The origin of squamates revealed by a Middle Triassic lizard from the Italian Alps

CT anatomy of the only known Megachirella specimen PZO 628 was scored in a combined morphology–molecule analysis that recovered it on the squamate stem; the same model's divergence estimates are not fossil observations or crown-Squamata FADs.

The Lepidosauria navigation envelope uses the approximately 240 Ma Megachirella specimen and its tested stem-squamate placement as the older evidence anchor and living lepidosaurs at 0 Ma as the younger edge; this does not make Megachirella a direct ancestor or establish a global lepidosaur first appearance or divergence time.

Pan-Squamata is a navigation route spanning sampled stem and crown squamates; the Megachirella analysis recovers one fossil on the squamate stem but does not identify a direct ancestor, crown FAD or complete route duration.

Megachirella provides a Middle Triassic Pan-Squamata stem sample, not a crown-Squamata first appearance; the former 201.4 Ma–present crown display is therefore withheld.

Megachirella PZO 628 provides a roughly 240 Ma Middle Triassic Pan-Squamata stem anchor; a 240 Ma–present route is shown without treating the specimen as a direct ancestor or crown-Squamata FAD.

The cited analyses place Megachirella on the squamate stem, Taytalura as an early-diverging stem lepidosauromorph, and Bellairsia on the squamate stem; these placements are sampled analytical results and do not resolve every lepidosaur relationship.

The profile's named lepidosaur samples come from the Middle Triassic Italian Alps (Megachirella), Late Triassic Ischigualasto Formation of Argentina (Taytalura), and the Middle Jurassic Kilmaluag Formation of Skye, Scotland (Bellairsia specimen NMS G.2022.1.1); these occurrences do not establish a global lepidosaur distribution.

High-resolution imaging exposes complementary early lepidosaur anatomy: Megachirella contributes cranial, wrist and shoulder characters, Taytalura preserves a three-dimensionally exposed CT-resolved skull, and Bellairsia provides synchrotron-resolved stem-lizard anatomy.

The cited Megachirella, Taytalura and Bellairsia studies provide locality, anatomy and phylogenetic analyses but do not establish a single Lepidosauria diet, habitat, locomotor mode, body-size distribution or ecological guild; those fields remain explicitly unassigned here.