Crocodilian climate history points to possible refuges after dinosaur-killing asteroid
A new study suggests crocodilian relatives followed warm habitats over millions of years, possibly leaving some in regions that remained suitable after the asteroid impact.
Crocodilian relatives largely followed warm climates across their evolutionary history, a new study published in Science Advances finds. Reuters reported that this pattern may help explain why some survived the asteroid impact 66 million years ago: tropical and subtropical areas could have remained suitable refuges while many other habitats were disrupted.
The researchers compared more than 7,000 fossils and records covering over 400 living and extinct species with reconstructions of ancient climate and geography, according to a University College London account of the study. Reuters reported that the team examined the climatic conditions in which crocodilian relatives lived over time.
How crocodilian relatives followed warmth
Rather than repeatedly adapting to different climates, the animals generally moved with suitable warm environments, lead author Alfio Alessandro Chiarenza of University College London said, according to Reuters. Their ranges expanded toward the poles during warmer periods and contracted toward the equator as conditions cooled. The UCL account describes relatives living at high latitudes, including Antarctica, during the warmth of the early Eocene around 50 million years ago.
The pattern had exceptions. The UCL account identifies an extinct Australian crocodile group that adapted to drier conditions around 34 million years ago, as rainfall declined and the continent dried out. That departure shows why the broader finding describes a long-running tendency across the lineage.
What the asteroid simulations suggest
The impact at Chicxulub, off Mexico’s Yucatán Peninsula, caused a global environmental crisis in which about three-quarters of Earth’s species disappeared, including the non-avian dinosaurs, Reuters reported. In the study’s simulations, tropical and subtropical regions retained conditions suitable for crocodilian relatives under all but the most extreme impact scenario tested, Chiarenza said. The finding suggests some populations may have occupied refuges near the equator, among other factors that helped them survive.
Other characteristics may also have mattered. Reuters described crocodilians’ ability to enter dormancy during harsh heat, drought or cold. The UCL account names smaller body size, semiaquatic habits, flexible diets and relatively low energy needs as further possible advantages during environmental stress.
The study also has a present-day implication, according to UCL co-author Philip Mannion. If crocodilians have often responded to climate change by moving into suitable habitat, living species may need space to shift their ranges as the planet warms. Roads, farms and cities can make that movement harder, he said.
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Sources and context
- An affinity for warm climes has helped crocs thrive for eonsChannel NewsAsia (Reuters)
- Keeping to warm climates may have helped crocodiles outlast the dinosaursPhys.org / University College London
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