biostudies-literatureUnknown10Madzia D<i>Ischyrodon meriani</i> is an obscure pliosaurid taxon established upon an exceptionally large tooth crown of a probable Callovian (Middle Jurassic) age that originates from Wölflinswil, Canton of Aargau, Switzerland. Despite being known for almost two centuries, the specimen remains poorly researched. Historically, <i>I. meriani</i> has been associated, or even considered conspecific, with <i>Pliosaurus macromerus</i> and <i>Liopleurodon ferox</i>. However, neither of the two hypotheses have been tested through detailed comparisons or using modern quantitative methods. Here, we redescribe the type of <i>Ischyrodon meriani</i>, illustrate it, and compare to teeth of thalassophonean pliosaurids, with special focus on Jurassic representatives of the clade. Multivariate analyses show close similarities to <i>L. ferox</i> but comparable structures to those of <i>I. meriani</i>, including a distinctive pattern of the apicobasal ridges, are also observable in some mid-Cretaceous brachauchenines from the '<i>Polyptychodon</i>' assemblage of East and South East England. While it is likely that <i>I. meriani</i> represents a <i>Liopleurodon</i>-like taxon, or is indeed conspecific with <i>L. ferox</i>, which would make <i>I. meriani</i> the proper name for the species, any such taxonomic considerations are hindered by the fragmentary nature of the type specimens of both these taxa as well as limited knowledge of the dental variability within and between individual jaws of <i>L. ferox</i>. Currently, <i>I. meriani</i> is best treated as a <i>nomen dubium</i>. Finally, we discuss the potential implications of <i>I. meriani</i> being conspecific with <i>L. ferox</i>, and additionally provide a commentary on the taxonomic status of <i>Liopleurodon</i>.PeerJe13244https://www.ebi.ac.uk/biostudies/studies/S-EPMC8995022biostudies-literatureHistorical significance and taxonomic status of <i>Ischyrodon meriani</i> (Pliosauridae) from the Middle Jurassic of Switzerland.PMC8995022Klug CMadzia DSachs SfalseHistorical significance and taxonomic status of <i>Ischyrodon meriani</i> (Pliosauridae) from the Middle Jurassic of Switzerland.<i>Ischyrodon meriani</i> is an obscure pliosaurid taxon established upon an exceptionally large tooth crown of a probable Callovian (Middle Jurassic) age that originates from Wölflinswil, Canton of Aargau, Switzerland. Despite being known for almost two centuries, the specimen remains poorly researched. Historically, <i>I. meriani</i> has been associated, or even considered conspecific, with <i>Pliosaurus macromerus</i> and <i>Liopleurodon ferox</i>. However, neither of the two hypotheses have been tested through detailed comparisons or using modern quantitative methods. Here, we redescribe the type of <i>Ischyrodon meriani</i>, illustrate it, and compare to teeth of thalassophonean pliosaurids, with special focus on Jurassic representatives of the clade. Multivariate analyses show close similarities to <i>L. ferox</i> but comparable structures to those of <i>I. meriani</i>, including a distinctive pattern of the apicobasal ridges, are also observable in some mid-Cretaceous brachauchenines from the '<i>Polyptychodon</i>' assemblage of East and South East England. While it is likely that <i>I. meriani</i> represents a <i>Liopleurodon</i>-like taxon, or is indeed conspecific with <i>L. ferox</i>, which would make <i>I. meriani</i> the proper name for the species, any such taxonomic considerations are hindered by the fragmentary nature of the type specimens of both these taxa as well as limited knowledge of the dental variability within and between individual jaws of <i>L. ferox</i>. Currently, <i>I. meriani</i> is best treated as a <i>nomen dubium</i>. Finally, we discuss the potential implications of <i>I. meriani</i> being conspecific with <i>L. ferox</i>, and additionally provide a commentary on the taxonomic status of <i>Liopleurodon</i>.2022-01-01T00:00:00Z20222026-06-03T10:26:35.924Z2026-05-29T03:06:18.499ZS-EPMC89950223541501810.7717/peerj.13244