Fossil woods from the Lower Cretaceous Tres Lagunas Formation of central Patagonia (Chubut Province, Argentina)

Journal Pre-proof Fossil woods from the Lower Cretaceous Tres Lagunas Formation of central Patagonia (Chubut Province, Argentina) Carlos D. Greppi, Roberto R. Pujana, Roberto A. Scasso PII:

S0195-6671(19)30268-X

DOI:

https://doi.org/10.1016/j.cretres.2019.104322

Reference:

YCRES 104322

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Cretaceous Research

Received Date: 21 June 2019 Revised Date:

30 September 2019

Accepted Date: 17 November 2019

Please cite this article as: Greppi, C.D., Pujana, R.R., Scasso, R.A., Fossil woods from the Lower Cretaceous Tres Lagunas Formation of central Patagonia (Chubut Province, Argentina), Cretaceous Research, https://doi.org/10.1016/j.cretres.2019.104322. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Elsevier Ltd. All rights reserved.

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Fossil woods from the Lower Cretaceous Tres Lagunas Formation of central Patagonia

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(Chubut Province, Argentina)

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Carlos D. Greppia*, Roberto R. Pujanaa and Roberto A. Scassob.

4

a

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Ciudad de Buenos Aires, Argentina.

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b

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Departamento de Geología, Facultad de Ciencias Exactas y Naturales, Universidad de

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Buenos Aires, Intendente Guiraldes 2620, (1428) Ciudad de Buenos Aires, Argentina.

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*Corresponding autor. E-mail address: [email protected]

Museo Argentino de Ciencias Naturales-CONICET, Av. Ángel Gallardo 470, (1405)

Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires (IGEBA),

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ABSTRACT

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Silicified fossil woods are common in the Tres Lagunas Formation (Lower Cretaceous) of

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central Patagonia. This region has a poor record of Early Cretaceous fossil woods. A

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collection of 23 fossil woods is studied. Fossil wood anatomy is described and compared in

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detail. The wood flora is composed of conifers. Most of the samples have Araucariaceae-

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like wood anatomy. The samples are placed into seven taxonomic units: three fossil-species

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of Agathoxylon, two more taxonomic units related to Agathoxylon, one taxonomic unit

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consistent with Cupressinoxylon? and one fossil-species of Brachyoxylon. This study

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indicates a dominance of conifers, particularly Araucaiaceae, during the Early Cretaceous

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of this zone of central Patagonia which partially does not coincide with the taxonomic

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proportions of previous studies of coeval pollen and plant macrofossils.

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Key words: Fossil wood; Wood anatomy; Conifers; Early Cretaceous; Tres Lagunas

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Formation.

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1. Introduction

27 28

Gondwana's Early Cretaceous was characterized by a series of events related to the

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development of rifts and the fragmentation of the continent, marine regressions and

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transgressions, absence of polar ice and changes in the concentration of CO2 due to the rift-

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associated volcanism that induced the expansion of the warm to temperate paleoclimate

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zones toward the poles and favored the development, extension and diversification of the

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flora (McLoughlin, 2001; Passalía, 2004; Del Fueyo et al., 2007).

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During the Early Cretaceous, southern Patagonia flora was dominated by different

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groups of conifers and pteridosperms, in addition to ginkgoaleans, cycads, bennettitaleans,

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equisetaleans and ferns. Within the conifers, the most important groups were the

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Araucariaceae, the Podocarpaceae and the Cheirolepidiaceae that developed large tall

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forests and associated umbrophil plants in delta, fluvial and lacustrine environments, while

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the open areas were apparently dominated mainly by cycads and bennettitals (Del Fueyo et

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al., 2007). These paleoflora studies are based on the abundant fossil leaves and

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palynomorphs from different stratigraphic units of central and southern Patagonia

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(Baldoni, 1979; Baldoni and De Vera, 1980; Archangelsky et al., 1984; Archangelsky and

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Llorens, 2003).

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Detailed studies of Patagonian woods from the Lower Cretaceous, however, are

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scarce and isolated, and there are only some recent studies mostly based on one or very few

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samples (e.g. Martínez and Lutz, 2007; Vera and Césari, 2012; Carrizo and Del Fueyo,

47

2015; Brea et al., 2016; Gnaedinger et al., 2017; Nunes et al., 2018, 2019).

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In this contribution, a relatively large collection of fossil woods is described with

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taxonomy based on recent bibliography. This is the first detailed study of the anatomy of

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conifer woods from the Tres Lagunas Formation and from southwestern Chubut Province,

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Argentina. Comments about the diversity of the ancient forests and comparisons to other

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paleofloras are made.

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2. Geological setting

55 56

The Tres Lagunas Formation is equivalent to the Toqui Formation, the lowermost

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unit of the Tithonian–Aptian Coyhaique Group (Heim, 1940; Ramos, 1981; Suárez et al.,

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2009). It discordantly overlies Jurassic lavas and breccias of the Lago La Plata Formation

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and upper Paleozoic sedimentary rocks and it is transitionally overlain by the Katterfeld

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and Apeleg formations (Fig. 1) (Ramos, 1981; Olivero, 1987; Ploszkiewicz, 1987).

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According to the literature the age of the Coyhaique Group is not older than Tithonian and

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not younger than Aptian (Scasso, 1989). The most likely age for the Tres Lagunas

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Formation is late Valanginian (Aguirre Urreta and Rawson, 1998).

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The Tres Lagunas Formation mainly consists of conglomerates, sandstones, shales

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and black limestones cropping out close to the Tres Lagunas locality (Fig. 2) and in the

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southern margin of the Fontana Lake (Bergmann, 1956; Ramos, 1981; Scasso, 1989;

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Hechem et al., 1993). In spite of intense faulting and folding, the lithology and fossiliferous

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content of the rocks, together with their relation with other formations in the region, drove

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most authors to consider the Tres Lagunas Formation as a single sequence (Masiuk and

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Nakayama, 1978; Ramos, 1981) of mixed carbonate-siliciclastic and pyroclastic sediments

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(Scasso, 1989), with an upward trend towards siliciclastic deposits at the top in the Tres

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Lagunas area (Scasso and Kiessling, 2002). There, thick conglomerate beds with rounded

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clasts and sandy matrix, at the base of the unit, bear dark purple, silicified logs

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(Ploszkiewicz, 1987). Dark shales with interbedded sandstones and black limestones,

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contain a marine, varied mollusc fauna (Ploszkiewicz and Ramos, 1977; Ramos, 1981;

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Ploszkiewicz, 1987; Olivero, 1983). Rapid lateral and vertical facies changes characterize

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the Tres Lagunas Formation. This is attributed to a very irregular relief caused by tectonism

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and volcanism. Depositional environments range from coastal, shallow marine

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environments (e.g. shoreface and patch-reef), developed on the margins of small volcanic

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islands, to deeper fringe-apron environments such as front-reef or small submarine fans

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developed around and down-slope of the clastic-carbonatic shelves (Scasso, 1987; 1989).

