Stephanocerataceae
Encyclopedia
Stephanocerataceae is a superfamily of middle Jurassic ammonoid cephalopods within the order Ammonitida containing diverse forms, generally with sharp ribbing and complex suture lines. Aptychi
are believed to be mostly granular (Granulaptycus) or concentrially ribbed on the surface (Praestriaptychus) (Arkell et al. 1957)
, 1957 Part L. They are the:
The Pachyceratidae and Tulitidae included in the Stephanocerataceae in the Treatise (1957) are reassigned to the Perisphinctaceae
. The Macrocephalotidae and Mayaitidae of the Treatise are reduced to subfamilies within the Spaeroceratidae, Macrocephalitinae and Mayaitinae, but still in the Stephanocerataceae. The Clydoniceratidae and Thamboceratidae are combined as the Clydoniceratinae within the Hildoceratacean
family Oppeliidae.
This differs from the older phylogeny of the Treatise
Part L the Stephanocerataceae are thought to be derived from the Hammatoceratidae (Hildocerataceae
) through the ancestral family, the Otoitidae which gave rise in the early MIddle Jurassic to the Stephanoceratidae and Sphaeroceratidae, forming two main lineages. The Stephanoceratidae gave rise to the Thamboceratidae which in turn gave rise to the Clydoniceratidae. The Sphaeroceratidae gave rise to the Tulitidae which is the source for both the Macrocephalitidae and the Pachyceratidae. The Pachyceratidae lead to the Mayitidae, the Macrocephalitidae both the Kosmoceratidae and Cardioceratidae.
Aptychus
An aptychus is a type of marine fossil, a hard anatomical structure like a curved shelly plate, which was part of the body of an ammonite. Paired aptychi have, on rare occasions, been found at or within the aperture of ammonite shells....
are believed to be mostly granular (Granulaptycus) or concentrially ribbed on the surface (Praestriaptychus) (Arkell et al. 1957)
Morphologic Variation
The shells of the Stephanocerataceae, which determine the different included families, are highly variable in form. They are discoidal and evolute with all whorls exposed, spheroidal and involute with only the outer whorl showing, cadiconic with a deep umbilicus and broad ventral margin, and oxiconic with the ventral margin sharp. They are united by being generally sharply ribbed and by their complex suture lines with a dominant 1st lateral lobe and a well-developed umbilical lobe. (Arkell et al. 1957)Taxonomy
The Stephanocerataceae contains five families according to Donovan et al. (1981), a reduction from the 11 listed in the TreatiseTreatise on Invertebrate Paleontology
The Treatise on Invertebrate Paleontology published by the Geological Society of America and the University of Kansas Press, is a definitive multi-authored work of some 50 volumes, written by more than 300 paleontologists, and covering every phylum, class, order, family, and genus of fossil and...
, 1957 Part L. They are the:
- StephanoceratidaeStephanoceratidaeSephanoceratidae is a family of planulate and coronate ammonites within the Stephanocerataceae. Shells are evolute so that all whorls are exposed and have strong ribbing that bifurcates, that is splits in two, on the flanks. Many have tubercles at the point of bifurcation...
- Kosmoceratidae
- OtoitidaeOtoitidaeOtoidtidae: stephanoceratacean ammonitina from the early Middle Jurassic that begin as cadicones but become more planualte with age; derived from the Hammitoceratidae , probably through Erycites by way of Abbasites....
- Sphaeroceratidae
- Cardioceratidae
The Pachyceratidae and Tulitidae included in the Stephanocerataceae in the Treatise (1957) are reassigned to the Perisphinctaceae
Perisphinctaceae
Perisphinctoidea, formerly Perisphinctaceae, is a superfamily of Middle Jurassic to Lower Cretaceous ammonites, commonly with evolute shells with strong ribbing that typically divides about mid flank before crossing the venter....
. The Macrocephalotidae and Mayaitidae of the Treatise are reduced to subfamilies within the Spaeroceratidae, Macrocephalitinae and Mayaitinae, but still in the Stephanocerataceae. The Clydoniceratidae and Thamboceratidae are combined as the Clydoniceratinae within the Hildoceratacean
Hildocerataceae
Hildocerataceae is a superfamily of compressed or planulate ammonites, some tending to develop acute outer rims; generally with arcuate or sigmoidal ribs. Aptichus were found in place are double-valved....
family Oppeliidae.
Phylogeny
According to Donovan et al (1981) the Stephanoceratidae and Otoitdae both have there origin in the Hildocerataceae, in the Phymatoceratidae. The Otoitidae gave rise to the Sphaeroceratidae which gave rise to the Cardioceraticae, the Stephanoceratidae to the Kosmoceratidae, all within the Stephanoceratacae. The Stephanoceratidae, accordingly, also gave rise to the Perisphinctidae, root stock of the Perisphictaceae.This differs from the older phylogeny of the Treatise
Treatise on Invertebrate Paleontology
The Treatise on Invertebrate Paleontology published by the Geological Society of America and the University of Kansas Press, is a definitive multi-authored work of some 50 volumes, written by more than 300 paleontologists, and covering every phylum, class, order, family, and genus of fossil and...
Part L the Stephanocerataceae are thought to be derived from the Hammatoceratidae (Hildocerataceae
Hildocerataceae
Hildocerataceae is a superfamily of compressed or planulate ammonites, some tending to develop acute outer rims; generally with arcuate or sigmoidal ribs. Aptichus were found in place are double-valved....
) through the ancestral family, the Otoitidae which gave rise in the early MIddle Jurassic to the Stephanoceratidae and Sphaeroceratidae, forming two main lineages. The Stephanoceratidae gave rise to the Thamboceratidae which in turn gave rise to the Clydoniceratidae. The Sphaeroceratidae gave rise to the Tulitidae which is the source for both the Macrocephalitidae and the Pachyceratidae. The Pachyceratidae lead to the Mayitidae, the Macrocephalitidae both the Kosmoceratidae and Cardioceratidae.