Placenticeratidae
Encyclopedia
The Placenticeratidae is a family of mostly Late Cretaceous
ammonites (cephalopod
order Ammonitida
) included in the superfamily Hoplitaceae
, derived from the Engonoceratidae
by an increase in suture complexity.
Placeticeratids are characterized by rather involute compressed shells of moderate to large size with narrow flat or grooved venters (outer rims), at least on early whorls. Most are rather smooth or weakly ornamented except for a few later forms in which the outer whorls are strongly tuberculate. The suture has numerous, including auxiliary and adventive, elements. Saddles and lobes are typically deep, narrow necked, and raggedly embayed.
The Placenticeratidae had their beginning in the Late Albian stage at the end of the Early Cretaceous, starting with Hypengonoceras. The type genus, Placenticeras
appears later and is knows from the upper Santonian
to the lower Campanian
of the Upper Cretaceous. The family has the longest duration of the Hoplitaceae, extending will into the Maastrichtian
, the final stage of the Cretaceous period with the genus Hoplitoplanticeras.
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
ammonites (cephalopod
Cephalopod
A cephalopod is any member of the molluscan class Cephalopoda . These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles modified from the primitive molluscan foot...
order Ammonitida
Ammonitida
The Ammonitida is an order of more highly evolved ammonoid cephalopods from the Jurassic and Cretaceous time periods, commonly with intricate ammonitic sutures....
) included in the superfamily Hoplitaceae
Hoplitaceae
Hoplitaceae is a superfamily of mostly Upper Cretaceous ammonites comprising families united by a similar suture pattern with multiple similar elements that tend to decrease in size going toward the umbilicus, at the inner edge of any whorl, and which are typically in a straight line...
, derived from the Engonoceratidae
Engonoceratidae
Engonoceratidae is a family of typically compressed, more or less flat sided and involute ammonites from the mid Cretaceous belonging to the Hoplitaceae. shells have flat sided outer rims , at least in some stage. Single or branching irregular ribs and variably placed tubercles may occur...
by an increase in suture complexity.
Placeticeratids are characterized by rather involute compressed shells of moderate to large size with narrow flat or grooved venters (outer rims), at least on early whorls. Most are rather smooth or weakly ornamented except for a few later forms in which the outer whorls are strongly tuberculate. The suture has numerous, including auxiliary and adventive, elements. Saddles and lobes are typically deep, narrow necked, and raggedly embayed.
The Placenticeratidae had their beginning in the Late Albian stage at the end of the Early Cretaceous, starting with Hypengonoceras. The type genus, Placenticeras
Placenticeras
Placenticeras is an ammonite genus from the Late Cretaceous. Its fossils have been found in Asia, Europe, North and South America.-Taxonomy:...
appears later and is knows from the upper Santonian
Santonian
The Santonian is an age in the geologic timescale or a chronostratigraphic stage. It is a subdivision of the Late Cretaceous epoch or Upper Cretaceous series. It spans the time between 85.8 ± 0.7 mya and 83.5 ± 0.7 mya...
to the lower Campanian
Campanian
The Campanian is, in the ICS' geologic timescale, the fifth of six ages of the Late Cretaceous epoch . The Campanian spans the time from 83.5 ± 0.7 Ma to 70.6 ± 0.6 Ma ...
of the Upper Cretaceous. The family has the longest duration of the Hoplitaceae, extending will into the Maastrichtian
Maastrichtian
The Maastrichtian is, in the ICS' geologic timescale, the latest age or upper stage of the Late Cretaceous epoch or Upper Cretaceous series, the Cretaceous period or system, and of the Mesozoic era or erathem. It spanned from 70.6 ± 0.6 Ma to 65.5 ± 0.3 Ma...
, the final stage of the Cretaceous period with the genus Hoplitoplanticeras.