File Groups

Specimen Numbering

An arbitrary "tooth-type" designation has not been developed. For discussion purposes, the nomenclature employed only refers to the illustration's number. This should be a temporary condition. Described tooth-types which are not illustrated are assigned a one-up numbering system with a "NYI" (not yet illustrated) prefix.

Collected Lots

General Description

Anterior and lateral teeth of both sexes have cuspidate crowns, in contrast to the typical globular design associated with most stingrays. The medial teeth have strong, lingually directed cusps, which are similar to the "typical" high-cusped male stingray tooth -- such as those from Dasyatis americana HILDEBRAND & SCHROEDER, 1928, D. sayi (LESUER, 1817) and D. sabina (LESUER, 1824). Unlike the cited examples, the labial face does not have strong enameloid ridges or a medial depression running the length of the cusp. In lateral teeth, the cusp is weaker and more upright. In lieu of a cusp, the posterior teeth have a prominent, laterally elongated, transverse crest which adjoins a strong transverse depression on the labial face. On the lingual face, the transverse crest has longitudinal ridges. Medial and lateral teeth have a weak depression on the labial face which is located at the juncture of the crown base and the cusp.

The labial face of all teeth have a pitted appearance which results from the depressions created by numerous small meandering enameloid ridges. No teeth have a "cutting edge" as in many shark or skate teeth. Rather, the acute angle of the transverse edge of the cusp and transverse crest have a serrate edge created by the numerous enameloid ridges.

As a dasyatid, there is a unique feature represented in these teeth -- the development of a second cusp. An incipient reflection of this characteristic can be seen in many teeth, usually as a longitudinal depression in the lingual face of the crown. Eight percent of the teeth, originating in medial and lateral positions, have a second cusp. These bicusped teeth appear sporadically within the dentition, and are present in a file of teeth which are otherwise single-cusped. Unlike the mobulids, the other family developing additional cusps, this bicuspidate condition in the pelagic stingray is not associated with the mesio-distal elongation of the crown.

Sex and the isolated Pelagic stingray tooth

The anterior and most lateral teeth, as presented in this study, can be ascribed to a particular sex with a strong degree of certainty. To a lesser extent and with less confidence, the posterior teeth could be grouped by sex. This may not be the case when the origin of the teeth is unknown. If teeth from a large male were intermixed with those of a small female, it is unlikely that any posterior, and possibly lateral, teeth could be segregated. Anterior teeth from the first few files may show sexual dimorphism.

I make the final comment from experience with the previously described dentition. Based on size, and prior to extensive tooth study, that dentition was thought to be from a large male. The teeth from that dentition were compared with the small (male) teeth collected from the aquarium. Although smaller in size, these shed teeth all had counterparts in the dentition. When improved tooth collecting techniques were developed, a new group of small teeth were identified -- they were clearly anterior male teeth, but were not in the dentition. Once photographs of the MBA ray dentitions became available, they were compared with the shed teeth and the studied dentition. It became readily apparent that the dentition was from a small female rather than a large male. It was only the first few files that had teeth sufficiently different to ascribe that difference to anything other than size.

Additional research may yield subtle morphological details which will allow teeth of unknown origin to be confidently ascribed to a particular sex. However, at the time of this writing, relative size, a very poor basis for identification, is the only characteristic available for most isolated teeth.

High-Cusped Teeth (Anterior)

• LARGE TEETH, probably shed by females.

Cuspal view	Specimen 54-C. hgt = 2.5, wid = 2.9, dep = 2.5 mm

• Type 54-C. These are one of the most common and identifiable of the pelagic stingray teeth. In the March 14 sample, 12 of 136 teeth were segregated as belonging to this type and 10 of those, were like the illustration. Even the sizes were consistent - WIDbc 3.0 (+/- 0.2) x DEPbc 2.0 (+/- 0.1) mm. The triangular cuspal profile is characteristic, and the labial depression is weak. There is a distinct labial flange, and the base of the crown, at the lateral angle, is high. The cuspal angle is rounded and approximately 90 degrees.

Cuspal view	Specimen 54-B. hgt = 2.2, wid = 2.8. dep = 2.0 mm

• Type 54-B. These teeth are similarly common but less easily identified -- their cuspal profile and size tends to vary. Viewed labially, the cusp is often skewed to one side or the other but the lateral profile remains stable. This tooth-type is characterized by its strong labial depression. As with 54-C teeth, there is a distinct labial flange and high lateral angle. The March 14th sample had examples (qty = 15) ranging from WIDbc 2.8 x DEPbc 2.0 to 3.9 x 2.5 mm. The cuspal angle is rounded, slightly more than 90 degrees and located lower than noted on 54-C teeth. A weak secondary cusp was observed on two specimens.

Specimen 58-A hgt = 3.0, wid = 3.7, dep = 2.6 mm.

• Type 58-A. The March 14th lot contained three teeth of this style. They are generally similar to 54-B but the labial depression is very weak and the cuspal angle, higher. These teeth were WIDbc 3.9 x DEPbc 2.8 and 3.4 x 2.0 mm in size.

