Data from: New information on the Jurassic lepidosauromorph Marmoretta oxoniensis

The earliest known crown-group lepidosaurs are known from the Middle
Triassic, however their stem group is poorly sampled, with only a few
representative fossils found. This is partly due to the small size and
delicate bones of early stem-lepidosaurs (=lepidosauromorphs) which make
both preservation in the fossil record and subsequent discovery less
likely. The mid Jurassic lepidosauromorph Marmoretta oxoniensis Evans 1991
is re-examined using high-resolution µCT scanning to reveal parts of the
skull anatomy that were previously unknown. These include a squamosal,
postorbital, more complete parietal, pterygoids, and an articulated
posterior section of the mandible. Some differences between this and other
Marmoretta specimens were identified as a result, such as the arrangement
of palatal teeth and the shape of the parabasisphenoid. The status of
Marmoretta as a stem lepidosaur or stem squamate has been debated. To
evaluate this, we tested the phylogenetic position of Marmoretta by
including our new data in an adapted phylogenetic character matrix. We
recover Marmoretta as a stem-lepidosauromorph and sister to Fraxinisaura
rozynekae. Our findings support the hypothesis that both taxa belonged to
a clade of non-lepidosaur lepidosauromorphs that co-existed with
lepidosaurs into the Middle Jurassic.