Glandulocalyx upatoiensis, a fossil flower of Ericales (Actinidiaceae/Clethraceae) from the Late Cretaceous (Santonian) of Georgia, USA

Author(s)

Jürg Schönenberger, Maria von Balthazar, Masamichi Takahashi, Xianghui Xiao, Peter Crane, Patrick S. Herendeen

Abstract

† Background and Aims Ericales are a major group of extant asterid angiosperms that are well represented in the

Late Cretaceous fossil record, mainly by flowers, fruits and seeds. Exceptionally well preserved fossil flowers,

here described as Glandulocalyx upatoiensis gen. & sp. nov., from the Santonian of Georgia, USA, yield new

detailed evidence of floral structure in one of these early members of Ericales and provide a secure basis for comparison

with extant taxa.

† Methods The floral structure of several fossil specimens was studied by scanning electron microscopy (SEM),

light microscopy of microtome thin sections and synchrotron-radiation X-ray tomographic microscopy

(SRXTM). For direct comparisons with flowers of extant Ericales, selected floral features of Actinidiaceae

and Clethraceae were studied with SEM.

† Key Results Flowers of G. upatoiensis have five sepals with quincuncial aestivation, five free petals with quincuncial

aestivation, 20–28 stamens arranged in a single series, extrorse anther orientation in the bud, ventral

anther attachment and a tricarpellate, syncarpous ovary with three free styles and numerous small ovules on

axile, protruding-diffuse and pendant placentae. The calyx is characterized by a conspicuous indumentum of

large, densely arranged, multicellular and possibly glandular trichomes.

†Conclusions Comparison with extant taxa provides clear evidence for a relationship with core Ericales comprised

of the extant families Actinidiaceae, Roridulaceae, Sarraceniaceae, Clethraceae, Cyrillaceae and

Ericaceae. Within this group, the most marked similarities are with extant Actinidiaceae and, to a lesser

degree, with Clethraceae. More detailed analyses of the relationships of Glandulocalyx and other Ericales

from the Late Cretaceous will require an improved understanding of the morphological features that diagnose

particular extant groups defined on the basis of molecular data.

Organisation(s)

External organisation(s)

Niigata University, Argonne National Laboratory, Yale University, Chicago Botanic Garden

Journal

Annals of Botany

Volume

109

Pages

921-936

No. of pages

ISSN

0305-7364

DOI

https://doi.org/10.1093/aob/mcs009

Publication date

04-2012

Peer reviewed

Yes

Austrian Fields of Science 2012

106041 Structural biology

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