Believe it or not, massive sea creatures once lived in the Sahara

Fossils showing the teeth of an ancient lungfish

(CNN)It sounds like the twist in a sci-fi movie or an abandoned plotline on "Lost," but new research reveals some of the largest (and probably scariest*) sea creatures lived in what is now the Sahara Desert.

The paper, published in the Bulletin of the American Museum of Natural History, details an ancient body of water called the Trans-Sarahan Seaway, which covered parts of Western Africa 100 million to 50 million years ago.
For two decades, scientists examined fossils and sediment in present-day Mali to form an accurate picture of what this prehistoric environment looked like. They concluded the body of water was warm and shallow and, less pleasantly, was home to five-foot-long catfish and 40-foot-long sea snakes.
Ancient Malian catfish specimens and their estimated sizes. The largest catfish was estimated to be 160cm in length, or about 5.2 feet.
"The ancient Malian ecosystem had numerous apex predators including Crocodyliformes, Serpentes, and Amiidae, some of which were among the largest species in their clades," the paper reads. (A clade is a group of organisms thought to have evolved from the same ancestor.)
    In plain English, that's crocodile-like animals, snakes and ugly fish; all of them designed to kill.

    Why they were so big

    How did they get so big? The Trans-Saharan Seaway ran north-to-south from what is now Algeria to what is now Nigeria. That means it was isolated from larger bodies of water during long periods of its existence.
    According to the paper, this kind of isolation may have limited predators and ensured resources were always available, which is a perfect recipe for a species to grow unchecked.
    "The Trans-Saharan Seaway exhibited intermittent isolation from major seas," the paper reads. "This environmental variable may have created aquatic centers of endemism, stimulating selection for gigantism as previously observed for species on terrestrial islands."
    Endemism is when a species is confined to a specific area.
      The Sahara has obviously come a long way from the nightmare aquarium it once was. In 2014, climate simulations concluded the arid Sahara we know today was formed about seven million years ago when a shift in tectonic plates closed off the region from the surrounding seas.
      *To be clear, all prehistoric sea creatures were scary.