Trachyteuthis teudopsiformis, Fuchs & Engeser & Keupp, 2007

Fuchs, Dirk, Engeser, Theo & Keupp, Helmut, 2007, Gladius shape variation in coleoid cephalopod Trachyteuthis from the Upper Jurassic Nusplingen and Solnhofen Plattenkalks, Acta Palaeontologica Polonica 52 (3), pp. 575-589 : 584-585

publication ID	https://doi.org/ 10.5281/zenodo.13748968
persistent identifier	https://treatment.plazi.org/id/630D066F-D234-F55F-FFE8-03AA79ABE1F7
treatment provided by	Felipe
scientific name	Trachyteuthis teudopsiformis
status	sp. nov.

Treatment

Trachyteuthis teudopsiformis sp. nov.

Fig. 6 View Fig .

2006 Trachyteuthis (Teudopsis) spec.; Fuchs 2006a: 52, pl. 14: E.

Derivation of the name: The species name refers to the close similarity to the Toarcian vampyropod genus Teudopsis Eudes−Deslongchamps, 1835 .

Holotype: G 1306061; nearly complete gladius of an adolescent individual.

Paratype: MB. C 1002.4 (part) and PIMUZ 17826 (counterpart); fragmentary gladius of an adult individual.

Type locality: quarry Bérger, Blumenberg near Eichstätt (Southern Germany).

Type horizon: Solnhofen Plattenkalks, Lower Tithonian, Malm zeta 2–3, Hybonoticeras hybonotum Zone.

Material —G 1306061, MB.C 1002.4, PIMUZ 17826.

Diagnosis.—Gladius median field with a pronounced median keel. Granulation narrow, posteriorly restricted to the keel. Anterior gladius end sharply pointed.

Trachyteuthis teudopsiformis can be easily distinguished from other species of this genus by the possession of a Teudopsis −like prominent median keel, a comparatively narrow granulated area and a distinctly pointed anterior end ( Table 1 View Table 1 ). Adult Tr. teudopsiformis has possibly longer hyperbolar zones compared to Tr. hastiformis or Tr. nusplingensis (juvenile representatives are extremely rare). The extraordinary clarity of growth lines might be a diagenetical artefact. If not, it is a further characteristical feature of Tr. teudopsiformis , because generally growth increments in Tr. hastiformis and Tr. nusplingensis are weakly developed.

Description of the holotype.—The gladius, which is seen in dorsal aspect, has a preserved length of 70 mm ( Table 1 View Table 1 , Fig. 6A View Fig ). It is in an excellent condition except for the missing anterior part.

The most characteristic feature is the existence of a pronounced median keel, which increases in thickness from posterior to anterior. Most anteriorally it seems that the keel is flattened. A preservational interruption in the posterior third of the keel shows that the keel is solid ( Fig. 6A View Fig 3 View Fig ).

Another obvious character is the posterior granulation, which is restricted to the keel ( Fig. 6A View Fig 3 View Fig ). In the anterior half, the granulated area suddenly broadens ( Fig. 6A View Fig 2 View Fig ). Granules are coarse but regularly arranged in arcuated rows indicating a distinctly pointed anterior rim. As the total gladius length is uncertain and both hyberbolar zones and lateral fields are strongly flattened, determination of ratios is problematic. Although this specimen represents just an adolescent individual, we chose it for holotype, because gladius characters are best shown. Soft tissues are not preserved.

Description of the paratype.—The paratype ( Fig. 6B, C View Fig ) consists of part and counterpart ( MB.C 1002.4 + PIMUZ 17826). Owing to the typical “Sockelerhaltung” in the Solnhofen Plattenkalks, MB.C 1002.4, the better preserved specimen ( Fig. 6B View Fig 1 View Fig ), can be determined as the upper slab. Hence, the gladius was embedded ventrally with the dorsal side above. As upper (outer, dorsal) gladius laminae adhere to MB.C 1002.4 and lower (inner, ventral) laminae to PIMUZ 17826 neither the dorsal gladius surface nor the ventral gladius surface are visible. However, in a few small places, where gladius material is missing, several imprints of granules are present in MB.C 1002.4 ( Fig. 6B View Fig 2 View Fig ). The gladius was partially compacted. In spite of this, both slabs display a Teudopsis −like median keel constantly increasing in width from posterior to anterior.

In contrast to both lateral fields and the left (anatomic right, due to the ventral view) hyperbolar zone, which are not preserved, preservation of the right (anatomic left) hyperbolar zone enables at least length measurements.

As lateral fields are missing, the maximum gladius width and the overall shape of the posterior gladius end remains uncertain, but a more or less obtuse end can be presumed. Although outer margins of the anterior top are fragmentary, dorsal imprints indicate a distinctly pointed anterior end. Extraordinarily preserved growth increments clearly confirm this assumption and even enable the gladius outline of earlier ontogenetic stages to be determined. Significant differences between ontogenetic younger and older stages can be found. At a gladius length of 70 mm the hyperbolar zone accounts for approximately 33% of the total gladius length. In ontogenetic older stages, e.g., at a gladius length of 180 mm, the same ratio increases up to 45%. This allometric mode of growth found in Trachyteuthis teudopsiformis is surprising because the gladii of plesioteuthids from Solnhofen grow isometrically (own observations).

As in the holotype, soft tissues are not preserved in the paratype.

Other possible examples of Trachyteuthis teudopsiformis .— At least one poorly preserved specimen from the Solnhofen region and previously studied by Naef (1922: fig. 52) also offer a distinct median keel in combination with anteriorly pointed growth lines. Naef (1922) reconstructed the fins by means of two different specimens; among them the specimen of Crick (1896: pl. 14). We re−investigated the other specimen ( SOS 1425) and found weak evidence of a median keel ( Fig. 7A, B View Fig ). We are aware that identification of this specimen as Tr. teudopsiformis is only tentative due to a poorly preserved gladius.

Stratigraphic and geographic range.—Known only from the type locality.