Snakes in the Cretaceous Period

There are many different types of snakes found today. People don´t often stop to think about where snakes came from or how they have evolved into the creatures they currently are. The Cretaceous Period was a crucial time for the evolution of snakes. Snake fossils from this period have confirmed and rejected various theories about their evolution.

  1. Earliest Snakes Found

    • The earliest snakes are believed to have evolved during the Cretaceous Period. They include Pachydrachis, Pachyophis, Lapparentophis defrenni, Similiophis, Pouitella, Pachyrahachis problematicus, Eupodophis and Haasiophis. Most of the snake fossils, from about 96 to 100 million years ago, were all found scattered in different places in the Middle East.

    Sea Theory

    • For most of the 20th century, scientists believed that snakes evolved from land lizards, but towards the end of the century many snake fossils were found in marine deposits, so some scientists said that snakes evolved from marine lizards. This theory was mainly supported by the discovery of the Eupodophis, Pachyrhachis, Haasiophis terrasanctus, which were found to have two hind legs, complete with a femur, tibia and fibula bones.

    Land Theory

    • When the fossil Najash rionegrina was discovered in Argentina in 2003, the sea theory was overturned. This snake from the Cretaceous period had limbs and hips proving that it could not have lived in the sea. The fossil had a well-defined sacrum supporting a pelvis and functional hind legs outside of its ribcage. It was found in a terrestrial deposit. The new theory was that snakes evolved on land, eventually losing their limbs as they became soil burrowers.

    Modern Theory

    • It is hard to find fossil evidence of the evolution of snakes, because the vertebrae do not fossilize easily. Many scientists still go back and forth between the sea theory and the land theory. After the discovery of Najash, more marine fossil deposits were found off the coast of Israel and a new theory arose that snakes evolved from the now extinct marine lizards, monosaurs that lost their limbs in the oceans and seas. This theory was ruled out with a recent DNA study that found that monitors, which are direct descendants of monosaurs, are not related to snakes. The study found that snakes evolved on land. Despite varying beliefs, most scientists today can´t deny the crucial evidence of the Najash snake of the Cretaceous period. Most paleontologists agree that snakes evolved from a burrowing terrestrial lizard.