Research News
CT skeleton: Computed tomography image of the skeleton of the lizard Cryptolacerta hassiaca found in the Messel Pit. This technology allowed the scientists to investigate in detail internal anatomic structures not visible to the naked eye. Photo: MfN/Helmholtz-Zentrum Berlin
More information:
Fossil Lizard Revealed as Amphisbaenia Ancestor
The evolutionary genesis of snakes is one of the big riddles of evolution biology. Whereas genetic examination points towards a relationship to iguanas and monitor lizards, snake anatomy more likely indicates a joint origin with other reptiles featuring snake-like body shapes. Hot contestors are in particular the so-called worm lizards or Amphisbaenians, which at first glance look like earthworms with scales. A burrowing species, they mostly inhabite the tropical soils of Africa and South America. Yet which hypothesis is the right one?
The Discovery: A 47-million-year-old Fossil
The discovery of a small, 47-million-year-old fossil lizard in the Messel Pit near Darmstadt in Germany has now provided the first anatomical proof of the origins of Amphisbaenians. According to this fossil evidence, they are not related to snakes but to the so-called Lacerta genus of lizards, a member of which is also our domestic sand lizard. The small fossil, which the researchers named Cryptolacerta hassiaca ("hidden lizard from Hesse") belongs to the collection of the Senckenberg Research Institute and Natural Science Museum in Frankfurt am Main.
Lizard Amphisbaenian Ancestor
"This fossil conclusively refutes the hypothesis that snakes are related to other burrowing reptiles and have lost their limbs as well as lengthened their body in one joint evolutionary step", says Johannes Müller, scientist at the Natural Science Museum and professor at the Humboldt University Berlin. The researchers around Johannes Müller and doctoral candidate Christy Hipsley examined the fossil by way of a micro computed tomography device rendering visible in high resolution even the smallest structures inside the skeleton. In a next step, they combined the anatomic data with genetic information from modern lizards and snakes. Their results reveal that the shape of the head of Cryptolacerta consitutes an original variant of the capsule-like head adapted for burrowing that is characteristic of Amphisbaenians and that both species are most closely related to lizards of the genus Lacerta. Conversely, the closest relatives of snakes are species such as the present-day monitor lizard.
