Marmoretta gets a face lift = synchotron data

As reported here in 2014
“flat-headed rhynchocephalian, Marmoretta nests near the base of that clade [Rhynchocephalia], prior to the fusion of teeth together and to the jaws in many derived taxa, including pleurosaurs.”

Known previously by a skull and mandible drawing (Figs 1, 2). tiny Marmoretta nested in the large reptile tree (LRT, 2338 taxa) among the most basal members of the Rhynchocephalia = Sphenodontia. Only aquatic Megachirella and Pleurosaurus are as primitive.

Now Ford, Benson, Griffiths and Evans 2025 report
on elements of the post-crania revealed by synchotron and X-ray (Fig 1).

When the new data was applied to Marmotta, no taxa moved or shifted despite 29 score changes among 129 tested skull traits.

From the Ford et al abstract:
“Stem lepidosaurs are known from the Early Triassic onwards, but primarily from very incomplete specimens.”

In the LRT several stem lepidosaurs are known from complete skeletons. These include the famous gliding lepidosaurs from the Triassic through Cretaceous. Most of Marmoretta’s closest relatives in the LRT are known from complete skeletons.

“Therefore, we have little information on their ecological diversity or the ecological context of deep evolutionary divergences of Lepidosauria.”

In the LRT the gliding lepidosaur ancestors of Marmoretta are universally considered to be arboreal. Get that phylogeny straight before making statements like that.

“Marmoretta oxoniensis, from the Middle Jurassic of the UK, is one of the most completely known candidate stem lepidosaurs.”

In the LRT Marmoretta is not a candidate stem lepidosaur. It IS a stem lepidosaur.

“Previous studies [see citations below] proposed that it may have been semi-aquatic, based primarily on its abundance in marginal marine rocks. We show here that Marmoretta was adapted for climbing, based on the post-cranial anatomy of a partial skeleton, visualized using micro-computed tomography (µCT)—in particular, the steep angles of thoracic zygapophyses, ungual phalanx morphology and elongate penultimate manual phalanges that curve distoventrally along their lengths.”

All good to know. In the LRT more complete ancestors and relatives help determine partial skeleton taxa niches.

“Linear discriminant analysis of the partial hand, using a training dataset of hand skeleton measurements and habitat use in extant squamates, returns strong evidence for clinging arboreality and Marmoretta clusters among scansorial/arboreal iguanians in manus shape space. Evidence of arboreality in Marmoretta provides the first information about habitat use in a probable stem lepidosaur and illuminates the vertical structure of ecological communities of the mid-Mesozoic.”

The Marmoretta hand = manus is compared here (Fig 3) to the related Pleurosaurus manus. This gracile Marmoretta manus looks like the pes of many lepidosaurs. Key difference: Manual digit 5 has three phalanges. Pedal digit 5 has four phalanges.

Marmoretta oxoniensis
(Evans 1991, Waldman and Evans 1994) Middle/Late Jurassic, ~2.5 cm skull length, originally considered a sister of kuehneosaurs, drepanosaurs and lepidosaurs. Marmoretta was basal to Gephyrosaurus and the rest of the Rhynchochephalia. Two specimens are known with distinct proportions in the skull roof (frontal and parietal, see above).

Phys.org publicity:
“Looking at the scans of the fossil, the team noticed that the hands were not those of an aquatic reptile.Taking advantage of the vertical realm could have been the secret of these animals’ survival,”

The paper is behind a pay wall. So the text was not consulted.

References
Evans SE 1991. A new lizard−like reptile (Diapsida: Lepidosauromorpha) from the Middle Jurassic of Oxfordshire. Zoological Journal of the Linnean Society 103:391-412.
David P. Ford et al, 2025. Evidence for clinging arboreality in a Middle Jurassic stem lepidosaur, Proceedings of the Royal Society B: Biological Sciences. DOI: 10.1098/rspb.2025.0080
Griffiths EF Ford DP, Benson RBJ and Evans SE 2021. New information on the Jurassic lepidosauromorph Marmoretta oxoniensis. Papers in Palaeontology https://doi.org/10.1002/spp2.1400
Waldman M and Evans SE 1994. Lepidosauromorph reptiles from the Middle Jurassic of Skye. Zoological Journal of the Linnean Society 112:135-150.

wiki/Marmoretta
wiki/Colobops

Publicity
Ashworth J 2025. Early British lizard relative among the first known to climb trees. https://phys.org/news/2025-04-early-british-lizard-climb-trees.html

Source: https://pterosaurheresies.wordpress.com/2025/04/19/marmoretta-gets-a-face-lift-synchotron-data/