Evalea amchitkana, from Dall & Bartsch (1909).

Belongs within: Pyramidellidae.

Evalea is an Indo-Pacific genus of pyramidellid snails characterised by shells with a strong spiral sculpture and a columellar tooth.

The sandflies of the sea

Though spectacularly diverse, the tinier molluscs of the world tend to escape taxonomic scrutiny owing to the challenge of working with them. Perhaps this is never more evident than when considering the marine snail family Pyramidellidae. Among the most speciose of all gastropod families, pyramidellids remain poorly known. Their shells rarely grow more than a few millimetres in length, and the features distinguishing species are correspondingly fine and obscure. In 1955, malacologist Paul Bartsch recalled once facetiously suggesting to a colleague that pyramidellid specimens might be best assigned to genus by simply drawing lots.

Evalea eclecta, from the Academy of Natural Sciences.

Evalea is one of these pyramidellid genera that Bartsch found so challenging. It differs from other pyramidellids in possessing ovate to subconic shells with a single columellar fold and ornament of spiral striations. Bartsch (1955) treated Evalea as a subgenus of Odostomia, which possesses a similar shell but lacks the spiral striations, but more modern authors deal with them as separate genera. Within the modern fauna, Evalea seems to be a strictly Indo-Pacific genus; Atlantic species historically included in Evalea lack the columellar fold and have been transferred to the distinct genus Ondina (Pimenta et al. 2018).

Pyramidellids might be thought of as the mosquitoes of the marine environment. They lack a radula, instead possessing a retractable proboscis. This proboscis is used to pierce the body wall of other molluscs or marine worms and suck out tissues or bodily fluids. Infestations of pyramidellids have been accused of causing poor growth, increased mortality, or increased disease rates in economically significant molluscs. One Evalea species, E. tenuisculpta (a positive giant among pyramidellids, reaching shell lengths of nearly nine millimetres), has been investigated for its impact on abalone populations on the West coast of North America (Maguire & Rogers-Bennett 2013). However, their overall impact on hosts remains poorly understood. Do pyramidellids reach plague levels under normal conditions, or are infestations a side-effect of factors such as host overcrowding or poor water quality? Do pyramidellids act as direct vectors of pathogens in the manner of mosquitoes, or are weakened hosts just more vulnerable to secondary infections? These are questions still worthy of study.

