Thursday, August 18, 2016

[PaleoIchthyology • 2008] Materpiscis attenboroughi • Live Birth in the Devonian Period: Placoderm Fish from the Gogo Area of north-west Western Australia

Materpiscis attenboroughi  Long, Trinajstic, Young & Senden, 2008 

Artist’s reconstruction of Materpiscis gen. nov. giving birth.
by B. Choo. DOI:  10.1038/nature06966 

Materpiscis attenboroughi  
Long, Trinajstic, Young & Senden, 2008

   a, Diagram showing position of embryo and yolk sac within the mother. b, Artist’s reconstruction of Materpiscis gen. nov. giving birth (by B. Choo).

The extinct placoderm fishes were the dominant group of vertebrates throughout the Middle Palaeozoic era, yet controversy about their relationships within the gnathostomes (jawed vertebrates) is partly due to different interpretations of their reproductive biology. Here we document the oldest record of a live-bearing vertebrate in a new ptyctodontid placoderm, Materpiscis attenboroughi gen. et sp. nov., from the Late Devonian Gogo Formation of Australia (approximately 380 million years ago). The new specimen, remarkably preserved in three dimensions, contains a single, intra-uterine embryo connected by a permineralized umbilical cord. An amorphous crystalline mass near the umbilical cord possibly represents the recrystallized yolk sac. Another ptyctodont from the Gogo Formation, Austroptyctodus gardineri, also shows three small embryos inside it in the same position. Ptyctodontids have already provided the oldest definite evidence for vertebrate copulation8, and the new specimens confirm that some placoderms had a remarkably advanced reproductive biology, comparable to that of some modern sharks and rays. The new discovery points to internal fertilization and viviparity in vertebrates as originating earliest within placoderms.

Placodermi McCoy, 1848
Ptyctodontida Gross, 1932

Materpiscis attenboroughi gen. et sp. nov.

Etymology. Generic name from the Latin meaning ‘mother fish’; species name in honour of Sir David Attenborough, who first drew attention to the Gogo fish sites in his 1979 series Life on Earth.

Holotype. WAM 07.12.1 (Western Australian Museum, Perth).

Age and locality. From the Stromatoporoid camp locality, Gogo Station, near Fitzroy Crossing, Western Australia (Late Devonian, early Frasnian).

Diagnosis. A small aspinothoracid ptyctodontid fish having an anteriorly pointed nuchal plate that participates in the posterior margin of the skull roof, broad roughly triangular-shaped preorbitals that meet mesially; the marginal plate has a large postorbital region with parallel rows of tubercles adorning it; the submarginal is strap-like and strongly curved mesially; robust triturating tooth plates that meet only at anterior tips, superognathals with moderately high anterior dorsal process. The body is scaleless.

Dr John Long of Museum Victoria in Melbourne holds a model of a placoderm fish fossil that was was found in the Gogo area of north-west Western Australia and was named Materpiscis attenboroughi.
 Photograph: William West/AFP/Getty Images 

John A. Long, Kate Trinajstic, Gavin C. Young and Tim Senden. 2008. Live Birth in the Devonian Period. Nature. 453; 650-652. DOI:  10.1038/nature06966 

Oldest Live-Birth Fossil Found; Fish Had Umbilical Cord