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Troodontid nests with overlying clutches show site reuse and fidelity

Ben Creisler

A new online paper:

David J. Varricchio, Xingsheng Jin & Frankie D. Jackson (2015)
Lay, brood, repeat: nest reuse and site fidelity in ecologic time for
two Cretaceous troodontid dinosaurs.
Journal of Vertebrate Paleontology (advance online publication)

Whereas ‘biological site fidelity’ refers to the regular reuse of a
favored locale (e.g., breeding ground or nest) by an individual
animal, ‘paleontological site fidelity’ typically refers to repeated
use of a nesting locality by a herd or species over geologic time
scales. Two new Cretaceous specimens from the Two Medicine Formation
of Montana, U.S.A., and the Liantoutang Formation of Zhejiang, China,
each preserve two closely superimposed clutches of the egg form
Prismatoolithus. These eggs belong to the Troodontidae, small theropod
dinosaurs sharing a close ancestry with Aves. In both specimens, eggs
of a lower clutch are truncated at a level below what would normally
preserve in an undisturbed hatched clutch. These traces differ from
past examples of dinosaur site fidelity in (1) the close or
cross-cutting relationship of the clutches, (2) the precise overlay of
clutch atop clutch, and (3) the implication of nest reuse and, thus,
site fidelity on an ecologic rather than geologic scale and at
approximately the individual rather than species level. Given the
likely extended occupation of troodontid nesting sites by attending
adults, factors such as nesting success and territoriality may, in
addition to favorable substrates, have influenced the behaviors
recorded by these specimens. The arrangements of eggs as clutches
within the geologic record represent trace fossils. Thus, they record
past in situ behavior, providing important insight into dinosaur
nesting. In addition, they can serve as independent indicators of
substrate conditions and sedimentary history, potentially refining our
understanding of paleoenvironments.