Phylum: Mollusca
Class: Bivalvia
Order: Actinodontida (Douvillé, 1912)
Cincinnatian Families: Cycloconchidae

Geologic Range
Early Ordovician – Late Cretaceous

Common Paleoecology
Actinodontida is an extinct order of facultatively mobile infaunal suspension feeders

Characteristics of the Order

  • Equivalved
  • Few teeth, radial and divergent from umbo
  • Lateral teeth originate below beak
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Treatise on Invertebrate Paleontology, Part N, Mollusca 6 (1 of 3) (1969):

    • Equivalve, with closed margins and, where preserved, prismatonacreous shells; ligament amphidetic or opisthodetic, external and parivincular; dentition generally consisting of few teeth more or less radial and divergent from umbonal region, striated in some genera, rarely becoming taxodont in few genera (uncertain Unionoida); where lateral teeth occur, they originate below beaks and are not separated from cardinals by edentulous interval, as in Heterodonta. [These forms include the actinodonts (earliest known Bivalvia), Trigonioida and Unionoida. They lead in various lines to the Pteriomorphia, Heterodonta, and possibly to the Mytiloida early in the Paleozoic.]

Actinodontoida was named by Douville (1912), was assigned to Palaeoheterodonta by Cope (1997), but was synonymized subjectively with Unionoida by Nevesskaja (2009); it was corrected as Actinodontida by Carter et al. (2011).

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