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Acrioceras
Classification
Phylum:
Mollusca
Class:
Cephalopoda
Order:
Ammonitida
Superfamily:
Ancylocerataceae
Family:
Ancyloceratidae
Formal Genus Name and Reference:
Acrioceras HYATT, 1900, p. 587
Type Species:
Ancyloceras tabarelli ASTIER, 1851, p. 453 (19), OD
Images
(Click to enlarge in a new window)
F IG . 173,1. *A. (A.) tabarelli (ASTIER ), Lower Barremian, France; ×1 (Sarasin & Schöndelmayer, 1902).
Synonyms
Mesocrioceras
Geographic Distribution
western and central Europe, Caucasus, Madagascar, Japan, California
Age Range
Beginning Stage in Treatise Usage:
Lower Cretaceous (Upper Hauterivian)
Beginning International Stage:
Hauterivian
Fraction Up In Beginning Stage:
45
Beginning Date:
129.86
Ending Stage in Treatise Usage:
Lower Cretaceous (Lower Aptian)
Ending International Stage:
Aptian
Fraction Up In Ending Stage:
33
Ending Date:
118.69
Description
Small, spire of 1 or 2 loosely coiled whorls followed by short or long, straight or curved shaft, terminal hook, and short or long final shaft, ribs generally fine and untuberculate, but sometimes major ribs enlarged and carrying 1 to 3 tubercles, ribs single on spire and shaft but may branch from umbilical tubercles on hook and final shaft, dorsum tending to become flat and dorsolateral margin to become angular on shaft and hook
References
Museum or Author Information
Classification
Phylum:
Mollusca
Class:
Cephalopoda
Order:
Ammonitida
Superfamily:
Ancylocerataceae
Family:
Ancyloceratidae
Formal Genus Name and Reference:
Acrioceras HYATT, 1900, p. 587
Type Species:
Ancyloceras tabarelli ASTIER, 1851, p. 453 (19), OD
Images
(Click to enlarge in a new window)
F IG . 173,1. *A. (A.) tabarelli (ASTIER ), Lower Barremian, France; ×1 (Sarasin & Schöndelmayer, 1902).
Synonyms
Mesocrioceras
Geographic Distribution
western and central Europe, Caucasus, Madagascar, Japan, California
Age Range
Beginning Stage in Treatise Usage:
Lower Cretaceous (Upper Hauterivian)
Beginning International Stage:
Hauterivian
Fraction Up In Beginning Stage:
45
Beginning Date:
129.86
Ending Stage in Treatise Usage:
Lower Cretaceous (Lower Aptian)
Ending International Stage:
Aptian
Fraction Up In Ending Stage:
33
Ending Date:
118.69
Description
Small, spire of 1 or 2 loosely coiled whorls followed by short or long, straight or curved shaft, terminal hook, and short or long final shaft, ribs generally fine and untuberculate, but sometimes major ribs enlarged and carrying 1 to 3 tubercles, ribs single on spire and shaft but may branch from umbilical tubercles on hook and final shaft, dorsum tending to become flat and dorsolateral margin to become angular on shaft and hook