2 NEW FOSSIL FLOWERS OF MAGNOLIID AFFINITY FROM THE LATE CRETACEOUS OF NEW-JERSEY

Citation
Wl. Crepet et Kc. Nixon, 2 NEW FOSSIL FLOWERS OF MAGNOLIID AFFINITY FROM THE LATE CRETACEOUS OF NEW-JERSEY, American journal of botany, 85(9), 1998, pp. 1273-1288
Citations number
44
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Plant Sciences
Journal title
ISSN journal
0002-9122
Volume
85
Issue
9
Year of publication
1998
Pages
1273 - 1288
Database
ISI
SICI code
0002-9122(1998)85:9<1273:2NFFOM>2.0.ZU;2-R
Abstract
Two taxa of cupulate magnoliid fossil flowers, Cronquistiflora and Det rusandra, are described from the Late Cretaceous (Turonian, similar to 90 million years before present [MYBP]) Raritan (or lower Magothy) Fo rmation of New Jersey. The fossil taxa are represented by flowers at v arious stages of development, associated fragments of cup-shaped flora l receptacles with attached anthers, and isolated anthers. Both taxa h ave laminar stamens with adaxial thecae and valvate dehiscence. Pollen is boat-shaped and foveolate in anthers associated with Cronquistiflo ra and spherical with reticulate ornamentation in Detrusandra. Cup-sha ped receptacles are externally bracteose in both taxa. The receptacle of Cronquistiflora is broader than the campanulate one of Detrusandra. Cronquistiflora also has more carpels (similar to 50 in a spiral vs. similar to 5 in a whorl or tight spiral). In Detrusandra the carpels a re surrounded by dorsiventrally flattened structures (pistillodes?) th at are remote from the attachment of the stamens near the distal rim o f the receptacular cupule. Detrusandra stigmas are rounded and bilobed , while those of Cronquistiflora, although bilateral in symmetry, are somewhat peltate. The fossil taxa share prominent characters with exta nt cupulate magnoliids (e.g., Eupomatia, Calycanthus), but also share characters with other magnoliids including Winteraceae. These fossils represent taxa that are character mosaics relative to currently recogn ized families. Inclusion of these fossils in existing data matrices an d ensuing phylogenetic analyses effect changes in tree topologies cons istent with their mosaicism relative to modern taxa. But such analyses do not definitively demonstrate the affinities of the fossils other t han illustrating that these fossils are generalized magnoliids. Additi onal analysis of modern and fossil magnoliids is necessary to fully ap preciate the phylogenetic significance and positions of these fossil t axa. However, the results of the phylogenetic analyses do introduce th e possibility that extinct taxa of Magnoliales with cupulate floral re ceptacles were transitional between basal angiosperms and those with t ricolpate pollen. The fossils provide insights into the timing of evol ution of character complexes now associated with coleopteran pollinati on.