Monographs Details: Calliergon richardsonii (Mitt.) Kindb.
Authority: Buck, William R. 1987. Bryostephane Steereana: A Collection of Bryological Papers Presented to William Campbell Steere On The Occasion of His 80th Birthday. Mem. New York Bot. Gard. 45: 1-749.
Discussion:Two well preserved leafy plant apices and two isolated leaves, 1.45-1.56 m. The name Calliergon richardsonii is used provisionally for the fossils because the leaves are longer and narrower than is typical of most extant populations of that species I have studied. The shortness ofthe costa mles out C. cordifolium (Hedw.) Kindb. and C. giganteum (Schimp.) Kindb. Howard Crum (in litt.) suggested that the fossils were similar in leaf shape to Calliergidium pseudostramineum (C. Müll.) Grout. They are a good match for what Janssens and Glaser (1986) illustrated as Calliergon aftonianum Steere, which is based on Pleistocene fossils from Iowa. Kuc (1974) indicated that intermediate forms connect C aftonianum and C. richardsonii, although he maintained C. aftonianum as a species. Janssens and Glaser (1986) reported the discovery of extant populations of C aftonianum in highly shaded fen margin habitats in the Red Lake peatland, Minnesota. I have recently seen fossils referable to this narrow leaved form of C richardsonii (=C. aftonianum?) from sediments radiocarbon dated at 11,400 ± 100 yr B.P. at the Lamb Site, Genesee County, New York. Fig. 5a, b.