Northeastern (46th Annual) and North-Central (45th Annual) Joint Meeting (20–22 March 2011)

Paper No. 6
Presentation Time: 9:15 AM


WALKOWICZ, Joseph, Earth & Planetary Sciences Department, Northwestern University, 1927 Orrington Ave, Seabury H112, Evanston, IL 60201 and PLOTNICK, Roy E., Earth and Environmental Sciences, University of Illinois at Chicago, 845 W. Taylor St, Chicago, IL 60607,

Eurypterids first appear in the early Late Ordovician (Tetlie 2007). The best known Ordovician eurypterid is the large (at least 50 cm long) and spectacular Megalograptus from the Cincinnatian of Ohio (Caster & Kjellesvig-Waering, 1964). Megalograptus possesses a number of unusual and apparently derived features, including a tripartite telson and frontal appendages bearing long spines. Fragments assignable to Megalograptus were described by Shuler (1915) from the Bays Formation of Walker Mountain, Virginia. We describe new material of Megalograptus from the Upper Ordovician Martinsburg Formation at Fagg, Virginia. The eurypterids are in fine grained clastics with common bivalves, gastropods, and Lingula, interpreted as representing shallow shelf conditions. Although fragmentary, the material is diagnostic of Megalograptus. Identifiable fragments include the telson, cercal blade, postabdominal segments, coxa, and the distal portion of a swimming leg. There are also isolated scraps of integument with characteristic ornamentation, possibly representing portions of a tergite. The Ordovician record of eurypterids is still extremely spotty; the occurrence of Megalograptus in typical marine faunas in both Ohio and Virginia suggest that eurypterids may have been more widespread in that period than previously recognized.