THE NAUTILUS 111(1):1-12, 1998 Page 1 Amrnonicera in Florida: Notes on the Smallest Living Gastropod in the United States and Comments on Other Species of Omalogyridae (Heterobranchia) r .. 1•. If I Rudiger Bieler Paula M. Mikkelsen Center for Evolutionary and Environmental Biology Field Museum of Natural History Roosevelt Road at Lake Shore Drive Chicago, Illinois 60605, U.S.A. bieler@fmnh.org Department of Invertebrates American Museum of Natural History Central Park West at 19th Street New York, New York 10024, U.S.A. mikkel@amnh.org ABSTRACT The first record of a species of Ammonicera in Florida, with an additional record from Yucatan, Mexico, is presented and the gross morphology of the living animal is described for the first time. This smallest living snail in the United States is identified as Ammonicera minortalis Rolan, 1992, originally described from Cuba. Comparisons are made with closely similar species, especially A. japonica Habe 1972, a possibly conspecific form with known wide distribution in the Pacific Ocean. Various taxonomic problems in the genera Ammonicera and Omalogyra are addressed, and current composition of the family Omalogyridae is discussed. Lists of currently recognized omalogyrid species in the Atlantic Ocean (including the Mediterranean Sea) are presented. Key words: Florida Keys, Gastropoda, lower Heterobranchia, Ammonicera, Omalogyra, Omalogyroidea, Atlantic Ocean, Systematics. INTRODUCTION The family Omalogyridae is a poorly known group of extremely small marine snails. Placed in their own superfamily Omalogyroidea, they are currently classified as members of the unresolved "lower heterobranch" gastropods (e.g., Haszprunar, 1988; Bieler, 1992; Healy, 1993). Even the most basic taxonomic and distributional information is sketchy for this group, with most faunistic studies missing or deliberately omitting the usually lessthan-one-millimeter size range of the adult shells. The few studies that have concentrated on this group have brought many new species to our attention, such as the recent series of works with excellent scanning electron micrographs by Sleurs of omalogyrids in Papua New Guinea (1983) and in the Republic of Maldives (1985b), by Palazzi (1988) in the Mediterranean and Madeira, and those by Rolan in the Cape Verdes (1991) and Cuba (1992). Whether these areas are exceptional in their high species diversity of omalogyrids is doubtful, although it is surprising that no true omalogyrids were reported in some Caribbean studies that otherwise dealt with minute species (e.g., De Jong & Coomans, 1988; Rios, 1994). In addition to their small size, omalogyrids have anatomical features that set them apart from caenogastropods with which they were usually grouped. This led to early speculations about their systematic position. Because of their unusual radular characters, G. 0. Sars (1878) placed the at the time monotypic family as the only member of his new higher taxon "Prionoglossa," giving it equal rank with other groups such as Taenioglossa and Ptenoglossa. Jeffreys (1859a) thought these animals the only surviving members of the otherwise extinct genus Euomphalus Sowerby, 1814. Fretter (1948) showed in a detailed anatomical study that Omalogyra atomus (Philippi, 1841) differs greatly from the "prosobranchs" with which it was traditionally placed. Omalogyrids have regained interest in recent years because of their presumed basal position within the heterobranchs (Haszprunar, 1988; Ponder, 1990, 1991). Their exact relationships remain uncertain; recent suggestions (Bandel, 1996; Pacaud & Le Renard, 1996) to combine the Omalogyridae with several other families in a superfamily Architectonicoidea are not supported by anatomical data (Healy, 1993; Huber, 1993). At the nomenclatural level, certain confusion exists in the literature about the usage of genus-group names such as Ammonicera versus Ammonicerina, and about the identity and authorship of Oma.logyra's type species. The discovery of an Ammonicera species in the Florida Keys, representing the smallest gastropod known in the United States, is here used to summarize existing data on Omalogyridae in the Atlantic Ocean and to address additional taxonomic problems. Page 2 ABBREVIATIONS USED American Museum of Natural History, New York, U.S.A. BMNH The Natural History Museum, London, United Kingdom FMNH Field Museum of Natural History, Chicago, U.S.A. MLP Museo de La Plata, Argentina MNCN Museo Nacional de Ciencias Naturales, Madrid, Spain MNHN Museo Nacional de Historia Natural, Santiago, Chile ZMB Zoologisches Museum, Humboldt Universitat, Berlin, Germany SEM Scanning Electron Micrograph AMNH RESULTS Family Omalogyridae G. 0. Sars, 1878: 215 [as Homalogyridae] (often erroneously credited to Fischer, 1885; e.g., Abbott, 1974) Genus Ammonicera Vayssiere, 1893 Ammonicera minortalis Rolan, 1992 (Figures 1-8) Omalogyra species.