Great white shark maximum length

Children’s encyclopedia (60s-70s) used to say the GWS could reach a maximum length of 45 feet but current definitions simply say it could exceed 6.1 meters (20 feet.) What was the basis for the initial estimate and what caused the downward adjustment?

I suspect there could have been confusion between GWS and the most recent fossils of megalodon but megalodon was already known in the 60s (i first saw the famous people-inside-the-open-jaw picture in a 70s guiness book.)

Until a real biologist chimes in. . .
Concerning Megalodon, remember that the early Guinness books once had it attaining a length of 120 feet, which has since been revised downward quite a bit. Possibly the same reevaluation was done to the Great White.

And I won’t forget them when they’re gone.

Seems to me that the largest (longest) documented GW’s have been just over 20 feet, with much older, less dependable/suspect reports going several feet longer.
In a recent book about the Farallon Island shark population, the author casually refers to 25-footers as if they’re not unusual, but IMO other aspects of her story undermine her credibility.

I think one contributing factor may have been that the “Port Fairy Shark” was reported to be 36 or so feet. This measurement dates back awhile (to the 19th century, IIRC), and so reports of sharks greater than than 20-25 feet didn’t seem implausible.

I think the “Port Fairy Shark” jaws were later measured and its predicted length was about 20 feet–still a big fish, but not nearly as big as it had been thought.

Is the Farallon book The Devil’s Teeth? I’ve read another book by her and don’t find her to be the most objective author.

That’s a good way to put it. That’s the book.