Ancistroceras
Ancistroceras is one of the two ancestral lituitids from the late Early Ordovician (Arenigian). The other being Holmiceras. The shell is weakly annulate, starts off with 1.5 to 2 contiguous or slightly separated whorls followed by a rapidly expanding orthocone with an apical angle of about 30 deg. Growth lines are sinuous, show a pronounced hyponomic sinus in the coiled juvenile portion at the apex but almost none at the mature aperture of the orthcone. Holmiceras is similar except that its whorls are more loosely coiled and it is known only from the Arenigian whereas Ancistroceras ranges through most of the Middle Ordovician.
primaryTopic
Ancistroceras
Ancistroceras is one of the two ancestral lituitids from the late Early Ordovician (Arenigian). The other being Holmiceras. The shell is weakly annulate, starts off with 1.5 to 2 contiguous or slightly separated whorls followed by a rapidly expanding orthocone with an apical angle of about 30 deg. Growth lines are sinuous, show a pronounced hyponomic sinus in the coiled juvenile portion at the apex but almost none at the mature aperture of the orthcone. Holmiceras is similar except that its whorls are more loosely coiled and it is known only from the Arenigian whereas Ancistroceras ranges through most of the Middle Ordovician.
has abstract
Ancistroceras is one of the tw ...... nament and a complex aperture.
@en
class
family
order (taxonomy)
phylum
Wikipage page ID
26,553,507
Wikipage revision ID
726,045,428
fossil range
late L Ord - M Ord.
genus
comment
Ancistroceras is one of the tw ...... most of the Middle Ordovician.
@en
label
Ancistroceras
@en
wasDerivedFrom
isPrimaryTopicOf
name
Ancistroceras
@en