Cupressaceae conifers from the early cretaceous of Mongolia

Premise of research. The two living species of Cunninghamia form a clade that is sister to the rest of the Cupressaceae sensu lato, within which the monotypic extant genus Taiwania is sister to all Cupressaceae except Cunninghamia. Seed cones of both Cunninghamia and Taiwania bear helically arranged bract-scale complexes, but a free ovuliferous scale is present only in Cunninghamia. Here, we describe two new genera of fossil seed cones similar to those of Cunninghamia and Taiwania. Methodology. Early Cretaceous (Aptian-Albian) bulk lignite samples collected from the Tevshiin Govi locality were disaggregated in water, cleaned with hydrochloric and hydrofluoric acids, washed, and dried in air. Pivotal results. Pentakonos gen. nov. has seed cones that are up to 7 mm long with ca. 25-30 helically arranged, papery bract-scale complexes that have minute teeth. Adaxially, the free tip of the membranous ovuliferous scale is denticulate, and the scale bears five small, thin-winged seeds. Pentakonos adds to the diverse Cunninghamia-like seed cones known from the early fossil record of Cupressaceae. Seed cones of Stutzeliastrobus gen. nov. are terminal and single on leafy shoots with helically arranged falcate scale leaves. Seed cones are up to 32 mm long with ca. 30-70 helically arranged woody bract-scale complexes that lack a conspicuous, free ovuliferous scale. Morphological features of Stutzeliastrobus suggest a relationship with Taiwania, but the bract-scale complexes bear up to four inverted winged seeds rather than the two commonly seen in living Taiwania. Conclusions. Together with previously described fossils, Pentakonos and Stutzeliastrobus provide additional evidence that both Cunninghamia-like and Taiwania-like plants were important elements in the early diversification of the Cupressaceae s.l. A morphological cladistic analysis of the phylogenetic position of Pentakonos and Stutzeliastrobus suggests that an expanded cunninghamioid clade followed by Stutzeliastrobus are the successive sister groups to all other extant Cupressaceae.