Tenagodus barbadensis, Bieler, 2004

Bieler, Rüdiger, 2004, Sanitation with sponge and plunger: western Atlantic slit-wormsnails (Mollusca: Caenogastropoda: Siliquariidae), Zoological Journal of the Linnean Society 140 (3), pp. 307-333 : 310-321

(SYNONYM TENAGODIDAE GILL, 1871 )

GENUS TENAGODUS GUETTARD, 1770

Type species by subsequent designation ( Adams & Adams, 1853 -4: 360–361): Serpula anguina Linnaeus, 1758 (Indo-Pacific). Linnaeus’ (1758: 787) Serpula anguina was based on more than one species, and the Linnaean collection contains several taxa under this name, without indication of type specimen ( Hanley, 1855: 448). Linnaeus had adopted the species name from the nonbinominal ‘ Solen anguinus ’ of Rumphius (1705: 125) and referred to illustrations in that work. The specimen illustrated by Rumphius (1705: pl. 41, fig. H) from Ambon, Moluccas, Indonesia, as cited by Linnaeus, is here selected as lectotype. Siliquaria Bruguière, 1789 , is an objective synonym of Tenagodus , with Serpula anguina Linnaeus, 1758 , as type species by subsequent monotypy ( Lamarck, 1799: 79). The complex synonymies at the generic and familial levels were discussed by Bieler (1992).

TENAGODUS MODESTUS ( DALL, 1881)

( FIGS 1, 2 , 7–9 , 26–28, 31–33 , 36, 37 , 41–43 )

Siliquaria modesta Dall, 1881: 39 . Tryon, 1886: 191. Paetel, 1888: 499. Agassiz, 1888: 71, fig. 296. Dall, 1889a: 260, pl. 26, fig. 4. Dall, 1889b: 144, pl. 26, fig. 4. Dall, 1896: 25 [‘The first reported since the original types’]. Maury, 1922: 104. Abbott, 1974: 96, fig. 926 (from Dall, 1889a,b). Rios, 1985: 47, pl. 18, fig. 210. Rios, 1994: 66, pl. 22, fig. 253. Díaz & Puyana, 1994: 140, pl. 44, fig. 481. Pointier & Lamy, 1998: 48. Hartman & Hubbard, 1999: 1 ff.

Siliquaria ? modesta: Mikkelsen, 1981: 47 .

Tenagodus modestus: Bieler, 1990: 21 . Leal, 1991: 69. Pansini et al., 1999: 429.

Type material: Dall (1881: 39) described this species based on R/V Blake material ‘found in all depths from 80 to 800 fathoms.’ He did not formally select a type specimen but added, ‘The specimen from which the description was taken lived in 220 fathoms (Station 20)’, a locality off Bahia Honda, Cuba. Eight years later, Dall (1889a: 260, pl. 26, fig. 4) listed individual stations, including number 20, and illustrated a specimen without indicating its provenance. Agassiz (1888: 71, fig. 296) illustrated another specimen from an unspecified Blake station. A comparison of the original material in the USNM and MCZ collections showed Dall’s (1889a) figure to be based on a specimen from the originally cited Blake station 20. The 22.8 mm specimen ( MCZ 341075; Fig. 2 ) is here selected as lectotype, with three paralectotypes remaining as MCZ 7419. The type locality is here thus restricted to US Coast Survey Steamer Blake station 20, off Bahia Honda, Cuba, Blake Expedition 1877–78, 220 fathoms (402 m), 23∞02¢30≤N, 83∞11¢00≤W.

Specimens examined: See Appendix 1.

