Spinucella a New Genus of Miocene to Pleistocene , Muricid Gastropods from the Eastern Atlantic

Contr. Tert. Quatern. Geol. 30(1-2) 19-27 1 tab., 1 pi. Leiden, June 1993 Spinucella a new genus of Miocene to Pleistocene , muricid gastropods from the eastern Atlantic Geerat J. Vermeij University of California Davis, U.S.A. — new of Miocene Pleistocene muricid from the Atlantic. Contr. Tert. Vermeij, GeeratJ. Spinucella, a genus to gastropods eastern Quatern. Geol., 30(1-2): 19-27, 1 tab., 1 pi. Leiden, June 1993. The muricid is for de C. 1825 from the Pliocene of the new gastropod genus Spinucella proposed Purpura tetragonaJ. Sowerby, (type species), North Sea Basin, and for several other early Miocene to late Pleistocene species from southern Europe, North Africa, and southern Africa. The is characterised the of labral on the of the shell and reticulate of genus by presence a spine outer lip by sculpture. Species and Acanthinucella Cooke, 1918. The Spinucella closely resemble members ofNucella Röding, 1798, Acanthina Fischer von Waldheim, 1807, ofthat in the eastern Pacific Acanthina andAcanthinucella. Withthe removal of labral spine of Spinucellawas probably evolved independendy from where authors have the the time of arrival of Nucella in the North Atlantic from the S. tetragona Nucella, many recent placed species, North Pacific was late Pliocene, rather than middle Pliocene. — words Key Spinucella, new genus, Acanthina, Nucella, Neogene, biogeography. Prof. Dr G.J. Vermeij, Department of Geology, University of California, Davis, CA 95616, U.S.A. Contents 1956; Glibert, 1959, 1963). In fact, Glibert (1959) considered N. tetragona to be ancestral to N. lapillus, Introduction 19 p. the two species being linked by the late Pliocene 20 Systematics p. taxon N. lapillus incrassatus (J. de C. Sowerby, 1825). Comparisons p. 21 According to this interpretation, N. tetragona would Evolutionary and biogeographical be the earliest species of the genus in the North 22 relationships p. Atlantic, and invasion of Nucella from the Pacific, Acknowledgements p. 24 where be traced back the Nucella can to early References p. 24 would have taken later than Miocene, place no middle Pliocene time (Crothers, 1983; Vermeij, Introduction 1991). muricid Nucella The gastropod genus Roding, 1798, Authors who regard Purpura tetragona as a species have overlooked several characters that comprises eight or nine cool-temperate species of Nucella found intertidal and shallow this all other members abundantly on rocky distinguish species from of surfaces in the northern Its sublittoral oceans. type that genus. In our study of the phylogeny of Nucella & in P. species, Nucella lapillus (Linnaeus, 1758) (see Kool (Collins et al., prep.), we found that tetragona both the and small but distinct labral Boss, 1992), occurs on European possesses a spine, a ventral of and is the American sides the Atlantic, only living projection at the anterior end of the outer lip of the of the in North Atlantic shell. This feature representative genus waters. is characteristic of Acanthina All other in the North Pacific. Several Fischer 1807. species occur von Waldheim, Lecointre (1952), who have also been to Nucella. other species assigned considered Acanthina to be a subgenus of Nucella (or These include four and Pliocene in living one species Purpura his terminology), assigned P. tetragona, from South Africa (Kilburn & Rippey, 1982; Ken- along with several other Pliocene and Pleistocene sley & Pether, 1986) and the Pliocene species origi- species from Morocco and southern Europe, to described de C. Acanthina A. monodon nally as Purpura tetragonaJ. Sowerby, [type species: (Pallas, 1774)]. Basin of One of the Morocco considered 1825, from the North Sea western Europe species from was by Altena Lecointre be (see Harmer, 1914-1921; van Regteren et al., (1952) to specifically indistinguishable 20 from A. monodon unicornis (Bruguiere, 1789) (A. Netherlands, S. tetragona is found washed up on beaches in in crassilabrum Lamarck in Lecointre's terminology), the estuary of the Westerschelde the from southern South America. province of Zeeland (van Regteren Altena et al., A of and of It therefore has re-examination Purpura tetragona var- 1956). a geological range of middle ious other species assigned to Nucella, Acanthina, and to late Pliocene. related indicates the existence of The shell of is groups an early Spinucella tetragona moderately large Miocene to late Pleistocene lineage of eastern (up to 63 mm in length), characterised by a rela- Atlantic muricids possessing a labral spine and reti- tively high spire, long siphonal canal, well-marked culate The of this is rounded sculpture. purpose paper to pseudo-umbilical slit, a columella, a deep and this the short labral and latticed recognise name lineage as new genus suture, a very spine, strong