DACTYLIOCERATIDAE
DACTYLIOCERATIDAE
Origins: 192 million years ago (Early Jurassic, Pliensbachian stage)
Extinction: 174 million years ago (Early Jurassic, Toarcian stage)
Dactylioceratids is a family that comprises Early Jurassic ammonites with ribbed and commonly tuberculate shells, similar to those of the mid-late Jurassic stephanoceratid and perisphincitd families.
These ammonites usually have shells that are evolute, serpenticone or cadicone, with ribs and sometimes with tubercles. It is divided in two subfamilies, one of them being the Reynesocoeloceratinae, which possesses two major secondary lobes in the dorsal side of the external saddle, saddle which is not divided that way in the second subfamily, the Dactylioceratinae.
The earliest representatives of the family come from the early Pliensbachian stage, with the dactylioceratines, specifically, first arising in the late Pliensbachian stage, and eventually the family disappears at the end of the Toarcian stage.
main source: Wikipedia
PHYLOGENY
- Phylloceras heterophyllum
- Lytoceras fimbriatum
- Dactylioceratidae
- Catacoeloceras crassum
- Dactylioceras commune
NAME: Catacoeloceras crassum
SIZE: 3-7 centimeters of shell diameter
DESCRIBED BY: Young & Bird, 1828
CLOSEST LIVING RELATIVES: Neocoleoids
DEPICTED IN: The Life of a Temnodontosaurus episodes 2 and 3
Catacoeloceras crassum was a species characteristic of the Toarcian stage of the early Jurassic. Its genus existed in various subzones and was found in many continents, including Europe, Africa, North America and South America.
NAME: Dactylioceras commune
SIZE: 2-11 centimeters of shell diameter
DESCRIBED BY: Sowerby, 1815
CLOSEST LIVING RELATIVES: Neocoleoids
DEPICTED IN: The Life of a Temnodontosaurus episode 17
Dactylioceras commune was a species of the genus Dactylioceras, which was an immensely widespread genus of ammonites during the Pliensbachian and Toarcian stages.
The name Dactylioceras comes from the Greek dactyl, meaning “finger”, and refers to the shell's branching ribs, and ceras, which means "horn", a typical suffix for ammonite genera.
The ribs are slightly inclined forward, running over the outer edge, and either simple or forking at outer end, a style of ribbing that was perpetuated in other ammonites up until the end of the Cretaceous.
Dactylioceras appears to have been a slow swimmer, so likely a passive feeder of organic particles that floated in the surface, rather than a large active predator, as other cephalopods it lived with were.
Dactylioceras has been collected from almost every continent, and was one of the most successful ammonite lineages ever, having an immense amount of species recorded.
The exact number of species that the Dactylioceras genus had is under dispute, but they do seem to be divided in a few subgenera. These are Dactylioceras, Orthodactylides, Iranodactylides and Eodactylides.
In these small but strong shells ribs run straight or are slightly convex across the ventral side, and these ribs are quite coarse on the outer whorls and finer on the inner whorls; the whorl section is as round as a circle.