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FLOWERS, FRUITS, AND POLLEN OF FLORISSANTIA, AN EXTINCT MALVALEAN GENUS FROM THE EOCENE AND OLIGOCENE OF WESTERN NORTH AMERICA
Author(s) -
Manchester Steven R.
Publication year - 1992
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.1002/j.1537-2197.1992.tb13689.x
Subject(s) - biology , pollen , genus , botany , perianth , pedicel , bract , eudicots , reticulate , disjunct , stamen , calyx , taxonomy (biology) , inflorescence , population , demography , sociology
Compressed flowers and fruits of Florissantia (Lesquereux) comb. nov. from the latest Eocene of Colorado and Montana and from the middle Eocene to early Oligocene of Oregon were reinvestigated using the type material and more recently collected specimens. Two additional species, Florissantia quilchenensis (Mathewes & Brooke) comb. nov. from the middle Eocene of British Columbia and Washington and F. ashwillii sp. nov. from the middle Eocene to early Oligocene of Oregon, are also recognized on the basis of differences in perianth and anther morphology. Florissantia flowers are borne on long (up to 3 cm) pedicels and possess a large (2.3‐5.3 cm diam), shallowly campanulate, five‐lobed, persistent gamosepalous calyx. The fertile parts include a superior, pentagonal ovary, a single style with five stigmas, and a cycle of five stamens with bifurcate filaments topped by stout anthers or half anthers. Pollen removed from the anthers is oblate, 20‐32 μ m equatorial diam, 3(‐4)‐colporate, with short colpi and reticulate ornamentation. Although formerly placed in Porana (Convolvulaceae) and Holmskioldia (Verbenaceae), the newly recognized characters of floral and pollen morphology demonstrate that the genus belongs within the Malvales as an extinct genus possessing features found today in Tiliaceae, Bombacaceae, and Sterculiaceae. Recognizing that there is much overlap among extant genera of these families, and that the circumscription of these families is in need of systematic revision, the fossil is tentatively placed in the Sterculiaceae. Florissantia flowers exhibit a syndrome of features suggestive of insect or bird pollination, while the fruits, provided with a large, persistent, membranous calyx, appear to be well adapted for wind dispersal. Dismissal of this and other purported verbenaceous fossils from the Verbenaceae casts doubt on the presence of Verbenaceae in the early Tertiary of North America.