When dealing with neoselachian dentitions, there are certain terms that are commonly used, others which are selectively employed, and some which carry different meanings by various authors. This page will attempt to define the terms used in this report and expand upon the more important aspects. The sections on this page include:


Chondrichtyan dentitions have been grouped into a number of general designs based upon the function of the teeth. These dentitions may be simple (made up of similar tooth-types) or more often, intermixed types (complex) within a given dentition, inorder to provide the necessary functionality.

It's the Root, Stupid

The root of a chondrichthyan tooth, requires particular attention. A half century ago a Belgian paleontologist, Edgar Casier, proposed four root types based largely upon the root's structure, foramina and nutrient groove. The nomenclature is useful when attempting to categorize a root design, and there certainly appears to be a trend in neoselachians, the modern sharks, to have bilobate roots, rather than the simple structures of their Paleozoic and early Mesozoic forerunners; but, I wouldn't want to reclassify sharks based upon them.

The carryover Paleozoic design he referred to as anaulacorhizous roots (i.e. the flat porous roots of Notorynchus); holaulacorhizous was applied to the typical bilobate roots (i.e., Carcharias) and hemiaulacorhizous for an intermediate design where a canal served to connect a basal foramen to one on the lingual side of the root -- an incomplete nutrient groove (Squatina). The batomorphs appeared in the late Jurassic and maintained the bilobate design until the upper Cretaceous when two superfamilies (Myliobatoidea and Mobuloidae) enter the fossil record. They would bear mesio-distally elongated teeth with multiple nutrient grooves -- polyaulacorhizous roots.

Once this root style is determined when working with batoid teeth, other root and crown characteristics can often be differentiated to establish the relevant family. This will often lead directly to a genus.

Files & Series, Columns & Rows

If there are terms that cause confusion, controversy and/or debate, they are the nouns chosen to describe a group of teeth running either front to back or side to side. Reading the descriptions provided by various authors, there appeared to be no universal agreement if a "row" of teeth ran laterally (mesio-distally) or from front to back (labio-lingually). This inconsistent usage was undoubtedly noted by others, and the terms "series" (mesio-distal) and "file" (labio-lingual) now appear much more often. I recently read a publication that abandoned both terms. For additional details on this confusion see Roe vs Row. The definition for the terms used within this website include:


Figure 1 (below) shows a Raja (skate) tooth from five angles. From left to right and top to bottom, they are: lateral (side), labial (outer), lingual (inner), basal (bottom) and occlusal (or apical, top). Note that in ray teeth, the roots are displaced lingually. It is hard enough to ascribe a tooth to a genus, let alone distinguish male from female, upper from lower, mesial from distal, or right from left. With this handicap, a term such as mesio-distal is used without identifying which is which.

A cuspal view (not illustrated) is useful with certain batoid teeth. This is a view done perpendicular to the cusp (in batoids, this would be the labial face). This perspective is commonly used for shark teeth but is refered to a labial or lingual. With batoid teeth, labial and cuspal views can be quite different.

Terminology by Illustration.

Fig. 1.   The accompanying illustration depicts some of the more common terms or references which may appear when describing ray teeth: uvula, visor, face, cusp, transverse crest, cutting edge, median ridge, central foramen, nutrient groove and notch. Many of these terms may be modified by refering to them as labial, lingual, mesial or distal (see Orientation above).

Fig. 2. This illustration depicts some of the terms
or references which may appear when describing

Fig. 3. Dasyatid teeth have certain common features.

Tooth terminology.

Reading various publications, there is not only different terms used when providing descriptions, but the same terms are sometimes used with opposite definitions (see "file" and "row"). The below list provides the definitions I am using in this study; in most cases, they are the commonly used terms. Any term I have coined, am using in a more narrow context, or am using without seeing it described in a another glossary, will be italicized. In addition, certain terms will be clarified with the above illustrations.



Fig. 4. Measurements
I have no idea if there is a proper method of measuring these teeth. For discussion purposes, I employ the illustrated method in which the base of the crown is placed approximately level and the broadest/widest part (of the crown and/or root) is measured. Note that each measurement is "overall". In many instances, the dimensions of the the crown's basal margin are most relevant, particularly for comparrisons. A "bc" prefix" will indicate as basal crown measurement (i.e., bcDep).