An enormous femur was retrieved from the Stonesfield limestone quarry in Oxfordshire, England, back in 1676. It’s thought to have belonged to the first dinosaur ever described, Megalosaurus bucklandii, but its discoverers didn't know what they were dealing with at the time. That meant when it was later depicted in the first known published illustration of a dinosaur bone appearing like two large, rounded balls with a wrinkly surface, it somehow ended up with the name Scrotum humanum.
The curious nomenclature followed the recent establishment of the binomial way of naming species introduced by Linnaeus in 1758. The system is still used today, applying a Latin genus and shorthand species name, which is why we're known as Homo sapiens.
In Plot’s defense, it appears he was aware that the bone wasn’t actually a giant pair of fossilized nads. Evidence for this is included in some of Plot’s notes that feature in a 2021 paper from Olivier Rieppel.
“I have one dug out of a Quarry in the Parish of Cornwell, and given me by the ingenious Sir Thomas Pennyson, that has exactly the figure of the lowermost part of the thigh-bone of a Man, or at least of some other Animal, with the capita femoris inferiora, between which are the anterior… and the larger posterior sinus, the feat of the strong ligament that rises out of the thigh, and that gives safe passage to the vessels descending into the leg: And a little above the sinus, where it seems to have been broken off, shewing the marrow … in the hollow of the bone.”
However, Plot was stumped by the enormity of the specimen. It was far too big for a human, despite looking just the same as our femurs, and it also was way too big for horses or cows. He also didn’t buy the theory it was a relic of the war elephants brought to the region back in Roman times, so what was it?
Being a religious man, Plot theorized it could belong to the giants described in the bible when he wrote “‘provided it be clearly made out that there have been Men and Women of proportionable stature in all ages of the World, down even to our own days”. Plot was often seeing human-like features reflected in ancient specimens, often comparing them to things like kidneys, brains, eyes, ears, hearts, and breasts.
It's perhaps here where things got a bit confused around our old pal Scrotum humanum, as Rieppel states that the name only appeared when the specimen was later re-described in a publication illustrated and published by Richard Brookes. It seems Brooke's depiction of the testicle-like specimen may have taken Plot’s comparison too literally, as the figure caption mistakenly immortalized its suggestive appearance with a curious scientific name.
It's now considered a nomen dubium, a name of questionable application, but it was a hit with 18th-century French philosopher Jean- Baptiste-René Robinet. In his early life, Robinet's figured stones theory suggested that they aren’t the rocky remains of past life, but instead, their own living organisms that develop, grow, and even reproduce. To that end, it's easy to see why Robinet liked Scrotum humanum so much.
“Of the stone called Scrotum humanum […] it is not only by its external shape that it imitates this part of a man,” he wrote. “The internal organization is likewise analogous. When we touch this stony Scrotum, we can nearly feel that each testicle is enclosed in its own muscular pouch, as if the inside were divided in two by the closure formed by the duplication of the dartos fascia, as is the case in the real human scrotum. Another singular feature of this stone is that one can see the upper part of a sort of canal, which is filled with a spongy substance, quite similar to the ureter.”
How accurate this description was is up for debate owing to the fact that Robinet isn’t thought to have ever directly seen or touched the specimen. It’s now thought to be the thigh bone of Megalosaurus, the first dinosaur ever to be described – but since the specimen has gone missing, it seems we’ll never get to the bottom of this testicular mystery.
If you think this story is weird, wait until you find out why the guy who actually named Megalosaurus ate a king's heart.