Abstract Detail

Paleobotanical Section

Taylor, Witt [1].

Morphology of Cyclocarya infructescences (Juglandaceae) from the late Paleocene of North Dakota, USA.

Manchester and Dilcher (1982) named Cyclocarya brownii from the late Paleocene Almont locality, Sentinel Butte Formation of central North Dakota based on fruits preserved on the surfaces of silicified shale. Since this description, over 150 additional specimens have been collected from both the original Almont site and Beicegel Creek, in McKenzie County, western North Dakota. Previously we have described anatomical features of Beicegel Creek fruits, however the nature of infructescences has never been completely explored. Newly described material provides the first evidence for attached fruits of Cyclocarya. Two part-counterpart infructesences with up to 23 attached fruits are known. In contrast to extant Cyclocarya in which fruits are sessile or have very short (0.5-1 mm) peduncles, those of the North Dakota fruits are up to 25 mm long. Modern Cyclocarya infructescences are typically described as pendulous and have relatively few fruits; given the organization of the Almont specimens they appear to have been more robust and to have borne more fruits per infructesence. Fossil and extant fruits also vary in size. The Almont fruits have nutlets 4.5 mm across and wings up to 11.4 mm wide, with a complete fruit diameter of 27.3 mm, in contrast extant fruits are around twice this size with complete fruits ranging from 25-60 mm. Based on fossil infructesences we have, there appears to be no significant size difference in fruits within the infructescence, however the possibility does exist that variation may occur either within or among individuals. While fruits are mostly circular, several show scalloped or undulating margins; however this may be a taphonomic character as the modern fruits exhibit the same effect when they are dried. Since the Paleocene there appears to be a change from a three-dimensional infructescence bearing fruits with long peduncles to a more planar, flattened infructesence in the modern forms. A similar change occurs in Betulaceae from the 3-dimensionally organized Palaeocarpinus to a more planar infructesence in the modern Carpinus.

Broader Impacts:

1 - Arizona State University, School of Life Sciences, P.O. Box 874601, Tempe, Arizona, 85287, USA

Keywords:
Cyclocarya
Almont
Paleocene
Juglandaceae
fossil fruit
living fossil.

Presentation Type: Oral Paper:Papers for Sections
Session: 8
Location: 555B/Convention Center
Date: Monday, August 2nd, 2010
Time: 10:15 AM
Number: 8001
Abstract ID:718