A new extremely tiny pre-snake: Barlochersaurus

Just out,
Daza et al.. 2018 describe a privately-owned, Mid-Cretaceous, teeny-tiny, ‘enigmatic’ lizard preserved in amber, Barlochersaurus winhtini (Figs. 1, 3; 1.5 in total length). The authors report, “The fossil is one of the smallest and most complete Cretaceous lizards ever found, preserving both the articulated skeleton and remains of the muscular system and other soft tissues. Despite its completeness, its state of preservation obscures important diagnostic features.We determined its taxonomic allocation using two approaches: we used previously identified autapomorphies of squamates that were observable in the fossil; and we included the fossil in a large squamate morphological data set.”FIgure 1. From Daza et al. 2018 and color overlays applied here. FIgure 1. From Daza et al. 2018 and color overlays applied here.

FIgure 1. From Daza et al. 2018 and color overlays applied here.Phylogenetically the authors report,
“Results from the phylogenetic analysis places the fossil in one of four positions: as sister taxon of either Shinisaurus crocodilurus or Parasaniwa wyomingensis, at the root of Varanoidea, or in a polytomy with Varanoidea and a fossorial group retrieved in a previous assessment of squamate relationships.”

Figure 2. Subset of the LRT showing stem snakes, snakes and their sister group, the geckos.

Figure 2. Subset of the LRT showing stem snakes, snakes and their sister group, the geckos.

Unfortunately this lack of resolution is due to taxon exclusion.
In the large reptile tree (LRT, 1318 taxa; subset Fig. 2) Barlochersaurus nests between the stem snakes Pontosaurus (Fig. 5) and tiny Tetrapodophis (Figs. 3, 4) neither of which is listed in the text of the Daza et al. paper.

Figure 3. Tetrapodophis and Barlochersaurus at full scale when seen on a monitor at 72 dpi.

Figure 3. Tetrapodophis and Barlochersaurus at full scale when seen on a monitor at 72 dpi.

According to Wikipedia
“Anguimorpha include the anguids (alligator lizardsglass lizardsgalliwasps and legless lizards)They are characterized by being heavily armored with non-overlapping scales, and almost all having well-developed ventrolateral folds (excluding Anguis). Anguidae members can, however, be somewhat difficult to identify in their family, as members can be limbed or limbless, and can be both viviparous and oviparous.” The LRT tests several anguids. They do not attract Barlochersaurus as well as Tetrapodophis and Pontosaurus.

Figure 4. The skull of Tetrapodophis, the proximal outgroup taxon to living snakes.

Figure 4. The skull of Tetrapodophis, the proximal outgroup taxon to living snakes.

Pontosaurus
(Fig. 5) has a longer tail and is much larger overall. The manus and pes of Pontosaurus are similar in proportion and detail to those of Barlochersaurus.

Figure 2. Pontosaurus and its parts. Data from Caldwell 2006. This is one of the last taxa we know in the snake lineage that still had a pectoral girdle.

Figure 2. Pontosaurus and its parts. Data from Caldwell 2006. This is one of the last taxa we know in the snake lineage that still had a pectoral girdle.

The Daza team printed 3D replicas,
blown up to 10 times the original size. These are publicly available at Florida’s Museum of Natural History and Harvard’s Museum of Comparative Zoology.

Earlier
we looked at a more primitive pre-snake with legs (JKZ-Bu267) also found in amber here.

And, oh, yeah… did I forget to mention?
Phylogenetic miniaturization at the genesis of major and minor clades in the LRT strikes again! This time, to the extreme!

References
Daza JD, Bauer AM, Stanley EL, Bolet A, Dickson B and Losos JB 2018. A enigmatic miniaturized and attenuate whole lizard from the Mid-Cretaceous amber of Myanmar. Breviora 563: 18pp.

https://www.pbs.org/wgbh/nova/article/paperclip-lizard/

3 thoughts on “A new extremely tiny pre-snake: Barlochersaurus

  1. I think taxon sampling is not the solely cause of this discrepancy, the specimen offers very limited information (large number of missing information). At the fast rate of recovery of burrito specimens, I wouldn’t be surprise if better specimens would pop up and this would offer new insights. For the time brain I would treat this post with caution.

  2. I think taxon sampling is not the solely cause of this discrepancy, the specimen offers very limited information (large number of missing information). At the fast rate of recovery of Burmese amber specimens, I wouldn’t be surprise[d] if better specimens would pop up and this would offer new insights. For the time being I would treat this post with caution.

    • Glass snakes were the option suggested by the authors. I wish they had included Pontosaurus and Tetrapodophis in their analysis to eliminate that possibility. Convergence is strong in these unrelated ultimately legless clades.

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