Fossil woods from Argentina

: Argentinean fossil woods have been studied since the end of the XIX century and numerous publications have dealt with this type of fossil. A database of 324 records including fossil woods from the Carboniferous to the Pleistocene found in Argentina (including Malvinas/Falkland Islands) was built. The publications about fossil wood records through 134 years (1884–2021) can be divided into three periods, i) publications by non-Argentine researchers (1884–1940), ii) sporadic publications by researchers from Argentina (1941–1999), and iii) frequent publications by researchers from Argentina (2000–2021). The database has updated information (i


INTRODUCTION
Fossil wood (secondary xylem) records from Argentina are abundant.They came from a wide time range, from the middle Carboniferous (Pujana & Césari 2008) to the Pleistocene (e.g., Moya & Brea 2015a), covering all periods/epochs between them.Fossil woods have been described since 1884 and in 134 years  the anatomy of more than 900 specimens was studied.This type of fossil plant is essential to reconstruct the past flora and the canopy composition of the forests of the past.In addition, based on detailed studies of the woods, inferences about the paleoclimate (e.g., Ruiz et al. 2021) are made.
Fossil wood was the first type of fossil to be observed in a (rudimentary) microscope and illustrated and published (Hook 1665).In the first half of the XIX century, Witham (1831) illustrated the first transverse sections of fossil woods and later the first detailed descriptions of fossil wood anatomy were published, mostly with specimens from Europe (e.g., Lindley & Hutton 1833;Witham 1833;Zenker 1833).Since then, thousands of woods have been described worldwide.In Argentina, the first mentions of fossil woods are from the early XIX century (Ottone 2005), but the first anatomy descriptions were made by Conwentz (1884).
Some databases of Argentinean paleobotany records have been published (Menéndez 1968(Menéndez , 1979;;Archangelsky et al. 2000), and some exclusively of fossil woods (Lutz & Herbst 1986;Herbst et al. 2007) or woods of a taxonomic group (e.g., Pujana et al. 2011).In addition, some global fossil databases include Argentinean woods (e.g., Gregory et al. 2009;InsideWoood 2004-onwards;Philippe et al. 2004).However, they are now outdated, and the last database of Argentinean fossil woods by Herbst et al. (2007) contains only a part (less than 40 %) of the records compiled herein.Besides, this new database includes repository numbers, the newest nomenclature/systematics, synonyms, and the newest given ages to the fossiliferous localities or stratigraphic units.

MATERIALS AND METHODS
The database has all the fossil wood records found in Argentina published up to 2021 from the Carboniferous to the Pleistocene; subfossils from the Holocene (e.g., Rabassa et al. 1991) are omitted.It includes records from the Malvinas/ Falkland Islands, but not the sector of Antarctica claimed by Argentina.Each record (or entry) of the database corresponds to a taxonomic unit from a stratigraphic unit, similar criteria used by Pujana et al. (2011;2021a) and Panti et al. (2012).Each record may have a formal species name (e.g., Nothofagoxylon triseriatum), an informal name (e.g., "sample x", or "xilotipo 3") or an open nomenclature name (e.g., Agathoxylon sp.).Specimens assigned to "indeterminate conifer" or similar designation (e.g., Pujana et al. 2020a) without a description are not included.A taxonomic unit found in two localities of the same stratigraphic unit but far away enough (i.e., more than ca.50 km) and published separately are included in different records (e.g., Pujana et al. 2020b andPujana et al. 2021b).References of revisions and re-descriptions are included in the record of the original description.
Only secondary xylem (wood) with anatomical descriptions are included, with or without primary structures (i.e., pith and primary xylem).Records with the mere mention of fossil wood names, if they do not have at least some description or illustration of anatomical features, are not included (e.g., Darwin 1839;Frenguelli 1946;Archangelsky & Brett 1960;Artabe & Zamuner 1991;Ganuza et al. 1998;Zucol et al. 2005).The database does not include palms (e.g., Ancíbor 1995) and tree ferns (e.g., Herbst 2006), plants that lack typical secondary xylem.However, it includes manoxylic gymnosperms like cycads (e.g., Martínez et al. 2012).The database includes records published in articles from journals, books, book chapters, and special publications.It does not include conference abstracts, theses or unpublished publications.

