Kosmoceratidae is an extinct ammonite family from the

Callovian In the geologic timescale, the Callovian is an age and stage in the Middle Jurassic, lasting between 166.1 ± 4.0 Ma (million years ago) and 163.5 ± 4.0 Ma. It is the last stage of the Middle Jurassic, following the Bathonian and preceding the ...

(Middle Jurassic) to Early

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...

. Kosmoceratidae are probably the most polymorphic groups of Jurassic ammonites. These ammonoids have a more or less tabulate venter, with lateral or ventrolateral tubercles. The

aptychus An aptychus is a type of marine fossil. It is a hard anatomical structure, a sort of curved shelly plate, now understood to be part of the body of an ammonite. Paired aptychi have, on rare occasions, been found at or within the aperture of ammo ...

is double valved with a concentrically ribbed surface.Treatise on invertebrate paleontology. Part F : America / edited by Raymond C. Moore. -- University of Kansas Press, 1956

References

* Philippe Courville, Catherine Crônier
Diversity or Disparity in the Jurassic (Upper Callovian) genus Kosmoceras (ammonitina): A Morphometric Approach

External links

Jurassic ammonites Callovian first appearances Middle Jurassic extinctions Ammonitida families Stephanoceratoidea {{ammonitina-stub