Tissotiidae

Tissotiidae Temporal range: U Cretaceous Turonian- Lower Santonian.
Fossil of Tissotia species from Wawat in the Sudanese Nubian desert
Scientific classification
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Cephalopoda
Subclass:	†Ammonoidea
Order:	†Ammonitida
Superfamily:	†Acanthoceratoidea
Family:	†Tissotiidae Hyatt, 1900

Tissotiidae is a family of ammonites (Ammonitina) belonging to the Acanthoceratoidea.

The Tissotiidae are derived from the Vascoceratidae, another acanthoceratoid family, and gave rise to the Coilopoceratidae. They have been divided into two subfamilies, the earlier and more primitive Pseudotissotiinae and the more advanced and later Tissotiinae, which differ only in the details of the suture. (ibid)

Genera

Genera within the family Tissotiidae include:

• Heterotissotia Peron, 1897
• Metatissotia
• Paratissotia
• Tissotia Douvillé, 1890
• Tissotioides Reyment, 1958

Description

Members (genera) of the Tissotiidae tend to have smooth, strongly involute shells with deeply impressed inner rims to the whorls where subsequent whorls wrap around those prior. Shells may be narrow and discoidal, broad and subspheroidal, or in between. Sides commonly have broad ribs, and on some, tubercles. The outer rim, known as the venter, may be wide and nearly flat, rounded, or narrow and even sharp. The suture in tissotiids is generally simple, either a simple form of ammonitic or ceratitic with smooth rounded saddles divergent forward and serrate lobes pointing to the rear. (Arkell et al.)

References

• Arkell, W.J. et al., Mesozoic Ammonoidea in the Treatise on Invertebrate Paleontology, Part L, Ammonoidea: Geol Soc of America and Univ Kansas Pres. R.C; Moore (ed).