Title: Two early eudicot fossil flowers from the Kamikitaba assemblage (Coniacian, Late Cretaceous) in northeastern Japan

Abstract

Two new fossil taxa referable to the basal eudicot grade are described from the Kamikitaba locality (ca. 89 MYBP, early Coniacian: Late Cretaceous) in the Ashizawa Formation (Asamigawa Member) of Futaba Group in northeastern Japan. These charcoalified mesofossils exhibit well-preserved three-dimensional structure and were analyzed using synchrotron-radiation X-ray microtomography (SRXTM) at the Advanced Photon Source (APS) to document the composition and internal structure. Cathiaria japonica sp. nov. is represented by infructescence segments that consist of an axis bearing three to four fruits. The capsular fruits are sessile and dehiscent and consist of a gynoecium subtended by a bract. No perianth parts are present. The gynoecium is monocarpellate containing two pendulous seeds. The carpel is ascidiate in the lower half and conduplicate in the upper part, style is deflected abaxially with a dorsiventral suture and a large, obliquely decurrent stigma. Pollen grains are tricolpate with a reticulate exine. The morphological features of Cathiaria are consistent with an assignment to the Buxaceae s. l. (including Didymelaceae). Archaeostella verticillata gen. et sp. nov. is represented by flowers that are small, actinomorphic, pedicellate, bisexual, semi-inferior, and multicarpellate. The floral receptacle is cup shaped with a perigynous perianth consisting of several tepals inserted around themore » rim. The androecium comprises ca. 120 stamens with clear differentiation into anther and filament. The anthers are basifixed and tetrasporangiate. The gynoecium consists of a whorl of ten conduplicate, laterally connate but distally distinct carpels with a conspicuous dorsal bulge, including a central cavity. The styles are short, becoming recurved with a ventrally decurrent stigma. The fruit type is a follicle. Seeds are ca. 10 per carpel, marginal, pendulous from the broad, oblique summit of the locule. Seeds are small, spindle-shaped, with a chalazal extension, Pollen grains are tricolpate with a reticulate exine pattern, suggesting a relationship to eudicots. The morphological features of Archaeostella indicate a possible relationship to Trochodendraceae in the basal grade of eudicots, although it is uncertain if the anther thecae open by longitudinal slits as in extant Trochodendron. The fossil currently provides the earliest record of the family and documents the presence of Trochodendraceae in eastern Eurasia during the middle part of the Late Cretaceous. Furthermore, the recovery of Cathiaria japonica and Archaeostella verticillata from the Kamikitaba locality suggests that the basal eudicot families Trochodendraceae and Buxaceae s. l. (including Didymelaceae) were differentiated and distributed in eastern Eurasia area during the Late Cretaceous.« less

Authors:

Takahashi, Masamichi ^[1]; Herendeen, Patrick S. ^[2]; Xiao, Xianghui ^[3]

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+ Show Author Affiliations

1. Niigata Univ., Niigata (Japan)
2. Chicago Botanic Garden, Glencoe, IL (United States)
3. Advanced Photon Source, Argonne, IL (United States)

Publication Date:

Thu May 11 00:00:00 EDT 2017

Research Org.:

Argonne National Lab. (ANL), Argonne, IL (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES); National Science Foundation (NSF); Japan Society for the Promotion of Science (JSPS)

OSTI Identifier:

1417890

Grant/Contract Number:  

AC02-06CH11357

Resource Type:

Accepted Manuscript

Journal Name:

Journal of Plant Research

Additional Journal Information:

Journal Volume: 130; Journal Issue: 5; Related Information: Note: An erratum for this article is available at https://doi.org/10.1007/s10265-017-0957-x; Journal ID: ISSN 0918-9440

Publisher:

The Botanical Society of Japan and Springer Japan

Country of Publication:

United States

Language:

English

Subject:

59 BASIC BIOLOGICAL SCIENCES; 60 APPLIED LIFE SCIENCES; Angiosperms; Archaestella verticillatus; Cathiaria japonica; Futaba group; Japan; Kamikitaba assemblage; Coniacian; Cretaceous; Buxaceae s. l.; Mesofossil; Synchrotoron-radiation X-ray microtomography (SRXTM); Trochodendraceae