Choanopoma andrewsae, (Ancey, 1886)

Watters, G. Thomas, 2014, A revision of the Annulariidae of Central America (Gastropoda: Littorinoidea), Zootaxa 3878 (4), pp. 301-350 : 329-331

Tudorisca andrewsae ( Ancey, 1886)

Figure 7 L–W, 12 C

Type material. Cyclostoma andrewsae Ancey, 1886 : possibly ZMB unnumbered (1), syntype. Choanopoma cozumelensis Richards, 1937 : ANSP 167749, holotype; ANSP 167639 (25), paratypes; CMNH 62.33057 (17), paratypes. Choanopoma andrewsae roatanense Richards, 1938 : ANSP 170018, holotype; ANSP 170403 (25), paratypes; FMNH 90606 (1), paratype (fig. 7 T); CMNH 62.33056 (5), paratypes.

Type locality. Cyclostoma andrewsae Ancey, 1886 : not stated, but all other species in paper from Isla de Utila, Honduras. Choanopoma cozumelensis Richards, 1937 : “ San Gerbacio, Cozumel.” Choanopoma andrewsae roatanense Richards, 1938 : “West End [town], fairly common in crevices in limestone.”

Type figured. Cyclostoma andrewsae Ancey, 1886 : unfigured. Choanopoma cozumelensis Richards, 1937 : pl. 4, fig. 3. Choanopoma andrewsae roatanense Richards, 1938 : pl. 3, figs. 1, 7; FMNH 90606, paratype, Solem, 1961: pl. 10, fig. 10.

Chresonymy.

Cyclostoma andrewsae Ancey, 1886: 251 –252; Watters, 2006: 140.

Choanopoma andrewsae ( Ancey, 1886) . Martens, 1890: 14, 16, pl. 1, fig. 4; Richards, 1937: 256; Richards, 1938: 171, 174, 176; Thompson, 1967: 225 –227, figs. 6a, b.

Colobostylus andrewsae ( Ancey, 1886) . Fischer & Crosse, 1890: 218; Simpson, 1897: 13; Géret, 1909: 13.

Chondropoma (Chondropomium) andrewsae ( Ancey, 1886) . Henderson & Bartsch, 1921: 60.

Choanopoma cozumelensis Richards, 1937: 256 , pl. 4, fig. 3; Richards, 1938: 174; Richardson et al., 1991: 42; Watters, 2006: 218.

Choanopoma andrewsae variety roatanense Richards, 1938: 169 , 174, 176, pl. 3, figs. 1, 7; Thompson, 1967: 225, 227 [in synonymy of Cyclostoma andrewsae Ancey, 1886 ]; Watters, 2006: 140, 227 [in synonymy of Cyclostoma andrewsae Ancey, 1886 ]; Thompson, 2011: 45 [in synonymy of Cyclostoma andrewsae Ancey, 1886 ].

Choanopoma (Choanopomops) andrewsae andrewsae ( Ancey, 1886) . Solem, 1961: 195, 198–200, pl. 10, fig. 9, pl. 12, fig. 24h, map 1.

Choanopoma (Choanopomops) cozumelensis Richards, 1937 . Solem, 1961: 195, 198–199, pl. 10, fig. 7, pl. 12, fig. 24g, map 1.

Choanopoma (Choanopomops) andrewsae roatanense Richards, 1938 . Solem, 1961: 200, pl. 10, fig. 10, pl. 12, fig. 24i, map 1.

Choanopoma cozumelense Richards, 1937 . Baker, 1964: 169; Parodiz & Tripp, 1988: 133.

Choanopoma roatanense Richards, 1938 . Baker, 1964: 170.

Choanopoma cozumelense Richards, 1937 . Thompson, 1967: 225, 227 [in synonymy of Cyclostoma andrewsae Ancey, 1886 ]; Thompson, 2011: 45 [in synonymy of Cyclostoma andrewsae Ancey, 1886 ].

Choanopoma andrewsae roatanense Richards, 1938 . Thompson, 1967: 225, 227 [in synonymy of Cyclostoma andrewsae Ancey, 1886 ].

