Nogrobs Montfort, 1808

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 : 845-849

Genus Nogrobs Montfort, 1808

Type species: Nogrobs vermicularis Montfort, 1808 , Middle Jurassic (presumably Stephanoceras humphriesanum Zone of the Bajocian), Muttenz, Switzerland .

Nogrobs aff. quadrilatera (Goldfuss, 1831)

Fig. 9A–C.

Material.— 36 specimens, the majority of which are well-preserved, encrusting belemnite rostra from the middle Bathonian (Middle Jurassic) of Gnaszyn Dolny, Polish Jura (see Table 1); GIUS 8-3730 .

Description.—Tubes medium-sized (up to 25 mm long), straight to slightly curved, adjusting to the available solid substrates to which they are attached: small to medium-sized, but relatively long belemnite rostra. Tubes growing relatively fast in diameter in the early ontogenetic stages where some of the specimens forming either a loose or a tight spiral, whereas in the adult anterior tube portions increase in diameter (up to 1.5 mm) slowly or very slowly. The tube base sometimes delicately widened and rarely possesses hollow flanges, which are visible in a few cases where the tubes are partly worn out. Tubes distinctly flattened on top and have three median longitudinal crests, of which the two marginal ones more conspicuous than the central one, which is faint or barely present. The vast majority of specimens attached to the substrate along their entire length; only in a few tubes the anterior portions raised above a substrate. Transverse ornamentation represented by well-visible, regular growth lines which are especially well-developed between the keels. Weakly developed nodular peristomes occasionally occur. Lateral walls nearly parallel, resulting in a subquadrangular to subcircular cross-section, in some specimens slightly convex in profile. The tube wall composed of two layers.

Remarks.—The tubes are assigned to Nogrobs aff. quadrilatera (Goldfuss, 1831) because their cross-section, shape and ornamentation are characteristic for this species. Similarly to our specimens, N. quadrilatera sensu stricto has a flattened upper side, three small median keels and a subquadrangular cross-section. However, unlike in species of Nogrobs from many other localities (e.g., Germany, England), the broken-off, free tube portions which origi- nally rose above the substrate are relatively rare in our materials. Our tubes somewhat resemble Nogrobs tricarinata (Goldfuss, 1831) (see Parsch 1956: 224, pl. 21: 21). Moreover, Serpula tricarinata (Goldfuss, 1831) , is a junior homonym of Serpula tricarinata Sowerby, 1829 , the latter correctly affiliated to Mucroserpula by Ippolitov (2007b). To replace Goldfuss’ (1831) invalid junior homonym, Ippolitov (2007a) proposed a new combination Metavermilia goldfussi . Nogrobs aff. quadricarinata reported by Vinn et al. (2014: fig. 4G, H) bears similar growth lines to those present in our specimens; however, these are less visible.

Nogrobs ? aff. tricristata (Goldfuss, 1831)

Fig. 9D, E.

Material.—Eight, mostly well-preserved specimens encrusting belemnite rostra from the middle Bathonian (Middle Jurassic) of Gnaszyn Dolny, Polish Jura (see Table 1); GIUS 8-3730.

Description.—Tubes medium-sized (up to 20 mm long), straight or only slightly undulating; however, in two cases they form a loose loop in the early ontogenetic stages. The upper surface flattened and bears three consistent longitudinal keels. The central keel rather weakly developed, the lateral two are more distinct. All three keels well-visible and present in all specimens along the entire tube length. The lateral walls nearly parallel. The tubes with many irregularly distributed, flaring peristomes which in some specimens slightly protrude at the keels to form short and blunt spines. In some specimens, after forming a sharp, angular folding, the anterior tube part projecting upwards and rising above the substrate. In the anteriormost tube part, walls slightly concave. Prominent and regular growth lines

