Bipedal Cretaceous lizard tracks

These are the oldest lizard tracks in the world…
(if you don’t consider Rotodactylus (Early Triassic) strictly a ‘lizard’ (= squamate). One rotodactylid trackmaker, Cosesaurus, is a tiny lepidosaur).
Figure 1. Bipedal lizard tracks from South Korea in situ.

Figure 1. Bipedal lizard tracks from South Korea in situ. They are tiny.

From the abstract
“Four heteropod lizard trackways discovered in the Hasandong Formation (Aptian-early Albian), South Korea assigned to Sauripes hadongensis, n. ichnogen., n. ichnosp., which represents the oldest lizard tracks in the world. Most tracks are pes tracks that are very small. The pes tracks show “typical” lizard morphology as having curved digit imprints that progressively increase in length from digits I to IV, a smaller digit V that is separated from the other digits by a large interdigital angle. The manus track shows a different morphology from the pes. The predominant pes tracks, the long stride length of pes, narrow trackway width, digitigrade manus and pes prints, and anteriorly oriented long axis of the fourth pedal digit indicate that these trackways were made by lizards running bipedally, suggesting that bipedality was possible early in lizard evolution.”
Actually, the lizard was not running.
Typically in running tracks the prints are very far apart and these tracks are sometimes left toe to right heel.
Figure 2. Original and new tracings of the bipedal lizard tracks from South Korea. PILs are added,

Figure 2. Original and new tracings of the bipedal lizard tracks from South Korea. PILs are added. Manual digit 4 and 5 appear to have shifted.

 The authors did not venture who made the tracks.
They reported, “based on the palaeobiogeographic distribution of facultative extant families, the lizard that produced S. hadongensis tracks could well have been a member of an extinct family or stem members of Iguania, which was present in the Early Cretaceous.”
Actually the closest match among tested taxa
is with Eichstaettisaurus (Fig. 1), a basal member in the lineage of snakes. And this clade is close to the origin of geckos. ReptileEvolutiion.com and the large reptile tree would have been good resources for the authors to use. Lots of lizard pedes were illustrated and scored there.
Figure 3. Originally pictured as a generic lizard (below), here Eichstattsaurus scaled to the track size walks upright.

Figure 3. Originally imagined  as a generic lizard (below), here Eichstattsaurus matched and scaled to the track size walks upright.

 Based on a phylogenetic analysis of the tracks
the closest match in the LRT is with Eichstaettisaurus, so a slightly larger relative made them. Distinct from the skeletal taxon, the trackmaker had a longer p2.1 than 2.1 and pedal digit 1 was quite short. Otherwise a good match in all other regards.
So why walk bipedally?
It was walking, not running, so escape from predation can be ruled out. Elevating the upper torso and head, like a cobra, can be intimidating to rivals, or just offer a better view over local plant life. This sort of flexibility could have helped them get into the trees and then to move to higher branches.
References
Lee H-J, Lee Y-N, Fiorillo AR &  LÃ J-C 2018. Lizards ran bipedally 110 million years ago. Scientific Reports 8: 2617. doi:10.1038/s41598-018-20809-z

Tracing fossil photos goes mainstream in 2014

DGS is going mainstream
A new paper by Chiappe et al. 2014, forsakes time honored and inaccurate pencil tracings with a camera lucida (basically a prism) and goes straight to the camera, scanner and mouse in their portrayal of the new Hongshanornis specimen. This is a great example of DGS or digital graphic segregation.

Figure 1. From Chiappe et al. 2014 showing the fossil (at right) and the digital tracing (at left).

Figure 1. From Chiappe et al. 2014 showing the fossil (at right) and the digital tracing (at left). Here’s a professional paleontologist using a technique for which I was once and continue to be derided.

There is value in this technique, even when the bones are mere impressions, and the soft tissue is ephemeral, as they appear here. (Figs. 1, 2). The technique is especially helpful in two-dimensional crushed fossils, like Hongshanornis.

Figure 2. The two images of Hongshanornis superimposed to show the exactness this tracing technique produces, plus color, plus enlargements, etc. etc.

Figure 2. The two images of Hongshanornis superimposed to show the exactness this tracing technique produces, plus color, plus enlargements, etc. etc.

Many were the times
when I tried to match a published drawing with a published photo and found I had to warp or distort one or the other to make them match. A long lens from a distance at right angles to the plane of the specimen minimizes distortion and key-stoning (perspective problems). This photography technique combined with scanning such a photo and tracing it on screen with a mouse makes that problem go away.

The next step, of course, is to use the digital tracings to create a very accurate reconstruction.

References
Chiappe L, Bo Z, O’Connor J, Chunling G, Xuri W, Habib M, Marguan-Lobon J, Qingjin M and  Xiaodong C 2014. A new specimen of the Early Cretaceous birdHongshanornis longicresta: insights into the aerodynamics and diet of a basal ornithuromorphPeerJ. 2:e234; DOI 10.7717/peerj.234

wiki/Hongshanornis