title: A Silurian maxillate placoderm illuminates jaw evolution.
abstract: The discovery of Entelognathus revealed the presence of maxilla, premaxilla, and dentary, supposedly diagnostic osteichthyan bones, in a Silurian placoderm. However, the relationship between these marginal jaw bones and the gnathal plates of conventional placoderms, thought to represent the inner dental arcade, remains uncertain. Here we report a second Silurian maxillate placoderm, which bridges the gnathal and maxillate conditions. We propose that the maxilla, premaxilla, and dentary are homologous to the gnathal plates of placoderms and that all belong to the same dental arcade. The gnathal-maxillate transformation occurred concurrently in upper and lower jaws, predating the addition of infradentary bones to the lower jaw.
authors.affiliation: Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, PO Box 643, Beijing 100044, China. zhumin@ivpp.ac.cn per.ahlberg@ebc.uu.se.|College of Earth Science, University of Chinese Academy of Sciences, Beijing, 100049, China.
authors.forename: Min
authors.initials: M
authors.lastname: Zhu
authors.affiliation: Subdepartment of Evolution and Development, Department of Organismal Biology, Uppsala University, Norbyvägen 18A, SE-752 36 Uppsala, Sweden. zhumin@ivpp.ac.cn per.ahlberg@ebc.uu.se.
authors.forename: Per E
authors.initials: PE
authors.lastname: Ahlberg
authors.affiliation: Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, PO Box 643, Beijing 100044, China.|College of Earth Science, University of Chinese Academy of Sciences, Beijing, 100049, China.
authors.forename: Zhaohui
authors.initials: Z
authors.lastname: Pan
authors.affiliation: Subdepartment of Evolution and Development, Department of Organismal Biology, Uppsala University, Norbyvägen 18A, SE-752 36 Uppsala, Sweden.
authors.forename: Youan
authors.initials: Y
authors.lastname: Zhu
authors.affiliation: Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, PO Box 643, Beijing 100044, China.
authors.forename: Tuo
authors.initials: T
authors.lastname: Qiao
authors.affiliation: Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, PO Box 643, Beijing 100044, China.
authors.forename: Wenjin
authors.initials: W
authors.lastname: Zhao
authors.affiliation: Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, PO Box 643, Beijing 100044, China.
authors.forename: Liantao
authors.initials: L
authors.lastname: Jia
authors.affiliation: Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, PO Box 643, Beijing 100044, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Lu
mesh_terms: D000818:Animals; D005075:Biological Evolution; D003724:Dental Arch / Q000033:anatomy & histology; D005399:Fishes / Q000033:anatomy & histology / Q000145:classification; D005580:Fossils; D008334:Mandible / Q000033:anatomy & histology; D008437:Maxilla / Q000033:anatomy & histology; D010163:Paleontology; D010802:Phylogeny