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Synchronous volcanism is represented by coarse volcanic detritus, which comprises most of

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the epiclastic fraction, as well as by fall-out tuffs interbedded with the clastic and

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carbonatic beds (Scasso, 1989; Scasso and Kiessling, 2002).

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3. Material and methods

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A collection of 23 fossil woods was studied. The samples were collected in central

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Patagonia, in the Tres Lagunas locality, from two fossiliferous outcrops (1= 44°52'02'' S,

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70º47'16'' W and 2= 44º52'07'' S, 70º47'49'' W, Fig. 1). Both outcrops are in the type

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locality of the Tres Lagunas Formation, 20 km north of Alto Rio Senguer town, Chubut

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Province, Argentina. Samples were stratigraphical and geographically located (Fig. 1, Fig.

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2).

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These specimens are housed in the Museo Paleontológico Egidio Feruglio, located

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in Chubut Province, Argentina, under accession numbers MPEF Pb 10113–10135 (Table

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1). Microscopic slides bear the same number as the hand specimen followed by a lower

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case letter.

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The specimens are silicified, mainly dark purple. They were sectioned according to

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the typical methodology for studying petrified woods: transverse section (TS), radial

100

longitudinal section (RLS) and longitudinal tangential section (TLS). Some acetate peels

101

according to the method of Galtier and Phillips (1999) were carried out, but these did not

102

show good anatomical details. All samples were observed with scanning electron

103

microscopy (SEM) after being gold coated. The slides were studied using light microscopy

104

(Leica DM2500) and photographed with Leica 1295 DFC camera. At least 20

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measurements or observations of each character for each specimen were made when

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possible. Measurements are expressed as the weighted mean followed by the range between

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parenthesis and mean standard deviation of all the specimens assigned to each taxonomic

108

unit.

109

The terminology used follows the IAWA recommendations for softwood

110

identification (IAWA Softwood Committee, 2004) when possible. Indices for measuring

111

and quantifying the radial intertracheary pitting arrangement (Cp and Si) are those of

112

Pujana et al. (2016). Si= 1. 00 indicates that all the intertracheary pits are uniseriate, Si > 1.

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00 indicates that there are two- or more-seriate pits, Cp= 0 % that no pits touch and Cp=

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100 % that all pits touch (Pujana et al., 2016). For open nomenclature names, Bengston

115

(1988) was followed.

116

It is very challenging to assign an accurate extant affinity to fossil woods previous

117

to the Cenozoic, and the parataxonomy for fossil-genera delimitation of Philippe and

118

Bamford (2008) is followed. Consequently, only the fossil-genus and not higher taxonomic

119

ranges are given in the systematic palaeontology section, but the probable familial affinity

120

is discussed in the remarks of each taxonomic unit.

121 122

4. Systematic palaeontology

123 124

Fossil-genus Agathoxylon Hartig, 1848

125

Type species: Agathoxylon cordaianum Hartig, 1848, p. 188

126 127

Agathoxylon antarcticus (Poole and Cantrill, 2001) Pujana, Santillana and Marenssi, 2014

128

Fig. 3A–H

129

2001 Araucariopitys antarcticus Poole and Cantrill, p. 1086, pl. I, figs. 2–10.

130

2005 Agathoxylon matildense Zamuner and Falaschi, p. 340, fig. 2.

131 132

New material. MPEF-Pb 10115, 10117, 10124, 10125 and 10131.

133

Description. The specimens are pycnoxylic secondary xylem, with variable preservation.

134

Growth rings boundaries are distinct, latewood with 2–6 rows of tracheids (Fig. 3A–B).

135

The earlywood-latewood transition is abrupt and the cells roundish to polygonal in

136

transverse section. Intertracheary pitting on radial walls is araucarian, uni- to biseriate, in

137

most samples predominantly uniseriate (Si= 1.10), contiguous (Cp= 90.1%), and alternate

138

when biseriate (Fig. 3C–D). Intertracheary radial pits are circular to hexagonal, 12.5 (9.8–

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15.4, sd= 1.0) µm in vertical diameter. Tracheid tangential diameter is 37.9 (19.5–59.2, sd=

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4.7) µm. Pits on tangential section are not observed. Horizontal and end walls of ray

141

parenchyma cells are smooth. Mean ray height is very low to medium 6.8 (1–25, sd= 4.7)

142

cells high, almost exclusively uniseriate (Fig. 3E–F), very rarely biseriate portions and with

143

a frequency of 5.3 (3–8, sd= 1.0) rays per mm. Ray height is 143 (20–459, sd= 90) µm.

144

Cross-fields are araucarioid with 4–9, mean 6.2, sd= 0.9, contiguous pits per cross-field

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(Fig. 3G–H, Fig. 4A). Cross-field pits are half-bordered (= oculipores) circular and 7.1

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(4.7–11.4, sd= 0.6) µm in vertical diameter.

147

Remarks. This fossil-species is characterized by its distinct to indistinct growth ring

148

boundaries, araucarian mostly uniseriate radial intertracheary pitting, araucarioid cross-

149

fields and absence of axial parenchyma and resin plugs. Pujana et al. (2014) discussed and

150

compared this fossil-species in detail.

151

The wood anatomy of A. antarcticus, and from all the samples referred to

152

Agathoxylon from the Tres Lagunas Formation are typical of the living Araucariaceae, as

153

many of the species of Agathoxylon. However, not all the numerous Agathoxylon species,

154

particularly Paleozoic species, can be assigned to this family (Philippe, 2011; Rößler et al.,

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2014).

156

Agathoxylon antarcticus was found in Antarctica from the Cretaceous to the Eocene

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(Poole and Cantrill, 2001; Pujana et al., 2014, 2015, 2017; Mirabelli et al., 2017). In South

158

America was found in the Jurassic and Cretaceous (Zamuner and Falaschi, 2005; Pujana et

159

al., 2007). This fossil-species is the most abundant of the assemblage of the Tres Lagunas

160

Formation (Table 1).

