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. 2025 Jun 18;12(6):250435. doi: 10.1098/rsos.250435

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© 2025 The Authors.

Published by the Royal Society under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/4.0/, which permits unrestricted use, provided the original author and source are credited.

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Line drawings comparing parietal morphology among Late Cretaceous and Modern monstersaurs — Line drawings comparing parietal morphology among Late Cretaceous and Modern monstersaurs. (A–D) Campanian monstersaur specimens, denoted by black border. (A) Monstersaur parietals from the upper Campanian Kaiparowits Formation (Fm) in dorsal (top) and ventral (bottom) views. (B) Dorsal view of the parietal from specimen MOR 792 (referred to Palaeosaniwa canadensis) from the Campanian Two Medicine Fm, modified from Balsai [8] and Hamilton et al. [30]. (C) Dorsal (top) and ventral (bottom) views of specimen TMP 1985.058.058 (Helodermatidae indet.) from the upper Campanian Oldman Fm, modified from Gao & Fox [7]. (D) Described monstersaur parietals from the Campanian Djadokhta/Baruungoyot formations. Left: Parietal from the holotype specimen IGM 3/14 of Estesia mongoliensis in dorsal (top) and ventral (bottom) views, modified from Norell et al. [5]. Right: dorsal views of parietals referred to Gobiderma pulchrum. Top: ZPAL MgR III/64 (holotype), modified from Conrad et al. [12]; middle: ZPAL MgR III/66, modified from Conrad et al. [12]; bottom: IGM 3/59, modified from Conrad et al. [12]. (E) Parietal UALVP 33385 from the Maastrichtian Scollard Fm, referred to Paraderma bogerti, in dorsal (top) and ventral (bottom) views. Modified from Gao & Fox [7]. (F) Parietal OMNH 27022 referred to Primaderma nessovi from the Cenomanian Mussentuchit Member, Cedar Mountain Fm, in dorsal (top) and ventral (bottom) views. Modified from Nydam [10]. (G) Parietal of UF 153328 (Heloderma horridum) in dorsal (top) and ventral (bottom) views. Anatomical abbreviations: am, adductor musculature attachment; fps, frontoparietal suture; pfos, parietal fossa; pfrm, parietal foramen.