Rhaeticosaurus

Rhaeticosaurus is anchored by holotype LWL-MFN P 64047 from a specific Rhaetian Exter Formation bed at Bonenburg; this secure specimen does not establish an exact global plesiosaur or genus origin.

Rhaeticosaurus mertensi is a new small-bodied plesiosaurian recovered within Plesiosauria as a basal Pliosauridae member in the published 35-taxon, 270-character analysis; that placement is matrix-dependent rather than direct ancestry.

The Rhaeticosaurus holotype comes from clay pit #3 of the Lücking brick company, 1 km north of Bonenburg in Warburg, North Rhine-Westphalia, Germany, in Rhaetian dark marine mudstones of the Exter Formation; this is a locality record, not a complete distribution.

Holotype LWL-MFN P 64047 is a partial articulated subadult skeleton preserving the occiput, lower jaw, vertebral column, girdles and left limbs; its diagnosis includes ventrally concave V-shaped cervical neurocentral sutures and foreshortened zeugopodials.

Rhaeticosaurus preserves four similar pointed flippers and a short tail consistent with plesiosaurian hydrofoil and paraxial-locomotion comparisons, while histological growth and physiological implications remain interpretations rather than directly measured behaviour or metabolism.