ABSTRACT Evidence of reproductive biology is extremely rare in the fossil record. Recently the first known embryos were discovered within the Placodermi1, an extinct class of armoured fish,

indicating a viviparous mode of reproduction in a vertebrate group outside the crown-group Gnathostomata (Chondrichthyes and Osteichthyes). These embryos were found in ptyctodontids, a small

group of placoderms phylogenetically basal to the largest group, the Arthrodira2,3. Here we report the discovery of embryos in the Arthrodira inside specimens of _Incisoscutum ritchiei_

from the Upper Devonian Gogo Formation of Western Australia4 (approximately 380 million years ago), providing the first evidence, to our knowledge, for reproduction using internal

ptyctodontids, arthrodires and chondrichthyans is difficult to reconcile in the light of current phylogenies of lower gnathostomes2,3,5, we explain these similarities as being most likely

due to convergence (homoplasy). These new finds confirm that reproduction by internal fertilization and viviparity was much more widespread in the earliest gnathostomes than had been

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Contact customer support SIMILAR CONTENT BEING VIEWED BY OTHERS FIRST REPORT OF RECURRENT PARTHENOGENESIS AS AN ADAPTIVE REPRODUCTIVE STRATEGY IN THE ENDANGERED COMMON SMOOTH-HOUND SHARK

_MUSTELUS MUSTELUS_ Article Open access 26 July 2024 DISCOVERY OF A NEW MODE OF OVIPAROUS REPRODUCTION IN SHARKS AND ITS EVOLUTIONARY IMPLICATIONS Article Open access 23 July 2020 INDUCED

SPAWNING WITH GAMETE RELEASE FROM BODY RUPTURES DURING REPRODUCTION OF _XENOTURBELLA BOCKI_ Article Open access 17 February 2023 REFERENCES * Long, J. A., Trinajstic, K., Young, G. C. &

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(1963) Download references ACKNOWLEDGEMENTS We thank M. Brazeau for access to his manuscript before publication, A. Ritchie for discussions, and G. Young and G. Edgecombe for reviewing the

manuscript. We also thank K. Bifield for the photograph of WAM 04.10.02, and the Centre for Microscopy, Characterisation and Analysis, UWA, for microscopy assistance. J.A.L. and K.T. are

supported by Australian Research Council Discovery grants. AUTHOR CONTRIBUTIONS All three authors contributed equally to the description of the new embryos and arthrodire pelvic structures,

and to the general discussion; J.A.L. provided new data on Victorian phyllolepids. AUTHOR INFORMATION AUTHORS AND AFFILIATIONS * Museum Victoria, PO Box 666, Melbourne 3001, Victoria,

Australia , John A. Long * Research School of Earth Sciences, The Australian National University, Canberra 2600, Australian Capital Territory, Australia , John A. Long * School of

Geosciences, Monash University, Clayton 3800, Victoria, Australia , John A. Long * School of Earth and Geographical Sciences, The University of Western Australia, Perth 6009, Western

Australia, Australia , Kate Trinajstic * Natural History Museum, Cromwell Road, London SW7 5BD, UK , Zerina Johanson Authors * John A. Long View author publications You can also search for

this author inPubMed Google Scholar * Kate Trinajstic View author publications You can also search for this author inPubMed Google Scholar * Zerina Johanson View author publications You can

also search for this author inPubMed Google Scholar CORRESPONDING AUTHOR Correspondence to John A. Long. SUPPLEMENTARY INFORMATION SUPPLEMENTARY INFORMATION This file contains Supplementary

Notes, Supplementary References and Supplementary Figures 1-3 with Legends (PDF 3355 kb) POWERPOINT SLIDES POWERPOINT SLIDE FOR FIG. 1 POWERPOINT SLIDE FOR FIG. 2 POWERPOINT SLIDE FOR FIG. 3

RIGHTS AND PERMISSIONS Reprints and permissions ABOUT THIS ARTICLE CITE THIS ARTICLE Long, J., Trinajstic, K. & Johanson, Z. Devonian arthrodire embryos and the origin of internal

fertilization in vertebrates. _Nature_ 457, 1124–1127 (2009). https://doi.org/10.1038/nature07732 Download citation * Received: 12 November 2008 * Accepted: 17 December 2008 * Issue Date: 26

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