Dental plate histology of †Ischyodus dolloi (Chondrichthyes, Holocephali), from Antarctica

• DOI: 10.1111/joa.14257
• Publication Date: 2025-04-19T10:51:01Z
• Authors: Ignacio Cerda; Soledad Gouiric C...; Marcelo A. Reguero
• Keywords: Chondrichthyes; Histology

Abstract In contrast to other cartilaginous fishes (Chondrichthyes), the dentition of Holocephali consists six dental plates, four in upper jaw (two vomerines and two palatines) lower (mandibulars). While microstructure holocephalan has been extensively studied extant species, similar analyses fossil taxa are less common. Here, we provide a detailed description interpretation microanatomy histology plates extinct taxon † Ischyodus dolloi Leriche (Chimaeriformes: ‘Edaphodontidae’). The study is based on palatine mandibular from Eocene Antarctic Peninsula. Our main objectives were (1) identify presence distribution different tissues; (2) analyze morphological diversity hypermineralized structures (i.e., tritors) within plates; (3) compare I. with living holocephalans; (4) infer sequence mode tissue formation plates. composed an outer shell enclosing framework trabecular dentine, which dentine whitlockin) deposited form tritors. Trabecular becomes compacted by centripetal deposition circumvascular around vascular canals. tritors exhibit types: tritoral rods (first report for ‘Edaphodontidae’) pads. Additionally, distinct tissue, term ‘parallelitubular dentine’, formed aboral symphyseal regions. Regarding growth identified developmental pattern full complete compaction follows mesial‐to‐lingual, oral‐to‐aboral, labial‐to‐symphyseal sequence. This aligns spatial order dentinal tissues progressively removed due feeding‐related wear.