In an attempt to identify Miocene stingray teeth recovered from the Pungo River (Miocene) and Yorktown (Miocene-Pliocene) sediments at Aurora (Beaufort County, NC -- aka Lee Creek), extant species are being studied. After cursory examinations of material available at the Smithsonian, it was determined that more intense analysis of a greater number of specimens was required.

The first opportunity was to study teeth shed by the pelagic stingray (D. violacea) with Henry Mollet and Scott Greenwald of the Monterey Bay Aquarium (MBA). A great deal of information was garned from this research, but D. violacea did not appear to be represented in the Lee Creek fauna.

Thanks to the efforts and contacts of Henry Mollet, a second extant Dasyatis species (which was a likely candidate for a Lee Creek fossil record) could be studied -- D. sabina, the Atlantic Stingray. In June 1997, Elena Amesbury of the University of Central Florida (Orlando) forwarded four dentitions. Peter Piermarini (University of Florida - Gainsville) then offered his assistance in providing additional dentitions.

Dasyatis sabina - (LESUER, 1824)

This is a small tropical ray from Florida and the Gulf of Mexico (known from Central America to the Chesapeake). It inhabits shallow coastal waters. Snelson et al (1988) indicates that males mature at 20 cm DW (max 32.6 cm/1.6 kg) and females 24 cm DW (max 37.0 cm/2.2 kg). The population studied by Peter Piermarini lives and breeds in Lake Jessup ( freshwater) of the St. Johns River in Florida. Kajiura & Tricas (1996, citing Cook 1994) note that they feed upon small benthic crustraceans (amphipods, mysids, isopods), polychaetes and invertebrates found in seagrass beds. During the summer months they feed upon calcified brittlestar disks.

Peter Piermarini (pers com) noted that the Lake Jesup population appears to have no seasonal shifts in diet. Stomach contents reveal a diet that is composed of viviparid gastropods, various insect larvae (Chironomids and mosquito pupae) and small crustataceans (definitely no brittle stars). Gastropod feet muscle and opercula are found in the gut, but the shell material is apparently spit out. See Peter Piermarini page at the Atlantic stingray

Dentition

The D. sabina dentition was traditionally viewed as having a crushing design in female specimens, and clutching in males. Kajiura & Tricas (1996) demonstrated that the species in fact had a crushing design, but in males, cuspidate teeth were present during mating season, giving them a seasonal, grasping dentition.

The wear patterns on the teeth of specimen ELA95-10.5 suggest that the dentition may serve a grinding function as well, at least on a seasonal basis. Terminology

Fig. 1 ELA95-3.2 D. sabina
female dentition, 54 mm width

As can be seen in figure 1, the occlusal surface of the upper tooth band is strongly depressed (concave) in the mesial position (which corresponds with the teeth termed anterior) and raised (convex) in the lateral. The lower tooth band matches this design by being raised in the mesial position and depressed in the lateral. The distal regions of upper and lower are level.

For initial discussion purposes, each (upper and lower) tooth band will be divided into three regions - mesial, lateral and distal. The mesial region will include 'symphyseal' and 'anterior' teeth, the lateral,' lateral' teeth and the distal, 'posterior' teeth. It is unknown at this time if the teeth from various tooth band regions will display sufficient odontological variations to be identified on an isolated tooth basis.

Prepared and studied specimens include:

Specimen IDSex Collected Location Disc
Width		Upr File
Formula		Lwr File
Formula
LJ-10/96 Male Oct. 96 Lake Jesup22.8 cm. 17-s-17 20-1:1-20
LJ-3-31-97 Male Mar 31, 97Lake Jesup 26.5 cm 19-s-19 damaged
ELA95-10.5 FemaleJun 7, 95 Lake Jesup37.0 cm 20-s-20 20-1:1-21
ELA95-3.2 FemaleFeb 16, 95Lake Jesup30.5 cm    
NOTE: The cleaning and curing process will cause the dentitions to assume a shape that may not be totally natural or become distorted. The fleshy padding between the dental band and the jaws will also be subject to shrinkage

Specimen No. ELA95-10.5

This is the dentition of a large (37 cm DW) female captured June 7, 1995 in Lake Jesup. The dentition when dried measured 73 mm in width. The upper tooth band is 37 mm in width and the lower, 34.5 mm.

