Large Crocodilian Coprolite

Crocodile Rock
United States
South Carolina US
21 cm dia x 16 cm long
I remember when I was young,
Me and Grandpa had so much fun. 
We would find and polish stones. 
Had fun back then but now I’m all grown. 
Now the biggest kick I ever got
Was learning ‘bout crocodile rock. 
While the other folks are staring at the clock, 
I’m doin’ the math to find the length of a croc. 

La lalalala la lalalala la lalalala la

Can you tell I’m an Elton John fan? It’s no wonder I grew up to love coprolites listening to a singer that changed his last name to John.

Okay, let's get serious. Because of the location in which it was found and it's size, shape, and lack of inclusions, this coprolite is thought to be from a crocodile. Did you know scientists did a study to determine that you can estimate the length of a crocodilian (alligators, crocodiles, caimans and gharials) based on the diameter of its poop? It's true! The formula is:

[Coprolite Diameter (cm) - 1.10]/0.012 = Croc's Length (cm)

So let's see how big the croc was that ejected this beauty. Since coprolites rarely have a circular cross section I usually first measure the circumference. In this case, the circumference is approximately 21 cm. Since circumference/π = diameter: 

21/π = 6.68 cm

We can now plug that into our formula:

[6.68-1.10]/0.012 = 465 cm

So if this coprolite was produced by a crocodile, the animal was approximately 465 cm (or 15 ft) long!

Source: Crocodylian Scatology - A Look into Morphology, Internal Architecture, Inter- and Intraspecific Variation and Prey Remains in Extant Crocodylian Feces by Jesper Milàn