161 162

Agathoxylon kellerense (Lucas and Lacey, 1981) Pujana, 2017

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Fig. 3I–P

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1990 Araucarioxylon kellerense Nishida, Ohsawa and Rancusi, p. 27.

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Basionyms. Dadoxylon kellerense Lucas and Lacey, 1981.

166 167

New material. MPEF-Pb 10116, 10118, 10119 and 10135.

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Description. The specimens are pycnoxylic secondary xylem, with variable preservation.

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Growth ring boundaries are distinct, latewood with 1–7 rows of tracheids (Fig. 3I). The

170

earlywood-latewood transition is abrupt and the cells are roundish to polygonal as seen in

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transverse section. Intertracheary pitting on radial walls is araucarian, uni- to triseriate,

172

mostly biseriate or triseriate, rarely uniseriate (Si= 2.05), contiguous (Cp= 100%), and

173

alternate when biseriate or triseriate (Fig. 3J–L). Intertracheary radial pits are hexagonal,

174

13.7 (9.5–19.1, sd= 1.2) µm in vertical diameter (Fig. 3J–L). Tracheid tangential diameter

175

is 38.9 (19.2–62.9, sd= 6.4) µm. Pits on tangential walls are slightly smaller and with

176

similar arrangement to the intertracheary radial pits (araucarian). Horizontal and end walls

177

of ray parenchyma cells are smooth. Mean ray height is medium, 8.3 (1–29, sd= 4.4) cells

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high, exclusively uniseriate (Fig. 3M–N), with a frequency of 4.7 (2–7, sd= 1.0) rays per

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mm. Ray height is 193 (58–574, sd= 96) µm. Cross-fields are araucarioid with 5.7 (3–6,

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sd= 0.5), contiguous half-bordered pits (= oculipores) per cross-field (Fig. 3O–P, Fig. 4A).

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Cross-field pits are circular 8.7 (6.3–11.5, sd= 0.9) µm in vertical diameter.

182

Remarks. Agathoxylon kellerense is characterized by its distinct growth ring boundaries and

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araucarioid radial pitting with mostly bi- to triseriate pitting (Lucas and Lacey, 1981;

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Pujana et al., 2014, 2017). Seriation of radial pitting differentiates it from Agathoxylon

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antarcticus which has mainly uniseriate pitting (Pujana et al., 2014). Fossil-species of

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Araucariaceae-like wood have been historically classified by the number of vertical rows of

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tracheid pitting (e.g. Penhallow, 1907), along with other characters.

188

This fossil-species was first described from the King George (25 de Mayo) Island,

189

Antarctica, by Lucas and Lacey (1981) and later found in other localities of Antarctica and

190

Patagonia (Nishida et al., 1990; Mirabelli et al., 2017; Pujana et al., 2017).

191 192

Agathoxylon pseudoparenchymatosum (Gothan, 1908) Pujana, Santillana and Marenssi,

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2014

194

Fig. 5A–H

195

1908 Dadoxylon pseudoparenchymatosum Gothan, p. 10, pl. I, figs. 1–3, 12–16.

196

1914 Araucarioxylon novaezeelandii Stopes, p.348, pl. XX.

197

1919 Araucarioxylon kerguelense Seward, p. 185, fig. 714.

198

1921 Dadoxylon kerguelense (Seward) Edwards, p.614, pl. XXIII.

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1926 Dadoxylon kaiparaense Edwards, p. 127, figs. 11–13.

200

1970 Araucarioxylon chilense Nishida, p.14, pl. II, fig. 4.

201

1984 Araucarioxylon pseudoparenchymatosum (Gothan) Nishida, p. 89, pl. LXXXI.

202 203

New material. MPEF-Pb 10126.

204

Description. The specimen is pycnoxylic secondary xylem.Growth ring boundaries are

205

distinct, latewood with 1–3 rows of tracheids (Fig. 5A). The earlywood-latewood transition

206

is abrupt and the cells roundish to polygonal in transverse section with resin plugs in

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tracheids adjacent to the rays (Fig. 5B). Intertracheary pitting on radial walls is araucarian,

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uni- to triseriate, predominantly uniseriate (Si= 1.66), contiguous (Cp= 96.6%), and

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alternate when biseriate or triseriate (Fig. 5C–D). Intertracheary radial pits are circular to

210

hexagonal, 14.0 (12.0–16.8, sd= 1.0) µm in vertical diameter (Fig. 5C–D). Tracheid

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tangential diameter is 30.5 (19.5–41.9, sd= 5.9) µm. Pits on tangential walls are not

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observed. Horizontal and end walls of ray parenchyma cells are smooth. Mean ray height is

213

medium, 8 (3–19, sd= 3.85) cells high, almost exclusively uniseriate (Fig. 5E–F), and with

214

a frequency of 3.6 (2–6, sd= 0.9) rays per mm. Ray height is 192 (78–391, sd= 86) µm.

215

Resin plugs in tracheids adjacent to the rays (Fig. 5B, E–F), with variable heights, mostly

216

plate-like (Fig. 5E–F). Cross-fields are araucarioid with 6.2 (5–8, sd= 0.9), mostly

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contiguous pits per cross-field (Fig. 5G–H, Fig. 4A). Cross-field pits are half bordered (=

218

oculipores), circular, and 8.3 (6.2–9.9, sd= 100) µm in vertical diameter.

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Remarks. Agathoxylon pseudoparenchymatosum is characterized by its distinct to indistinct

220

growth ring boundaries, mainly uni- to biseriate araucarioid radial pitting, araucarioid

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cross-fields and presence of resin plugs. Occurrence of resin plugs differentiates it from

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Agathoxylon antarcticus (Pujana et al., 2014).

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This fossil-species is frequently found in South America and Antarctica (Gothan,

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1908; Seward, 1919; Kräusel, 1924; Nishida, 1970, 1981, 1984; Torres et al., 1994; Pujana

225

et al., 2014, 2015, 2017; Mirabelli et al., 2017).

226 227

Agathoxylon sp.

228

Fig. 5I–P.

229 230

New material. MPEF-Pb 10130.

231

Description. The specimen is pycnoxylic secondary xylem. Growth ring boundaries are not

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observed, probably because of the poor preservation of the specimen (Fig. 5I).

