Truncilla macrodon - (I. Lea, 1859)
Texas Fawnsfoot
Taxonomic Status: Accepted
Related ITIS Name(s): Truncilla macrodon (I. Lea, 1859) (TSN 80168)
Unique Identifier: ELEMENT_GLOBAL.2.120471
Element Code: IMBIV45030
Informal Taxonomy: Animals, Invertebrates - Mollusks - Freshwater Mussels
 
Kingdom Phylum Class Order Family Genus
Animalia Mollusca Bivalvia Unionoida Unionidae Truncilla
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Concept Reference
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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.
Concept Reference Code: B98TUR01EHUS
Name Used in Concept Reference: Truncilla macrodon
Conservation Status
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NatureServe Status

Global Status: G1
Global Status Last Reviewed: 28Nov2018
Global Status Last Changed: 28Nov2018
Ranking Methodology Used: Ranked by calculator
Rounded Global Status: G1 - Critically Imperiled
Reasons: The species is endemic to Texas and has, historically and currently, a small geographic range. It has been extirpated from perhaps as much as 85% of its historic range. There are 2-3 viable populations. The overall population ?may already be below the minimum viable population requirement,? as per USFWS? (2016:87258) assessment. Threats are considered very high and imminent and are ?likely to result in the extinction of the Texas Fawnsfoot in the foreseeable future? (USFWS 2016:87258).
Nation: United States
National Status: N2 (30May1998)

U.S. & Canada State/Province Status
Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
United States Oklahoma (S4?), Texas (S1)

Other Statuses

U.S. Endangered Species Act (USESA): C: Candidate (06Oct2011)
Comments on USESA: In a 12-month petition finding, USFWS (October 6, 2011) found listing this species to be warranted but precluded by higher priority actions. It has been added to the candidate species list. As of November 22, 2013, there is no change in status and listing is still warranted-but-precluded by higher priority actions (USFWS 2013).
U.S. Fish & Wildlife Service Lead Region: R2 - Southwest
American Fisheries Society Status: Endangered (01Jan1993)

NatureServe Global Conservation Status Factors

Range Extent: 20,000-200,000 square km (about 8000-80,000 square miles)
Range Extent Comments: Cordeiro (2007) commented: Historically known from the Colorado, Trinity, and Brazos River drainages in Central Texas (Howells et al., 1996). Branson (1984) includes it as potentially in Oklahoma without any confirmed occurrences but based solely on Burch's (1975) statement "Texas to Oklahoma", however, all of Strecker's (1931) localities (Llano, Colorado, Bosque, Brazos, Little River drainages) lie south of the Red River drainage. It appears to still survive in very small numbers over several hundred miles of the Central Brazos River drainage.

Smith-Patten (2018) added: The species is currently known from portions of the Brazos, Colorado, and San Saba Rivers. Isolated/remnant populations appear to persist in the Clear Fork Brazos River and Deer Creek. Reports from the Trinity River are considered to actually be of Truncilla donaciformis (USFWS 2015). The species is not known from Oklahoma.

Area of Occupancy: 126-2,500 4-km2 grid cells
Area of Occupancy Comments: Used 1-km2 grid cells because this is a linear species. Estimates of AOO ranged from 30 to 43 1-km2 grid cells.

Number of Occurrences: 1 - 5
Number of Occurrences Comments: Smith-Patten (2018) added to comments: USFWS (2016:87258) estimated that there are five extant populations with only three that ?are likely to be stable and recruiting; the remaining populations are disjunct to short stream reaches.?

Cordeiro (2007) commented: Historically, Strecker (1931) listed several localities: Llano River in Mason Co., Colorado River in Burnet and Colorado Cos., Bosque River in McLennan Co., Aquilla Creek in McLennan Co., Brazos River in McLennan Co., Leon River in Coryelle Co., Brazos River in Robertson Co. Since 1980, living or recently dead specimens have been found on the Clear Fork of the Brazos River and in the main channel of the Brazos River (Howells et al., 1996; 1997). However, no specific centers of population or beds have been located with the exception of possibly the Brazos River in Washington Co.. A single undocumented specimen reportedly taken in the San Angelo area is the only recent evidence of continued survival anywhere in the Colorado River system (Howells et al., 1996; 1997). Seven live individuals were also found in the Brazos River in Washington Co. (Reimer and Linam, 2005). The second largest population in Texas was recently found on the San Saba River (Agrilife Today, 2011).

