its mother after the scientists used an acid immersion technique in order to study the fossil in more detail.

Only after the outer layers of rock were removed was the embryo discovered within the body cavity of the relatively complete adult specimen, close to its vertebral column. The position of the well-preserved embryo within the adult specimen suggested to the scientists that the smaller individual was contained within the mother s uterus rather than the gut.

The delicate bones of the embryo, which show little breakage or damage by stomach acids, and the characteristic tooth-plate morphology shared by both specimens further supports the claim that the smaller specimen contained within the body cavity of the larger specimen actually represents a juvenile of the same species and not an ingested prey item.

Though live bearing, also referred to as viviparity, is a common reproductive strategy amongst present day vertebrates, examples of live bearing in the fossil record are extremely rare.

The new fossil fish, named Materpiscis attenboroughi, (generic name derived from the latin meaning ~motherfish ; species name in honor of Sir David Attenborough) is exceptional not only because it provides a definitive example of viviparity in the fossil record but also because it suggests that a live bearing strategy, comparable to that of modern sharks and rays, originated in vertebrates at least 380 million years ago.

For more information on the new fossil livebearer see the article: Long J. A., Trinajstic K., Young G. C. & Senden T. 2008. Live birth in the Devonian period. Nature, 453: 650-652.

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