Cementula Regenhardt, 1961

Słowiński, Jakub, Vinn, Olev, Jäger, Manfred & Zatoń, Michał, 2022, Middle and Late Jurassic tube-dwelling polychaetes from the Polish Basin: diversity, palaeoecology and comparisons with other assemblages, Acta Palaeontologica Polonica 67 (4), pp. 827-864 : 837-845

Genus Cementula Regenhardt, 1961

Type species: Cementula sphaerica ( Brünnich Nielsen, 1931) ; Maas- trichtian ( Upper Cretaceous ), Nørre Uttrup, Denmark .

Cementula spirolinites (Münster in Goldfuss, 1831) Fig. 5A–C .

1831 Serpula spirolinites sp. nov.; Münster in Goldfuss 1931: 229, pl. 68: 5a–c.

1956 Serpula (Dorsoserpula) spirolinites Münster, 1831 ; Parsch 1956: 221, pl. 21: 29.

2004 Cementula spirolinites (Münster in Goldfuss, 1831); Radwańska 2004: 39, pl. 2: 6–8.

2019 Cementula spirolinites (Münster in Goldfuss, 1831); Kočí et al. 2019: 317: 4 D.

Material.— 122 specimens attached to sponges from the lower Oxfordian (Upper Jurassic) of Zalas , Polish Jura (see Table 1); GIUS 8-3746 .

Description.—Tubes up to 100 mm long. Predominantly straight or slightly undulating tube portions alternate with planispiral coils. Tube diameter small (not exceeding 2 mm), almost constant throughout the length of the tube and apparently small also if compared to the diameter of the spiral. Within most spirals, the tube not overgrowing its previous whorls, so that all whorls most often remain visible. About five whorls usually tightly contiguous; however, in some loops the whorls without tight contact and more or less irregularly coiled, and most often with a small open umbilicus in the center of the spiral. Usually, the tubes attached to the substrate by indistinctive basal flanges. A single well-developed median keel present along the entire length of the tube. Transverse elements represented by rare, irregularly occurring alae-type peristomes, strongly developed on top of the tube and less strongly and less often developed in the upper-lateral position where the peristome may resemble a pair of “ears”. However, they stay rather faint outside these positions and close to the basal margins. Apart from the median keel and peristomes, the tube’s external surface smooth and without any additional ornamentation. The cross-section usually rounded-triangular.

Remarks.—Our specimens described above resemble tubes of Spiraserpula oligospiralis Ippolitov, 2007b , in several features: consistent median keel throughout entire length of the tube, alternation of straight portions with contiguous coiled spirals leaving an open umbilicus, and absence of ITS (Internal Tube Structures). However, they differ by the spirals growing larger in diameter and amounting to a considerably higher percentage of the total tube length, as well as by the keel being conspicuous already in the posterior tube portion. The genera Spiraserpula Regenhardt, 1961 , and Cementula are hardly distinguishable due to similarities in external appearance, in spite of the fact that Spiraserpula tends to grow to a larger size forming a more complex tube system consisting of alternating straight tube portions and several spirals. A reliable distinction between the genera Spiraserpula and Cementula , as previously mentioned by Pillai (1993) and Pillai and Hove (1994), is based only on the presence of ITS, which are present in Spiraserpula , while in Cementula they are absent. Thus, the principal character allowing distinction between these two genera is the potential ability to form ITS in Spiraserpula . To prevent ambiguous determinations where ITS would be an exclusive feature determining this taxon, Ippolitov (2007b) proposed to consider Cementula as a subgenus of Spiraserpula . Although an ability to form ITS cannot be taken as the only taxonomic feature simply due to taphonomic reasons, possibly except for well-recog- nizable species within certain stratigraphic intervals (e.g., Cementula spirolinites ), in principle this problem seems to refer to younger species than those described here. To the best of our knowledge, until now not a single ITS in tubes of any Spiraserpula species older than Campanian has been found (see Pillai 1993; Pillai and Hove 1994; Jäger 2005).

