Wyoming's Rarest Dinosaur: Only One Ever Found, Almost Lost

The only Alcovasaurus fossil ever discovered has survived an incredible journey: 146 million years underground, a museum flood, and over a century of scientific debate.

Fossil hunter William Harlow Reed found the unique stegosaur near Wyoming's Alcova Reservoir in 1908 after abandoning his original dig site due to too many rattlesnakes. He and partner A.C. Dart spent that summer carefully excavating 42 vertebrae, several ribs, a pelvis, one femur, and four remarkably long tail spines stretching over 3 feet each.

Those tail spines caught everyone's attention immediately. They were much longer than any known Stegosaurus spikes, suggesting this might be something entirely new.

Reed sent plaster casts to paleontologist Charles Gilmore at the Smithsonian, who named it Stegosaurus longispinus in 1914. The fossils went on display at the University of Wyoming Geological Museum, which housed the second largest collection of American Jurassic fossils in the world at the time.

Then disaster struck in the late 1920s. An overhead water pipe burst, flooding the exhibit hall with water and steam that seeped into the ancient bones and reduced nearly all of them to rubble.

The same element that preserved these bones for millions of years destroyed them in minutes. Only the femur and two plaster casts of the tail spikes survived.

Why This Inspires

Despite the devastating loss, scientists never gave up on Alcovasaurus. Graduate student Julian Hernandez Diepenbrock and regional paleontologist Brent Breithaupt continue studying the remaining femur and casts, using modern technology to unlock secrets from limited evidence.

Their dedication paid off. In recent years, paleontologists determined Alcovasaurus wasn't just a species of Stegosaurus but an entirely new genus with unique characteristics no other stegosaur possesses.

Museums worldwide hold dozens of well-preserved Stegosaurus specimens, making Alcovasaurus infinitely more rare and scientifically valuable. Paleontologists across the American West keep searching for a second specimen, and each new discovery in the Morrison Formation brings fresh hope.

The story reminds us that even fragments can hold enormous value. Scientists continue learning from that single femur, proving that persistence and curiosity can extract meaning from the smallest remnants of the past.

Somewhere in Wyoming's ancient rocks, another Alcovasaurus might be waiting to be found.