Estudios xilotafoflorísticos del neógeno de los Valles Calchaquíes, Argentina

Abstract

The purpose of this work is to announce the xylotaphofloristic composition of various Neogene formations in northwestern Argentina and to establish comparisons with other contemporary lignofloras allowing

us to arrive at evolutionary, paleoecological, and paleoclimatic considerations. It is worth mentioning that it is the first integrated work on the xylofloras of the region, there was already information on their saltuaria. The materials analyzed in this work belong to the Paleontological Collections of the UNNE “Dr. Rafael Herbst” Paleobotanical Section, under the acronym CTES-PB and CTES-PMP and are deposited in the

Centro de Ecología Aplicada del Litoral (CECOAL-CONICET-UNNE), Corrientes, and the LIL PB Paleobotanical Collection of the Fundación Miguel Lillo, Tucumán, Argentina. As a result of the study, the xylological content of the following formations involved was determined: in the province of Salta, the record

of a Leguminosae in the Palo Pintado Formation (Payogastilla Group), Piptadenioxylon chimeloi Suguio & Mussa, is disclosed. The woods of the formations that integrate the Santa María Group in the provinces of Catamarca and Tucumán were analyzed showing a diverse xylotaphoflora. The San José Formation with specimens of Leguminosae: Peltophoroxylon indicum (Ramanujam) Müller-Stoll & Mädel and a new genus and species of this family and another of Bignoniaceae, adding a Combretaceae with two new species of Terminalioxylon Schönfeld. Other specimens of Leguminosae Paraalbizioxylon caccavariae Martínez, Menendoxylon vasallensis Lutz were found in the Chiquimil Formation, and within the framework of the development of this thesis, two new taxa: Menendoxylon lutzi Baez & Crisafulli and the oldest record of Malvaceae: Bastardioxylon antiqua Baez & Crisafulli. The xylological association that characterizes the

Andalhuala Formation is composed of legumes: Paracacioxylon odonelli Müller-Stoll & Mädel, Paraalbizioxylon caccavariae Martínez, Paraalbizioxylon cienense Cevalloz-Ferriz & Barajas-Morales, Gleditsioxylon fiambalense Baez, a new species of this genus; an Elaeocarpaceae: Elaeocaarpoxylon sloaneoides

Petriella and accompanying this association are monocot specimens: Palmoxylon romeroi Franco, Brea & Herbst (Arecaceae). The Corral Quemado Formation hosts species of Paracacioxylon odonelli Müller-Stoll & Mädel, Mimosoxylon tenax (Felix) Müller-Stoll & Mädel and the only record of a gymnosperm of the Podocarpaceae family: Circoporoxylon krausellii Martínez & Lutz. It is interesting to note that in this work

the first finding of a fossil in the Tambería Formation (Fiambalá Basin) with Baez was reported. In the province of La Rioja, where the Vinchina Formation (from the homonymous basin) outcrops, the first record

of a Bignoniaceae with a new genus and species is described. The fossil woods found in the Las Arcas Formation were not preserved. On the other hand, some of those collected in the Palo Pintado and San Felipe

formations (both of the Payogastilla Group) and those of Toro Negro (Vinchina Basin) could not be determined due to poor preservation. Nevertheless, the analysis of the woods of Palo Pintado allowed making

considerations about the morphological attributes of taphonomic interest that they showed. The analyzed formations share taxa with other contemporaries from Argentina (Corrientes, Entre Ríos, and Santiago del Estero), Brazil, and Colombia. The most heterogeneous paleoxyloflora in terms of composition are those from the San José, Chiquimil and Andalhuala formations. Woods with simple perforation plates, alternate pits, short vessel elements, vasicentric paratracheal parenchyma, and unstratified rays predominate. These features allowed us to infer that they were xylofloras with evolved anatomical characters and that, based on

the results obtained with the vulnerability (VI) and mesomorphy (MI) indices, these specimens can be considered as mesomorphic species. The data provided by the sedimentology and the paleobotanical content of

these stratigraphic units are corroborated by the analysis of the anatomical characteristics that suggested a

hot and humid seasonally dry climate. From a paleoecological point of view, this is confirmed by the presence of coprolites and fungal elements in the xylem of woods from the Chiquimil and Palo Pintado formations, which provided data on the humidity and temperature conditions favorable for their colonization. It

is concluded that through this contribution, the xylological associations of the Neogene of northwestern Argentina were characterized, expanding the known botanical spectrum and establishing its current botanical

affinity while continuing to generate fossil collections to enrich the paleontological heritage of the country.