Description

Shell (teleoconch) ( Figs 1, 2 , 7–9 , 42, 43 ). Relatively large, very loosely coiled; specimens usually less than 8 cm in total length, with inner apertural diameter of 4–6 mm, but occasionally reaching a length of 15 cm ( USNM 86776, Trinidad). Sculpture consisting entirely of incremental growth marks, without spiral ribs or striae. Earliest whorls often internally closed off by concave calcareous septa (as shown in Fig. 14 for a different species). Early part of open shell slit (corresponding to region of posterior mantle cavity) narrowed by lateral ingrowths to a – usually very regular – series of holes ( Fig. 7 ); the most recent (body whorl) slit left open with slightly undulating margins ( Fig. 9 ). Slit of earlier whorls (now in the region of digestive gland and gonad) filled-in with shell material that often protrudes outward through the holes ( Figs 7, 8 ). Fresh specimens have somewhat glossy shell surface, particularly on early whorls; later whorls often chalky externally. Colour off-white, sometimes with light tan mottling.

Protoconch ( Figs 15–21 ). Fragile, easily decollated and rarely retained in museum specimens [in fact, Dall’s (1889a: 260) original description of live material maintained that it ‘shows no sign of a regularly formed spiral nucleus’], approximately 212– 240 Mm high and 200–216 Mm wide, with 2 whorls. First whorl represents smooth, bulging embryonic shell (protoconch I, hereafter PC-I), about 129– 133 Mm in diameter, with circular aperture; second whorl formed by helically coiled, broadly rounded, sculptured larval shell (protoconch II, hereafter PC-II). Sculpture consisting of about 5 very irregular rows of distinctly demarcated pustules on upper part of whorl, followed below by about 7 finely granulated spiral striae (which appear as rows of fused pustules). Areas between striae and region around open larval umbilicus with more or less distinct irregular rows of finer pustules. Aperture strongly sinuous, deeply embayed on upper whorl surface at point of contact with teleoconch slit area. Translucent white, lower half of PC-II brown.

Operculum ( Figs 26–28 , 36, 37 ). Large (2.5–2.8 mm in diameter) in relation to body width, dome-shaped, multispiral, tightly fitting inside shell tube, composed of 20–30 spiral layers of corneous lamella. Edge of each layer beset with rounded, thorn-like spines. Lamella not continuous internally: core filled with triangular compartments, about 6 per whorl, spirally arranged around a central axis.

Anatomy ( Figs 31–33 , 36, 37 ; for measurements, n = 12).

Head-foot: Body long and slender, spirally coiled, forming approximately 3 whorls, 2 of which occupied by mantle cavity; overall body length of preserved animal (excluding operculum) 35–42 mm. Mantle cavity up to 30 mm long; body width in mid-mantle region approximately 1.3 mm. Foot forming a round column bearing the large operculum; small (0.6 ¥ 1.0 mm), glandular, transversely furrowed area of foot (the ‘sole’) in front of the mouth. Head small in comparison to width of body; snout short, bluntly rounded, with mouth a vertical slit at its tip. Two cephalic tentacles about as long as snout, with black eyes at their outer bases. Mantle margin simple but with small weak papillae on inner side. Head-foot and area between mantle papillae with brownish pigment (black before preservation?). No pedal tentacles or pedal mucous gland.

Pallial cavity: Corresponding to shell fissure, dorsal right side of mantle with slit, longitudinally opening mantle between rectum and pallial gonoduct. Ctenidium extending as far as mantle slit, its filament lengths gradually decreasing posteriorly; curved, rodshaped gill filaments long (to 1.8 mm), narrow (about 30 ¥ 80 Mm in cross section), and very flexible ( Fig. 31 ). In addition to rows of relatively short frontal and abfrontal cilia, a row of very long (up to 40 Mm) lateral cilia on either side; thickened, club-shaped tip ciliated (details not observed due to poor preservation). Row of filaments extends across mantle cavity top right side of animal. Osphradium restricted to anterior part of mantle cavity, beginning next to and shortly behind anteriormost gill filaments; about 2.4 mm in total length, compressed-S-shaped, with posterior leg the longest; its sensory zone with weak meanders. Endostyle forming a narrow glandular tract between gill axis and osphradium, along entire length of gill. Sharply demarcated food groove on dorsum of animal, with thick, tall ridges; groove extending straight in about mid-line from posterior end of mantle cavity to neck region and then looping around right side of head, ending with spoon-like process at mouth opening ( Fig. 37 , sp.).