-Vokes and Vokes, 1984: 168, figs. 7, 7a (SEM). Ammonicera minortalis Rolan, 1992: 40, 42, figs. 10, 11 (teleoconch), 13, 15 (protoconch) (all SEM). Holotype: (MNCN 15.05/6794): shell diameter 0.35 mm; type locality: north of Cuba, Baracoa; holotype from 4 m depth. Type material studied: 3 paratypes, AMNH 226450, from type locality. Florida material studied: 2 Florida Keys specimens collected and observed alive, one each from station FK045 [Indian Key Fill, Mile Marker 79, Monroe County, 24°53'25"N, 80°40'28'W, Gulf side, rocks in 0.5--1 m among Thalassia/Halodule seagrasses, 20 September 1996] and station FK-062 [Missouri Key, Mile Marker 39.5, Monroe County, 24°40'29"N, 81°14'2l'W, Gulf side of Missouri-Ohio Key bridge, subtidal rocks, 14 April 1997]. Also empty shells from sta. FK-040 [Missouri Key site as above, 12 March 1996], FMNH 279010 (1 shell); FK-057 [Missouri Key site as above, 26 September 1996], FMNH 279011 (10 shells incl. SEM material), AMNH 288137 (5 shells). All localities were fully marine and were sampled by the authors by "rock washing" (brushing and rinsing of rock surfaces). Distribution: Now known from north and south coasts of Cuba (Rolan, 1992), the Florida Keys (this paper), and the Yucatan Peninsula (Vokes & Vokes, 1984). Description: Shell (Figs. 1-2) extremely minute, diameter 0.34-0.46 mm (0.2-0.4 mm, fide Rolan, 1992), planispiral, tightly coiled, glossy, uniformly dark brown, resembling a miniature ammonite in shape and sculp- THE NAUTILUS, Vol. 111, No. 1 ture. Protoconch (Figs. 3-4) of 1.3 whorls• (identical in SEM but described as "3/4 whorl," by Rolan, 1992), diameter 120-135 µm, distinctively sculptured with one major spiral cord at mid-whorl, reticulate sculpture peripheral to major cord, and 3-4 smaller spiral ridges central to major cord. No distinction of a separate larval shell ("protoconch II"), indicating the absence of a free swimming larval stage. Coiling near-planispiral, with slight initial hyperstrophy (compare Figs. 3 and 4). Teleoconch of about 1.3 rounded whorls (1-1.5 whorls fide Rolan, 1992), sculptured with prominent elongated axial tubercles, regularly spaced, equally sized, beginning immediately after protoconch, numbering 15--19 (13-17 fide Rolan, 1992) on body whorl, fading to no axial sculpture at the periphery. Tubercles and spaces between also with fine growth lines. Periphery (Fig. 6) uniformly rounded, smooth except for fine growth lines. No distinct spiral sculpture (but occasionally with extremely fine lines, see specimen in Fig. 1). Outer lip (Figs. 1-2) thin, sharp, ending in a single plane perpendicular to the plane of coiling; aperture circular; columella without folds or grooves. Head-foot (Figs. 7-8) translucent to nearly transparent. Animal gliding rapidly on short foot, with blunt, very active propodium. Shell held nearly vertically as the snail crawls. Transparent operculum on hindfoot serving as a support for the coil of the shell. Head with two finger-shaped tentacles, each held in an erect arch curving toward the midline; eyes black, near base of tentacles. Radula and internal anatomy not studied. Habitat: Animals not observed in situ, but collected from shallow subtidal rocks covered on one or several surfaces with various polychaete worm tubes, marine algae, sponges, tunicates, and numerous other attached or free-living mollusks. Diet unknown (but see below). Remarks: Although the diet of Ammonicera minortalis has not been confirmed, it is likely to feed on the variety of algal species growing in its subtidal rock habitat, based on literature records on the habitat/diet of other Omalogyridae: on Codium and Zostera (Omalogyra atomus [as Euomphalus nitidissimus ]-Jeffreys, 1859a, 1859d); on Ulva (0. atomus-Fretter, 1948); on Fucus (A. rota-Nordsieck, 1972); on Ulva and Enteromorpha (0. atomus-Fretter & Graham, 1978; Graham, 1988); on Fucus, Laminaria, Cladophora, Corallina, Ulva (Ammonicera rota-Fretter & Graham, 1978); on Padina (Hawaiian A. japonica-Kay, 1979); piercing algal cells and sucking out the contents, and depositing egg strands on bases of Cladophora (A. rota I A. fischeriana-Franc, 1948; Graham, 1988); on Halimeda (A. japonica and others-Sleurs, 1985a, 1985c); on liJstera, Ulva, Cystoseira, and epiphytic diatoms (0. atomus, A. fischeriana-Gaglini, 1993). Bullock et al., 1990, provided the most detailed account, reporting Azorean 0. atomus and A. fischeriana from a variety of algae, including 1 Ascertained using the method of Taylor as summarized by Jablonski & Lutz (1980: 330, fig. 4) R. Bieler and P. M. Mikkelsen, 1998 Page 3 Figures 1-6. Ammonicera minortalis, shells by scanning electron microscopy (four different shells, FM H 279011 ). 1. Apical view. 2. Umbilical view. 3 . Protoconch (detail of fig. 1). 4. Protoconch (detail of fig. 2). 