→ Fig. 8. Representatives of the serpulid polychaete Propomatoceros spp. from the Jurassic of Poland. A, B. Propomatoceros sp. 1 detached from fragmented shell from the middle Bathonian of Gnaszyn Dolny (A, GIUS 8-3730/14, B, GIUS 8-3730/15). C. Propomatoceros sp. 2 encrusting a shell fragment of Ctenostreon proboscideum (Sowerby and Sowerby, 1820) from the Callovian of Zalas ( GIUS 8-3745/3); top (C 1) and lateral (C 2) views. Note the anterior tube part overgrowing older portion of the tube and rising above the substrate (C 2). D. Propomatoceros sp. 3 encrusting a small piece of a shell from the Kimmeridgian of Małogoszcz ( GIUS 8-3747/2).

covering the flattened upper surface between the lateral keels. Perpendicular growth lines well-visible also on the lateral tube sides. The tubes gently curved, quadrangular in cross-section, and slowly growing in diameter up to 1 mm. The tube wall composed of two layers.

Remarks.—The specimens studied are tentatively assigned to Nogrobs because of their overall shape, quadrangular cross-section and perpendicular growth lines. However, these specimens may also be referred to Filogranula due to a characteristic rising above substrate in the anterior part, often slightly flaring and weakly spiny peristomes, and three consistent keels running along the entire tube, although the keels are not denticulate. Specimens discussed here are also similar in general shape to Nogrobs aff. quadrilatera described above and might also be a variation of that species from the same locality; however, differences comprise flaring and more frequent peristomes, three better developed keels, and parallel or delicately concave lateral walls (see Parsch 1956: 225, pl. 19: 17). Filogranula tricristata (Goldfuss, 1831) described from Toarcian–Aalenian (Lower–Middle Jurassic) deposits of Germany has occasionally widened base of the tubes resulting in the trapezoidal cross-section (MJ own observations), which clearly differs from the tubes described here. Moreover, Filogranula tricristata is attached to the substrate along its entire length, while the specimens discussed herein have their anterior portions occasionally raised up. This supports the distinction between the studied specimens from Poland and the typical Filogranula tricristata from the Toarcian and Aalenian from Germany.

Nogrobs aff. tetragona (Sowerby, 1829)

Fig. 9F–J.

Material.— 29 specimens from the middle Bathonian (Middle Jurassic) of Gnaszyn Dolny, Polish Jura (see Table 1); GIUS 8-3730 ; three of the specimens encrust two belemnite rostra and the rest are free-lying/detached .

Description. — Tubes small (up to 10 mm long), almost straight or only slightly curved. Nearly all free-lying; only three partially attached to the substrate. Only the attached posterior tube portion bearing a small median keel on the tube’s upper side, whereas the free anterior portion with no median keel. No growth lines visible except those on the lateral walls. Peristomes occasionally occurring; they consist of four thick nodes situated at the edges of the square. The tube diameter expanding very slowly, except for the anterior end where it (up to 1 mm) increases more abruptly. The most distinctive character of the tube, especially of its free anterior portion, is the quadrangular cross-section, with all the walls markedly concave between the edges.

Remarks.— Nogrobs tetragona was described from claystone of late Oxfordian–early Kimmeridgian age in England, and is characterized by masses of densely entangled clusters of tubes (Sowerby 1829), which are not attached to the substrate, lack any attachment scars and never tend to form a compact spiral in the posterior tube part (MJ own observations). However, N. tetragona has been used in the literature in a wider sense (e.g., Sowerby 1829; Gerasimov 1955; Ippolitov 2007a) for predominantly free tube portions, which lack or possess only inconspicuous, rare peristomes with a quadrangular cross-section, found in many localities from the Middle and Upper Jurassic of England (Sowerby 1829) and Germany ( Parsch 1956). The tubes described here match N. tetragona well, if it is understood in that wider sense. The specimens described show a very close resemblance to “ Serpula (Tetraserpula) tetragona ” (see Parsch 1956: 223, pl. 21: 14), “ Tetraserpula tetragona ” (see Ippolitov 2007a), and to a lesser extent to “ Serpula (Tetraserpula) quadrisulcata ” (see Parsch 1956: 227, pl. 21: 15), which bears more prominent and sharp margins.

