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Theropod "lek" nest scrape display arenas as Cretaceous trace fossils (free pdf)

Ben Creisler

A new paper:

Martin G. Lockley, Richard T. McCrea, Lisa G. Buckley, Jong Deock Lim,
Neffra A. Matthews, Brent H. Breithaupt, Karen J. Houck, Gerard D.
Gierliński, Dawid Surmik, Kyung Soo Kim, Lida Xing, Dal Yong Kong, Ken
Cart, Jason Martin & Glade Hadden (2016)
Theropod courtship: large scale physical evidence of display arenas
and avian-like scrape ceremony behaviour by Cretaceous dinosaurs.
Scientific Reports 6, Article number: 18952

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.