Cephalopoda Cuvier, 1797

Arnold, Sam, Nos, David, Sáez-Liante, Raquel & Fernández-Álvarez, Fernando Á., 2025, Diversity in the squid family Ancistrocheiridae and description of a new family of the order Oegopsida (Cephalopoda), Zoological Journal of the Linnean Society 204 (3) : -

Class Cephalopoda Cuvier, 1797

Subclass Coleoidea Bather, 1888

Superorder Decapodiformes Haeckel, 1866

Order Oegopsida d’Orbigny, 1845 in Férussac and d’Orbigny, 1834 –48

Family Mobydickidae fam. nov. Arnold and Fernández-Álvarez

Diagnosis: Oegopsida without photophores and with chromatophore pattern reduced to a small area over the ventral and dorsal area surrounding each eye; arms equal in length with 50+ hooks, arms I–III with distinct circular horny rings with one large main cusp and one accessory claw on each side, arm IV with circular horny rings with a thicker area where the main cusp is found in the suckers from other arms; gladius very pronounced and angular, with a long rachis; lower beak broad with a large wing gap; shallow connection between the rachidian teeth and the lateral cusp.

Remarks: The morphology of the specimen NHM 20240079 superficially resembles that of Ancistrocheirus as it is a large squid with long fins, tentacles as a subadult or adult, and hooks in the arms. However, it differs from any member of the superfamily Enoploteuthoidea by the absence of any known photophore. The morphology of the horny rings from the central part of arms I–III does not resemble any known from any other known family of oceanic squids. Also, the beak morphology is very different from the very characteristic morphology of Ancistrocheirus spp .. This specimen is also the largest depigmented squid species to the best of our knowledge. We decided to erect the new family for the following reasons: (i) we were not able to find any described family in which this squid could fit; (ii) including it in Ancistrocheiridae would imply radically modifying the diagnosis of the family in one of its most diagnostic characters: the presence of symmetrically arranged photophores; and (iii) we have no guarantee that this specimen is the sister-group of Ancistrocheirus . If it actually is its sister-group, it would not create any taxonomic problem, as the families Ancistrocheuridae and Enoploteuthidae Pfeffer, 1900 are known to be sister-groups ( Fernández-Álvarez et al. 2022), and adding another family as a sister of Ancistrocheuridae would not have any further nomenclatural or taxonomic consequence. However, if this squid is added to Ancistrocheiridae , its diagnosis is modified to fit this species in, and later it is discovered that it is not a member of this group, it would create taxonomic instability.