Dactylioceras commune

Overview

Dactylioceras commune is an ammonite with a shell that exposes its inner whorls. The genus diagnosis describes simple or branching ribs. The large spiral and small surface repetitions can be examined together.^[1]

Key facts

The shell’s arrangement reveals the inner coils as well as the outer whorl. Surface ribs continue singly or branch. The repetition of whorls and branching of ribs can be read at different scales.^[1]

Time and place

This is a Jurassic ammonite. The Jurassic spanned approximately 200–140 million years ago. Taxonomic publications and species-level specimen records provide evidence for exploring its shell features.^[1][3]

The time range describes source context, not the complete duration of this species.

Size, form and skeleton

The genus diagnosis describes a shell with visible inner whorls and simple or branching ribs. Surface branching can be examined within the broader arrangement of connected coils. Different kinds of repetition occur on the same shell.^[1]

Dactylioceras commune is an ammonite with visible inner whorls. One Jurassic fossil from the Mecsek Mountains in present-day Hungary had a shell diameter of 7.3 cm. Following rib-like ridges from the center outward allows shell size and repeated ornamentation to be explored together.^[4]

Habitat and reproduction

Which parts of a coiled shell can be compared? The exposure of inner whorls and branching of surface ribs are different features. Reading both the broad outline and small surface details helps distinguish similar ammonites.^[1]

Fossil discovery

Taxonomic literature on cephalopods summarizes the type species, plate explanations, and genus diagnosis of Dactylioceras. Museums also hold records under the species name commune. These sources connect the reference for a name with shell form.^[1][2]

References

1. Cephalopod classification literature — Dactylioceras
2. National Museum of Natural History, Paris — Dactylioceras commune
3. International Commission on Stratigraphy (2024) — Geological time chart
4. Kovács et al. (2023) — Jurassic ammonites from the Mecsek Mountains, Hungary
5. Gomez-Cruz et al. (2015) — Ammonite specimens from the Rosablanca Formation
6. Treatise — The names Lissonia and Hoplites riveroi

Research questions

Where does one rib divide into two? Examining the surface along the whorl reveals the relationship between repetition and branching. This involves comparing different regions of the same shell in sequence.^[1]

Observation

Follow the coiled whorls from inside to outside. Then examine the simple and branching surface ribs to connect the broad outline with small repetitions.^[1]