Stratigraphic and geographic range.—The material studied herein come from lower Oxfordian (Upper Jurassic) of Zalas, Polish Jura. This species was also reported from the Oxfordian (Upper Jurassic) of central Poland (Wapienno Quarry) by Radwańska (2004), Germany (Goldfuss 1831; Parsch 1956), and Czech Republic ( Kočí et al. 2019).

Cementula radwanskae sp. nov.

Fig. 5D–G .

Zoobank LSID: urn:lsid:zoobank.org:act:67B0722D-4F88-4DDD-A813-C090E89B4E54

Etymology: In honor of Urszula Radwańska in recognition of her studies on tube-dwelling polychaetes.

Type material: Holotype: GIUS 8-3589 /7 (almost complete coiled tube attached to a bivalve shell fragment, partially encrusting another Cementula radwanskae sp. nov.) . Paratypes: GIUS 8-3589 /8, GIUS 8-3589 /9 (two slightly eroded coiled tubes attached to a bivalve shell fragment). All from type locality and type horizon, see below.

Type locality: Zalas near Krzeszowice, southern Poland .

Type horizon: Middle–upper Callovian (Middle Jurassic) .

Material.—33 well-preserved specimens encrusting mainly bivalves from the Middle Jurassic of the Polish Jura (4 from Bolęcin and 29 from the Callovian of Zalas) (see Table 1); GIUS 8-3589, GIUS 8-3745.

Diagnosis.—The tubes forming rather small spirals which are coiled in a compact tight mode. Keels and peristomes lacking. The entire surface covered by delicate wrinkles and corrugations and lines of tiny granules.

Description.—Tubes very small, planispirally coiled. Spirals reaching only up to 3 mm in diameter, usually consisting of up to five whorls. Predominately sinistrally coiled, but both directions of coiling may occur. Rarely, small anterior tube portions uncoiled. All the whorls are tightly adherent to each other. The umbilicus in the center of the spiral is tiny or absent. Tubes are attached to the substrate by their entire length and do not overgrow each other. Tube diameter (less than 0.5 mm) increasing only very slowly or constant in the anterior part. The tubes lacking any strongly developed ornamentation such as keels or peristomes, but usually the entire surface densely covered by somewhat irregular delicate corrugations, wrinkles and lines of tiny granules protruding slightly at the tube’s median line. Cross-section circular or subcircular.

Remarks.—The specimens studied are similar to Cementula cf. circinnalis (MünsterinGoldfuss,1831) occurringinBajocian–Bathonian (Middle Jurassic) deposits of Ogrodzieniec-Świertowiec, but differ from this species in granulate ornamentation present on a vast majority of Cementula radwanskae sp. nov. specimens and more tightly coiled whorls. Cementula radwanskae sp. nov. bears features somewhat similar to the species Cementula sp. 2 from the Bajocian of Normandy, France, described by Breton et al. (2020), whose spirals, however, may reach more than twice the diameter of the spirals of C. radwanskae sp. nov. Cementula radwanskae sp. nov. differs from C. spirolinites by its much smaller size, compact coiling mode, and universal lack of keels and peristomes. In contrast to C. circinnalis , C. radwanskae sp. nov. possesses delicate wrinkles and corrugations on the entire surface and has more tightly coiled whorls. In contrast to Cementula complanata (Goldfuss, 1831) (see Jäger and Schubert 2008), C. radwanskae sp. nov. possesses occasionally straightened anteriormost tube portion and has delicate ornamentation.

Stratigraphic and geographic range.—The material studied herein comes from upper Bathonian–lower Callovian (Middle Jurassic)of Bolęcin,and Callovian(Middle Jurassic) of Zalas, Polish Jura. Possibly, the species may also occur in the Bajocian of Normandy, France ( Breton et al. 2020).