233

Intertracheary pitting on radial walls is uni- to biseriate, mostly uniseriate (Si= 1.39),

234

continuous (Cp= 100%), and alternate when biseriate (Fig. 5J–L). Intertracheary radial pits

235

are circular to hexagonal 11.3 (9.2–13.9, sd= 1.0) µm in vertical diameter. Tracheid

236

tangential diameter is 31.8 (21.1–44.6, sd= 5.3) µm. Pits on tangential walls are not

237

observed. Horizontal and end walls of ray parenchyma cells are smooth. Mean ray height is

238

medium, 8.5 (1–23, sd= 6.1) cells high, uniseriate to partially biseriate, rays uniseriate

239

(86%) or uniseriate with biseriate portions (14%) (Fig. 5M–O), with a frequency of 6.1 (4–

240

9, sd= 1.37) rays per mm. Ray height is 250 (42–557, sd= 145) µm. Only a few cross-fields

241

could be observed, apparently all araucarioid, with ca. 5–8 contiguous half-bordered pits

242

(oculipores) per cross-field (Fig. 5P, Fig. 4A).

243

Remarks. Araucarian tracheid radial pitting and araucarioid cross-field pits indicate an

244

affinity with Agathoxylon (Philippe and Bamford, 2008). Poor preservation of the sample

245

prevented the observation of the growth ring boundaries and allowed to observe only a few

246

cross-fields and other details. The most significant character of this specimen is the 14% of

247

partially biseriate rays. Araucarioxylon semibiseriatum Pant and Singh from the Permian of

248

India and Dadoxylon weavirense Maheshwari from the Permian of Falklands/Malvinas

249

Islands have frequently biseriate rays but they have mostly multiseriate radial pitting

250

(Maheshwari, 1972; Pant and Singh, 1987). Specimens studied by Lutz et al. (2001) from

251

the Triassic of Chile are very alike the specimen from Patagonia. They were assigned to A.

252

semibiseriatum but they do not have predominantly multiseriate radial pitting as the

253

holotype of that fossil-species from India

254 255

Agathoxylon?

256

Fig. 6A–H.

257 258

New material. MPEF-Pb 10114, 10120, 10128, 10129 and 10132–10134.

259

Description. The specimens are pycnoxylic secondary xylem. Most are poorly preserved,

260

and only a few characters could be observed confidently. In some specimens growth rings

261

boundaries are distinct (Fig. 6A) with earlywood-latewood transition abrupt, with 1–5 rows

262

of tracheids. In others they are apparently indistinct or absent (Fig. 6B) and the cells are

263

roundish to polygonal as seen in transverse section (Fig. 6B). All of them have araucarian

264

intertracheary radial pitting, mostly uni- to biseriate and alternate when biseriate (Fig. 6C–

265

E). Pits on tangential walls are not observed. Rays are uniseriate. Resin plugs and axial

266

parenchyma are not observed. Horizontal and end walls of ray parenchyma cells are

267

smooth. Mean ray height is very low to medium, exclusively uniseriate (Fig. 6F–H). Cross-

268

fields are not observed.

269

Remarks. The specimens assigned to this taxonomic unit are poorly preserved. However,

270

some diagnostic characters, like araucarian intertracheary radial pitting indicate similarities

271

and consistency with Agahoxylon.

272 273

Fossil-genus Brachyoxylon Hollick and Jeffrey, 1909

274

Type species. Brachyoxylon notabile Hollick and Jeffrey, 1909

275 276

Brachyoxylon raritanense Torrey, 1923

277

Fig. 7A–H.

278 279

New material. MPEF-Pb 10113 and 10122.

280

Description. Gymnosperm pycnoxylic secondary xylem with growth ring boundaries

281

indistinct (Fig. 7A), hardly observed macroscopically. Cells are roundish to polygonal as

282

seen in transverse section. Intertracheary pitting on radial walls is mixed, uniseriate (Si=

283

1.00), mostly contiguous (Cp= 60.9%) (Fig. 7B–D). Intertracheary radial pits are circular,

284

11.3 (7.5–16.2, sd= 1.4) µm in vertical diameter. Tracheid tangential diameter is 24.8

285

(13.9–27.4, sd= 4.2) µm. Pits on tangential walls are not observed. Horizontal and end

286

walls of ray parenchyma cells are smooth. Mean ray height is very low, 4.3 (1–11, sd=

287

2.16) cells high, uniseriate to partially biseriate (Fig. 7E–F), with a frequency of 5.6 (4–7,

288

sd= 0.8) rays per mm. Ray height is 91 (19–552, sd= 57) µm. Cross-fields with 6.7 (4–10,

289

sd= 2.1), contiguous half-bordered pits (= oculipores) per cross-field (Fig. 7G–H, Fig. 4B).

290

Cross-field pits are circular to elliptic 5.1 (3.2–7.3, sd= 0.8) µm in vertical diameter.

291

Remarks. The samples are assigned to Brachyoxylon because they have mixed radial pitting

292

arrangement and araucarioid cross-fields with several contiguous half-bordered pits

293

(Philippe and Bamford, 2008). The samples were compared with species of Brachyoxylon

294

in Table 2.

295

The most similar fossil-species is B. raritanense Torrey from the Cretaceous of

296

North America, which matches all the diagnostic characters (i.e. exclusively uniseriate

297

radial pitting, lack of axial parenchyma, ray height and seriation, etc., Torrey, 1923) with

298

the Patagonian samples. The description of Torrey (1923) is not very detailed (e.g. it lacks

299

many measurements). Tangential pits on the tracheids were described in the holotype

300

(Torrey, 1923), but they could not be observed in the new specimens (probably because of

301

the preservation). Brachyoxylon liebermanii Philippe from the Cretaceous of Europe also

302

shares the diagnostic characters (Philippe, 1995) with B. raritanense, indicating that these

303

two fossil-species are very similar. Kräusel (1949) synonymized B. raritanense with B.

304

notabile Hollick and Jeffrey. However B. notabile has axial parenchyma, traumatic canals

305

and biseriate pits (Hollick and Jeffrey, 1909) and we consider these differences enough for

306

separating those two fossil-species.

307 308

Brachyoxylon is associated with the family Cheirolepidiaceae, an extinct family of conifers (Alvin et al., 1981). This family was particularly diverse and abundant globally

309

during the Jurassic and Early Cretaceous with a wide range environments from flood plains

310

near river systems or lake margins to environments halophytic or xeric environments

311

(Alvin, 1982; Watson, 1988). Classopollis is the pollen type of the Cheirolepidiaceae and is

312

widely distributed (Alvin et al.1981; Alvin 1982; Zhou 1983; Machhour and Pons 1992;

313

Limarino et al. 2012) and is usually found in association with cones of Classostrobus

314

(Hieger et al., 2015). Leaves are also associated with this extinct family (e.g.

