Oral Paper

         Paleobotany

Cyclocarya brownii (Juglandaceae): an update on what we know about this plant.

Presenting Author
Kathleen Pigg
Description
Cyclocarya brownii Manchester & Dilcher was described in 1982 from the Late Paleocene Almont locality, Morton County, North Dakota, USA. Additional specimens from Almont, including infructescences with attached fruits were discovered in the early 2000s along with exquisite anatomically preserved material at Beicegel Creek, McKenzie County, North Dakota.  Witt Taylor's dissertation in 2011 comprised this material, and since then we have updated and broadened the study to review new occurrences of fossils and new developmental studies of extant Cyclocarya.  We can now recognize several interesting details: 1) in contrast to extant C. paliurus which has relatively few (around 5), widely spaced sessile fruits in a catkin, C. brownii's fruits are crowded, numerous (around 23) and borne on elongate pedicels; 2) fruits are pyramidal with basally attached wings in contrast to equatorial attachment of oblate to lenticular fruits in C. paliurus, and this may correlate with being attached at the broadest part of the fruit; 3) fruit wall anatomy is distinct and more complex than that of extant and related fossil species; 4) triporate (vs tetraporate) pollen of the Momipites triorbicularis (Leffingwell) Nichols type occurs both in typical pollen catkins and in stamens borne on fruits.  Fruits bearing stamens also occur on occasion in extant Cyclocarya paliurus and may be a plesiomorphic character in the clade.  Lastly, 5) individual fruits of Cyclocarya brownii serve as the major disseminule, accounting for the rare occurrence of infructescences in the fossil record. The lignified, persistent infructescence remains on the tree and serves as the platform from which fruits can be dispersed. We interpret the abundance of individual Cyclocarya fruits at the Almont locality to represent sites where the buoyant fruits were carried to relatively low energy environments such as the distal edges of overflow deposits into abandoned channels. The bedforms and more fragmentary fossils recovered at Beicegel Creek suggest a higher energy environment such as fluvial deposition. Clearly, the combination of wind dispersal and hydrochory played a role in dispersal in fossil Cyclocarya, as it does within the genus today.