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Denazinemys nodosais a Late Cretaceous representative of the North American turtle clade Baenidae diagnosed, among others, by a shell surface texture consisting of raised welts. We provide a detailed description of a partial skeleton from the late Campanian Kaiparowits Formation of Utah, USA, including bone-by-bone analysis of its cranium based on images obtained using micro-computed tomography. A revised phylogenetic analysis confirms placement ofDenazinemys nodosaclose toEubaena cephalicaandBoremysspp. within the clade Eubaeninae. Comparison with a second skull from the Kaiparowits Formation previously assigned toDenazinemys nodosaquestions its referral to this taxon. An assortment of specimens from the Early to Late Campanian of Mexico and the USA had previously been referred toDenazinemys nodosabased on shell surface texture alone, even though this characteristic is known to occur in other baenids. Our review of all available material concludes thatDenazinemys nodosais currently only known from the Late Campanian of New Mexico and Utah.
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This content will become publicly available on June 1, 2026
New monstersaur specimens from the Kaiparowits Formation of Utah reveal unexpected richness of large-bodied lizards in Late Cretaceous North America
Monstersauria (Squamata, Anguimorpha) fossils are present in most Upper Cretaceous sedimentary basins in western North America, but despite almost a century of collection, their record remains extremely fragmentary. Here, we describe new material belonging to large-bodied monstersaurs, including a new taxon,Bolg amondolgen. et sp. nov., based on a fragmentary associated skeleton and co-occurring specimens from the middle unit of the upper Campanian Kaiparowits Formation of Grand Staircase–Escalante National Monument in southern Utah, USA. Phylogenetic analyses recoverB. amondolwithin Monstersauria, with two unique anatomical features: fused osteoderms on the jugal and the presence of autotomy septa on the distal caudal vertebrae. Critically,B. amondolis morphologically distinct from the problematic Late Cretaceous North American monstersaurPalaeosaniwa canadensis, whereas co-occurring monstersaur vertebrae and parietals from the Kaiparowits Formation (cf.P. canadensis) highlight a pressing need for a reassessment of this important, widespread taxon. These results offer new evidence that at least three lineages of distinct, large-bodied monstersaurian lizard were present on the palaeolandmass of Laramidia during the Campanian Stage. Importantly,B. amondolrepresents the most complete squamate recovered from late Campanian southern Laramidia and reveals key anatomical characteristics for future identification of isolated lizard fossil elements.
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- PAR ID:
- 10649608
- Publisher / Repository:
- Royal Society
- Date Published:
- Journal Name:
- Royal Society Open Science
- Volume:
- 12
- Issue:
- 6
- ISSN:
- 2054-5703
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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