315

Brachyphyllum, Pseudofrenelopsis, Tomaxiellia) (Alvin, 1983; Villar de Seoane, 1998;

316

Moreno Sánchez et al., 2007; Sucerquia et al., 2015). In the Cretaceous of Patagonia, most

317

records of Cheirolepidiaceae are from leaves, cones and pollen (e.g. Archangelsky, 1963;

318

Traverso, 1966; Baldoni, 1978; Archangelsky et al., 1981, Escapa et al., 2012).

319

Brachyoxylon is widely distributed, however its species are mostly found in

320

northern hemisphere sediments (Table 2) (Hollick and Jeffrey, 1909; Philippe, 1995; Tian

321

et al., 2018). In Patagonia, it was found only in the Lower–Middle Jurassic and Lower

322

Cretaceous by Bodnar et al. (2013) and Vera and Césari (2015) respectively and it is

323

virtually absent in Antarctica, only one wood with a putative assignation to this fossil-

324

genus has been described (Torres et al., 1997a).

325 326

Cupressinoxylon?

327

Fig. 7I–P.

328 329

New material. MPEF-Pb 10121.

330

Description. Gymnosperm pycnoxylic secondary xylem with growth ring boundaries

331

indistinct to distinct, the number of tracheid rows of the latewood is difficult to count due to

332

the poor preservation of the specimen (Fig. 7I). Intertracheary pitting on radial walls is

333

abietinoid, uni- to biseriate, mostly uniseriate (Si= 1.35), mostly continuous (Cp= 70.1 %),

334

and opposite when biseriate (Fig. 7J–L). Intertracheary radial pits are circular, 15.5 (11.5–

335

18.4, sd= 1.6) µm in vertical diameter. Tracheid tangential diameter is 34.6 (26.9–45.8, sd=

336

5.02) µm. Pits on tangential walls are not observed. Horizontal and end walls of ray

337

parenchyma cells are smooth. Mean ray height is medium, 5.5 (1–19, sd= 3.6) cells high,

338

exclusively uniseriate (Fig. 7M–N), with a frequency of 4.7 (4–6, sd= 0.8) rays per mm.

339

Ray height is 128 (19–332, sd= 82) µm. Cross-fields with 1.2 (1–2, sd= 0.4), non-

340

contiguous and apparently are cupressoid half-bordered pits (= oculipores) per cross-field

341

(Fig. 7O–P, Fig. 4C). Cross-field pits are circular 11.3 (9.3–13.8, sd= 1.1) µm in vertical

342

diameter.

343

Remarks. The specimen has a poor preservation and many character details (i.e. radial

344

pitting, cross-field pits) were observed better with SEM. We consider that the wood has an

345

abietinean radial pitting arrangement because despite that most uniseriate and biseriate pits

346

are contiguous, when they are biseriate they are almost always circular and opposite (rarely

347

subopposite) and never alternate and hexagonal.

348

Cross-field pits are half-bordered, however the width of the border is not always

349

observed clearly, but seems to be wider than the aperture. Cupressinoxylon differs from

350

Podocarpoxylon mainly by the type of cross-field pits; Podocarpoxylon spp. have usually

351

cross-field pits that match the taxodioid type of IAWA Softwood Committee (2004) or

352

“podocarpoid” sensu other authors (see Pujana and Ruiz, 2017) cross-fields and

353

Cupressinoxylon has cupressoid cross-field pits. Similar fossil-species with usually one,

354

relatively large (mean diameter >10 um), half-bordered pit per cross-field from Patagonia

355

and Antarctica include:

356

1. Cupressinoxylon rotundum Pujana. This Antarctic fossil-species is very similar, but the

357

specimen from Patagonia lacks axial parenchyma (Pujana et al., 2017).

358

2. Ruiz et al., (2017) described C. austrocedroides Nishida from the lower Paleocene of

359

Patagonia. In these samples some of the horizontal walls of the ray parenchyma cells are

360

nodular and axial parenchyma is present.

361

3. Podocarpoxylon multiparenchymatoum Pujana and Ruiz from the Eocene, has clearly

362

taxodioid sensu IAWA Softwood Committee (2004) cross-field pits (half-borders of the

363

pits are thinner than the aperture and with a near to vertical aperture) and abundant axial

364

parenchyma (Pujana and Ruiz, 2017).

365

4. Circoporoxylon gregussii Del Fueyo of the Upper Cretaceous of Patagonia has uniseriate

366

to biseriate rays and axial parenchyma is present (Del Fueyo, 1998).

367

The type of cross-field of the sample is more similar to that of extant Podocarpaceae

368

rather than that of extant Cupressaceae which usually have more than one pit per cross-field

369

(Patel, 1967; Gajardo et al., 1998; Roig, 1992).

370

A few Cupressinoxylon species were found in Patagonia (e.g. Kräusel, 1924; Ruiz

371

et al., 2017). This fossil-genus includes species with affinity to the Cupressaceae or

372

Podocarpaceae (Vaudois and Privé, 1971; Pujana et al., 2017).

373 374

5. Discussion

375 376

The Lower Cretaceous of Gondwana is characterized by the diverse environments

377

caused by the opening of the Atlantic ocean and a change in ocean circulation (Scotese et

378

al., 1999). These paleogeographic changes in the Late Jurassic-Early Cretaceous originated

379

a small ice house in some regions of the planet including Patagonia (Scotese et al., 1999).

380

The paleoflora of the Tres Lagunas Formation would have developed in a paleolatitude

381

between 45º to 54º S according to the coral hermatipics fossils found in the same formation

382

associated with volcanic activity (Scasso and Kiessling, 2002).

383

Consequently, the paleoforest of Tres Lagunas would have developed in a volcanic

384

area. A similar scenario was described for the Early Cretaceous flora of the Livingston

385

Island, which developed in proximity to a volcanic arc at a paleolatitude of 62º (Falcon-

386

Lang and Cantrill, 2001). Based on the analysisof cuticles, during the middle Aptian and

387

the late Albian–early Cenomanian, Patagonian floras (e.g. cycads, bennettitaleans and

388

Cheirolepidiaceae) would have developed mainly in temperate-warm climates (Passalía,

389

2009). This was a result of the the expansion of tropical to subtropical paleofloras towards

390

high latitudes, which were found in South America, Antarctica and Australia (Iglesias et al.,

391

2011).

