William L. Crepet

A reevaluation of seed plant phylogeny

Seed plant phylogeny is evaluated using a data set of 46 terminals (taxa) and 103 morphological and anatomical characters. Cladistic analyses using the criterion of parsimony were performed on the complete data set as well as on subsets of the data, e.g., excluding fossils and/or combining various complex taxa into single terminals. The results support the placement of the cycads as the sister group of a monophyletic group that includes several fossil «seed ferns» as well as extant Ginkgo, conifers, gnetopsids, and angiosperms. When fossils were included, Bennettitales (cycadeoids) were part of an «anthophyte» clade that included gnetopsids and angiosperms. Pentoxylon was a sister taxon to the core anthophyte clade, in some, but not all, of the most parsimonious trees

Fossil evidence and phylogeny: the age of major angiosperm clades based on mesofossil and macrofossil evidence from Cretaceous deposits.

The fossil record has played an important role in the history of evolutionary thought, has aided the determination of key relationships through mosaics, and has allowed an assessment of a number of ecological hypotheses. Nonetheless, expectations that it might accurately and precisely mirror the progression of taxa through time seem optimistic in light of the many factors potentially interfering with uniform preservation. In view of these limitations, attempts to use the fossil record to corroborate phylogenetic hypotheses based on extensive comparisons among extant taxa may be misplaced. Instead we suggest a method-minimum age node mapping-for combining reliable fossil evidence with hypotheses of phylogeny. We use this methodology in conjunction with a phylogeny for angiosperms to assess timing in the history of major angiosperm clades. This method places many clades both with and without fossil records in temporal perspective, reveals discrepancies among clades in propensities for preservation, and raises some interesting questions about angiosperm evolution. By providing a context for understanding the gaps in the angiosperm fossil record this technique lends credibility and support to the remainder of the angiosperm record and to its applications in understanding a variety of aspects of angiosperm history. In effect, this methodology empowers the fossil record.

Fossil Clusiaceae from the late Cretaceous (Turonian) of New Jersey and implications regarding the history of bee pollination.

The Turonian flora from Sayreville New Jersey includes one of the worlds most diverse assemblages of Cretaceous angiosperm flowers. This flora is made even more interesting by its association with a large insect fauna that is preserved by charcoalification as well as in amber. Floral diversity includes numerous representatives of Magnoliidae, Hamamelididae, Rosidae, Dilleniidae, and Asteridae (Ericales sensu lato). Included are hypogynous, five-merous flowers with uniseriate hairs on the pedicels and stamens in bundles most frequently borne opposite the petals. There is considerable variation in filament length, and some filaments are branched. On some anthers, strands of residue, suggesting the former presence of a liquid of unknown nature, partially occlude the apparent zone of dehiscence. In other cases, open anthers are fully occluded by an amorphous substance. Pollen is rarely found associated with anthers, but is common on stigmatic surfaces. Pollen is prolate and tricolporate with reticulate micromorphology. The superior syncarpous ovary is five-carpellate with axile/intruded parietal placentation and numerous anatropous ovules/carpel. Ovary partitions have closely spaced, parallel ascending channels (secretory canals?), and there are apparent secretory canals/cavities in receptacles, sepals, and petals. Individual stigmas are cuneiform with a central groove and eccentrically peltate. Styles are short and fused. In aggregate, the stigmas form a secondarily peltate stigma. Seeds have a reticulate sculpture pattern, a pronounced raphe, and funicular arils with sculpture similar to the seeds. Phylogenetic analyses of several data matrices of extant taxa place this fossil in a monophyletic group with the modern genera Garcinia and Clusia within the Clusiaceae. As such, these fossils represent the earliest fossil evidence of the family Clusiaceae. Some modern Clusiaceae are notable, in particular, for their close relationship with meliponine and other highly derived bee pollinators; the fossil flowers share several characters that suggest a similar mode of pollination. This possibility is consistent with other floral and insect data from the same locality.

Timing in the evolution of derived floral characters: upper cretaceous (turonian) taxa with tricolpate and tricolpate-derived pollen

Abstract Various hypotheses that seek to explain the rich species diversity of angiosperms relative to other seed plants are briefly mentioned or reviewed. Of these, the subset that relates angiosperm diversity in some way to the relationship between angiosperms and insects, particularly anthophilous insects, is here the object of attention. Specifically, I address and reject the possibility that the relationship between angiosperm diversification and insects, particularly those demonstrating a preference for flowers with derived floral characteristics associated with insect pollination, may be ruled out because of asynchronous patterns of diversification in the fossil record. New data on floral structure from the Turonian of the Atlantic Coastal Plain reveal a surprising diversity of floral characters in taxa bearing tricolpate and tricolporate-derived pollen. The characters and taxa that appear in these Turonian sediments suggest that rather specific modes of insect pollination, perhaps involving highly derived insect pollinators, already existed at 90 Ma. Given the observed rate of diversification of angiosperms during that time and the pattern of evolution in insects, including what can be inferred about the history of the Apidae, these new floral data suggest that hypotheses relating angiosperm diversity to highly specific pollinators are still valid in the context of fossil evidence. Even so, consistency with fossil evidence is not necessarily proof of these relationships. In any case, there may well be multiple causes of relatively high angiosperm species diversity and understanding the relative importance of each of these requires neontological as well as paleontological investigations. One promising approach is to work within the context of phylogenetic patterns with more fossil data.

