Late Pleistocene), Entre Ríos, Argentina

Soledad RamosIAWA et al. Journal– Pleistocene 35 (2), Peltophoroxylon 2014: 199–212 from Argentina 199

A new fossil wood of Peltophoroxylon (Leguminosae: Caesalpinioideae) from the El Palmar Formation (late Pleistocene), Entre Ríos, Argentina

R. Soledad Ramos1,2,*, Mariana Brea1,3 and Romina Pardo4 1Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción (CICyTTP- CONICET), Dr. Matteri y España SN, E3105BWA, Diamante, Entre Ríos, Argentina 2FONCyT - Agencia Nacional de Promoción Científica y Tecnológica 3CONICET - Consejo Nacional de Investigaciones Científicas y Técnicas 4Cátedra de Dasonomía, Facultad de Ciencias Naturales, Universidad Nacional de Salta, Avenida Bolivia 5150, 4400 Salta, Argentina *Corresponding author; e-mail: [email protected]

abstract This paper describes the first record ofPeltophoroxylon (Ramanujam) Müller- Stoll et Mädel 1967 from the late Pleistocene of Argentina. The fossil specimens were recovered from the Colonia Ayuí and Punta Viracho fossil localities of the El Palmar Formation, located in the middle part of the Uruguay Basin, eastern Argentina. The diagnostic features are: growth ring boundaries demarcated by marginal parenchyma, medium-sized vestured intervessel pits, vessel-ray parenchyma pits similar in size and shape to intervessel pits, vasicentric to lozenge type aliform axial parenchyma, biseriate (70%) and uniseriate (30%) homocellular rays, non-septate and septate fibers, and long chains (10+) of prismatic crystals in chambered axial parenchyma cells. These features suggest a relation- ship with Peltophorum (Vogel) Benth. (Leguminosae: Caesalpinioideae). The vessel diameter and vessel density of the El Palmar woods are consistent with the temperate-warm, humid-semiarid climate inferred for this region during the late Pleistocene. Keywords: Wood anatomy, Peltophoroxylon, Pleistocene, Uruguay Basin, Argentina. INTRODUCTION

Today, the Fabaceae or Leguminosae includes approximately 730 genera and over 19,400 species worldwide (Lewis et al. 2005). The subfamily Caesalpinioideae, contain- ing approximately 2,250 species in 171 genera (Bruneau et al. 2008), is paraphyletic, and it includes the monophyletic tribes Cercideae and Detarieae and the paraphyletic tribes Cassieae and Caesalpinieae (Lewis et al. 2005). The South American extant flora includes 65 genera of Caesalpinioideae (Zuloaga & Morrone 1999; Ulibarri 2008) and inhabits tropical and subtropical areas, from rain forests, evergreen or deciduous forests, to savannas, semi-deserts and high mountains (Ulibarri 2008). In South America there are 31 genera in the tribe Caesalpinieae. Brazil has the highest concentration of endemics at the genus levels (Bruneau et al. 2008; Ulibarri 2008).

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Figure 1. Location map showing Colonia Ayuí and Punta Viracho fossil localities.

South America has an extensive and diverse legume fossil record, and woods with affinities to all subfamilies are reported (see Pujana et al. 2011). Worldwide, the old- est putative fossil wood assigned to the subfamily Caesalpinioideae is from the late Cretaceous of Africa and resembles the modern tribe Cassieae (Wheeler & Baas 1992). South American fossil woods that seem reliably assigned to the Caesalpinioideae are reported from the Miocene onwards (Pons 1980; Martínez & Rodriguez Brizuela 2011; Brea et al. 2012; see Pujana et al. 2011). The El Palmar Formation is well known for its rich fossil wood and phytolith assemblages. Taxa in these assemblages are interpreted to be trees, shrubs and herbs belonging to the Lauraceae, Fabaceae, Podostemaceae, Myrtaceae, Combretaceae, Anacardiaceae, Poaceae, Cyperaceae and Arecaceae (Zucol et al. 2005; Brea et al. 2010; Brea & Zucol 2011; Patterer & Brea 2011; Patterer 2012; Ramos et al. 2012). The Leguminosae from the El Palmar Formation include five Mimosoideae:Menen - doxylon areniensis, M. mesopotamiensis, M. piptadiensis, Mimosoxylon caccavariae, Prosopisinoxylon castroae, and two Papilionoideae: Holocalyxylon cozzoi and Am- buranoxylon tortorellii (Lutz 1979; Brea 1999; Zucol et al. 2005; Brea et al. 2010). The new fossil wood described herein represents the first report of fossil wood with affinities to Caesalpinioideae from the Uruguay Basin.