A brief history of Argentinean fossil wood studies
In Argentina, the presence of fossil woods has been mentioned since the beginning of the XIX Century (Ottone 2005).Azara (1809) mentioned for the first time fossil woods from Paraná and Uruguay rivers, but he was unaware that the pieces of wood were fossilized.Later D'Orbigny (1835) mentioned and recognized silicified woods as fossils (Ottone 2005).However, the first mention of fossil wood with some taxonomic identification is that of Darwin (1839), who mentioned the presence of fossil woods from the Triassic of Uspallata, Mendoza Province.Darwin's samples were identified by Robert Brown, an English botanist, as araucariaceous, but they did not provide more anatomical details and therefore that record is not included in the database herein.Fossil woods from this fossiliferous locality (now called Darwin's Forest, not to be confused with another Darwin's Forest from Chile) were later described by Brea (1997) as Araucarioxylon protoaraucana Brea (Thomas 2009) and by Artabe & Brea (2003) as Cuneumxylon spallettii Artabe & Brea.Studies of fossil wood anatomy from Argentina can be divided into three periods.
i) Publications by non-Argentine researchers : The first detailed study with anatomical descriptions and the first naming of new fossil species from Argentina (and South America) was made by Conwentz (1884).Hugo Conwentz, 1855Conwentz, -1922, was a German botanist who described seven taxonomic units from the Tertiary of today Río Negro Province.These fossil woods were collected by the Argentine geologist Adolfo Döring and other collaborators during the "Conquista del Desierto" (sic), a military expedition (Herbst 2013).This article, according to the publications of that time, has short descriptions of dicots and conifers and no illustrations.Some of these specimens, deposited in Córdoba Province, were being revised (Herbst 2013;Crisafulli & Herbst 2014).Twenty-six years af-ter, Halle (1912) described four taxonomic units from the Permian and Cenozoic of the Malvinas/ Falkland Islands.Publications from 1912 to 1940 are sporadic (e.g., Gothan 1925) and the article of Kräusel (1924) stands out in this period.Richard Kräusel (1890Kräusel ( -1966) ) was a German botanist, who described in his article (Kräusel 1924) several fossil woods from Chilean and Argentinean Patagonia.Most of the fossil species' names are still in use.
ii) Sporadic publications by researchers from Argentina : After fourteen years without publications on fossil woods, Lucas Tortorelli, 1908Tortorelli, -1978 an Argentine agronomist who specialized in forest science, published a fossil wood with Ginkgoaceae affinity from the Cretaceous of Río Negro Province (Tortorelli 1941).This is the first fossil wood anatomy description published by an Argentine.Later, sporadic works include that of Archangelsky (1960), who described two Paleozoic gymnosperms from the Permian of Patagonia, the first cycad stems described by Archangelsky & Brett (1963), and the first corystosperm (Rhexoxylon) by Archangelsky & Brett (1961).Besides other sporadic articles, the article of Petriella (1972) with specimens from the Paleocene of Chubut Province (Patagonia) stands out.
iii) Frequent publications by researchers from Argentina : Publications since the year 2000 are much more frequent, and usually several records per year are published.This pe-This period includes 76 % of the records.Moreover, publications have increased significantly in the last 15 years, since ca.2005 (Fig. 1).Most of the researchers and their groups that began publishing at the beginning of this century (e.g., Crisafulli et al. 2000;Brea et al. 2001a) are active and many other researchers are constantly publishing.In addition, given the abundance of fossil woods in Argentina, many more results are expected in the next years.

The fossil wood record of Argentina
Of the 324 records of the Argentinean fossil wood database (Table 1), the majority (62 %) are from Patagonia, the southernmost region of South America that includes Río Negro, Neuquén, Chubut, Santa Cruz, and Tierra del Fuego, Antártida e Islas del Atlántico Sur provinces (including the Malvinas/Falkland Islands but not the Antarctic Region claimed by Argentina) (Fig. 2).This can be the result of the great extension of the region (800,000 km 2 ) with scarce vegetation in most of it and a mountainous relief mostly in the west that makes this region an outstanding place for fossiliferous outcrops.Santa Cruz Province has the highest percentage of records (27 %) followed by Chubut Province (18 %).The Mesopotamia Region (mostly from one of its provinces, Entre Ríos) follows the Patagonia Region in the percentage of records (14 %) (Fig. 2).
Fossil woods from the Paleozoic, usually lack an accurate botanical affinity and are assigned to several fossil genera.Many of them have the pith preserved.The pith and primary xylem have very important diagnostic characters and can be crucial to define the fossil genus (Lepekhina 1972).The oldest fossil wood described until today is Cuyoxylon multipunctatum, from the middle Carboniferous of San Juan Province, and is probable the oldest from Gondwana with a coniferous structure (Pujana & Césari, 2008).In the Carboniferous, the oldest Argentinean pteridosperm was described by Césari et al. (2005).
During the Triassic, woods of conifer families (that are still alive) appeared (e.g., Araucariaceae, described by Brea 1997).The oldest angios- The oldest angiosperm (Cretaceous) was recently described: Carlquistoxylon australe by Nunes et al. (2018) from central Patagonia and it is also the oldest angiosperm wood from South America.It has, as many Cretaceous angiosperm woods, uncertain affinities.
The records are distributed through all the periods/epochs, but most of them are from the Cenozoic (57 %).Particularly, Pliocene and Pleistocene have more records per Ma, a consequence of the numerous studies of the Entre Ríos Province (e.g., Franco et al. 2020).
The database built herein, has more than twice as many records as previous databases (e.g., Herbst et al. 2007), mainly a consequence of the numerous publications of the last years.The database also has complete fields of each record (e.g., repository numbers).The records indicate that Argentina has a high number of records found in all epochs since the Carboniferous and a high diversity of fossil woods.The outlook for the future of this discipline is encouraging as current researchers are publishing several descriptions of fossil woods per year, and new localities that carry this type of fossil continue to appear.
Appendix: complete database of Argentinean fossil woods, including references (Table 1 + online supplementary data).