Peltoceras
Encyclopedia
Peltoceras is an extinct ammonite
genus from the aspidoceratid
subfamily Peltoceratinae
that lived during the later part of the Middle Jurassic (U Callovian
).
The shell of Peltoceras is evolute with whorls hardly embracing, so that all whorls are mostly exposed. The outer rim, which is known as the venter, aligning with the lower part or belly of the animal, is nearly flat. Inner whorls have strong ribs that bifurcate and trifurcate on the ventral margin. The outer whorls have large simple ribs and two rows of massive lateral tubercles, the outer row developing first.
Ammonitida
The Ammonitida is an order of more highly evolved ammonoid cephalopods from the Jurassic and Cretaceous time periods, commonly with intricate ammonitic sutures....
genus from the aspidoceratid
Aspidoceratidae
The Aspidoceratidae comprise a family of middle and upper Jurassic ammonites that make up part of the superfamily Perisphinctaceae, characterized by evolute shells, commonly stocky, that tend to develop tubercles....
subfamily Peltoceratinae
Peltoceratinae
The Peltoceratinae comprise a subfamily in the Aspidoceratidae, .Genera in the Peltoceratinae have sharply ribbed inner whorls and outer whorls that bear spines or tubercles, or have coarse simple ribs...
that lived during the later part of the Middle Jurassic (U Callovian
Callovian
In the geologic timescale, the Callovian is an age or stage in the Middle Jurassic, lasting between 164.7 ± 4.0 Ma and 161.2 ± 4.0 Ma. It is the last stage of the Middle Jurassic, following the Bathonian and preceding the Oxfordian....
).
The shell of Peltoceras is evolute with whorls hardly embracing, so that all whorls are mostly exposed. The outer rim, which is known as the venter, aligning with the lower part or belly of the animal, is nearly flat. Inner whorls have strong ribs that bifurcate and trifurcate on the ventral margin. The outer whorls have large simple ribs and two rows of massive lateral tubercles, the outer row developing first.