In addition to the dasyatoids and myliobatoids presented in the previous parts of this series, the mobuloids (devil rays) represent the third superfamily of the order Myliobatiformes to appear in the Lee Creek fossil record.

Cappetta (1987) traces the devil rays back to the Upper Paleocene. Like other members of the order, the mobuloids have broad, well-developed pectoral fins, in certain species, a stinging spine, and a whip-like tail. Unlike the others, the devil rays have large cephalic lobes which create mobile peribuccal fins which direct food into the mouth. They feed on small pelagic organisms -- schooling fish and planktonic crustaceans. Not needing a grinding dentition, there are numerous small, and often very poorly developed teeth. Cappetta indicates that they appear to have been derived from the rhinopterids which might best be illustrated by the teeth of Plinthicus (a common genus from the mine) or better, the Eocene genus Burnhamia. In Manta, and certain species of Mobula, the teeth are peg-like.

In general, the mobulids represent small to very large rays of subtropical and tropical waters. They are planktonic feeders that often school. Although single-cusped teeth are usually bilobate, they have polyaulacorhizous roots which are most evident in those teeth which are mesio-distally elongated.

Potential Lee Creek Devil Rays

The Pungo River Formation is thought to have been a subtropical environment and the Yorktown, warm temperate. Devil rays are a very common element of the batoid fauna in the Pungo River and to a lesser extent, the Yorktown, which corresponds well with their current warm water preference.

Cappetta (1987) includes Archaeomanta and Burnhamia as Upper Paleocene - Middle Eocene genera, Manta as Lower Miocene to recent, Mobula as Lower Oligocene to recent and Plinthicus as Lower to Middle Miocene Included were the species Manta melanyae CASE, 1980 from the Lower Miocene of North Carolina, Mobula loupianensis CAPPETTA, 1970 from the lower and Middle Miocene of Europe and M. pectinata CAPPETTA, 1970 to the Middle Miocene of France.

Notarbartolo di Sciara (1987) did an extensive revisionary study of the genus Mobula and concluded that there were nine extant species, largely based on soft tissue. Candidates for Lee Creek include: Mobula hypostoma RAFINESQUE, 1810 , possibly the eastern Atlantic species M. mobular (BONNATERRE, 1788) , Ceratobatis robertsii BOULENGER, 1897 (deemed synonymous with M. hypostoma) and several species that are known from the eastern Atlantic: M. rochebrunei (VAILLANT, 1879), M. thurstoni (LLOYD, 1908), M. kuhlii (VALENCIENNES in Müller & Henle, 1841), and M. tarapacana (PHILIPPI, 1892). Unlike most studies of living batoids employed in this research, this work provides excellent detail of tooth morphology

What's in a family Carroll (1988) placed Burnhamia, Eomanta, Paramobula and Mobula into the family MOBULIDAE, and Plinthicus into RHINOPTERIDAE. Cappetta (1970 & '87) put Paramobula and Eomanta into the genus Manta, included Ceratobatis with Mobula, added Archaeomanta and grouped all in MOBULIDAE. Regarding Plinthicus, Cappetta noted that the high crowns and lack of occlusal surface wear definitely suggests a ray more similar to the mobulids than the rhinopterids.

Lee Creek Devil Ray Teeth

As a percentage of the non-myliobatoid ray teeth recovered, devil ray teeth are significantly more common in the Pungo River (50%) than the Yorktown (22%) tailings of the mine, possibly reflecting a greater temperature sensitivity than the other rays.

To obtain specimens, the best method would be to sieve tailing samples directly from the mine. The dark brown phosphatic sands are particularly rich with these teeth. They have been obtained in lesser abundance from the upper Pungo River and lowest Yorktown units. The finer material from Blount Crossroads produces some, but due to their small size, not in the abundance of the mine's.

Mobula cf loupianensis CAPPETTA, 1970

As was documented by Notarbartolo di Sciara, Mobula teeth are highly variable in shape, depending on age, tooth position, sex and variability between individuals. I originally applied my standard numbering convention to these teeth and came up with several apparently distinct types. As research continued, it became apparent that most of the teeth likely represented tooth position and/or gender differences of a single species. These groups, termed Type "D" and "N", are illustrated below.

D-Type Teeth. (Figures 1 & 4) Working the DPW material, I had found few of these teeth, but as sand from the mine was processed, these became very common. Having first found an illustration in Cappetta (1987) which pointing to the genus, I studied M. hypostoma material at the Smithsonian and concluded that those grouped as Type "N" were likely the female counterparts of Type "D" (shape, size and relative abundance). The fossil teeth, however, remained different from the teeth in extant species. I was inclined to view them as M. cf hypostoma until reading Cappetta (1970), wherein he describes a then new species from the Miocene of France, M. loupianensis. The similarity was striking -- his illustration strongly resembled the tooth in figure 3.

