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

Abstract

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.

Compound osteoderms preserved in amber reveal the oldest known skink

“…Molecular and morphological data indicate that skinks are most closely related to girdled lizards (Cordylidae), plated lizards (Gerrhosauridae) and night lizards (Xantusiidae) among extant lizard groups 15 – 19 . Morphological evidence also supports a close relationship of skinks to several fossil lizard groups, including Carusiidae, Globauridae, and Paramacellodidae 20 – 22 .…”

“…Stem Scincoidea 41 , Glyptosaurinae 42 , 43 , Helodermatidae 44 , Shinisauria 45 , and Anguidae 46 , among others), may also be informative. Within Scincoidea, there is a remarkable pattern of distribution of body armor; while osteoderms are common in Scincidae, Cordylidae and Gerrhosauridae, they are absent among Xantusiidae, including some amber embedded lizards with excellent integumentary preservation 22 .…”

35 million-year-old solid-wood-borer beetle larvae support the idea of stressed Eocene amber forests

“…Larger animals are often not fully embedded into the amber as the resin flow was only partly able to cover them (e.g. birds: Xing et al 2017Xing et al , 2019Xing et al , 2020lizards: Daza et al 2016;Čerňanský et al 2022). After the carcass is rotten, this leaves a large cavity in the amber.…”

A new fossil lizard (Reptilia: Squamata) from the Lower Cretaceous of eastern Inner Mongolia, China

“…The presence or absence of a mesosternal fontanelle (formed by the fusion of the mesosternal rods or the formation of a bridging bar) was recently listed as a phylogenetic character (Ch.485) in Gauthier et al (2012) and subsequent updates (e.g. Simões et al, 2018;Čerňanský et al, 2022). Among extant squamates, Russell & Bauer (2008) reported the presence of a mesosternal (or 'xiphisternal') fontanelle in Scincidae, gerrhosaurine cordylids, and Lacertidae, although neither we (in Lacerta viridis, Gallotia atlantica, Gallotia caesaris) nor Gauthier et al 2012 (in Lacerta viridis, Takydromus ocellatus) found the mesosternal rods to be fused in the latter group.…”