title: Digit-only sauropod pes trackways from China--evidence of swimming or a preservational phenomenon?
abstract: For more than 70 years unusual sauropod trackways have played a pivotal role in debates about the swimming ability of sauropods. Most claims that sauropods could swim have been based on manus-only or manus-dominated trackways. However none of these incomplete trackways has been entirely convincing, and most have proved to be taphonomic artifacts, either undertracks or the result of differential depth of penetration of manus and pes tracks, but otherwise showed the typical pattern of normal walking trackways. Here we report an assemblage of unusual sauropod tracks from the Lower Cretaceous Hekou Group of Gansu Province, northern China, characterized by the preservation of only the pes claw traces, that we interpret as having been left by walking, not buoyant or swimming, individuals. They are interpreted as the result of animals moving on a soft mud-silt substrate, projecting their claws deeply to register their traces on an underlying sand layer where they gained more grip during progression. Other sauropod walking trackways on the same surface with both pes and manus traces preserved, were probably left earlier on relatively firm substrates that predated the deposition of soft mud and silt . Presently, there is no convincing evidence of swimming sauropods from their trackways, which is not to say that sauropods did not swim at all.
authors.affiliation: School of the Earth Sciences and Resources, China University of Geosciences, Beijing, China.
authors.forename: Lida
authors.initials: L
authors.lastname: Xing
authors.affiliation: Geological Museum of Gansu, Lanzhou 730040, China.
authors.forename: Daqing
authors.initials: D
authors.lastname: Li
authors.affiliation: Structure and Motion Laboratory, Department of Comparative Biomedical Sciences, Royal Veterinary College, Hatfield AL97TA, UK.|Department of Ecology and Evolutionary Biology, Brown University, Providence, RI 02912, USA.
authors.forename: Peter L
authors.initials: PL
authors.lastname: Falkingham
authors.affiliation: Dinosaur Trackers Research Group, University of Colorado, Denver, Colorado, USA.
authors.forename: Martin G
authors.initials: MG
authors.lastname: Lockley
authors.affiliation: School of Earth Sciences, University of Bristol, Bristol, BS8 1RJ, UK.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Benton
authors.affiliation: Saurierwelt Paläontologisches Museum, Alte Richt 7, D-92318 Neumarkt, Germany.
authors.forename: Hendrik
authors.initials: H
authors.lastname: Klein
authors.affiliation: School of the Earth Sciences and Resources, China University of Geosciences, Beijing, China.
authors.forename: Jianping
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Ecology of Rare and Endangered Species and Environmental Protection, Ministry of Education, Guilin 541004, China.
authors.forename: Hao
authors.initials: H
authors.lastname: Ran
authors.affiliation: Department of Biological Sciences, University of Alberta 11455 Saskatchewan Drive, Edmonton, Alberta T6G 2E9, Canada.
authors.forename: W Scott
authors.initials: WS
authors.lastname: Persons
authors.affiliation: No. 208 Hydrogeological and Engineering Geological Team, Chongqing Bureau of Geological and Mineral Resource Exploration and Development, Chongqing 400700, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Dai
mesh_terms: D000818:Animals; D002681:China; D025061:Dinosaurs / Q000033:anatomy & histology* / Q000502:physiology*; D006614:Hindlimb / Q000033:anatomy & histology* / Q000502:physiology*; D013550:Swimming / Q000502:physiology*