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| Electroscincus zedi Daza, Stanley, Heinicke, Leah, Doucet, Fenner, Arias, Smith, Peretti, Aung & Bauer, 2024 |
Abstract
Scincidae is one of the most species-rich and cosmopolitan clades of squamate reptiles. Abundant disarticulated fossil material has also been attributed to this group, however, no complete pre-Cenozoic crown-scincid specimens have been found. A specimen in Burmite (99 MYA) is the first fossil that can be unambiguously referred to this clade. Our analyses place it as nested within extant skinks, supported by the presence of compound osteoderms formed by articulated small ostedermites. The specimen has a combination of dorsal and ventral 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 armour. Compound osteoderms could be a key innovation that facilitated diversification in this megadiverse family.
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| 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). Scale bar applies to the entire amber piece. |
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| Electroscincus zedi, pectoral and pelvic girdle in ventral view (a, b). Numbers indicate digit number. |
Systematic Paleontology.
Squamata Oppel, 1811.
Scincoidea Oppel, 1811.
Scincidae Gray, 1825.
Electroscincus zedi, gen. et sp. nov.
Diagnosis:
A small lizard with an estimated snout vent length (SVL) of 30 mm. Electroscincus zedi differs from all other known squamates from the Mesozoic by the presence of imbricate, compound osteoderms arranged in a staggered pattern around the body, supporting its placement in Scincidae (Figs. 2, 3). Its inclusion within Scincidae is also supported by its possession of cycloid scales around the body28 overlying compound osteoderms (in some Cordyliformes compound osteoderms are present in scales of the ventral surface only49,50). The osteoderms are very different from rectangular and imbricated paramacellodid osteoderms.
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Holotype: Peretti Museum Foundation/ GRS GemResearch Swisslab AG (GRS-Ref-51036).
Type locality. Specimen comes from mid-Cretaceous (Late Albian/early Cenomanian) outcrops in the Myitkyina District, Hukawng Valley, Kachin Province, northern Myanmar, approximately 100 km west of the town of Myitkyina. Precise location of these mines, history of excavations, and stratigraphy of the Burmese amber deposits are summarized elsewhere51.
Etymology. The generic name is a combination of the Latin word for amber (electrum) and skink (scincus). The species epithet zedi refers to the bell-shaped stupas that house relics at Burmese Buddhist temples, referencing the smooth-sided amber housing the fossil remains, while also honoring David Temple, Curator of Paleontology at the Houston Museum of Natural Sciences (HMNS), for his contributions to palaeontology and public awareness of Burmite fossils (including the social conflict associated with its mining in Myanmar) by developing the exhibit “Amber Secrets, Feathers from the Age of Dinosaurs”.
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| Life reconstruction of Electroscincus zedi. Areas of the lizard not represented in the material available are depicted as blurred. Illustration by Stephanie Abramowicz. |
Juan D. Daza, Edward L. Stanley, Matthew P. Heinicke, Chuck Leah, Daniel S. Doucet, Kelsey L. Fenner, J. Salvador Arias, Ru D. A. Smith, Adolf M. Peretti, Nyi Nyi Aung and Aaron M. Bauer. 2024. Compound Osteoderms preserved in Amber reveal the Oldest Known Skink. Scientific Reports. 14, 15662. DOI: 10.1038/s41598-024-66451-w
