Rivista Italiana di Paleontologia e Stratigrafia volume 104 numero 2 r*ole 1-2 pagrne 279-286 Agosto 1998 NOA BREVE SPIRORBID POLYCHAETES AS IN THE MEDITERRANEAN BOREAL GUESTS PLEISTOCENE ROSSANA SANFILIPPO Received January 1, 1988; accEted April 17, 1998 Keytaords: Spirorbidae, Boreal Guests, Pleistocene, Mediterra- nean, North Atlantic. Riassunto. Sono stati trovati numerosi tubi di policheti spiror- bidi attribuibili alle specie Spirorbis spirorbis (Linnaeus, 1758) e Spí rorbis corallinae de Silva 6c Knight-Jones, 1962, provenienti vari depo- siti del Pleistocene freddo della Sicilia, nonché da sedimenti wiirmia- ni del Mar Tirreno. Tali spirorbidi vivono lungo le coste dell'Atlanti- co settentrionale, in acque basse della piattaforma continentale, e sono assenti nell'attuale Mediterraneo. Nei sedimenti pleistocenici questi sono invece associati a faune di media piattaforma ed epibatia- li, probabilmente perché spiazzati da biotopi pirì superficiali. Viene attribuito a S, spirorbis e S. corallinae un significato paleobiogeografi- co e paleoclimatico, in base alla loro attuale distribuzione biogeogra- fica. Tali specie, entrate in Mediterraneo durante una o più fasi fredde del Pleistocene, assumono quindi il significato di Ospiti Nordici. Spe- ciale attenzione è stata, infine, rivolta alla morfologia e struttura del tubo, le quali hanno ponato all'individuazione di caratteri diagnostici a livello specifico. Abstract. A first report of Spirorbis spirorbis (Linnaeus, 1758) tnd Spirorbis coralLinae (de Silva & Knight-Jones, 1962) from Early and Middle Pleistocene deposits in Sicily and submerged Late Glacial sediments in the \Western Mediterranean is presented. Today both spe- cies live on shores and very shallow bottoms in the Nonh Atlantic and are unknown from the Recent Mediterranean, Such differences in their present and past biogeographic distributions suggest that these species were Boreal Guests (BGs) in the Mediterranean Pleistocene. Special attention ìs paid to tube morphology and structure, which bear some diagnostic features for species identification. lntroduction. The appearance in the Mediterranean of boreal shelf species, together with the progressive disappearance (since the Piacenzian) of warm-temperate taxa is a di- stinctive element of the cold Pleistocene phases (Raffi, 1986; Raffi & Marasti, 1982). These cold-water species are currently known as "Northern Guests" or "Boreal Guests" (BGs) as they spread mainly in the North Atlantic Ocean, from Arc- tic latitudes southward to the southern British Isles and the Bav of Biscav. During cold phases the BGs funnelled inro the Mediterranean, superimposing on the Mediterranean au- tochthonous temperate faunas. Their migration occurred in successive, cumulative, increasingly cold floods, which correspond in part to the chronostratigraphic re- partition of the Early Pleistocene (Raffi, 1986). BG species, early used as strarigraphic markers (N4ars 1963; Ruggieri et al. t976), were employed subsequently as palaeoclimatic tools (Di Geronimo, 1974; Malatesta & Zarlenga, 1986; Raffi, 1986; Taviani et al., 1997). Deposits rich in BGs have been studied since the last century and crop out extensively in southern kaly. Records of boreal species are known from the colder pe- riods of both the Mediterranean and the Atlantic Ocean (Taviani et al., 1991). Nevertheless, BGs are quire poor- ly documented within the East Atlantic Pleistocene se- diments (submerged thanatocoenoses) and are recorded mainly from the Mediterranean