Genus Mucroserpula Regenhardt, 1961

Type species: Mucroserpula mucroserpula ( Regenhardt, 1961) ; Hauterivian (Lower Cretaceous), Schandelah, north Germany .

Mucroserpula tricarinata (Sowerby, 1829) Fig. 10A .

1829 Serpula tricarinata sp. nov.; Sowerby 1829: 226, pl. 608: 3, 4.

1956 Serpula (Tetraserpula) quinquangularis Goldfuss 1831 ; Parsch 1956: 224, pl. 19: 9, pl. 20: 13, pl. 21: 25.

2007 Mucroserpula tricarinata (J. de C. Sowerby, 1829); Ippolitov 2007b: 429, pl. 12: 1a, 1b, 2.

Material.—Two partially preserved specimens attached to bivalve shells from the Callovian (Middle Jurassic) of Zalas, Polish Jura (see Table 1); GIUS 8-3589.

Description.—Tubes medium-sized (less than 20 mm long), curved in a loose loop, moderately increasing in diameter (ca. 1 mm). The tubes possessing a consistent, slightly undulating median keel and two weaker lateral keels. Delicate, perpendicular growth lines visible along most of the tubes’ length. Specimens are attached to the substrate along their entire length, and the tube base is widened, resulting in a triangular to subtriangular cross-section; however, the anteriormost parts are pentagonal due to the three keels and the edges of the base.

Remarks.—The specimens described are assigned to the genus Mucroserpula due to their characteristic three keels and the mode of coiling. In spite of the fact that the tubes are not very well-preserved, the features indicative of Mucroserpula

→ Fig. 9. Representatives of the serpulid polychaete Nogrobs spp. from the middle Bathonian (Middle Jurassic) of Gnaszyn Dolny, Poland. A–C. Nogrobs aff. quadrilatera (Goldfuss, 1831) encrusting belemnite rostra (A, GIUS 8-3730/16; B, GIUS 8-3730/17; C, GIUS 8-3730/18); the specimen in C has been partially detached from its substrate. D, E. Nogrobs ? aff. tricristata (Goldfuss, 1831) encrusting belemnite rostra (D, GIUS 8-3730/19; E, GIUS 8-3730/20); ctenostomate bryozoan colony indicated by arrow in D. F–J. Free-lying tubes of Nogrobs aff. tetragona (Sowerby, 1829) ( GIUS 8-3730/21– 25, respectively); lateral (I 1) and cross-section (I 2) view; I 2 shows characteristic quadrangular cross-section with distinctly concave walls between the edges. Notice characteristic quadrangular cross-section with distinctly concave walls between the edges visible in J. Scale bars 1 mm.

are sufficiently visible. Our specimens are small compared to other specimens of Mucroserpula tricarinata , presumably representing juveniles. Mucroserpula jaegeri Radwańska, 2004 , from the lower Kimmeridgian (Upper Jurassic; see Wierzbowski et al. 2016) of central Poland differs from M. tricarinata by its very regular spiral coiling: the posterior tube portion forms a tightly coiled spiral, whereas the anterior, which is still attached all along its length, forms a wide open spiral curve. Moreover, M. jaegeri has weaker developed lateral keels and a more distinctly flattened tube.

Stratigraphic and geographic range. —The material studied here come from Callovian (Middle Jurassic) of Zalas, Polish Jura. Mucroserpula tricarinata was also reported from the Middle and Upper Jurassic of England (Sowerby 1829), Germany ( Parsch 1956), and Russia ( Ippolitov 2007b).

Figures

Fig.10. Serpulid and sabellid polychaetes from the Jurassic of Poland.A. Mucroserpula tricarinata (Sowerby, 1829) (white arrow) and sabellid Glomerula gordialis (black arrow) encrusting a fragment of a shell from the Callovian of Zalas (GIUS 8-3589/14). B. Mucroserpula? sp. encrusting a fragment of a shell from the middle Bathonian of Gnaszyn Dolny (GIUS 8-3730/26); top (B1) and cross-section view (B2). Notice the characteristic pentagonal cross-section (B2) due to the presence of three keels. Scale bars 1 mm.