Oldest known lepidosaur? No.

Marke et al 2025 reported,
“The Lepidosauria is the most species-rich group of land-dwelling vertebrates. The group includes around 12,000 species of lizards and snakes (Squamata) and one species of Rhynchocephalia, the tuatara Sphenodon punctatus from New Zealand.”

Unfortunately the authors omit the adjective ‘living’ or ‘extant’.

This omission becomes doubly important because the headline reports, “oldest known lepidosaur”.

Fossil lepidosaurs also include more members of the Rhynchocephalia, drepanosaurs, tanystropheids (including fenestrasaurs and pterosaurs) and extinct Rhynchosauria and their worldwide ancestors including transitional taxa like Trilophosaurus and Azendohsaurus, according to the large reptile tree (LRT, 2337 taxa).

Lepidosauria includes the last common ancestor (LCA) of Iguana and Sphenodon by definition. Let’s look for that LCA. It might turn out to be the oldest known lepidosaur.

“Squamates owe their success to their generally small size, but also to their highly mobile skull that enables them to manipulate large prey.”

Note: Mosasaurs, pythons and azhdarchid pterosaurs are also lepidosaurs.
Some grow to be giants. Many lepidosaurs have mobile skulls. Many do not.

“Here we report a reasonably complete skull and skeleton of a definitive rhynchocephalian from the Middle Triassic (Anisian) Helsby Sandstone Formation of Devon, UK that is around 3–7 million years older than the oldest currently known lepidosaur.”

The authors named their specimen, Agriodontosaurus helsbypetrae.

“The current oldest member of Rhynchocephalia is Wirtembergia from the late Middle Triassic (239–237 million years ago (Ma). The oldest known member of crown Squamata is Cryptovaranoides from the Late Triassic (202 Ma).”

Figure 1. Agriodontosaurus helsbypetrae in situ. ” data-image-caption=”

Figure 1. Agriodontosaurus helsbypetrae in situ.

” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/09/agriodontosaurus_helsbypetrae_insitu588.jpg?w=164″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/09/agriodontosaurus_helsbypetrae_insitu588.jpg?w=559″ class=”size-full wp-image-94437″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/09/agriodontosaurus_helsbypetrae_insitu588.jpg” alt=”Figure 1. Agriodontosaurus helsbypetrae in situ. ” width=”584″ height=”1071″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/09/agriodontosaurus_helsbypetrae_insitu588.jpg?w=584&h=1071 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/09/agriodontosaurus_helsbypetrae_insitu588.jpg?w=82&h=150 82w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/09/agriodontosaurus_helsbypetrae_insitu588.jpg?w=164&h=300 164w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/09/agriodontosaurus_helsbypetrae_insitu588.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />

Figure 1. Agriodontosaurus helsbypetrae in situ.

Meanwhile
in the LRT the last common ancestor of Sphenodon and Iguana, Early Permian Tridentinosaurus, is the most primitive known Lepidosaur. Related Coelurosauravus is from the Late Permian. Lanthanolania is from the Middle Permian. Saurosternon and Lacertulus are from the Late Permian.

Somehow the authors omitted taxa common to the ancestry of Rhynchocephalia and Squamata recovered by the LRT. This omission reflects a simplistic view of phylogeny approved by textbook writer, senior professor and co-author, Mike J Benton.

Figure 2. Cladogram portion from Marke et al 2025. Note the lack of resolution at the base of the Pan-Lepidosauria with some taxa older than Agriodontosaurus. This weakens their headline claims. ” data-image-caption=”

Figure 2. Cladogram portion from Marke et al 2025. Note the lack of resolution at the base of the Pan-Lepidosauria with some taxa older than Agriodontosaurus. This weakens their headline claims.

” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/09/agriodontosaurus.cladogram588.gif?w=300″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/09/agriodontosaurus.cladogram588.gif?w=584″ class=”size-full wp-image-94439″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/09/agriodontosaurus.cladogram588.gif” alt=”Figure 2. Cladogram portion from Marke et al 2025. Note the lack of resolution at the base of the Pan-Lepidosauria with some taxa older than Agriodontosaurus. This weakens their headline claims. ” width=”584″ height=”518″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/09/agriodontosaurus.cladogram588.gif?w=584&h=518 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/09/agriodontosaurus.cladogram588.gif?w=150&h=133 150w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/09/agriodontosaurus.cladogram588.gif?w=300&h=266 300w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/09/agriodontosaurus.cladogram588.gif 588w” sizes=”(max-width: 584px) 100vw, 584px” />

Figure 2. Cladogram portion from Marke et al 2025 their figure 4. Note the lack of resolution at the base of the ‘Pan-Lepidosauria’ with some taxa older than Agriodontosaurus. This weakens their headline claims. The LRT does not recover a ‘Pan-Lepidosauria’, but does recover a ‘Lepidoauria’.

The authors’ figure 1 is a simple cladogram
that includes 12 generic and suprageneric taxa. The LRT includes 2337 generic taxa and several dozen red taxa that are less complete. Figure 4 includes more taxa, but far too few.

Once again taxon exclusion and superlatives in the headline hobble a study published in Nature, which gets less respect every time the authors, editors and referees approve manuscripts like this for publication.

Beware of superlatives like ‘oldest known.‘ Rarely will this be confirmed. The LRT falsified this headline and claim with taxa omitted from the study.

Agriodontosaurus helsbypetra
will be tested in the LRT in the next few days.

References
Marke D et al (7 co-authors including MJ Benton) 2025. The oldest known lepidosaur and origins of lepidosaur feeding adaptations.  Nature. https://doi.org/10.1038/s41586-025-09496-9

https://en.wikipedia.org/wiki/Lepidosauria

Publicity
science.org/content/article/incredible-fossil-reveals-earliest-relative-lizards-and-their-kin

nhm.ac.uk/discover/news/2025/september/newly-found-fossils-lizard-like-animal-oldest-ever-discovered.html

discovermagazine.com/a-242-million-year-old-fossil-has-drastically-altered-the-story-of-lizard-evolution-48013

phys.org/news/2025-09-lizards-ancient-fossil-ancestral-traits.html

bristol.ac.uk/news/2025/september/lizards.html