EXTANT BATOIDS

Stingray Glossary

Jim Bourdon
Illustrated by Jim Bourdon, Copyright © 1997

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:

Chondrichthyan Dentition-types
Tooth Files and Series
The Root of a Chondrichthyan Tooth
Orientation or Viewing Aspects
Illustrated Terminology
Defined Terminology
Orientation or Viewing Aspects
Measurments

Dentition-types

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.

Grasping.

Carcharias

Clutching.

Cutting.

Galeocerdo

Vestigal.

Megachasma & Rhinocodon

Crushing.

Grinding.

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. The definition for the terms used within this website include:

Dentition. The default definition would be all the teeth and their arrangement in the mouth (both jaws). This may be modified to include only the upper or lower.
File = Column. A labio-lingual group of teeth the include the functional and replacement teeth.
Series = Row. A mesio-distal group of teeth each of which will be functional or replacement.
Position. By default, refers to the mesio-distal location (which file), may be specifically modified to indicate a labio-lingual location (which series) or both (i.e. UL6/3 = Upper Left, 6th tooth to left, 3rd tooth in).
File/Tooth Count. The number of teeth in a series or row from one distal position to the other.
Tooth Numbering. Teeth will be counted from the medial position to the distal. If a symphyseal is present it will be noted as "S". It is not uncommon to encounter an assymetrical ray dentition, therefore a particular dentition may have a tooth count of 44 teeth numbered 21-S-22 which would equate to 21 teeth to the left of center, 22 to the right plus a symphyseal (21-:-22 would refer to tooth count of 43, teeth 1-21 to the left and 1-22 to the right, no symphyseal).

Orientation.

Figure 1 (below) shows a Raja (skate) tooth from five angles. From left to right and top to bottom, they are: lateral (side), lingual (inner), labial outer), occlusal (apical, top) and basal (bottom). Note that in ray teeth, the roots are displaced lingually. Illustrations usually include more than one of these viewing aspects. A cuspal view (not illustrated) is useful with certain batoid teeth. This is a view done perpendicular to the cusp (in stingrays, 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 stingray teeth: uvula, transverse crest, median ridge, central foramen, nutrient groove and grooves Many of these terms may be modified by refering to them as labial, lingual, mesial or distal (see Orientation above).

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..

anterior (1) = when referring to a position on a tooth, synonymous with labial.

anterior (2) = when referring to a tooth's position in a series or a file in a dental band, nearer the symphysis.

anterior (3) = when comparing teeth within a file or series within a dental band, a more labial position.

apical = toward the tip or apex of the crown.

apron = In batoids, the portion of the basal labial coronal face which overhangs the root stem. In sharks, used to refer to the continuation of the crown's enameloid over the labial face of the root.

asymmetrical = when used to refer to root lobes, this term means that the footprints of each lobe are different in shape, orientation, or significantly, in size.

basal = referring to the bottom of a structure.

benthic = living near the bottom.

bisected lobe = a lobe that has a marked lateral longitudinal notch on the external face.

central foramen = a single large foramen in the base of the nutrient groove.

central pore = a single large hole in the base of the nutrient groove made up of 1 or more foramina.

cf. - confer = compare with

clutching dentition = a dentition intended to hold prey, see Dentition-types.
collar (MOBULIDAE only) = the portion of the basal lingual coronal face which overhangs the root stem. It is a transversely expanded uvula.
crown = enameloid-covered dentine portion of tooth (not connected to the jaw).
crown foot = the juncture of crown and root.
crushing dentition = a dentition used to fracture shells or other hard material, see

Dentition-types.

