Serpula ” calannai, Sanfilippo & Rosso & Reitano & Viola & Insacco, 2018

Sanfilippo, Rossana, Rosso, Antonietta, Reitano, Agatino, Viola, Alfio & Insacco, Gianni, 2018, New serpulid polychaetes from the Permian of western Sicily, Acta Palaeontologica Polonica 63 (3), pp. 579-584 : 580-583

Family Serpulidae Rafinesque, 1815 Genus Serpula Linnaeus, 1758

“ Serpula ” calannai sp. nov.

Figs. 2 , 3A–F .

Etymology: In honor of the paleontology amateur collector the late Mario Calanna (1945–2014), for his contribution to natural history collections, especially in malacology.

Holotype: MSNC 4549-33 , one large tube portion (44 mm long and 7.8 mm wide), representing part of an unattached anterior erect portion, broken at both ends and partially filled by lithified sediment.

Type locality: Sosio Valley, western Sicily, Italy.

Type horizon: “Pietra di Salomone” Limestone, Wordian to upper Permian (see Material and methods).

Material.— Type material only.

Diagnosis.—Tube quite large, with a well-developed raised anterior end, circular in cross-section, with outer surface feebly rough. Ornamentations solely consisting of eristomes well developed and slightly flaring. Tube wall thick and layered.

Description.—The single available specimen is a large tube portion of the anterior end, 44 mm long and 7.8 mm wide. It is slightly bent and circular in cross-section, not increasing in diameter. Outer surface is feebly lumpy to smooth, with only irregular and inconspicuous growth lines, which are about 10 μm thick. Peristomes are well developed, differently pronounced and slightly flaring, with smooth, circular edges, locally crenulated. Peristomes are protruding up to 300 μm and irregularly spaced, at intervals of 2–6 mm. Tube wall is about 600 μm thick, with a seemingly layered internal structure, as barely visible along some sections, which cross areas that are not completely altered by recrystallization. Posterior (attached) tube portion is lacking.

Remarks.—The combination of tube characters of “ Serpula ” calannai sp. nov. are considered sufficient to describe it as a new species. Particularly, this species clearly differs from the other five serpulids recently mentioned from the same area ( Sanfilippo et al. 2016, 2017b) by the relevant size of the tube, which is significantly larger and thicker than those of these other species, and by the presence of evident peristomes. Obvious differences also exist with species that have erect anterior ends, but show different co-occurring characters: Palaeotubus sosiensis Sanfilippo, Reitano, Insacco, and Rosso, 2016 , has a tube ornamented by a number of longitudinal keels; Serpula distefanoi Sanfilippo, Rosso, Reitano, and Insacco, 2017b , has a tube end with evident growth lines and a rougher outer surface; Serpulidae gen. et. sp. indet. sensu Sanfilippo et al. 2017b, has a very smooth tube, with regular growth lines and only weak annulations but no peristomes. “ S.” calannai sp. nov. only roughly recalls Propomatoceros permianus Sanfilippo, Rosso, Reitano, and Insacco, 2017b , of which exclusively its posterior part is known. However, it is not unlikely that, even if this latter species developed an anterior adult part circular in cross section and ornamented with peristomes (as it is in some other serpulid species), it would have retained typical transverse ribs that are lacking in “ S.” calannai sp. nov.

Contrary to the specific attribution, the generic allocation is difficult, owing to the absence of preserved characters of taxonomical importance (e.g., Weedon 1994, Vinn and Mutvei 2009, Vinn et al. 2008) in the available material, because neither the morphology of the attached tube portion nor the pristine structure of the tube wall are fully known. Like some species of the genus Vermiliopsis Saint-Joseph, 1894 , “ Serpula ” calannai sp. nov. possesses distinct peristomes, but its tube does not increase in diameter and lacks the longitudinal keels typical of that genus ( Jäger 2005, 2011; ten Hove and Kupriyanova 2009). In contrast, particularly large-sized tubes with circular anterior ends and evident peristomes can be present in Serpula ( Sanfilippo and Mòllica 2000; ten Hove and Kuprianova 2009; Sanfilippo et al. 2013). Consequently, we provisionally assign the new species to “ Serpula ”, a genus name often misused to allocate species of the family Serpulidae whose characters are insufficiently known and/or do not allow an unequivocal generic attribution (see Jäger 1993). If further specimens will be found, including attached tube parts with less altered wall structure, it would be possible to support the present attribution more consistently or disregard it.

“ Serpula ” calannai sp. nov. resembles the present-day S. cavernicola Fassari and Mòllica, 1991 , more than the other species in the genus, for its very long erect part with a relevant diameter and comparable, and even major, wall thickness, as well as for the occurrence of peristomes. However, S. cavernicola has longitudinal keels. This species also shows a special micromorphology of the outer surface ( Sanfilippo and Mòllica 2000: figs. 1, 2), which seems to be different from that of S. calannai . In the new species growth lines are obvious and perfectly preserved ( Fig. 3E ) evidencing that the outer surface is not affected by any process of destructive taphonomic processes (e.g., abrasion, dissolution).

Stratigraphic and geographic range.— Type locality and horizon only.

“ Serpula ” prisca sp. nov.

Figs. 2B , 4A–D .

Etymology: From Latin priscus, ancient; referring to both the age of the outcrop where the species was found, and to the primordial position of the species in the serpulid family.

Holotype: PMC.S5.15.09.2017, a fragment, broken at both ends, of a slightly curved free anterior tube portion. The fragment is 43 mm long and 3.9 mm wide, and appears recrystallized.

