A primitive placoderm sheds light on the origin of the jawed vertebrate face
2014 (English)In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 507, no 7493, 500-503 p.Article in journal (Refereed) Published
Extant vertebrates form two clades, the jawless Cyclostomata (lampreys and hagfishes) and the jawed Gnathostomata (all other vertebrates), with contrasting facial architectures(1,2). These arise during development from just a few key differences in the growth patterns of the cranial primordia: notably, the nasal sacs and hypophysis originate from a single placode in cyclostomes but from separate placodes in gnathostomes, and infraoptic ectomesenchyme migrates forward either side of the single placode in cyclostomes but between the placodes in gnathostomes(3-8). Fossil stem gnathostomes preserve cranial anatomies rich in landmarks that provide proxies for developmental processes and allow the transition from jawless to jawed vertebrates to be broken down into evolutionary steps(7,9-12). Here we use propagation phase contrast synchrotron microtomography to image the cranial anatomy of the primitive placoderm (jawed stem gnathostome) Romundina(13), and show that itcombines jawed vertebrate architecture with cranial and cerebral proportions resembling those of cyclostomes and the galeaspid (jawless stem gnathostome) Shuyu(11). This combination seems to be primitive for jawed vertebrates, and suggests a decoupling between ectomesenchymal growth trajectory, ectomesenchymal proliferation, and cerebral shape change during the origin of gnathostomes.
Place, publisher, year, edition, pages
2014. Vol. 507, no 7493, 500-503 p.
IdentifiersURN: urn:nbn:se:uu:diva-224362DOI: 10.1038/nature12980ISI: 000333402000041OAI: oai:DiVA.org:uu-224362DiVA: diva2:716462
FunderEU, European Research Council, 233111Knut and Alice Wallenberg Foundation