Video: An exceptionally-preserved placoderm from the Silurian of China Digital dynamic restoration of specimen IVPP V18620 (holotype of Entelognathus primordialis gen. et sp. nov.) showing the cheek complex, sclerotic ring, mandible, submandibular and gular series in external and internal views. - Ancient fish face shows roots of modern jaw Primitive vertebrate's sophisticated mandible rewrites evolutionary tree. Nature 25 September 2013 doi:10.1038/nature.2013.13823 http://www.nature.com/news/ancient-fish-face-shows-roots-of-modern-jaw-1.13823 Reference A Silurian placoderm with osteichthyan-like marginal jaw bones Nature (2013) doi:10.1038/nature12617 http://www.nature.com/nature/journal/vaop/ncurrent/full/nature12617.html Abstract The gnathostome (jawed vertebrate) crown group comprises two extant clades with contrasting character complements. Notably, Chondrichthyes (cartilaginous fish) lack the large dermal bones that characterize Osteichthyes (bony fish and tetrapods). The polarities of these differences, and the morphology of the last common ancestor of crown gnathostomes, are the subject of continuing debate. Here we describe a three-dimensionally preserved 419-million-year-old placoderm fish from the Silurian of China that represents the first stem gnathostome with dermal marginal jaw bones (premaxilla, maxilla and dentary), features previously restricted to Osteichthyes. A phylogenetic analysis places the new form near the top of the gnathostome stem group but does not fully resolve its relationships to other placoderms. The analysis also assigns all acanthodians to the chondrichthyan stem group. These results suggest that the last common ancestor of Chondrichthyes and Osteichthyes had a macromeric dermal skeleton, and provide a new framework for studying crown gnathostome divergence. Supplementary information PDF: http://www.nature.com/nature/journal/vaop/ncurrent/extref/nature12617-s1.pdf - A jaw-dropping fossil fish (photo) https://www.facebook.com/stefano.dicriscio/media_set?set=a.576272099086976.1073741974.100001125725009&type;=1

• published: 27 Sep 2013
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