Abstract Detail

Paleobotany

Matel, Theodore [1], Gandolfo, Maria [2], Hermsen, Elizabeth J. [3], Wilf, Peter [4].

New reproductive structures of Cunoniaceae tribe Cunonieae from the early Eocene Laguna del Hunco flora, Chubut, Patagonia, Argentina.

The early Eocene (~52 Ma) Laguna del Hunco flora from Chubut Province, Patagonia, Argentina, has provided key insights into the history of iconic Southern Hemisphere plant taxa, among them Agathis (Araucariaceae), Papuacedrus (Podocarpaceae), Gymnostoma (Casuarianaceae), Eucalyptus (Myrtaceae), and the families Proteaceae, Winteraceae, and Cunoniaceae. Within Cunoniaceae, fruits of Ceratopetalum (tribe Schizomerieae) have previously been described from the flora. Here, we present new reproductive macrofossils with morphological affinities to the extant genus Weinmannia of tribe Cunonieae. The specimens include multiple reproductive axes bearing flowers and fruits, as well as dispersed capsules. Morphological similarities that link the fossils to extant Cunonieae include racemose reproductive axes with acropetal and synchronous flower and fruit maturation; dehiscent, bicarpellate, and syncarpous capsules; persistent, decurrent styles; and four- or five-merous perianth whorls. The combination of a seed-bearing replum in the capsule, septicidally dehiscent capsules, and a persistent 4-5-merous calyx links the specimens to the genus Weinmannia. These specimens represent the first and oldest record of Cunonieae in South America based on reproductive macrofossils, and they provide strong evidence that at least two tribes of Cunoniaceae—Cunonieae and Schizomerieae—had already diversified by the early Eocene. Weinmannia is the most speciose extant genus of family in South America. Globally, it comprises approximately 200 species and is widely distributed in the Neotropics, temperate South America, subtropical and tropical Indian Ocean islands (Comoros, Madagascar, and the Mascarenes), Malesia, and the South Pacific. Therefore, the presence of fossils with affinities to Weinmannia connects the Laguna del Hunco paleoflora in West Gondwana to multiple modern biogeographic regions, presumably through combinations of plate movements and oceanic dispersals.

1 - Cornell University, Plant Biology, 406 Mann Library, Ithaca, NY, 14853, United States
2 - Cornell University, L. H. Bailey Hortorium, Plant Biology Section, SIPS, 406 Mann Library Building, Plant Biology Section, Ithaca, NY, 14853, United States
3 - Paleontological Research Institution, Ithaca, NY, 14850, USA
4 - Pennsylvania State University, Geosciences, 537 Deike Bldg., University Park, PA, 16802, United States

Keywords:
Cunoniaceae
Weinmannia
Reproductive structures
Patagonia
Argentina
early Eocene
fossils.

Presentation Type: Oral Paper
Session: PL1, Paleobotany: Cookson Student Presentations - Session I
Location: /
Date: Monday, July 19th, 2021
Time: 11:30 AM(EDT)
Number: PL1007
Abstract ID:158
Candidate for Awards:Isabel Cookson Award,Maynard F. Moseley Award