> Menetus dilatatus (Gould 1841)
    "Micromenetus dilatatus"

> Habitat & Distribution
The species ranges broadly through the eastern US from Florida and Texas up to Maine but not (oddly) to northern Michigan or into Canada.  In the southern Atlantic drainages it is a common inhabitant of ponds, swamps, and the quiet areas of rivers throughout the Piedmont and Coastal Plain, extending sporadically into the Blue Ridge, especially on vegetation and woody debris.  M. dilatatus populations seem to be able to tolerate more acidic water quality, and may be found in darker creeks and swamps in the lowcountry.

> Ecology & Life history
Jokinen (1985) reported three generations per year in a Connecticut population of M. dilatatus, following the D(iss) pattern of Dillon (2000: 156-162).  The data of Jokinen (1983) suggest that populations of the species tend to inhabit poor or peripheral environments in Connecticut.  My analysis suggested that the species displays Stress-tolerating life history adaptation (Dillon 2000: 360-363). 

> Taxonomy & Systematics
Burch (following Baker 1945) distinguished an M. brogniartianus (Lea 1842) by an especially carinate periphery on the shell.  But the shell periphery completely intergrades from rounded to angular within typical populations of Menetus in South Carolina, and thus brogniartianus is here considered a junior synonym.  

The classification of the Planorbidae proposed by the tag team of Baker (1945) and Hubendick (1955) remains, after 50 years, the basis for our understanding of this large and diverse family of pulmonates worldwide.   See Essay #1 below.  

Turgeon et al. (1998) raised the Baker's (1945) subgenus Micromenetus to the genus level, and placed dilatatus within it, with no justification offered.  I think that the problem may have been that Baker's concept of the genus Menetus contained two species, in violation of the strict "one species per genus rule" enforced throughout the North American freshwater Pulmonata.

> Essay #1
The Classification of the Planorbidae.  1 Figure.

> Hubendick (1955)
classification of the Planorbidae, applied to North America.

> Maps of Menetus distribution
Click the small map to enlarge it, or download the state-specific PDFs



North Carolina (PDF)

South Carolina (PDF)

Georgia (PDF)

> References
Baker, F. (1945) The Molluscan Family Planorbidae. Urbana: University of Illinois Press.  Baker, H. B. (1946) Index to F.C. Baker's "The Molluscan Family Planorbidae." Nautilus, 59, 127-41.  Dillon, R. T., Jr. (2000)  The Ecology of Freshwater Molluscs.  Cambridge University Press, United Kingdom.  509 pp.  Hubendick, B.  (1955)  Phylogeny in the Planorbidae.  Trans. Zool. Soc. London 28: 453-542.  Jokinen, E.  (1983)  The freshwater snails of Connecticut. Hartford, Connecticut, State Geol. Nat. Hist. Survey Bull. 109. 83 p.  Jokinen, E.  (1985)  Comparative life history patterns within a littoral zone snail community. Verh. Internat. Verein, Limnol., 22: 3292-3399.  Turgeon, D. D. et al. (1998)  Common and Scientific Names of Mollusks, Second edition.  Amer. Fisheries Soc. Sp. Publ. 26.