Simoniteuthis michaelyi, Fuchs & Weis & Thuy, 2024
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publication ID |
https://doi.org/ 10.1186/s13358-024-00303-y |
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persistent identifier |
https://treatment.plazi.org/id/03BAB207-EC37-EC3A-FCC7-66757990816E |
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treatment provided by |
Felipe |
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scientific name |
Simoniteuthis michaelyi |
| status |
sp. nov. |
Simoniteuthis michaelyi n. sp.
Holotype: MNHNL TI024 , consisting of slab and counter-slab.
Type locality: Bascharage, Industrial Zone Edward Steichen ( Fig. 1 View Fig ; 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: Te holotype exhibits structures of the gladius as well as the head–arm complex. Te latter is only visible on the slab ( Figs. 2A–D, 2G View Fig , 3A, B View Fig ); the counter-slab is unfortunately missing the head–arm complex ( Figs. 2E, F View Fig , 3D, E View Fig ). Te 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 View Fig ). UV-light reveals scarce remains of the arm musculature ( Fig. 2D View Fig ). Te 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. Te 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. Te preserved length of the gladius measures 23 cm ( Fig. 3A–E View Fig ). Only 1–2 cm of the conus part is missing as can be assessed by well-developed diverging inner asymptotes. Te 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. Te hyperbolar zone is accordingly V-shaped and deeply incised. Te 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. Tis is simultaneously the widest part of the median field; anteriorly, its width is decreasing. Te 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°. Te 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. Te 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 View Fig ). Anteriorly, the lateral reinforcements appear parabolar (?and projected; Fig. 3A–C View Fig ) 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 View Fig ). Te median field bears a median line, but is insufficiently preserved for a detailed description. A median keel is certainly absent.
Comparisons: Te cluster analysis ( Fig. 4A View Fig ) 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 ). Te 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).
Te 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 View Fig ). Te 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.
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