392

All the fossil woods of the studied assemblage have a conifer-like structure. It is

393

dominated by Araucariaceae-like woods (86%), followed by Brachyoxylon raritanense

394

with 9% (Cheirolepidiaceae), and Cupressinoxylon? with 5% (Fig. 8). Two samples were

395

assigned as “Gymnosperm indet.” because they are very poorly preserved (Fig. 8; Table 1).

396

The paleoforest of the Tres Lagunas Formation was dominated by Agathoxylon, a fossil-

397

genus with affinity to the Araucariaceae. However, older species of this genus, particularly

398

those form the Paleozoic, would have no relation to the family. The Araucariaceae is

399

particularly diverse and abundant in South America and Antarctica during the Jurassic and

400

Early Cretaceous (Philippe et al., 2004; Panti et al., 2012), which is consistent with the

401

proportions we obtained.

402

Fossil wood studies from the Lower Cretaceous of Patagonia are very scarce.

403

Therefore, the taxonomic proportions we obtained can not be compared with those previous

404

studies of fossil woods which were based only in one or very few samples. However, some

405

fossil wood studies from the Lower Cretaceous of Western Antarctica showed a dominance

406

of conifers over other gymnosperms (Torres et al., 1982; Philippe et al., 1995; Falcon-Lang

407

and Cantrill, 2001). In Byers Peninsula, Livingston Island, (Torres et al., 1982; Falcon-

408

Lang and Cantrill, 2001) and in Snow Island (Philippe et al., 1995; Torres et al., 1997a), in

409

outcrops of the Lower Cretaceous Cerro Negro Formation, fossil wood assemblages are

410

dominated by conifers, with Agathoxylon, Podocarpaceae and other putative fossil-genera.

411

However, in none of those studies a dominance of Agathoxylon was found, suggesting that

412

the Araucariaceae were more abundant in Patagonia than in Antarctica. In addition, non-

413

conifers woods were found in Antarctica, particularly Sahnioxylon (Torres et al., 1997a;

414

Falcon-Lang and Cantrill, 2001), which was not found in Patagonia until today.

415

The conifer-dominated forests indicated by the wood assemblage of Tres Lagunas

416

and the absence of cycads (which may have a low potential for fossilization) and other non-

417

conifer trunks like tree ferns differ in the proportions with the pollen and macrofloras

418

previously described from the Lower Cretaceous of the area (e.g. Baldoni, 1978;

419

Archangelsky et al., 1981). Baldoni and De Vera (1980) and Baldoni and Olivero (1983)

420

described Upper Jurassic-Lower Cretaceous fossil leaves assemblages from the Lake

421

Fontana area, about 50 km west from Tres Lagunas locality, which show a dominance of

422

ferns joined with equisetaleans, cycads, bennettitaleans, caytoniales and conifers. Other

423

similar leaf floras were found in the Lower Cretaceous of Patagonia (Baldoni, 1978, 1979):

424

Kachaike Fm. (Del Fueyo et al., 2007; Passalía, 2007a,b), Baqueró group (Archangelsky,

425

2001 and references therein), Springhill Fm. (Del Fueyo et al., 2007; Carrizo and Del

426

Fueyo, 2015), and in the Lower Cretaceous of the Antarctic Peninsula (Torres et al., 1997b;

427

Cantrill, 1998; Falcon-Lang and Cantrill, 2002). The studies from Patagonia indicate a

428

significant diversity of plants with local turnovers in the flora composition (Del Fueyo et

429

al., 2007). In most of the floras, conifers are not a dominant part of the vegetation (Baldoni,

430

1978).

431

The differences in the taxonomic composition between the wood flora from Tres

432

Lagunas and the other mentioned macrofloras can be explained by a local dominance of

433

Araucariaceae or by the fact that araucarias are low producers of leaf fossils, due to their

434

evergreen habit (Falcon-Lang, 2000) or because of the rate of preservation of their leaves.In

435

addtion, palynological studies from surface sediments and drill cores from localities near

436

Tres Lagunas, show a dominance of Classopollis of the Cheirolepidiaceae and

437

Callialasporites whose affinity is questioned between Araucariaceae and Podocarpaceae

438

(Batten and Dutta, 1997). Other pollen grains of the Araucariaceae, Araucariacites and

439

Cyclusphaera are infrequent (Archangelsky et al., 1981; Seiler and Moroni, 1984).

440

Growth rings with narrow latewood composed of only a few rows of cells may

441

indicate a little marked seasonality, typical of subtropical to tropical climates. However,

442

some conifers (as most of the Araucariaceae) have this type of growth rings because of

443

their evergreen habit (Falcon-Lang, 2000), and consequently we must be caution about this

444

deduction. In addition, Brison et al. (2001) recommended not to assure paleoclimatic

445

conclusions taken from Agathoxylon woods make.

446 447

6. Conclusions

448 449

Anatomical descriptions of the woods have shown that the woody plants of the area

450

consisted of Agathoxylon (Araucariaceae), Brachyoxylon (Cheirolepidiaceae) and probably

451

Cupressinoxylon (Cupressaceae or Podocarpaceae).

452

The generic proportions of the fossil woods indicate an Araucariaceae-dominated

453

forest. This is consistent with the fossil record, because the Araucariaceae reaches its major

454

diversity and abundance in South America and Antarctica in the Early Cretaceous (Panti et

455

al., 2012). However, coeval fossil leaf and pollen floras of the region and of Antarctica do

456

not indicate an Araucariaceae dominance.

457 458

Acknowledgments

459

The authors thank two anonymous reviewers and the editor for their suggestions

460

and corrections. Funds for this work were provided by PIP 2014-0259 granted to RRP by

461

Conicet and PUE 0098 granted to the MACN by Conicet. Ana Greppi is acknowledged for

462

her collaboration with the drawings.

463 464

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gymnosperm leaves of Patagonia, Argentina. Palaeogeography, Palaeoclimatology,

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669 670 671 672

Philippe, M., 2011. How many species of Araucarioxylon? Comptes Rendus Palevol 10, 201–208. Philippe, M., Bamford, M.K., 2008. A key to morphogenera used for Mesozoic conifer-like woods. Review of Palaeobotany and Palynology 148, 184–207.

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674

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680

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681

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682

Crétacé inférieur d’Asie du Sud-Est. Geodiversitas 33, 25–32.

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692

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693

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694

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717

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777

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784

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785

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786

Zamuner, A.B., Falaschi., 2005. Agathoxylon matildense n. sp., leño araucariáceo del

787

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788

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789 790

Zhou, Z., 1983. A heterophyllous conifer from the Cretaceous of east China. Palaeontology 26, 789–811.