Population Size: 1000 - 100,000 individuals
Population Size Comments: Cordeiro (2007) commented: Approximately 40-50 specimens have been documented since 1980 and many of these were recently dead animals, but few actual living animals have been found. Seven live individuals were also found in the Brazos River in Washington Co. (Reimer and Linam, 2005).

Smith-Patten (2018) added: Burlakova et al. (2011) determined Truncilla macrodon to be ?rare.? Burlakova and Karatayev (2012) provided population estimates that ranged from 1511-42069 individuals.

Number of Occurrences with Good Viability/Integrity: Very few (1-3)

Overall Threat Impact: Very high
Overall Threat Impact Comments: USFWS (2015, 2016) considered the primary threat to this species to be habitat loss and degradation from impoundments, contributing to scouring of riverbeds, sedimentation, modified stream flows, and decreased water quality. Concern was also expressed about dewatering and the restriction of ?fish host migration and distribution of freshwater mussels.? Additional threats include the many sand and gravel mining operations found in the region, pollution of waterways, and the high probability that climate change will exacerbate threats. The species is considered ?highly vulnerable to stochastic events? (USFWS 2015). Additionally, there is concern about contaminants, including, but not limited to, ammonia, nitrogen, phosphorus, copper, mercury, pharmaceuticals, hormones, and oil spills. Three non-native invasive species, golden algae, zebra mussel, and the black carp, have been identified as threats or potential threats.

Short-term Trend: Decline of >90%
Short-term Trend Comments: Threats are considered very high and imminent and are ?likely to result in the extinction of the Texas Fawnsfoot in the foreseeable future? (USFWS 2016:87258). Cordeiro (2007) previously commented: Riverine mussel populations have been declining dramatically in recent decades in Central Texas due to a variety of conditions. Because environmental problems associated with these losses are complex and far reaching, quick resolution of these situations and restoration of aquatic ecoystems are unlikely.

Long-term Trend: Decline of 30-50%
Long-term Trend Comments: The species has lost approximately 36-50% of its historical range

Intrinsic Vulnerability: Unknown

Environmental Specificity: Narrow. Specialist or community with key requirements common.
Environmental Specificity Comments: Little is known about habitat requirements for this species. Only a few specimens have been found alive or recently dead. Since 1980. It is likely these were washed or otherwise removed from their preferred microhabitat sites which remain undetermined. Texas fawnsfoot appears to prefer rivers and larger streams. Living specimens have not been documented in reservoirs suggesting intolerance of impoundment, but has also been found alive in the past in flowing rice irrigation canals. It probably prefers sand, gravel, and perhaps sandy-mud bottoms in moderate flows.

Other NatureServe Conservation Status Information

Inventory Needs: Despite work by Texas Parks and Wildlife Department (Howells 1996, 1997) and others (Howells et al. 1997), most recent specimens are represented only by recently dead shells. Living animals remain illusive suggesting exact microhabitat sites remain to be discovered and defined.

Distribution
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Global Range: (20,000-200,000 square km (about 8000-80,000 square miles)) Cordeiro (2007) commented: Historically known from the Colorado, Trinity, and Brazos River drainages in Central Texas (Howells et al., 1996). Branson (1984) includes it as potentially in Oklahoma without any confirmed occurrences but based solely on Burch's (1975) statement "Texas to Oklahoma", however, all of Strecker's (1931) localities (Llano, Colorado, Bosque, Brazos, Little River drainages) lie south of the Red River drainage. It appears to still survive in very small numbers over several hundred miles of the Central Brazos River drainage.

Smith-Patten (2018) added: The species is currently known from portions of the Brazos, Colorado, and San Saba Rivers. Isolated/remnant populations appear to persist in the Clear Fork Brazos River and Deer Creek. Reports from the Trinity River are considered to actually be of Truncilla donaciformis (USFWS 2015). The species is not known from Oklahoma.

