title: Fossil fishes from china provide first evidence of dermal pelvic girdles in osteichthyans.
abstract: BACKGROUND
  The pectoral and pelvic girdles support paired fins and limbs, and have transformed significantly in the diversification of gnathostomes or jawed vertebrates (including osteichthyans, chondrichthyans, acanthodians and placoderms). For instance, changes in the pectoral and pelvic girdles accompanied the transition of fins to limbs as some osteichthyans (a clade that contains the vast majority of vertebrates--bony fishes and tetrapods) ventured from aquatic to terrestrial environments. The fossil record shows that the pectoral girdles of early osteichthyans (e.g., Lophosteus, Andreolepis, Psarolepis and Guiyu) retained part of the primitive gnathostome pectoral girdle condition with spines and/or other dermal components. However, very little is known about the condition of the pelvic girdle in the earliest osteichthyans. Living osteichthyans, like chondrichthyans (cartilaginous fishes), have exclusively endoskeletal pelvic girdles, while dermal pelvic girdle components (plates and/or spines) have so far been found only in some extinct placoderms and acanthodians. Consequently, whether the pectoral and pelvic girdles are primitively similar in osteichthyans cannot be adequately evaluated, and phylogeny-based inferences regarding the primitive pelvic girdle condition in osteichthyans cannot be tested against available fossil evidence.
  
  
  RESULTS
  Here we report the first discovery of spine-bearing dermal pelvic girdles in early osteichthyans, based on a new articulated specimen of Guiyu oneiros from the Late Ludlow (Silurian) Kuanti Formation, Yunnan, as well as a re-examination of the previously described holotype. We also describe disarticulated pelvic girdles of Psarolepis romeri from the Lochkovian (Early Devonian) Xitun Formation, Yunnan, which resemble the previously reported pectoral girdles in having integrated dermal and endoskeletal components with polybasal fin articulation.
  
  
  CONCLUSIONS
  The new findings reveal hitherto unknown similarity in pectoral and pelvic girdles among early osteichthyans, and provide critical information for studying the evolution of pelvic girdles in osteichthyans and other gnathostomes.
authors.affiliation: Key Laboratory of Evolutionary Systematics of Vertebrates, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, China. zhumin@ivpp.ac.cn
authors.forename: Min
authors.initials: M
authors.lastname: Zhu
authors.forename: Xiaobo
authors.initials: X
authors.lastname: Yu
authors.forename: Brian
authors.initials: B
authors.lastname: Choo
authors.forename: Qingming
authors.initials: Q
authors.lastname: Qu
authors.forename: Liantao
authors.initials: L
authors.lastname: Jia
authors.forename: Wenjin
authors.initials: W
authors.lastname: Zhao
authors.forename: Tuo
authors.initials: T
authors.lastname: Qiao
authors.forename: Jing
authors.initials: J
authors.lastname: Lu
mesh_terms: D058500:Animal Fins; D000818:Animals; D005075:Biological Evolution; D002681:China; D005121:Extremities; D005399:Fishes / Q000145:classification; D005580:Fossils; D010163:Paleontology; D010388:Pelvis; D010802:Phylogeny; D014714:Vertebrates