Geoscience Reference
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their model, they concluded that, yes indeed, sauropods alone could have produced
almost as much methane in a year as is made by all sources (human and non-hu-
man) today: about 570 million tons versus 600 million tons, respectively. Among
the factors they considered in their model were:
• Sauropod metabolism, such as whether they were endothermic or ecto-
thermic;
• Mode of digestion, in which they assumed sauropods used gut bacteria or
archeans to break down low-quality plant matter;
• An average sauropod size of 20 tons, which was typical for the Late Juras-
sic sauropod
Apatosaurus;
• Estimated sauropod herd size;
• Land area needed to ecologically support this dinosaur biomass;
• High ecological productivity of land ecosystems during the Mesozoic,
whichwaspartlyafunctionofhowaverageglobaltemperaturesweremuch
warmer than today.
So did Mesozoic global warming begin before dinosaurs added their gaseous
contributions to the atmosphere, or afterwards? This is actually a tough question to
answer,becauseunlikeothertimesinearth'shistory,theMesozoiclackedlongperi-
ods of global cooling. Instead, it was warm throughout almost its entire 185 milli-
on years, from the start of the Triassic Period to the end of the Cretaceous Period.
Dinosaurs were a part of this equation for the last 165 million of those years, but
the grandest of herbivorous gas-bag dinosaurs—sauropods—did not show up until
about the middle of the Jurassic, which is when they were joined by stegosaurs, an-
kylosaurs,andnodosaurs.Later,intheCretaceous,sauropodswereaccompaniedby
great numbers ofbigornithopods andceratopsians. This means that awarm climate
was started before the Late Triassic—which was when the dinosaurs arrived on the
scene—but dinosaurs may have done their part to keep the home fires burning once
they evolved, spread, and farted throughout the Jurassic and Cretaceous.