U.S. States and Canadian Provinces

Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
Color legend for Distribution Map
Endemism: endemic to a single nation

U.S. & Canada State/Province Distribution
United States OK, TX

Range Map
No map available.


U.S. Distribution by County Help
State County Name (FIPS Code)
TX Austin (48015), Brazos (48041), Burleson (48051), Colorado (48089), Falls (48145), Fayette (48149), Fort Bend (48157), Grimes (48185), Hood (48221), Irion (48235)*, Lampasas (48281), Matagorda (48321), McLennan (48309), Milam (48331), Mills (48333), Palo Pinto (48363), Parker (48367), Robertson (48395)*, San Saba (48411), Shackelford (48417), Somervell (48425), Stephens (48429), Waller (48473), Washington (48477), Wharton (48481)
* Extirpated/possibly extirpated
U.S. Distribution by Watershed Help
Watershed Region Help Watershed Name (Watershed Code)
12 Middle Brazos-Millers (12060101), Lower Clear Fork Brazos (12060104)+, Middle Brazos-Palo Pinto (12060201)+, Middle Brazos-Lake Whitney (12060202)+, Bosque (12060203)*, North Bosque (12060204)*, Lower Brazos-Little Brazos (12070101)+, Navasota (12070103)+, Lower Brazos (12070104)+, Leon (12070201)*, Cowhouse (12070202)*, Little (12070204)+, South Concho (12090102)+*, Middle Colorado (12090106)+, San Saba (12090109)+, Buchanan-Lyndon B (12090201)+, Llano (12090204)*, Austin-Travis Lakes (12090205)*, Lower Colorado-Cummins (12090301)+, Lower Colorado (12090302)+, San Bernard (12090401)*
+ Natural heritage record(s) exist for this watershed
* Extirpated/possibly extirpated
U.S. Distribution by Watershed (based on multiple information sources) Help
Ecology & Life History
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Basic Description: A freshwater mussel with a gray-green, greenish-brown, orange-brown, to dark brown, colored shell often with greenish rays, zig-zags, or chevrons.
General Description: Ovate to long ovate, slightly compressed, males more pointed posteriorly, to at least 55 mm shell length, thin to moderately thick, subsolid to solid, disk unsculptured, beaks slightly elevated, beak cavity shallow, lateral teeth relatively short, pseudocardinal teeth triangular and compressed; external coloration gray-green, greenish-brown, orange-brown, to dark brown, often with greenish rays, zig-zags, or chevrons; nacre white (Howells et al. 1996).
Reproduction Comments: Reproductive information including glochidial hosts remains unknown.
Habitat Type: Freshwater
Non-Migrant: N
Locally Migrant: N
Long Distance Migrant: N
Riverine Habitat(s): CREEK, MEDIUM RIVER
Special Habitat Factors: Benthic
Habitat Comments: Little is known about habitat requirements for this species. Only a few specimens have been found alive or recently dead. Since 1980. It is likely these were washed or otherwise removed from their preferred microhabitat sites which remain undetermined. Texas fawnsfoot appears to prefer rivers and larger streams. Living specimens have not been documented in reservoirs suggesting intolerance of impoundment, but has also been found alive in the past in flowing rice irrigation canals. It probably prefers sand, gravel, and perhaps sandy-mud bottoms in moderate flows.
Economic Attributes Not yet assessed
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Management Summary
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Stewardship Overview: Immediate actions need to be taken if this species is to survive. These include habitat restoration and ceasing activities in waterways that adversely affect this species. Interagency cooperation is a must and, given that much of the species? current range does not fall on public lands, landowner cooperation is also a must. Stream flow obstructions and activities contributing to degradation of water quality and flow should be strictly avoided. Habitat loss around streams that will lead to erosion, siltation, turbidity, and scouring must be avoided. Restoration of habitat is encouraged. Sand and gravel operations should not be allowed at or anywhere near extant populations.

As per USFWS (2015) recommendations, work should continue with the development of ?a drought contingency plan that will facilitate the management and monitoring of mussel populations.? Protocols for survey, relocation, and monitoring should be developed to ?establish a commonality among the wide variety of methods currently being used in Texas and would establish a baseline of what kind of data needs to be collected while conducting surveys.? Continue surveys and research aimed at finding new populations, monitoring existing populations, more accurately estimating population sizes and health, and ?to identify host fish, spawning and brooding seasons, glochidia, and habitat and physiochemical parameters? (USFWS 2015).

