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Mechanisms underlying exceptional plant diversity across eastern Asia

Bickner, Maya [1], Herrera, Fabiany [1], Herendeen, Patrick [1], Shi, Gongle [3], Niiden, Ichinnorov [4], Crane, Peter [5].

Three New Early Cretaceous Seeds from Mongolia with Chlamydospermous Organization.

Three new types of lignified  and permineralized fossil seeds from the Early Cretaceous have been recovered from Mongolia and Inner Mongolia, China. The three morphotypes were all recovered as lignite mesofossils from the Tevshiin Govi Formation, and the first morphotype was also recovered as permineralized chert specimens from the Zhahanaoer Formation. The seeds have been studied using a combination of light microscopy, semi-destructive traditional sectioning and synchrotron radiation X-ray micro-tomography. The seeds are all chlamydospermous in organization, in which a sclerenchymatic seed envelope completely covers the integument that extends apically into an elongated micropyle. The seeds of the first morphotype are 4-6 mm long, 2-3.5 mm wide, subtly four angled in cross section, and obovate to fusiform in longitudinal section, with a collar-like structure supporting a long micropyle. This seed is unique in having a two-layered sclerenchymatic seed envelope, in which a smooth outer envelope layer covers a highly rugulate inner envelope layer. The seeds of the second morphotype are 4-6.5 mm long, 3-4 mm wide, ovoid to spherical, tapering at the apex into an extended micropyle. The seed envelope is covered in a thick cuticle, consisting of rectangular, longitudinally arranged cells covering a smooth sclerenchymatic seed envelope. We assign the third seed morphotype to the genus Problematospermum and provide new information on this enigmatic fossil plant. The new specimens, 3-4.5 mm long and 1-1.5 mm wide, are long elliptic, with short blunt processes, and a long micropyle at the apex. The new specimens demonstrate that the Problematospermum seed envelope has sutures that split apically into five to seven valves. The Mongolian specimens also provide new information on the orientation of these seeds on the parent plant. The three morphotypes are assigned to the assemblage of isolated mesofossils with chlamydospermous organization associated with the Bennettitales, Erdtmanithecales, and Gnetales. These seeds expand this group's known range into central Mongolia and add to the diversity of gymnosperms during this crucial time in plant evolution.

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1 - Chicago Botanic Garden, 1000 Lake Cook Road, Glencoe, IL, 60022, USA
2 - Chicago Botanic Garden, 1000 Lake Cook Road, Glencoe, IL, 60022, USA
3 - Nanjing Institute Of Geology And Palaeontology, Chinese Academy Of Sci, 39 East Beijing Road, Nanjing, 32, 210008, China
4 - Institute of Paleontology, Mongolian Academy of Sciences, Ulaanbaatar-15160, Mongolia
5 - Oak Spring Garden Foundation, Oak Spring, Upperville, VA, 20184, United States

none specified

Presentation Type: Colloquium Presentations
Session: C04, Mechanisms underlying exceptional plant diversity across eastern Asia
Location: /
Date: Tuesday, July 20th, 2021
Time: 12:45 PM(EDT)
Number: C04010
Abstract ID:238
Candidate for Awards:None

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