Male D-type teeth tend to have distinct lateral cusplets and elongated medial cusp(s). They have a clear depression in the lower labial crown face which accommodates the tooth anterior to it.

N-Type Teeth. (Figures 2 & 3) Unlike the male teeth, N-type teeth (female) tend to have cusps which are broader, merging with and weakening the impact of the lateral cusps. As with their male counterparts, the teeth usually appear bilobate until a second central cusp "appears."

Fig. 1 Type "D5" 96-JAB-TGA-433-S25 hgt = 1.8 wid = 1.8 mm

Fig. 2 Type "N2" 96-JAB-TGA-432-S10 hgt = 1.6 wid = 1.8 mm

Fig. 31 Type "N4" 95-JAB-TGA-778-S40 hgt = 1.2 wid = 2.3 mm

Fig. 4 Type "D7" 96-JAB-TGA-391-S09 hgt = 1.5 wid = 1.6 mm

Mobula cf loupianensis

Plinthicus cf stenodon COPE 1869

Like most Lee Creek visitors, I started as a surface collector -- walking the mine and picking up what I "saw." Looking down at the tailings, Plinthicus teeth usually appeared as broken myliobatoid teeth -- this proved to be an excellent example of "you find what you're looking for." When I first saw an illustration in Cappetta (1987), I knew I'd been passing over many of these teeth; but looking through my Lee Creek material, I managed to find a few examples. In subsequent visits to the mine, I found and retained numerous examples of them.

U-Type Teeth. The species appears to have had a rhinopterid-type dentition with multiple, weakly-interlocking columns of teeth. Most striking in these teeth is the 45-degree angle of recline seen in lateral profile. In occlusal view (figure 38, second from right), the hexagonal myliobatoid shape can be seen. However, these teeth are labio-lingually compressed and very high (relative to the other dimensions).

The most common are those illustrated in figure 5. Termed Type "U2", these are the laterally shortened variation with about eight (range 7 to 9) root loblets. Next most common are the more elongated teeth ("U3") with 12 (range 11 to 14) loblets. The propensity for breakage is unknown, but the elongated teeth ("U4") with about 20 loblets appear less common. The specimen illustrated in figure 6 is the only complete elongated specimen I've collected so far.

A mesio-distal slope of the occlusal face is pronounced only in some U2-type teeth, suggesting a more lateral position. The only example of a true lateral tooth was provided by Becky Hyne and is shown in figure 7.

Fig 5. Type "U2" 96-JAB-TGA-174-B, width = 9.3 mm

Plinthicus stenodon Fig 7. (left) Type "U6" 9X-BH-TGA-61, width = 12.0 mm Fig 6. (right) Type "U4" 96-JAB-TGA-174-E, width = 20.0 mm

Paramobula fragilis (CAPPETTA 1970)

The teeth from this ray are indeed fragile -- of the dozens collected by the author, none have been complete. They appear regularly when collecting the dark brown sands of the Pungo River Marl. Cappetta originally placed these teeth in the genus Manta, then concluded they were not, preferring Mobula. Pfeil (1981) erected Paramobula for these teeth, and its usage seems appropriate.

Fig. 8 - Paramobula fragilis — 97-JAB-TGA-563B height 3.3, width 7.2 mm

Manta hynei BOURDON 1999

In September 1996, I collected a low Yorktown sample that produced my first Isistius teeth. More noteworthy for me was a small (3 mm in height), peg-like tooth. I noticed it only because I'd been looking for that particular shape for months. The crown and root stem is like those of Manta birostris as illustrated in Bigelow & Schroeder (1953). Cappetta's (1987) illustration shows a similar tooth with a lingually placed foramen and a bulbous root which lacks a nutrient groove.

Notarbartolo di Sciara (1987) provided a photo of a Mobula japanica tooth which is also peg-shaped and has a single, deep nutrient groove. Although its current distribution does not include the Atlantic, that author refers to the M. mobular dentition as similar. These teeth, however, have lateral cusps which are not evident in the Lee Creek specimen.

Fig. 9 - - Manta hynei 96-JAB-TGA-174-B, height = 3.0 mm

Mobulid Comments

Since I was unable to find any references to either Mobula or Manta at Lee Creek, the February 1997 issue of the New Jersey Paleontological Society Paleontograph may be the first documentation of their presence. The evidence is overwhelming for Mobula. M. cf loupianensis and Plinthicus stenodon teeth account for the vast majority of mobuloid material from the mine. The mine, however, holds more secrets, particularly of this family.