Bivalvia - Cardiida - Veneridae
Alternative spelling: Pachydesma
Synonym: Trigonella Conrad 1837 [replaced name]
Parent taxon: Tivela according to T. S. Oldroyd 1925
See also Clark 1915, Cox et al. 1969, Sepkoski 2002 and Wagner and Schilling 1923
Sister taxa: Tivela (Comus), Tivela (Planitivela), Tivela (Tivela), Tivela cliffensis, Tivela kelloggensis, Tivela merriami, Tivela packardi, Tivela trigonalis, Tivela vaquerosensis, Tivela weaveri
Subtaxa: Pachydesma sulcataria Tivela (Pachydesma) diabloensis Tivela (Pachydesma) gabbi Tivela (Pachydesma) inezana Tivela (Pachydesma) stultorum
Ecology: facultatively mobile infaunal suspension feeder
Distribution:
• Quaternary of Mexico (5 collections), United States (30: California)
• Pliocene to Pleistocene of United States (1: California)
• Pliocene of Mexico (1), United States (10: California)
• Miocene of United States (24: California)
• Oligocene of United States (1: California)
• Eocene of Canada (1: British Columbia), United States (7: California, Oregon, Washington)
Total: 80 collections including 81 occurrences