Quaternary. Most BGs are molluscs, such as the bivalve Arctica islandica, the best known North Atlantic species in rhe Mediterranean, which is now regarded as a marker for the Plio-Pleistocene boundary @uggieri er al., 1984). Other ta- xonomic benthic groups, nohbly serpulids (Zibrowius, 1979; Zlbrowius & ten Hove, 1987) have been considered sporadically as palaeoclimatic-oceanographic tools. How- ever, these Plio-Pieistocene taxa, are more widely distribu- ted, belong to the deep-sea Mediterranean benthos and have an Atlantic or more generally oceanic affinity. In the present work, the first Mediterranean fossil records of two North Atlantic spirorbid species are di- scussed, together with an account of their present-day geographic distributions and ecology. Material and methods. The material examined (Fig. 1) originates from Early to Middle Pleistocene sandy deposits, cropping Istituto Policattedra di Oceanologia e Paleoecologia, Università di Catania, Corso ltalia 55,I-95L29, Catania, Italy, e-mail: rosso@mbox.unict.it 280 Fio I out in .western (Valle del Belice) and eastern (Augusta and Salice) Sicily, and from submerged Late Glacial sedi- ments in the Tyrrhenian Sea (canyon "del Toro"). The Valle del Belice section crops out along the right side of the Belice river, in south'western Sicily (Fig. 1). It consists of a biogenic sandy succession, ca.3.5 m thick, within a clayey sequence of uppermost Eariy Pleistocene age. The sands are highly fossiliferous, with corallinaceous algae, rhodoliths and molluscs. The spi- rorbid tubes were found in a bed with Arctica islandica. Palaeoecologic indications inferred from the benthic ma- crofaunistic assemblages, suggest an upper-circalittorai soft bottom (ca. 35-40 m depth) (Di Geronimo et al., 1994). Several species of North Atlantic origin are pre- sent. S. spirorbis (10 specimens) and S. corallinae (21 spe- cimens) are associated with other serpulids, i.e. Hydroi- R. Sanfi.lippo Fossil (closed symbol$ and Recent (open symbols) records of Spirorbis spirorbis (triangle$ and, Spirorbis corallinae (circle$. 1) Augu- sta; 2) Valle del Belice; 3) Salice; 4) Canyon del "Toro". des noroegicus, Spirobrancbus po/ytrema, Serpula concha- rum and Pomatoceros triqueter. Most S. corallinae tubes show a concave attachment surface, indicating grorÀ/th on articulate coralÌine stems (P1. 1, Fig. Z, 8), while some S. spirorbis tubes have flat attachment surfaces, suggesting that they may have been attached to kelp fronds. The Augusta outcrop is located along the left side of the Marcellino river (SE Sicily), ca.7 km S\l of Au- gusta (Fig. 1). It consists of an organogenic sequence of muddy-gravelly sands of uppermost Early Pleistocene age (Di Geronimo et al., in press), over 1 m thick, con- tained in bluish sandy muds. Palaeoecologic observa- tions from the sandy levels indicate a mid-shelf area (up- per Circalittoral) with palaeocommunities characterized by North Atlantic immigrant species, among which ,4. PLATE 1 Scale bar : 400 pm Fig. 1 - Spirorbis spirorbis (Linnaeus, 1758). Augusta, Early Pleistocene. Fig. 2 - Spirorbis spirorbis. Valle del Belice, Early Pleistocene. Fig.3 - Spirorbis coralLinae de Silva Ec Knight-Jones (1962), forming irregular ascending coils. Salice, Early Pleisrocene Fig. 4 - Spirorbis corallinae, with regularly flat coìls. Valle del Belice, Early Pleistocene. Fig. 5 Tube of Sptrorbis corallinae on a Corallina stem. Valle del Belice, Early Pleistocene. Fig. 6 - Tube of Spirorbis coraLlinae, attached on Corallina