From the early Miocene El Cien Formation, Baja California Sur, Mexico, a new Tapirira species is described. Among the diagnostic features that relate T. peninsularis Martínez-Cabrera & Cevallos-Ferriz sp. nov. with extant species of the genus are libriform septate fibers, radial canals with 2–4 layers of epithelial cells, and scanty paratracheal to vasicentric axial parenchyma. In order to establish similarity between wood of T. peninsularis and fossil and extant species of the genus, cluster and principal component analyses were carried out. Numerical analyses support that Tapirira peninsularis is distinct from other extant and fossil species of the genus. Quantitative characters like frequency of radial canals, diameter of fibres, vessel element lumen, and height and width of the rays with radial canals are important in distinguishing between these taxa. Though these wood characters are quantitative, they also have been useful in the recognition of two subgenera within the genus. Recognition of this new species, along with the fossil record of the group, and a phytogeographic analysis suggest a low latitude North American origin for the genus, and a subsequent introduction to southern latitudes.
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- Author or Editor: Sergio R.S. Cevallos-Ferriz x
Hugo I. Martínez-Cabrera and Sergio R.S. Cevallos-Ferriz
Sergio R. S. Cevallos-Ferriz and Ruth A. Stockey
Several anatomieally preserved twigs, a branehing speeimen and the wood of a large axis with affinities to Rosaeeae are deseribed from the Prineeton ehert (Middle Eoeene) of British Columbia, Canada. Speeimens are eharaeterised by a heteroeellular pith with a peri-medullary rone of thiek-walled oval eells and semi-ring-porous seeondary xylem with vertieal traumatie duets, fibres with eireular bordered pits, and mostly seanty paratracheal and oeeasionally apotracheal parenehyma. Ray to vessel pitting is similar to the alternate intervaseular pitting. Seeondary phloem is eomposed of tangentially oriented diseontinuous bands of alternating fibres and thinwalled eells. Seeondary eortical tissues are represented by a phelloderm eharaeterised by rectangular eells and phellern with rectangular eoneave eells. Anatomical variation between speeimens can be related to age of the woody axes. Juvenile and mature wood of this speeies differ in vessel arrangement and presenee of scanty paratracheal parenchyma in mature wood. Vessel elements are arranged in radial multiples, oeeasional clusters as well as solitary vessels. Tyloses and dark cellular contents are present mainly in mature wood. Some twigs have a heterocellular pith with a few scattered cells with dark contents or, occasionally, short irregular rows of these cells. In the branching specimen eells of this type also are organised in longer rows. Together, these anatomical features suggest that all specimens belong to the same taxon, Prunus allenbyensis Cevallos-Ferriz ' Stockey n. sp. Anatomy of this plant reinforces the interpretation of a subtropical to temperate climate during the time of deposition.
Sergio R. S. Cevallos-Ferriz and Josefina Barajas-Morales
Three types of fossil woods with similarities to the Leguminosae are described, Mimosoxylon tenax (Felix) Müller-Stoll ' Mädel, Bajacalijomioxylon cienense Cevallos-Ferriz ' Barajas-Morales, gen. et sp. nov., and Copaijeroxylon matanzensis Cevallos-Ferriz ' Barajas-Morales, sp. nov. These woods are from the EI Cien Formation in Baja California Sur, Mexico, which is dated as Zemorrian-Saucesian, i.e., late Oligocene–early Miocene. Although two of the names of the fossil woods suggest affinity with a particular extant taxon, differences in some quantitative and qualitative features preclude their identification with a single extant taxon. The similarity among wood of some groups of extant Leguminosae and limited knowledge of character variability in woods of this family explains this taxonomie uncertainty. These fossil woods from Baja California underscore the need for an extensive systematic study of the wood anatomy of Leguminosae, add to the poorly known plant history of the Peninsula, suggest a tropical South American influence in the fossil flora of Baja Califomia, and indicate that the climate during the Zemorrian- Saucesian was different from the xeric conditions that prevail today in the area.
Sergio R.S. Cevallos-Ferriz, Hugo I. Martínez-Cabrera and Laura Calvillo-Canadell
Fossil woods from the El Cien Formation have yielded important information on the taxonomic composition and climate of a flora established in the west coast of Mexico during the Miocene. This report of a new genus and species, Ruprechtioxylon multiseptatus Cevallos-Ferriz, Martínez Cabrera et Calvillo-Canadell, is based on woods with the following combination of features: vessels solitary and in radial multiples of 2–3; vestured, alternate, oval to polygonal intervessel pits; vessel-ray and vessel-parenchyma pits similar in size to intervessel pits, but with slightly reduced to reduced borders; 2–5 septa per fibre; scanty paratracheal, unilateral and vasicentric axial parenchyma; uniseriate homocellular rays, occasionally locally biseriate; crystals in fibres. The presence of Ruprechtioxylon (Polygonaceae) in the El Cien Formation confirms that plants of lineages growing today under contrasting climates lived together in the past. This record adds a new species to the growing list of Neotropical taxa that were present in Mexico prior to the great Plio-Pleistocene exchange of biota in the Americas.