A fossil found in limestone along a remote South Texas riverbed could be that of a dolphin-like reptile that swam in oceans 90 million years ago, according to paleontologists.

The discovery was made two years ago by petroleum geologist James Harcourt, who works for the Texas Railroad Commission, which regulates the state's oil and gas industry. It went largely unnoticed until a photo of the fossil appeared on the cover of the commission's 2016 annual report.

The find is unique because it appears to be a nearly complete fossil of an ichthyosaur, which grew to 1.8 meters long and had the sleek body of a dolphin and long, toothy jaws of a dinosaur, the Houston Chronicle reports.