Proteroctopus ribeti Fischer & Riou, 1982

Proteroctopus ribeti Fischer & Riou, 1982

( Fig. 8 View Fig )

Specimen MNHN.F. R03801 , holotype of Fischer and Riou, (1982) .

Stratigraphy Koenigi Zone, early Callovian, Middle Jurassic.

Locality La Voulte-sur-Rhône, Ardèche, France.

Description of arm crown Like Vampyronassa , the holotype of P. ribeti is extremely well preserved, showing detail rarely seen in other coleoid fossils. Te holotype measures about 120 mm in length with a 68 mm long mantle ( Kruta et al., 2016: p. 2, Fig. 8a View Fig ). Fins are clearly visible. Te head is rather short with big eyes, though neither reveal a lot of anatomical detail. By contrast, the arm crown is complete and shows suckers and internal anatomical details. In fig. 1F of Kruta et al. (2016) and in Fig. 8b, c View Fig , the axial nerve cords are evident in the tomographic image. At an arm diameter of about 2.5 mm, the axial nerve is about 0.5 mm wide.

Vampyronassa rhodanica Fischer & Riou, 2002 ( Fig. 9 View Fig )

Specimen MNHN.F.B74244, paratype of Fischer and Riou (2002)

Stratigraphy Koenigi Zone, early Callovian, Middle Jurassic.

Locality La Voulte-sur-Rhône, Ardèche, France.

Description of arm crown MNHN.F.B74244 has undergone some rotation and compaction prior to fossilization, though many of the original soft tissues are preserved in 3D (Rowe et al., 2022). Te overall length (posterior-most tip of the mantle to the distal tip of the dorsal arms) of the specimen measures approximately 97 mm. Tere is no evidence that V. rhodanica possessed an ink sac. Te head, which is fused to the mantle, preserves both eyes. Teir position and subspherical shape (about 5–7 mm in diameter) likely reflect the compaction of the specimen.

Eight arms are visible in the arm crown ( Fig. 9 View Fig ). Te preserved length of the two dorsal arms is about 43 to 51 mm. Tis is approximately equivalent in length to the mantle (about 46 mm). Te configuration of the armature on the dorsal arms comprises two distally positioned uniserial suckers, flanked by biserial cirri. Te suckers are about 2 mm in diameter.

Te six non-dorsal arms are shorter and their preserved length ranges from 24 to 36 mm. Up to ten uniserial suckers are visible per arm, and range in diameter from 1.6 mm (proximally) to 0.8 mm (distally). Tese are continuous along the length. Biserial cirri flank these suckers. Tey have a similar diameter and same tapering pattern as the suckers.

Te axial nerves of each of the arms are visible in the PPC-SRµCT slices Fig. 9b, c View Fig . Tey are most prominent in the dorsal arms where, in the distal half of the arm, they range in diameter from about 0.2–0.6 mm. Te width of the arms in this section varies from 1.6 to 2.9 mm. In the non-dorsal arms, the axial nerve size range is 0.3–0.7 mm and the arm width varies between 1.4 and 2.4 mm. It should be noted that the compression of the soft tissue prior to fossilization has likely altered the preserved diameter of these elements.

Te suckers of V. infernalis are radially symmetrical, and each has a conical, Vampyroteuthis -like attachment. Tere is no clear attachment to the internal arm musculature.