Extreme ecosystem instability suppressed tropical dinosaur dominance for 30 million years

A major unresolved aspect of the rise of dinosaurs is why early dinosaurs and their relatives were rare and species-poor at low paleolatitudes throughout the Late Triassic Period, a pattern persisting 30 million years after their origin and 10â15 million years after they became abundant and specio...

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Published in:	Proceedings of the National Academy of Sciences - PNAS Vol. 112; no. 26; pp. 7909 - 7913
Main Authors:	Whiteside, Jessica H, Sofie LindstroÌm, Randall B. Irmis, Ian J. Glasspool, Morgan F. Schaller, Maria Dunlavey, Sterling J. Nesbitt, Nathan D. Smith, Alan H. Turner
Format:	Journal Article
Language:	English
Published:	United States National Academy of Sciences 30-06-2015 National Acad Sciences
Subjects:	Animals atmospheric CO2 Biological Sciences carbon cycling Carbon dioxide Carbon Isotopes - analysis climate climate change Correlation analysis Dinosaurs Early Mesozoic Ecosystem Environmental conditions environmental factors fauna Fires Forest & brush fires fossils herbivores Hot Temperature Isotopes latitude paleoclimatology Physical Sciences terrestrial ecosystems Tropical Climate vertebrates wildfires North America carbon cycling atmospheric CO2 Early Mesozoic terrestrial ecosystems wildfires
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Summary:	A major unresolved aspect of the rise of dinosaurs is why early dinosaurs and their relatives were rare and species-poor at low paleolatitudes throughout the Late Triassic Period, a pattern persisting 30 million years after their origin and 10â15 million years after they became abundant and speciose at higher latitudes. New palynological, wildfire, organic carbon isotope, and atmospheric p CO â data from early dinosaur-bearing strata of low paleolatitudes in western North America show that large, high-frequency, tightly correlated variations in Î´ Â¹Â³C âáµ£g and palynomorph ecotypes occurred within a context of elevated and increasing p CO â and pervasive wildfires. Whereas pseudosuchian archosaur-dominated communities were able to persist in these same regions under rapidly fluctuating extreme climatic conditions until the end-Triassic, large-bodied, fast-growing tachymetabolic dinosaurian herbivores requiring greater resources were unable to adapt to unstable high CO â environmental conditions of the Late Triassic. Significance This is, to our knowledge, the first multiproxy study of climate and associated faunal change for an early Mesozoic terrestrial ecosystem containing an extensive vertebrate fossil record, including early dinosaurs. Our detailed and coupled high-resolution records allow us to sensitively examine the interplay between climate change and ecosystem evolution at low paleolatitudes during this critical interval of Earth's history when modern terrestrial ecosystems first evolved against a backdrop of high CO â in a hothouse world. We demonstrate that these terrestrial ecosystems evolved within a generally arid but strongly fluctuating paleoclimate that was subject to pervasive wildfires, and that these environmental conditions in the early Mesozoic prevented large active warm-blooded herbivorous dinosaurs from becoming established in subtropical low latitudes until later in the Mesozoic.
Bibliography:	http://dx.doi.org/10.1073/pnas.1505252112 ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 2Present address: The Dinosaur Institute, Natural History Museum of Los Angeles County, Los Angeles, CA 90007. Edited by Paul E. Olsen, Columbia University, Palisades, NY, and approved May 15, 2015 (received for review March 25, 2015) Author contributions: J.H.W. and R.B.I. designed research; J.H.W., S.L., R.B.I., I.J.G., M.F.S., and M.D. performed research; J.H.W., S.L., R.B.I., I.J.G., M.F.S., S.J.N., N.D.S., and A.H.T. analyzed data; and J.H.W., S.L., R.B.I., I.J.G., S.J.N., N.D.S., and A.H.T. wrote the paper.
ISSN:	0027-8424 1091-6490
DOI:	10.1073/pnas.1505252112