Biological Research Needs: Virtually nothing has been documented about species biology including required or preferred habitat, glochidia, host fishes, reproductive seasons, fecundity, environmental tolerances, to name but a few. This species is very poorly known biologically.
Population/Occurrence Delineation
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Group Name: Freshwater Mussels

Use Class: Not applicable
Minimum Criteria for an Occurrence: Occurrences are based on some evidence of historical or current presence of single or multiple specimens, including live specimens or recently dead shells (i.e., soft tissue still attached and/or nacre still glossy and iridescent without signs of external weathering or staining), at a given location with potentially recurring existence. Weathered shells constitute a historic occurrence. Evidence is derived from reliable published observation or collection data; unpublished, though documented (i.e. government or agency reports, web sites, etc.) observation or collection data; or museum specimen information.
Mapping Guidance: Based on the separation distances outlined herein, for freshwater mussels in STANDING WATER (or backwater areas of flowing water such as oxbows and sloughs), all standing water bodies with either (1) greater than 2 km linear distance of unsuitable habitat between (i.e. lotic connections), or (2) more than 10 km of apparently unoccupied though suitable habitat (including lentic shoreline, linear distance across water bodies, and lentic water bodies with proper lotic connections), are considered separate element occurrences. Only the largest standing water bodies (with 20 km linear shoreline or greater) may have greater than one element occurrence within each. Multiple collection or observation locations in one lake, for example, would only constitute multiple occurrences in the largest lakes, and only then if there was some likelihood that unsurveyed areas between collections did not contain the element.

For freshwater mussels in FLOWING WATER conditions, occurrences are separated by a distance of more than 2 stream km of unsuitable habitat, or a distance of more than 10 stream km of apparently unoccupied though suitable habitat. Standing water between occurrences is considered suitable habitat when calculating separation distance for flowing water mussel species unless dispersal barriers (see Separation Barriers) are in place.

Several mussel species in North America occur in both standing and flowing water (see Specs Notes). Calculation of separation distance and determination of separation barriers for these taxa should take into account the environment in which the element was collected. Juvenile mussels do not follow this pattern and juveniles are typically missed by most standard sampling methods (Hastie and Cosgrove, 2002; Neves and Widlak, 1987), therefore juvenile movement is not considered when calculating separation distance.

Separation Barriers: Separation barriers within standing water bodies are based solely on separation distance (see Separation Distance-suitable, below). Separation barriers between standing water bodies and within flowing water systems include lack of lotic connections, natural barriers such as upland habitat, absence of appropriate species specific fish hosts, water depth greater than 10 meters (Cvancara, 1972; Moyle and Bacon, 1969) or anthropogenic barriers to water flow such as dams or other impoundments and high waterfalls.
Separation Distance for Unsuitable Habitat: 2 km
Separation Distance for Suitable Habitat: 10 km
Alternate Separation Procedure: None
Separation Justification: Adult freshwater mussels are largely sedentary spending their entire lives very near to the place where they first successfully settled (Coker et al., 1921; Watters, 1992). Strayer (1999) demonstrated in field trials that mussels in streams occur chiefly in flow refuges, or relatively stable areas that displayed little movement of particles during flood events. Flow refuges conceivably allow relatively immobile mussels to remain in the same general location throughout their entire lives. Movement occurs with the impetus of some stimulus (nearby water disturbance, physical removal from the water such as during collection, exposure conditions during low water, seasonal temperature change or associated diurnal cycles) and during spawning. Movement is confined to either vertical movement burrowing deeper into sediments though rarely completely beneath the surface, or horizontal movement in a distinct path often away from the area of stimulus. Vertical movement is generally seasonal with rapid descent into the sediment in autumn and gradual reappearance at the surface during spring (Amyot and Downing, 1991; 1997). Horizontal movement is generally on the order of a few meters at most and is associated with day length and during times of spawning (Amyot and Downing, 1997). Such locomotion plays little, if any, part in the distribution of freshwater mussels as these limited movements are not dispersal mechanisms. Dispersal patterns are largely speculative but have been attributed to stream size and surface geology (Strayer, 1983; Strayer and Ralley, 1993; van der Schalie, 1938), utilization of flow refuges during flood stages (Strayer, 1999), and patterns of host fish distribution during spawning periods (Haag and Warren, 1998; Watters, 1992). Lee and DeAngelis (1997) modeled the dispersal of freshwater into unoccupied habitats as a traveling wave front with a velocity ranging from 0.87 to 2.47 km/year (depending on mussel life span) with increase in glochidial attachment rate to fish having no effect on wave velocity.

