Rhynchonellata - Orthida - Dalmanellidae
Alternative spelling: Arcualla
Parent taxon: Isorthis according to A. Williams et al. 2000
See also Sepkoski 2002
Sister taxa: Isorthis (Isorthis), Isorthis (Ovalella), Isorthis (Protocortezorthis), Isorthis alpha, Isorthis bailyi, Isorthis crassa, Isorthis estona, Isorthis festiva, Isorthis loveni, Isorthis mediocra, Isorthis parvulus, Isorthis pygmaea, Isorthis slitensis
Subtaxa: Isorthis (Arcualla) arcuaria Isorthis (Arcualla) boreaina Isorthis (Arcualla) microscapha
Type: Orthis (Dalmanella) arcuaria
Ecology: stationary epifaunal suspension feeder
Distribution:
• Devonian of Australia (1 collection), the Czech Republic (3)
• Whitwellian of Canada (3: Northwest Territories)
• Silurian of Canada (2: Northwest Territories, Ontario), the Czech Republic (6), United States (21: Indiana, Oklahoma), Venezuela (2)
Total: 38 collections including 42 occurrences