title: The largest Silurian vertebrate and its palaeoecological implications.
abstract: An apparent absence of Silurian fishes more than half-a-metre in length has been viewed as evidence that gnathostomes were restricted in size and diversity prior to the Devonian. Here we describe the largest pre-Devonian vertebrate (Megamastax amblyodus gen. et sp. nov.), a predatory marine osteichthyan from the Silurian Kuanti Formation (late Ludlow, ~423 million years ago) of Yunnan, China, with an estimated length of about 1 meter. The unusual dentition of the new form suggests a durophagous diet which, combined with its large size, indicates a considerable degree of trophic specialisation among early osteichthyans. The lack of large Silurian vertebrates has recently been used as constraint in palaeoatmospheric modelling, with purported lower oxygen levels imposing a physiological size limit. Regardless of the exact causal relationship between oxygen availability and evolutionary success, this finding refutes the assumption that pre-Emsian vertebrates were restricted to small body sizes.
authors.affiliation: 1] Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of SciencesPO Box 643, Beijing 100044, China [2] School of Biological Sciences, Flinders University, GPO Box 2100, Adelaide 5001, South Australia.
authors.forename: Brian
authors.initials: B
authors.lastname: Choo
authors.affiliation: Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of SciencesPO Box 643, Beijing 100044, China.
authors.forename: Min
authors.initials: M
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 SciencesPO 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 SciencesPO Box 643, Beijing 100044, China.
authors.forename: Liaotao
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 SciencesPO Box 643, Beijing 100044, China.
authors.forename: You'an
authors.initials: Y
authors.lastname: Zhu
mesh_terms: D000818:Animals; D005075:Biological Evolution; D049628:Body Size; D002681:China; D005399:Fishes / Q000033:anatomy & histology* / Q000145:classification*; D005580:Fossils / Q000033:anatomy & histology*; D005843:Geography; D009752:Nutritional Status; D010100:Oxygen / Q000378:metabolism; D010163:Paleontology; D014070:Tooth / Q000033:anatomy & histology*; D014714:Vertebrates / Q000033:anatomy & histology*
chemical_list: D010100:Oxygen