stem. Belice, Early Pleistocene. Frg.7 - Bioimmuration of Corallina stem lry Spirorbis corallinae. Augusta, Early Pleistocene. Fig. 8 - Detail of Frg. 7 showing casts of sporangiae. Pleistocene Soirorbid Pohchaetes in the Mediterranean 281 282 R. Sanfilippo islandica is dominant (Di Geronimo et al., in press). Some layers of the sequence supplied tubes of S. spiror- Als (6 specimens) and S. corallinae (14 specimen$. They are mostly detached from the original substrata, proba- bly coming from neighbouring shallower biotopes. Among the associated serpulids, Hydroides noraegicus is the more abundant species. Moreover, several tubes of an undetermined Circeis species occur. The Salice section crops out near the town of Sali- ce, ca. 15 km W of Messina (Fig. 1). The Middle Pleisto- cene outcrop (Di Stefano & Lentini, 1996) is an organo- genic sandy sequence, 13 m thick, overlying in uncon- formity limestones with bathyal corals. The sands are often cross-bedded and increase in muddy fraction upwards. The same two spirorbid species (13 S. spirorbis and 25 S. corallinae specimens) were obtained within some layers of the sands, becoming more abundant in their upper part. The associated benthic assemblages in- dicate an epibathyal palaeoenvironment swept by cur- rents, with infra- and circaiittoral elements transported down from shallower biotopes located on top of the steep sides of the palaeobasin. Faunas are characterised by species with a markedly Atlantic affinity (such as Neouermilia falcigera among serpulids). Placostegus tri- dentatus and Serpula lobiancoi are the dominant associa- ted serpulids. Some tubes of Circeis sp. are also present. S. corallinae tubes are usually detached from the substra- te, showing a concave area of attachment, suggesting an originai settlement on cylindrical substrata \ke Coralli- na. sÍems, S. spirorbis and S. corallinae were found also in a sample dredged from "del Toro" canyon, off southwe- stern Sardinia (Stn. DG03, 38o43.28'N, 8o20.59'8, I95 m). The sample consists of muds rich in oyster shells and scleractinians, indicating a Late Glacial age. S. spiror- bis and S. corallinae (both with 6 specimens) occur toget- her with deep circaiittoral and bathyal serprlids (Meu- verrnilia rnultioistau, Semioermilia agglutinaa, Hyalopo- matus oariorugosus and Filogranula stellau). As in the previous sample, spirorbids seem to have been displaced from the infralittoral environment, down to epibathyal depths. Some specimens of spirorbids are free in the mud, showing limited areas of attachment, as though they had been attached to comparatively thin srems of algae, hydroids or bryozoans. A stock of living specimens of S. spirorbls from Iceland, collected by Drs. P. and E.\L Knight-Jones, was used for observations and comparison of tube structu- res. They are densely settled on a blade of. Fwcus serratus. For SEM observations, before coating with gold palladium, fossil and Recent tubes were cleaned with FIzOz. Some tubes were broken to investigate the wall slructure. Tube morphology and structure. Differences between the tubes of S. spirorbi.s and S. corallinae are seemingly slight, both tubes being sini- strally coiled, smooth and similar in shape. Neverthe- less, careful observations of tube morphology allow a distinction at the species level to be made, even when only fossil material is available. Size is also similar, the outer coil diameter being ca. 2-3 mm in S. spirorbrs and 2-2.5 mm in S. corallinae. The opening is simple, without peristomes, in both spe- cies (Pl. 1, Figs. 1,,2,4). A weak sculpture occurs oniy in S. corallinae, consisting of wide-spaced rounded gros/th ridges, indica- ting the previous openings (P1. 