Cassius, the largest living crocodile in captivity, could be even bigger than previously thought.

The saltwater crocodile — who is thought to be 120 years old — entered the record books in 2011, when he measured nearly 18 feet (5.48 meters) long. But his keepers haven't measured him since, meaning Cassius may have grown even bigger since then.

"It's very possible Cassius may have grown bigger since 2011, however we have not attempted to remeasure him," Toody Scott, who looks after Cassius at Marineland Crocodile Park in Australia, told Guinness World Records. "We may attempt this in the near future to provide some insight into growth rates of large crocodiles or of course if his record was being challenged."

Saltwater crocodiles (Crocodylus porosus) can grow up to 23 feet (7 m) long, with another record holder — a 50-year-old, captive animal in the Philippines named Lolong — measuring more than 20 feet (6.17 m). Lolong was captured in 2012 and briefly replaced Cassius as record-holder, but the crocodile died one year later after flipping over with a bloated stomach and Cassius was reinstated as the world's largest captive croc.

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Despite having likely lived more than twice as long, Cassius probably won't catch up with his predecessor. "As crocodiles get larger than 5 m [16.4 feet], growth rates seem to slow to as little as 1 cm [0.4 inch a year] and in many instances the crocodile may stop growing," Scott said.

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But Cassius might also be missing a few inches as a result of injuries he sustained in the wild. When researchers captured him in 1984, the gigantic croc had been fighting other crocodiles over territory and attacking boat engines, resulting in him losing bits of his snout and tail. These missing body parts were not factored into his 2011 measurements and could have added an extra 6 to 10 inches (15 to 25 cm) to his length, according to Guinness World Records.

Based on the size of crocodiles that have lived in the Marineland park since birth, Cassius' keepers estimate the colossal croc was born in 1903. This year therefore marks the saltwater giant's 120th birthday, and his keepers say Cassius may have "years to come."

"Becoming a Guinness World Record holder certainly shot Cassius to 'croc-stardom,'" Scott said.