Nearly all mussels require a host or hosts during the parasitic larval portion of their life cycle. Hosts are usually fish, but a few exceptional species utilize amphibians as hosts (Van Snik Gray et al., 2002; Howard, 1915) or may metamorphose without a host (Allen, 1924; Barfield et al., 1998; Lefevre and Curtis, 1911; 1912). Haag and Warren (1998) found that densities of host generalist mussels (using a variety of hosts from many different families) and displaying host specialists (using a small number of hosts usually in the same family but mussel females have behavioral modifications to attract hosts to the gravid female) were independent of the densities of their hosts. Densities of non-displaying host specialist mussels (using a small number of hosts usually in the same family but without host-attracting behavior) were correlated positively with densities of their hosts. Upstream dispersal of host fish for non-displaying host specialist mussels could, theoretically, transport mussel larvae (glochidia) over long distances through unsuitable habitat, but it is unlikely that this occurs very often. D. Strayer (personal communication) suggested a distance of at least 10 km, but a greater distance between occurrences may be necessary to constitute genetic separation of populations. As such, separation distance is based on a set, though arbitrary, distance between two known points of occurrence.

Date: 18Oct2004
Author: Cordeiro, J.
Notes: Contact Jay Cordeiro (jay_cordeiro@natureserve.org) for a complete list of freshwater mussel taxa sorted by flow regime.
Population/Occurrence Viability
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U.S. Invasive Species Impact Rank (I-Rank) Not yet assessed
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Authors/Contributors
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NatureServe Conservation Status Factors Edition Date: 28Nov2018
NatureServe Conservation Status Factors Author: Smith-Patten, B.D. (2018, in part); Cordeiro, J. (2007); Howells, R. G. (1998)
Management Information Edition Date: 30Nov2018
Management Information Edition Author: Smith-Patten, B. D. (in part)
Element Ecology & Life History Edition Date: 06Mar2007
Element Ecology & Life History Author(s): Cordeiro, J.

Zoological data developed by NatureServe and its network of natural heritage programs (see Local Programs) and other contributors and cooperators (see Sources).

References
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  • Agrilife Today. 2011. Researchers discover freshwater mussel species thought to be extinct. Agrilife Today, August 15, 2011.

  • Branson, B.A. 1984. The mussels (Unionacea: Bivalvia) of Oklahoma- Part 3: Lampsilini. Proceedings of the Oklahoma Academy of Science, 64: 20-36.

  • Burch, J.B. 1975a. Freshwater unionacean clams (Mollusca: Pelecypoda) of North America. Malacological Publications: Hamburg, Michigan. 204 pp.

  • Burlakova, L.E., A.Y. Karatayev, V.A. Karatayev, M.E. May, D.L. Bennett, and M.J. Cook. 2011. Endemic species: contribution to community uniqueness, effect of habitat alteration, and conservation priorities. Biological Conservation 144(1):155-165.

  • Howard, A.D. 1915. Some exceptional cases of breeding among the Unionidae. The Nautilus 29:4-11.

  • Howells, R.G. 1996a. Distributional surveys of freshwater mussels bivalves in Texas: progress report for 1994. Texas Parks and Wildlife Department, Management Data Series 120, Austin, Texas.

  • Howells, R.G. 1996b. Distributional surveys of freshwater mussels bivalves in Texas: progress report for 1995. Texas Parks and Wildlife Department, Management Data Series 125: Austin, Texas.

  • Howells, R.G. 1997c. Distributional surveys of freshwater mussels bivalves in Texas: progress report for 1996. Texas Parks and Wildlife Department, Management Data Series 144: Austin, Texas.

