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Newtonsaurus

Evans et al., 2025 NYOO-ton-SOR-us Disputed

From 'Newton' (honoring British paleontologist Edwin Tully Newton, 1840-1930, of the Geological Survey, who first described the holotype) and Greek 'sauros' (lizard).

205.7–201.4 million years ago Rhaetian, Late Triassic
Late Triassic stages

Newtonsaurus is an extinct genus of large neotheropod dinosaur from the Rhaetian (Late Triassic) Cotham Member of the Lilstock Formation, Penarth Group, recovered at Stormy Down near Bridgend in South Wales. The single species, Newtonsaurus cambrensis, is known from a natural mold of a left dentary preserved as two blocks of sandstone (basionym 'Zanclodon' cambrensis Newton 1899); Evans, Howells, Wintle and Benton (2025) re-evaluated the holotype and erected the new genus, recovering the taxon tentatively as a coelophysoid with morphological affinity to Dilophosaurus, although a stem-averostran position cannot be excluded. The estimated body length of 5-7 m, derived from a ~28 cm preserved dentary representing roughly half the mandible, makes Newtonsaurus a candidate for the largest known Late Triassic theropod. The genus name had been used as a nomen nudum in private compilations since 1999 and is formally established by this paper.

Under dispute

Newtonsaurus cambrensis was revalidated as a distinct neotheropod, tentatively a coelophysoid, by Evans and colleagues (2025), who reject earlier megalosauroid referrals; Jones (2026) still treats it as a nomen dubium.

Diagnosis

  1. Anterior tip of dentary modestly expanded but not bulbous, forming a low dorsal convexity with its apex at the third tooth position.
  2. 16-17 dentary alveoli present, with the third (second as preserved) alveolus distinctly enlarged and subcircular in outline.
  3. Lateral foramina along the labial groove anteroposteriorly elongated (elliptical, ~1.5 cm long) rather than circular.
  4. Single Meckelian foramen at the anterior terminus of the Meckelian groove, level with the third alveolus.
  5. Unfused, sub-pentagonal interdental plates separated from the medial dentary wall by a narrow paradental groove open for its entire length.
  6. Relative mandible depth (depth/length ratio ~17.8%) intermediate between that of shallow coelophysoid forms and deeper-jawed forms.

Species

Newtonsaurus cambrensis Evans et al., 2025 Disputed

Type species

From Latin 'cambrensis' (of Cambria, an old name for Wales), referring to the South Wales provenance of the holotype.

Holotype
GSM 6532 , British Geological Survey
Material
Natural mold of a left dentary preserved on two blocks of sandstone (medial and lateral surfaces), ~28 cm long, retaining 16-17 alveoli, 7 fully erupted teeth, interdental plates, the Meckelian fossa, and neurovascular foramina.
Horizon
Cotham Member, Lilstock Formation, Rhaetian, Late Triassic , 205.7–201.4 million years ago
Locality
Stormy Down, near Bridgend, Bridgend, United Kingdom

References

  1. Evans, O.; Howells, C.; Wintle, N.; Benton, M. J. (2025). Re-assessment of a large archosaur dentary from the Late Triassic of South Wales, United Kingdom. Proceedings of the Geologists' Association 101142. Elsevier. doi:10.1016/j.pgeola.2025.101142

    Re-evaluates the holotype dentary GSM 6532 (basionym 'Zanclodon' cambrensis Newton 1899); erects Newtonsaurus as a new genus and formalizes a name that had been a nomen nudum since 1999.

    evans2025a
  2. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Theropods. Princeton University Press.

    Lists Newtonsaurus as an informally named, dubious taxon.

    jones2026c
  3. Rauhut, O. W. M.; Hungerbühler, A. (2000). A review of European Triassic theropods. Gaia 15: 75-88.

    Finds no derived characters allowing a diagnosis of "Zanclodon" cambrensis and regards it as a nomen dubium.

    rauhut2000a