Systematics of Evalea
<==Evalea Adams 1860P61
    |--*E. elegansP61
    |--E. aequisculpta [=Odostomia aequisculpta]C64
    |--E. aleutica (Dall & Bartsch 1909) [=Odostomia (Evalea) aleutica]O27
    |--E. altina (Dall & Bartsch 1909) [=Odostomia (Evalea) altina]O27
    |--E. amchitkana (Dall & Bartsch 1909) [=Odostomia (Evalea) amchitkana]O27
    |--E. angularis (Dall & Bartsch 1907) [=Odostomia (Evalea) angularis]O27
    |--E. atossa (Dall 1908) [=Odostomia (Evalea) atossa]O27
    |--E. bachia (Bartsch 1927) [=Odostomia (Evalea) bachia]O27
    |--E. balbridgae (Bartsch 1912) [=Odostomia (Evalea) balbridgae]O27
    |--E. baranoffensis (Dall & Bartsch 1909) [=Odostomia (Evalea) baranoffensis]O27
    |--E. barkleyensis (Dall & Bartsch 1910) [=Odostomia (Evalea) barkleyensis]O27
    |--E. calcarella (Bartsch 1912) [=Odostomia (Evalea) calcarella]O27
    |--E. californica (Dall & Bartsch 1909) [=Odostomia (Evalea) californica]O27
    |--E. callimene (Bartsch 1912) [=Odostomia (Evalea) callimene]O27
    |--E. calliope (Bartsch 1912) [=Odostomia (Evalea) calliope]O27
    |--E. capitana (Dall & Bartsch 1909) [=Odostomia (Evalea) capitana]O27
    |--E. cassandra (Bartsch 1912) [=Odostomia (Evalea) cassandra]O27
    |--E. clessini (Dall & Bartsch 1909) [=Odostomia (Evalea) clessini]O27
    |--E. columbiana (Dall & Bartsch 1907) [=Odostomia (Evalea) columbiana]O27
    |--E. cookeana (Bartsch 1912) [=Odostomia (Evalea) cookeana]O27
    |--E. cypria (Dall & Bartsch 1910) [=Odostomia (Evalea) cypria]O27
    |--E. delicatula [=Odostomia delicatula]C64
    |--E. deliciosa (Dall & Bartsch 1907) [=Odostomia (Evalea) deliciosa]O27
    |--E. donilla (Dall & Bartsch 1909) [=Odostomia (Evalea) donilla]O27
    |--E. edmondi (Jordan 1920) [=Odostomia (Evalea) edmondi]O27
    |--E. esilda (Dall & Bartsch 1909) [=Odostomia (Evalea) esilda]O27
    |--E. eyerdami (Bartsch 1927) [=Odostomia (Evalea) eyerdami]O27
    |--E. franciscana (Bartsch 1917) [=Odostomia (Evalea) franciscana]O27
    |--E. gravida (Gould 1852) [=Odostomia (Evalea) gravida]O27
    |--E. hagemeisteri (Dall & Bartsch 1909) [=Odostomia (Evalea) hagemeisteri]O27
    |--E. herilda (Dall & Bartsch 1909) [=Odostomia (Evalea) herilda]O27
    |--E. huttoni Suter 1907F27
    |--E. hypatia (Dall & Bartsch 1912) [=Odostomia (Evalea) hypatia]O27
    |--E. inflata (Carpenter 1865) [=Odostomia (Evalea) inflata]O27
    |--E. io (Dall & Bartsch 1903) [=Odostomia (Evalea) io]O27
    |--E. jewetti (Dall & Bartsch 1907) [=Odostomia (Evalea) jewetti]O27
    |--E. kadiakensis (Dall & Bartsch 1909) [=Odostomia (Evalea) kadiakensis]O27
    |--E. killisnooensis (Dall & Bartsch 1909) [=Odostomia (Evalea) killisnooensis]O27
    |--E. liricincta (Suter 1908)P61
    |--E. minutissima (Dall & Bartsch 1909) [=Odostomia (Evalea) minutissima]O27
    |--E. movilla (Dall & Bartsch 1909) [=Odostomia (Evalea) movilla]O27
    |--E. nemo (Dall & Bartsch 1909) [=Odostomia (Evalea) nemo]O27
    |--E. notilla (Dall & Bartsch 1909) [=Odostomia (Evalea) notilla]O27
    |--E. nunivakensis (Dall & Bartsch 1909) [=Odostomia (Evalea) nunivakensis]O27
    |--E. obesa (Dall & Bartsch 1909) [=Odostomia (Evalea) obesa]O27
    |--E. obsoleta Murdoch 1900F27
    |--E. phanea (Dall & Bartsch 1907) [=Odostomia (Evalea) phanea]O27
    |--E. phanella (Dall & Bartsch 1909) [=Odostomia (Evalea) phanella]O27
    |--E. plana Laws 1941P61
    |--E. pratoma (Dall & Bartsch 1909) [=Odostomia (Evalea) pratoma]O27
    |--E. profundicola (Dall & Bartsch 1909) [=Odostomia (Evalea) profundicola]O27
    |--E. propria Laws 1941P61
    |--E. quadrae (Dall & Bartsch 1910) [=Odostomia (Evalea) quadrae]O27
    |--E. raymondi (Dall & Bartsch 1909) [=Odostomia (Evalea) raymondi]O27
    |--E. resina (Dall & Bartsch 1909) [=Odostomia (Evalea) resina]O27
    |--E. sabulosa (Suter 1908)P61 [=Menestho sabulosaF27]
    |--E. santarosana (Dall & Bartsch 1909) [=Odostomia (Evalea) santarosana]O27
    |--E. septentrionalis (Dall & Bartsch 1909) [=Odostomia (Evalea) septentrionalis]O27
    |--E. serilla (Dall & Bartsch 1909) [=Odostomia (Evalea) serilla]O27
    |--E. sitkaensis (Clessin 1900) [=Odostomia (Evalea) sitkaensis]O27
    |--E. skidegatensis (Bartsch 1912) [=Odostomia (Evalea) skidegatensis]O27
    |--E. spreadboroughi (Dall & Bartsch 1910) [=Odostomia (Evalea) spreadboroughi]O27
    |--E. stephensae (Dall & Bartsch 1909) [=Odostomia (Evalea) stephensae]O27
    |--E. strongi (Bartsch 1927) [=Odostomia (Evalea) strongi]O27
    |--E. tacomaensis (Dall & Bartsch 1907) [=Odostomia (Evalea) tacomaensis]O27
    |--E. tenuisculpta (Carpenter 1864) [=Odostomia (Evalea) tenuisculpta]O27
    |--E. thea (Bartsch 1912) [=Odostomia (Evalea) thea]O27
    |--E. tillamookensis (Dall & Bartsch 1907) [=Odostomia (Evalea) tillamookensis]O27
    |--E. unalashkensis (Dall & Bartsch 1909) [=Odostomia (Evalea) unalashkensis]O27
    |--E. valdezi (Dall & Bartsch 1907) [=Odostomia (Evalea) valdezi]O27
    |--E. vancouverensis (Dall & Bartsch 1910) [=Odostomia (Evalea) vancouverensis]O27
    |--E. whitei (Bartsch 1927) [=Odostomia (Evalea) whitei]O27
    |--E. willetti (Bartsch 1917) [=Odostomia (Evalea) willetti]O27
    `--E. youngi (Dall & Bartsch 1912) [=Odostomia (Evalea) youngi]O27

*Type species of generic name indicated


Bartsch, P. 1955. The pyramidellid mollusks of the Pliocene deposits of North St. Petersburg, Florida. Smithsonian Miscellaneous Collections 125 (2): 1–102, 118 pls.

[C64] Carpenter, P. P. 1864. Supplementary report on the present state of our knowledge with regard to the Mollusca of the west coast of North America. Report of the British Association for the Advancement of Science 33: 517–686.

[F27] Finlay, H. J. 1927. A further commentary on New Zealand molluscan systematics. Transactions and Proceedings of the New Zealand Institute 57: 320–485.

Maguire, A. K., & L. Rogers-Bennett. 2013. An ectoparasitic snail (Evalea tenuisculpta) infects red abalone (Haliotis rufescens) in northern California. California Fish and Game 99 (2): 80–89.

[O27] Oldroyd, I. S. 1927. The Marine Shells of the West Coast of North America vol. 2 pt 2. Stanford University Press: Stanford University (California).

Pimenta, A. D., F. N. Santos & C. M. Cunha. 2018. Redescription and reassignment of Ondina semicingulata to the Pyramidellidae, with review of the occurrence of genus Evalea in the western Atlantic (Gastropoda). Zoosystematics and Evolution 94 (2): 535–544.

[P61] Powell, A. W. B. 1961. Shells of New Zealand: An illustrated handbook 4th ed. Whitcombe and Tombs Limited: Christchurch.

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