1, fig. a). In S. spirorbls the outer edge of the tube spreads out to form a more or less evident peripheral flange (Pl. 1, Figs. 1,2). This feature is distinctive for S. spirorbis (see Rzhavsky, 7994), but lacking in S. corallinae, the cross section of which is regularly circular (Pl. 1, Figs. 3,4,5). When attached to the small and convex fronds of Corallina, a tube of S. corallinae grows often as irregular ascending coils (P1. 1, Figs. 3, 5, 6). On fronds of larger algae it is regularly flat and planispirally coiled. The tube diameter of the external coii does not increase ro- ward the opening (Pl. 1, Fig. a). The outer coil of S. spirorbis, however, lies partly over the inner ones and the tube diameter increases more rapidiy with growth (P1. 1, Figs. 1, 2). On the attachment surface of S. corallinae, on casts of Corallina stems and sporangia are often visi- ble (Pl. 1, fig. 7, 8). PLATE 2 Scale bar : 400 pm (Fig. 1),20 pm (Figs. 2-7) Fig. 1 - Spirorbis spirorbis on Fucus serratus. Iceland, Recent, F;- , - T."-."-..- .-^'l^'1 of tube wall of Spirorbis spirorbis sho*ing an inner chitinous layer, a mid opaque and an outer glossy calcareous layer. Iceland, Recent. Fig. 3 - Microstructure of the two calcareous layers. Opaque layer with crystals arranged in a criss-cross pattern. Outer glossy with isorienta- ted crystals. Iceland, Recent. Fig. 4 Detaii of outer glossy layer. Needle-like crystals, perpendicular to the outer surface. Fig. 5 - Detail of mid opaque layer. Crystals of prismatic shape and criss-cross arrangement. Fig. 6 - Transverse wall section of fossil Spirorbis spirorbis, with homogeneous structure without layers. Augusta, Early Pleistocene. Fig.7 - Detail of Fig. 6. Crystals have lost the original shape structure and have crowded together. Pl.2 PLeistocene Spirorbid PoLychaetes in the Mediterranean 284 R. Sanfilippo The tube wall of living S. spirorbis specimens has a glossy surface and is composed of two calcareous layers (P1. 2, fig. 2,3). The inner layer is opaque, ca. 50 pm thick, and with crystals arranged in a criss-cross pat- tern (Pl. 2, Fíg. 5); the outer iayer is porcellaneous or almost vitreous, ca. 20 1tm thick, with larger crystals, showing a common axis orientation. At higher magnifi- cation, crystals appear needle-like and perpendicular to the outer tube surface (Pl. 2, fig. 4). This kind of struc- ture results in transparency (Zlbrowius & ten Llove, 1,987). A third chitinous layer rarely occurs around the lumen of the tube (Pl. 2, Fig. 2). Several burrows, proba- bly by boring algae, are visible near the outer surface (P1. 2, Fig. 2). Fossii tubes of both species are thick and rather porcelaneous, with a glossy surface. They are always re- crystallized. SEM micrographs show a unique homoge- neous layer, 70 ptm thick, in which crystals are closely packed without a regular orientation (P1. 