Filogranula spongiophila, Słowiński & Vinn & Jäger & Zatoń, 2022

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 : 836-837

Filogranula spongiophila sp. nov.

Fig. 4F, G .

Zoobank LSID: urn:lsid:zoobank.org:act:D9C5AD2A-271B-4D41-B6

C9-0D02C21E584D

Etymology: After the substrate (sponges), the sole substrate this species encrusts.

Type material: Holotype: GIUS 8-3746 /2 (almost completely preserved tube attached to a sponge substrate) . Paratype: GIUS 8-3746 /3 (almost completely preserved tube attached to a sponge substrate) from the type locality and horizon .

Type locality: Zalas near Krzeszowice, southern Poland .

Type horizon: Lower Oxfordian , Upper Jurassic .

Material.— 16 specimens encrusting sponges from the type locality and horizon (see Table 1); GIUS 8-3746 .

Diagnosis.—A species of the genus Filogranula which lacks continuous keels; instead, it has three longitudinal rows of large granules. Moreover, occasionally a free apertural part and peristomes occurring like thickenings on the tube may be present.

Description.—Tubes small to medium-sized (5–20 mm long; tube diameter 0.5–1.5 mm), usually straight or only slightly undulating, and attached to the substrate by most of their length; however, in some specimens the anterior part is detached by angular folding and erected upwards. Lateral tube walls are almost parallel, only slightly rounded. Tube base is not widened and lacks any flanges or attachment structures. Longitudinal ornamentation is strongly developed and becomes most distinctive in the anterior part of the tube. Keels are lacking; instead, each tube bears three longitudinal rows of large granules which are present along the entire tube length. They may project over the aperture. The median line of granules may be slightly weaker in some specimens. Transverse elements are occasionally represented by irregularly distributed, thick, somewhat nodular (due to the granules), very slightly flaring peristomes occurring rather like thickenings on the tube. However, peristomes are not always present. Tube cross-section rounded pentagonal or petaloid.

Remarks.— Filogranula spongiophila sp. nov. differs from F. runcinata by having rows of granules instead of continuous keels. Moreover, it differs from Filogranula tricristata (Goldfuss, 1831) by its thicker peristomes and the presence of occasionally a free-apertural part. Filogranula spongiophila sp. nov. differs from other species investigated in the present study in the presence of petaloid aperture sometimes raised above the substrate, and keels substituted by rows of granules. However, these regularly ornamented, denticulated forms occur solely within the lower Oxfordian sponge facies of Zalas and are clearly different from Filogranula runcinata from the upper Bajocian–Callovian of other localities mentioned above. To the best of our knowledge, these and similar fossils have not been found in any other locality and currently are known only encrusting sponges from Zalas. Thus, their assignment to a new species is justified.

Stratigraphic and geographic range.—Lower Oxfordian (Upper Jurassic), Zalas, Poland.

Figures

Fig. 4. Serpulid polychaetes from the Jurassic of Poland. A. Metavermilia? sp. encrusting a belemnite rostrum from the middle Bathonian of Gnaszyn Dolny (GIUS 8-3730/9). B–E. Filogranula runcinata (Sowerby, 1829), specimens encrusting: an oncoid from the upper Bajocian–lower Bathonian of Ogrodzieniec-Świertowiec (B, GIUS 8-3750/3); a hiatus concretion from the upper Bajocian of Mokrsko (C, GIUS 8-3751/4); shell fragments from the middle Bathonian of Gnaszyn Dolny (D, GIUS 8-3730/10), the Callovian of Zalas (E, GIUS 8-3589/6). F, G. Filogranula spongiophila sp. nov. encrust- ing sponge fragments from the Oxfordian of Zalas (F, holotype, GIUS 8-3746/2; G, paratype, GIUS 8-3746/3). Scale bars 1 mm.