Fig. 2 ELA95-10.5 D. sabina large female dentition, 73 mm width

Upper Tooth Band. The dental formula is 20-s-20, forty-one teeth. There is a symphyseal, the anterior teeth include file postions 1 - 6, the laterals 7 - 13 and the posteriors, 14 - 20. The symphyseal & anterior teeth [s, 1-6] are small (1.2 x 0.9 mm, meso-distal width x labio-lingual depth when noted) and less densely packed than the laterals. There are 10 - 12 rows present which includes two which appear to be in the process of being shed, and two sufficiently worn to be deemed 'functional'. The lateral teeth [7 - 13] are the largest in the band reaching 2.0 x 1.8 mm (file 10). There are 10 - 11 rows, with 1.5 rows in a shed position and 3.5 in a functional. Posterior teeth [14 - 20] have fewer rows (file 14 with 10 and 20 with 8) and gradually grow smaller distally, 1.4 x 0.8 mm in position (file) 20. In file position 14, three rows are functional with another in a shed position and in file 20, two are functional.

Lower Tooth Band. The dental formula is 20-1:1-21, forty-one teeth. The anterior teeth include postions 1 - 6, the laterals 7 - 13 and the posteriors, 14 - 20/21. (The demarcation between laterals and posteriors is currently rather subjective.) The anterior teeth [1-6] are large (1.8 x 1.2 mm, in file 3) and densely packed. There are 15 - 16 rows present which includes one or two which appear to be in the process of being shed, and four with enough wear to be deemed 'functional'. These functional teeth are worn sufficiently to have a flat occlusal surface and hexagonal shape -- giving teeth in these rows a myliobatoid-look (grinding pavement teeth). The lateral teeth [7 - 13] are small (1.2 x 1.0 mm in file 10). There are 11 - 14 rows, with one row in a shed position and two in a functional. Posterior teeth [14 - 20/21] have fewer rows (the most distal file has 8) and gradually grow smaller distally, 1.0 x 0.7 mm in the last file. There appears to be three fuctional rows.

Specimen No. ELA95-3.2

Specimen No. LJ-10/96 (Fig. 3)

This is the dentition of a (22.8 cm DW) male captured in October 1996 in Lake Jesup. The dentition when dried measured 33 mm in width. The mandibular cartilage was damaged during removal resulting in the loss of about 2 mm from the right side. The upper tooth band is 20 mm in width and the lower, 18.5 mm. This dentition reflects the seasonal dimorphism described by Kajiura & Tricas (1996). Within each file, there is an abrupt change in tooth morphology — the teeth become significantly more cuspidate lingually.

Fig. 3 LJ-10/96 D. sabina male 22.8 cm width

Upper Tooth Band (Fig. 4). The dental formula is 17-s-17, thirty-five teeth. There is a symphyseal, the anterior teeth include file postions 1 - 7, the laterals 8 - 14 and the posteriors, 15 - 17. The symphyseal & anterior teeth [s, 1-7] are high-cusped and small (c1.0 mm in width). There are seven rows present which appear to include three which are functional. In row five, the cusps become clearly larger. The lateral teeth [8 - 14] are the largest in the band (file 10) reaching c1.3 mm in width and low-cusped. There are seven rows, with 2.5 appearing to be functional. Begining in row four, the teeth have higher cusps. Posterior teeth [15 - 17] are small and non-cuspidate. Arranged in five rows, they gradually grow smaller distally (c0.8 mm in file 17). Two rows show evidence of being functional and a uspidate morphology appears in row three.

