Pérez-Lara et IAWAal. – Eocene Journal Anacardiaceae 38 (4), 2017: 543–552from Chiapas, Mexico 543 A new genus of Anacardiaceae fossil wood from El Bosque Formation (Eocene), Chiapas, Mexico Diana K. Pérez-Lara1, Carlos Castañeda-Posadas1, and Emilio Estrada-Ruiz2,* 1Benemérita Universidad Autónoma de Puebla, Facultad de Ciencias Biológicas, Blvd. Valsequillo y Av. San Claudio, Edificio BIO-1, Ciudad Universitaria, 72570 Puebla, México 2Laboratorio de Ecología, Departamento de Zoología, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Prolongación de Carpio y Plan de Ayala s/n, 11340 Ciudad de México, México *Corresponding author; e-mail: [email protected] ABSTRACT We describe a new fossil wood from the El Bosque Formation (Eocene) in Chiapas, southern Mexico. It has a combination of features found in the Anac- ardiaceae, including distinct growth rings, diffuse porosity, vessels solitary and in radial multiples of 2–3, simple perforation plates, medium to large alternate intervessel pits, vessel-ray parenchyma pits rounded and elongate with reduced borders, septate and non-septate fibers, axial parenchyma scanty paratracheal, vasicentric, apotracheal diffuse, Kribs heterogeneous rays type IIA, and mul- tiseriate rays with radial canals. The mosaic of features of this wood supports the erection of a new genus, Bosquesoxylon Pérez-Lara, Castañeda-Posadas et Estrada-Ruiz. This new genus of anacardiaceous fossil wood extends our knowl- edge of this family’s history and offers hints on the possible relationships with floras from other localities worldwide, especially North America and Asia. Keywords: Anacardiaceae wood, Bosquesoxylon, Eocene, Chiapas, Mexico. INTRODUCTION Anacardiaceae is a family with around 75 genera and 1000 species, represented by trees, shrubs and some woody climbers, with a wide distribution in tropical and warm-tem- perate regions (Mabberley 2008). In Mexico, there are ~62 extant species distributed in 20 genera, including some trees of economic importance, e.g., Spondias purpurea L. (jocote) (Martínez-Millán & Cevallos-Ferriz 2005; Medina-Lemus & Fonseca 2009). Anacardiaceae have an abundant fossil record. Fossils of the family have been reported worldwide, principally in America and Asia. In a literature review, Ramírez- Garduño (1996) listed ~120 fossil species in 30 genera, and that number has recently in- creased. In Mexico, several anacardiaceous macrofossils have been described, including flowers, leaves and woods. An Oligocene wood resembling Loxopterygium Hook. f. from Coayuca de Andrade, Puebla (Méndez-Cárdenas et al. 2014); Oligocene-Miocene flower and wood of Tapirira (Miranda 1963; Martínez-Cabrera & Cevallos-Ferriz 2004, respectively). Leaves and/or leaflets of Pseudosmodingium Engl., Haplorhus © International Association of Wood Anatomists, 2017 DOI 10.1163/22941932-20170179 Published by Koninklijke Brill NV, Leiden Downloaded from Brill.com10/06/2021 01:24:04AM via free access 544 IAWA Journal 38 (4), 2017 Engl., Rhus L., Comocladia L., and Pistacia L. from the Oligocene Los Ahuehuetes locality Tepexi de Rodríguez in Puebla (Ramírez et al. 2000; Ramírez & Cevallos- Ferriz 2002). The record of anacardiaceous fossil woods is rich, with approximately 78 wood types reported worldwide (e.g., Awasthi 1966; Gregory et al. 2009). The majority of the records are from Cenozoic sediments of Europe, Asia, and North and South America (Martínez-Cabrera & Cevallos-Ferriz 2004; Gregory et al. 2009). The oldest known ana- cardiaceous woods are Anacardiaceoxylon semecarpoides Prakash & Dayal (1964), and Dracontomeloxylon palaeomangiferum Prakash from the latest Cretaceous-earliest Paleocene Deccan Intertrappean Beds of India (Bande & Khatri 1980; Wheeler et al. 2017). The Deccan sample of Lanneoxylon grandiosum that Srivastava and Guleria (2004) described has features of both the Anacardiaceae and Burseraceae clade of the Sapindales (Wheeler et al. 2017). Recently, Estrada-Ruiz et al. (2010) described wood resembling Anacardiaceae /Burseraceae from the late Campanian of the Olmos Formation. We describe a new genus and species of Anacardiaceae from the El Bosque Formation (Eocene). Bosquesoxylon represents the oldest record of radial canals in Mexico. This new fossil wood further supports the hypothesis that Mexico has been a diversification center of the Anacardiaceae since the Paleogene, as suggested by its extant and fossil diversity in Mexico. MATERIALS AND METHODS Fossil wood was collected from a single outcrop locality of the El Bosque Formation. The locality is known as “Las Maderas Acala” and is located approximately 10 km southeast of the county seat Acala, Chiapas, Mexico (92°43'47" N and 16°30'41" W) (Fig. 1). -93° -92° -92° -92° -92° 16° 16° 16° 16° 16° 16° 16° 16° 