Paper No. 2
Presentation Time: 8:00 AM-5:30 PM
PONDSNAIL PROBLEMS: INVESTIGATING THE LYMNAEIDAE
Although lymnaeid snails are common worldwide in Mesozoic to Recent freshwater settings and are important intermediate hosts of human and livestock parasites, their generic nomenclature is in chaos. Nearly 200 genera have been proposed. This reflects radical variation in classification philosophy, use of the family as a wastebasket for random freshwater snails, and genuine variability in a global, mid-Mesozoic to Recent taxon. Different authors currently recognize between 1 and about 50 genera and/or subgenera. The influential monograph of Hubendick (1951) argued for a single genus and only about 40 Recent species worldwide, but relied on misidentifications to "prove" extreme intraspecies variation. Conversely, Starobogatov, Kruglov, and colleagues, like the "Nouvelle École" a century before, recognize almost any variation as worthy of at least a species name. To sort this out, it has been necessary to review the entire family, including DNA sequencing of extant species, tracking down obscure literature, and morphological examination of fossils. Problematic fossil names include Pitharella, Berellaia, and Scalaxis, from the Paleocene of western Europe; Zalophancylus from the Neogene of the northwestern US.; Zagrabica from the Neogene of the Balkans; and Zaptychius, reportedly Carboniferous from western North America. Specimens of Pitharella in the Paleontological Research Institution enabled investigation, confirming that is not a lymnaeid but probably an acteonid instead. Zalophancylus is a fish vertebra impression; Zaptychius is a Cretaceous ellobiid; affinites of Zagrabica, Berellaia, and Scalaxis are less certain but Zagrabica is probably a large rissooidean. Problems exist among Recent names as well, such as Bocourtia, described as a southeast Asian lymnaeid with unspecified major anatomical differences from known species but actually a South American landsnail. The lymnaeids in the southeastern U.S. and Caribbean region are generally assignable to Galba (including Bakerilymnea), Polyrhytis (including North American "Stagnicola"), and Pseudosuccinea.