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Potamilus capax

(Green, 1832)

Fat Pocketbook

G3Vulnerable Found in 2 roadless areas NatureServe Explorer →
G3VulnerableGlobal Rank
VulnerableIUCN
MediumThreat Impact
Fat pocketbook (Potamilus capax). Photo by U.S. Fish & Wildlife Service, Public Domain (U.S. Government Work), via ECOS.
U.S. Fish & Wildlife Service, https://www.usa.gov/government-works
Identity
Unique IDELEMENT_GLOBAL.2.109746
Element CodeIMBIV37030
Record TypeSPECIES
ClassificationSpecies
Classification StatusStandard
Name CategoryInvertebrate Animal
IUCNVulnerable
CITESAppendix I
Endemicendemic to a single nation
KingdomAnimalia
PhylumMollusca
ClassBivalvia
OrderUnionoida
FamilyUnionidae
GenusPotamilus
Synonyms
Proptera capax(Green, 1832)
Other Common Names
Fat Pocketbook Pearly Mussel (EN)
Concept Reference
Turgeon, D. D., J. F. Quinn, Jr., A. E. Bogan, E. V. Coan, F. G. Hochberg, W. G. Lyons, P. M. Mikkelsen, R. J. Neves, C. F. E. Roper, G. Rosenberg, B. Roth, A. Scheltema, F. G. Thompson, M. Vecchione, and J. D. Williams. 1998. Common and scientific names of aquatic invertebrates from the United States and Canada: Mollusks. 2nd Edition. American Fisheries Society Special Publication 26, Bethesda, Maryland. 526 pp.
Taxonomic Comments
This is a member of the widely distributed genus Potamilus. This species was formerly placed in the genus Proptera which was widely used in the 1950s and 1960s. A recent ruling published in the Bulletin of Zoological Nomenclature (ICZN, 1992) recommended retention of the older name Potamilus. In an analysis of systematic relationships of species in the genus Potamilus using DNA sequence data, Roe and Lydeard (1998) concluded that Potamilus is paraphyletic with Leptodea fragilis and Lampsilis ornata nested between Potamilus capax and the remaining Potamilus species (all of which appeared to be monophyletic). Roe and Lydeard (1998) placed Potamilus capax outside the remaining members of Potamilus in their phylogenetic tree indicating possible affinities with other taxa but did not go so far as to formally recommend a genus in which to place P. capax, although Simpson (1914) placed it in Lampsilis.
Conservation Status
Rank Method Rank calculation - Biotics v2
Review Date2024-01-08
Change Date2024-01-08
Edition Date2024-01-08
Edition AuthorsCummings, K.S. (1997); rev. J. Cordeiro (2011); rev. T. Cornelisse (2024)
Threat ImpactMedium
Range Extent1000-20,000 square km (about 400-8000 square miles)
Number of Occurrences21 - 80
Rank Reasons
This species has a moderate range and number of occurrences and despite historical population declines and several ongoing threats, populations are stable to improving in recent years.
Range Extent Comments
This species occurs in the St. Francis, Wabash, Ohio, and Lower Mississippi Rivers and drainages in Arkansas, Illinois, Missouri, Indiana, Kentucky, Louisiana, and Mississippi, USA (USFWS 2012, 2019; GBIF 2024).
Occurrences Comments
This species is known from 33 streams and occurrences (USFWS 2019).
Threat Impact Comments
This species is threatened by habitat loss and degradation associated with dams and other waterway barriers, channelization, and dredging operations; pollutants from illegal discharges or spills from industrial operations; and sedimentation from land disturbance activities, such as development and agriculture implemented without adequate measures to control runoff (USFWS 2012, 2019).
Ecology & Habitat

Description

Shell round to somewhat oblong, greatly inflated, and thin (young) to moderately thick (adults). Anterior and posterior ends rounded. Umbos greatly inflated, elevated, and turned inward. Beak sculpture consists of a few faint ridges, visible only in young shells. Small posterior wing present in young mussels. Surface usually smooth and very shiny. Periostracum rayless, yellow, yellowish tan or olive, becoming dark brown in older individuals. Length to 5 inches.

Pseudocardinal teeth thin, compressed, and elevated; two in each valve. Lateral teeth thin and greatly curved; two in the left valve, one in the right. Hinge line S-shaped. Beak cavity very deep. Nacre white, sometimes tinged with pink or salmon in the beak cavity.

Habitat

This species is found in medium to large rivers in sand, mud, and fine gravel substrates and slow flowing water, often near river banks, as well as in artificial ditches, sloughs, and streams (Dennis 1985; Cummings et al. 1990; Miller and Payne 2005).
Other Nations (1)
United StatesN3
ProvinceRankNative
OhioSXYes
IndianaS1Yes
MissouriS1Yes
IowaSXYes
New YorkSHYes
MinnesotaSXYes
TennesseeSNRYes
KentuckyS2Yes
ArkansasS2Yes
MississippiS1Yes
LouisianaS1Yes
WisconsinSXYes
IllinoisS2Yes
Threat Assessments
ThreatScopeSeverityTiming
4 - Transportation & service corridorsRestricted (11-30%)Moderate or 11-30% pop. declineHigh (continuing)
4.3 - Shipping lanesRestricted (11-30%)Moderate or 11-30% pop. declineHigh (continuing)
7 - Natural system modificationsRestricted (11-30%)Moderate or 11-30% pop. declineHigh (continuing)
7.2 - Dams & water management/useRestricted (11-30%)Moderate or 11-30% pop. declineHigh (continuing)
9 - PollutionLarge (31-70%)Moderate or 11-30% pop. declineHigh (continuing)
9.2 - Industrial & military effluentsRestricted (11-30%)Moderate or 11-30% pop. declineHigh (continuing)
9.3 - Agricultural & forestry effluentsRestricted (11-30%)Moderate or 11-30% pop. declineHigh (continuing)
9.3.2 - Soil erosion, sedimentationRestricted (11-30%)Moderate or 11-30% pop. declineHigh (continuing)

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Roadless Areas (2)
Idaho (1)
AreaForestAcres
Bear CreekCaribou-Targhee National Forest118,582
Illinois (1)
AreaForestAcres
Burke BranchShawnee National Forest6,231
References (63)
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