title: Theropod courtship: large scale physical evidence of display arenas and avian-like scrape ceremony behaviour by Cretaceous dinosaurs.
abstract: Relationships between non-avian theropod dinosaurs and extant and fossil birds are a major focus of current paleobiological research. Despite extensive phylogenetic and morphological support, behavioural evidence is mostly ambiguous and does not usually fossilize. Thus, inferences that dinosaurs, especially theropods displayed behaviour analogous to modern birds are intriguing but speculative. Here we present extensive and geographically widespread physical evidence of substrate scraping behavior by large theropods considered as compelling evidence of "display arenas" or leks, and consistent with "nest scrape display" behaviour among many extant ground-nesting birds. Large scrapes, up to 2 m in diameter, occur abundantly at several Cretaceous sites in Colorado. They constitute a previously unknown category of large dinosaurian trace fossil, inferred to fill gaps in our understanding of early phases in the breeding cycle of theropods. The trace makers were probably lekking species that were seasonally active at large display arena sites. Such scrapes indicate stereotypical avian behaviour hitherto unknown among Cretaceous theropods, and most likely associated with terrirorial activity in the breeding season. The scrapes most probably occur near nesting colonies, as yet unknown or no longer preserved in the immediate study areas. Thus, they provide clues to paleoenvironments where such nesting sites occurred.
authors.affiliation: University of Colorado Denver, Campus Box 172, Denver Colorado 80217-3364, USA.
authors.forename: Martin G
authors.initials: MG
authors.lastname: Lockley
authors.affiliation: Peace Region Palaeontological Research Center, Box 1540, Tumbler Ridge, British Columbia, V0C 2W0, Canada.
authors.forename: Richard T
authors.initials: RT
authors.lastname: McCrea
authors.affiliation: Peace Region Palaeontological Research Center, Box 1540, Tumbler Ridge, British Columbia, V0C 2W0, Canada.
authors.forename: Lisa G
authors.initials: LG
authors.lastname: Buckley
authors.affiliation: Natural Heritage Center, National Research Institute of Cultural Heritage, 927 Yudeng-ro, Seo-gu, Daejeon, 302-834, Korea.
authors.forename: Jong Deock
authors.initials: JD
authors.lastname: Lim
authors.affiliation: National Operations Center, USDOI-Bureau of Land Management, Denver, Colorado 80225, USA.
authors.forename: Neffra A
authors.initials: NA
authors.lastname: Matthews
authors.affiliation: Wyoming State Office, Bureau of Land Management, Cheyenne, Wyoming, 82003, USA.
authors.forename: Brent H
authors.initials: BH
authors.lastname: Breithaupt
authors.affiliation: University of Colorado Denver, Campus Box 172, Denver Colorado 80217-3364, USA.
authors.forename: Karen J
authors.initials: KJ
authors.lastname: Houck
authors.affiliation: Polish Geological Institute, ul. Rakowiecka 4, 00-975 Warszawa, Poland.
authors.forename: Gerard D
authors.initials: GD
authors.lastname: Gierliński
authors.affiliation: Department of Paleontology and Stratigraphy, Faculty of Earth Science, University of Silesia, ul. Bedzinska 60, 41-200 Sosnowiec, Poland.
authors.forename: Dawid
authors.initials: D
authors.lastname: Surmik
authors.affiliation: Department of Science Education, Chinju National University of Education, Jinju, Kyungnam, 660-756, Korea.
authors.forename: Kyung Soo
authors.initials: KS
authors.lastname: Kim
authors.affiliation: School of the Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China.
authors.forename: Lida
authors.initials: L
authors.lastname: Xing
authors.affiliation: Natural Heritage Center, National Research Institute of Cultural Heritage, 927 Yudeng-ro, Seo-gu, Daejeon, 302-834, Korea.
authors.forename: Dal Yong
authors.initials: DY
authors.lastname: Kong
authors.affiliation: 3072 Bison Ave, Grand Junction, CO, 81504, USA.
authors.forename: Ken
authors.initials: K
authors.lastname: Cart
authors.affiliation: Downey Ct., #2, Clifton, CO, 81520, USA.
authors.forename: Jason
authors.initials: J
authors.lastname: Martin
authors.affiliation: Bureau of Land Management, Uncompahgre Field Office, 2465 S. Townsend Ave., 81401 Montrose, Colorado, 81401, USA.
authors.forename: Glade
authors.initials: G
authors.lastname: Hadden
mesh_terms: D000818:Animals; D005075:Biological Evolution; D001717:Birds / Q000145:classification / Q000502:physiology*; D003120:Colorado; D003380:Courtship / Q000523:psychology*; D025061:Dinosaurs / Q000033:anatomy & histology / Q000145:classification / Q000502:physiology*; D053476:Extinction, Biological; D005260:Female; D005580:Fossils / Q000033:anatomy & histology*; D008297:Male; D009425:Nesting Behavior / Q000502:physiology*; D010802:Phylogeny