2, fig. 6, 7). The original wall structure is lost. Biogeography and ecology. The present geographic distribution of the two species investigated is Atlantic, north of latitude 40oN. S. spirorbis is a boreal-arctic species (Fig. 1), ran- ging from the Arctic Sea to the northeast coast of the U.S. (Knight-Jones e/ a1.,1.99t).It is frequent in the Cel- tic and North Seas (Knight-Jones & Knight-Jones, 1,977; Knight-Jones, pers. comm.). It was found also in the \X/hite and Barents Seas (Rzhavsky, 1,992). S. corallinae is boreal-arctic too, but less vzidely di- stributed, ranging from the Barents Sea (Rzhavsky, L992) to southern Brittany (Fig. t). It is particularly common in the Celtic Sea, from Ireland to the Scilly Isles (Knight-Jones & Knight-Jones, 7977). In the southern area of distribution of both spe- cies (English Channel) the mean bottom water tempera- ture is 6-10o C in winter and does not exceed 16" C in summer (Holmes, 1966). Both species are mesolittoral to upper infralittoral, occurring from rock pools to shallow depths (Knight-Jo- nes et al., 1975; Knight-Jones & Knight-Jones, 7977; Rzhavsky, 1992). They are mainly epiphytic on fronds of various algae. S. spirorbis typically settles on brown fucoids (especially Fucus serratus) but may occur also on kelps (Larninaria, Sacchorbiza) (Knight-Jones et ^1., I975)" S. corallinae settles almost exclusively on Coralli- na officinalis, and rarely on other red algae. Exceptional- ly it was found on the soft red alga Chondrus, in higher pools (Knight-Jones Er Knight-Jones, L977). Gregariou- sness is seen in both species and the larvae swim for no more than a few hours (Knight-Jones, 1951). The boreal distribution of S. spirorbis and S. coral- linae ís a character common to many species belonging to the genus Spirorbls Daudin. S. rupestris, S. inornatus and S. tridentatus are exclusively boreal (Knight-Jones et al., 1.991; Knight-Jones Ec Knight-Jones, 1995). S. striga- tus, as well as the recently described S. (Wlorbis) gesae, live in the Atlantic at midlatitudes (off west Africa). Only three species live in the Mediterranean: S. infundi" bulum, which is probably endemic, S. cuneatus which lives also in NE Atlantic, and the circumtropical S. (Spi rorbella) marioni, whose recent introduction into the Mediterranean was by ship transporr (Zibrowius & Bianchi, 1981). The last species, and three other easrern Pacific spirorbids (5. spatulatus, S. bifurcatus, S. rothlisber- gi) are dextraily spiraled. Oniy two other Spirorbis are tropicai, S. placophora and S. bidentatus, the former known only from the Galapagos and the latter having a circumtropical distribution (Knight-Jones et al., 1991). In the fossil assemblage the associatio n of S. spiror- bis and S. corallinae with a deep water fauna can be ex- plained easily by post-mortem down slope displacement from shallower bottoms. It is very unlikely that these shallow water spirorbids were fossilized within their ori- ginal environment, exposed to dispersing.wave action. Discussion. The present boreal and arctic distribution of S. spirorbis and S. corallinae, here reported as Pleistocene fossils, suggests significantly colder conditions than to- day. Their immigration into the Mediterranean Pleisto- cene probably took place by a gradual southward expan- sion of their biogeographic range, in step with the pro- gressive cooling. The movement of their populations into the Mediterranean would have been helped by their short planktonic larval phase and gregariousness during settlement. S. spirorbis and S. corallinae probably made a relatively "late" appearance in the Mediterranean during the cold Pleistocene. They are recorded from sediments not older than the uppermost Early Pleistocene (Sicilian age), corresponding to the third molluscan migration flood (Raffi, 1986). As already srressed by Buccheri (1985) this age couid be correlated to the first cold Plei- stocene peak recognised by Shackleton & Opdyke (lZe) at abour 0.8 Ma. A similar southward movement