''Dactylioceras'' was a widespread

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

ammonite Ammonoids are a group of extinct marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda. These molluscs, commonly referred to as ammonites, are more closely related to living coleoids (i.e., octopuses, squid and cuttlefish) ...

s from the

Lower Jurassic The Early Jurassic Epoch (in chronostratigraphy corresponding to the Lower Jurassic Series) is the earliest of three epochs of the Jurassic Period. The Early Jurassic starts immediately after the Triassic-Jurassic extinction event, 201.3 Ma&nb ...

period, approximately 180 million years ago ( mya).

Etymology

The name ''Dactylioceras'' comes from the

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

''dactyl'', meaning “finger”, and refers to the shell's branching ribs.

Description

''Dactylioceras'' are generally small, averaging in diameter. They have a strong, ribbed shell. The ribs are slightly inclined forward, running over the outer edge, and either simple or forking at outer end. Though they eventually died out 180 mya, their style of ribbing was copied by numerous subsequent ammonite genera until the whole group became extinct 66 million years ago with the

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

Ecology

''Dactylioceras'' probably lived by scavenging on the sea floor. Mass mortality specimens of ''Dactylioceras'' are common, and perhaps suggest that these ammonites may often have died shortly after spawning. The dead shells were probably gently washed up into a shell bank on the margins of the Lower Jurassic seas. Flow tank experiments show that ''Dactylioceras'' was probably a slow swimmer.

Distribution

''Dactylioceras'' has been collected from almost every

continent A continent is any of several large landmasses. Generally identified by convention rather than any strict criteria, up to seven geographical regions are commonly regarded as continents. Ordered from largest in area to smallest, these seven ...

, and was one of the most successful ammonite lineages ever. They are abundant throughout

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...

, with exceptionally fine specimens found in England and Germany. Like many other ammonites, the genus ''Dactylioceras'' is extremely important in

biostratigraphy Biostratigraphy is the branch of stratigraphy which focuses on correlating and assigning relative ages of rock Stratum, strata by using the fossil assemblages contained within them.Hine, Robert. “Biostratigraphy.” ''Oxford Reference: Dictiona ...

, being a key

index fossil Biostratigraphy is the branch of stratigraphy which focuses on correlating and assigning relative ages of rock Stratum, strata by using the fossil assemblages contained within them.Hine, Robert. “Biostratigraphy.” ''Oxford Reference: Dictiona ...

for identifying their region of the Jurassic.

Subgenera

Currently, 3 or 4 subgenera are considered to be valid. Number differs on authors opinions. * ''D. (Dactylioceras)'' Hyatt, 1867: type species: ''Ammonites communis'' Sowerby, 1815 * ''D. (Orthodactylites)'' Buckman, 1926: type species: ''Dactylioceras directus'' Buckman, 1926 * ''D. (Iranodactylites)'' Repin, 2000: type species: ''Dactylioceras (Iranodactylites) ketevanae'' Repin, 2000 * ''D. (Eodactylites)'' Schmidt-Effing, 1972: type species: ''Dactylioceras pseudocommune'' Fucini, 1935. This subgenus is not recognized by some authors, while some other prefer to maintain it.KOVÁCS, Zoltán. "Toarcian Dactylioceratidae (Ammonitina) from the Gerecse Mts (Hungary)." (2014): 45-77.

Species

Species within the genus ''Dactylioceras'' include:Dactylioceras
on the

Paleobiology Database The Paleobiology Database is an online resource for information on the distribution and classification of fossil animals, plants, and microorganisms. History The Paleobiology Database (PBDB) originated in the NCEAS-funded Phanerozoic Marine Pale ...

