Echinolittorina nielseni, Araya & D. Reid, 2016

Araya, Juan Francisco & Reid, David G., 2016, A new species of Echinolittorina Habe, 1956 (Gastropoda: Littorinidae) from the Quaternary of Chile, Palaeontologia Electronica 19 (1), pp. 1-8 : 2-5

publication ID	https://doi.org/ 10.26879/600
publication LSID	lsid:zoobank.org:pub:A----
persistent identifier	https://treatment.plazi.org/id/03ACB001-FFBE-D820-6ED9-F9613B31FC44
treatment provided by	Felipe
scientific name	Echinolittorina nielseni
status	sp. nov.

Treatment

Echinolittorina nielseni View in CoL sp. nov.

Figure 2.1 View FIGURE 2 -8

zoobank.org/ DD2906C5-7FE3-4DFF-9C50-5A2471AADDA3

PALAEO- ELECTRONICA.ORG

v. 2015 Echinolittorina n. sp.; Araya and Reid, p. 85, figs 1.A-H.

Diagnosis. Large, broad Echinolittorina with rounded whorls, concave spire profile, 7–9 strong spiral ribs at and above angled periphery.

Description. Shell large (H = 15.7–22.2 mm). Shape high turbinate (H/B = 1.29–1.44; H/LA = 1.54–1.83); spire whorls well rounded, suture distinct; spire profile concave near apex; periphery of last whorl slightly but distinctly angled; rarely a slight angulation at shoulder ( Figure 2.6 View FIGURE 2 -7). Columella straight, moderately broad, slightly hollowed and pinched at base; no eroded parietal area. Sculpture of 7–9 low, broad, rounded, spiral ribs above periphery (including the strongest rib at periphery), becoming less distinct near suture; ribs of unequal width and prominence, separated by narrow grooves or incised lines. Base with 6–8 finer ribs. No spiral microstriae visible. A trace of colour is preserved on one specimen, showing a pale spiral band on the base ( Figure 2.4 View FIGURE 2 ). None of the specimens showed fluorescence under ultraviolet light, which might have revealed original colour patterns.

Type material. Holotype: SGO. PI 23.100 ( Figure 2.1-2 View FIGURE 2 ) ; Paratypes NHMUKPAL PI TG 26769– 26775 ( Figure 2.3 View FIGURE 2 -8, seven specimens), MPCCL 14012016 (fifteen specimens). All the material collected at type locality by J. F. Araya, January 15, 2012 .

Type locality. Eroded cliff east of El Morro Hill, about 10 km south of Caldera, Región de Atacama, northern Chile (27°09’13”S; 70°55’33”W, 123 m); Pleistocene GoogleMaps .

Etymology. The name of the species honours our friend Sven Nielsen (Universidad Austral de Chile, Valdivia, Chile) for his extensive research on Chilean fossil molluscs.

Remarks. These relatively large, thick, spirallysculptured shells with an entire aperture containing a basal white band, and lacking an umbilicus, unquestionably belong to the subfamily Littorininae (reviewed by Reid, 1989) and can be compared with members of its living genera. Superficially, the shells resemble members of the littorinid genus Littoraria ; this assignment is suggested by the strong spiral sculpture, the enlarged peripheral rib that gives an angled profile to the final whorl, and the somewhat short and wide columella. In the recent fauna six Littoraria species occur on the Pacific mainland coast of Central and South America, but all have a tropical distribution and five are almost entirely restricted to mangrove and halophyticgrass habitats. The one rocky-shore species ( Littoraria pintado [ Wood, 1828]; see Reid, 1999a; Reid et al., 2010) can be discounted because it is smooth-shelled and relatively narrow with a straight spire. The most southerly records of living Littoraria species are between 3° and 5°S in northernmost Peru ( Reid, 1999a). Since the present fossil sample is from 27°S in northern Chile and accompanied by a fauna of temperate, rocky-shore gastropods, their identification as a Littoraria species associated with mangrove trees would be extremely surprising. Of the living Littoraria species, the new species most closely resembles Littoraria varia ( Sowerby, 1832) (see Reid, 1999a) ( Figure 2.14 View FIGURE 2 -15). However, close comparison shows that the sculpture of L. varia is stronger, the primary spiral ribs more equal in width, and that they are separated by wide grooves with secondary ribs and fine spiral microstriae, quite unlike the rounded ribs separated by grooves that are little more than incised lines in the new species. The peripheral angle is marked by a strong rib in L. varia , and there is sometimes a slight angle at the shoulder as well ( Figure 2.14 View FIGURE 2 ), which are points of similarity with the fossils (compare with Figure 2.6 View FIGURE 2 - 7). One of the fossil shells bears a spiral white band on the base ( Figure 2.4 View FIGURE 2 ); this band is weakly present (and then only within the aperture) in only three of the 39 living Littoraria species ( Reid, 1999b), but is present in a variety of other littorinid genera ( Reid, 1989), including all members of the genus Echinolittorina ( Reid, 2002, 2007, 2009, 2011). The sculptural details and presence of the white basal band exclude the present shells from Littoraria .

Turning to the modern rocky-shore fauna of the eastern Pacific Ocean, there are 18 littorinid species in the genera Echinolittorina and Austrolittorina (see Reid, 2002 for detailed descriptions and Reid et al., 2012 for current generic assignments based on molecular phylogeny). All have a basal white band visible within the aperture and often externally as well. None of the members of Echinolittorina in the tropical eastern Pacific is similar to the new species, being smaller, narrower, usually with regular spiral grooves, and sometimes nodulose or umbilicate. Two of the three temperate littorinid species can also be discounted: Austrolittorina fernandezensis ( Rosewater, 1970) is large (to 21 mm), but macroscopically smooth, and is endemic to the Juan Fernández Archipelago, off central Chile; Austrolittorina araucana (d’Orbigny, 1840) is common in Chile, again macroscopically smooth, but does not exceed 13.8 mm in height. The only other living littorinid in the southeastern Pacific is Echinolittorina peruviana ( Lamarck, 1822) . This is a well-known species, common on temperate shores from northern Peru to southern Chile (5°05’S to 41°49’S; Reid, 2002; Castillo and Brown, 2010), where it is found in local assemblages that are much the same as that in which the fossil shells occurred. It too can reach a large size, up to 23.8 mm high. However, shells of E. peruviana are usually smooth, relatively elongate (H/B = 1.31–1.88; H/LA = 1.46–1.93), the whorls are not swollen, the columella is long and the anterior apertural margin protrudes slightly ( Figure 2.9 View FIGURE 2 -12) ( Reid, 2002)—characters which at first appear to exclude close relationship with the new species. However, a very few shells of E. peruviana (13/884 = 1.4% of shells examined from throughout geographical range) show “1–4 (rarely 6–8) faint incised lines above periphery” ( Reid, 2002: 147) (Figure 2.9,12-13). Sometimes, even in smooth shells, irregularities in the axial colour stripes show a periodicity similar to that of the incised spiral lines (compare Figure 2.11 and 2.12 View FIGURE 2 ). The incised lines are shown more clearly in an SEM of a well-preserved juvenile shell ( Figure 2.13 View FIGURE 2 ). The spacing of the incised spiral lines in these rare shells of E. peruviana is not as regular as the ‘primary spiral grooves’ of typical tropical Echinolittorina species (e.g., Reid, 2002), instead recalling the somewhat unequal ribs of the fossils. It is, therefore, proposed that E. nielseni sp. nov. is a member of Echinolittorina and is most closely related to E. peruviana .