cusp = a major projection of the crown. It had been long thought that when present in batoids (skates, stingrays, devil rays...) that these were usually male characteristic. Kajiura & Tricas (1996) have shown that in at least one species, Dasyatis sabina, that they are present in males only during the breeding season. In pelagic stingrays, both sexes have cuspidate teeth.
cuspal angle (DASYATIDAE) = When viewing a high-cusped tooth laterally, the cusp portion of the crown becomes lingually directed some distance above the base of the crown. This location, where the the labially sloping lower crown meets the cusp is refered to herein as the cuspal angle. It is limited to usage for the lingual face and has properties which include the sharpness of the 'flex' pont, the acuteness of the cusp's re-direction and the relative distance above the base of the crown.
cutting dentition = a dentition used to cut flesh, see

Dentition-types.

cutting edge = a sharp, thin enameloid ridge, not found on stingray teeth.
dentine = a hard calcified material of mesodermal origin.
depth = refers the labio-lingual direction or measurement of the crown, root and/or tooth parallel to the crown foot, see Measurements.
(dermal) denticles = small placoid scales embedded in and protruding from the skin.
(dermal) thorns = a dermal denticle with an enameloid thorn or cusp-like protuberance.
dignathic heterodonty = teeth differ between upper and lower jaws.
distal = toward commissure or end of the jaw. Usually refers to file(s), but can be used for particular teeth within a series.
enameloid = the smooth and glossy enamel-like tissue coating the crowns of elasmobranchs. Formed of extremely dense dentine and of mixed ectodermal and mesodermal origin.
file (aka row to some authors) = labio-lingual column of teeth, which includes functional & replacements, see Files & Series.
file counts The number of files in a dental band, see Files & Series.
file numbering see Files & Series.
footprint = term used to describe the shape of a root lobe when viewed basally.
foramen = an opening or hole into the root.
functional teeth or series = Teeth currently being used, see Files & Series.
groove (dasyatoids only) = a furrow or any other elongated depression in the crown's surface more likely created by the valley between enameloid ridges than by depressions in an otherwise flat surface.
grinding dentition = A plate-like dentition used to grind hard-bodied food, see Dentition types.
height = as a measurement, it applies to the apico-basal distance perpendicular to the crown foot.
heterodont = Term used to describe teeth which change shape and/or size in different regions of the jaw.
homodont = little or no difference in a tooth's size or shape in different regions of its dentition.
labial (aka outer, anterior series) = toward the front of the mouth (tooth).
labial flange = a basally directed, labial crown protuberance extending below the crown foot.
lateral (1) = when referring to a position on a tooth, used to indicate mesial and/or distal.
lateral (2) = when referring to a tooth's position: if a series is made up of the two file-types, medial and lateral, this would be the distal tooth-type; if the the series is made up of three or more tooth-types (anterior-lateral-posterior), this would refer to a middle file-group from within the series.
lateral angle = the location on the rim that represents the widest point of the crown.
lateral foramen = refers to a foramen on the internal face of a root lobe usually adjacent to central foramen.
lingual (aka inner, posterior series) = toward the rear of the tooth, see Orientation.
lingual depression = a depression above the uvula and below the cusp that accommodates the next posterior tooth of a particular file.
lingual uvula (aka lingual protuberance) = a uvula extending over the lingual root stem in a median position between the root lobes.
lobe (1, sharks) = the mesial or distal portion of the root created by the nutrient groove.
lobe (2, rays) = the multiple basal extensions of the root which are created by the nutrient groove(s).
longitudinally = referring to a structure that is apico-basally oriented.
longitudinal notch = a longitudinally oriented notch on the face of a root or root lobe.
mandibular cartilage = refers to the cartilage component of the lower jaw.
median = when referring to a tooth, refers to the labio-lingual mid-line or cross-section.
median ridge = a labio-lingual ridge extending in a median position on a face of the crown.
mesial (aka anterior file) = toward symphysis or junction of left and right jaws. Usually refers to file(s), but can be used for certain teeth of a series.
monognathic heterodonty = Tooth odontology changes within the same jaw.