Cementula cf. circinnalis (Münster in Goldfuss, 1831) Fig. 6A, C .

Material.—38 well-preserved specimens exclusively encrusting oncoids from the upper Bajocian – lower Bathonian (Middle Jurassic) of Ogrodzieniec-Świertowiec, Polish Jura (see Table 1); GIUS 8-3750.

Description.—Tubes very small, planispirally coiled, usually consisting of three to five whorls. Sinistral and dextral spirals occur. The maximum diameter of entire spiral reaching only 3 mm, while the tube diameter does not exceed 0.5 mm. Most of the whorls very tightly coiled; however, in some specimens they are not completely adpressed, and show small chinks left between subsequent whorls. A minute umbilicus occasionally present in the center of the spiral. In some cases, anteriormost tube portions straight and not adhering to the previous whorl. The attachment area sometimes widened at the basal margins. The tube diameter increasing moderately fast in the early ontogenetic stages, but rather constant in the adult tube portions. The external surface of the tubes completely smooth. Cross-section circular to subcircular.

Remarks.—In overall shape, these tubes are similar to those assigned to Cementula radwanskae sp. nov.; however, in all cases they differ in having an entirely smooth surface lacking any ornamentation, whereas C. radwanskae sp. nov. possesses granulate ornamentation. Coiling mode is also slightly different in the vast majority of spirals, the tubes are less tightly coiled than in C. radwanskae sp.nov. and straight tube portions in the anterior occur more frequently. Therefore, we consider them separate species. The type of Cementula circinnalis comes from the lower Aalenian (Middle Jurassic; Goldfuss 1831). Another possible affiliation is Cementula filaria (Goldfuss, 1831) , but due to the unification of species from two presumably different genera under this name by Goldfuss (1831), the species name “ filaria ” seems to be not a good choice for these Middle Jurassic forms. Specimens presumably of the same species as those discussed here were described from the Bajocian of Normandy under the name Cementula sp. 1 by Breton et al. (2020).

Genus Serpula Linnaeus, 1758

Type species: Serpula vermicularis ( Linnaeus, 1767) ; Recent , western European seas .

“ Serpula cingulata Münster in Goldfuss, 1831”

Fig. 6B .

Material.— Three specimens attached to sponges from the lower Oxfordian (Upper Jurassic) of Zalas , Polish Jura (see Table 1); GIUS 8-3746 .

Description. —Tubes relatively short (ca. 10 mm long), attached to the substrate along their entire length.Tube diameter increases slowly, up to 1 mm. Tubes slightly undulate forming delicate curves. Attachment structures absent, although basal parts of the tubes are slightly widened. Ornamentation consisting of thick, densely and regularly spaced, ringlike peristomes present along the whole length of the tube. Longitudinal elements are absent. Cross-section not well-visible; likely subcircular due to the overall shape of the tube.

Remarks.—The name “ Serpula cingulata ” is derived from Münster in Goldfuss (1831), although the true generic affiliation of the present species to the genus Serpula is unclear.

Stratigraphic and geographic range.—The material studied herein comes from the lower Oxfordian (Upper Jurassic) of Zalas, Polish Jura; present also in the Upper Jurassic sponge facies of Germany ( Parsch 1956: 215).

Genus Propomatoceros Ware, 1975

Type species: Propomatoceros sulcicarinata (Ware, 1975) ; Aptian (Lower Cretaceous), Faringdon, UK .

Propomatoceros lumbricalis ( Schlotheim, 1820)

Figs. 2A, 3F, 6C–F, 7A–D.

1820 Serpulites lumbricalis sp. nov.; Schlotheim 1820: 96. 1952 Serpula cf. lumbricalis Schlotheim ; Makowski 1952: 4, pl. 2: 2, 3. 1956 Serpula (Dorsoserpula) lumbricalis (Schlotheim) 1820 ; Parsch

1956: 219, pl. 20: 18, 20. 2007 Propomatoceros lumbricalis ( Schlotheim, 1820) ; Ippolitov 2007b:

432, pl. 12: 1c, 3, 6–8, 9c, 9d.

