was a widespread genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Ammonite, as a zoological or paleontological term, refers to any member of the Ammonoidea an extinct subclass within the Molluscan class Cephalopoda which are more closely related to living coleoids Ammonite, as a zoological or paleontological term, refers to any member of the Ammonoidea an extinct...
from the Jurassic
The Jurassic is a geologic period and system that extends from about Mya to Mya, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the age of reptiles. The start of the period is marked by...
period, approximately 172 million years ago (mya). They are generally small, averaging 65 mm in diameter.
has a strong, ribbed shell. The ribs are slightly inclined forward, running over the outer edge, and either simple or forking at outer end. Though it eventually died out 180 mya, their style of ribbing was copied by numerous subsequent ammonite genera until the whole group became extinct 65 million years ago with the dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
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.
has been collected from almost every continent
A continent is one of several very large landmasses on Earth. They are generally identified by convention rather than any strict criteria, with seven regions commonly regarded as continents—they are : Asia, Africa, North America, South America, Antarctica, Europe, and Australia.Plate tectonics is...
, and was one of the most successful ammonite lineages ever. They are abundant throughout Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
, 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 strata by using the fossil assemblages contained within them. Usually the aim is correlation, demonstrating that a particular horizon in one geological section represents the same period...
, being a key index fossil
Index fossils are fossils used to define and identify geologic periods . They work on the premise that, although different sediments may look different depending on the conditions under which they were laid down, they may include the remains of the same species of fossil...
for identifying their region of the Jurassic.
The name Dactylioceras
comes from the Greek
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
, meaning “finger”, and refers to the shell’s branching ribs.