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Extreme Triassic ecosystem instability suppressed tropical dinosaur dominance

Ben Creisler

A new online paper:

Jessica H. Whiteside, Sofie Lindström, Randall B. Irmis, Ian J.
Glasspool, Morgan F. Schaller, Maria Dunlavey, Sterling J. Nesbitt,
Nathan D. Smith, and Alan H. Turner (2015)
Extreme ecosystem instability suppressed tropical dinosaur dominance
for 30 million years.
Proceedings of the National Academy of Sciences (advance online publication)


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 CO2 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.


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 10–15 million years
after they became abundant and speciose at higher latitudes. New
palynological, wildfire, organic carbon isotope, and atmospheric pCO2
data from early dinosaur-bearing strata of low paleolatitudes in
western North America show that large, high-frequency, tightly
correlated variations in δ13Corg and palynomorph ecotypes occurred
within a context of elevated and increasing pCO2 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 CO2 environmental
conditions of the Late Triassic.


News release:

Why big dinosaurs steered clear of the tropics