Alimentary system: Mouth opening flanked by pair of slender jaws made up of platelets in palisade-like fashion. Simple oesophagus (without dorso-ventral division or crops) with two salivary glands, the latter somewhat increasing in bulk posteriorly and ending well in front of concentrated nerve ring, passing straight to stomach as a simple tube. Digestive gland a single lobe. Simple intestine loops forward and continues as short rectum (about 2.4 mm within mantle cavity), with anal opening in posterior part of mantle cavity; weak ciliated groove leading from anus forward to mantle cavity. Stomach with style sac and gastric shield. Radula small ( Figs 32, 33 ; length 0.94–1.00, width 0.10–0.12 mm), taenioglossate, with 52–54 rows, transparent; rachidian with strong, finger-like projecting main cusp and 8–12 short flanking cusps on either side, smooth basal platform, no lateral or basal projections. Lateral tooth with slender, triangular main cusp and 8–12 short inner flanking cusps and about 20 outer flanking cusps. Marginal teeth hooklike, bluntly tipped; cutting edge of inner marginal tooth finely cuspidate on either side, of outer marginal tooth smooth.

Reproductive system: All sexable animals (5) female. Ovipositor ( Fig. 37 , ov) with central groove anterior and to the right of head.

Habits and habitat

According to Dall (1881: 39, original description): ‘Found at all depths from 80 to 800 fathoms [146– 1463 m], but not in less than 80 fathoms. The specimen from which the description was taken lived in 220 fathoms’. Hartman & Hubbard (1999) described a large aggregation in a sponge ( Thrombus ) at a depth of 21.5 m ( Trinidad). Live material in the present study came from between 56 and 73 m, while shells were recorded from between 18 and 1472 m. Tenagodus modestus was originally described from live material ( Dall, 1881: 39), but no reference was made to its anatomy or even to the fact that it was collected in or with a sponge. Specimens in the present study were found completely embedded in a colony of an unidentified species of Thrombus (Porifera: Demospongiae: Choristida: Thrombidae ; S. Pomponi, pers. comm.) at c. 56 m. In situ , only the apertural openings were visible from the outside. The density of individuals inside the sponge was very high, with about 54 shell apertures emerging from a surface area of 5 ¥ 5 cm. This translated into 5400 snails per surface square metre of the sponge colony (see also Figs 42, 43 ). There was relatively little sponge tissue between the gastropods, explaining the intertwined and contorted condition of shells as a result of competition for space.

Geographical distribution

Widely distributed in deeper waters of the western Atlantic, ranging from Bermuda, Florida, Bahamas to Brazil (Bahia to Espírito Santo, all seamounts; Rios, 1994), the Gulf of Mexico and the Caribbean Sea.

Taxonomic remarks

Tenagodus modestus was once considered to be ‘the young’ of T. squamatus ( Abbott, 1954: 145) . Many collection specimens labelled ‘ modestus ’ were found to be juvenile or strongly eroded (and thus smooth-shelled) T. squamatus . The latter species has fluted spines on its shell, does not have its shell slit narrowed to form a regular series of holes, and its protoconch is very different (see below).

