Paleontologists have found the remains of a previously unknown species of lizard in a piece of mid-Cretaceous amber excavated in northern Myanmar.
Life reconstruction of Electroscincus zedi; areas of the lizard not represented in the material available are depicted as blurred. Image credit: Stephanie Abramowicz.
The newly-discovered species was a small lizard with an estimated snout-vent length of 3 cm (1.2 inches).
Named Electroscincus zedi, it lived during the mid-Cretaceous period, approximately 99 million years ago.
It differs from all other known squamates (lizards and snakes) from the Mesozoic by the presence of imbricate, compound osteoderms arranged in a staggered pattern around the body, supporting its placement in the skink family Scincidae.
“Scincidae is a megadiverse clade of squamates, which today has attained a near cosmopolitan distribution in temperate and tropical regions worldwide,” said Dr. Juan Daza of Sam Houston State University and his colleagues.
“It is represented by more than 1,745 described living species, comprising nearly 15% of all living lizards.”
“Typical skinks have cylindrical bodies and relatively short limbs and, in over 50 skink lineages, evolutionary transitions towards limb reduction or loss have occurred.”
“Among living scincoids (Xantusiidae, Gerrhosauridae, Cordylidae, Scincidae), members of Scincidae exhibit the greatest range in body length, including some miniaturized forms having a body length of only a few centimeters to the extinct Tiliqua frangens, which may have reached half a meter or more.”
“Skinks also show great variation in the number of presacral vertebrae, ranging from 26 to 108, which, in combination with cycloid scales and compound osteoderms, may have facilitated the repeated evolution of fossorial and limbless morphotypes.”
“Most skinks are characterized by possession of smooth, cycloid scales underlain by compound osteoderms — bony plates in the dermis that are made up of several articulated osteodermites per scale.”
Electroscincus zedi, fossil in ventral (a) and dorsal (b) views; detail of the right foot (c, e) and osteoderms (d); X-ray of the whole specimen showing the skeletal remains, and several articulated and scattered osteoderms (f). Image credit: Daza et al., doi: 10.1038/s41598-024-66451-w.
A piece of Burmese amber (Burmite) that preserves Electroscincus zedi was found in the mid-Cretaceous outcrops in the Myitkyina district, Kachin province, northern Myanmar, approximately 100 km west of the town of Myitkyina.
The specimen includes two disconnected parts of the skink, containing the scales and mostly appendicular bones, but is clearly part of a single individual.
“Currently over 100 specimens of squamates are known from Burmite,” the paleontologists said.
“In this large sample, this new fossil is the only one that preserves this osteodermal morphology which makes it diagnosable to the Scincidae, and differentiates it from all known fossil squamates from the Cretaceous.”
“The specimen is incomplete, but it does retain both postcranial skeletal elements and integumentary structures and, though less than ideal, it provides a basis for comparison with any putative scincid material that might be found in the future.”
“The specimen has a combination of compound osteoderms and overlapping cycloid scales that is limited to skinks.”
“We propose that this type of osteoderm evolved as a response to an increased overlap of scales, and to reduced stiffness of the dermal armor,” the researchers concluded.
Their paper was published in the journal Scientific Reports.
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J.D. Daza et al. 2024. Compound osteoderms preserved in amber reveal the oldest known skink. Sci Rep 14, 15662; doi: 10.1038/s41598-024-66451-w