Integrative taxonomy in action: a new genus of phyllobothriid tapeworms (Cestoda: Phyllobothriidea), with insights on potential transmission pathways and influences of environmental gradients on diversity patterns of the group.

This article focuses on the taxonomic reassessment and detailed redescription of *Phyllobothrium sinuosiceps* Williams, 1959, a tapeworm parasite of the bluntnose sixgill shark (*Hexanchus griseus*). Using molecular phylogenetic analyses based on 28S ribosomal DNA sequences and ultrastructural examination via scanning electron microscopy, the study establishes a new genus, *Carrassoniella* gen. nov., with *Carrassoniella sinuosiceps* comb. nov. as its sole species. The parasite is characterized by a unique combination of morphological features, including a spherical, foliose scolex with uniloculate, crenulated bothridia and distinctive microtriches, and it infects deep-sea cowsharks primarily in the northeastern Atlantic and Mediterranean Sea. The research also situates *Carrassoniella* within the order Phyllobothriidea, highlighting its evolutionary relationships and ecological association with deep-sea environments, and provides a conservation assessment classifying the species as Near Threatened due to its host’s status.