title: A new basal sauropod dinosaur from the middle Jurassic of Niger and the early evolution of sauropoda.
abstract: BACKGROUND
  The early evolution of sauropod dinosaurs is poorly understood because of a highly incomplete fossil record. New discoveries of Early and Middle Jurassic sauropods have a great potential to lead to a better understanding of early sauropod evolution and to reevaluate the patterns of sauropod diversification.
  
  
  RESULTS
  A new sauropod from the Middle Jurassic of Niger, Spinophorosaurus nigerensis n. gen. et sp., is the most complete basal sauropod currently known. The taxon shares many anatomical characters with Middle Jurassic East Asian sauropods, while it is strongly dissimilar to Lower and Middle Jurassic South American and Indian forms. A possible explanation for this pattern is a separation of Laurasian and South Gondwanan Middle Jurassic sauropod faunas by geographic barriers. Integration of phylogenetic analyses and paleogeographic data reveals congruence between early sauropod evolution and hypotheses about Jurassic paleoclimate and phytogeography.
  
  
  CONCLUSIONS
  Spinophorosaurus demonstrates that many putatively derived characters of Middle Jurassic East Asian sauropods are plesiomorphic for eusauropods, while South Gondwanan eusauropods may represent a specialized line. The anatomy of Spinophorosaurus indicates that key innovations in Jurassic sauropod evolution might have taken place in North Africa, an area close to the equator with summer-wet climate at that time. Jurassic climatic zones and phytogeography possibly controlled early sauropod diversification.
authors.affiliation: Paleontology, Steinmann Institute for Geology, Mineralogy and Paleontology, University of Bonn, Bonn, Germany. kristian.remes@uni-bonn.de
authors.forename: Kristian
authors.initials: K
authors.lastname: Remes
authors.forename: Francisco
authors.initials: F
authors.lastname: Ortega
authors.forename: Ignacio
authors.initials: I
authors.lastname: Fierro
authors.forename: Ulrich
authors.initials: U
authors.lastname: Joger
authors.forename: Ralf
authors.initials: R
authors.lastname: Kosma
authors.forename: José Manuel Marín
authors.initials: JM
authors.lastname: Ferrer
authors.forename: Oumarou Amadou
authors.initials: OA
authors.lastname: Ide
authors.forename: Abdoulaye
authors.initials: A
authors.lastname: Maga
mesh_terms: D000818:Animals; D044822:Biodiversity; D005075:Biological Evolution; D002980:Climate; D025061:Dinosaurs / Q000033:anatomy & histology / Q000145:classification*; D053476:Extinction, Biological; D005580:Fossils; D005843:Geography; D009548:Niger; D010163:Paleontology / Q000379:methods; D010802:Phylogeny; D011157:Population Dynamics; D013997:Time Factors