of Spirorbis was invoked to explain the recent finding of a species which may be endemic to Madeira, S. (Wlorbis) gesae Kníght- Jones & Knight-Jones (1,995). This is quite like S. spiror- bis, and the authors suggest that a common ancestor of both species may have reached Madeira during an ice age, and that S, (Wlorbts) gesae may be its modified de- scendent. As mentioned above, tubes of Circeis and of the serpuiid H. noruegicui occur together with the fossil Spl- rorbis snder study. Circeis is a circumboreal spirorbid genus, quite common in northeastern Atlantic infralitto- ral waters, but not represented in the present-day Medi- terranean (Knight-Jones & Knight-Jones, 1977). It may thus have the same palaeoclimatic significance as the two other spirorbids. H. noraegicus, still common in the Recent Mediterranean (Zibrowius, L972), appears more abundant in Pleistocene mid-shelf deposits. This could also suggest lower Pleistocene temperatures. The diagnostic value of shape and other morpho- logic features of spirorbid tubes is demonstrated here. Identification at the species level is possible only when empty or fossil tubes are available. SEM observations of the tube wail of S" spirorbis show a particular micro- structure, not observed in other spirorbids (two distinct Pleistocene Spirorbid Polychaetes in tbe Mediterranean 285 layer$. This suggests that at least in Recent materiai, not affected by diagenetic changes, tube microstructure can also be a diagnostic character at the species level. Achnouledgements. I am greatly indebted to P and E. W. Knìght-Jones (Depanment of Zoology, Swansea) for constructive comments and loaned material. I also thank H. Zibrowius (Stat. Mar. Endoume, Marseille) for critical review of the manuscript, S. Di Geronimo (Istituto Policattedra dì Oceanologia e Paleoecologia, Catania) for useful suggestions and O" Torrisi (C.N.R., Catania) for assrstance rn SEM observations. This paper was supported financially by 40/o (Di Geronimo) M.U.R.S.T. erants. REFERENCES Buccheri G. (1985) - Osservazioni paleoclimatiche al limite Pleistocene inferiore-Pleistocene medio della foce del Belice (Sicilia sud-occidentale) mediante l'uso degli Pte- ropodi. Boll. Soc. GeoL. It., v. 104, pp. 1L5-1.22,F.orr'a. Di Geronimo L (1974) - Significato paleoecologico di CyLi- chna alba nuovo "ospite nordico" del Pleistocene deila Sicilia. Mem. Mus. Cia. St. Nat. Wrona, v. 2a, pp. 569- 572, Yerora. Di Geronimo I., Costa 8., La Perna R., Randazzo G., Rosso A. 8c Sanfilippo R. (199a) - The Pleistocene "Case Cata- rinicchia" Section (Belice, S\l Sicily). Studies on Ecolo- gy and Paleoecology of Benthic Communities. R. Mat- teucci et al. (eds.), Boll. Soc. Paleont.1r., Vol. Spec. 2, pp. 93-L15, Modena" Di Geronimo L, Di Geronimo R., La Perna R., Rosso A. Ee Sanfilippo R. (in pres$ - Cooling evidence from Pleisto- cene shelf assemblages in SE Sicily. Proc. European Pa- leontological Congress, lt;Jy 1997, lù/ten. Di Stefano A. & Lentini F. (1996) - Ricostruzione stratigrafica e significato paleotettonico dei depositi pleistocenici del margine tirrenico tra Villafranca Tirrena e Faro (Sicilia nord-orientale) . Studi Geologici Camerti, vol. spec. n. 2, pp. 21.9-237, Camerino. Flolmes N. (1966) - The bottom fauna of the Engiish Chan- nel J. Mar. Biol. Ass. U.K., v. 41, pp.397'461, [,ondon. Knight-Jones E.\f. (1951) - Gregariousness and some other aspects o{ the settling behaviour of Spirorbis. J. mar. bioL. Ass. U.K, v. 3, pp. 201,-222, I-ondon. Knight-Jones P., Knight-Jones E.'W. & Al-Ogily S.M. (1975) - Ecological isolation in the Spirorbtdae. Proc. 9th Europ. mar. biol. Sy*p., pp. 539-561,, Aberdeen. Knight-Jones P. & Knight-Jones E.