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STUDY AREA AND GEOLOGICAL SETTING Fossil woods were collected in the Colonia Ayuí and Punta Viracho localities of the El Palmar Formation. This fluvial unit is located in the southernmost part of the Uruguay Basin, in eastern Argentina (Fig. 1). The El Palmar Formation consists of medium, reddish and yellowish ochre sands, medium-to-thick sandstone layers with planar stratification and lenses of gravel and pebbles. Sand strata and gravel lenses represent channel facies, while fine sediments represent floodplain facies. This formation, which is 3 to 12 m thick, is found at the modern surface and has not been buried since its deposition (Iriondo 1980; Iriondo & Kröhling 2008; Kröhling 2009). At Federación city in Argentina, this formation was dated to 80,670 ± 13,420 years BP by TL (thermoluminescense dating) (Iriondo & Kröhling 2001), while near to the city of Salto in Uruguay, it was dated to 88,370± 35,680 years BP (Iriondo & Kröhling 2008).

MATERIALS AND METHODS Two fragments of wood were found in sediments of the El Palmar Formation (Iriondo 1980; Iriondo & Kröhling 2008; Kröhling 2009). One specimen (CIDPALBO-MEG 111) was collected by Cristina Vassallo de Cettour from the Colonia Ayuí locality. The other specimen (CIDPALBO-MEG 148) was collected by one of the authors (MB) from the Punta Viracho locality, both from Entre Ríos Province, Argentina (Fig. 1). Both specimens are silicified. The CIDPALBO-MEG 111 wood is 27 cm long and 12 cm in diameter and CIDPALBO-MEG 148 wood is 7.6 cm long and 4.2 cm in diameter. Thin sections were made using standard petrographic techniques. Anatomical terms used in this paper generally follow the recommendations of the IAWA List of Microscopic Features for Hardwood Identification (IAWA Committee 1989), with some terms also taken from Chattaway (1932), Kribs (1935) and Carlquist (2001). The bibliographic lists by Gregory (1994) and Gregory et al. (2009) were used. To compare the samples to extant and fossil species, we used the InsideWood website (InsideWood 2004-onwards; Wheeler 2011) and descriptions by Metcalfe and Chalk (1950), Cozzo (1951), Tortorelli (1956), Gasson et al. (2003, 2009) and Evans et al. (2006). Pardo (2012) studied the wood anatomy of extant Peltophorum dubium. The samples she studied are deposited in the Laboratorio de Anatomía Vegetal, Facultad de Ciencias Naturales, Universidad Nacional de Salta, Argentina (LANAVE). Systematic assignment follows APG (2009). Names used are as found in The Interna- tional Plant Names Index (The Plant List 2010) and the Index Nominum Genericorum (ING) (Farr & Zijlstra 1996). The quantitative values in the anatomical description are averages of 25 measure- ments, in all cases the average is cited first, followed by the minimum and maximum values, which are given in parentheses. The material was studied with a Nikon Eclipse E 200 light microscope, and photomicrographs were taken with a Nikon Coolpix S4 digital camera. The fossil specimen and microscope slides are deposited in the Labo- ratorio de Paleobotánica (CICyTTP-CONICET), Diamante, Argentina, under the acro- nym CIDPALBO-MEG for wood specimens and CIDPALBO-MIC for slides.

