Belemnitina is a

suborder Order () is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between family and class. In biological classification, the order is a taxonomic rank used in the classification of organisms and recognized ...

belemnite Belemnitida (or belemnites) is an extinct order (biology), order of squid-like cephalopods that existed from the Late Triassic to Late Cretaceous (And possibly the Eocene). Unlike squid, belemnites had an internal skeleton that made up the cone ...

s, an extinct group of

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

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 143.1 Mya. ...

to the early

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...

. 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 International Commission on Stratigraphy, ICS' geologic timescale, an age (geology), age and stage (stratigraphy), stage in the Early Jurassic, Early or Lower Jurassic. It spans the time between 184.2 Megaannum, Ma (million ...

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

Pliensbachian The Pliensbachian is an age of the geologic timescale and stage in the stratigraphic column. It is part of the Early or Lower Jurassic Epoch or Series and spans the time between 192.9 ±0.3 Ma and 184.2 ±0.3 Ma (million years ago). The Plie ...

(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-

Aptian The Aptian is an age (geology), age in the geologic timescale or a stage (stratigraphy), stage in the stratigraphic column. It is a subdivision of the Early Cretaceous, Early or Lower Cretaceous epoch (geology), Epoch or series (stratigraphy), S ...

boundary (early Cretaceous).

Stratigraphic range

Belemnitina first appear in the fossil record in the

Hettangian The Hettangian is the earliest age and lowest stage of the Jurassic Period of the geologic timescale. It spans the time between 201.3 ± 0.2 Ma and 199.3 ± 0.3 Ma (million years ago). The Hettangian follows the Rhaetian (part of the Triass ...

(early Jurassic). Two genera, '' Schwegleria'' 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 belemnites) is an extinct order (biology), order of squid-like cephalopods that existed from the Late Triassic to Late Cretaceous (And possibly the Eocene). Unlike squid, belemnites had an internal skeleton that made up the cone ...

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