* ''D. (O.) aequistriatum'' Zieten, 1830 * ''D. (D.) alpestre'' Wiedenmayer, 1980 * ''D. (D.) amplum'' Dagis, 1968 * ''D. (O.) andaluciensis'' Jiménes & Rivas, 1991 * ''D. (O.) anguiforme'' Buckman, 1928 * ''D. (O.) anguinum'' Reinecke, 1818 * ''D. (D.) annuliferum'' Simpson, 1855 * ''D. (D.) arcus'' Buckman, 1926 * ''D. (D.) athleticum'' Simpson, 1855 * ''D. (D.) attenuatum'' Simpson, 1855 * ''D. (O.) chilense'' Hillebrandt and Schmidt-Effing, 1981 * ''D. (O.) clevelandicum'' Howarth, 1973 * ''D. (D.) commune'' Sowerby, 1815 * ''D. (D.) comptum'' Dagis, 1968 * ''D. (D.) consimile'' Buckman, 1926 * ''D. (D.) crassescens'' Simpson, 1855 * ''D. (O.) crassifactum'' Simpson, 1855 * ''D. (O.) crassiusculosum'' Buckman, 1912 * ''D. (D.) crassiusculum'' Simpson, 1855 * ''D. (D.) crassulum'' Buckman, 1921 * ''D. (D.) crosbeyi'' Simpson, 1843 * ''D. (O.) directum'' Buckman, 1926 * ''D. (O.) ernsti'' Lehmann, 1968 * ''D. (D.) gracile'' Simpson, 1843 * ''D. (O.) helianthoides'' Yokoyama, 1904 * ''D. (O.) hispansum'' Schmidt-Effing, 1972 * ''D. (O.) hoelderi'' Hillebrandt & Schmidt-Effing, 1981 * ''D. (D.) holandrei'' d'Orbigny, 1845 * ''D. (O.) ketevanae'' Repin, 2000 * ''D. (O.) kanense'' McLearn, 1930 * ''D. (I.) ketevanae'' Repin, 2000 * ''D. (D.) laticostatum'' Bardin et al., 2014 * ''D. (O.) marioni'' Lissajous, 1906 * ''D. (E.) mirabile'' Fucini, 1935 * ''D. (D.) mite'' Buckman, 1927 * ''D. (D.) peloritanum'' Fucini, 1935 * ''D. (D.) percostatum'' Fucini, 1935 * ''D. (D.) perplicatum'' Fucini, 1935 * ''D. (E.) polymorphum'' Fucini, 1935 * ''D. (D.) praepositum'' Buckman, 1927 * ''D. (E.) pseudocommune'' Fucini, 1935 * ''D. (D.) pseudocrassoides'' Maubeuge, 1957 * ''D. (O.) sapunovi'' Repin, 2000 * ''D. (O.) semiannulatum'' Howarth, 1978 * ''D. (O.) semicelatum'' Simpson, 1843 * ''D. (E.) simplex'' Fucini, 1935 * ''D. (D.) stresherense'' Sapunov, 1963 * ''D. (D.) subholandrei'' Fucini, 1935 * ''D. (D.) suntarense'' Krimholz, 1957 * ''D. (D.) tardosensis'' Kovács, 2014 * ''D. (D.) tauromenense'' Fucini, 1935 * ''D. (D.) temperatum'' Buckman, 1927 * ''D. (O.) tenuicostatum'' Young & Bird, 1822 * ''D. (O.) toxophorum'' Buckman, 1926 * ''D. (D.) triangulum'' Fischer, 1966 * ''D. (D.) vermis'' Simpson, 1855 * ''D. (O.) wunnenbergi'' Hoffmann, 1968 Dactylioceratidae - Dactylioceras commune

Dactylioceratidae - Dactylioceras commune

''Dactylioceras commune'' has shells reaching a diameter of . Usually the average diameter reach about , while the average width is . In these small but strong shells ribs run straight or are slightly convex across the venter. These ribs are quite coarse on the outer whorls and finer on the inner whorls. The whorl section is as round as a circle.Ammonites
/ref> Fossils of this species have been found in

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 ...

age of Canada, France, Italy, Russia, Serbia and Montenegro, United Kingdom and United States.

References

* {{Taxonbar, from=Q1452422 Ammonitida genera Dactylioceratidae Jurassic ammonites Early Jurassic ammonites of Europe Fossils of Serbia