Specimen 58-B hgt = 2.8, wid = 4.0, dep = 2.6 mm.

• Type 58-B. Similar to the preceding tooth-type, the March 14th lot contained three teeth of this style. They are also similar to 54-B but the cuspal angle is very sharp and less than 90 degrees. These teeth are WIDbc 4.0 x DEPbc 2.6, 3.9 x 2.3 and 2.9 x 2.2 mm in size. One example is bicuspidate.

Specimen 60-C hgt = 2.8, wid = 2.9, dep = 2.2 mm.

• Type 60-C (was NYI-1). These teeth (two examples) appear to be fall between 54-B and 54-D. They have a strong labial depression, the cuspal angle is rounded and obtuse, but the cusp remains lingually directed (but only slightly). In one example the cuspal angle is low and in the other, high. These teeth are (WIDbc x DEPbc) 3.0 x 2.1 and 3.0 x 2.4 mm in size.

• SMALL TEETH, probably shed by males.

Specimen 58-D hgt = 2.6, wid = 2.3, dep = 1.9 mm.

• Type 58-D. Quite similar to the 54-C tooth described above, these teeth are common (eleven in the March 14th sample) and generally triangular in shape. However, the cusps are usually skewed to some extent. Other than one tooth measuring 2.5 x 1.8 (which is similar to this design but not exact), their size range is relatively consistent (WIDbc x DEPbc) 2.3 (+/- 0.2) x 1.5 (+/- 0.1) mm. The labial flange is weak, cuspal angle obtuse and labial depression moderate.

• Not Yet Illustrated - NYI-3. In this style tooth represented by three examples, the lower labial face is broader and the cusp narrower -- a tear drop shape. The cusp is centered and the labial depression moderate. The cuspal angle is rounded, low and obtuse. The labial flange is strong and the crown base high at the lateral angle. The teeth measured WIDbc 2.4 x DEPbc 1.5 (+/- 0.1) mm.

Specimen 58-C. hgt = 2.0, wid = 2.6, dep = 1.6 mm

• Type 58-C. This tooth-type is a broader variation of NYI-3 but with a shorter cusp. The labial flange is mild, labial depression weak and the rim rises at the lateral angle. Ten teeth from the March 14th lot fell into this group. Between them there were differences in the cuspal angle which coincided with size.

  Six teeth have a cuspal angle which is rounded, obtuse and in a medium position. They measured (WIDbc x DEPbc) 2.6 x 1.7, 2.6 x 1.6, 2.4 x 1.5, 2.3 x 1.6, 2.3 x 1.4 and 2.2 x 1.4 mm. The larger of these teeth (illustrated) compares very well with upper teeth from files three and four in the studied dentition. Three teeth had a less rounded cuspal angle which was slightly higher and the cusp more lingually oriented. These teeth were 2.1 x 1.4 (+/- 0.1) in size. The last example measured 2.3 x 1.4 but had a cusp more similar to NYI-3. Another example is bicusped.

  Specimen 60-A. hgt = 1.9, wid = 2.1, dep = 1.6 mm

• Type 60-A (was NYI-4). Viewed labially, these teeth look similar to 58-C but with a lower cusp. Laterally however, the crown is upright with no pronounced lingually directed cusp, somewhat similar to the 54-E design. This style tooth was represented by five examples which measured WIDbc 1.9 (+/- 0.2) x DEPbc 1.2 (+/- 0.1) mm. The cuspal angle is sharp and obtuse, with no apparent labial flange.

Low-Cusped Teeth (Lateral)

Specimen 54-D. hgt = 2.8, wid = 3.5, dep = 2.3 mm

• Type 54-D. Viewed labially, these teeth have pointed crowns, but laterally, there is no obvious cusp -- the lateral profile is somewhat triangular. Ten teeth from the March 14th lot fell into this grouping. There is a strong labial depression which redirects the upper labial face and a rounded and obtuse lingual cusp angle which creates an upright, cusp-like transverse crest. Sizes of these teeth are not uniform, ranging from (WIDbc x DEPbc) 3.1 x 2.1 to 3.8 x 2.6 mm. (These large teeth were probably shed by females.) Three of these teeth had two cusps. In one specimen (0314-122), one cusp was labially directed (54-D) and the other, lingually (54-B).

Specimen 54-E. hgt = 2.0, wid = 2.8, dep = 2.1 mm

• Type 54-E. This tooth-type compares well with teeth found in the lower lateral position of the studied dentition. There is a transverse depression, labial flange and a moderately sharp cuspal angle which slightly obtuse. Three teeth from the March 14th sample have been ascribe to this type, they measured (WIDbc x DEPbc) 2.3 x 1.7 to 2.7 x 1.9 mm.
• NYI-6. Very similar to 54-E were five larger teeth: WIDbc 3.2 (+/- 0.1) x DEPbc 2.1 (+/- 0.2) mm. Besides their larger size, the labial flange was often weaker, the cuspal angle sharper, and transverse depression weaker. The cusp is low and lingually directed.