A new fossil flower from the Turonian of New Jersey: Dressiantha bicarpellata gen. et sp. nov. (Capparales).

Recent discoveries of fossil reproductive structures from deposits of the Raritan Formation in New Jersey (Turonian, Upper Cretaceous, ~90 million years BP) include a previously undescribed representative of the Order Capparales. The fossils are usually charcoalified with three-dimensional structure and excellent anatomical details. In the present contribution, we introduce a taxon represented by fossil flowers that have a combination of characters now found in the families of the Order Capparales sensu Cronquist. The fossil species is characterized by an unique suite of characters, such as the presence of a gynophore, arrangement of the sepals, unequal petal size, monothecal anthers, and a bicarpellate gynoecium, that are found in extant families of the Order Capparales. This new taxon constitutes an important addition to our understanding of Cretaceous angiosperm diversity and represents the oldest known fossil record for the Capparales. Heretofore, the oldest known capparalean was from the Late Tertiary sediments of North America.

Selection of Fossils for Calibration of Molecular Dating Models1

Abstract In the past decade, there has been a rise in interest in the plant fossil record. Fossils potentially provide information for assessing homology and evolutionary change (e.g., the popular missing link phenomenon), character evidence that affects phylogenetic conclusions and, thus, our understanding of modern relationships, evidence of past distributions that can aid in understanding biogeographic histories, and estimates of minimum ages of the clades to which they belong. Recently, many molecular biologists have used fossils in their analyses as a way of providing a calibration point for evolutionary models used to approximate ages for the nodes of phylogenetic trees. However, there has been little, if any, discussion of the criteria by which calibration fossils can be selected for these studies. When considering the use of a fossil as a calibration point, it is critical to take into account the quality of preservation, the method and details of identification (reliability of the taxonomic placement), and the accuracy of the published age. Here, we provide basic criteria for the use of fossils to calibrate molecular evolutionary models. These approaches not only provide better primary estimates for ages of clades, but also provide more reliable sources for those molecular biologists wishing to clean up their molecular clocks.

Fossil flowers and pollen of Lauraceae from the Upper Cretaceous of New Jersey

A fossil trimerous flower from the Turonian (ca. 90 MYBP, Upper Cretaceous) of New Jersey is described as a new genus in the familyLauraceae. The fossil flower is charcoalified and preserved in exceptional detail. This fossil specimen is particularly remarkable in that several pollen grains have been preserved; pollen grains ofLauraceae generally have very thin exine and are rarely preserved in the fossil record. Although the specimen is incomplete and lacks anthers, there are sufficient structural details preserved to permit an assignment to theLauraceae, as well as comparisons with the tribePerseeae. This new genus provides an important addition to our knowledge of systematic and structural diversity in CretaceousLauraceae.

The Diversification of the Leguminosae: First Fossil Evidence of the Mimosoideae and Papilionoideae

The legumes are an important group of flowering plants with a poorly documented evolutionary history. New fossil evidence provides data on the timing of the origin of the two derived subfamilies of legumes (the Mimosoideae and Papilionoideae). These data strongly suggest the importance of bee pollinators during a major period of angiosperm diversification.

Oldest known fossils of monocotyledons

The monocotyledonous angiosperm clade (class Liliopsida) includes roughly 50,000 species of diverse forms. The group comprises such economically noticeable plants as palms, orchids, most of the horticultural bulbs, and grasses, which include some of the most important food crops, such as maize, rice and other grains. Modern monocotyledons are diverse and dominate many habitats, but the fossil record of these plants is meagre, fossils of monocotyledonous flowers are rare, and the earliest putative monocotyledonous fossils (pollen and leaves) are all equivocal,. Here we describe the oldest known fossil flowers that can be definitely assigned to the Liliopsida.

A new fossil fern assignable to Gleicheniaceae from Late Cretaceous sediments of New Jersey.

The recent discovery of well-preserved charcoalified rhizomes, petioles. pinnules, sori, and spores from the Upper Cretaceous of New Jersey provides the basis for the description of a new gleicheniaceous fern, Boodlepteris turoniana. The fossils were collected from unconsolidated sediments of Turonian age (~90 MYBP million years before present; Raritan/ Lower Magothy Formation, Potomac Group). These deposits are rich in angiosperms, but also have a limited representation of fern and gymnosperm remains. Fossil specimens from this locality are particularly remarkable in that minute detail, including anatomical features, are often preserved. Some Boodlepteris specimens have cell by cell preservation that reveals the nature and structure of the stele in rhizomes and petioles, and others show minute details of the sori borne on fertile pinnae. Although these specimens are not in organic connection, there are sufficient structural and anatomical details preserved to confidently suggest that they belong to the same taxon. Cladistic analysis of the fossils, both separately and as a reconstruction, support assignment of Boodlepteris to the extant family Gleicheniaceae.