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Abstract PremiseFossil infructescences and isolated fruits with characters of Malvoideae, a subfamily of Malvaceae (mallow family), were collected from early Eocene sediments in Chubut, Argentina. The main goals of this research are to describe and place these fossils systematically, and to explore their biogeographical implications. MethodsFossils were collected at the Laguna del Hunco site, Huitrera Formation, Chubut, Patagonia, Argentina. They were prepared, photographed, and compared with extant and fossil infructescences and fruits of various families using herbarium material and literature. ResultsThe infructescences are panicles with alternate arrangement of fruits. They bear the fruits on short pedicels that are subtended by a bract; the fruits display an infracarpelar disk and split to the base into five ovate sections interpreted as mericarps. Each mericarp is characterized by an acute apex and the presence of a longitudinal ridge. The isolated fruits show the same features as those on the infructescences. The fossils share unique features with members of the cosmopolitan family Malvaceae, subfamily Malvoideae. ConclusionsThe fossils have a unique combination of characters that does not conform to any previously described genus, justifying the erection of a new genus and species,Uiher karuen. This new taxon constitutes the first known Malvoideae reproductive fossils of the Southern Hemisphere, expanding the distribution of Malvoideae during the early Eocene.
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Reinterpretation of Paleoazolla : a heterosporous water fern from the Late Cretaceous of Patagonia, Argentina
PremiseUndoubtedly, fossils are critical for understanding evolutionary transformations in deep time. Here, we reinvestigate the microspores and megaspores ofPaleoazolla patagonica, a water fern found in Late Cretaceous sediments of the Chubut Province, Patagonia, Argentina, which provides novel evidence on the past history of the water fern clade. The study was based on recently collected specimens and additional observations of the original material. MethodsMost specimens analyzed herein were obtained from new palynological samples collected at the Cerro Bosta and Cañadón del Irupé localities, La Colonia Formation. Samples were mechanically disaggregated and treated with hydrofluoric and hydrochloric acid. Spores were studied using standard light microscopy and scanning electron microscopy. We also reexamined the original materials. ResultsThe newly described characters ofPaleoazollainclude the presence of heterosporangiate sori composed of one ellipsoidal megasporangium surrounded by three to four oval microsporangia, megasporangium containing one hairy massula that encloses two trilete megaspores (rarely one or three), and microsporangia containing numerous microspore massulae with non‐septate multibarbed glochidia and one trilete microspore per massula. ConclusionsThe reinterpretation has revealed a novel set of characters for understanding the evolution of heterosporous water ferns. The presence of two megaspores in the megasporangium ofPaleoazollaexposes serious gaps in the current knowledge on the evolution of monomegaspory in heterosporous water ferns, a fact that emphasizes the need of including fossils within phylogenies to elucidate patterns of character acquisition among water ferns.
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- Award ID(s):
- 1925552
- PAR ID:
- 10456529
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- American Journal of Botany
- Volume:
- 107
- Issue:
- 7
- ISSN:
- 0002-9122
- Format(s):
- Medium: X Size: p. 1054-1071
- Size(s):
- p. 1054-1071
- Sponsoring Org:
- National Science Foundation
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