title: Isotopic ordering in eggshells reflects body temperatures and suggests differing thermophysiology in two Cretaceous dinosaurs.
abstract: Our understanding of the evolutionary transitions leading to the modern endothermic state of birds and mammals is incomplete, partly because tools available to study the thermophysiology of extinct vertebrates are limited. Here we show that clumped isotope analysis of eggshells can be used to determine body temperatures of females during periods of ovulation. Late Cretaceous titanosaurid eggshells yield temperatures similar to large modern endotherms. In contrast, oviraptorid eggshells yield temperatures lower than most modern endotherms but ∼ 6 °C higher than co-occurring abiogenic carbonates, implying that this taxon did not have thermoregulation comparable to modern birds, but was able to elevate its body temperature above environmental temperatures. Therefore, we observe no strong evidence for end-member ectothermy or endothermy in the species examined. Body temperatures for these two species indicate that variable thermoregulation likely existed among the non-avian dinosaurs and that not all dinosaurs had body temperatures in the range of that seen in modern birds.
authors.affiliation: Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, California 90095, USA.|Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125, USA.|European Institute of Marine Sciences (IUEM), Université de Brest, UMR 6539, Rue Dumont D'Urville, 29280 Plouzané, France.|Natural History Museum of Denmark, University of Copenhagen, Copenhagen K DK-1350, Denmark.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Eagle
authors.affiliation: Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, California 90095, USA.
authors.forename: Marcus
authors.initials: M
authors.lastname: Enriquez
authors.affiliation: Orcas Island Historical Museums, Eastsound, Washington 98245, USA.|CONCIET, Anillaco, Argentina.
authors.forename: Gerald
authors.initials: G
authors.lastname: Grellet-Tinner
authors.affiliation: Department of Geological Sciences, University of Alabama, Tuscaloosa, Alabama 35487, USA.
authors.forename: Alberto
authors.initials: A
authors.lastname: Pérez-Huerta
authors.affiliation: Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125, USA.
authors.forename: David
authors.initials: D
authors.lastname: Hu
authors.affiliation: Institute of Geosciences, University of Mainz, Johann-Joachim-Becherweg 21, Mainz 55128, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Tütken
authors.affiliation: Department of Ecology, Evolution, and Environmental Biology, Columbia University, New York, New York 10027, USA.
authors.forename: Shaena
authors.initials: S
authors.lastname: Montanari
authors.affiliation: Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, California 90095, USA.|Department of Geological Sciences, California State University, Fullerton, California 92831, USA.
authors.forename: Sean J
authors.initials: SJ
authors.lastname: Loyd
authors.affiliation: Department of Geosciences and Environment, California State University, Los Angeles, California 90032, USA.
authors.forename: Pedro
authors.initials: P
authors.lastname: Ramirez
authors.affiliation: Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, California 90095, USA.|European Institute of Marine Sciences (IUEM), Université de Brest, UMR 6539, Rue Dumont D'Urville, 29280 Plouzané, France.|Natural History Museum of Denmark, University of Copenhagen, Copenhagen K DK-1350, Denmark.|Department of Atmospheric and Oceanic Sciences, Institute of the Environment and Sustainability, California NanoSystems Institute, University of California, Los Angeles, California 90095, USA.
authors.forename: Aradhna K
authors.initials: AK
authors.lastname: Tripati
authors.affiliation: Department of Geosciences, Boise State University, Boise, Idaho 83725, USA.
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Kohn
authors.affiliation: Department of Geology and Geophysics, University of Utah, Salt Lake City, Utah 84112, USA.
authors.forename: Thure E
authors.initials: TE
authors.lastname: Cerling
authors.affiliation: Natural History Museum of Los Angeles County, Los Angeles, California 90007 USA.
authors.forename: Luis M
authors.initials: LM
authors.lastname: Chiappe
authors.affiliation: Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125, USA.
authors.forename: John M
authors.initials: JM
authors.lastname: Eiler
mesh_terms: D000818:Animals; D001831:Body Temperature; D002119:Calcium Carbonate / Q000032:analysis*; D025061:Dinosaurs / Q000502:physiology*; D005260:Female; D005580:Fossils; D007554:Isotopes / Q000032:analysis; D010060:Ovulation; D010063:Ovum / Q000737:chemistry*
chemical_list: D007554:Isotopes; D002119:Calcium Carbonate