Trachyteuthis nusplingensis, 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 : 583-584

Trachyteuthis . nusplingensis sp. nov.

Fig. 5 .

1846 “without appellation”; Münster 1846: pl. 9, 2.

2005 Trachyteuthis hastiformis Rüppell 1829 ; Klug et al. 2005: 179, figs. 6A, G, 7B, D, 13A.

2006 Trachyteuthis ? spec.; Fuchs 2006a: 52, pl. 14: D.

Derivation of the name: After the village of Nusplingen (Southern Germany).

Holotype: SMNS 63596 ; completely preserved gladius of an adult individual.

Paratypes: SMNS 63596 , 65345 , 63254 ;completely preserved adult gladii .

Type locality: Nusplingen quarry, South of Balingen ( Germany).

Type horizon: Nusplingen Plattenkalks, Upper Kimmeridgian, (Malm zeta 1), Hybonoticeras beckeri Zone.

Diagnosis.—Dorsal gladius surface flat. Granulation regular and fine.

Morphologic differences between Tr. nusplingensis and Tr. hastiformis are small and thus difficult to determine in poorly preserved specimens, but in well preserved specimens they are distinct. Tr. nusplingensis lacks the spindle−shaped elevation on the median field described in Tr. hastiformis . In comparison to the coarse and irregular granulation in Tr. hastiformis , granulation in Tr. nusplingensis is fine and regularly arranged throughout the whole gladius length ( Table 1 ).

Description of the holotype.—Specimen SMNS 63596 consists of an almost complete and nearly uncompacted gladius in dorsal view ( Fig. 5A ). Only a few millimetres of the rearmost part are missing ( Table 1 ). The overall shape of the gladius seems to be identical to T. hastiformis . Since the gladius is only slightly compacted these measurements are valuable proxies reconstructing real gladius proportions, and the dorsal relief can easily be investigated. The hyperbolar zone forms a distinct furrow between the lateral fields and median field. The boundary between the hyperbolar zone and the median field is sharp, because the curvature of the median field is stronger than the lateral fields. Inner asymptotes are therefore well definable. Outer asymptotes indicating the transition from lateral fields into hyperbolar zones are discernable by weak growth lines.

After 50% of the total gladius length, the curvature of the median field decreases. Anteriorly, the median field is almost flat.

The granulated area diverges constantly at a narrow angle of 12 °. Granules are arranged in anteriorly directed parabolic lines ( Fig. 5A 2 –A 4 ). Their size increases from posterior to anterior. Most anteriorly preserved mantle musculature covers the granulated area. Outer tubercles have the same size as inner ones. Laterally and medially, they form an indistinct ridge throughout the gladius length.

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

Figures

Fig. 5. Gladius of vampyropod coleoid Trachyteuthis nusplingensis sp. nov. A. Holotype (SMNS 63596), Upper Kimmeridgian (Hybonoticeras beckeri Zone), Nusplingen. A1, gladius seen in dorsal aspect; A2, close−up of A1 showing the granules at the anterior third of the gladius; A3, close−up of A1 showing the granules at the middle third of the gladius; A4, close−up of A1 showing the granules at the posterior third of the gladius. B. Specimen SMNS 63259, Upper Kimmeridgian (Hybonoticeras beckeri Zone), Nusplingen, gladius seen in dorsal aspect. C. Specimen SMNS 65345, Upper Kimmeridgian (Hybonoticeras beckeri Zone), Nusplingen, gladius seen in dorsal aspect.

Fig. 2. Gladius shape variation in Trachyteuthis. A. Planar type. B. Nonplanar type.C. Keeled type.The granulated area is marked by a pointed line.

Fig. 4. Gladius of vampyropod coleoid Trachyteuthis hastiformis (Rüppell, 1829). Specimen SOS 5762, Lower Tithonian (Hybonoticeras hybonotum Zone), Sappenfeld (Solnhofen area). A. Dorsal view. B. Close up of A showing the anterior mantle margin. Note that the gladius protrudes from the latter. C. Close−up of A showing position and shape of the paired fins. D. Close−up of A showing the granules at the anterior third of the gladius. E. Close−up of A showing the granules at the middle third of the gladius. F. Close−up of A showing the granules at the posterior third of the gladius.