Abstract Detail


Zou, Xiaoyu [1], Wilf, Peter [1], Donovan, MIchael P. [2], Kocsis, László [3], Briguglio, Antonino  [4].

The First Fossil Leaf Flora from Brunei Darussalam: A Preliminary Report.

Almost no Cenozoic plant macrofossils have been reported from the Malay Archipelago for about 100 years. Here, we investigate newly discovered leaf fossils that are the first known from Brunei, a nation on the north coast of Borneo. The new fossil compression floras are dominated by angiosperm leaves, also including three dipterocarp fruit wings, and come from two sites of probable Pliocene age: Berakas Beach (BB) and Jalan Lugu (JL). Additional details of geology and palynology are given in our companion abstract. After manual preparation and high-resolution imaging, Adobe Bridge was used to keyword the fossil database to expedite rapid sorting into morphotypes, using the Manual of Leaf Architecture (Ellis et al. 2009). From this investigation, we recognized about 17 species. There is abundant evidence of Dipterocarpaceae at both fossil sites and for at least three dipterocarp genera that are currently dominant in the area. Morphotype BR02 (BB) is visibly plicate and has a very straight base, regular eucamptodromous secondary veins, and opposite percurrent intercostal tertiaries that are thin and closely spaced, features that show affinity with Dipterocarpus. Morphotype BR12 (JL) has a strongly folded, elliptic blade with a long-acuminate apex and very dense, thin, secondaries that terminate in an intramarginal vein very close to the leaf margin. These are characteristic features of the dipterocarp Dryobalanops.  A Dipterocarpaceae fruit-wing fragment at BB has at least ten parallel primary veins and a lobe width of ~1 cm, best matching the genus Shorea. Among other plant families, morphotype BR06 (both sites) has five basal acrodromous primaries, three of them more prominent and with a much stronger course than the other two; the lamina is elliptic and major secondaries are interior. The specimens appear to match Ziziphus in family Rhamnaceae. Morphotype BR14 (JL) has five actinodromous primaries with more robust lateral primaries, percurrent and low-angled interior secondaries, and looped marginal venation and probably belongs to the family Melastomataceae. Morphotype BR07 (BB), a likely Malvaceae, has a reflex base angle, cordate base shape, and basally actinodromous primaries. This investigation of plant fossils makes a novel contribution to the historical understanding of the Malay Archipelago flora and highlights the ancient history of the extant taxa that live in the imperiled rainforests of the region.

1 - Pennsylvania State University, Dept. of Geosciences, University Park, Pennsylvania, 16802, United States
2 - Cleveland Museum of Natural History, Department of Paleobotany and Paleoecology, Cleveland, OH, 44106, USA
3 - Universiti Brunei Darussalam, Geology Group, Faculty of Science, Gadong, BE, 1410, Brunei Darussalam
4 - Università degli Studi di Genova, Dipartimento di Scienze della Terra, dell'Ambiente e della Vita, Corso Europa 26, Genoa, I – 16132, Italy

leaf architecture

Presentation Type: Poster
Session: P, Paleobotany Posters
Location: Virtual/Virtual
Date: Wednesday, July 29th, 2020
Time: 5:00 PM Time and date to be determined
Number: PPB003
Abstract ID:306
Candidate for Awards:None

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