\L (1977) - Taxonomy and ecology of British Spirorbidae (Polychaety'. J. rnar. bioL. Ass. IJ.K., v. 57, pp. 453-499, london. Knight-Jones P., Knight-Jones E.\L & Buzhinskaya G. (1991) - Distribution and interrelationships of northern spiror- bid genera. BulL Mar. Science, v. 48, n. 2, pp. 189-197. Knight-Jones P. 8c Knight-Jones E.'SL (1995) - Spirorbidae (Polychaeta) from Madeira including a new species and subgenus of Spirorbis. Mitt. hamb. zool. Mus. Inst^, v" 92, -^ eq_1n1 l-l"-h,,,^ ^*^.^- *rg. Malatesta A.. k Zarlenga F. (1986) - Northern guests in the Pleistocene Mediterranean Sea. GeoL. Romana, v. 25, pp. 9l-154, Roma. Mars P. (1963) - Les faunes et la stratigraphie du Quaternaire Méditerranéen. Réc. Tia<.,. Stat. Mar. Endoumo v 2R- nn 61-97, Marseille. Raffi S. (1986) - The significance of marine boreal molluscs in the Early Pleistocene far,rnas of the Mediterranean area. Palaeogeogr. Palaeoclim., Palaeoec., v. 52, pp. 267- 289. Amsterdam. Raffi S. Ec Marasti R. (1982) - The Mediterranean bioprovince from the Pliocene to the Recent: observations and hypotheses based on the evolution of the taxonomic di- versity of moiluscs. In: Paleontology, essential of histo- rical geology, Proc. Int. Meet. Venice 1981, E. Montana- ro Galitelli (Ed.), pp. 151-177, Mucchi, Modena. Ruggieri G., Buccheri G., Greco A. & Sprovieri, R. (1,976) - Un affioramento di Siciliano nel quadro della revisione della stratigrafia del Pleistocene inferiore. BolL. Soc. Geol. It., v. 94, pp. 889-914, Roma. Ruggieri G., Rio D. & Sprovieri R. (198a) - Remarks on the chronostratigraphic classification of Lower Pleistocene. Boll. Soc. Geol. lL., v. 103. pp. 251-259, Roma. Rzhavsky A.V. (L992) - Review of Circeinae and Spirorbinae (Polychaeta, Spirorbidae) from seas of USSR with a de- scription of a new species, Circeis gurjanotae. Zool. Zhurn., v.7 L n.7. pp. 5-13. Moscow. Rzhavsky A.V. (1994) - On the morphoecology of spirorbid trbes. Ophelia, v. 39, n. 3, pp. I77-182, FIelsrngor. Shackleton N.J. e. Opdyke N.D. (1976) - Oxygen-isotope and Paiaeomagnetic Stratigraphy of Pacific core Y28-239 Late Pliocene to Latest Pleistocene. Geol. Soc. Am. Mem. v. 145, pp. 449-484. 286 Taviani M., Bouchet P., Metivier 8., Fontugne M. Er Deli- brias G. (1991) - Intermediate steps of southq/ards fau- nai shifts testi{ied by last glacial submerged thanatocoe- noses in the Atlantic Ocean. Palaeogeogr., Palaeoclimat., Palaeoecol., v. 86, pp. 331,-338, Amsterdam. Zibrowius H. (1,972) - Hydroides noroegica Gunnerus, Hydroi- des azorica n.sp. et Hydroides capensis n. sp. (Polychaeta Serpulidae), espèces vicariantes dans l'Atlantiqre. Bull. Mu* Hist. nat., Paris, s. 3, v. 39 (33), pp. 433-446,Paris. Zibrowius H. (1979) - Vitreotubus digeronimoi n. g., n. sp. (Polychaeta Serpulidae) du Pléistocène inférieure de la Sicile et de l'étage bathyal des Agores et de l'Océan In- dien. 7étlrys , v. 9, n. 2, pp. 183-190, Marseille. Zibrowius H. Ec Bianchi C.N. (1981) - Spirorbis rnarioni er Pileolaria berkeleyana, Spirorbidae exotiques dans les ports de la Médlterranée nord-occidentale. Ropp. Comm. int. Mer Mèdìt., v. 27, pp. 763-t64, Monaco. Zibrowius H. & ten Hove H. (\987) - Neoztermilia faLcigera (Roule, 1898) a deep- and cold- water serpulid polychae- te common in the Mediterranean Plio-Pleistocene. BuLL. Biol. Soc. Wash., v.7, pp. 259-271, \Tashington. R. San/ìlippo