Tissotiidae is a family of ammonites (

Ammonitina Ammonitina comprises a diverse suborder of ammonite cephalopods that lived during the Jurassic and Cretaceous periods of the Mesozoic Era. They are excellent index fossils, and it is often possible to link the rock layer in which they are found t ...

) belonging to the

Acanthoceratoidea Acanthoceratoidea, formerly Acanthocerataceae, is a superfamily of Upper Cretaceous ammonoid cephalopods belonging to the order Ammonitida, and comprising some 10 or so families.W.J Arkell ''et al''., Mesozoic Ammonoidea; Treatise on Invertebrate ...

. The Tissotiidae are derived from the

Vascoceratidae The Vascoceratidae is a family of Upper Cretaceous ammonites in the superfamily Acanthoceratoidea characterized by shells that are either smooth or bluntly tuberculate, or have sparse, coarse ribs. Sutural elements are shallow, irregular, and sli ...

, 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:Fossilworks
/ref> *'' 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 The ''Treatise on Invertebrate Paleontology'' (or ''TIP'') 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 co ...

, Part L, Ammonoidea: Geol Soc of America and Univ Kansas Pres. R.C; Moore (ed). Ammonitida families Acanthoceratoidea Turonian first appearances Santonian extinctions {{Ammonitina-stub