791

Fig. 1. Stratigraphic table based on data compiled from Ploszkiewick (1987), Aguirre

792

Urreta and Rawson (1998), and Scasso and Kiessling (2002).

793 794

Fig. 2. Location map of the two outcrops.

795 796

Fig. 3. A–H, Agathoxylon antarcticus (Poole and Cantrill) Pujana, Santillana and Marenssi,

797

I–P, Agathoxylon kellerense (Lucas and Lacey) Pujana. A–B. Distinct to indistinct growth

798

ring boundaries in transverse section (TS). Bars: 200 µm. MPEF-Pb 10125 (A) and 10123

799

(B). C. Predominantly uniseriate radial pitting in a longitudinal radial section (RLS). Bar:

800

50 µm. MPEF-Pb 10125. D. Uni-biseriate radial pitting (SEM). Bar: 45 µm. MPEF-Pb

801

10117. E–F. Uniseriate rays (TLS). Bars: 200 µm (E) and 100 µm (F). MPEF-Pb 10115 (E)

802

and 10129 (F). G–H. Cross-fields (SEM). Bar: 20 µm. MPEF-Pb 10131 (G) and 10125 (H).

803

I. Distinct growth ring boundary (TS). Bar: 200 µm. MPEF-Pb 10118. J–L. Bi-triseriate

804

radial pitting (RLS). Bars: 100 µm (J, L) and 50 µm (K). MPEF-Pb 10135 (J, K) and 10118

805

(L). M–N. Uniseriate rays (TLS). Bars: 200 µm. MPEF-Pb 10118 (M) and 10119 (N). O–P.

806

Cross-fields (RLS). Bars: 50 µm. MPEF-Pb 10118 (O) and 10135 (P).

807 808

Fig. 4. Schematic draw of cross-fields. A. Agathoxylon. B. Brachyoxylon raritanense. C.

809

Cupressinoxylon?. All samples assigned to Agathoxylon have similar cross-fields.

810 811

Fig. 5. A–H, Agathoxylon pseudoparenchymatosum (Gothan) Pujana, Santillana and

812

Marenssi, MPEF-Pb 10126. I–P, Agathoxylon sp., MPEF-Pb 10130. A. Distinct growth

813

ring boundary (TS). Bar: 200 µm. B. Resin plugs in tracheids close to the rays (arrowhead)

814

(TS). Bar: 100 µm. C. Bi-triseriate radial pitting. Bar: 50 µm. D. Uniseriate radial pitting

815

(SEM). Bar: 40 µm. E–F. Uniseriate rays and resin plugs (arrowheads) (TLS). Bars: 200

816

µm (E) and 100 µm (F). G–H. Cross-fields. Bars: 50 µm. I. Traqueids in a transverse

817

section, growth rings boundaries not observed (TS). Bar: 200 mm. J–K. Uni-biseriate radial

818

pitting (SEM). Bars: 30 µm. L. Uni-biseriate radial pitting (RLS). Bar: 50 m. M–O. Rays

819

uniseriate and uniseriate with biseriate portions (TLS). Bars: 200 µm (M) and 100 µm (N,

820

O). P. Cross-fields (SEM). Bar: 20 µm.

821

822

Fig. 6. Agathoxylon?. A. Distinct to indistinct growth ring boundary (TS). Bar: 200 µm.

823

MPEF-Pb 10134. B. Tracheids (TS). Bar: 200 µm. MPEF-Pb 10133. C. Biseriate radial

824

pitting (RLS). Bar: 50 µm. MPEF-Pb 10128. D–E. Biseriate radial pitting (SEM). Bars: 30

825

µm (D) and 20 µm (E). MPEF-Pb 10114 (D) and 10120 (E). F–H. Uniseriate rays (TLS).

826

Bars: 200 (F, G) and 100 (H) µm. MPEF-Pb 10128 (F), 10114 (G) and 10129 (H).

827 828

Fig. 7. A–H, Brachyoxylon raritanense Torrey. I–P, Cupressinoxylon?, MPEF-Pb 10121.

829

A. Growth ring boundaries indistinct (TS). Bar: 500 µm. MPEF-Pb 10113. B–C. Uniseriate

830

mixed radial pitting (SEM). Bar: 40 µm. MPEF-Pb 10113. D. Uniseriate and contiguous

831

radial pitting. Bar: 40 µm. MPEF-Pb 10122. E–F. Uniseriate rays (TLS). Bars: 200 µm.

832

MPEF-Pb 10113. G–H. Cross-fields (SEM). Bar: 20 mm. MPEF-Pb 10122. I. Growth ring

833

boundary indistinct (TS). Bar: 200 µm. J. Uniseriate radial pitting. Bar: 50 µm. K. Uni-

834

biseriate radial pitting (RLS). Bar: 50 µm. L. Uniseriate radial pitting (SEM). Bar: 45 µm.

835

M–N. Uniseriate rays (TLS). Bars: 200 µm (M) and 100 µm (N). O–P. Cross-fields (SEM).

836

Bars: 20 µm.

837 838

Fig. 8. Circle with the proportions of the fossil-genera studied.

839 840

Table 1. List of studied specimens. Si and Cp indices are those of Pujana et al. (2016).

841

Abbreviations: VDRP= Vertical diameter radial pits; AP= Axial parenchyma; TTD=

842

Tracheid tangential diameter; NPxCF= Number of pits per cross-field; VDCFP= Vertical

843

diameter of cross-field pits; RH= Ray height; R x mm= Rays per mm. A= absent; ?=

844

unknown values; *= less than 15 measurements.

845 846

Table 2. Comparison of Brachyoxylon raritanense with other species of Brachyoxylon.

847

Abbreviations: GRB= Growth ring boundary; IPS= Intertracheary pitting seriation; PxCF=

848

Pit per cross-field; RS= Ray seriation; RH= Ray height; AP= Axial parenchyma; C=

849

Crassulae; RC= Resin canal; D= Distinct; I= Indistinct; A= Absent; P= Present; ?=

850

unknown; T= Traumatic; (T)= Rarely traumatic; e.g.: 1(2)s= Mainly uniseriate, rarely

851

biseriate pits. Bold letter indicates similarities with the Tres Lagunas samples. All the

852

authorities cites are in the references.

MPEF-Pb

Taxon

Si

Cp [%]

VDRP[µm]

AP

TTD [µm]

NPxCF [cells]

VDCFP [µm] 4.7

RH [cells] 4.3

RH [µm] 100.1

10113

Brachyoxylon raritanense

1.00

41.2

11.0

A

24.6

6.5

10114

Agathoxylon?