TENAGODUS SQUAMATUS ( DE BLAINVILLE, 1827)

( FIGS 3–5 , 10–13 , 22 , 29, 30 , 35 , 38–40 )

Siliquaria squamata de Blainville, 1827: 213 . Chenu, 1842 -43: 3, pl. 2, fig. 12. Mörch, 1861: 414. Paetel, 1869: 56. Dall, 1889a: 260. Dall, 1889b: 144. Nutting, 1920: pl. 40, fig. 2. Maury, 1922: 103–104. Peile, 1926: 78. Merrill & Petit, 1965: 60. Gould, 1966: 1–11, figs 1-3, 6 (photographs of protoconchs reversed). Abbott, 1968: 84, fig. 4. Rios 1970: 40, pl. 8, fig. Abbott, 1974: 96, fig. 925. Rios, 1975: 46, pl. 13, fig. 171. Emerson & Jacobson, 1976: 74, pl. 6, colour fig. 1. Abbott & Dance, 1982: 61, fig. Rios, 1985: 46, pl. 18, fig. 209. De Jong & Coomans, 1988: 40. Leal, 1989: 8, fig. 9 (SEM photomicrograph of protoconch and juvenile teleoconch). Harasewych, 1989: 48, pl. 32. Lipe & Abbott, 1991: 52, fig. on 53. Rosenberg, 1992: 52–53, fig.? Rios, 1994: 66, pl. 22, fig. 252. Díaz & Puyana, 1994: 140, pl. 44, fig. 482.

Siliquaria squammata [sic], Chenu, 1842 -43: figure caption, pl. 2, fig. 12 (erroneously giving ‘ nobis ’, i.e. Chenu, as authority). Chenu, 1859: 322, 309 (from Chenu, 1842 -43).

Tenagoda [sic] squamata, Adams & Adams, 1853 -54: 361.

Tenagodus squamata, Mörch, 1861: 414 .

Tenagodus squamatus, Mörch, 1865: 99 . Mörch, 1877: 110. Abbott, 1954: 145, pl. 21, fig. G. Parker & Curray, 1956: 2434. Bieler, 1990: 21. Leal, 1991: 68, pl. 6, figs I, J. Bandel & Kowalke, 1997: 263. Turgeon et al., 1998: 69, 213. Pansini et al., 1999: 429. Redfern, 2001: 23, pl. 12, fig. 95A, B.

Tenagodus (Pyxipoma) anguillae Mörch, 1861: 410 , 412. Mörch, 1877: 110.

Tenagodus (Agathirses) squamata, Mörch, 1861: 411 . Siliquaria (Tenagodus) aquillae [sic] Mörch, Sowerby in Reeve, 1876: last page (‘species not known’).

Tenagodus ruber (Schumacher) , Mörch, 1877: 109 [ Bermuda and St. Thomas] [non Anguinaria rubra Schumacher, 1817 ].

Siliquaria (Agathirses) anguina (Linnaeus), Tryon, 1886) [in part]: 190, pl. 58, fig. 25 (after Chenu, 1842 - 43) [non Serpula anguina Linnaeus (1758) ].

Siliquaria anguina Vr. squamata, Paetel, 1888: 499 .

Siliquaria anguillae, Paetel, 1888: 499 . Menzies et al., 1966: 408 [as S. angullae ], 414, 428. Morris, 1973: 145, pl. 41, fig. 9. Wolfe & Wolfe, 1970: 14. Porter, 1974: 15. Lipka, 1974: 148, 168, fig. 13. Warmke & Abbott, 1975: 67, pl. 12 fig. g.

Siliquaria (Tenagodus) ruber Schumacher, Heilprin, 1889: 172 [ Bermuda, following Mörch].

Siliquaria ruber Schumacher, Dall, 1889a: 259 .

‘ Tenagodus , or Siliquaria ruber ’ Verrill, 1905: 139 [ Bermuda].

Siliquaria rubra, Peile, 1926: 78 [ Bermuda, following Verrill].

Tenagodus (Agathirsus) squamatus, Haas, 1941: 171 . Siliquaria angullae [sic] Mörch, Abbott, 1974: 96 (in synonymy). Rios, 1985: 46 (in synonymy). Rios, 1994: 66 (in synonymy).