Material.—840 variably preserved specimens, mainly encrusting oysters and belemnites (31 from Kawodrza Górna, 228 from Gnaszyn Dolny, 81 from Bolęcin, and 149 from the Callovian of Zalas), but also hiatus concretions (21 from Mokrsko, 81 from Bugaj, 33 from Ogrodzieniec, 23 from Krzyworzeka, and 9 from Żarki) and oncoids (156 from Ogrodzieniec-Świertowiec) from the Middle Jurassic of the Polish Jura and Upper Jurassic of Małogoszcz (28) (see Table 1); GIUS 8-3589, GIUS 8-3730, GIUS 8-3745, GIUS 8-3747, GIUS 8-3750, GIUS 8-3751.

Description.—Tubes of different, sometimes large sizes (up to 80 mm long), straight to strongly curved, very rarely forming loops; large and robust tubes dominate in the majority of localities. Tubes grow in diameter (up to 6 mm) at a moderately fast rate. Attachment structures well developed, forming characteristic tubulae, sometimes resulting in a widened tube base; however, in some specimens flanges are less developed. Tubulae are most often divided into chambers which are visible in the abraded tube parts where the irregularly distributed transverse elements occur; hollow tubulae are rare. A prominent median keel on the top of the tube running along its entire length. In the middle and anterior parts, the keel sometimes tends to undulate. Curved alae-type peristomes, most often well developed, occur occasionally at irregular intervals. Growth lines most promi- nently near the median keel, seldom visible along the whole length of the tube. The tube surface usually smooth, only occasionally covered irregularly by tiny granules. Cross-section depending on the ontogenetic stage, most often being triangular, and subtriangular at early ontogenetic stages, and becoming more subcircular at later stages, with the lateral walls becoming more convex, and the longitudinal keel on top only delicately marked.

Remarks.—Among fossil serpulids, Propomatoceros is one of the most common, geographically widespread and geologically long-ranging genera. Its occurrence in Jurassic and Cretaceous deposits combined with conservative morphology, which varies intraspecifically and depending on palaeoenvironment and ontogeny, makes reliable species determinations within this genus remarkably difficult.

The species name Serpulites lumbricalis is historically the oldest available species name which can be included into Propomatoceros . It was introduced by Schlotheim (1820) for Middle and Late Jurassic species, but unfortunately without providing any figure or type specimen. Nevertheless, as this is the oldest available name, we decided to use it, including also some informal names such as e.g., forma “ limax ”, which Goldfuss (1831) had introduced as a species name for Bajocian (Middle Jurassic) serpulids from Southern Germany. In contrast to Schlotheim (1820), Goldfuss (1831) provided figures and more detailed information on several species which now can be included into Propomatoceros . Parsch (1956) and Ippolitov (2007b) validated the species status of Promopatoceros lumbricalis , and they considered forma “ limax ” of Goldfuss (1831) as its subjective synonym. Considering the difficulties in proposing a morphologically well-defined species concept for this genus with a well-defined stratigraphic range, here, we consider all specimens having a similar suite of features as belonging to a single species Propomatoceros lumbricalis .Althoughthespecimens are slightly variable within certain populations, they display rather congruent morphology as all the easily-distinguishable features of species of Propomatoceros , such as e.g., distinctive keel which may vary inter- and intraspecifically, and on- togenically. Thus, we regard such small-scale morphological differences which might have led to the introduction of separate species as a result of intraspecific, palaeoenvironmentally controlled changes within a given population. However, for the sake of coherence, we use such taxonomic names as forma “ limax ” and forma “ conformis ” (both of Goldfuss 1831) only as names of particular morphotypes. In fact, a part of the studied specimens of Propomatoceros lumbricalis might have been represented by the genuine representatives of Propomatoceros limax (Goldfuss, 1831) and Propomatoceros conformis (Goldfuss, 1831) .

