Simoniteuthis michaelyi, Fuchs & Weis & Thuy, 2024

Fuchs, Dirk, Weis, Robert & Thuy, Ben, 2024, SimoniteUthiS, a new vampyromorph coleoid with prey in its arms from the Early Jurassic of Luxembourg, Swiss Journal of Palaeontology (6) 143 (1), pp. 1-10 : 3-6

Simoniteuthis michaelyi n. sp.

Figures 2–3

Holotype: MNHNL TI024 , consisting of slab and counter-slab.

Type locality: Bascharage, Industrial Zone Edward Steichen ( Fig. 1 ; formerly “Bommelscheier”) ( Henrotay et al., 1998; Szwedo et al., 2017).

Type horizon: Near-continuous level of bituminous finely laminated carbonate nodules rich in insect and teleost remains, approximately 90 cm above the base of the bituminous black shale succession; Lower Toarcian, Serpentinum Chronozone, Exaratum Subchronozone.

Derivation of name: Dedicated to Patrick Michaely, Director of the Natural History Museum Luxembourg with a passion for palaeontological research.

Description: The holotype exhibits structures of the gladius as well as the head–arm complex. The latter is only visible on the slab ( Figs. 2A–D, 2G , 3A, B ); the counter-slab is unfortunately missing the head–arm complex ( Figs. 2E, F , 3D, E ). The head–arm complex of the slab is represented by proximal and middle parts of the arms, eyeballs, and the above-mentioned bony fish ( Fig. 2C, D ). UV-light reveals scarce remains of the arm musculature ( Fig. 2D ). The arm tips are obviously not conserved in the concretion. One can count eight arms; evidence of a rudimentary (filamentous) fifth arm pair does not exist. Further details such as suckers or arm length are not determinable. The two fishes are situated between two greyish eyeballs and obviously take the former position of the buccal mass.

Leaked ink unfortunately hampers the reconstruction of the gladius. The preserved length of the gladius measures 23 cm ( Fig. 3A–E ). Only 1–2 cm of the conus part is missing as can be assessed by well-developed diverging inner asymptotes. The maximum width of the lateral fields reaches 8.2 cm suggesting a moderately wide gladius (gladius widthmax- to-gladius length = 0.33). Taking into account a certain degree of dorsoventral compaction the overall width was slightly less. Apart from this issue, parts of the lateral field are poorly visible. In particular, their anterior extensions are hidden behind mantle musculature and thus complicate interpretations. Outer asymptotes (opening angle c.15°) as well as growth increments suggest that the transition from the parabolar lateral field to the hyperbolar zone is sharp (pointed) and distinctly projected. The hyperbolar zone is accordingly V-shaped and deeply incised. The hyperbolar zone takes 21 cm of the total median field length (ratio of the hyperbolar zone length to total gladius length = 0.86), which is categorized as very long. Where the hyperbolar zone joins the median field, the latter is 4.3 cm wide. This is simultaneously the widest part of the median field; anteriorly, its width is decreasing. The ratio median field width at anterior end of the hyperbolar zone to hyperbolar zone length of 0.21 suggests a slender to very slender opening angle of the median field of 11–12°. The lateral margins of the median field (adjacent to the hyperbolar zones) are plate-like reinforced. Anteriorly, these diverging reinforcements reach a maximum width of 0.9 cm and are slightly shorter than the anterior gladius margin. The shape of the latter, particularly the transition from lateral reinforcements to central median field is problematic due to the lack of informative growth increments ( Fig. 3C ). Anteriorly, the lateral reinforcements appear parabolar (?and projected; Fig. 3A–C ) suggesting a second zone of hyperbolar growth lines intercalated between the parabolar reinforcements and parabolar central median field. Such a “secondary hyperbolar zone” is very unusual and a series of anteriorly parabolar structures imprinted in the leaked ink (?remains of growth structures) alternatively imply an evenly convex anterior gladius margin ( Fig. 3B ). The median field bears a median line, but is insufficiently preserved for a detailed description. A median keel is certainly absent.

Comparisons: The cluster analysis ( Fig. 4A ) of the gladius outline exposes Vampyrofugiens atramentum Rowe et al., 2023 from the Callovian of La Voulte-sur-Rhône to be most similar to Simoniteuthis michaelyi n. gen. n. sp. However, the gladius of this deep-sea vampyromorph is based solely on a tomographic outline reconstruction and thus still poorly understood.

Besides, the gladius shape of Simoniteuthis michaelyi n. gen. n. sp. is most similar to contemporary geopeltid ( Geopeltis simplex , Parabelopeltis flexuosa ) and loligosepiid vampyromorphs ( Loligosepia aalensis , Jeletzkyteuthis coriaceus ). The distinctly forward-projected lateral fields combined with the deeply incised V-shaped hyperbolar zones are typical for loligosepiids, although the relative length of the hyperbolar zones is slightly shorter in Simoniteuthis michaelyi n. gen. n. sp. than in loligosepiids. In geopeltids, the hyperbolar zone is shorter than in Simoniteuthis michaelyi n. gen. n. sp. and evenly arcuated (rather than sharply recurved).

The plate-like lateral reinforcements as described for Simoniteuthis michaelyi n. gen. n. sp. are unusual for loligosepiids, but known from Geopeltis simplex , Leptotheuthis gigas and Paraplesioteuthis sagittata ( Fig. 4B ). The latter is a contemporary taxon and belongs to the prototeuthid clade owing to the absence of a hyperbolar zone. Tithonian Leptotheuthis gigas differs from Simoniteuthis michaelyi n. gen. n. sp. through a wider median field and a constriction of the lateral fields in the posterior third of the gladius.

Figures

Fig. 2 Simoniteuthis michaelyi n. gen. n. sp., holotype (MNHNL TI024), Lower Toarcian, Serpentinum Chronozone, Exaratum Subchronozone, Bascharage.A–D slab; E–G counter-slab. A overview; B camera lucida drawing of A; C close-up of the head–arm complex; D same under UV-light showing the weakly illuminating arm musculature; E overview; F close-up of the preyed fishes, red colour Specimen 1 (op=opercle; sop =subopercle),blue colour Specimen 2 (caud= caudal fin; sop =subopercle; centra =central vertebra); G same under UV-light. Scale bars =10 mm

Fig. 3 Gladius morphology of Simoniteuthis michaelyi n. gen. n. sp., holotype (MNHNL TI024), Lower Toarcian,Serpentinum Chronozone, Exaratum Subchronozone, Bascharage. A overview of the slab; B close-up of the anterior hyperbolar zone showing the course of growth increments; C schematic morphology and measurements; D overview of the counter-slab;E close-up of the posterior gladius showing the course of growth increments. Scale bars=10 mm

Fig. 1 Detailed map of the Edward Steichen Industrial Zone, northeast of the town of Bascharage in southwest Luxembourg.The area marked by a black asterisk corresponds to the place of finding (© Carte topographique: Adm. Du Cadastre et de la Topographie,Luxembourg)

Fig. 4 Comparative gladius morphology of selected octobrachiate coleoids.A Topology of the cluster analysis based on gladius outlines; B 3-reconstructions of the same gladiuses systematically sorted (after Fuchs, 2020). Where known arm configurations are indicated. Note the gladius outline of Vampyrofugies (based on Rowe et al., 2023) is approximated