Type material: De Blainville’s original material of Siliquaria squamata has not been located. A lectotype for Tenagodus anguillae Mörch, 1861 , is here designated ( Anguilla, Leeward Islands; before 1848; ex coll. Hornbeck; ZMK; Fig. 5 ), from a lot that also contains 1 paralectotype and 1 loose operculum.

Specimens examined: See Appendix 2.

Description

Shell (teleoconch) ( Figs 3-5 , 10–13 ). Large and very loosely coiled; some specimens exceed a total length of 17 cm and inner apertural diameter of 10 mm. Juvenile shell with little sculpture except growth marks; shell later develops faint longitudinal lines becoming rows of spines. Smaller specimens with seven, larger lines with 9–12 longitudinal rows of spines (occasionally more numerous, sometimes with finer ridges interspersed, especially near shell slit); spines strongest on underside of coils, and nearly absent in what would be the umbilicus in a regularly coiled shell. Spines curved and fluted tube-like, with open side facing aperture. Later part of shell has healed breakages throughout. Earliest whorls often internally closed off by concave calcareous septa (as shown in Fig. 14 for a different species). Early part of open shell slit (corresponding to region of posterior mantle cavity) narrowed by lateral ingrowths, but not normally forming complete holes ( Fig. 11 ); the most recent (body whorl) slit barely restricted, with near-even margins ( Fig. 12 ). Slit of earlier whorls (now in the region of digestive gland and gonad) filled-in with shell material ( Figs 10, 11 ). Fresh specimens with glossy shell surface; strongly eroded specimens often without spines, but with longitudinal sculpture still discernible. Shell light tan to reddish brown, darker near shell slit (older specimens usually faded to yellowishwhite).

Protoconch ( Fig. 22 ). Extremely fragile and easily decollated, rarely retained in museum specimens [in fact, Dall’s (1889a: 260) original description maintained ‘The most perfect spires I have seen showed no sign of a regularly spiral nucleus’. Data presented here obtained from descriptions and images in Gould (1966; note that all protoconch images in that work are reversed), and Leal (1991; pers. comm.)]. Approximately 0.26–0.29 mm high and 0.26–0.27 mm wide (based on 10 specimens studied by Gould, 1966: 6), of two and a quarter whorls. The first part represents smooth, bulging, almost planispiral embryonic shell with circular aperture; the following whorl formed by helically coiled, broadly rounded, sculptured larval shell. Sculpture consisting of 5–8 rows of small pustules on upper part of whorl, followed below by finely granulated spiral striae (which appear as rows of fused pustules); contact between the two types of ornament at the whorl periphery relatively sharp. Aperture strongly sinuous, deeply embayed on upper whorl surface at point of contact with teleoconch slit area. Embryonic shell whitish brown, larval shell light golden brown.

Operculum ( Figs 29, 30 , 38 ). Very large (5.0–6.6 mm in diameter) in relation to body width, cylindrical, multispiral, tightly fitting inside shell tube; composed of numerous spiral layers of corneous lamellae, the earlier ones usually decollate and only 8–12 remaining attached to the animal (height of operculum then 6.8– 12 mm). Edge of each layer with flat spine-like projections ( Fig. 30 ); lamella not continuous internally: core filled with triangular compartments, about 6 per whorl, spirally arranged around a central axis ( Fig. 29 ).

Anatomy ( Figs 34, 35 , 38-40 ; for measurements, n = 3).

Head-foot: Body long and slender, spirally coiled, approximately 3 whorls, 2 of which occupied by mantle cavity; overall body length (excluding operculum) 55–67 mm. Mantle cavity to 52 mm long; body width in mid-mantle region approximately 1.3 mm. Foot forming a round column bearing the very large operculum; small (3.5 ¥ 1.5 mm), glandular, transversely furrowed area of foot (the ‘sole’) in front of the mouth, with tip of the sole always pointed. Head very small in comparison to width of body; snout short, bluntly rounded, with mouth a vertical slit at its tip. Two cephalic tentacles about as long as snout (1.0– 1.3 mm), with black eyes on their outer bases. Mantle margin smooth, but with fine papillae in gill region (when animal retracted). Head and anterior foot region salmon-coloured to rust-red; uppermost skin layer with fine brown-black pigment (fading to lightbrown when ethanol preserved), especially on snout, tentacle and metapodium. Numerous white granules embedded in head-foot tissue. No pedal tentacles or pedal mucous gland.

