Trachyteuthis hastiformis ( Rüppell, 1829 )

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 : 579-582

publication ID	https://doi.org/ 10.5281/zenodo.13748968
persistent identifier	https://treatment.plazi.org/id/630D066F-D239-F552-FCE4-05B57E24E0D5
treatment provided by	Felipe
scientific name	Trachyteuthis hastiformis ( Rüppell, 1829 )
status

Treatment

Trachyteuthis hastiformis ( Rüppell, 1829)

Figs. 3 View Fig , 4 View Fig .

1825 Sepia prisca sp. nov.; König 1825: pl. 27: 201 (nomen nudum).

1829 Sepia hastiformis sp. nov.; Rüppell 1829: 9–10, pl. 3: 2.

1837 Sepia obscura sp. nov.; Münster 1837: 252 (nomen nudum).

1837 Sepia regularis sp. nov.; Münster 1837: 252 (nomen nudum).

1837 Sepia linguata sp. nov.; Münster 1837: 252 (nomen nudum).

1837 Sepia venusta sp. nov.; Münster 1837: 252 (nomen nudum).

1837 Sepia antiqua ; Münster 1837: 252 (nomen nudum).

1835–48 Sepia hastiformis ; Férrussac and d’Orbigny 1835–48: pl. 16: 1, 2.

1835–48 Sepia antiqua Münster ; Férrussac and d’Orbigny 1835–48: pl. 14: 1, 2.

1835–48 Sepia caudata Münster ; Férrussac and d’Orbigny 1835–48: pl. 15: 1, 2.

1835–48 Sepia linguata Münster ; Férrussac and d’Orbigny 1835–48: pl. 14: 3, pl. 15: 4, 5, pl. 16: 3.

1846 “without appellation”; Münster 1846: pl. 9: 3.

1846 Trachyteuthis ensiformis ; Meyer 1846: 598.

1846 Trachyteuthis oblonga sp. nov.; Meyer 1846: 598 (nomen nudum).

1855 Trachyteuthis ensiformis sp. nov.; Meyer 1846: 106–109, pl. 19: 1.

1922 Trachyteuthis hastiformis Rüppell, 1829 ; Naef 1922: 137, figs. 51, 52.

1977 Trachyteuthis hastiformis ; Rietschel 1977: fig. 6.

1986 Trachyteuthis hastiformis Rüppell, 1829 ; Bandel and Leich 1986: 140, figs. 14, 15.

1988 Trachyteuthis hastiformis Rüppell, 1829 ; Engeser 1988: 59.

1995 Trachyteuthis sp. ; Donovan 1995: 2, figs. 1–4.

2003 Trachyteuthis hastata Rüppell, 1829 ; Donovan et al. 2003:93, fig.1.

2006 Trachyteuthis hastiformis ; Fuchs 2006a: 52, text−fig. 3.6−4, pl. 14: A–C.

Holotype: SMF IX1328 About SMF , original of Rüppell (1829: 9–10, pl. 3: 2).

Type locality: Mühlheim (Solnhofen area, Southern Germany).

Type horizon: Solnhofen Plattenkalks, Lower Tithonian, Solnhofen Formation (Malm zeta 2b), Hybonoticeras hybonotum Zone.

Diagnosis.—Gladius median field with a spindle−shape elevation. Dorsal granulation coarse and irregular.

Nomenclatural remarks.—As Sepia prisca König, 1825 (pl. 27: 201) remained unpublished, Sepia hastiformis Rüppell, 1829 has priority. Sepia antiqua Férrussac and d’Orbigny, 1835 –48, Sepia caudata Férrussac and d'Orbigny, 1835 –48 and Sepia linguata Férrussac and d’Orbigny 1835 –48 are considered to be junior subjective synonyms of Sepia hastiformis Rüppell, 1829 . After re−investigation of the originals of both Rüppell (1829) and Meyer (1855), we ascertain that Trachyteuthis ensiformis Meyer, 1846 is identical with Sepia hastiformis Rüppell, 1829 . Trachyteuthis ensiformis Meyer , 1846 is therefore a junior subjective synonym of Sepia hastiformis Rüppell, 1829 .

Re−description of the holotype.—The original of Rüppell (1829: pl. 3: 2) includes part and counterpart ( Fig. 3A View Fig ). The figured gladius represents the lower slab because the outline of the fossil is elevated above the bedding plane of the slab (“Sockelerhaltung”, see Seilacher et al. 1976). Shell material is preserved partly on the lower and partly on the upper slab. The upper slab exhibits the rounded anterior gladius end and parts of the posterior median field, whereas the lower slab exposes the middle portion of the median field and the outline of the anterior extremity ( Fig. 3A View Fig 1 View Fig ). The gladius has a preserved length of 225 mm ( Table 1 View Table 1 ). Neither lateral fields nor hyperbolar zones are visible. It seems that at least the left lateral field and hyperbolar zone are preserved on the lower slab but are still covered with sediment.

The lower slab displays the dorsal, the upper the ventral gladius surface. Where gladius material is missing on the upper slab imprints of the dorsal surface appear. Rüppell (1829: 10) described a “convex elevation”. Indeed, a slight spindle−shaped elevation is recognisable on both slabs ( Fig. 3A View Fig 2 View Fig ). In dorsal view, this structure seems to be raised above the gladius surface, whereas the marginal parts of the “spindle” are depressed below the gladius surface. The elevation has a longitudinal ridge, which corresponds to the median line of the gladius.

As Rüppell (1829: 19) correctly stated, the granules are arranged in anteriorly directed parabolic lines ( Fig. 3A View Fig 2 View Fig ). But the granulation becomes more and more irregular at the anterior gladius half. From posterior to anterior, the fine granulation also becomes coarser (except the most anterior gladius end). Granules are finest at their outer margin and coarsest in the median line. The granulated area has its maximum width within the spindle−shaped area.

