title: Sexually dimorphic tridimensionally preserved pterosaurs and their eggs from China.
abstract: BACKGROUND
  The pterosaur record is generally poor, with little information about their populations, and pterosaur eggs are even rarer, with only four isolated and flattened eggs found to date.
  
  
  RESULTS
  We report here a population of a new sexually dimorphic pterosaur species (Hamipterus tianshanensis gen. et sp. nov.), with five exceptionally well-preserved three-dimensional eggs, from the Early Cretaceous deposit in northwestern China. About 40 male and female individuals in total were recovered, but the actual number associated might be in the hundreds. All of the discovered skulls have crests, which exhibit two different morphologies in size, shape, and robustness. The eggs show pliable depressions with cracking and crazing on the outer surface. The eggshell, observed by scanning electron microscopy and energy-dispersive spectroscopy, comprises a thin calcareous external hard shell followed by a soft membrane.
  
  
  CONCLUSIONS
  These fossils shed new light on the reproductive strategy, ontogeny, and behavior of pterosaurs. The cranial crests show sexually dimorphic morphologies, with presumed males and females differing in crest size, shape, and robustness. Ontogenetic variation is reflected mainly in the expansion of the rostrum. The eggs have some external rigidity of the general pliable eggshell, and the microstructure of the eggshell is similar to that of some modern "soft" snake eggs. We suggest that this new pterosaur nested in colonies and thus exhibited gregarious behavior, a possible general trend for at least derived pterodactyloid pterosaurs.
authors.affiliation: Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, PO Box 643, Beijing 100044, China. Electronic address: wangxiaolin@ivpp.ac.cn.
authors.forename: Xiaolin
authors.initials: X
authors.lastname: Wang
authors.affiliation: Laboratory of Systematics and Taphonomy of Fossil Vertebrates, Department of Geology and Paleontology, Museu Nacional/Universidade Federal do Rio de Janeiro, Quinta da Boa Vista s/n, São Cristóvão, CEP 20940-040, Rio de Janeiro, RJ, Brazil. Electronic address: kellner@mn.ufrj.br.
authors.forename: Alexander W A
authors.initials: AWA
authors.lastname: Kellner
authors.affiliation: Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, PO Box 643, Beijing 100044, China; University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Shunxing
authors.initials: S
authors.lastname: Jiang
authors.affiliation: Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, PO Box 643, Beijing 100044, China.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Wang
authors.affiliation: Hami Museum, Hami 839000, China.
authors.forename: Yingxia
authors.initials: Y
authors.lastname: Ma
authors.affiliation: Hami Museum, Hami 839000, China.
authors.forename: Yahefujiang
authors.initials: Y
authors.lastname: Paidoula
authors.affiliation: Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, PO Box 643, Beijing 100044, China; University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Cheng
authors.affiliation: Department of Biology, Agrarian Sciences Center, Universidade Federal do Espírito Santo, Alto Universitário s/n, Caixa Postal 16, Guararema, CEP 29500-000, Alegre, ES, Brazil.
authors.forename: Taissa
authors.initials: T
authors.lastname: Rodrigues
authors.affiliation: Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, PO Box 643, Beijing 100044, China.
authors.forename: Xi
authors.initials: X
authors.lastname: Meng
authors.affiliation: Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, PO Box 643, Beijing 100044, China; University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Jialiang
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, PO Box 643, Beijing 100044, China; University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Ning
authors.initials: N
authors.lastname: Li
authors.affiliation: Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, PO Box 643, Beijing 100044, China.
authors.forename: Zhonghe
authors.initials: Z
authors.lastname: Zhou
mesh_terms: D000818:Animals; D002681:China; D005260:Female; D005580:Fossils / Q000033:anatomy & histology*; D008297:Male; D010063:Ovum / Q000502:physiology; D012098:Reproduction; D012104:Reptiles / Q000033:anatomy & histology* / Q000145:classification / Q000254:growth & development / Q000502:physiology*; D012727:Sex Characteristics; D012886:Skull / Q000033:anatomy & histology / Q000254:growth & development; D012919:Social Behavior