Belemnitina is a suborder of

belemnite Belemnitida (or the belemnite) is an extinct order of squid-like cephalopods that existed from the Late Triassic to Late Cretaceous. Unlike squid, belemnites had an internal skeleton that made up the cone. The parts are, from the arms-most ...

s, an extinct group of

cephalopod A cephalopod is any member of the molluscan class Cephalopoda (Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral body symmetry, a prominent head ...

s. They have been identified as the oldest of all the belemnites and are likely the stockgroup for them. They were extant from the early

Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The J ...

to the 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 th ...

. Their geographic distribution was mostly limited to Europe, although specimens have been described in Japan suggesting they may have been more widespread than previously thought.

Morphology

They have a broad, rounded pro-ostracum (the section of the guard (the hard internal skeleton commonly fossilised) closest to the head of the living animal). This characteristically lacks longitudinal alveolar canals and the associated splitting surfaces or open fissures. Commonly there are one or more longitudinal furrows in the apical region of the guard, similar furrows may be found in the alveolar region, these would not be accompanied by splitting surfaces or open fissures.

Distribution

Based on current evidence it appears that the Belemnitina were mostly restricted to Europe prior to the

Toarcian The Toarcian is, in the ICS' geologic timescale, an age and stage in the Early or Lower Jurassic. It spans the time between 182.7 Ma (million years ago) and 174.1 Ma. It follows the Pliensbachian and is followed by the Aalenian. The Toarcian ...

(late-early Jurassic), probably in small shelf seas until the

Pliensbachian The Pliensbachian is an age (geology), age of the geologic timescale and stage (stratigraphy), stage in the stratigraphic column. It is part of the Early Jurassic, Early or Lower Jurassic epoch (geology), Epoch or series (stratigraphy), Series an ...

(middle-early Jurassic). After the middle Jurassic they appear to have spread but still remained primarily in Europe. They gradually retreated during the Jurassic, becoming extinct in the Mediterranean area in the Oxfordian (late Jurassic) times. The last remaining members of the Belemnitina disappear from North-western Europe at the

Berremian The Barremian is an age in the geologic timescale (or a chronostratigraphic stage) between 129.4 ± 1.5 Ma (million years ago) and 121.4 ± 1.0 Ma). It is a subdivision of the Early Cretaceous Epoch (or Lower Cretaceous Series). It is precede ...

Aptian The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous Epoch or Series and encompasses the time from 121.4 ± 1.0 Ma to 113.0 ± 1.0 Ma (million years ago), a ...

boundary (early Cretaceous).

Stratigraphic range

Belemnitina first appear in the fossil record in the Hettangian (early Jurassic). Two genera, ''

Schwegleria ''Schwegleria'' is a genus of belemnite, an extinct group of cephalopods. See also * Belemnite Belemnitida (or the belemnite) is an extinct order of squid-like cephalopods that existed from the Late Triassic to Late Cretaceous. Unlike ...

'' and aff. '' Subhastites'' are found in Hettangian sediments from Belgium, southwest Germany and northern Ireland. They are the oldest belemnites thus far found and have been suggested as a stockgroup for all belemnites. Belemnitina have also been found in Hettangian deposits in Japan, which implies an origin for this sub-group before the Jurassic. This fits with the evidence from other groups such as the

Belemnitida Belemnitida (or the belemnite) is an extinct order of squid-like cephalopods that existed from the Late Triassic to Late Cretaceous. Unlike squid, belemnites had an internal skeleton that made up the cone. The parts are, from the arms-most to ...

which have been recorded approximately 33 million years before the Triassic-Jurassic boundary. There appears to have been a replacement of Belemnitina with the sub-order Belemnopseina in North-western Europe before the Berremian-Aptian boundary. The long interval (47 million years) between the extinction in the Mediterranean region (Oxfordian) and that in North-western Europe (Aptian) implies that the Belemnitina survived in geographically isolated regions.

References

{{Taxonbar, from=Q4882172 Belemnites Early Jurassic first appearances Early Cretaceous extinctions