Behind the missing skull: A unique fin configuration redefines the Jurassic shark † Palaeoscyllium formosum Wagner, 1857 (Neoselachii, Galeomorphi)

The holotype of the type species † Palaeoscyllium formosum Wagner, 1857 from the Jurassic of Europe, lacking the cranial region, is herein carefully re-described and re-evaluated to clarify the taxonomic and nomenclatural status of this taxon. Post-cranial morphological characters identified through direct revision of the holotype are extensively compared with those of morphologically similar fossil and extant sharks, with particular emphasis on species-specific diagnostic traits. The results confirm the taxonomic validity and applicability of both the genus † Palaeoscyllium and its type species. The revaluation of the holotype reveals a distinctive fin configuration not documented in any known living or fossil shark to date. These findings further highlight the remarkable morphological disparity of Jurassic galeomorph sharks, indicating that some fin arrangements present in fossil taxa are absent among extant representatives of the same orders. The study also emphasizes that characters derived from the fossil dermal skeleton should be interpreted cautiously in systematic contexts due to their extensive variability and the potential influence of ecological factors on dermal structures. This study represents an additional step toward clarifying the diversity and evolutionary history of galeomorph sharks during the Jurassic, a crucial interval for their morphological diversification. Future studies reassessing other species and specimens currently referred to † Palaeoscyllium , also exploring additional dental and skeletal characters, are highly desirable. Broader comparative investigations into fin position and configuration across extant and fossil galeomorph sharks are likewise required to better understand the structural variability and evolutionary significance of these life traits over a long temporal scale.