title: Anomphalidae
text: # Anomphalidae
  
  The Anomphalidae is an extinct family of fossil sea snails, marine gastropod mollusks. These are archaeogastropods which are included in the suborder Trochina. The Anomphalidae lived during the Paleozoic, from the Silurian to the Middle Permian. According to some authorities these snails belong instead to the Euomphalacea.
  
  ## Morphologic diagnosis
  
  Shells of the Anomphalidae are rounded, almost discoidal, low-spired trochospiral inform, possibly with a globular body whorl. The aperture is oval, without exhalent slit or crease. The umbilicus is narrow, open or closed. The inner shell layer is seemingly nacreous. The shell surface is generally smooth, ornamentation consisting of fine transverse lyrae or growth lines parallel to the aperture lip.
  
  The Anomphalidae differ from the Euomphalcea to which they have been reassigned in being more trochoidal, in lacking the angulation on the upper whorl surface characteristic of Euomphalacea, and in having the inner shell layer seemingly nacreous. (The inner shell layers of the Euomphalacea may be of laminar aragonite, but are never nacreous.) The Anomphalidea differ from the Pleurotomariacea in lacking the often deep slit or selenizone, which is characteristic of that taxon.
  
  ## Taxonomy
  
  J Brooks Knight, et al, in the Treatise, 1960, assigned 10 genera to the Annomphalidae. They are
  
      Anomphalus Meek and Worthen 1866, the type genus
      Cycloscena Fletcher 1958
      Eiselia Dietz 1911
      Isonema Meek and Worthen 1866
      Pycnomphalus Lindström 1884
      Turbocheilus Perner 1907
      Sosiolytes Gemmellaro 1889
      Straparella Fischer 1885
      Turbinilopsis de Koninck 1881
      Tychonia de Koninck 1881
  
  At present the Anompalideae has been expanded to include 17 genera in two subfamilies established by Peel, 1984.
  
  Added to Anomphalus, Cycloscena, Eiselia, and Isonema in the Anomphalinae are:
  
  Antirotiela Cossmann 1918, given in the Treatise as a synonym for Anomphalus
  
      Frydacosta Cook and Nützel 2005
      Delphinuella Heidelberger 2001
      Givediscus Heidelberger 2001
      Littorella Heidelberger 2001
      Nodinella Heidelberger 2001
  
  Contained within the Pycnomphalinae in addition to Pycnomphalus, Turbocheilus, Sosiolites, Strapariella, and Tychonia:
  
      Pycnotrochus Perner 1903
      Turbinilopsis de Koninck 1881
  
  Pycnotrochus, from the Upper Silurian of Europe, was removed from the Sinuopeidae (Pleurotomariacea); the lip has a sinus more characteristic of the original family. Turbinopsis, from the Lower Devonian of North America, was removed from the Palaeotrochidae (Palaeotrochacea); has a spiral chord not found on typical Anomphalidae and an aperture with a thicker, wider lip, also atypical.
  
  Bouchet & Rocroi, 2005 simply included the Anomphalidae in "basal taxa that are certainly Gastropoda".
  
  