How big was a mosasaurus?

Quick Scoop

Mosasaurus was huge: many adults were about 39–42 feet long, and the largest estimates put some individuals at around 56–57 feet. Its weight is often estimated at roughly 5.5 to 15 metric tons, depending on the specimen and the study.

Size in context

That means Mosasaurus was longer than a school bus and among the biggest marine reptiles ever known. The exact size is still debated because the fossil record is incomplete, so different studies give different upper estimates.

Typical estimates

• Average adult length: about 12–13 meters, or 39–42 feet.
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• Maximum length: about 17 meters, or 56–57 feet, in the largest estimates.
[7][1]
• Estimated weight: around 5.5 to 15 metric tons, depending on the model used.
[3][1]

Bottom line

If you want the short answer: Mosasaurus was roughly 40 feet long on average, and the biggest ones may have reached about 57 feet.