DEVORE, MELANIE L.1*, KATHLEEN B. PIGG2, and STEPHEN J. MOUTON1. 1Department of Biological & Environmental Sciences, Georgia College & State University, Milledgeville, GA, 31062-0001 USA; 2Department of Plant Biology, Arizona State University, Box 871601, Tempe, AZ, 85287-1601 USA. - Permineralized fruit with malvalean affinities from the Late Paleocene Almont Flora, North Dakota.
The Almont flora of southwestern North Dakota occurs in silicified
shale that preserves morphological and anatomical details of fruits
and seeds. Among these remains we find a small multiloculate fruit
containing around 15 - 20 seeds, with a single seed per locule. Fruits
are 10.5 mm wide and 4.5 -5 mm high in transverse section and up to
around 13 mm long. Seeds are borne with their long axes parallel to
one another, and are separated by a distictive honeycomb-like pattern
of septa. Septa are formed by two adjacent layers of prominent
palisade cells. Seeds are flattened, ovoid, and triangular in section
with a rounded end and pointed apex. They have an outer layer of
somewhat elongate cells that parallel the surface of the seed, and
tend to change orientation toward the inside of the seed. This portion
of the seed coat is usually only partly preserved. An inner seed layer
forms a reticulate pattern on the surface of the silicified seed
casts. Based on comparisons of extant taxa, it appears that this fruit
type is most closely allied to the core Malvales (Bombacaceae,
Malvaceae, Sterculiaceae, and Tiliaceae). Of these families, the
Almont fruit compares most closely with Tiliaceae, in particular
because of the presence of single-seeded locules. The malvalean fruit
from Almont is of particular significance because of its similarity
with Carpolithus bowerbanki Reid & Chandler, an
anatomically preserved form based on a single specimen from the Lower
Eocene London Clay flora. Carpolithes bowerbanki is
similar to the Almont fruit in many features, but somewhat larger. The
Paleocene-Eocene was an interval of major faunal exchange across the
North Atlantic. The similarities between the Almont fruit and
Carpolithus bowerbanki strongly suggest that there were
also shared floristic elements.
Key words: Almont, Carpolithes bowerbanki, fossil fruit, Malvales, Paleocene, permineralization