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

Andrej Čerňanský,Joseph J Bevitt,Aaron M Bauer,Nyi Nyi Aung,Arnau Bolet,Juan D Daza,J Salvador Arias,Adolf M Peretti,Edward L Stanley,Susan E Evans,Marta Vidal-García

doi:10.1038/s41598-022-05735-5

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.

Highlights

We here report on a well-preserved juvenile lizard specimen in Albian amber from the Hkamti site (Myanmar)
Squamates have a history estimated to date back over 200 million years[4,5,6,7]. Their early Mesozoic record remains limited, but their Cretaceous fossil record has been improving, especially in the last few decades. This Cretaceous record is heavily biased toward northern continents; far less is known of the Mesozoic squamate record in Gondwana, leaving many aspects of the evolutionary history and palaeobiogeography of lizards uncertain
Cenomanian terrestrial lizard fossils are represented by disarticulated and isolated e lements[19,20,21,22,23,24,25], whereas Myanmar amber is famous for the extraordinary preservation of articulated fossils with preserved integument, many of these are limited to isolated limbs and/or tails[12]

Summary

Introduction

We here report on a well-preserved juvenile lizard specimen in Albian amber (ca. 110 mya) from the Hkamti site (Myanmar). The amber mines of Katchin State, northern Myanmar form a series of deposits dated from ~ 110 Ma (Hkamti amber; i.e., the “new mine”) to ~ 72 Ma (Tilin site, see Xing and Qiu[8]; Nyunt et al.9), whereas specimens from elsewhere in the Hukawng valley (for the map of the localities, see Supplementary Data 1) are dated to 99 Ma10 These amber deposits have yielded a significant number of mostly early Cenomanian squamates as inclusions, including some exquisitely preserved lizards[11,12,13,14,15,16,17] and s nakes[18]. In this paper we describe the specimen in detail using high-resolution X-ray microcomputed tomography (synchrotron data), and discuss the possible affinities of the new taxon

Methods

Findings

Discussion

Conclusion