Specimen 55-B. hgt = 1.7, wid = 2.4, dep = 1.9 mm

• Type 55-B. Originally lumped as a single tooth-type, there now appears to be two represented by this design, one female (some upper teeth from the studied dentition look very much like these), and the other possibly male. The sizes vary greatly. The illustrated example is (WIDbc x DEPbc) 2.5 x 2.1 mm and the two similar teeth from the March 14th sample measure 3.4 x 2.2 and 3.0 x 2.1 mm. These teeth have a strong labial flange, a cuspal angle in a medial position (rounded and obtuse) and high lateral angle.
• NYI-5. Very similar to the 55-B design, were three other teeth from the March sample. In these teeth however, there is a sharp cuspal angle and the lingual face is more upright. (although the overall crown height is lower). These teeth measured 3.0 x 2.2, 2.6 x 2.0 and 2.3 x 1.7 mm.

Specimen 60-B. hgt = 1.5, wid = 2.6, dep = 1.5 mm

• Type 60-B (was NYI-10). Three teeth from the March 14th sample are broad and low crowned and initially might appear as posterior teeth. However, they were clearly cuspidate. Viewed laterally, the labially face gently slopes in a lingual direction with a concavity in the area of the transverse depression. The lingual face has an sharp and acute cuspal angle These teeth measured 2.6 x 1.4, 2.5 x 1.4 and 2.7 x 1.7 mm. (The later had two cusps.)

Non-Cuspidate Teeth (Posterior)

In the studied dentition, the upper posterior teeth were of the broad 54-D design and the lower teeth were similar to the 55-D tooth. Because of the variations in sizes within each group, it is likely that male and female teeth are represented within these groups.

Specimen 54-A. hgt = 2.1, wid = 2.5, dep = 2.2 mm

• Type 54-A. Only six specimens in the March sample correspond with the design as illustrated above. Viewed lingually, the labially face is concave and the lingual slopes labially with a rounded cuspal angle which is obtuse and in a median position. The lingual face above the cuspal angle is labially directed. The crown has little or no labial flange and the transverse crest is broad and straight. The WIDbc-DEPbc measurements range form 2.9 x 2.0 to 2.3 x 1.3 mm. A seventh tooth has broadly separated roots and measures 2.9 x 1.5 mm - it may be pathological.

• NYI-7. Three teeth are very similar to the 54-A design but have a sharper and less obtuse cuspal angle. This results in the upper lingual face being generally upright. These teeth's basal crown measurements were 2.8 x 2.0 (+/- 0.1) mm.

Specimen 58-E hgt = 1.9, wid = 2.7, dep = 2.0 mm.

• Type 58-E. Six other teeth are similar to the 54-A design but have a less concave labial face and a higher cuspal angle. These teeth fall into two distinct size (WIDbc-DEPbc) ranges: (two teeth) 2.6 x 1.7 & 2.5 x 1.8 and (four teeth) 2.0 x 1.3 (+/- 0.1) mm.

• NYI-9. Two teeth are similar to the 54-A design but have a less concave labial face and a low cuspal angle with a nearly upright, upper lingual face. These teeth measure 2.0 x 1.3 (+/- 0.1) mm.

Specimen 55-D. hgt = 1.5, wid = 2.1, dep = 1.6 mm

• Type 55-D. The March 14th sample included twenty-two teeth with this design. They represent some of the smaller teeth found, and likely originate in distal positions of the dental band. The WIDbc-DEPbc measurements are quite erratic. If they originated from dental bands of significantly different sizes (male and female), the graduation in sizes would be more logical. (Fourteen teeth ranged from 2.1 x 1.3 to 2.3 x 1.8 mm, and eight measured 2.3 x 1.4 to 2.8 x 2.1 mm.) The study of a male dentition could resolve this matter. In general, when viewed laterally, the labial face is concave, the transverse crest upright and the lingual face has a sharp cuspal angle which is moderately obtuse. A labial flange is generally lacking, and from a labial perspective, the crown appears neither cuspidate not pointed.

Bi-cuspidate Teeth

Since that time, a dentition was obtained which also reflected this characteristic. Because this is no longer deemed a singular event (although both MBA rays and the studied dentition were collected from a similar area and may reflect a characteristic of a localized population) only teeth which have two cusps (and not the incipient condition) are now being counted. In the 0314 sample, 13 teeth had a second cusp (2/54-B, 4/54-D, 3/54-E, 58-B, 58-C?, NYI-08 & 60-B).

Looking at the distribution of bicusped teeth (using the allocation-to-tooth-group methodology employed for the March 14 sample) within the dentition, nearly 25% of the lateral teeth display this condition while only 6% of the anterior and 3% of the posterior teeth display this characteristic. This could turn out to be a characteristic of lateral teeth only,

Specimen 55-A. hgt = 2.1, wid = 3.2, dep = 2.0 mm

Pathological Teeth

Specimen 55-C. hgt = 1.5, wid = 2.9, dep = 2.1 mm

Condition

Page revised July 31, 1997