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RESULTS Fabales Bromhead 1838 Leguminosae Jussieu 1789 Caesalpinioideae de Candolle1825 Genus: Peltophoroxylon (Ramanujam) Müller-Stoll et Mädel 1967 Type species: Peltophoroxylon variegatum (Ramanujam) Müller-Stoll et Mädel 1967 Species: Peltophoroxylon uruguayensis Ramos, Brea et Pardo, sp. nov. (Fig. 2 & 3) Specific diagnosis – Growth rings distinct, demarcated by narrow (less than 3 cells wide) marginal parenchyma bands of only a few cells wide; diffuse porous; vessels solitary and in radial multiples of 2–4, rarely in clusters, circular to oval in outline, medium to small in diameter with thin walls; perforation plates simple; intervessel pits alternate, vestured and small to medium; vessel-ray pits similar in size and shape to intervessel pits; gums or other deposits present; axial parenchyma scanty paratracheal, vasicentric, and aliform, diffuse parenchyma scarce; fibers mostly non-septate, rarely septate; rays mostly biseriate and occasionally uniseriate, homocellular composed exclusively by procumbent cells; prismatic crystals in long chains in chambered axial parenchyma cells. Holotype – CIDPALBO-MEG 111 specimen, CIDPALBO-MIC 1368 (three microscope slides). Type locality – Colonia Ayuí, Entre Ríos, Argentina. Paratype – CIDPALBO-MEG 148 specimen, CIDPALBO-MIC 1571 (three microscope slides). Locality – Punta Viracho, Entre Ríos, Argentina. Horizon – upper part of the El Palmar Formation. Age – late Pleistocene. Etymology – Specific epithet, uruguayensis, refers to the region where the fossil specimens were found. Botanical affinity– Leguminosae-Caesalpinioideae, more closely with Peltophorum (Vog.) Benth. Repository – Colección Laboratorio de Paleobotánica, CICyTTP-CONICET, Dia- mante, Entre Ríos, Argentina. Description – Growth rings distinct, demarcated by narrow marginal parenchyma bands of only a few cells wide (Fig. 2.1, 2.4, 3.2). Wood diffuse porous (Fig. 2.1, 2.4).

← Figure 2. Peltophoroxylon uruguayensis Ramos, Brea et Pardo, sp. nov. (Caesalpinioideae). CIDPALBO-MEG 111 (1, 2); CIDPALBO-MEG 148 (3, 4, 5, 6). – 1: Distinct growth rings, vessels solitary and in short radial multiples; axial parenchyma in marginal bands (arrow). – 2: Detail of vessel elements (arrow). – 3: Rays uniseriate and biseriate. – 4: Vessels solitary and in radial multiples, vasicentric and confluent axial parenchyma (arrow). – 5: Vessel elements with oblique or straight end walls, parenchyma strand (arrow). – 6: Detail of vasicentric to confluent axial parenchyma (arrow). — Cross section (CS): 1, 4, 6; tangential section (TLS): 3, 5; radial section (RS): 2. – Scale bars: 1 = 500 µm; 2 & 4 = 200 µm; 3 & 6 = 100 μm; 5 = 50 µm.

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Vessels solitary (50%), and in radial multiples of 2–4 (46%), rarely in clusters (4%), circular to oval in outline in cross section (Fig. 2.1, 2.4, 2.6). Tangential diameter 127 (76−190) μm, radial diameter of 130 (57−187) μm, 15 (12–18)/mm2, walls 11 (7−15) μm thick. Vessel elements short, 205 (158–266) μm long. Perforation plates exclusively simple with straight to slightly oblique end walls (Fig. 2.2, 2.5, 3.6). Intervessel pits alternate, vestured, small to medium, 6 (4–8) μm, with slit-like apertures (Fig. 3.6, 3.7). Vessel-ray parenchyma pits similar in size and shape to intervessel pits (Fig. 3.8). Brownish yellow deposits present, abundant (Fig. 2.1, 2.4, 2.6). Axial parenchyma scanty paratracheal, vasicentric, aliform, occasionally confluent (Fig. 2.1, 2.4, 2.6), also in narrow marginal bands (Fig. 2.1, 3.2), rarely diffuse. Strands of 3–4 cells (Fig. 2.5). Prismatic crystals in long chains of chambered axial parenchyma cells, one crystal per chamber (Fig. 3.3). Rays mostly biseriate (70%) and occasionally uniseriate (30%). Ray width 17 (10–25) μm (Fig. 2.3, 3.5); ray height 210 (140–305) μm, 18 (10–25) cells. Rays homocellular, composed exclusively of procumbent cells (Fig. 3.1, 3.4); 15 (13−18) rays per mm. Dark deposits in many rays (Fig. 3.1, 3.3, 3.5). Fibers thick-walled (2−5 μm), polygonal in outline (Fig. 3.2), usually non-septate, rarely septate (Fig. 3.4, 3.5); diameter 12 (8–15) μm. Pits not observed. Storied structure not observed.

