This species was originally described as Unio pullus (Conrad 1838). The Savannah River population was once described as a separate species, Carunculina patrickae (Bates 1966), due to different shell morphology.

Carunculina patrickae was synonymized with C. pullus by Johnson (1970), and is now known as Toxolasma pullus.

A list of synonyms for this species can be found on The MUSSEL project web site (Graf and Cummings 2011).

Toxolasma pullus has been assessed as Vulnerable as it is restricted to approximately seven highly fragmented populations, of which just three are reproducing, with an extent of occurrence of around 20,000 km². It faces many different threats throughout its distribution, ranging from water loss and impoundment to predation and motor vehicle impacts. Although these are in the main local threats, each one has the potential to affect an entire population, with little chance of recovery due to the fragmented distribution of T. pullus.

Despite the possibility of new populations being discovered, it is recommended that T. pullus be listed as Vulnerable due to a total extent of occurrence of less than 20,000 km²; ongoing declines in density and number of populations, and of habitat quality; and a total number of less than ten locations.

This species is restricted to three states in the US: South Carolina, North Carolina, and Georgia.

In South Carolina, it is known from the Savannah, Cooper-Santee, and Pee River basins (Bogan et al. 2008). In Georgia, it is found in the Savannah, Ogeechee, and Altamaha River basins (the southern-most extent of its range) (Wisniewski 2008). Although originally described from the Wateree River in South Carolina, an extensive survey in 2004 failed to find any individuals (J. Alderman pers. comm. cited in Price 2005). In North Carolina, it is believed to be extirpated from Lake Waccamaw (Bogan and Alderman 2004).

This species is thought to have an extent of occurrence of around 20,000 km²; throughout its range it is highly fragmented (NatureServe 2009).

This species used to extend from the Altamaha River basin in Georgia to the Neuse River basin in North Carolina (Bogan and Alderman 2004). It is still thought to be fairly abundant, but only in a very small number of locations (NatureServe 2009), and has exhibited recent and continuing declines in both density and the number of populations. Despite this, new populations continue to be discovered, suggesting that understanding of this species is incomplete (L. Zimmerman pers. comm. 2009).

A survey by Alderman (1994) found just seven extant populations: Ohoopee River (Georgia); Savannah River (South Carolina, Georgia); Richardson Creek (Rocky River basin), Densons Creek and Little River (Pee Dee River basin), Lake Waccamaw, and University Lake (Haw River basin) in North Carolina. Recent surveys have also confirmed its presence in the Altamaha River in Georgia (Wiskiewski 2008). Only three of the populations listed by Alderman (1994) have shown recent evidence of reproduction (NatureServe 2009).

It is considered extirpated from several of its former locations, including: the Neuse and Waccamaw River basins (North Carolina) (Adams et al. 1990); Columbus County, North Carolina. (NatureServe 2009); the Wateree River, South Carolina. Only seven individuals were recently found in Lake Marion, S.C., and three in the Ogeechee River in Georgia (Price 2005).

The most stable populations appear to be at University Lake, North Carolina, an artificially-created lake which covers an area of 86 ha (0.86 square km) and in the Savannah River (A. Bogan pers. comm. 2010). However, this population has also undergone recent declines (Price 2005).

This species inhabits lotic streams and ponds, where it prefers mud or sand near the banks (Johnson 1970). It is rarely found in deeper water, but usually in small colonies in less than six inches of water.

Little is known about the life history of this species (Adams et al. 1990). Studies in the one of the only known stable populations, at University Lake in North Carolina, found that the fish-host species is the hybrid bluegill (Lepomis macrochirus x L. cyanellus). Other Lepomis spp. are also considered likely hosts due to associations with congeneric species (Hanlon and Levine 2004). Also at the same location, the sex ratio was found to be not significantly different from 1:1, although without a thorough sub-sample survey the authors caution against generalising for all populations (Hanlon and Levine 2004). Age ranged from three to nine years (mean: 5.2 for males, 4.7 for females), with most individuals found (85%) aged four to six years (Hanlon and Levine 2004).

Being a shallow-water specialist with many small, fragmented populations, this species is highly susceptible to any form of water loss (for example from drainage or drought). It is also vulnerable to the effects of off-road vehicles, the suspected cause of declines in the Ohoopee River, Georgia (Price 2005, Wisniewski 2008). The species is also susceptible to pollution, and its dispersal is hindered by artificial structures such as dams.

Dredging work and modification of the Savannah River by the US Army Corps of Engineers has negatively impacted one of the largest populations of this species (Alderman 1994).

Anecdotal information suggests that entire populations may be at risk from episodes of water loss; for example the mass stranding that occurred at Lake Marion in January 2005, resulting in the loss of many individuals (T. Savidge pers. comm. cited in Price 2005).

This species has a fast life-history relative to other species of freshwater mussel (Hanlon and Levine 2004) which should be taken into account when considering the vulnerability of the University Lake population to predation. However the threat from predation by muskrats, for example, increases when water levels are low, with large or mature individuals most likely to be taken (Hanlon and Levine 2004). Females in particular are vulnerable due to conspicuous reproductive behaviour (Smith et al. 2001).

Introduced Flathead Catfish (Pylodictis olivaris) are considered a potential threat due to direct consumption of mussels and indirect predation of their host fish species (Wisniewski 2008).

Excess sedimentation due to inadequate riparian buffer zones covers suitable habitat and could potentially suffocate mussels (Wisniewski 2008).

This species has been given a NatureServe Global Heritage Status Rank of G2 (Imperiled), a US national status of N2 (Imperilled) and was assigned an American Fisheries Society Status of Threatened. It is a Federal species of concern, and is listed as Endangered in the states of South Carolina (Bogan and Alderman 2004) and North Carolina (Hanlon and Levine 2004), and Threatened in Georgia (Wisniewski 2008). The US Fish and Wildlife Service (USFWS) was considering listing the species as Endangered nationally (Price 2005). However, due to incomplete knowledge about the number of viable populations such a listing is no longer being pursued (L. Zimmerman pers. comm. 2009).

The species occurs in the Altamaha River in the Griffin Ridge Wildlife Management Area in Georgia. However, this does not eliminate habitat degradation as a possible threat because disturbances may occur upstream (Wisniewski 2008).

Proposed conservation measures include: reintroduction of artificially propagated individuals into suitable locations within the species' historic range; management of water levels in small ponds and lakes to avoid high levels of predation (Hanlon and Levine 2004); minimizing disturbances due to all-terrain vehicles to prevent individuals from being crushed, as well as minimizing unnecessary erosion along waterways (Wisniewski 2008).