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Leguminosae are one of the most diverse flowering-plant groups today, but the evolutionary history of the family remains obscure because of the scarce early fossil record, particularly from lowland tropics. Here, we report ~500 compression or impression specimens with distinctive legume features collected from the Cerrejón and Bogotá Formations, Middle to Late Paleocene of Colombia. The specimens were segregated into eight fruit and six leaf morphotypes. Two bipinnate leaf morphotypes are confidently placed in the Caesalpinioideae and are the earliest record of this subfamily. Two of the fruit morphotypes are placed in the Detarioideae and Dialioideae. All other fruit and leaf morphotypes show similarities with more than one subfamily or their affinities remain uncertain. The abundant fossil fruits and leaves described here show that Leguminosae was the most important component of the earliest rainforests in northern South America c. 60–58 million years ago.
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Reassessing floral diversity at Río Pichileufú, earliest middle Eocene of Río Negro, Argentina
The Río Pichileufú (RP) fossil locality contains one of Patagonia’s only well-dated middle Eocene floras, deposited ca. 47.7 Ma during the onset of global temperature decline and South America's tectonic isolation. In 1938, Edward W. Berry described 135 species from RP based on compressed angiosperm leaves and rare reproductive structures. The flora was considered highly diverse and to have predominantly Neotropical affinities; however, many of Berry’s identifications were botanically incorrect, confusing interpretations of composition, diversity, and biogeography. Only a fraction of the flora has been studied since, and substantial new collections have remained unevaluated. Here, we reassess the fossil leaves from RP, creating a stable platform for systematic and ecological analyses. We use a morphotype approach to bypass the numerous prior taxonomic errors, while preserving nomenclatural links to specimens. We jointly consider the type and cohort (n = 696) and recent (n = 1286) collections. We validate 82 leaf morphotypes in the type collections, much lower than Berry’s estimate of 131, and consider 43 species as indeterminate. We find that 44 historical species were improperly split, lumped, or misaligned to existing names. At least 12 plant families and 30 plant genera initially reported from the site are unreliable, including Poaceae, Cannabaceae, Ericaceae, Hydrangeaceae, and Rosaceae. However, considering all the collections, we recognize 158 total leaf morphotypes. Reliable taxa include ginkgophytes, Norfolk Island pines (Araucaria), legumes (Fabaceae), soapberries (Sapindaceae), and laurels (Lauraceae). Although Berry's initial assessment of diversity at RP was significantly overestimated, including new material re-establishes the flora as exceptionally diverse.
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- PAR ID:
- 10589832
- Publisher / Repository:
- Paleontological Society
- Date Published:
- Journal Name:
- Palaeontologia Electronica
- Volume:
- 27
- Issue:
- 3
- ISSN:
- 1935-3952
- Page Range / eLocation ID:
- a49
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Leguminosae are one of the most diverse flowering-plant groups today, but the evolutionary history of the family remains obscure because of the scarce early fossil record, particularly from lowland tropics. Here, we report ~500 compression or impression specimens with distinctive legume features collected from the Cerrejón and Bogotá Formations, Middle to Late Paleocene of Colombia. The specimens were segregated into eight fruit and six leaf morphotypes. Two bipinnate leaf morphotypes are confidently placed in the Caesalpinioideae and are the earliest record of this subfamily. Two of the fruit morphotypes are placed in the Detarioideae and Dialioideae. All other fruit and leaf morphotypes show similarities with more than one subfamily or their affinities remain uncertain. The abundant fossil fruits and leaves described here show that Leguminosae was the most important component of the earliest rainforests in northern South America c. 60–58 million years ago.more » « less
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.26879/1383
