Glomerula testatrix ( Etheridge, 1892 ) Sanfilippo & Rosso & Reitano & Insacco, 2017

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 : 27-28

Glomerula testatrix ( Etheridge, 1892) comb. nov.

Fig. 2A–C .

1892 Serpula testatrix sp. nov.; Etheridge 1892: 120, pl. 18: 4, 5.

Material.—Two glomerate coiling tubes on sponges ( MSNC 4515, MSNC 4516) and one incomplete glomerate tube on a crinoid stalk ( MSNC 4517). One aggregate of tubes nearly aligned and irregularly coiled, attached on a sponge ( MSNC 4518). All specimens come from the “Pietra di Salomone” megablock, the Sosio Valley, western Sicily ( Italy); Wordian to upper Permian.

Emended diagnosis.—Tube long in respect to its width, circular in cross-section and smooth, increasing in diameter slowly. Base of the tube not widened by a basal cementing flange. Tubes more or less irregularly curved, often forming irregular spirals, intermingled meanders or chaotic knots.

Description.—Tubes are small-sized (outer diameter of 0.2– 0.25 mm) and weakly attached to the substrate, their outer surface being smooth, only marked by feeble growth lines at places. Tubes form intermingled overlaid whorls growing on previous tube portions. The original tube wall structure is biased by recrystallization showing large diagenetic crystals which locally expand inwards, also infilling the tube lumen.

Remarks.—This species was originally described as a serpulid under the name Serpula testatrix by Etheridge (1892), based on late Permian specimens from Australia. No further specimen has been found since then and no modern images or descriptions are available. Nevertheless, Etheridge’s description and figures (1892: pl. 18: 4, 5) of the holotype are sufficiently diagnostic and unequivocally indicate that the species lacks serpulid characters. In contrast, its small-sized and typically glomerate coiled tube fits well in the genus Glomerula ( Fig. 2A ), as recently suspected by Ippolitov et al. (2014). Jäger (1983, 2005) considered Omasaria Regenhardt, 1961 as a synonym of Glomerula , mainly on the basis of its typical irregularly interweaving tubes. Such tubes seem to have a very wide stratigraphic distribution. Following Ippolitov et al. (2014), the oldest Palaeozoic representatives likely attributable to Glomerula could be those reported as “ Serpula ” spp. by Stuckenberg (1905) and as tubeworms” by Hoare et al. (2002: fig. 1.1–1.7) from the Late Carboniferous. Indeed, these specimens show slowly widening tubes and a characteristic glomerate coiling.

Owing to their morphological characters, specimens found in the “Pietra di Salomone” megablock can be identified as G. testatrix . Furthermore, Australian and Sicilian specimens share the same substratum, and possibly the same habitat, because pl 18: 5 in Etheridge (1892) depicts the species encrusting crinoids. Interestingly, the stratigraphic distribution of the new G. testatrix findings is consistent with the age of the holotype material.

Like other Palaeozoic congeners, G. testatrix , with a tube diameter of only 0.25 mm, is minute in respect to Mesozoic species of Glomerula , which possess quite large tubes, from slightly less than 1 mm ( G. lombricus Defrance, 1827 ) to ca. 4 mm in diameter at maximum (e.g., Jäger 1983). Also the only known Recent species G. piloseta ( Perkins, 1991) is larger, having a diameter of about 0.5 mm.

The presence of trilobate lumina has been reported from some Cretaceous species assigned to Glomerula and used as a diagnostic feature to distinguish them from some more ancient, Jurassic congeners ( Jäger 1983, 1993, 2005). This character is also absent in G. testatrix and in other old species, as well as in Cenozoic to Modern Glomerula representatives. Consequently, it seems to be restricted only to a few Cretaceous species. We suggest here to place such species in a separate genus, pending examination of the type materials.

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

Figures

Fig. 2. Sabellids from literature (A) and from study material (B–F). A. Holotype of Serpula testatrix Etheridge, 1892 (pl. 18: 5) on a crinoid stem from East Maitland (South Wales), Permo-Carboniferous, showing typical loose loops and spirals. B, C. Glomerula testatrix (Etheridge, 1892) Sanfilippo comb. nov., from the Sosio Valley, western Sicily (Italy), Wordian to upper Permian. B. MSNC 4515, irregular glomerate interweaving tubes; photograph (B1), SEM image (B2); B3, detail of B2, showing the tube outer surface with feeble growth lines. C. MSNC 4518, set of sub-parallel tubes slightly meandering and locally forming a sharp bend encrusting a sponge. D–F. Glomerula gemmellaroi sp. nov. from the Sosio Valley, western Sicily (Italy), Wordian to upper Permian. D. MSNC 4519, holotype, specimen forming meanders and bending at angles of 90° and 180°. E. MSNC 4520, tube initially loop-like curved and then bent at right angle. F. MSNC 4521, meandering tube on a sponge.