THE AQUATIC ANGIOSPERM TRAPAGO-ANGULATA FROM THE UPPER CRETACEOUS (MAASTRICHTIAN) ST-MARY-RIVER FORMATION OF SOUTHERN ALBERTA

A floating aquatic dicot with leaves assignable to Trapago angulata ha s been characterized from Upper Cretaceous (Maastrichtian) deposits of the St. Mary River Formation in southern Alberta, Canada. Reconstruct ion of the plant is based on nearly 500 specimens of various isolated and attached organs. Prominent floating rosettes of leaves were interc onnected by submerged horizontal rhizomes with a distinct, crenulate s urface and formed dense mars at the surfaces of small freshwater ponds . At least eight different leaf morphologies were produced. Rosettes b ore opposite pairs of simple leaves and compound leaves with three, fi ve, seven, nine, and possibly 11 leaflets. Highly dissected, submerged leaves of differing morphologies occur on rosette-bearing axes and rh izomes. Paired bud scales at the nodes of the crenulate rhizomes subte nd both rhizome leaves and elongate, branched roots. Solitary flowers on long pedicels are attached in the axils of compound leaves. These r emains are compared to those described as Quereuxia angulata (Newberry ) Kryshtofovich from Russia, and extant Trapa L. Specimens from Russia , while showing leaves of morphology similar to that of T. angulata, d iffer in growth and branching pattern, supporting the interpretation t hat they are indeed different genera. Although Trapago has commonly be en placed in the Trapaceae, the similarities between extant Trapa and Trapago could be attributed to convergence, and the familial affinitie s of the fossil remain uncertain.