Pallial cavity: Corresponding to shell fissure, dorsal right side of mantle with slit, longitudinally opening mantle between rectum and pallial gonoduct; slit usually lined on outside with yellow to tan. Ctenidium extending as far as mantle slit, its filament lengths gradually decreasing posteriorly; 25–31 filaments per mm. Curved, rod-shaped gill filaments very long (6.8– 7.5 mm), narrow and very flexible (details of ciliation not observed due to poor preservation); row of filaments extends across mantle cavity top right side of animal. Osphradium restricted to anterior part of mantle cavity, beginning next to and shortly behind anteriormost gill filaments; short, 5.3–7.8 mm in total length, compressed S-shaped, with anterior leg somewhat longer, its sensory zone with weak meanders. Endostyle forming a narrow glandular tract along entire length of gill.

Alimentary system: As in T. modestus , anal opening of short rectum (7.9–9.6 mm in mantle cavity) likewise in posterior part of mantle cavity; weak ciliated groove leading from anus forward to mantle cavity. Radula small ( Figs 34, 35 ), length about 1.36 mm, width 0.18 mm), taenioglossate, with 48–52 rows, transparent brown; rachidian with strong, slender triangular main cusp and 8–12 short flanking cusps on either side, smooth basal platform, no lateral or basal projections. Lateral tooth with slender, triangular main cusp and 7–12 short inner flanking cusps and about 25 outer flanking cusps. Marginal teeth hook-like, bluntly tipped; cutting edge of inner marginal tooth finely cuspidate on either side (up to 30 cusps on outer side), of outer marginal tooth smooth.

Reproductive system: Sexable animals (2) female, with developing eggs in gonad.

Habits and habitat

Tenagodus squamatus is usually found associated with the sponges Spongosorites ruetzleri ( Soest & Stentoft, 1988) and S. siliquaria Soest & Stentoft (1988) . In the original descriptions of S. ruetzleri (as? Halichondria ) and S. siliquaria, Soest & Stentoft, 1988: 92–93 ) noted the association of ‘vermetids’ with the former and members of the genus Siliquaria [= Tenagodus ] with the latter. Shells in the present study came from depths ranging between 13 and 366 m, with live records from between 51 and 213 m. Abbott (1974: 96) and Rios (1994: 66) reported maximum depths of more than 700 m for the siliquariid.

Geographical distribution

Widely distributed in the deeper waters of the western Atlantic, from Bermuda, the Carolinas (e.g. Merrill & Petit, 1965), Florida, Bahamas, to Brazil (Amapá to Espírito Santo, all Seamounts; Rios, 1994), the Gulf of Mexico and the Caribbean Sea.

Taxonomic remarks

In teleoconch characters, Tenagodus squamatus is very similar to the type species of Tenagodus , T. anguinus ( Linnaeus, 1758; originally described as Serpula ) of the Indian Ocean. Tryon (1886: 190) even synonymized the two. The anatomy of the type species remains unstudied. T. barbadensis sp. nov. is also very similar in teleoconch characters, but differs greatly in its larval shell morphology (see below).