DISCUSSION

Comparison with extant species The following combination of features was used to determine the affinities of these woods: wood diffuse porous, vessels solitary and in radial multiples, simple perforation plates, vestured alternate intervessel pits, vessel-ray pits similar to intervessel pits; vessel element lengths short to medium, rays uniseriate to biseriate, usually low and mostly homocellular; axial parenchyma predominantly vasicentric, and crystals in chambered axial parenchyma cells (Cozzo 1950, 1951; Metcalfe & Chalk 1950; Baretta-Kuipers 1981; Wheeler & Baas 1992; Evans et al. 2006). The woody Fabaceae are characterized by the presence of diffuse porous wood, vessels with simple perforation plates, vestured alternate intervessel pitting (except in some caesalpinioid species), vessel elements of medium to short length, vessels solitary and in radial multiples, sometimes with clusters. Diagonal–tangential vessel

← Figure 3. Peltophoroxylon uruguayensis Ramos, Brea et Pardo, sp. nov. CIDPALBO-MEG 111 (2, 3, 8); CIDPALBO-MEG 148 (1, 4, 5, 6, 7). – 1: Detail of homocellular rays. – 2: Detail of marginal axial parenchyma (arrow) – 3: Detail of dark deposits in rays and prismatic crystals in chambered axial parenchyma cells (arrow). – 4: Detail of septate fiber (arrow). – 5: Detail showing biseriate ray with dark deposits and septate fiber (arrow). – 6: Alternate intervessel pits with slit-like apertures and vessel elements with oblique or straight end walls (arrow). – 7: Detail of alternate vestured pits. – 8: Detail of the vessel-ray parenchyma pits similar and smaller than the intervessel pits. — Cross section (CS): 2; tangential section (TLS): 3, 5, 6; radial section (RS): 1, 4, 7, 8. – Scale bars: 1 = 25 µm; 2–6 = 20 µm; 7 & 8 = 10 µm.

Downloaded from Brill.com10/05/2021 09:13:16AM via free access 206 IAWA Journal 35 (2), 2014 arrangement is occasional in Caesalpinioideae. Rays are usually low and made up primarily or entirely of procumbent cells. The parenchyma is commonly abundant and paratracheal. The vessel-ray pits are similar to the intervessel pits. Storied structure is present in most Papilionoideae, many Caesalpinioideae but hardly any Mimosoideae and crystals in chambered axial parenchyma cells are usually present (Baretta-Kuipers 1981; Wheeler & Baas 1992). Many of the aforementioned characters above also occur in the Combretaceae, Anacardiaceae, Rutaceae, Meliaceae, Sapindaceae and Apocy- naceae. However, co-occurrence of vestured pits and homocellular rays in the wood fossil indicates it likely is a legume (Wheeler & Baas 1992). The species of the Caesalpinioideae subfamily have medium to thick fiber walls, aliform, confluent and marginal axial parenchyma, homocellular rays or rays with a row of square or upright marginal cells, non-storied biseriate rays and prismatic crystals in chambered axial parenchyma cells (Wheeler & Baas 1992; Espinoza de Pernía & León 2002; Espinoza de Pernía & Melandri 2006a, 2006b). These features are more common in the Caesalpinioideae, but they also occur in the Mimosoideae subfamilies. The InsideWood database was searched to obtain a list of extant species of the New World with the following combination of features that occur in the fossil wood: 5p 6a 7a 8a 9a 10a 11a 12a 13p 14a 22p 24a 27a 29p 30p 79p 80p 83p 89p 92p 97p 104p 118a 120a 136p 142p 164a 168a 171a 175a 178a 181a with 0 allowable mismatches (see coding in IAWA Committee 1989). According to the results of this search, the fossil woods were compared with the following taxa, features that distin- guish them from Peltophoroxylon uruguayensis sp. nov. are given for each: Albizia spp. size of the intervessel pits, fiber wall thickness, number of cells per parenchyma strand and ray width; Enterolobium cyclocarpum (Jacq.) Griseb. has crystals in chambered fibers (Evans et al. 2006); Inga rubiginosa (Rich.) DC. and Inga splendens Willd. have exclusively septate fibers (Evans et al. 2006); Leucaena canescens Benth. with vessels of two distinct diameter classes, occasionally vessels in tangential bands and septate fibers;Marmaroxylon spp. and Senna galeottiana H.S. Irwin & Barneby, size of the intervessel pits and the type of axial parenchyma; Parapiptadenia rigida (Benth.) Brenan has heterocellular and/or homocellular rays; Prosopis juliflora (Sw.) DC. has larger rays commonly 4- to 10-seriate; Dicymbe bernardii R.S. Cowan has homocellular and heterocellular rays and prismatic crystals in upright and/or square ray cells; Melanoxylon brauna Schott has axial parenchyma and/or vessel elements storied and rays and/or axial elements irregularly storied. In addition, three species of American Caesalpinia: C. echinata Lam., C. cacalaco Humb. et Bonpl. and C. pulcherrima (L.) Sw. showed some similarities to the fossil wood described herein. Peltophoroxylon uruguayensis sp. nov. differs from Caesalpinia echinata because this extant species generally has storied rays and prismatic crystals in procumbent ray cells (Détienne & Jacquet 1983). Caesalpinia cacalaco differs because it has prismatic crystals in rays and occasionally marginal upright cells, in the number of vessels per mm2, and length of the vessel elements (>350 μm) (Gasson et al. 2009; InsideWood 2004-onwards). Caesalpinia pulcherrima has radial multiple vessels with ≥4 elements, vessel element lengths ≥350 μm, and heterocellular rays (Gasson et al. 2009).

