Aulacomnium heterostichoides sp.nov., an Eocene moss from south central British Columbia

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Abstract
Aulacomnium heterostichoides Janssens, Horton, and Basinger is described as new from Eocene sediments located near Horsefly, B.C. It is characterized by spirally arranged, oblong leaves, which are slightly asymmetric by the unequal laminae in the lower one-third; irregularly, coarsely toothed upper margins with the teeth both multicellular and multiseriate; a strong costa, which ends near the apex; upper and basal laminal cells which are more or less isodiametric. These character states indicate a very close relationship to Aulacomnium heterostichum.Palynological studies indicate that Aulacomnium heterostichoides grew in a temperate, deciduous forest with species of Alnus, Carya, Pinns, Quercus, Taxodium, and Tilia, as well as other deciduous and coniferous trees. Extant populations of A. heterostichum commonly occur in a similar habitat along streams in the mesic, deciduous forests of eastern Asia and eastern United States.There is considerable fossil evidence which shows that vascular plants currently restricted to eastern Asia and eastern North America, occurred in the intervening areas across continental North America in Tertiary times. Our report of A. heterostichoides is the first indication, based on a fossil specimen, that bryophytes presently associated with the disjunct deciduous forests of eastern Asia and eastern North America were earlier associated with some elements of these forests in localities beyond the present range of such taxa.