5. Ape rh1ral view. 6. Dorsal view (from .. above," as seen in crawling animal). Scale bars: Fig. 1 = 100 µm (Figs. 2, 5, 6 at same scale); Fig. 3 = 20 µm (Fig. 4 at same scale). THE NAUTILUS, Vol. 111, No. 1 Page 4 Additional specimens were described and illustrated as Ammonicera japonica from Hawaii by Kay (1979:92, figs. 32A-C [SEM], as Omalogyra; earlier reported by Kay & 7 8 Figures 7-8. Ammonicera minorlalis, sketch of living animal. Maximum shell diameter = 0.42 mm. 1. Right lateral view. 8. Dorsal view. Enteromorpha, Cystoseira, Ulva. Pterocladia, Peysonnelia, Halopteris, Asparagopsis, as well as Codium. Omalogyra atomus, which they also found on Gelidium and Sargassum, was the dominant species on Chondria and the only mollusk found on Fucus in that study. DISCUSSION Species-level identification: Rolan (1992) described this species based on empty shells collected from north and south coasts of Cuba (3-20 m). A comparison with the excellent original illustrations and with paratypic material at AMNH proved the identity of the Florida Keys specimens. No other lmown Atlantic species combines . such axial teleoconch sculpture with reticulated sculpture of its protoconch. Rolan apparently was unaware of an earlier record of this form, as "Omalogyra species," by Vokes and Vokes (1984) who collected it in Arrecife Alacran, about 140 km nm::th of Progreso, Yucatan, in the Gulf of Mexico. According to Rolan (1992: 42), only Ammonicera japonica Habe, 1972, described as "Japan's smallest gastropod" from Honshu, is "superficially similar but it has very constant spiral striae." Habe's species (1972:115116, figs. 1-4) was described as 0.42-0.68 mm in diameter, dark brown in color, with "about 16 annulations in the body whorl" (Habe, 1972:116). Habe did not mention or illustrate the spiral sculpture noted by Rolan. Switzer, 1974:278, table 1, from Fanning Island). Kay mentioned sculpture "from 16 to 18 axial ribs on the last whorl, the ribs becoming obsolete at the periphery." Spiral striae were not described but faint spiral sculpture is visible in one illustrated shell (Kay, 1979:fig. 32B). Sleurs' (1985a:4-5, pl. 1, figs. 1, 6, 9 [SEM]; as Omalogyra) description of A.japonica from Papua New Guinea was very similar. He described the protoconch in detail "with reticulated sculfture at the abapical side" (his fig. 9); spiral sculpture o the 0.3 to 0.45 mm large teleoconch was not discussed, but shows very faintly in one SEM illustration (his fig. 6). Fukuda's illustration of this species from the Ogasawara (Bonin) Islands (1994:pl. 35, fig. 697a-c; as "Omalogyla" japonica), shows no spiral sculpture. The large specimen illustrated (0.4 mm) has about 19 axial ribs. The protoconch and teleoconch sculpture of the shells of Ammonicera minortalis and A japonica are extremely similar according to the SEMs provided by Rolan (1992), Kay (1979), Fukuda (1994) and Sleurs (1985a), respectively, and suggest synonymy of the Caribbean and IndoPacific species. Faint spiral teleoconch sculpture appears to occur in some individuals of both nominal species. However, the disjunct distributional pattern makes further study necessary. No similar form has been described or recorded from the eastern Pacific (Shasky, 1989). As also noted by Rolan (1992), Ammonicera minortalis is similar to the European A. rota (Forbes & Hanley, 1850) in its teleoconch characters (but the latter has a greater number of whorls and axial tubercles continuing over the periphery). Ammonicera rota has, however, a very different protoconch without reticulated sculpture (see, e.g.• Rodriguez Babio & Thiriot-Quievreux, 1974: pl. 2, F -H; as A fischeriana). Also similar is A plicata Sleurs, 1985, from the Maldives (1985b:20 ff., figs. 2, 7, 10, 13, 14), which has a larger teleoconch (0.45 to 0.65 mm) with weaker axial ribs and a protoconch lacking the reticulate sculpture present in A minortalis and A. japonica. Genus-level identification: Omalogyridae currently comprises three recognized extant genera: Ammonicera Vayssiere, 1893, Omalogyra Jeffreys, 1859, and Retrotortina Chaster, 1896. The last (with type species by monotypy: R. fuscata Chaster, 1896) has a sinistral teleoconch that distinguishes it from Ammonicera and Omalogyra. Bandel (1988:9) also placed Orbitestella Iredale, 1917, in this family, but Ponder (1990) showed that this genus belongs in the Valvatoidea, not Omalogyroidea. Bandel (1988), who viewed omalogyrids as small-bodied members of Architectonicidae or Architectonicoidea (pp. 10, 17), attempted to introduce a new fossil genus "Neamphitomaria,,. but did not designate a type species. Bandel (in Dockery, 1993:92) subsequently provided such a R. Bieler and P. M. Mikkelsen, 1998 designation (the Upper Cretaceous Pseudomalaxis stantoni Sohl, 1960) and thus validated Neamphitomaria of that date [not as of 1988 as is frequently cited; see ICZN Art. 13(b)]. Amphitomaria Koken, 1897, and Neamphitomaria Bandel, 1993, were then placed in a new family, Amphitomariidae, by Bandel (1996), thus removing