Problems related to the taxonomic placement of incompletely preserved amber fossils: transfer of the Paleogene liverwort Cylindrocolea dimorpha (Cephaloziellaceae) to the extant Odontoschisma sect. Iwatsukia (Cephaloziaceae)

Abstract

A revision of the Baltic and Bitterfeld amber fossilsassigned to Cylindrocolea dimorpha (Cephaloziellaceae) has yielded evidence of the presence ofmulticellular, bifid underleaves, which have not previously been reportedfor this species and conflict with the current circumscription of thefamily. We transfer the fossil species to Odontoschisma (sect. Iwatsukia) and propose the newcombination O. dimorpha of the Cephaloziaceae. Characteristics of the fossil include anoverall small size of the plant, entire-margined, bifid leaves andunderleaves, more or less equally thickened leaf cell walls, ventralbranching that includes stoloniform branches with reduced leaves, and thelack of a stem hyalodermis and gemmae. Placement of the fossil inCephaloziaceae profoundly affects divergence time estimates for liverwortsbased on DNA sequence variation with integrated information from the fossilrecord. Our reclassification concurs with hypotheses on the divergence timesof Cephaloziaceae derived from DNA sequence data that provide evidence of alate Early Cretaceous to early Eocene age of the Odontoschisma crown group and an originof O. sect. Iwatsukia in the Late Cretaceous to Oligocene.