Tenagodus squamatus specimens from Bermuda are frequently dark reddish brown in colour and have been called ‘ Tenagodus ruber ( Schumacher, 1817) ’. Verrill (1905) thought that it was this form that gives the reddish tint to the ‘pink beaches’ of Bermuda, which in fact is caused by the abundant shells of the foraminiferan Homotrema rubrum (Lamarck, 1816) . Schumacher (1817) gave a short description for his Anguinaria rubra and therein referred to ‘ Serpula anguina ’ sensu Martini (1769: 50 , pl. 2, figs 13, 14), non Linnaeus, 1758. Martini’s original figures show several different forms. Mörch (1861: 403) excluded Martini’s references and restricted Schumacher’s Tenagodus ruber to a purple-shelled form with the type locality ‘Moluccas’, but later ( Mörch 1877: 110) used the name again for material from Bermuda and St. Thomas. Mörch’s earlier (1861) decision is followed here, applying Schumacher’s A. rubra to an Indo- Pacific species.

The type material of Tenagodus anguillae Mörch, 1861 , consists of two incomplete, eroded juvenile shells without protoconch (11.6 and 10.7 mm), and one damaged, incomplete operculum. The somewhat larger shell is here selected as lectotype (ZMK; Fig. 5 ). The specimens agree in their morphology with beachworn juvenile T. squamatus and the nominal species is thus placed in its synonymy. Siliquaria ‘ aquillae ’ and S. ‘ angullae ’ of authors are subsequent misspellings without nomenclatural status. North Carolina records of ‘ Siliquaria anguillae ’ are here interpreted as having been based on eroded (and thus smooth) shells of Tenagodus squamatus , although it is possible that T. modestus specimens might have been commingled.

Figures

Figures 1–6. Figs 1, 2, Tenagodus modestus, shell. 1: Florida Keys, 56 m, FMNH 296716; greatest length = 48 mm. 2: lectotype of Siliquaria modesta Dall, 1889, Cuba, MCZ 341075; greatest length = 22.8 mm. Figures 3–5, Tenagodus squamatus, shell. 3: Venezuela, Golfo Triste, 46–55 m, FMNH 296706; greatest length = 165 mm. 4: Bermuda, 110 m, FMNH 296697; greatest dimension (diameter of spiral) = 46.6 mm. 5: lectotype of Tenagodus anguillae Mörch 1861, Anguilla; ZMK; greatest length = 11.6 mm. Fig. 6, Tenagodus barbadensis sp. nov., shell; Barbados, 69 m, FMNH 301239; greatest length = 35.8 mm.

Figures 7–14. Figs 7-9, Tenagodus modestus, teleoconch detail (Florida Keys, FMNH 296716). 7: transition from shell covering posterior organs (shell slit filled) to posterior mantle cavity region (shell slit narrowed to series of holes). 8: detail of Fig. 7; note regular, layered restrictions. 9: late shell; slit unrestricted. Figs 10–13, Tenagodus squamatus, teleoconch detail (Bahamas, FMNH 296709). 10: transition from shell covering posterior organs (shell slit filled) to posterior mantle cavity region (shell slit open). 11, 12: detail of Fig. 10; note incomplete restrictions when compared to Fig. 8. Fig. 13: adult sculpture; note fluted hollow spines. Fig. 14, Tenagodus barbadensis sp. nov., teleoconch detail (FMNH 301290); early whorls opened to display internal septation by calcareous plugs. All SEM. Scale bars = 300 Mm (Figs 8, 11, 12) and 1 mm (all others).

Figures 26–31. Figs 26-28, Tenagodus modestus, operculum (Florida Keys, FMNH 296716). 26: outside (heads-on) aspect, diameter = 2.5 mm. 27: razorblade section of whole mount attached to foot, showing internal compartments; diameter = 2.5 mm. 28: detail of Fig. 26, spines on lamellar margin. Figs 29, 30, Tenagodus squamatus, operculum (Bahamas, FMNH 296703). 29: razorblade section of whole mount attached to foot, showing internal compartments; diameter = 5.6 mm. 30: details of Fig. 29, spines on lamellar margin (note attached sponge spicules). Fig. 31, Tenagodus modestus, highly flexible ctenidial filaments (FMNH 296716). All SEM, critical-point dried. Scale bars = 100 Mm.

