Doyle, James A. , Endress, Peter K. , Upchurch, Garland .
Early Cretaceous monocots: a phylogenetic evaluation.
Reports of Early Cretaceous monocots have been questioned as being based on faulty systematic criteria and not supported by phylogenetic analyses, even though their commonly proposed sister clades, magnoliids and eudicots, were radiating at this time. We evaluate the Early Cretaceous monocot record using morphological data sets for basal angiosperms and seed plants, and assuming relationships among living taxa derived from morphological and molecular data. For pollen, our analyses support a monocot affinity for Liliacidites, boat-shaped monosulcate pollen with graded sculpture that becomes finer at the ends of the grain, based on the presence of similar pollen in multiple monocot orders and its absence from non-monocotyledonous groups. However, pollen with finer sculpture at the poles, originally assigned to Liliacidites but segregated as Similipollis, has been associated with floral parts called Anacostia, which seed characters indicate is nested within Austrobaileyales. Pollen identified as “Liliacidites” minutus was produced by Virginianthus, a flower that appears to belong near the base of Laurales. Masses of striate pollen called Mayoa share unique derived characters with some Araceae, but the coarsely reticulate pollen genus Pennipollis and associated floral remains, also compared with Araceae and other Alismatales, are more likely related to Chloranthaceae, based on their combination of floral and pollen characters. For vegetative remains, analysis in the context of a seed plant data set supports a monocotyledonous affinity for Acaciaephyllum, a shoot bearing leaves with apically converging major venation. Although Acaciaephyllum resembles some Gnetales in having parallel-appearing major venation and chevron-like cross-veins, a monocot relationship is favored by its alternate phyllotaxis, distinct medial vein, and sequential fusion of lateral veins at the apex, features that contrast with all Gnetales or those with superficially similar leaves. Leaf fragments from the late Albian-early Cenomanian of Australia have derived venational and stomatal features indicative of monocots.
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1 - University of California, Davis, Department of Evolution and Ecology, One Shields Ave., Davis, California, 95616, USA
2 - University of Zurich, Institute of Systematic Botany, Zollikerstrasse 107, Zurich, 8008, Switzerland
3 - Texas State University, Department of Biology, San Marcos, Texas, 78666, USA
Presentation Type: Oral Paper:Papers for BSA Sections
Location: Superior A/Cliff Lodge - Level C
Date: Wednesday, July 29th, 2009
Time: 11:00 AM