Serpula Linnaeus, 1758

Sanfilippo, Rossana, Rosso, Antonietta, Reitano, Agatino & Insacco, Gianni, 2017, First record of sabellid and serpulid polychaetes from the Permian of Sicily, Acta Palaeontologica Polonica 62 (1), pp. 25-38 : 31-32

Genus Serpula Linnaeus, 1758

Type species: Serpula vermicularis Linnaeus, 1767 ; Recent of England .

“ Serpula ” distefanoi sp. nov.

Figs. 5 , 6 .

Etymology: Named after Pietro Di Stefano from the University of Palermo, an expert on geology and palaeontology of the Sosio Valley area.

Type material: Holotype: MSNC4527, one incomplete tube partly damaged on its upper side, attached to a sponge, partially filled by lithified sediment. Paratypes: MSNC 4528, one incomplete tube attached on a sponge; MSNC 4529, one tube fragment broken at both ends representing a part of the anterior free portion. All specimens come from type locality, except for specimen MSNC 4528 originating from the “Rupe di San Benedetto” megablock.

Type locality: Sosio Valley , western Sicily ( Italy) . Type horizon: “Pietra di Salomone” Limestone, Wordian to upper Permian .

Diagnosis.—Tube quite long, straight to slightly meandering or curved. Anterior free tube portion well developed. Transverse tube section circular in the free tube portion, somewhat flattened on the upper side in the attached part. Tube relatively thick, outer surface rough.

Description.—The holotype is an adult, 5.5 cm long tube slowly increasing in diameter up to 2.4 mm. Encrusting part initially forming a loop and then nearly straight. Anterior end free, circular in cross-section, 3 mm in outer diameter, without peristomes. Tube sub-circular in cross-section and somewhat flattened on the upper side in the encrusting adult part. Outer surface quite irregular and rough, with lateral transverse arc-shaped ridges on the encrusting part. Growth lines feeble, curved like the transverse ridges, annular and straight in the erect part. Tube wall relatively thick, ca. 0.2 mm. Internal structure of the tube wall biased by recrystallization, causing the formation of densely arranged crystals, the larger crystals situated in the central part of the wall. Paratypes: incomplete tube 11 mm long and tube fragment 5 mm long broken at both ends.

Remarks.—We consider the attached tube and the fragments of free anterior portion as belonging to the same species, due to corresponding tube diameters and wall thicknesses and to corresponding characteristic rough ornamentation of the external surfaces. One additional incomplete tube attached on a sponge, lacking its upper part, is tentatively assigned to this species.

The combination of features characteristic of the tube of this species, including the general morphology and dimensions, shape of cross-section and the distinctive rough ornamentation, are not shared with any other known tube and are considered sufficient to introduce a new species. In contrast, the generic attribution of this serpulid is difficult, because neither the unaltered original tube wall structure nor the operculum is known. Consequently, we provisionally assign the new species to “ Serpula ”, a genus name often misused as a waste-bin to allocate species of the family Serpulidae whose characters are insufficiently known and/ or do not allow an unequivocal generic attribution (see Jäger 1993). A more reliable generic attribution could be possible following a hopeful future finding of specimens preserving the unaltered tube wall structure.

Stratigraphic and geographic range.—Wordian to upper Permian of Italy.

Figures

Fig. 5. Serpulid “Serpula” distefanoi sp. nov. from the Sosio Valley, western Sicily (Italy), Wordian to upper Permian. A. MSNC 4527, general view of the holotype. B. MSNC 4529, two opposite views (B1, B2) of a tube fragment of the anterior erect part, showing the rough surface; cross section of the erect tube portion (B3).

Fig. 6. Serpulid “Serpula” distefanoi sp. nov., from the Sosio Valley, western Sicily (Italy), Wordian to upper Permian. A. Holotype MSNC 4527, SEM image of the adult portion of the tube evidencing the flattened upper part and thickenings concave towards the aperture (A1), arrow indicates the growth direction; detail of the initial part of the tube which is loop-like curved (A2); detail of the tube showing lateral growth lines and irregular thickening and roughness (A3). B. Paratype MSNC 4529, tube fragment of the anterior erect part, broken at both ends (B1), straight growth lines and rough surface are obvious on the outer tube surface. The internal mould of lithified sediment occurs within the lumen. Detail of the tube wall (B2), showing heavy recrystallization with densely patched crystals, smaller in the periphery.