16° 16° Figure 1. Location of the fossiliferous outcrop. -93° -92° -92° -92° -92° Downloaded from Brill.com10/06/2021 01:24:04AM via free access Pérez-Lara et al. – Eocene Anacardiaceae from Chiapas, Mexico 545 The Bosque Formation has been dated as Eocene. This formation consists of a sequence of ~37 meters of strata and is a rhythmic sequence of siltstones, shales, cal- careous sandstones, and occasional polymictic conglomerates. The Bosque Formation has yielded invertebrate fossils such as gastropods, bivalves, echinoderms, some verte- brates (e.g., sharks and turtles), calcareous algae, leaf impressions, and permineralized woods (Juárez-Hernández 2014). These sediments belong to a continental sedimentary environment marked by marine transgressions and regressions (Juárez-Hernández 2014). In some studies, this formation is divided as the El Bosque (lower Eocene) and San Juan (middle Eocene) Formations (Frost & Langenheim 1974; Müllerried 1982; Ferrusquía et al. 2000). The wood described herein was found in sediments within the El Bosque Formation. We prepared transverse (TS), tangential (TLS), and radial (RLS) sections using standard thin section techniques. The descriptions use terminology from the IAWA Hardwood List (IAWA Committee 1989). Affinities were determined by consulting the literature (e.g., Metcalfe & Chalk 1950; Détienne & Jacquet 1983; Ilic 1987, 1991; Terrazas 1994, 1999; Terrazas & Wendt 1995), and by using the multiple entry key of InsideWood, a wood anatomy website (InsideWood 2004-onwards; Wheeler 2011). For the classification of ray types, we employed the terminology proposed by Kribs (1935). Anacardiaceae has mostly heterogeneous rays (Kribs’s Types IIA and IIB). In the heterogeneous Type IIA, the uniseriate rays are composed of upright cells, and the multiseriate portions of multiseriate rays are composed mostly of procumbent cells with short uniseriate wings of upright cells. In the heterogeneous Type IIB, the uniseriate rays are of two types: composed of upright cells or composed of procumbent cells. Multiseriate portions are composed mostly of procumbent cells and have very short uniseriate wings composed of upright cells (Kribs 1935; Carlquist 2001). The speci- mens described here are housed in the Colección de Paleontología, from Benemérita Universidad Autónoma de Puebla, Puebla, Mexico. SystematiC DESCRIPTION Core Eudicots Malvids – Eurosids II Order – Sapindales Family – Anacardiaceae Genus – Bosquesoxylon Pérez-Lara, Castañeda-Posadas et Estrada-Ruiz, gen. nov. Species – Bosquesoxylon chiapiasense Pérez-Lara, Castañeda-Posadas et Estrada- Ruiz, sp. nov. Etymology – The generic name refers to the Formation, where the material was collected. The specific epithet refers to Chiapas State, Mexico, where the El Bosque Formation is found. Holotype hic designatus – BUAPALV 1536 A, B and C. Age – Eocene. Material – Description based on a single mature wood sample of permineralized float wood, about 7.7 cm in width and 13.6 cm long. Estimated original axis diameter of ~60 cm. Downloaded from Brill.com10/06/2021 01:24:04AM via free access 546 IAWA Journal 38 (4), 2017 Figure 2. Bosquesoxylon chiapasense Pérez-Lara, Castañeda-Posadas et Estrada-Ruiz, gen. et sp. nov. (BUAPALV 1536). – A: Diffuse porous wood (TS). Scale bar = 300 μm. – B: Solitary vessel, scanty paratracheal parenchyma, and growth ring boundary marked by latewood fibers (arrows) (TS). Scale bar = 100 μm. – C: Simple perforation plate; polygonal and alternate intervessel pits (TLS). Scale bar = 92 μm. – D: Axial parenchyma strand (arrows; F = fibers) (RLS). Scale bar = 16 μm. – E: Multiseriate rays (TLS). Scale bar = 100 μm. – F: Vessel-ray parenchyma pits circular, angular, and horizontally elongated with reduced borders (RLS). Scale bar = 23 μm. – G: Septate fibers (arrows) (TLS). Scale bar = 20 μm. – H: Heterocellular rays and a radial canal (TLS). Scale bar = 100 μm. – I: Heterocellular rays (RLS). Scale bar = 100 μm. – J: Showing three radial canals in a ray (TLS). Scale bar = 100 μm. – K: Prismatic crystals (arrow) (RLS). Scale bar = 30 μm. → Diagnosis – Distinct growth ring boundaries marked by radially narrowed latewood fibers; vessels solitary and in radial multiples of mainly 2 to 3; intervessel pitting alter- nate; vessel-ray and vessel parenchyma pits with reduced borders, horizontally elongated to round; non-septate and septate fibers, 1–2 septa per fiber; axial parenchyma mostly scanty paratracheal, also apotracheal diffuse, vasicentric; heterocellular rays, Kribs type IIA, ray body composed entirely of procumbent cells, and usually one marginal row of erect or square cells; radial canals in some multiseriate rays. Description in IAWA feature numbers: 1, 5, 13, 22, 23, 26, 27, 31, 42, 47, 56, 65,