the genus again from the Omalogyridae. The placement of the present species in the genus Ammonicera, rather than Omalogyra, is here accepted because of: (1) its protoconch sculpture with strong spiral ribs and grooves (in contrast to small tubercles in Omalogyra; e.g., Rolan, 1992); (2) the presence of distinct cephalic tentacles (absent in Omalogyra); and (3) its strong teleoconch sculpture (absent or weak in Omalogyra ). The known radulae of Omalogyra and Ammonicera (not yet studied for A. minortalis) are so different between members of the two nominal genera that Sleurs (1985c:l81) suggested that they might belong to different families. However, published radular data differ even within the two genera: Omalogyra radulae have been described as either uniserial (Jeffreys, 1859, 1867; Thiele, 1929; Sleurs, 1985c) or with a formula of 1-1-1 (G. 0. Sars, 1878; Thiele, 1929; Egorova, 1991). Those of Ammonicera have been described with a formula of 1-1-1 (Vayssiere, 1893) or 1-1-0-1-1 (Sleurs, 1985b, c), and so definitive conclusions must await a detailed comparative study. Unfortunately, the taxonomic history of Ammonicera, Omalogyra, and their included species is exceedingly complex and confused (see discussion below). REMARKS ON AMMONICERA AND ITS TYPE SPECIES Ammonicera was introduced by Vayssiere (1893:16 ff.) for Homalogyra fischeriana Monterosato, 1869. He provided a full anatomical description based on histology and studies of the radula. Franc (1948:142 ff.) and Sleurs (1985a:9) questioned the identity of Vayssiere's material, assuming that his work was based on misidentified "Omalogyra rota" Forbes and Hanley, 1850. Compared to Gaglini's descriptions and illustrations (1993:933-04, 934-03-04), Vayssiere's line drawings of the shell (1893: figs. 8-9) seem to represent typical A. fischeriana in color pattern and relatively fine crenulations of the periphery, although the sketched pronounced axial ribbing is more representative of the nominal species A. rota. Monterosato himself considered the two nominal species as varieties of one (e.g., Monterosato 1872:38; 1875:29), and many recent authors (e.g., Fretter & Graham, 1978; Backeljau et al., 1984; Knudsen, 1995) have deemed them synonymous (see also Hoisaeter, 1968; van Aartsen et al., 1984). Gaglini (1993), on the other hand, argued convincingly for the presence of two sympatric species. Whether or not they will prove to be synonymous, they are without doubt so closely related and morphologically similar that it will not impact interpretation of the nominal genus Ammonicera (in contrast to Sleurs, 1985a). In addition to Vayssiere's extensive description, pub- Page 5 lished biological information about this/these species includes description of gross anatomy (Franc, 1948), nervous system (Huber, 1993), egg capsules (Franc, 1948 [summarized by Knudsen, 1995]; Graham, 1988), and feeding (Graham, 1988). Ammonicera should not be confused with Ammonicerina-see synonymy of Omalogyra (below). REMARKS ON OMALOGYRA AND ITS TYPE SPECIES Omalogyra was introduced by Jeffreys (1859b) in the midst of an engaged discussion (with Clark, 1859) ultimately involving the identities of Helix nitidissima Adams, 1800, "Skenea" nitidissima sensu Forbes and Hanley, 1850, and "Tmncatella" atomus Philippi, 1841. The current understanding of Omalogyra is based on Fretter's (1948) excellent anatomical study on British animals identified as 0. atomus. Other published information on this species includes gross anatomy and radula (G. 0. Sars, 1878), nervous system (Huber, 1993), spermatozoa (Healy, 1993), and egg capsules (Graham, 1988; Knudsen, 1995 [However, it should be noted that the accompanying SEM shell photographs, Knudsen's fig. 5, seem to be of a skeneopsid, not of 0. atomus]). The "eggs" of 0. atomus as described by Jeffreys (1867) and Lebour (1937) were subsequently recognized as misidentified glandular structures (Fretter, 1948). No type material for any of these nominal taxa could be located; our following discussion thus has to concentrate on literature review: Helix nitidissima J. Adams, 1800, was introduced with a short description and three illustrations (here reproduced in Fig. 9). The species was accepted and cited, in various generic combinations, by subsequent authors (e.g., Weinkauff, 1868:266, as "Spira nitidissima Adams"). Many authors have considered H. nitidissima J. Adams, 1800, as synonymous with Tmncatella atomus Philippi, 1841 (e.g., Fischer, 1857; Weinkauff, 1868; Fretter & Graham, 1978; Rolan, 1983; Graham, 1988; Poppe & Goto, 1991; Rosenberg/Malacolog, 1997). The original description by Adams (1800: 4, pl. 1, figs. 22-24) was based on the shell alone: "H.