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The fossil woods share many characters with Peltophorum dubium as described by Tortorelli (1956), Kribs (1968), Détienne and Jacquet (1983), Nardi Berti and Edlmann Abbate (1992), InsideWood (2004-onwards) and Pardo (2012). A list of these shared features follows. Wood diffuse porous, vessels solitary and in radial multiples, dark deposits in many vessels, small to medium intervessel pits alternate, vestured, with slit-like apertures, vessel-ray parenchyma pits similar to intervessel pits, perforation plates exclusively simple. Axial parenchyma vasicentric, aliform, confluent and marginal and rarely apotracheal. Axial parenchyma strands of 3–4. Rays mostly biseriate and occasionally uniseriate, homocellular, prismatic crystals in chambered axial parenchyma.

Comparison with fossil woods The legume family is well represented in the fossil record worldwide from the late Cretaceous to Pleistocene (Herendeen et al. 1992; Pujana et al. 2011), particularly in tropical and subtropical areas of Africa and South America (Rundel 1989; Bolzon & Marchiori 2002; Pujana et al. 2011). In South America, the fossil legume woods have an extensive and diverse temporal and spatial record, from the Paleocene (Danian) (Brea et al. 2008) to the Pleistocene, and from northern Colombia (c. 4° N) to southernmost Patagonia (c. 51° S) in Argentina (Pujana et al. 2011). The fossil wood described herein was compared with eleven fossil genera (Mussa 1959; Gregory et al. 2009) assigned to the Caesalpinioideae: Caesalpinioxylon Schenk 1890 (19 species); Cynometroxylon Chowdhury & Ghosh 1946 (14 species); Zollerni- oxylon Mussa 1959 (2 species, South America, Pleistocene); Pahudioxylon Chowdhury et al. 1960 (22 species); Afzelioxylon Louvet 1965 (5 species); Copaiferoxylon Müller- Stoll & Mädel 1967 (8 species); Pterogynoxylon Müller-Stoll & Mädel 1967 (1 species, southern India, Cenozoic); Cassinium Prakash 1973 (16 species); Acrocarpoxylon Gottwald 1994 (2 species, South Central Asia, Miocene); cf. Hymenolobium Pons & De Franceschi 2007 (1 species, South America, Miocene) and Peltophoroxylon Ramanujam (Müller-Stoll & Mädel 1967) (6 species). The differences between the Argentinian wood described herein and ten of these genera follow. Caesalpinioxylon has short to medium vessel element lengths, mainly solitary vessels, axial parenchyma confluent and banded, uniseriate rays that are heterocellular and usually storied (Schenk 1890; Müller-Stoll & Mädel 1967). Cynometroxylon has 1–3-seriate heterocellular rays, which usually are storied (Chowdhury & Ghosh 1946). Zollernioxylon has storied rays and axial parenchyma (Mussa 1959). Pahudioxylon has predominantly biseriate or triseriate rays as well as larger rays that commonly are > 4-seriate rays, occasionally rays are storied (Chowdhury et al. 1960). Afzelioxylon has septate fibers, and rays, axial parenchyma and vessel elements are commonly storied (Louvet 1965). Copaiferoxylon has regular axial canals. Pterogynoxylon Müller-Stoll & Mädel 1967 has prismatic crystals in rays and storied rays and axial parenchyma. Cassinium has rays 1–4- (mostly 3–4-)seriate, which are homocellular to weakly heterocellular and occasionally storied (Prakash 1973). Acrocarpoxylon has heterocellular rays and prismatic crystals in upright and/or square ray cells (Gottwald 1994). cf. Hymenolobium has crystals in fibers (Pons & De Franceschi 2007).