Choanopoma cozumelense Richards, 1937 . Thompson, 1967: 225, 227 [in synonymy of Cyclostoma andrewsae Ancey, 1886 ]; Thompson, 2011: 45 [in synonymy of Cyclostoma andrewsae Ancey, 1886 ].

Choanopoma andrerosae [sic] roatanensis Richards, 1938 . Parodiz & Tripp, 1988: 146.

Annularia andrerosae [sic] roatanensis Richards, 1938 . Parodiz & Tripp, 1988: 146.

Choanopoma roatanensis Richards, 1938 . Richardson et al., 1991: 43.

Tudorisca andrewsae ( Ancey, 1886) . Watters, 2006: 79, 140.

Tudorisca cozumelensis ( Richards, 1937) . Watters, 2006: 79, 218.

Choanopoma (Choanopomops) andrewsae ( Ancey, 1886) . Thompson, 2011: 45, 282, 284, 291, 296.

Distribution and habitat. Limestone outcrops, fossilized coral, and archeological ruins across the Yucatán Peninsula and Isla de Cozumel, Isla de Utila, and Isla de Roatán. D. Dourson (pers. comm., 9 April 2014), records this species from Belize as well. Specimens occur on rock outcrops. Often abundant.

Although the entire island is karst (“limestone occurs almost everywhere on the island” Richards (1937: 258)), records for Isla de Cozumel are largely from just northeast of San Miguel, which has been more or less cleared for an airport and a golf course. Thus this distribution may be an artifact of collecting; most of the island is impenetrable jungle. The same is true for Isla de Utila where the collection localities are adjacent to the airfield. Collections are more widespread on Isla de Roatán, but are concentrated at West End, the most developed portion of the island.

Sporadically found specimens are known from across the central Yucatán Peninsula. These populations were first discovered by Thompson (2011), having escaped the attention of Solem and all others. Given the amount of collecting in Yucatán, this species appears to be quite rare on the mainland.

Conservation. Portions of the population occur in the Reserva de la Biosfera de Calakmul and probably other protected areas as well.

Other material (specimens examined: 914). Honduras. Isla de Roatán: GTW 15960b (1); UF 242669 (65), limestone ridge, West Bay; UF 224560 (37), coral limestone, E edge of Mangrove Bight; UF 224487 (38), limestone ridge 5.6 km NE of Oak Ridge; UF 224460 (70), limestone ridge W side of Oak Ridge Harbour; UF 224511 (89), point at West End Village; UF 224542 (153), limestone ridge, 0.5 km E of West Bay Village; UF 224521 (49), 1.6 km NE of West Bay Beach; GTW 15960a (25), W side of Carib Bight, 6– 12 m. Isla de Utila: UF 213708 (61), UF 216360 (6), UF 216367 (14); UF 224415 (31), coral limestone on coast, 3 km N of Utila; UF 224437 (66), Brand Hill. México. Isla de Cozumel: UF 213706 (1); UF 19125 (92), 1.5 km NNE of San Miguel; UF 19135 (6), 5.0 km NNE of San Miguel; UF 19133 (12), 6.0 km NNE of San Miguel; UF 19136 (11), 3.0 km E of San Miguel; UF 19127 (34), Santa Rita ruins. Quintana Roo State: UF 19139 (2), 3.7 km SSE of Polyuc; UF 19131 (8), 11.4 km NNW of Polyuc. Yucatán State: UF 19134 (7), 1.3 km NE of Becanchén; UF 19140 (2), 16.0 km NE of Becanchén. Campeche State: UF 19137 (1), 5.5 km S of Cayal; UF 19132 (12), 30.9 km E of Silvituc; UF 191281 (27), 8.2 km NNW of Dzitbalché; UF 19130 (14), 6.4 km E of Xpujil.