[elix] testa duobus anfractibus, subtilissime transverse striata. Obs. Corneous, pellucid, umbilicated; easily distinguished by the uncommon brilliancy of its glossiness." Original figure 23, said to be of "natural size" (1800:6) measures nearly 3 mm. The shell, much too large to be a European omalogyrid species, was subsequently recognized as "evidently the fry of ZLmites radiatulus [J. Alder, 1830]," a land snail, by Jeffreys (1867:71). The holotype of H. nitidissima was not located (K. Way, BMNH, pers. comm., 1997). The interpretation as a young stage of a British land snail is here accepted; H. nitidissima Adams is not a senior synonym of T. atomus. Much of the interpretation of "nitidissima " by subsequent authors was based on "Skenea" nitidissima sensu Forbes and Hanley, 1850, who used this name for a different species. Several authors erroneously credited Forbes and Hanley with the description of a new species THE NAUTILUS, Vol. 111, No. 1 Page 6 23 24 9 fi/g.4. J. a. (j ｾ＠ .<4 °' Ci[ /.) 10 Figure 9. Reproduction of original illustrations of Helix niliJ. Adams, 1800 (from Adams, 1800: pl. 1, figs. 22-24). Figure 10. Reproduction of original illustrations ofTnmcatella atomus Philippi, 1841 (from Philippi, 1841: pl. 5, figs. 4a-cl). dissima "Skenea nitidissima " (e.g., Jeffreys, 1860; Nordsieck, 1972; No rdsieck & Garcia-Talavera, 1979; Gaglini, 1993). However, Forbes and Hanley the mselves (1850: 158) cited the species as "S. [kenea] nit idissima, Adams" with full page and figure reference to Adams' original work. It is this misidentified "nitidissima se11s11 Forbes & Hanley" that ente rs into the various lengthy published discussions compaiing "n itidissima" and Tnmcatella atomus. Philippi (1841:54, pl. 5, figs. 4a-d) described and illustrated Tnm catella atomus, collected in Sorre nto (Campania, southe rn Italy). He e mphasized that he was able to study the animal in detail at a magnification of 60 times and placed it in Tnmcatella because of the animal's similarity to members of that genus . In 1844, he re-described the species (p . 134, pl. 24, fig. 5; again as "n. sp.") and reproduced his 1841 illustrations of T atomus. Philippi's (1841) illustrations, here reproduced in Fig. 10, show a living specimen with planispiral shell (with logarithmic growth), tapering tentacles, an operculum, and a representation of actual size of about 0.5 mm. The type mate1ial has not been located in Berlin or Santiago (von Rintelen, ZMB, pe rs. comm ., 1997; MNH N, pers. obs., 1997). Forbes and Hanley (1850:158-160, pl. 73, figs. 7, 8) described and illustrated a British shell under the name "S. [kenea] nitidissima, Adams"; they did not mention the living animal. They placed Philippi's Tnm catella atom11s, \vith question mark, in synonymy. Jeffreys (1859a: l09l l l, pl. 3, figs. 15a, b , 16a-c) discussed the species, as E11omphalus nitidissimus, vvith a sketch of the animal (showing ciliated head lobes, no tentacles, and a unise- riate radula). He reported its range as "from the Shetlands to Sicily, and probably far beyond these limits" (p. 111) based in part on the synonymy of Tnm catella atomus of Philippi, and ex-pressed his astonishment over Philippi's "mistake" of describing the animal so differently (i.e., with tapering tentacles). Much of the ensuing confusion was based on (1) the treatment of Philippi's Italian "Tnm catella atom us" specimens as members of the British "Omalogyra nitidissima" sens11 Forbes and Hanley, and (2) the discrepancy between gross anatomical desc1iptions of these two species, i.. e., with or witl1out tapering head tentacles, respectively. Clark (1859:410-413, text-figure ), after reexammmg British animals reconstituted from d1ied specimens, disagreed witl1 Jeffreys and corroborated tl1e correctness of Philippi's figure of an animal vvitl1 triangular tentacles, the large eyes e mbedded at tl1e center of their bases. "It appears quite clear that Mr. Jeffreys has delineated his animal vvith rounded lobes, or, in otl1er words, \.vith the tentacles retracted ..." (p. 411 ). Jeffreys (1859b:498) rebutted: "What Mr. Clark supposed to be tentacula must have been tl1e sh1ivelled lobes of the veil. ..." Fischer (1859:364-367) joined Cla rk in criticizing Jeffreys (1859c), assuming that the latte r had described a larval stage with vela instead of tentacles. Jeffreys tl1en (1860: 108-111), in rebuttal of Fischer, affirmed that his observations were based on adult specimens \vithout tentacles. Finally, in B1itish Conchology, Jeffreys (1867:6771, pl. 1, fig. 5; 1869:209, pl. 70, fig. 2) again described the shell and animal in detail, reaffirming his opinion of Philippi's e rror, but recognized tl1e prio1ity of "Homalogyra atom11s" (Philippi) ove r "Skenea 11'itidissima" of Forbes and Hanley. This "anatomically corrected" Homalogyra atom11s, vvith "Skenea" nitidissima sensu Forbes and Hanley in synonymy, is tl1e Omalogyra atomus described in detail by Frette r (1948) and tl1at currently fonns our concept of the genus. Unfortunately the original figures of Tnmcatella atomus Philippi, 1841, are in conflict with the descriptions of Fretter. Philippi's