Microderoceras

Microderoceras is a flat sided, evolute, radially ribbed Lower Jurassic ammonite belonging to the ammonitid family Eoderoceratidae and superfamily Eoderoceratoidea. Its whorls are subquadrangular in section; venter on the outer rim, rounded; sides with two rows if distinct spines, tubercles on internal molds, formed at either end of the ribs. The lateral surface of the ribcage is concave toward both sides, the lateral side of the dorsal and the lateral side of the ventral surface. The ribs are divided into six pairs (1-3) of the following types: 2-3 is the only type. In the first type, the ribs on the ventral face are fused to the ribs on the ventral sides; the ribs on the dorsal face are fused to the ribs on the dorsal sides. The second type represents the ribbed body, the ribs are in the same arrangement as in the first type and the rib cage does not fuse to the dorsal surface.

Microderoceras
Temporal range: Sinemurian[1]
Scientific classification
Kingdom: Animalia
Phylum: Mollusca
Class: Cephalopoda
Subclass: †Ammonoidea
Order: †Ammonitida
Family: †Eoderoceratidae
Genus: †Microderoceras
Hyatt, 1871
Species [2]
  • Microderoceras birchi
  • Microderoceras nautilum

These shelled cephalopods, named by Alpheus Hyatt in 1871, are part of the now extinct Ammonoidea, which are distinct from the shelled nautiloids still found living today.

Distribution

Argentina, Canada and the United Kingdom.[2]

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References
Notes
  1. Sepkoski, Jack (2002). "A compendium of fossil marine animal genera (Cephalopoda entry)". Bulletins of American Paleontology. 363: 1–560. Archived from the original on 2016-02-25. Retrieved 2017-10-18.
  2. "Paleobiology Database - Microderoceras". Retrieved 2017-10-19.
Bibliography
  • Arkell et al., 1957. Mesozoic Ammonoidea, in Treatise on Invertebrate Paleontology, (Part L); Geological Soc. of America and University of Kansas press
  • Donovan, Callomon and Howarth 1981 Classification of the Jurassic Ammonitina; Systematics Association.


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