Description. Shell turbinate, low-spired, thin but solid. Smallest adult specimen seen 7.3 mm in length, largest 13.7 mm, average 10.3 mm (decollate). Protoconch lost in adult, 1.5 prominent, rounded, pale whorls. Teleoconch of 3.5–4 rounded whorls. Umbilicus wide, partially occluded by outer lip. Spiral sculpture obsolete except for 4–6 widely spaced low cords below the suture and 4–6 cords in the umbilicus of some specimens (see “Variation” below). Axial sculpture of numerous, crowded, fine rounded threads; this sculpture is stronger and more lamellate and widely separated on earlier whorls, which may be scalloped. Suture deeply incised. Tufts absent but axial lamella may render the suture finely serrate. Aperture nearly circular. Inner lip smooth, narrowly exserted. Outer lip strongly lamellate, widely reflected perpendicular to whorl, evenly expanded except narrow facing umbilicus, auriculate posteriorly, adnate to previous whorl. Base color dingy white to yellowish-tan, first teleoconch whorl darker in some specimens. Unicolor or with more or less continuous brown, spiral bands, occasionally broken into spots, bands lacking in umbilicus. Outer lip white; the bands do not extend to the front of the lip. Inside of aperture tan or white with the outer pattern showing through. Operculum paucispiral, with a thick, reflected, white plate that forms a flat, continuous surface. The operculum barely fits or is too large to fit into the aperture. Radula and anatomy unknown.

Variation in specimens. Specimens from Isla de Roatán are higher-spired than other populations, including those on neighboring Isla de Utila, which more closely resemble Yucatán and Cozumel specimens. These Isla de Roatán specimens were named Choanopoma andrewsae variety roatanense by Richards (1938). Richards (1937: 256) distinguished T. cozumelensis from T. andrewsae by “its chestnut dotted bands, its slightly more convex whorls and especially by its sculpture which is finer”—features shared however with mainland Yucatán specimens as well. The strength of the axial lamellae vary considerably resulting in sculpture ranging from nearly smooth to scalloped.

Comparison with other species. The combination of small, turbinate shape and the prominent, white, flat operculum sets this species apart from all others.

Remarks. This species was named after “Geo. Andrews” and clearly the correct orthography should be andrewsi rather than andrewsae . However, as this is not considered an inadvertant error, it should not be corrected (ICZN 32.5.1).

This species presents considerable problems of a zoogeographic nature. Several scenarios for the distribution of this species are possible, but concrete evidence supporting one or the other is lacking. 1) The Bay Islands are on a horst, the Banacca Ridge, which tectonically emerged during the Eocene/Oligocene. The fauna and flora of the islands must have originated elsewhere and been rafted to the islands. Prevailing currents would carry debris from the Bay Islands to Belize, Cozumel, and Yucatán but not the other direction, making the Bay Islands the potential source population. But from where did the Bay Islands populations originate? It is possible that this species, or its last common ancestor, occurred in mainland Honduras and was rafted to the islands; it has become extinct or remains undiscovered in mainland Honduras. From the islands it was rafted northwest to Yucatán (and possibly Cozumel). 2) This species may once have occurred throughout Yucatán/ Belize / Honduras, including offshore islands, but has been lost (or remains undiscovered) throughout much of this hypothesized range, leaving the patchy distribution we see today. 3) Tudorisca andrewsae is nearly inseparable from the Cayman Islands species Tudorisca rosenbergiana (Preston, 1911) , which itself is genetically close to Jamaican Tudorisca (Skomrock, Watters & Daly, in prep.). The Cayman Islands are downstream of Jamaica and it is possible that T. rosenbergiana is the descendant of a rafted Jamaican species. Prevailing currents could carry debris from the Cayman Islands to Yucatán/Cozumel, but at a distance of over 570 km. However, Censky et al. (1998) reported iguanas rafted from Guadeloupe to Anguilla by Hurricane Luis, a distance of over 200 km. 4) A last, intriguing theory involves anthropogenic dispersal. The majority of post-Columbian human inhabitants of the Honduran Bay Islands are descendants of ex-Cayman slaveholders and slaves who migrated there after Britain abolished slavery in 1838. They may have incidentally brought T. rosenbergiana with them, whose descendants have since colonized its current range.

