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T. Rex Grew Slower Than We Thought!
15 Jan
Summary
- Tyrannosaurus rex took about 40 years to reach its maximum size.
- New study found previously unknown growth marks in leg bones.
- T. rex lifespan may have been longer, around 45 to 50 years.

The fearsome Tyrannosaurus rex, a contender for Earth's most massive land predator, may have achieved its formidable size at a more gradual pace than scientists once thought. New analysis of the microstructure in fossilized leg bones from 17 specimens suggests that T. rex took around 40 years to reach its full weight of approximately 8 tons. This timeframe is about 15 years longer than prior estimations, revealing a slower growth trajectory.
Researchers identified novel growth marks within the bones, visible only under polarized light, which indicate a more extended period at juvenile and subadult stages. This flexible growth pattern, with varying annual rings reflecting resource availability, allowed T. rex to survive harsh periods and outcompete other carnivores. The study, involving more specimens and a new statistical approach, also revises the estimated lifespan of T. rex to between 45 and 50 years, extending beyond the previously accepted 30 years.




