Néstor R. Cúneo

Cretaceous/Paleogene Floral Turnover in Patagonia: Drop in Diversity, Low Extinction, and a Classopollis Spike

Nearly all data regarding land-plant turnover across the Cretaceous/Paleogene boundary come from western North America, relatively close to the Chicxulub, Mexico impact site. Here, we present a palynological analysis of a section in Patagonia that shows a marked fall in diversity and abundance of nearly all plant groups across the K/Pg interval. Minimum diversity occurs during the earliest Danian, but only a few palynomorphs show true extinctions. The low extinction rate is similar to previous observations from New Zealand. The differing responses between the Southern and Northern hemispheres could be related to the attenuation of damage with increased distance from the impact site, to hemispheric differences in extinction severity, or to both effects. Legacy effects of the terminal Cretaceous event also provide a plausible, partial explanation for the fact that Paleocene and Eocene macrofloras from Patagonia are among the most diverse known globally. Also of great interest, earliest Danian assemblages are dominated by the gymnosperm palynomorphs Classopollis of the extinct Mesozoic conifer family Cheirolepidiaceae. The expansion of Classopollis after the boundary in Patagonia is another example of typically Mesozoic plant lineages surviving into the Cenozoic in southern Gondwanan areas, and this greatly supports previous hypotheses of high latitude southern regions as biodiversity refugia during the end-Cretaceous global crisis.

Revision of the Proteaceae Macrofossil Record from Patagonia, Argentina

Proteaceae are restricted to the Southern Hemisphere, and of the seven tribes of the subfamily Grevilleoideae, only three (Macadamieae, Oriteae, and Embothrieae) have living members in Argentina. Megafossil genera of Proteaceae recorded from Patagonia includeLomatia, Embothrium, Orites, andRoupala. In this report, we evaluate and revise fossil Argentine Proteaceae on the basis of type material and new specimens. The new collections come from the Tufolitas Laguna del Hunco (early Eocene, Chubut Province), the Ventana (middle Eocene, Río Negro Province), and the Río Ñirihuau (late Oligocene-early Miocene, Río Negro Province) formations, Patagonia, Argentina. We confirm the presence ofLomatia preferruginea Berry,L. occidentalis (Berry) Frenguelli,L. patagonica Frenguelli,Roupala patagonica Durango de Cabrera et Romero, andOrites bivascularis Romero, Dibbern et Gandolfo. Fossils assigned toEmbothrium precoccineum Berry andE. pregrandiflorum Berry are doubtful, and new material is necessary to confirm the presence of this genus in the fossil record of Patagonia. A putative new fossil species of Proteaceae is presented as Proteaceae gen. et sp. indet. Fossil Proteaceae are compared with modern genera, and an identification key for the fossil leaf species is presented. Doubtful historical records of Proteaceae fossils for the Antarctic Peninsula region and Patagonia are also discussed. Based on this revision, the three tribes of Proteaceae found today in Argentina were already present in Patagonia by the early Eocene, where they probably arrived via the Australia-Antarctica-South America connection.ResumenLa familia Proteaceae está restringida al Hemisferio Sur, y en Argentina sólo tres (Macadamieae, Oriteae y Embothrieae) de las siete tribus de la subfamilia Grevilleoideae están representadas. En Patagonia, megafósiles asignados a Proteaceae incluyen los génerosLomatia, Embothrium, Orites yRoupala. En este trabajo, se evalúan y revisan todos los registros fósiles de Proteaceae para Argentina basados en el material tipo y en nuevos especímenes. Las nuevas colecciones fueron realizadas en las formaciones Tufolitas Laguna del Hunco (Eoceno Temprano, Provincia del Chubut), Ventana (Eoceno Medio, Provincia de Río Negro) y Río Ñirihuau (Oligoceno Tardío-Mioceno Temprano, Provincia de Río Negro), Patagonia, Argentina. Se confirma la presencia deLomatia preferruginea Berry,L. occidentalis (Berry) Frenguelli,L. patagonica Frenguelli, Roupala patagonica Durango de Cabrera et Romero, andOrites bivascularis Romero, Dibbern et Gandolfo. Los fósiles asignados aEmbothrium precoccineum Berry andE. pregrandiflorum Berry son dudosos, y nuevo material es necesario para confirmar la presencia de este género en el registro fósil de Patagonia. Una posible nueva especie fósil es presentada como Proteaceae gen. et sp. indet. Los fósiles asignados a Proteaceae son comparados con géneros modernos, y se proporciona una clave para la identification de las especies fósiles. Los registros fósiles históricos dudosos de Proteaceae para la región de la Península Antártica y Patagonia son también discutidos. Basados en esta revisión, las tres tribus de Proteaceae que se hallan hoy en Argentina se encontraban ya presentes en Patagonia durante el Eoceno temprano, donde probablemente arribaron vía la conección Australia-Antártida-Sudamérica.

