Plekocheilus (Eudolichotis) hauxwelli (Crosse, 1872)

Breure, Abraham S. H. & Avila, Valentin Mogollon, 2016, Synopsis of Central Andean Orthalicoid land snails (Gastropoda, Stylommatophora), excluding Bulimulidae, ZooKeys 588, pp. 1-199 : 6-8

Taxon classification Animalia Stylommatophora Amphibulimidae

Plekocheilus (Eudolichotis) hauxwelli (Crosse, 1872) Figs 12 A–F, 16

Bulimus hauxwelli Crosse 1872: 211; Crosse 1873: 252, pl. 11 fig. 2.

Type locality.

"in vicinio fluminis Ambiyacu, ad locum Pebas, Peruviae".

Type material.

MCZ 202073 (1), paratype.

Diagnosis.

See above.

Dimensions.

Shell height 50.6, diameter 18.5 mm.

Distribution.

Peru, Dept. Loreto, Pebas, banks of río Ampiyacu.

Ecoregion.

Iquitos varzea [NT0128].

Remarks.

Crosse did not state on how many specimens his description was based, but said his material was based on "(Coll. Orton)", and collected by John Hauxwell. The record of Breure (1979: 32) "HT MCZ" refers to specimen MCZ 202073 ("banks of Ambiyacu River near Pebas, Peru / Vassar College / James Orton"; see http://bit.ly/1fFP7xF), which was erroneous as Turner (1962) explained that in 1874 the type material-returned to Orton after the description by Crosse-has been transferred to the MCZ collection. Unfortunately, after Pilsbry used the holotype for his re-description, it "has since been misplaced or lost"; the MCZ specimen is thus a paratype, and was correctly mentioned as such by Breure (1978: 22). Pilsbry classified the species with his subgenus Plekocheilus (Eudolichotis) Pilsbry, 1896 and singled Plekocheilus (Eudolichotis) hauxwelli out in the key for the subgenus (Pilsbry 1896 [1895-1896]: 109), distinguishing it from Plekocheilus (Eudolichotis) distortus ( Bruguière, 1789) and Plekocheilus (Eudolichotis) aurissciuri (Guppy, 1866) by having (1) a "minutely, densely but irregularly scattered, papillose" sculpture on the last whorl; (2) "longitudinal groups of crowded, finely zigzag hydrophanous lines" on the dorsal side of the last whorl (Pilsbry 1896 [1895-1896]: pl. 44 fig. 78); (3) a narrow, "not calloused" lip. Many years later, Pilsbry (1944c) referred to this characteristics presented in this key to define his new subgenus Plekocheilus (Sparnotion) , with its sole species Plekocheilus (Simpulopsis) hauxwelli . This subgenus has been recognised by Zilch (1960: 476, fig. 1674), and Breure (1979: 32); Schileyko (1999: 277: fig. 334) expressed some doubt about its status by placing a question mark, but did not explicitly comment on this in his text.

The loss of the holotype of Bulimus hauxwelli makes it necessary to judge this taxon-and the subgenus Sparnotion -largely on the basis of the figures provided by Pilsbry and the remaining paratype in MCZ. As far as we know there is no material with proven locality data present in other museum collections. However, we recently had the opportunity to re-study the specimen in MCZ on the basis of high resolution pictures supplied by Adam Baldinger. As noted earlier ( Breure 1978: 22), the paratype does not show the "longitudinal groups of crowded, finely zigzag hydrophanous lines" very clearly and this could hardly be compared to the subcuticular cavities filled with air characteristic for Plekocheilus (Aeropictus) ; see also Borrero and Breure 2011: fig. 6 for shell sculptures of several Plekocheilus species. While the paratype shell shows a papillose sculpture of the last whorl (unfortunately not clearly shown on the picture), we think this sculpture is not atypical compared to the known species of Plekocheilus (Eudolichotis) . The sprout in the basal lip seems stronger than in Crosse’s or Pilsbry’s figures; this may be a sign for intra-specific variation. Finally, the narrow and 'not calloused’ lip reminds of several Plekocheilus (Eurytus) species and we hardly doubt if this characteristic alone may be sufficient for a subgeneric separation of this species.

When this manuscript was being finalized, we received information about a specimen with locality “Peru” in the RAMM collection. This specimen originates from the collection of Miss J.E. Linter (1844-1909) and is the sole specimen we have been able to trace apart from the type material. This specimen (Figs 12 D–F) does show the characteristics that Pilsbry mentioned for the lost holotype. And although there seems some mixing in of a characteristic-zigzag hydrophanous lines-from Plekocheilus (Aeropictus) , based on the shell morphology alone we conclude that this species may be best classified as Plekocheilus (Eudolichotis) hauxwelli untill more material, hopefully allowing for anatomical and molecular studies, becomes available.