  • Howells, R.G., C.M. Mather, and J.A.M. Bergmann. 1997. Conservation status of selected freshwater mussels in Texas. Pages 117-126 in K.S. Cummings, A.C. Buchanan, C.A. Mayer, and T.J. Naimo (eds.). Conservation and Management of Freshwater Mussels II: Initiatives for the Future, Proceedings of a UMRCC Symposium, 16-18 October, 1995, St. Louis, Missouri. Upper Mississippi River Conservation Committee, Rock Island, Illinois.

  • Howells, R.G., R.W. Neck, and H.D. Murray. 1996. Freshwater Mussels of Texas. Texas Parks and Wildlife Press: Austin, Texas. 218 pp.

  • Johnson, R.I. 1999. Unionidae of the Rio Grande (Rio Bravo del Norte) system of Texas and Mexico. Occasional Papers on Mollusks, 6(77): 1-65.

  • Lefevre, G. and W.T. Curtis. 1912. Studies on the reproduction and artificial propogation of fresh-water mussels. Bulletin of the Bureau of Fisheries 30:102-201.

  • Moyle, P. and J. Bacon. 1969. Distribution and abundance of molluscs in a fresh water environment. Journal of the Minnesota Academy of Science 35(2/3):82-85.

  • Reimer, M.M. and L.A. Linam. 2005. Texas mussel watch, a citizen based volunteer monitoring program. Ellipsaria, 7(3): 5-6.

  • Simpson, C.T. 1914. A Descriptive Catalogue of the Naiades or Pearly Fresh-water Mussels. Bryant Walker: Detroit, Michigan. 1540 pp.

  • Strayer, D. 1983. The effects of surface geology and stream size on freshwater mussel (Bivalvia, Unionidae) distribution in southeastern Michigan, U.S.A. Freshwater Biology 13:253-264.

  • Strayer, D.L. 1999a. Use of flow refuges by unionid mussels in rivers. Journal of the North American Benthological Society 18(4):468-476.

  • Strayer, D.L. and J. Ralley. 1993. Microhabitat use by an assemblage of stream-dwelling unionaceans (Bivalvia) including two rare species of Alasmidonta. Journal of the North American Benthological Society 12(3):247-258.

  • 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.

  • U.S. Fish and Wildlife Service (USFWS). 2013. Review of Native Species That are Candidates for Listing as Endangered or Threatened; Annual Notice of Findings on Resubmitted Petitions; Annual Description of Progress on Listing Actions. Federal Register 78(226):70104-70162.

  • U.S. Fish and Wildlife Service (USFWS). 2015. U.S. Fish and Wildlife Service species assessment and listing priority assignment form: Truncilla macrodon. U.S. Fish and Wildlife Service.

  • U.S. Fish and Wildlife Service (USFWS). 2016. Review of Native Species that are Candidates for Listing as Endangered or Threatened; Annual Notification of Findings on Resubmitted Petitions; Annual Description of Progress on Listing Actions. Federal Register 81(232): 87246-87272.

  • Van der Schalie, H. 1938a. The naiad fauna of the Huron River in southeastern Michigan. Miscellaneous Publication of the Museum of Zoology, University of Michigan 40:7-78.

  • Watters, G.T. 1992a. Unionids, fishes, and the species-area curve. Journal of Biogeography 19:481-490.

  • Williams, J. D., A. E. Bogan, R. S. Butler, K. S. Cummings, J. T. Garner, J. L. Harris, N. A. Johnson, and G. T. Watters. 2017. A revised list of the freshwater mussels (Mollusca: Bivalvia: Unionida) of the United States and Canada. Freshwater Mollusk Biology and Conservation 20:33-58.

  • Williams, J.D., M.L. Warren, Jr., K.S. Cummings, J.L. Harris, and R.J. Neves. 1993b. Conservation status of freshwater mussels of the United States and Canada. Fisheries 18(9): 6-22.

References for Watershed Distribution Map
  • Strecker, J.K. 1931. The naiades or pearly fresh-water mussels of Texas. Baylor University Museum Special Bulletin, 2: 1-71.

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