Type locality: Sosio Valley, western Sicily, Italy.

Type horizon: “Pietra di Salomone” Limestone, Wordian to upper Permian (see Material and methods).

Material.— Type material only.

Diagnosis.—Tube relatively large, with a well-developed raised anterior end. Tube circular in cross-section, outer surface smooth with very thin growth lines and nearly imperceptible longitudinal striations.

Description.—The single specimen consists of a slightly curved tube fragment corresponding to a long anterior tube portion. It is circular in cross-section with a constant diameter of 3.9 mm. Lumen 3.3 mm wide. Tube wall 0.3 mm thick. Outer surface smooth, with very thin and smooth growth lines spaced at intervals of usually 100 to 300 μm, but locally more closely spaced and evident. Even thinner and nearly imperceptible longitudinal striations, locally intersect the growth lines. Posterior encrusting tube portion unknown. Original microstructure of the tube wall not preserved.

Remarks.—Even incomplete, the measurements of the fragment most probably indicate that it belonged to an adult specimen. The available tube portion provided distinctive characters justifying the erection of a new species. “ Serpula ” prisca sp. nov. has a unique, extremely smooth tube, that differs from all other serpulids from the Sosio Limestone, only superficially resembling Serpulidae sp. nov. indet. Sanfilippo et al. 2017b. Nevertheless, the latter species is smaller-sized, shows more evident growth lines than S. prisca sp. nov. and lacks longitudinal striations.

Like for the previous species, generic allocation is difficult, mostly because of the absence of the posterior attached part. The tube roughly resembles that of species belonging to Protula Risso, 1826 , which may have comparable long raised anterior tube portions, not (noticeably) increasing in diameter, and lacking keels and peristomes. The delicate micromorphology with imperceptible longitudinal striations is somewhat similar to that of some scaphopod gadilinidae shells ( Scarabino 1995), but differs for disposition of growth lines. Also, the smooth outer morphology of the new species is comparable to that observed in Protula but in this species the outer surface is rougher (RS, unpublished data). In absence of a more fitting genus, we provisionally assign this species to “ Serpula ”, pending further support from more complete tubes with attached portions. Large secondary calcite crystals occur in the tube wall, whose original structure has been obliterated by diagenesis. The tube of S. prisca sp. nov. does not show any evidence of a worst preservation in respect to that of the other species ( S. calannai sp. nov.) described herein: both species come from the same outcrop, thus presumably underwent similar process of fossilization which led to similar degree of diagenetic preservation (heavy recrystallization, with large secondary calcite crystals). In spite of this, tubes of the two species possess different micromorphology. The tube of S. calannai sp. nov. displays a lumpy surface, with irregular growth lines, about 10 micron thick ( Fig. 3E ). In addition, several well-developed peristomes occur in the tube of S. calannai sp. nov. They are irregularly spaced and surprisingly very frequent along the tube (at intervals of 2–6 mm). Conversely, tube of S. prisca sp. nov. is perfectly smooth and lacks even slightly developed peristome. Also, both tubes represent anterior erect parts that largely differ in size: S. calannai sp. nov. is twice the size of S. prisca sp. nov. (outer diameter 7.8 mm and 3.9 mm) and has a thick wall, twice that of the other.

If these tubes belonged to the same species, the dimensional range (variability of the diameter of 4 mm) would be too large, and the hypothesis of an intraspecific variability would be little supportable. Likewise, the difference in thickness of the tube wall (0.3 mm) is likely too much to fit into a variability. It should also be considered that usually the raised parts of the tubes maintain substantially a constant diameter and a constant wall thickness. It is likely that tubes with such obvious differences belong to two different species rather than represent variants of the same species.

Stratigraphic and geographic range.— Type locality and horizon only.

Figures

Fig. 2. New serpulid polychaetes from the Wordian to upper Permian, “Pietra di Salomone” Limestone, Sicily, Italy. A. “Serpula” calannai sp. nov. (holotype MSNC 4549-33); general views (A1–A3), cross section of tube, white limestone partly filling lumen (A4). B. “Serpula” prisca sp. nov. (holotype PMC.S5.15.09.2017); general view of anterior end, partially embedded in rock.Arrow indicates growth directions for all tubes.

Fig. 3. Serpulid polychaete “Serpula” calannai sp. nov. (holotype MSNC 4549-33) from the Wordian to upper Permian, “Pietra di Salomone” Limestone, Sicily, Italy. A. Tube fragment before assembling. Growth direction, inferred from the slightly flaring peristomes, marked by an arrow. B. Detail of a peristome and growth lines.C. Longitudinal fracture of tube displaying wall section and inner surface covered by secondary crystals. D. Oblique view of tube showing prominence of ornamentations. E. Detail of C showing layered structure of tube wall, only locally preserved. F. Circular cross section of tube, with relatively thick wall locally showing its likely original layering. All SEM images.

Fig. 4. Serpulid polychaete “Serpula” prisca sp. nov. (holotype PMC. S 5.15.09.2017) from the Wordian to upper Permian, “Pietra di Salomone” Limestone, Sicily, Italy. A. Central portion of the tube glued together, with only feeble growth lines on its outer surface.B. Tube wall with large secondary calcite crystals pointing to complete recrystallization. C. Close-up of outer surface showing very thin and smooth growth lines. D. Magnification of C, with closely spaced, relatively prominent growth lines, crossed by nearly imperceptible longitudinal striations. All SEM images.