I have calibrated this fish from the image. Vern caught this fish in Rio ***** and at the time we both thought the fish was close to 2 feet long. The fish was measured at 23.5 SL, later I modified it to 23.5 TL as I did not think Vern measured it right and put the wrong length markings. A Piranha Fury member a month or so ago used a technique similar to the type I used to check out that S. rhombeus size. He used Vern's middle finger as a guide to size using his own finger length to approximate the length. Since I have the actual jaw of the fish here at OPEFE, it was easy for me to measure it (2 inches TL) against the photo and where the jaw is situated. Knowing anatomy helps.From this I subtracted a 1/4 inch from the jaw to allow for the snout length (these are approximation without having fish in front of me). I then calibrated 1 3/4 inches as a starter for length using the jaw marker minus the 1/4 inch. Then began to mark each line for 1 3/4. Below you can see the results. This photo is not the best to use for finding exact measurements, but it is interesting nonetheless to approximate a size.