Original description (translated here from Latin). Cyclostoma andrewsae Ancey, 1886 . “Shell clearly umbilicate, short ovate-pyramid, chestnut brown, actually wine-colored, elegantly striped decorated sometimes with wavy lines or darker brown as the apex is often broken by thin vanishing spirals; and a row crowded with slender silky lines and longitudinal to the other, more remote, raised; - spire subconical, truncate; - remaining 4 whorls very convex and rounded, fairly regularly, but rapidly increasing, suture a deep oblique more or less simple division; the last of which is well-rounded, spire short, the umbilical region and within it with impressed concentric grooved lines, aperture not solute, not abruptly descending; umbilicus open; - aperture not wide, subcircular-oval, with slight externally obtuse angle, rather narrow; peristome brown, double; inner part sometimes acutely raised; outer very widely reflexed, slightly concentric lamellae, in groups little by little less reflected, left margin but more dilated, angle above aperture slightly alate descending near the previous whorl. Alt. (shell decollate) 10 ½, diam. 8, alt. Aperture (outer) 5 ¾ millim. Var. minor , alt. 8 ½, diam. 6 ¼ millim. Operculum nearly as in Jamaican species, outside calcareous, flat, nucleus subspiral, corneous.”

Original description. Choanopoma cozumelensis Richards, 1937 . “The shell is narrowly umbilicate, elongate conic, truncate. The 3 ½ whorls retained are strongly convex, the embryonic whorls usually lost. Light brown with paler riblets; spiral series of sparse, unequal chestnut-brown dots are strongly developed on the two lower whorls, fainter on the upper whorls. Sculpture of fine, close, nearly regular axial riblets about 9 in 1 mm. On the last whorl, decidedly more widely spaced on the upper whorl retained; groups of two to three riblets project inconspicuously at the suture. Spiral sculpture developed only in the umbilical area, where there are several (4 to 6) coarse spiral cords. Aperture nearly circular. The flatly reflected peristome is widened at the posterior angle and slightly so at the columellar margin also, where it shows faint traces of fluting. Length 9.7 mm.; width 7.0 mm.; length of aperture with peristome 7.0 mm. Operculum white with gray nucleus above the lower third of the length; the last whorl with fine, somewhat irregular retractive striae.”

Original description. Choanopoma andrewsae variety roatanense Richards, 1938 . “Resembles the typical andrewsae Ancey except that the ribs are somewhat thinner and the shell is slightly more tapering. In some individuals a spiral series of sparse chestnut-brown dots are developed on the lower three whorls. In this respect the shell resembles C. cozumelensis Richards , but is distinguished by its thinner ribs and more slender shape. Length 10.25 mm; width 6.0 mm.; width of aperture 4.0 mm.”

Etymology. Cyclostoma andrewsae Ancey, 1886 : “Geo. Andrews.” Possibly George Reid Andrews, of the Royal Colonial Institute, sociologist and author on Central America, killed in Natal in 1898. Choanopoma cozumelensis Richards, 1937 : Cozumel + L. - ensis, from—from Cozumel. Choanopoma andrewsae roatanense Richards, 1938 : Roatán + l. - ensis, from—from Isla de Roatán.

Figures

FIGURE 7 A – K. Gouldipoma trochleare (Pfeiffer, 1852). A. NHMUK 20140099, probable syntype, ca. 14 mm. B. NHMUK 20140099, probable syntype, ca. 13 mm, both photos courtesy of J. Ablett (NHMUK). C – D. Chondropoma martensianum Pilsbry, 1900, ANSP 63417, lectotype, ca. 13 mm, photo courtesy of ANSP. E – F. UF 213709, 13.5 mm. G. UF 190678, 11.6 mm. H. UF 216382, 13.1 mm. I. GTW 13722 a, 10.3 mm. J – K. Grego coll., 12.0 mm. FIGURE 7 L – W. Tudorisca andrewsae (Ancey, 1886). L – M. UF 19125, 9.0 mm. N. UF 19127, 9.6 mm. O. UF 19125, 8.4 mm. P. UF 224415, 8.5 mm. Q. UF 224415, 7.6 mm. R. UF 242669, 12.5 mm. S. UF 242669, 10.9 mm. T. Choanopoma andrewsae roatanense Richards, 1938, FMNH 90606, paratype, 17.0 mm, photo courtesy of J. Gerber (FMNH). U. UF 19132, 9.9 mm. V. UF 19132, 9.9 mm. W. UF 19130, 11.3 mm.