Belemnotheutis antiquus Pearce, 1842

Klug, Christian, Hoffmann, René, Tischlinger, Helmut, Fuchs, Dirk, Pohle, Alexander, Rowe, Alison, Rouget, Isabelle & Kruta, Isabelle, 2023, ‘ Arm brains’ (axial nerves) of Jurassic coleoids and the evolution of coleoid neuroanatomy, Swiss Journal of Palaeontology (22) 142 (1), pp. 1-22 : 5

Belemnotheutis antiquus Pearce, 1842

( Fig. 4 )

Specimen NHMUK 25966, Natural History Museum, London; original of, e.g., Owen, (1844) and Pearce, (1847).

Stratigraphy Oxford Clay, Athleta Zone, upper Callovian, Localit y Christian Malford, Wiltshire, United Kingdom.

Description of arm crown Tis specimen is included for its excellent preservation and historical importance. It is also remarkable because it tells a story of the classical conflict between collectors and well-informed laypersons on the one hand (such as the amateur palaeontologists Mary Anning, who first discovered belemnotheutid materials in 1826, and Joseph Pearce, who introduced the genus and species in 1842) and professionals on the other hand, sometimes arrogant like Richard Owen, (1844) in this context, or correct such as Gideon Mantell, (1848). See Donovan and Crane, (1992) for a detailed historical report and description of the taxon.

Te specimen is about 243 mm long. It is complete and preserves the phragmocone (72 mm long) with the proostracum, which is largely covered by the phosphatized mantle musculature (81 mm long and 48 mm wide in its flattened state). Te head region is also phosphatized but is poor in anatomical detail. Te centre displays a 10 mm wide crescent-shaped structure, which is tentatively interpreted as part of the jaw. Te arm crown is very well preserved and shows the remains of at least seven arms with more than 240 distinct arm hooks, ranging between 1 mm (proximally and distally) and 5 mm (about 20–30 mm from the tips) in length, showing the previously mentioned shape change. Each double row of arm hooks is accompanied by an elongate phosphatized structure, which is 1–5 mm wide. It is unclear whether these structures represent the complete arms or parts thereof. Since it is a historic specimen, it is conceivable that parts of arm width were lost due to preparation efforts (for a photo see Clements et al., 2017).

Figures

Fig. 4 Belemnotheutis antiquus Pearce, 1847; NHMUK 25966,Christian Malford,Wiltshire, England, Callovian Oxford Clay; entire animal with excellently preserved mantle and complete arm crown. Drawing after the holotype, refigured in Clements et al. (2017)