with and dis- of six cords crossed Spinucella, Purpura tetragona as type, to sculpture consisting major spiral the and fifteen axial folds cuss characters, evolution, biogeographical by as many as (PI. 1). of this and sim- relationships group morphologically A second well-characterised species is S. plessisi ilar muricids. (Lecointre, 1952) from the late Pliocene to late Atlantic Pleistocene of the warm-temperate eastern SYSTEMATICS (PI. 1, Fig. 5). This species had a range from near Lisbon (Portugal) to Morocco and the Canary Family Muricidae Rafinesque, 1815 has Islands; a single (presumably fossil) specimen Subfamily Ocinebrinae Cossmann, 1903 been collected in sediment near Cape Bojador, Genus Spinucella nov. gen. Spanish Sahara (see Brebion, 1974, 1979a, b; Meco, — Type species Purpura tetragona J. de C. Sowerby, 1981). Spinucella plessisi is rather variable in shape 1825, here designated. and in the development of shell sculpture. Almost — shorter smooth forms called Diagnosis Shell ovate; spire than adult were Purpura (Acanthina) body whorl; teleoconch whorls four to five in crassilabrum Lam. by Lecointre (1952). More heavily rounded with of number, evenly or slightly shouldered; sculptured forms a reticulate sculpture spiral of both and axial and axial ribs named P. sculpture spiral elements; spiral were (A.) plessisi, P. nicklesi, ribs and P. nicklesi all of Lecointre usually broad, up to seven primaries on body var. imsouanensis, whorl, with intercalated secondary ribs and finer (1952). Brébion (1974, 1979a, b) and Meco (1981) axial ribs form reticulate all these forms under the threads; a or latticed pat- justifiably synonymised with the earliest available tern spiral sculpture; aperture ovate; junc- name, P. (A.) plessisi Lecointre, tion of outer lip with body whorl continuous, with- 1952, which is here placed in Spinucella. S. plessisi sinus of base differs from S. the absence of out posterior or notch; edge outer lip at tetragona by a pseudo- canal with short labral formed umbilical of siphonal spine, as slit, by having a lower spire, and by hav- an elaboration of one of the denticles on the inner ing the suture indistinct rather than deeply surface of the outer lip; outer lip slightly thickened, impressed. denticulate within, the denticles developed close to Perhaps the earliest representative of Spinucella is of the columella less S. from the middle the edge lip; more or straight, angulata (Dujardin, 1837) sometimes flattened, lacking folds; siphonal canal Miocene (Helvetian = Tortonian) of France. This visible shell's differs from other members of the open, its trace on the exterior as a species most fasciole often from the base its small size of adults 34 prominent separated by genus by (length up to mm) slit. and its of six to thick axial a pseudo-umbilical by sculpture seven very Geographical and stratigraphical distribution — Early ribs, which form nodes where they are crossed by five six Miocene to late Pleistocene; North Sea Basin to or closely spaced spiral cords. The upper- cord weak southern Africa. most spiral forms a shoulder, above — The of S. which the axial ribs towards Included species type Spinucella is tetragona straight slope the indis- (J. de C. Sowerby, 1825), which has been recorded tinct suture. in England from the Coralline Crag at Ramsholt Several other southern European species from the and from the Red Miocene and Pliocene throughout Crag (Waltonian, appear to belong to Spi- Newbournian, and Butleyan) (see Harmer, nucella. These include S. monacanthos (Brocchi, 1814) 1914-1921; Glibert, 1963). In Belgium the species is from the Pliocene of Italy, S. depressa (Bronn, 1831) known from the Oorderen Sands Member of the from the Pliocene of Italy, S. cancellata (Bellardi, Lillo Formation (Glibert, 1958, 1959). In The 1882) from the early and late Miocene of Italy, S. 21 S. from Helvetian whereas in Nucella they are deeply benoisti (Degrange-Touzin, 1895) the Spinucella, The inner surface of the ofNucella of France, and S. lesvignesi (Cossmann & Peyrot, recessed. outer lip In the the of France. It is doubtful is thus bevelled, whereas in Spinucella it is not. 1923) from Tortonian distinct but I third the lattice-like characteristic that all these names refer to species, place, sculpture in In of of these of does not occur Nucella. have not undertaken a critical review taxa. Spinucella species either Nucella with axial elements, the latter are Another species that appears to belong to Spi- in thick-shelled of nucella is the Pliocene South African S. praecingulata discrete knobs, as some morphs from from the west coast of N. (Deshayes, 1839) California, or (Haughton, 1932), described emarginata that override the This which reaches a are irregularly spaced flanges Cape Province. large species, they

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