|Reconstruction of Tetrapodophis.|
In 2015, Martill et al. described Tetrapodophis amplectus, a fossil snake with four legs. Tetrapodophis was found in the Bürgermeister-Müller-Museum,
a natural history museum in Solnhofen, Germany, while
students were on a field trip to the museum.
The Brazilian fossil was part of an exhibit on the Cretaceous and estimated
to be 110 million years old. The fossil was part of a larger exhibition on
The snake, was 20 cm from head to
toe, although it may have grown much larger. The head is the size of an adult
fingernail, and the smallest tail bone is only a quarter of a millimeter long.
But the most remarkable thing about it is the presence of four limbs each
ending in digits. The front legs are about 1cm long. The back legs are slightly
longer and the feet are larger than the hands. The authors hypothesized that
they may have been used to grasp prey or mates. The fossil Tetrapodophis
apparently had food in its guts when it was
preserved, the remains appeared to be from a salamander.
The authors considered Tetraphodophis
a snake, not a lizard
because of the elongated body; the tooth implantation, the direction of the
teeth, and the pattern of the teeth and the bones of the lower jaw are all
snake-like. The fossil also suggests a single row of ventral scales.
In the same issue of Science,
Evans (2015) notes that snakelike bodies evolved at least 26 times in squamates
and that body elongation is always correlated with limb reduction and that the
forelimbs are usually lost first. She also observed that the threshold body
length at which limb reduction begins is about 70 body vertebrae (or precaudal
remarkable in having about 160 precaudal vertebrae and retaining its anterior
limbs. Evans also notes Tetrapodophis
is like lizards in having distinct vertebral regions of the vertebral column. It has 10 or 11 short-ribbed neck vertebrae
adjacent to the tiny forelimbs. Some generalized terrestrial lizards and a neck
of about this same length. Thus, as in long-bodied lizards, elongation of the
snake skeleton occurred in the trunk region and not the neck. If Tetrapodophis
is indeed a stem-snake, then
body elongation preceded loss of the forelimbs.
In second look at the fossil by Lee
(2016) suggests Tetrapodophis
may not, in fact be a
snake at all. Instead they suggest it may be a dolichosaurid, a Cretaceous
four-legged marine lizard with an elongated, snake-like body.
characters that would be expected in a snake, including re-curved teeth. Lee and
colleagues reevaluated the ecomorphology of this fossil using a multivariate
morphometric analysis and reexamination of the limb anatomy. Their analysis suggests
that the body proportions are unusual and similar to both burrowing and
surface-active squamates. They also show it exhibits enlarged first metapodials
and reduced tarsal-carpal ossification. These traits imply Tetrapodophis
Unfortunately, the fossil is
privately owned and after Lee’s team took photos and measurements, the specimen
was removed from the museum so that it can no longer be studied.
Evans S. 2016.
Four legs too many? Science. 349(6246):374-5.
Palci A, Jones ME, Caldwell MW, Holmes JD, Reisz RR. 2016. Aquatic adaptations in
the four limbs of the snake-like reptile Tetrapodophis from the Lower
Cretaceous of Brazil. Cretaceous Research. 30, 66:194-199.
Tischlinger H. Longrich NR 2015. A four-legged snake from the Early Cretaceous
of Gondwana. Science, 349(6246): 416-419.