Both slabs clearly demonstrate that the gladius was laminated. Especially the lower slab shows that only the uppermost (dorsal) layer bears the granulation. Where this layer is exfoliated growth lines become visible.

Re−description of the specimen of Meyer (1855: 106–109, pl. 19: 1).—The gladius of Meyer’s specimen ( MARKA 1) exposed in ventral aspect has a preserved length of 295 mm ( Table 1 View Table 1 , Fig. 3B View Fig ). Only 20–25 mm of the most anterior end is not preserved. Imprints of the dorsal tubercles are visible where gladius material is missing. Granules are irregularly arranged.

The outer margins of the gladius are imperfectly dissected. Length and width indices are therefore doubtful. However, as Meyer (1846: 107) correctly stated, the ratio of hyperbolar zone length to total gladius length is between 0.39 and 0.42.

Growth increments are not visible. One can see several diverging lines in the posterior portion, but inner and outer asymptotes are difficult to determine.

A spindle−shaped elevation, which is not mentioned by Meyer (1846), is present in the middle portion of the median field ( Fig. 3B View Fig 2 View Fig ). This structure, 70–80 mm in length and 20–30 mm in width, possesses a central depression along the median line. The posterior end of the spindle is more pronounced than the anterior. It commences approximately at the anterior end of the lateral field.

Further specimens of Tr. hastiformis with a distinct spindle−shaped elevation on the median field were previously figured in Rietschel (1977: fig. 6), Bandel and Leich (1986: fig. 15), Donovan (1995: fig. 1), Fuchs (2006a: fig. 3.6−4, pl. 14: A–C). Férrussac and d’Orbigny (1835–48) probably observed the same structure, because a spindle−shaped depression is clearly visible in their drawing of Sepia antiqua (pl. 14: 2).

Wagner (1860: 755) was apparently the first who reported this peculiar structure. He wrote on page 755 (translated from German): “From time to time a longitudinal bulge arises on the granulated surface representing a longitudinal furrow on the ventral side.”

Description of a three−dimensionally preserved specimen of Tr. hastiformis .—A previously undescribed specimen ( SOS 5762) from Sappenfeld (Solnhofen region) exhibits a complete gladius, which is 325 mm in total length and almost unflattened ( Table 1 View Table 1 , Fig. 4A View Fig ). As mantle musculature covers the outermost margins of the gladius, length−width indices cannot be exactly determined. One can easily recognise that the spindle−shaped elevation is surrounded by a depression. The bulge is approximately 195 mm in total length (62% of the total gladius length). Its posterior end starts about 80 mm away from the posterior gladius end and shortly before lateral fields and hyperbolar zones expire. In cross−section the bulge is arquated (roof−shaped) with an indistinct ridge along the median line. The maximum width of the spindle measured half way along the total spindle length is 50–60 mm.

The alteration of the granules from posterior to anterior extremities is distinct ( Fig. 4D–F View Fig ). Posteriorly, the granulation is fine and regularly arranged in anteriorly directed parabolic lines ( Fig. 4F View Fig ). In this part, the granulated area linearly diverges with a very acute angle. When entering the spindle, the granulated area suddenly spreads out and follows the spindle ( Fig. 4E View Fig ). Simultaneously, granules become coarser and irregularly arranged. Granules located marginally within the depression are very small compared to those on the top of the bulge. Most anteriorly, where the spindle does not exist, the granulated area seems to diverge again linearly ( Fig. 4D View Fig ).

Apart from the gladius, the present specimen yields extraordinarily preserved details of soft tissues. The solid muscular mantle of this specimen is conserved in such a unique manner that the body outline of the animal and even the position of the gladius within the mantle can be easily reconstructed. The most characteristic feature is that the anterior gladius end distinctly protrudes from the anterior mantle margin ( Fig. 4B View Fig ). To a lesser extent this is also the case in Recent Vampyroteuthis . According to Bizikov (2004: 10, fig. 2), the circular mantle muscles in Vampyroteuthis attach to the ventral site of the gladius, except for the foremost rim.

In general, the body outline of Trachyteuthis hastiformis was cylindrical (bullet−shaped). The body is constantly 140 mm wide and posteriorly rounded. It seems that the lateral mantle is longer than the dorsal.

Posteriorly, one can see two pairs of lobate fins ( Fig. 4C View Fig ). This is well in accordance with previous observations made by Donovan (2002: fig. 1) and Donovan et al. (2003: fig. 2), who first reported the presence of two pairs of fins in Trachyteuthis hastiformis . Each of them is about 45–50 mm long. At their base the fins are about 20–25 mm in width. Striations of the muscle bundles are oriented parallel to the margins of the fin. Branching of muscle bundles as described by Donovan (2002) and Donovan et al. (2003) are not observed. Their position seems to be identical with those described in Donovan (2002) and Donovan et al. (2003). Both pairs were attached to the dorsal gladius surface (probably indirectly to the shell sac as in Recent vampyropods, see Bizikov 2004). The posterior pair was anchored to the rearmost part of the lateral field, whereas the anterior pair was attached to the middle part of the lateral field. Most probably the hyperbolar zone also served as an insertion site as in Vampyroteuthis ( Bizikov 2004: fig. 51).

Stratigraphic and geographic range.—Known with certainty from the Lower Tithonian (Malm zeta 2–3) of the Solnhofen Plattenkalks (Southern Germany). Tr. hastiformis probably also occurred in the Kimmeridgian (Malm zeta 1) of Nusplingen (Southern Germany).