Propomatoceros lumbricalis sensu stricto differs from the forma “ limax ” by its more prominent keel, better developed but less common peristomes, and smooth surface, as well as less convex lateral walls due to a usually faster growth. It differs from forma “ conformis ” in the more prominent and rather more undulating median keel and in the more rounded cross-section. Our specimens also exhibit a striking morphological resemblance to this species as described and figured by Ippolitov (2007b; see also Słowiński et al. 2020).

Further detailed studies are needed concerning the af- finity and the true systematic position of the genus Propomatoceros within the “ Spirobranchus group”, as well as a reliable intrageneric division of the genus. Detailed morphological studies engaging statistical methods within and between certain groups of Propomatoceros serpulids inhabiting different palaeoenvironments, both different-aged and coeval, together with microstructural data of different morphotypes will possibly help to solve this problem. Perhaps, it will allow to draw a proper universal concept of Jurassic species of Propomatoceros . All in all, at the moment it is not possible to provide unambiguous determination of species, proper differentiation between them, and exact stratigraphic ranges of all Propomatoceros fossils studied herein.

Stratigraphic and geographic range.—The material studied herein comes from the middle Bathonian–Callovian (Middle Jurassic) of the Polish Jura, and lower Kimmeridgian (Upper Jurassic) of the Mesozoic margin of the Holy Cross Mountains (Małogoszcz). This species was also reported from the Middle and Upper Jurassic of Germany ( Schlotheim 1820; Parsch 1956) and the Middle Jurassic of Central Russia ( Ippolitov 2007b).

Propomatoceros sp. 1

Figs. 7E, 8A, B.

Material.—Fivevariouslypreservedspecimens,fourofwhich encrust oyster shells and one encrusting a hiatus concretion from the upper Bajocian (Middle Jurassic) of Mokrsko and the middle Bathonian (Middle Jurassic) of Gnaszyn Dolny, Polish Jura (see Table 1); GIUS 8-3730, GIUS 8-3751.

Description.—Tubes large (up to 60 mm long) and robust, strongly curved or serpentine, rarely forming loops, but also with straight portions. Tube diameter growing moderately slowly and reaching up to 4 mm. Uneroded tube parts with an indistinct median keel presumably present along the entire tube length and forming only a slightly marked denticle above the aperture. Tubes with densely and regularly spaced, chevron-shaped transverse growth lines; in- terspaces between the growth lines only slightly wider than the width of growth lines. Common but indistinct alae-type peristomes occur at irregular intervals. The shape of growth lines and peristomes is identical, but peristomes are about twice as prominent as growth lines. Cross-section subtriangular to subcircular due to strongly convex walls in later ontogenetic stages. The tube wall is thick and often breaks along the boundary between its two layers.

Remarks.—The specimens studied superficially resemble Propomatoceros semicostatus ( Regenhardt, 1961) sensu Luci et al. (2013) in their large size, strong, characteristic ornamentation, and typical coiling. However, the type specimen figured by Regenhardt (1961) is smaller than Propomatoceros sp. 1 studied herein and more straight. In addition, the type specimen of Propomatoceros semicostatus as well as the tubes described by Luci et al. (2013) were found in Lower Cretaceous deposits; therefore, it is rather unlikely that our specimens belong to P. semicostatus . Our tubes may represent a new species; however, due to the highly limited number of specimens, we refrain from designation of the new species.

Propomatoceros sp. 2

Fig. 8C.

Material.— One specimen encrusting a small shell fragment of Ctenostreon proboscideum (Sowerby and Sowerby, 1820) from the Callovian (Middle Jurassic) of Zalas, Polish Jura (see Table 1); GIUS 8-3589 .