Pararaucaria delfueyoi sp nov from the late jurassic canadon calcareo formation, chubut, argentina: Insights into the evolution of the cheirolepidiaceae

The discovery of 16 cylindrical conifer seed cones at the Estancia Vilán locality in the Late Jurassic Cañadón Calcáreo Formation of Chubut Province, Patagonia, Argentina, provides anatomically preserved specimens, allowing for the description of a second species of Pararaucaria (Cheirolepidiaceae). The new species, Pararaucaria delfueyoi, is similar in general features to the type species, Pararaucaria patagonica, but has a specifically diagnostic combination of characters that include cone size, seed number, features of histology, and seed size. Specimens are cylindrical with a narrow axis that bears helically arranged bract/scale complexes. The bract and scale diverge from the axis at ∼90° and separate from each other almost immediately. The ovuliferous scale extends toward the margin of the cone and then arches over to enclose two inverted nonwinged seeds within a pocket of tissue. Although the specimens are abraded such that the distal regions of the ovuliferous scales are not preserved, this combination of morphological and histological characters allows for the assignment of P. delfueyoi to the Cheirolepidiaceae with confidence. The co-occurrence of this cone with an undescribed species of Araucaria extends the geographic and stratigraphic ranges of this association, which previously has been known only from the Middle Jurassic of Santa Cruz Province of Patagonia. This extends the knowledge of anatomical variation among seed cones of Cheirolepidiaceae and improves our understanding of homology relationships for conifer seed cone structures.

A Paleogene trans-Antarctic distribution for Ripogonum (Ripogonaceae: Liliales)?

An impressive and growing list of biogeographically interesting plant and animal taxa occur in Paleogene sediments of both southern Australia and southern South America, indicating trans-Antarctic distributions during the warm past. Here, we provide the first evidence that the living, woody, Australasian monocot Ripogonum was present during the early Eocene of Patagonia, Argentina. Two fossil leaves are sufficiently well preserved in overall shape, size, and fine venation details to be assigned to the genus, being closely comparable to leaves of the extant species R. album and R. scandens and the recently described early Eocene species R. tasmanicum from Tasmania, Australia. The new species, R. americanum , is described. Overall, this evidence suggests that Ripogonum had a significantly larger past range, including Antarctica, during the early Paleogene, when Antarctica was much more closely connected to both Tasmania and South America and high latitude climates were warm and wet. Ecologically, the South American Ripogonum was probably a scrambling vine in mesic forest and grew in association with a rich understory flora of ferns and angiosperms.

Potamogetonaceae Fossil Fruits from the Tertiary of Patagonia, Argentina

The subcosmopolitan and aquatic monocot family Potamogetonaceae Berch. and J. Presl 1823 comprises extant and fossil genera. Its known fossil record is composed mainly of fruit remains, and it comes only from Eocene to Pliocene sediments of the Northern Hemisphere (Europe, Saudi Arabia, and China). Recently, several fruits sharing characters with living and fossil Potamogetonaceae genera have been found within the Paleogene Baibián Beds, Chubut, Patagonia, Argentina. Fossils were collected at the Puesto Baibián locality, which outcrops at the eastern sector of the Sierra de La Colonia. Fossils are impressions/compressions of infructescences and isolated fruits and seeds preserved as molds and casts. The infructescences are probably racemes bearing fruits placed most likely in whorls of four each. Isolated fruits are small one‐seeded bisymmetrical endocarps. Palynological studies of the beds show the presence of an assemblage similar to those found in sediments of the Northern Hemisphere where Potamogetonaceae fossil fruits were previously recorded. This report constitutes the first fossil record of Potamogetonaceae for the Southern Hemisphere.

A new marattiaceous fern from the Lower Jurassic of Patagonia (Argentina): the renaissance of Marattiopsis

We here describe Marattiopsis patagonica sp. nov. (Marattiaceae) based on vegetative and fertile foliage impressions from the Lower Jurassic of Chubut Province, Patagonia, Argentina. The new species exhibits a unique combination of vegetative and reproductive features, including a prominent basal auricle; finely undulate, denticulate, to serrulate pinnule margins; interstitial fibres (venuli recurrentes) alternating with regular veins; submarginal position and distinctive relative length of synangia (about 12–20% of the pinnule width); and relatively small number of sporangia pairs per synangium (usually 14 or 16). The new species is assigned to the morphogenus Marattiopsis, since it shows no characters that would allow an unambiguous placement in any of the modern genera, Marattia s.s., Ptisana, or Eupodium. The newly established paraphyly of the Marattia s.l. species has a profound impact on the classification of fossil species. In this context, we provide a brief assessment of the significance of the fossil Marattiopsis for phylogenetic and biogeographical interpretations. It appears that essentially modern marattioid ferns, including Marattiopsis, which are commonly considered to be typical elements of tropical areas of the northern hemisphere during the Mesozoic, may have left an important but largely ignored fossil record in subtropical Gondwana.

FIRST RECORD OF CONIFER WOOD FROM THE CAÑADÓN ASFALTO FORMATION (EARLY–MIDDLE JURASSIC), CHUBUT PROVINCE, ARGENTINA

Abstract. A new fossil conifer wood —Brachyoxylon currumilii sp. nov.— is described from the Lower—Middle Jurassic of Chubut Province (Argentina). The specimens were collected at a locality where the Cañadón Asfalto Formation is exposed, in the vicinity of the Cerro Cóndor village. The studied wood is characterized by mixed pitting in radial tracheid walls (predominantly uniseriate), araucarioid cross fields, low uniseriate rays and the absence of resin canals. The use of transmitted light and epifluorescence microscopy together with SEM imaging allowed the identification of additional characters such as the presence of pitting with torus-margo and compression wood. These characters are discussed in terms of their systematic relevance. On these grounds, the systematic affinity of the studied wood is discussed and linked to the extinct conifer family Cheirolepidiaceae, one of the dominant plant groups during the Jurassic and Cretaceous in Patagonia.