The shellfish go by a variety of names, such as fat mucket, heel splitter and false spike. They are more common in the Colorado River basin that bisects central Texas than anywhere else in the state.
Because they filter the water they ingest, they retain contaminants in the water and pass them on to the river animals and insects that feed on them.
Endangered status could mean state river authorities may have to recalculate how much water can be allocated to industries, farms and communities in the Colorado basin and still leave enough to sustain the mussels.