Distichoceras
Encyclopedia
Distichoceras is a member of the Haploceratacean
family, Oppeliidae
, and type genus for the subfamily Distichoceratinae, found in upper Middle
and lower Upper Jurassic sediments in Europe, Algeria, India, and Madagascar. The shell is essentially evolute and compressed with the outer flanks converging on a narrow, keeled venter; inner flanks which may be feebly ribbed, are separated from outer by a shallow spiral groove or band. Ribs on outer flanks end on or are looped to tall clavi (elongate tubercles or nodes) that line the venter, standing above the keel.
Haplocerataceae
Haplocerataceae is a superfamily of ammonoid cephalopods belonging to the Ammonitida that unites three families, the Strigoceratidae, Oppeliidae, and Haploceratidae, listed below....
family, Oppeliidae
Oppeliidae
Oppeliidae are compressed to oxyconic, sculptured Haplocerataceae, either unkeeled, unicarinate, bicarinate, or tricarinate; with sutures in great variety, but ribbing usually more or less falcoid or falcate...
, and type genus for the subfamily Distichoceratinae, found in upper Middle
Middle Jurassic
The Middle Jurassic is the second epoch of the Jurassic Period. It lasted from 176-161 million years ago. In European lithostratigraphy, rocks of this Middle Jurassic age are called the Dogger....
and lower Upper Jurassic sediments in Europe, Algeria, India, and Madagascar. The shell is essentially evolute and compressed with the outer flanks converging on a narrow, keeled venter; inner flanks which may be feebly ribbed, are separated from outer by a shallow spiral groove or band. Ribs on outer flanks end on or are looped to tall clavi (elongate tubercles or nodes) that line the venter, standing above the keel.