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

Correspondence to: John A. Long^1,2,3 Correspondence and requests for materials should be addressed to J.A.L. (Email: jlong@museum.vic.gov.au).

The extinct placoderm fishes were the dominant group of vertebrates throughout the Middle Palaeozoic era¹, yet controversy about their relationships within the gnathostomes (jawed vertebrates) is partly due to different interpretations of their reproductive biology^{2, 3, 4, 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 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.

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