Materpiscis

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Materpiscis
Fossil range: Late Devonian

3D model of Materpiscis

Kingdom:	Animalia
Phylum:	Chordata
Class:	Placodermi
Order:	Ptyctodontida
Family:	Ptyctodontidae
Genus:	Materpiscis

Binomial name

M. attenboroughi
Long et al., 2008

Materpiscis (Latin: mother fish) is a genus of ptyctodontid placoderm (a class of shark-like fishes with no modern relatives) from the Late Devonian (about 380 million years ago) Gogo Formation of Western Australia. Known from only one specimen, it is unique in having an unborn embryo present inside Materpiscis, and with remarkable preservation of a mineralised placental feeding structure (umbilical cord). This makes Materpiscis the oldest known vertebrate to show viviparity, or giving birth to live young.

The fossil specimen was found in the Kimberley area of northern Western Australia by Lindsay Hatcher during the 2005 expedition to the Gogo led by John Long of Museum Victoria. Fossils from the Gogo Formation are preserved in limestone nodules, so dilute acetic acid is used to dissolve the surrounding limestone and reveal the fossil.^[1]

Fossilised embyro features

Model of Materpiscis on display at Museum Victoria, Australia

Examination of the tail section of the Materpiscis specimen led to the discovery of the partially ossified skeleton of a juvenile Materpiscis and the mineralised umbilical cord. The team published their findings in 2008.^[2] The species was named Materpiscis attenboroughi in honour of David Attenborough who first drew attention to the significance of the Gogo fish sites in his 1979 series Life on Earth.^[3]

Materpiscis would have been about 25 to 30 cm long and had powerful crushing tooth plates to grind up its prey, possibly hard shelled invertebrates like clams or corals.^[4]

The ptyctodontid fishes are the only group of placoderms to display sexual dimorphism, where males have clasping organs and females have smooth pelvic fin bases. It had long been suspected that they reproduced using internal fertilisation, but finding fossilised embryos inside both Materpiscis and in a similar form also from Gogo, Austroptyctodus, proved the deduction was true.