illustrated gross morphological details (i.e., tapering tentacles) are indicative of Ammonicera. Meanwhile, the sketched smoot11 shell appears in line witl1 tl1e current concept of Omalogyra. In the absence of type mate rial, it is impossible to ex-plain this discrepancy. It is possible that Philippi's material contained members of both genera and his illustration is a composite based on more than one species. In the inte rest of nome nclatural stability, we base our interpre tation of Philippi's Truncatella atomus on his illusb·ation/description of the she ll alone (excluding the an a tomy in original fig. 4c), thus preserving this name for "Skenea" nitidissima sensu Forbes and Hanley, 1850 (non Adams, 1800), and Omalog yra atomus sensu J e ffreys, 1859, as well as Fretter, 1948. The taxonomic confusion has been compounded by uncertain ty about tl1e type species designation and tl1e date of introduction of Omalogyra. Some authors (e.g., R. Bieler and P. M. Mikkelsen, 1998 Waren, 1980:12) cited it as having been introduced by Jeffreys (1860), with type species Trnncatella atomus Philippi, 1841, by monotypy. Others (e.g., Wenz, 1939: 647-648) gave "O. nitidissima (Forbes & Hanley)" as type species. The date of description is often erroneously cited as "1867" (e.g., Abbott, 1974; Castellanos, 1989a; Vaught, 1989; Rios, 1994). The generic name "for the reception of these anomalous mollusks" was in fact proposed by Jeffreys (1859b: 498). In that paper, he referred by name to "Euomphalus nitidissimus" (with reference to his earlier, 1859a, article), to "E. Rota" and its "variety tricarinata of Webster." In the referenced article, he additionally stated a synonym for "E." nitidissimus: "I have no doubt that it is the Trnncatella atomus of Philippi" (1859a:lll). Jeffreys did not indicate a type species. Following ICZN (1985: Art. 69(i)), there are four "originally included nominal species": Helix nitidissima J. Adams, 1800. Now considered a land snail [Jeffreys recognized the misidentification only in 1867; his (1859a, b) usage thus cannot be construed as "deliberately used in the meaning of a previous misuse" (ICZN, 1985: Art. ll(i)]. Truncate/la atomus Philippi, 1841 [in synonymy]. Skenea rota Forbes and Hanley, 1850. Now considered a member of Ammonicera. Skenea tricarinata Webster, 1856. Described as a potential new species; subsequently (beginning with Jeffreys in Webster, 1857) considered a variety/synonym of S. rota. Jeffreys (1867:69 ff.) synonymized "Skenea nitidissima" sensu Forbes and Hanley under Trnncatella atomus, after recognizing the true Helix nitidissima Adams as a land snail. He also synonymized Skenea tricarinata Webster under Skenea rota. No type species was designated. Jeffreys therein changed the generic name to Homalogyra, an unjustified emendation. The first authors to select a type species appear to have been Bucquoy et al. (1884:78) who stated "Type: Homalogyra atomus Philippi sp. (Trnncatella)." We therefore offer the following synonymies: Omalogyra Jeffreys, 1859b:498; type species by subsequent designation of Bucquoy et al. (1884:78), Tmncatella atomus Philippi, 1841. Ammonicerina 0. G. Costa, 1861: 71; type species by subsequent designation of Dall (1927b:l34, as "Ammonocerina"), Ammonicerina simplex 0. G. Costa, 1861. Preoccupied by Ammonicerina 0. G. Costa, 1856 [Protista]. This taxon is usually placed in synonymy of Ammonicera (e.g., Palazzi & Gaglini, 1979); however, its type species by subsequent designation belongs to Omalogyra. Homalogyra Jeffreys, 1867:67 (an unjustified emendation). Note: In the description of their new genus Transomalogyra, Palazzi and Gaglini (1979:33) made Ammonicerina simplex 0. G. Costa, 1861, the type species by original designation. This would make Transomalogyra an objective synonym of Ammonicerina and a subjective synonym of Omalogyra. However, as pointed out by Page 7 Waren (1991:74), the type species was misidentified, with Palazzi & Gaglini's illustration actually showing a shell of Adeuomphalus ammonifonnis Seguenza, 1876. Waren (1991) thus placed Transomalogyra in the synonymy of Adeuomphalus Seguenza, 1876, as a genus incertae sedis in the "Archaeogastropoda." Omalogyra atomus (Philippi, 1841) Truncate/la atomus Philippi, 1841:54, pl. 5, fig. 4a-d [excluding the sketched animal in fig. 4c]. Skenea nitidissima (Adams) sensu Forbes and Hanley, 1850, et auct. [non Helix nitidissima J. Adams, 1800]. Homalogyra atomus var. vitrea Jeffreys, 1867:69. Homalogyra atomus var. fasciata Monterosato, 1877:418. Notes on other named "varieties": Homalogyra atomus var. maculata Dautzenberg and Durouchoux, 1914:27. The authorship of this name is usually credited to Monterosato, 1875 (e.g., Gaglini, 1993: 928-02). However, Monterosato's applications and some subsequent citations of the name are not available for nomenclatural purposes because they represent nomina nuda (Monterosato, 