''Aulacostephanus'' is an extinct ammonoid cephalopod genus from the Upper Jurassic Tithonian belonging to the perisphinctoidean family Aulacostephanidae. ''Aulacostephanus'' produced a discoidal, strongly ribbed, evolute shell of moderate size, reaching diameters of 16 cm (~6.5in.), or so. Ribs diverge in pairs and threes from nodes on the umbilical shoulder and extend radially outward onto the ventro-lateral shoulder, but do not cross the venter, (the outer rim). Sides are flat, the venter steeply rounded, with an open bend or median groove running down the middle. Clutches of eggs attributed to this genus have been discovered in the

Kimmeridge Clay The Kimmeridge Clay is a sedimentary deposit of fossiliferous marine clay which is of Late Jurassic to lowermost Cretaceous age and occurs in southern and eastern England and in the North Sea. This rock formation is the major source rock for Nor ...

Distribution

Jurassic sediments of Germany, the Russian Federation, Switzerland and the United Kingdom

References

;Notes ;Bibliography *

Treatise on Invertebrate Paleontology The ''Treatise on Invertebrate Paleontology'' (or ''TIP'') published by the Geological Society of America and the University of Kansas Press, is a definitive multi-authored work of some 50 volumes, written by more than 300 paleontologists, and co ...

, Part L, Ammonoidea. R.C. Moore (Ed). Geological Society of America, 1957. Ammonitida genera Perisphinctoidea Jurassic ammonites Ammonites of Europe Tithonian life Aulacostephanidae {{ammonitina-stub