Sauropod Dinosaurs Restricted To Earth's Warmer Regions: Study

Giant, long-necked sauropods, thought to include the largest land animals ever to have existed, preferred to live in warmer, more tropical regions on Earth, suggesting they may have had different physiology from other dinosaurs, according to a new study led by researchers at the University College London (UCL) and the University of Vigo in Spain, ScienceDaily reported.

Photo Insert: The interpreted origin of Diplodocus sauropod dinosaur leg bones that were found in fluvial mudshale.

The study, published in the journal Current Biology, investigated the enigma of why sauropod fossils are only found at lower latitudes, while fossils of other main dinosaur types seem ubiquitously present, with many located in the polar regions.

The researchers analyzed the fossil record across the Mesozoic era (the time of the dinosaurs), lasting from around 230 to 66 million years ago, looking at occurrences of fossils of the three main dinosaur types: Sauropods, which include the Brontosaurus and the Diplodocus, theropods ("lizard-hipped"), which include velociraptors and Tyrannosaurus rex, and ornithischians ("bird-hipped") such as the Triceratops.

Combining this fossil data with data about climate throughout the period, along with information about how continents have moved across the globe, the researchers concluded that sauropods were restricted to warmer, drier habitats than other dinosaurs. These habitats were likely to be open, semi-arid landscapes, similar to today's savannahs.

Co-author Dr. Philip Mannion (UCL Earth Sciences) said: "Our research shows that some parts of the planet always seemed to be too cold for sauropods. They seem to have avoided any temperatures approaching freezing. Other dinosaur types, in contrast, could thrive in Earth's polar regions, from innermost Antarctica to polar Alaska -- which, due to the warmer climate, were ice-free, with lush vegetation. This suggests sauropods had different thermal requirements from other dinosaurs, relying more on their external environment to heat their bodies -- slightly closer to being 'cold-blooded', like modern-day reptiles. Their grand size hints that this physiology may have been unique."

First author Dr. Alfio Alessandro Chiarenza, formerly of UCL who is now based at the University of Vigo, Spain, said: "It may be that sauropods were physiologically incapable of thriving in colder regions, or that they thrived less well in these areas than their dinosaurian cousins and were outcompeted. A mix of features may have helped sauropods shed heat more easily than mammals do today. Their long necks and tails would have given them a larger surface area, and they may have had a respiratory system more akin to birds, which is much more efficient.”

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