1.60

100.0

13.2

?

38.8

10115

Agathoxylon antarcticus

1.01

76.5

12.2

A

34.0

10116

Agathoxylon kellerense

2.01

100.0

12.7

A

31.8

10117

Agathoxylon antarcticus

1.74

100.0

12.8

A

42.6

R x mm

?

7.2*

8.4*

241.0*

4.8

5.5*

10.4*

5.5

101.0

6.1

6*

9.2*

6.8

138.7

5.4

5.3*

7.7

6.2

157.7

3.8

6.2*

10118

Agathoxylon kellerense

1.84

100.0

13.9

A

41.0

4.3

9.0

8.3

207.5

4.2

10119

Agathoxylon kellerense

2.00

100.0

16.0

A

39.8

6.3*

8.2*

13.0

264.6

4.3

10120

Agathoxylon?

2.08

100.0

13.2

?

?

?

?

5.0*

191.1*

4.6

10121

Cupressinoxylon?

1.35

88.3

15.5

A

34.6

1.2

11.3

5.5

127.7

4.7

10122

Brachyoxylon raritanense

1.00

80.6

11.6

A

25.0

6.8*

5.6

4.3

79.5

5.0*

10123

Gymnosperm indet.

1.00

100.0

13.5*

?

36.5*

?

?

?

282.5*

?

10124

Agathoxylon antarcticus

1.00

100.0

11.8

A

38.6*

5.0*

5.4*

8.2

153.6

4.7*

10125

Agathoxylon antarcticus

1.00

94.5

13.2

A

34.1

5.2*

6.1

9.0

176.2

6.6*

10126

1.66

96.6

14.0

A

30.5

6.2*

8.3

8.0

192.2

3.7

10127

Agathoxylon pseudoparenchymatosum Gymnosperm indet.

1.00*

100.0*

13.8*

?

29.3

?

?

3.0*

73.7*

5.1

10128

Agathoxylon?

1.55

100.0

12.0

?

?

?

?

8.4

197.3

5.3*

10129

Agathoxylon?

1.00

100.0

12.7

?

36.4

?

?

3.1

62.0

?

10130

Agathoxylon sp.

1.40

100.0

11.3

A

32.0

5.2*

?

8.5

250.7

6.1

10131

Agathoxylon antarcticus

1.00

79.5

12.5

A

40.1*

9*

6.0

5.1

126.1

5.3

10132

Agathoxylon?

1.00

100.0

11.4

?

33.6

?

?

6.5

173.1

?

10133

Agathoxylon?

1.77

100.0

12.0

?

?

?

?

6.5

202.0

4.8

10134

Agathoxylon?

2.0*

100.0*

14.8*

?

40.6

6*

5.8*

7.4

164.1

?

10135

Agathoxylon kellerense

2.33

100.0

12.2

A

43.4

6.7*

8.6

5.0

162.5

4.8

Fossil-species

Age

Country

GRB

IPS

PxCF

RS, RH[cells]

AP

C

RC

B. avramii Iamandei and Iamandei, 2005 B. baqueroensis Vera and Césari, 2015 B. comanchense Torrey, 1923 B. cristianicum Iamandei, Iamandei and Grǎdinaru, 2018 B. currumilii Bodnar, Escapa, Cúneo and Gnaedinger, 2013 B. dobroglacum Imandei and Iamandei, 2005 B. eboracense (Holden, 1913) Philippe, 2002 B. holvavicum Iamandei, Iamandei and Grǎdinaru, 2018 B. lagonense (Laoudouéneix, 1973) Dupéron-Laoudouéneix, 1991 B. liebermannii Philippe, 1995 B. notabile Hollick and Jeffrey, 1909 B. nummularium (White, 1908) Kurzawe, Iannuzzi and Merlotti, 2012 B. raritanense Torrey, 1923 B. saurinii Boreau and Serra, 1961 B. semibiseriatum (Pant and Singh, 1987) Kurzawe and Merlotti, 2010 B. serrae Philippe, Suttethorn and Buffetaut, 2011 B. trautii (Barale, 1981) Philippe, 1995 B. voisinii Thevenard, Philippe and Barale, 1995 B. woodworthianum Torrey, 1923 B. zhejiangense Tian, Zhu, Wang and Wang, 2018

Early Cretaceous Late Cretaceous Cretaceous Early Jurassic Early–Middle Jurassic Early Cretaceous Jurassic Early Jurassic Cretaceous Jurassic Late Cretaceous Permian Cretaceous Jurassic (?) Permian Early Cretaceous Middle Jurassic Jurassic Early Cretaceous Early Cretaceous

Romania Argentina USA Romania Argentina Romania England Romania Chad France USA Brazil USA Cambodia Brazil Thailand France France USA China

D D D D D D D D ? I D I I D D D D A D D

1–2s 1–3s 1–2s 1–2s 1–2s 1–3s 1–2s 1(2)s 2–3s 1s 1–2s 1–2s 1s 1–2s 1–5s 1–2s 1-2s 1s 1(2)s 1-2s

1–8 8–26 12 1–6 4–11 1–6 numerous cupressoid 1–9 cupressoid 5–12 cupressoid to podocarpoid 5–11 1–6 1–9 2–12 4–16 5–16 4–9 3-8 cupressoid 2–7

1(2)s, 1–21 1s, 1–9 1s, 1–6 1(2)s, 1–20 1s, 1–10 1s, 1–10 1s, low 1–2s, 1–25 1s, low 1s, low 1s, 1–8 1(2)s, 1–39 1s, 1–15 1s, 1–31 1s, 1–38 cells 1s, 1–15 1s, 1–10 1s, mean 5.8 1–4s, 1s high, 2–4s low 1(2)s, 1–16

B. raritanense, new samples

Early Cretaceous

Argentina

I

1s

4–10

1(2)s, 1–11

A A A P P P A A A A A A A A A A A A A A A

A A ? A A P A A A A P A A A A A A A A A A

T A T A A A A A (T) T A T A A T P T A A T A A

1

Highlights.

2

Fossil woods from the Tres Lagunas Fm. (Lower Cretaceous of Patagonia) are studied.

3

We found a total dominance of conifer-like woods.

4

Three fossil-genera were found (Agathoxylon, Brachyoxylon and Cupressinoxylon?).

5

Agathoxylon, related to the Araucariaceae, dominates the assemblage.

6

No conflict of interest.