A new Early Cretaceous lizard in Myanmar amber with exceptionally preserved integument.

We here report on a well-preserved juvenile lizard specimen in Albian amber (ca. 110 mya) from the Hkamti site (Myanmar). This new taxon is represented by an articulated skull and the anterior portion of the trunk, including the pectoral girdle and forelimbs. The scleral ossicles and eyelid are also visible, and the specimen exhibits pristine detail of the integument (of both head and body). In a combined molecular and morphological analysis, it was consistently recovered as a scincoid lizard (Scinciformata), as sister to Tepexisaurus + Xantusiidae. However, the phylogenetic position of the new taxon should be interpreted with caution as the holotype is an immature individual. We explored the possibility of miscoding ontogenetically variable characters by running alternative analyses in which these characters were scored as missing data for our taxon. With the exception of one tree, in which it was sister to Amphisbaenia, the specimen was recovered as a Pan-xantusiid. Moreover, we cannot rule out the possibility that it represents a separate lineage of uncertain phylogenetic position, as it is the case for many Jurassic and Cretaceous taxa. Nonetheless, this fossil offers a rare opportunity to glimpse the external appearance of one group of lizards during the Early Cretaceous.

Surface contrast enhancement of integumentary structures in X-ray tomography.

Micro-computed tomography (µCT) has become standard in the biological sciences to reconstruct, display and analyse 3D models of all kinds of organisms. However, it is often impossible to capture fine details of the surface and the internal anatomy at the same time with sufficient contrast. Here we introduce a new approach for the selective contrast-enhancement of integumentary surface structures. The method relies on conventional and readily available sputter coaters to cover the entire sample with a thin layer of gold atoms. This approach proved successful on a diverse array of plants and animals. On average, we achieved a 14.48-fold gain of surface contrast (ranging from 2.42-fold to 86.93-fold) compared with untreated specimens. Even X-ray-transparent samples such as spider silk became accessible via µCT. This selective contrast-enhancement, makes it possible to digitally reconstruct fine surface structures with low absorbance while the tissue-dependent grey value resolution of the inner anatomy is maintained and remains fully visualisable. The methodology is suited for a broad scientific application across biology and other sciences employing (µ)CT, as well as educative and public outreach purposes.