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The structure of the fossil woods agrees with the features of the genus Peltophor- oxylon (Ramanujam 1960; Müller-Stoll & Mädel 1967). The diagnostic features of this genus are vessels solitary and in short radial multiples, medium-sized in cross section; perforation plates simple; axial parenchyma vasicentric, aliform, occasionally confluent and in marginal bands; homocellular rays and rarely heterocellular with one row of upright marginal cells, 1–5-seriate, partially storied and septate fibers. The fossil woods from El Palmar Formation differ from previously described Peltophoroxylon and so are assigned to a new species, Peltophoroxylon uruguayensis Ramos, Brea et Pardo. Peltophoroxylon indicum (Central South Asia, Miocene; Müller-Stoll & Mädel 1967) and Peltophoroxylon embergeri (tropical mainland Africa, Miocene; Lemoigne 1978) have multiseriate rays that commonly are more that 4-seriate. The relatively wide rays in these Asian and African fossils might indicate that they are not Peltophoroxylon. Peltophoroxylon variegatum (Central South Asia, Miocene; Müller-Stoll & Mädel 1967) and P. parenchymatosum (Southeast Asia and Pacific, Miocene; Kramer 1974) have heterocellular storied rays. The last species is a synonym of Cassinium parenchymatosum (Kramer 1974; Guleria et al. 2001). Peltophoroxylon cassioides (Central South Asia, Miocene; Prakash & Awasthi 1969) has 1–3-seriate rays and lacks marginal axial parenchyma. Peltophoroxylon ferrugineoides (Central South Asia, Miocene; Bande & Prakash 1980) has exclusively uniseriate rays and septate fibers.

Biogeography of Peltophorum Peltophorum today has a pantropical distribution with 2 species native to the Neo- tropics: Peltophorum dubium in E Brazil, N Uruguay, NE Argentina, Paraguay, Bolivia and the Carribbean and Peltophorum venezuelense Cardenas, Rodriguez & Varela de Vega, restricted to Venezuela and probably is conspecific withP. dubium. Peltophorum africanum Sond. is native to South Africa and P. pterocarpum (DC.) K. Heyne is native to Asia (Occhioni 1981; Haston et al. 2005; Lewis et al. 2005). Globally, Peltophorum occurs in semi-arid, succulent-rich, tropical dry forest, bush- land and thicket vegetation, which is poor in understory grasses and lacks tolerance to fire disturbance. Schrire et al. 2005 called this distribution pattern the Succulent (S) biome. Pennington et al. 2004 described the Neotropical Succulent regions as Seasonally Dry Tropical Forests (SDTFs). Such habitats represent the remnants of a persistent dry vegetation type that was linked in the Cenozoic, from circum-Amazonian South America through Central America, Mexico and the Caribbean, along the Tethys seaway to Africa, Arabia and India. Peltophorum is one of the genera with pantropical intercontinental disjunction and exhibits a discontinuous distribution in tropical Asia, Africa and South America (Lewis et al. 2005; Schrire et al. 2005) and is adapted to a wide range of environmental conditions (Occhioni 1981).

CONCLUSION The new fossil wood, Peltophoroxylon uruguayensis sp. nov., described herein, consti- tutes the first fossil record of the Caesalpinioideae subfamily in the eastern Argentina. The occurrence of this fossil record in the El Palmar Formation supports the idea that the genus Peltophorum was present in this region since at least the late Pleistocene.

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Peltophoroxylon uruguayensis sp. nov. has mesomorphic features (vessel diameter and vessel density), indicating that this specimen would had lived in more humid areas and/or areas with greater soil humidity. Also, this record indicates a warmer climate during this time interval. Sedimentological data (Iriondo & Kröhling 2008; Kröhling 2009) and phytolith assemblages (Zucol et al. 2005; Patterer 2012) have suggested a temperate-warm, humid-semiarid climate during the late Pleistocene. The fossil woods studied here increases our knowledge of the fossil record of the tribe Caesalpinieae. In addition, the report of this Pleistocene record adds new information for future research regarding the biogeography of this tribe.

ACKNOWLEDGEMENTS

The authors would like to express their thanks to three reviewers and for their valuable help in provid- ing critical and constructive comments on a previous version of this manuscript. Their observations have substantially improved the text. We are also grateful to the Editor, Elisabeth Wheeler for her observations, comments, correction the English text and for her constructive criticism of the manuscript. RSR and MB thank Cristina Vassallo de Cettour, who found one of the fossil wood specimens in Colonia Ayuí (Entre Ríos, Argentina). We are also grateful to Mirta Terán for her help and assistance. This work was financially supported by Agencia Nacional de Promoción Científica y Tecnológica (ANPCyT) PICT 2008 N° 0176.

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Accepted: 21 November 2013

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