Early Angiosperm Reproduction: Caloda delevoryana gen. et sp. nov., A New Fructification from the Dakota formation (Cenomanian) of Kansas

A new angiosperm fructification, Caloda delevoryana, is described from the Cenomanian age Dakota Formation of central Kansas. It consists of a long, narrow, main axis with numerous secondary axes arranged helically around the main axis. These secondary axes are each terminated in a small receptacle bearing numerous conduplicate carpels. No evidence of a perianth or androecium was found. This fructification bears some similarity to a number of different modem orders, such as the Hamamelidales, Alismatales, Najadales, and Piperales, and families, particularly the Platanaceae and the Aponogetonaceae, but cannot definitely be assigned to any modem taxon within the angiosperms. C. delevoryana exhibits several characters traditionally assumed to be primitive in the angiosperms, and several other features of this fossil are proposed as primitive in the evolution of angiosperms. This floral axis, with its compact mass of numerous secondary axes bearing very small fruits and seeds, may be the product of reduction through diminished growth of intemodes and carpels, and elaboration through increased repetition of floral modules. This record adds to the rapidly growing body of paleobotanical data on early angiosperm reproductive structures, which should prove important in the assessment of the extent and direction of angiosperm evolution. THE REPRODUCTIVE BIOLOGY of angiosperms is a fundamental driving force behind their evolution and diversity, and currently accepted classifications are based primarily on reproductive characters. However, most of our current ideas of early angiosperm reproductive evolution are based upon inference drawn from both modem comparative studies and the fossil record of isolated, nonreproductive plant organs. These fossil vegetative organs, when they can be placed in a certain modem taxon, are often taken as evidence that the floral structures common to that taxon were also present. In studies of the early evolution of angiosperms, however, it is risky to generalize about the nature of the flowers and fruits from vegetative material. This is evident from some studies of attached vegetative and reproductive material, such as Pseudofagus (Smiley and Huggins, 198 1) and Fagopsis (Manchester and Crane, 1983) in which assignments to the Fagaceae were previously made from leaf fossils. I Received for publication 18 November 1985; revision accepted 25 February 1986. This research was supported by National Science Foundationgrants DEB 79-10720 and BSR 85-16657. We would like to thank Karl Longstreth, William Crepet, Frank Potter, Charles Beeker, and Howard Reynolds for assistance with the field work in the collection of specimens. We also thank Sally Wolfe for drawing the illustrations in Fig. 14, 15, and Steven Manchester for providing helpful comments on the manuscript. When reproductive organs which were found attached to the leaves were studied, it became obvious that they were unique structures and different from those of any extant taxa of the Fagaceae. In recent years, many studies have been made of Cretaceous angiosperm flowers (Tiffney, 1977; Retallack and Dilcher, 1981; Friis and Skarby, 1982; Dilcher and Eriksen, 1983; Friis, 1983, 1984; Basinger and Dilcher, 1984; Crane and Dilcher, 1984; Dilcher and Crane, 1984). These Cretaceous flowers can provide direct evidence of the early radiations of the major groups of angiosperms. In particular, this record can demonstrate the level of divergence of modem orders and families, as well as the presence of "experimental" groups which are now extinct. Many of the more completely understood flowering plant remains cannot be easily placed in any one modem family or order (Basinger and Dilcher, 1984; Dilcher and Crane, 1984; Upchurch and Dilcher, 1984), and some seem to represent extinct groups (Retallack and Dilcher, 1981). This paper presents a new fossil fruiting axis of uncertain taxonomic affinities from the Cenomanian sediments of Kansas which provides new evidence and insight into the record of early angiosperm radiations. MATERIALS AND METHODS-The 10 specimens examined in this study were collected