LETTERS Live birth in the Devonian period John A. Long 1,2,3 , Kate Trinajstic 4 , Gavin C. Young 2 & Tim Senden 5 The extinct placoderm fishes were the dominant group of verte- brates throughout the Middle Palaeozoic era 1 , yet controversy about their relationships within the gnathostomes (jawed verte- brates) is partly due to different interpretations of their repro- ductive biology 2–5 . 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) 6 . 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 7 , also shows three small embryos inside it in the same position. Ptyctodontids have already provided the oldest definite evidence for vertebrate copulation 8 , 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 ante- riorly 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. Description. Materpiscis gen. nov. (Figs 1–3) is readily distinguished from all other known ptyctodontids by the combination of lacking a spinal plate with anteriorly pointed nuchal plate (Fig. 1e), and a much-expanded postorbital region on the marginal plate (Fig. 1f). The nuchal plate participates in the posterior margin of the skull roof and the centrals are unusually broad (Fig. 1e). The skull roof is unusual in having prominent raised ridges for the main sensory-line canals (Fig. 1e). The tooth plates can be moved against each other as in life. This shows that only the anterior-most biting edges of the jaws met in full occlusion (Fig. 1i). The trunk shield plates do not differ significantly from those of many other aspinothoracid ptyctodontids, in particular Austroptyctodus 7 , except for proportions and ornamentation, the median dorsal having a low median crest. A restoration of the dermal armour is shown in Fig. 1h. A detailed description of the dermal and axial skeleton, braincase and dentition of Materpiscis gen. nov., and its embryonic skeletal morphology, will be published elsewhere. The Gogo Formation has yielded the earliest phosphatized gnathostome muscle tissues and nerve fibres 9 , and the new specimen shows additional soft-tissue preservation never before recorded in any fossil. The new specimen is exceptional in revealing a small partial skeleton located within the upper body cavity of a pregnant, adult female ptyctodontid placoderm (Fig. 1a–d). The relatively complete adult skeleton includes much of the tail (Fig. 1a). The single, partially ossified juvenile skeleton inside the body cavity of the adult clearly belongs to the same species based on characteristic tooth-plate and marginal plate morphology (Fig. 1c, d). The small internal individual must be an embryo, rather than an ingested prey item, because the delicate bones show no breakage or etching from stomach acids, and the dentition is of similar gross morphology to that of the adult. The location of the preserved embryo close to the vertebral column suggests that it is in the uterus rather than the gut, a view supported by the presence of mineralized soft tissue forming a placental connection between embryo and mother. Furthermore, a second specimen from Gogo, previously described as Austroptyctodus gardineri 7 , has been re-examined and we have identified three small embryos in the same position posterior to the adult anterior lateral plate as in Materpiscis gen. nov. (Fig. 1g). Cases demonstrating viviparity in the fossil record are extremely rare, the best being Mesozoic ichthyosaurs 10,11 and mosasauroids 12 . Presumed fetal specimens of a holocephalan fish from the Lower Carboniferous of Montana 13 may extend the record of viviparity back into the Palaeozoic era, but were not found in or near the body cavity of the mother. Our new example extends the definite record of vertebrate viviparity back by some 200 million years. The embryos of Materpiscis gen. nov. and Austroptyctodus are about 25% of the adult size, based on proportions of the anterior lateral plate. The embryonic bones are remarkably thin and fragile, yet perfectly preserved, with the upper and lower dentition still in occlusion in Materpiscis gen. nov. (Figs 1b–d and 2g). The skull bones of this specimen are oriented posteriorly, indicating that the embryo was curled. Only some dermal plates are represented in the embryos. Absence of certain bones at an early developmental stage is also recorded in tiny (14–16 mm) juvenile skeletons of the antiarch placoderm Asterolepis 14 . Identified embryonic bones comprise paired preorbitals, a paranuchal, anterior dorsolateral, anterior lateral and a marginal plate, and both sets of tooth plates in articulation (Figs 1b–d, g and 2g, f). The supragnathals of Materpiscis gen. nov. meet at a distinct medially directed symphysis (sym, Fig. 2g), lending increased structural support for biting ability immediately after birth. 1 Museum Victoria, Melbourne, PO Box 666, Melbourne 3001, Australia. 2 Research School of Earth Sciences, The Australian National University, Canberra 0200, Australia. 3 School of Geosciences, Monash University, Clayton, Victoria 3800, Australia. 4 School of Earth and Geographical Sciences, The University of Western Australia, Perth 6009, Western Australia, Australia. 5 Department of Applied Mathematics, Research School of Physical Sciences and Engineering, The Australian National University, Canberra 0200, Australia. Vol 453 | 29 May 2008 | doi:10.1038/nature06966 650 Nature Publishing Group ©2008