1875:29; 1878:88; Bucquoy et al., 1884:324). The first available introduction appears to be that of Dautzenberg and Durouchoux (1914). Ammonicerina· atomus "var. pallida Monterosato 1884" as cited by Gaglini (1993:928-02) is likewise not available as of that date. Monterosato's usage (1884:22) of "var. pallida" is a nomen nudum, as is his Homalogyra atomus var. zonata Monterosato (1878:88), subsequently cited as "var. ex colore 2, zonata Monts." by Bucquoy et al. (1884:324; likewise a nomen nudum). Homalogyra atomus var. nautilifonnis De Gregorio, 1889, was recognized by Monterosato (1890:141) as a juvenile of Capulus ungaricus (Linnaeus, 1758). Nevertheless, the name nautilifonnis De Gregorio, 1889, was retained by some authors to describe an Omalogyra morph with a much widened body whorl (e.g., Nordsieck, 1972:148; Gaglini & Curini Galletti, 1978:210, fig. 2c). Gaglini (1993:928-02-3) introduced a new infrasubspecific name for this morph, Omalogyra atomus var. "inflata." Homalogyra atomus var. polyzona "Brusina mss. (fide Monterosato)" in Bucquoy et al., 1884:324, pl. 37, fig. 32. Earlier references to a variety "polyzona Brusina" by Monterosato (1872; 1875; 1878) are unavailable because they were stated in synonymy or as nomina nuda. Gaglini (1993:931-01, 931-02-3) showed that this is a potential synonym of 0. simplex, not 0. atomus. CURRENT COMPOSITION OF OMALOGYRIDAE Recognized western Atlantic Species: [regions of type localities in brackets] Ammonicera albospeciosa Rolan, 1992:44, figs. 17, 19, 21 [Cuba] Page 8 Ammonicera circumcin-a Rolan, 1992:45, figs. 23, 26, 28 [Cuba] Ammonicera familiaris Rolan, 1992:42, 44, figs. 16, 18, 20 [Cuba] Ammonicera lineofuscata Rolan, 1992:44-45, figs. 22, 24-25, 27 [Cuba] Ammonicera minortalis Rolan, 1992:40, 42, figs. 10-11, 13, 15 [Cuba] Ammonicera sculpturata Rolan, 1992:40, figs. 9, 12, 14 [Cuba] Omalogyra atomus (Philippi, 1841:54, pl. 5, figs. 4a-d) [Mediterranean] Omalogyra burdwoodiana (Strebel, 1908:52, pl. 6, fig. 85a-c [Burdwood Bank, south of Falkland Islands] Omalogyra fuscopardalis Rolan, 1992:36, 38, figs. 1, 3, 5, 7 [Cuba] Omalogyra taludana Castellanos, 1989a:88-89, figs. 1, 2 (plus sketch of apertural aspect in 1989b:pl. 1, fig. 10) [off San Jorge Gulf, Argentina] Omalogyra zebrina Rolan, 1992:38, figs. 2, 4, 6, 8 [Cuba] For the western Atlantic, eleven omalogyrid species are currently recognized. Of these, eight are to date only known from Cuba (all described by Rolan, 1992). Two others, Omalogyra burdwoodiana (Strebel, 1908) and 0. taludana Castellanos, 1989, are known from subantarctic waters off South America. Two omalogyrid species are now recognized from the east coast of the United States: Ammonicera minortalis and 0. atomus. Several other nominal omalogyrid species have been reported for the western Atlantic Ocean, but need to be excluded from that fauna: "Omalogyra planorbis": A nominal species in the western Atlantic frequently cited as an omalogyrid is Lippistes? planorbis Dall, 1927a:l31, originally described from "off Fernandina," Florida. This deep-water species was re-described in detail by Moore (1971: 114-116, fig. 1) as Omalogyra planorbis, and subsequently called Omalogyra (Ammonicera) planorbis (e.g., Abbott, 1974:81; Rios, 1994:60). This taxon was placed in l'alazzia Waren, 1991, as an "archaeogastropod" group of uncertain affiliations, tentatively assigned to Skeneidae (Waren, 1991: 74, 76). "Ammonicera fischeriana": Nordsieck (1972:149) referred to "Ammonicera fischeriana (Monterosato, 1869) = densecostata [sic] (Jeffreys, 1884)" in 'Westindien," without further explanation. This synonymy is erroneous. The West Indian record for this Mediterranean species is based on Watson's (1886) "Challenger" material of "densicostata" as explained in the following. "Omalogyra (Ammonicera) densicostata": Homalogyra densicostata Jeffreys, 1884:129, pl. 10, fig. 1, was described from "Porcupine" stations (1098-2002 m) off the coast of Portugal. Additional material from a "Bulldog" cruise off Labrador (2967 m) was also included in the original description. Abbott (1974:81) reported this species as Omalogyra (Ammonicera) densicostata from deep water off Portugal, the Azores, and Labrador. Moore (1971:114) showed that the Labrador ("Bulldog") material in fact belongs to "Lippistes" planorbis Dall, 1927, thus removing the Labrador record for "O." densicos- THE NAUTILUS, Vol. 111, No. 1 tata. Watson (1886:677) added a "Homalogyra densicostata (?)" record from north of the island of Culebra, between Puerto Rico and the Virgin Islands ("Challenger" station 24, 715 m). Moore (1971:115-116) doubted both the synonymy of the Challenger material and that of the shallow-water material reported by Dautzenberg (1889:46) for the Azores, thus restricting densicostata again to the eastern Atlantic. The species was considered a member of the eastern Atlantic omalogyrid fauna