notch = a groove situated on a face of the root. Usually applied to the nutrient groove (basal face) but expand herein to encompass longitudinal notches on the (lateral) faces of a root lobes.
nutrient groove (aka Herman's median groove) = a notch or groove separating lobes or lobets which contains the central foramen or foramina.
occlusal = refers to viewing the tooth's crown from an apical aspect (from the top), see Orientation.
odontological = refering to the form and structure of a tooth.
ontogenetic heterodonty = used to refer to changes in tooth design associated with age.
palatoquadrate cartilage = refers to the cartilage component of the upper jaw.
parasymphyseal = In the absence of a symphyseal, these are the first on either side of the symphysis.
pathological = abnormalities of a tooth usually associated with injury or disease.
pelagic = open ocean.
polyaulacorhizous = root made up of more than one nutrient groove, a characteristic of myliobatoids and mobuloids, see It's the Root.
posterior (1) = when referring to a position on a tooth, synonymous with lingual.
posterior (2) = when referring to a tooth's position in a series or a file in a dental band, equates to distal.
posterior (3) = when comparing teeth within a file or series within a dental band, a more lingual position.
pulp cavity = an open area inside the crown of an orthodont tooth.
replacement teeth or series = lingually positioned teeth not yet in use, see Files & Series.
rim (RAJIDAE only) = the widest margin of the crown between the crown foot and base of the cusp.
root = non-enamelated (dentine) portion of tooth which attaches the tooth to the jaw.
root coating = coating of upper part of root which may be enameloid.
root stem = portion of root between base of crown and root lobe.
row (aka file to some authors) = mesio-distal line of teeth, see Files & Series.
scalloped collar = a collar which has a weak or strong wave-like appearance created by the presence of multiple uvulae.
seed teeth = refers to teeth in the lingual most position of a file which are in the process of germinating.
series or row = a mesial-distal string of teeh in a similar position, see Files & Series.
series counts = the number of tooth series in a particular dentition, see Files & Series.
sexual dimorphism = differences in morphological characteristics between sexes of the same species.
splayed = when referring to the relative position of root lobes to each other, splayed indicates that they grow wider apart labially.
shed teeth = Teeth of the labial most series which have been worn and are no longer part of a functional series. They are in the process of being shed.
symmetrical = when applied to root lobes, the footprints are of similar shape, size and orientation.
tooth band = refers to all the teeth (upper or lower) of a particular jaw. Depending on the design of the dentition, the tooth band may divided into one to three regions. One is reserved for Aetobatus which has a single, laterally elongated, tooth. Two assigns all teeth to a mesial (for medial teeth) or distal (lateral teeth) position. When the tooth band is divided into three regions, the mesial region will include 'symphyseal' and 'anterior' teeth, the lateral, 'lateral' teeth and the distal, 'posterior' teeth. The 'tooth band' as employed refers to all the the teeth (files and series) that are in the dermis below the palatoquadrate, or above the mandibular, cartilage.
transverse depression (Dasyatoids only). Refers to a mesio-distal depression in the labial face of the crown. It's located posterior to the labial margin of the crown and its ornamentation. (In non-cuspidate teeth, this is just anterior to the transverse ridge and in cuspidate teeth, between the cusp and the lower labial face of the crown).
transverse ridge (aka median keel, transverse crest) = Ridge which divides the labial face of the crown from the lingual face.
transverse cutting edge = a cutting edge that follows the transverse ridge. When present, it may be limited to a portion of the cusp or extend to the rim and even follow it labially toward the visor.
trough = a depression between two coronal structures.
uvula = a basally directed protuberance of the crown extending below the crown foot.
viewing aspects = the surface of the object being viewed directly when a tooth or other object is being held in a particular orientation, see Orientation.

apical/occlusal - From the top.
basal - From the bottom
cuspal -viewed perpendicular to the cusp face.
labial - from the front
lateral - from the side
lingual - from the back

width = the mesio-distal dimension or measurement of the crown, root or tooth.

Measurement.

Fig. 2. 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).

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Page added April 15, 1997, last modified July 27, 1997.