Known from skeletons as well as teeth, the sclerorhynchids are an extinct family of sawfishes from the Cretaceous of Europe, Africa, the Near East and Americas. Ptychotrygon likely had a similar distribution, with oral teeth (only) reported from Europe, North Africa and particularly, North America. Unlike other members of the family, only Manning (2006) attributes rostral denticles (spines) to this genus.¹ The design of the crown and root strongly point to Sclerorhynchidae as the proper family.

Many species have been described from Upper Cretaceous waters of eastern and interior North America, particularly Texas. Cappetta & Case (1975: 32-35) reported P. vermiculata CAPPETTA 1975 and erected P. cuspidata from the Late Cretaceous of New Jersey. Schwimmer (1986: 121 plate 1:f) depicts a specimen (Campanian, GA) of the P. vermiculata-design. Cappetta (1987:156-57) included in the NA inland sea: P. blainensis CASE 1978 from the Judith River of Montana and P. ledouxi CAPPETTA 1973 from the Carlile Shale of South Dakota. Welton and Farish (1993: 147-51) included in the Texas fauna: P. agujaensis MCNULTY & SLAUGHTER, 1972 (Campanian), P. hooveri MCNULTY & SLAUGHTER, 1972 (Cenomanian-Coniacian), P. slaughteri CAPPETTA & CASE 1975 (Cenomanian), P. texana (LERICHE 1940) (Maastrichtian), and P. triangularis (REUSS 1844) (Cenomanian-Maastrichtian). Case & Cappetta (1997: 150-51) included P. vermiculata as present in the Kemp Clay (Maastrichtian, TX) and erected P. winni for a second tooth-design they recognized. Hartstein et al (1999: 18) included P. vermiculata from the Severn Fm (Maastrichtian) of Maryland; from the illustration, it is difficult to see the characteristic multiple mesio-distal edges associated with P. vermiculata. Included herein as figure is a Severn example referred to as Ptychotrygon sp B which does not compare well with P. vermiculata. Neither Case (1979) nor Robb (1989) included Ptychotrygon in their North Carolina faunal lists.

The teeth of this genus are usually small (2 - 6 mm in width), laterally expanded with a transverse crest, strong labial visor and often bearing additional transverse ridges on the labial crown face. The roots are bilobate (triangular when viewed basally) with a nutrient groove, central foramen, and a lateral foramen on the lingual face of each lobe.

In 1998 I had the opportunity to collect and study some 175 Ptychotrygon teeth from the Black Creek sands of Lenoir Co., North Carolina. Although individual teeth would vary, largely because of tooth position (Fig. ) and possibly as a result of sex and age, most corresponded with the P. vermiculata design. Using these as an example, a moderately strong transverse crest is accompanied by two additional transverse ridges on the labial face and another, high on the lingual face. A strong labial visor is accompanied by a corresponding depression on the lingual face of the crown. In a median position, the occlusal surface of the visor has ornamentation, which appears as short, meandering enameloid ridges. On some teeth, small enameloid "bumps" may be present in the depressions created by the transverse ridges of the labial face. The roots are less than half the height of the crown, and each lobe is clearly triangular when viewed basally. The nutrient groove is strong and bears a large central pore. Viewed lingually, a lateral foramen is on each lobe.

Follow-up collecting (2007) of reworked Late Cretaceous (Peedee/Tar Heel Fm) material in Wayne Co., NC provided additional specimens with a greater diversity. One of these additional tooth-designs compared very well with P. cuspidata (Fig. ). This specimen has a high crown connected to the lateral margins with a typical transverse edge; atypically, a relatively sharp medial ridge extends to the center of the prominent labial visor. The lower portion of the labial crown face bears numerous enameloid ridges extending partially up the crown face or to the medial ridge. A third design, Ptychotrygon sp A (fig. & ) is represented by several teeth. It is differentiated from P. vermiculata by its lateral profile and less-ridged labial face; it lacks the lower ornamentation seen in P. cuspidata.

Footnotes

1.	Manning attributes to Ptychotrygon triangularis rostral spines similar to some of those referred to by others as Ischyrhiza avonicola.

Selected References

Cappetta, H., 1987. Chondrichthyes II. Mesozoic and Cenozoic Elasmobranchii. In: Handbook of Paleoichthyologie, vol. 3b, Gustav Fischer Verleg, Stuttgart, 193 pp.
Cappetta, H. 1975. Ptychotrygon vermiculata n. sp., sélacien nouveau du Campanien du New Jersey. Comptes Rendus Sommaires de la Société Géologique de France 17:164-166.
Cappetta, H. & Case, G., 1975. Contribution à l'étude des sélaciens du groupe Monmouth (Campanien - Maestrichtian) du New Jersey. Palaeontographica Abteilung A, 151:1-46.
Case, G., 1979. Cretaceous Selachians from the Peedee Formation (Late Maestrichtian) of Duplin County, North Carolina, Brimleyana, Vol 2, pp 77-89.
Case, G. and Cappetta, H.. 1997. A new selachian fauna from the late Maastrichtian of Texas. Münchener Geowissenschaften Abhandungen 34:131-189.
Hartstein, E., Decina, L. and Keil, R., 1999. A Late Cretaceous (Severn Formation) Vertebrate Assemblage from Bowie, Maryland. The Mosasaur, 6:17-23.
Manning, E., 2006. Late Campanian vertebrate fauna of the Frankstown site, Prentiss County, Mississippi; systematics, paleoecology, taphonomy, sequence stratigraphy. Unpub. PhD dissertation, Tulane Univ., New Orleans, xvii+419 p., 16 pls.
Robb, A., 1989. The Upper Cretaceous (Campanian, Black Creek Formation) Fossil Fish Fauna of Phoebus Landing, Bladen County, North Carolina, The Mosasaur, Vol 4, pp 75-92.
Schwimmer, D., 1986. Late Cretaceous fossils from the Blufftown Formation (Campanian) in western Georgia. The Mosasaur. Delaware Valley Paleontological Society. pp 109-119.
Welton, B. and Farish, R., 1993. The Collector's Guide to Fossil Sharks and Rays from the Cretaceous of Texas. Before Time, Texas. 204 pp.