Megalodon was the largest predatory shark that ever lived, and its younger had been additionally gargantuan; at start, they had been as huge as the common basketball participant.
How did bouncing child megalodons gasoline their spectacular embryonic development? They might have wolfed up their smaller siblings whereas nonetheless within the mom’s womb, a survival technique shared by some trendy sharks.
Researchers lately calculated the dimensions of megalodon infants by analyzing skeletal fossils of an grownup Otodus megalodon that measured about 30 ft (9 meters) lengthy when it died (these monster sharks might doubtless attain about 66 ft, or 20 m). The scientists then checked out “development rings” in items of the shark’s preserved skeleton, just like the rings in tree trunks used to find out a tree’s age.
Associated: 7 unanswered questions about sharks
Megalodon — and all sharks, skates and rays — belong to a category of fishes referred to as Chondrichthyes, which have skeletons manufactured from cartilage somewhat than laborious bone. Extinct cartilaginous fish like megalodon and different megatooth sharks are due to this fact recognized principally from their enamel, which had been manufactured from calcium and due to this fact survive within the fossil document longer than these fishes’ delicate cartilaginous skeletons.
However for the brand new examine, printed on-line Jan. 11 within the journal Historical Biology, the authors examined a uncommon assortment of 150 megalodon vertebrae whose cartilage had mineralized, “the one moderately preserved vertebral column of the species in all the world,” they wrote.
Utilizing computed X-ray tomography (CT) scans, the scientists counted 46 regularly-spaced development rings in three of the megalodon’s vertebrae. They then utilized a mathematical development curve equation that is generally used to calculate development patterns in trendy sharks, based mostly on development bands of their spinal cartilage, stated lead creator Kenshu Shimada, a professor of paleobiology at DePaul College in Chicago and analysis affiliate on the Sternberg Museum in Kansas.
Every ring represented a yr of development, so the shark would have been about 46 years previous when it died. By working backwards to the earliest development ring — the “band at start” — the scientists calculated the shark’s size as a new child, estimating it to be round 6.6 ft (2 meters) lengthy — larger than any recognized new child sharks. Whereas prior research had famous the presence of those rings in megalodon fossils, “no detailed analyses had been performed previous to this new examine,” Shimada informed Dwell Science in an e mail.
Such giant infants would doubtless have been born dwell, the examine authors reported. Nourishing such monumental younger would have carried excessive power prices for the mom, suggesting that her infants supplemented in-utero vitamins with a facet serving to of unborn sibling cannibalism, Shimada stated.
“Oophagy — egg-eating — is a method for a mom to nourish its embryos for an prolonged time period,” he defined. “The consequence is that, whereas only some embryos per mom will survive and develop, every embryo can turn into fairly giant at its start.”
Examination of the vertebrae’s rings additionally revealed the shark in all probability grew slowly, with a barely greater development charge throughout its first seven years of life. Based mostly on the house between rings, the megalodon did not expertise a speedy development spurt in its youth as some animals do. Maybe that is as a result of it was already sufficiently big at start to compete for meals and discourage predator assaults, the examine authors reported.
By combining the expansion trajectory findings with knowledge about physique dimension within the largest recognized people, the researchers estimated that megalodon sharks could have lived to be a minimum of 88 to 100 years previous. Nevertheless, this inferred life expectancy “stays somewhat theoretical and wishes additional investigation,” Shimada stated.
Initially printed on Dwell Science.