New Early Cretaceous Seeds from Mongolia and Inner Mongolia, China, with Chlamydospermous Organization

Premise of research. Two new taxa of gymnosperm fossil seeds and new specimens of Problematospermum ovale have been recovered from the Early Cretaceous of Mongolia and Inner Mongolia, China. All were recovered as lignite mesofossils from Mongolia, and one, Bugdaevaea lignitica gen. et. sp. nov., was also recovered in permineralized chert from Inner Mongolia, China.Methodology. Fossils were studied using light microscopy, semidestructive traditional sectioning, cellulose acetate peels, and X-ray microtomography.Pivotal results. Bugdaevaea lignitica is 4–6 mm long, slightly four angled in cross section, and obovate to fusiform in longitudinal section, with a collar that supports a long micropyle. Bugdaevaea lignitica has a two-layered seed envelope, in which a smooth outer layer covers a rugulate sclerenchymatic inner envelope. Nosovaea striata gen. et sp. nov. is 4–6.5 mm long and ovoid to spherical and tapers at the apex into an extended micropyle. The seed envelope has a thick cuticle covering a smooth sclerenchymatic seed envelope. Newly discovered specimens of P. ovale are 3–4.5 mm long and narrowly elliptical, with short, blunt ridges and a long micropyle.Conclusions. All three seed taxa are chlamydospermous in organization, with a seed envelope completely covering the integument except for the elongated micropylar projection. Specimens of P. ovale demonstrate that the seed envelope has longitudinal sutures and splits apically into five to seven valves. They also clarify the orientation of these seeds on the parent plant. The three seed species are structurally similar to the diverse chlamydospermous seeds previously treated as the Bennettitales-Erdtmanithecales-Gnetales group. The discoveries from Mongolia and China show that seeds of this kind were present in Early Cretaceous floras from central and eastern Asia and contribute further information on the diversity of a key group of extinct seed plants at a critical time in plant evolution.