Figures 32–35. Figs 32, 33, Tenagodus modestus, radula (Florida Keys, FMNH 296716). 32: part of whole mount showing entire rows. 33: half row, rachidian teeth on left (partly dislocated to show base), smooth outer marginal on right. Figs 34, 35, Tenagodus squamatus, radula (Bahamas, FMNH 296701). 34: part of whole mount showing entire rows. 35: half row, rachidian tooth in centre left, smooth outer marginal on right (surface pattern resulting from preservation artefact). All SEM. Scale bars = 40 Mm (Figs 32, 34) and 20 Mm (Figs 33, 35).

Figures 36–37. Tenagodus modestus, external softbody anatomy, from preserved specimen (Florida Keys, FMNH 296715). 36: overall morphology; ctenidial filaments reflected out of naturally slitted mantle cavity to expose food groove; note greatly reduced cephalic and pedal region compared to rest of body. 37: oblique lateral aspect of head-foot region, mantle reflected along naturally occurring slit; note short looped osphradium, glandular pad, absence of rectum, and weak mantle papillae on inner mantle margin. Scale bars = 2 mm. Abbreviations: an, anus; com, columellar muscle; ct, ctenidium; dg, digestive gland; en, endostyle; ey, eye on outer base of tentacle; fg, food groove; ft, foot; mep, mantle edge papillae; ms, mantle slit; op, operculum; os, osphradium; ov, ovipositor.

Figures 41–43. Tenagodus modestus in sponge Thrombus sp. (Florida Keys, HBOM 065: 00767, 065: 02026). 41: sponge colony in 56 m depth off Key Largo; approximately 3 m in length (underwater photograph by submersible). 42: detail of Fig. 41, sponge surface with apertural openings of gastropods (alcohol-preserved). 43: side view of dissected, alcoholpreserved sponge, showing density in situ. Coin diameter = 19 mm.

Figures 15–25. Figs 15-21, Tenagodus modestus, protoconch (Florida Keys, FMNH 296716). 15, 16: side aspects. 17: basal aspect with larval shell umbilicus. 18: apical aspect, showing smooth embryonic shell and sculptured larval shell. 19, 20: oblique aspects of protoconch. 21: detail of sculpture, pustules and striae (embryonic shell on the left). Fig. 22, Tenagodus squamatus, protoconch (courtesy J. Leal). Figs 23–25, Tenagodus barbadensis sp. nov., protoconch (FMNH 301290). 23: detail of sculpture, pustules and striae (embryonic shell on the left). 24: side aspect showing large embryonic shell. 25: apical aspect, showing smooth embryonic shell and comparatively small larval shell. All SEM. Arrows marking simple apertural margin of embryonic shell (PC-I) and sinuous apertural margin of larval shell (PC-II). Scale bars = 20 Mm (Fig. 20), 80 Mm (Figs 22, 24, 25), and 40 Mm (all others).

Figures 38–40. Tenagodus squamatus, from living and preserved specimens (Bahamas). 38: oblique dorsal aspect of headfoot region, mantle reflected along naturally occurring slit; note small head and massive operculum, short looped osphradium, absence of rectum, and simple mantle margin (FMNH 296703, from preserved animal). 39: posterior animal, right side (FMNH 296700, from living specimen). 40: posterior animal, left side (as before, different animal). Scale bar = 5 mm. Abbreviations: com, columellar muscle; ct, ctenidium; dg, digestive gland; en, endostyle; es, oesophagus; ey, eye; fg, food groove; ft, foot; gd, gonoduct; go, gonad; he, heart; hy, hypobranchial gland; ki, kidney; mo, mouth opening; op, operculum; os, osphradium; pg, pallial gonoduct; pgl, lamella attached to right side of pallial gonoduct; sh, shell; st, stomach; vs, vascular system with embedded crystals.