Scherer, Jacqueline , Upchurch, Garland , Mack, Greg .
A new species of Pandanites from the Maastrichtian of south-central New Mexico: implications for the history of Pandanaceae.
CONTRADICTORY evidence exists for the presence of Pandanaceae in North America during the Late Cretaceous. Previous workers have compared dispersed fossil leaves and pollen of latest Cretaceous age to extant leaves and pollen of Pandanus; however, isolation of Pandaniidites pollen from coeval megafossils of Araceae implies that these identifications might be in error. Examination of a new species of Pandanites leaves from the Late Cretaceous (Maastrichtian) Jose Creek member of the McRae Formation (south-central New Mexico), and comparison with leaves of extant Pandanaceae and previously described fossil species, indicate that Pandanaceae or their stem lineage were widespread in the Northern Hemisphere during the Late Cretaceous. The new species of Pandanites, known from over 50 specimens, has a suite of foliar architectural characters restricted to extant Pandanaceae. These features include thick, strap-like leaves that are M-shaped in cross section, a margin armed with small, apically-oriented spines, longitudinal parallel veins of only one order, the absence of a thickened midvein, and weak cross veins that are oblique or perpendicular to the longitudinal parallel veins and interconnect only with adjacent veins. Abaxial midrib spines, a characteristic of extant Pandanaceae, have been tentatively identified on at least one specimen, but this character is difficult to substantiate because it is visible only in longitudinally split or folded leaves. The new species of Pandanites differs from previously described species, such as P. corsonii of North America and P. trinervis of Europe, in its narrower width (< 2.0 cm) and more crowded marginal prickles, but shares with these species foliar architectural features that diagnose extant Pandanaceae. These results reinforce previous evidence that Pandanaceae and other thermophilic taxa were widespread in the Northern Hemisphere during the Late Cretaceous and Early Tertiary and subsequently became restricted to Asia and the Southern Hemisphere through extinction.[c.e.:srb]
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1 - Texas State University, Department of Biology, 601 University Drive, San Marcos, Texas, 78666, USA
2 - New Mexico State University, Department of Geological Sciences, Las Cruces, New Mexico, 88003, USA
Presentation Type: Oral Paper:Papers for Sections
Date: Monday, July 31st, 2006
Time: 2:15 PM