Plagiosaurinae

Plagiosaurinae indet.

Figs. 17 View Fig , 18 View Fig .

Material.— WMNM P97470, an almost complete right parietal; WMNM P97554, a partial right lateral process of an interclavicles; both from clay pit #III of the August Lücking GmbH & Co. KG, northwest of the village of Bonenburg, North Rhine-Westphalia, Germany; Bone Bed 2a, Contorta Beds of the Exter Formation, Rhaetian, Triassic.

Description.— WMNM P97470 ( Fig. 17 View Fig ; SOM 1: fig. 10): an almost complete right parietal. The specimen is dorsoventrally flattened and is relatively narrow in the anterior region, while it is mediolaterally enlarged in the central and posterior regions. The bone is slightly thicker on the medial edge, corresponding to the margin of the pineal foramen ( Fig. 17A View Fig 1 View Fig ). The anterolateral margin of the parietal is concave and does not show any signs of damage, indicating that it is a natural anatomical edge, probably the border of the orbit. The other edges of the bone are all fracture surfaces. While the visceral surface of the bone is smooth, the external one is ornamented. The ornamentation is characterized by pustules arranged in radial lines from the center of the bone. In some areas, pustules are fused together, forming thin radial ridges.

WMNM P97554 ( Fig. 18 View Fig ; SOM 1: fig. 11): a portion of the right lateral process of the interclavicle, as it is partially ornamented and partially covered with faint striations on the ventral side ( Fig. 18A View Fig 1 View Fig ; SOM 1: fig. 11). On the dorsal side it also shows the thickened ridge ( Gee and Sidor 2022) typical of the lateral processes ( Fig. 18A View Fig 2 View Fig ).

Remarks.—The type of ornamentation seen in WMNM P97470, with pustules sometimes arranged in thin radial ridges, is characteristic of most plagiosaurids. More specifically, the ornamentation of WMNM P97470 is very similar to that of Plagiosaurinae , since it does not show polygonal pits and anastomosing ridges, which is the case for Plagiosterninae ( Jaekel 1914; Hellrung 2003; Jenkins et al. 2008). Given this similarity of the ornamentation with Plagiosaurinae ( Shishkin 1986), the specimen is assigned to this group. Since the specimen shows a natural edge in the anterolateral region ( Fig. 17 View Fig ), the parietal contributed to the border of the orbit. In their redescription of Plagiosaurus depressus Jaekel, 1914 , Witzmann and Schoch (2024) recognized that the postfrontal was independently lost in this plagiosaurine, enabling the parietal to contribute to the orbital margin. On the contrary, in the other known plagiosaurine, Gerrothorax pulcherrimus (Fraas, 1913) , the parietal is excluded from the orbital margin due to the presence of the postfrontal ( Hellrung 2003; Schoch and Witzmann 2012). Therefore, WMNM P97470 might be a parietal of Plagiosaurus depressus or a form more closely related to it than to Gerrothorax , but we prefer to be cautious and assign it only to Plagiosaurinae indet. due to the absence of other diagnostic fossils.

The ornamentation seen in WMNM P97554, with pustules arranged in radial ridges or scattered randomly, corresponds to Plagiosaurinae and differs from the one of Plagiosterninae, in which pustules are only present at the junctions of ridges bordering polygonal pits ( Shishkin 1973, 1987; see also Witzmann et al. 2010; Schoch et al. 2014). Given the fact that the interclavicle fragment lacks further diagnostic characters, it is assigned to Plagiosaurinae indet.