Description.—The tube diameter reaching 2.5 mm, but the diameter of the entire tightly coiled specimen not exceeding 10 mm. Posterior tube parts planispirally coiled and attached to the substrate along their entire length, the anterior part of the tube overgrows older portions, forming a loop with an open but narrow umbilicus, and rising above the substrate. The tube robust and possessing a not very high but consistent, only slightly undulating median keel. Otherwise the surface smooth. The base not distinctly widened; however, attachment structures visible due to expansion of the lowermost tube parts. Lateral walls distinctly convex and the tube is delicately flattened, resulting in a subtriangular or even almost circular cross-section and slightly lowered lateral sides below the median keel.

→ Fig. 7. Representatives of the serpulid polychaete Propomatoceros spp. from the Jurassic of Poland. A. Partially eroded Propomatoceros lumbricalis ( Schlotheim, 1820) encrusting an oyster shell from the middle Bathonian of Gnaszyn Dolny (GIUS 8-3730/13); eroded tube fragments show well-developed tubules, which are divided into chambers by densely spaced septa. B. Two specimens of Propomatoceros lumbricalis forma “ conformis ” and partially preserved, straight, tiny serpulid Metavermilia cf. striatissima ( Fürsich, Palmer, and Goodyear, 1994) (arrow) inside an unclosed loop of P. lumbricalis encrusting a shell fragment from the upper Bathonian – lower Callovian of Bolęcin (GIUS 8-3745/2). C, D. Propomatoceros lumbricalis forma “ limax ” encrusting shell fragments from the Callovian of Zalas (C, GIUS 8-3589/12; D, GIUS 8-3589/13). E. Robust Propomatoceros sp. 1 encrusting a hiatus concretion from the upper Bajocian of Mokrsko (GIUS 8-3751/5); the arrow points to the delicate growth lines.

Remarks.—The single tube is assigned to the Propomatoceros due to its low but distinctive keel and relatively large size. The specimen is characterized by a kind of tight coiling, which, although not common, is not so rare in Propomatoceros .

Figures

Fig.5. Serpulid polychaetes from the Jurassic of Poland. A–C. Cementula spirolinites (Münster in Goldfuss, 1831), specimen encrusting:sponge fragment from the Oxfordian of Zalas (A, GIUS 8-3746/4; B, GIUS 8-3746/5; C, GIUS 8-3746/6). D. Cementula radwanskae sp. nov., holotype (GIUS 8-3589/7, arrow) encrusting a shell fragment from the Callovian of Zalas; partially encrusting another C. radwanskae, sabellid Glomerula gordialis (Schlotheim, 1820) (white arrowhead), and serpulid Metavermilia cf. striatissima (Fürsich, Palmer, and Goodyear, 1994) (black arrowhead). E–G. Cementula radwanskae sp. nov. encrusting shell fragments from the Callovian of Zalas (E, paratype, GIUS 8-3589/8; F, paratype, GIUS 8-3589/9; G, GIUS 8-3589/10).

Fig. 6. Serpulid polychaetes from the Jurassic of Poland. A. Cementula cf. circinnalis (Münster in Goldfuss, 1831) encrusting an oncoid from the upper Bajocian–lower Bathonian of Ogrodzieniec-Świertowiec (GIUS 8-3750/4). B. “Serpula cingulata Münster in Goldfuss, 1831” encrusting a sponge fragment from the the Oxfordian of Zalas (GIUS 8-3746/7). C. Propomatoceros lumbricalis (Schlotheim, 1820) (arrowhead) and Cementula cf. circinnalis arrow) encrusting an oncoid from the upper Bajocian–lower Bathonian of Ogrodzieniec-Świertowiec (GIUS 8-3750/5). D–F. Propomatoceros lumbricalis, specimen encrusting: a piece of a belemnite rostrum from the middle Bathonian of Gnaszyn Dolny (D, GIUS 8-3730/11); an oyster shell from the middle Bathonian of Gnaszyn Dolny (E, GIUS 8-3730/12); a shell fragment from the Callovian of Zalas (F, GIUS 8-3589/11).