until recently (e.g., Sabelli et al., 1990; Gaglini, 1993). Homalogyra densicostata was synonymized under Adeuomphalus ammonifonnis Seguenza, 1876, and placed as an "archaeogastropod" of uncertain affiliations, tentatively assigned to Skeneidae (Waren, 1991:74 ff.). Recognized eastern Atlantic/Medite1T81lean Species: [regions of type localities in brackets] Ammonicera burnayi Rolan, 1991:112, figs. 13-14 [Cape Verde Archipelago] Ammonicera fischeriana (Monterosato, 1869:274-275, pl. 13, fig. 1) [Mediterranean] Ammonicera lignea (Palazzi, 1988:105, figs. 8, 18) [Madeira] Ammonicera multistriata Rolan, 1991:112, 114, figs. 15-16 [Cape Verde Archipelago] Ammonicera nolai Rolan, 1991:110, figs. 8-9 [Cape Verde Archipelago] Ammonicera oteroi Rolan, 1991:110, 112, figs. 10-12 [Cape Verde Archipelago] Ammonicera robusta Rolan, 1991:114-115, figs. 17-18 [Cape Verde Archipelago] Ammonicera rota (Forbes & Hanley, 1850:160, pl. 73, fig. 10; pl. 88, figs. 1, 2) [Ireland] Ammonicera rotundata (Palazzi, 1988:105, figs. 10, 21, 27) [Madeira] Ammonicera verdensis Rolan, 1991:109, figs. 6-7 [Cape Verde Archipelago] Omalogyra atomus (Philippi, 1841:54, pl. 5, figs. 4a-d) [Mediterranean] Omalogyra disculus Palazzi, 1988:104, figs. 1, 20 [Madeira] Omalogyra simplex (O.G. Costa, 1861:72, pl. 11 figs. 3 a, b) [Mediterranean] Omalogyra undosa Palazzi, 1988:104, figs. 5, 15 [Madeira] Retrotortina fuscata Chaster, 1896:2 [Strait of Gibraltar] In the eastern Atlantic, fifteen omalogyrid species are currently recognized, comprising ten species of Ammonicera, four of Omalogyra, as well as Retrotortina fuscata (for Mediterranean records see also Sabelli et al., 1990; Le Renard et al.ICLEMAM, 1997). Omalogyra atomus is the only species known from both sides of the Atlantic; it is widely distributed, ranging from the Mediterranean, Madeira, and the Azores to Norway, Iceland, Greenland, and in New England (Abbott, 1974; Bullock, 1969, 1995; Fretter & Graham, 1978; Thorson, 1944) from Maine to Rhode Island. Egorova (1991) recognized material from Antarctic waters, previously identified and cited as 0. atomus, as members of a morphologically extremely similar species, 0. antarctica Egorova, 1991. Several other nominal omalogyrid species have been described for the eastern Atlantic. Of these, Omalogyra aperta Sykes, 1925:192, from off Portugal, was recognized as a member of the "archaeogastropod" genus Eu- R. Bieler and P. M. Mikkelsen, 1998 daronia Cotton, 1945, by Waren (1991:80). Homalogyra granulosa Sykes, 1925, also from off Portugal, was placed in the "archaeogastropod" genus Retigyra Waren, 1989 (see Waren, 1992:168). Homalogyra paradoxa "Monterosato (? MS.)" of Sykes (1925:192) is a nomen nudum. Two other nominal species introduced by Sykes (H. sinuosa Sykes, 1925, and H. (?) marshalli Sykes, 1925) are in need of further study (see Palazzi, 1992). An additional Mediterranean species, 0. ausonia Palazzi, 1988, was recently made the type of Palazzia Waren, 1991, and transferred to the "archaeogastropods," with tentative placement in the Skeneidae (Waren, 1991). Nominal species Homalogyra ornata Dautzenberg, 1889 (p. 46, pl. 4, fig. 9a-d), described from the Azores, is still in need of reinvestigation. It should be noted that Palazzi (1988) used "ausonia" (Italy) and "disculus" (little disk) as nouns in apposition in the original descriptions; recent usage as "Palazzia ausoniae" or "Omalogyra discula" (e.g., Sabelli et al., 1990; Giannuzzi-Savelli et al., 1994; Arduini et al., 1995) are incorrect subsequent spellings. ACKNOWLEDGMENTS This project, as part of a broader study of lower heterobranch gastropods, was supported under National Science Foundation grant DEB-9318231 to RB. Field and laboratory work in Florida was made possible through Visiting Scientists Awards by the Smithsonian Marine Station at Link Port (SMSLP) to RB; Dr. Mary E. Rice and the station staff are gratefully acknowledged for their support. Field collecting in the Florida Keys was supported through supplementary funding from the Bertha LeBus Charitable Trust and Field Museum's Marshall Field Fund. Dr. Kenneth J. Boss (Museum of Comparative Zoology, Harvard University) and Richard E. Petit (North Myrtle Beach, South Carolina) kindly provided literature, and Roberto Cipriani (FMNH) assisted with translations. We thank Dr. Sergio Letelier (MNHN) for hospitality extended during RB's visit to Santiago, Kathie Way (BMNH) and Thomas von Rintelen (ZMB) for information on type holdings of their respective collections, Dr. Cristian F. ltuarte (MLP) for a specimen loan, and Richard E. Petit (North Myrtle Beach) as well as two anonymous reviewers for their comments on the manuscript. The excellent facilities and helpful staff of the AMNH and FMNH libraries are also acknowledged. This is SMSLP Contribution no. 434. LITERATURE CITED Abbott, R. T. 1974. 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