NOTE: The file breakpoints between tooth-types is an approximation only. The teeth are small and were observed in situ. The breakpoints were based on observable tooth structure and tooth band location. These may be revised in the future, but it is unlikely that they will vary by more than one file position. For the same reason, tooth measurements could not be reliably made and can be off by 0.2 mm. .

Fig. 4 LJ-10/96 D. sabina male, upper tooth band
Illustrated is the symphyseal, right hand files 1 - 16 and left hand files 1 - 12.
Anterior to top.

Lower Tooth Band (Fig. 5). The dental formula is 20-1:1-20 -- forty teeth. The anterior teeth include positions 1 - 7, the laterals 8 - 16 and the posteriors, 17 - 20. The anterior teeth [1-7] are high-cusped and the largest in the tooth band (width c1.0 in file 1 & c1.2 in file 4). There are 9 teeth in file 1 decreasing to 8 in file 7. One row is being shed, 2.5 appear functional and they become higher cusped in row 5. The lateral teeth [8 - 16] are smaller c1.0 mm in width) and are currently deemed non-cuspidate. There are seven rows (file 12), with three functional (may include teeth in a shed position). Teeth become cuspidate in row four. Posterior teeth [17 - 20] have fewer rows (the most distal file has 6) and gradually grow smaller distally (c0.7 mm in the last file). There appears to be three functional rows and teeth become cuspidate in row three or four.

Fig. 5 LJ-10/96 D. sabina male, lower tooth band

Specimen No.LJ-3-31-97

This is the dentition of a (26.5 cm DW) Lake Jesup male captured in March 1997. The right hand side of this dentition was severed during removal, but would have been of slightly wider than LJ-10/96 (c36 mm in width). The upper tooth band is 22 mm in width, but the lower cannot be determined. In this dentition, all rows contain high-cusped teeth. Within each row, there is an abrupt change in tooth morphology -- the teeth become significantly more cuspidate. Multiple rows are missing from the labial margin of the tooth bands (particularly the upper), this may possibly be the result of pectoral biting during mating.

Upper Tooth Band. The dental formula is 19-s-19, thirty-nine teeth (files). There is a symphyseal, the anterior teeth (subjectively) include file postions 1 -7, the laterals 8 - 12 and the posteriors, 13 - 19. The symphyseal & anterior teeth [s, 1-7] are high-cusped and small (c1.0 mm in width). The lateral teeth [8 - 12] are the largest in the band reaching 1.3 mm in width. Posterior teeth [15 - 17] are small and fully cuspidate.

Lower Tooth Band. Neither side of the tooth-band is complete -- row and file counts cannot be provided. It would be highly subjective to differentiate anterior teeth from laterals, however in files RH-14/LH-11, the tooth cusps become markedly lower, suggesting the begining of the posterior tooth-file groups.

A Fossil Record?

The D. sabina tooth design has not been noted in the Lee Creek Fauna (Miocene, North Carolina). However, odontologically-similar teeth are represented in the Sharktooth Hill Fauna (Miocene, California). Considering the current distribution of this species, and in the absence of connected Americas, there is no reason to fully discount this possibility.

References

Bigelow, H. B. & Schroeder, W., C., 1953. Fishes of the Western North Atlantic. Sawfishes, Guitarfishes. Skates and Rays. Memoires of the Sears Foundation for Marine Research, no. 1, part 2.
Kajiura, Stephan M. & Tricas, Timothy C., 1996. Seasonal dynamics of dental dimorphism in the Atlantic Stingray Dasyatis sabina. Journal of Experimental Biology, pp 2297-2306.
Snelson, F.F., Williams-Hooper, S.E. and Schmid, T.H., 1988. Reproduction and ecology of the Atlantic stingray, Dasyatis sabina, in Florida coastal lagoons. Copeia. pp 729 - 739