IAWA Bulletin n. s., Vol. 11 (3), 1990: 261-280 VEGETATIVE REMAINS OF THE ROSACEAE FROM THE PRINCETON CHERT (MIDDLE EOCENE) OF BRITISH COLUMBIA by Sergio R. S. Cevallos-Ferriz * and Ruth A. Stockey Department of Botany, University of Alberta, Edmonton, Alberta, Canada T6G 2E9 Summary Several anatomieally preserved twigs, a interpretation of a subtropical to temperate branehing speeimen and the wood of a large climate during the time of deposition. axis with affinities to Rosaeeae are deseribed Key words: Rosaeeae, Prunoideae, Maloi­ from the Prineeton ehert (Middle Eoeene) of deae, Prunus, fossil wood, Middle Eo­ British Columbia, Canada. Speeimens are eene. eharaeterised by a heteroeellular pith with a peri-medullary rone of thiek-walled oval eells Introduction and semi-ring-porous seeondary xylem with The Middle Eoeene Princeton ehert local­ vertieal traumatie duets, fibres with eireular ity of British Columbia has a diverse permin­ bordered pits, and mostly seanty paratracheal eralised flora that includes vegetative and and oeeasionally apotracheal parenehyma. reproduetive organs of ferns, conifers, mono­ Ray to vessel pitting is similar to the alternate eotyledons and dieotyledons. Among dicoty­ intervaseular pitting. Seeondary phloem is ledonous plant reproductive organs are flow­ eomposed of tangentially oriented diseontin­ ers represented by Paleorosa similkameenen­ uous bands of alternating fibres and thin­ sis Basinger 1976 (Rosaceae), Princetonia walled eells. Seeondary eortical tissues are allenbyensis Stockey 1987 (incertae sedis), represented by a phelloderm eharaeterised by and a sapindaeeous flower (Erwin & Stockey rectangular eells and phellern with rectangular 1990). Fruits and seeds include Decodon al­ eoneave eells. Anatomical variation between lenbyensis Cevallos-Ferriz & Stockey 1988 speeimens can be related to age of the woody (Lythraeeae), Allenbya collinsonae Cevallos­ axes. Juvenile and mature wood of this spe­ Ferriz & Stockey 1989 (Nymphaeaeeae), and eies differ in vessel arrangement and pres­ Ampelocissus similkameenensis Cevallos­ enee of scanty paratracheal parenchyma in Ferriz & Stockey 1990a (Vitaceae). Addition­ mature wood. Vessel elements are arranged al flowers, fruits and seeds eurrently under in radial multiples, oeeasional clusters as weIl investigation eontinue to demonstrate that a as solitary vessels. Tyloses and dark cellular diverse angiosperm flora oeeurred here dur­ contents are present mainly in mature wood. ing the Middle Eocene. Some twigs have a heterocellular pith with a Although studies of angiosperms at this few scattered cells with dark contents or, loeality have coneentrated on reproduetive occasionally, short irregular rows of these structures, vegetative remains including the cells. In the branching specimen eells of this sterns, roots, and leaves are also weIl pre­ type also are organised in longer rows. To­ served in the chert. Their identification and gether, these anatomical features suggest that attachment to reproductive structures is es­ all specimens belong to the same taxon, Pru­ sential to the reeonstruetion of whole plants nus allenbyensis CevaIlos-Ferriz & Stockey and the understanding of their biology. Vege­ n. sp. Anatomy of this plant reinforces the tative axes from the Princeton ehert are repre- * Present address: Instituto de Geologfa, Universidad Naeional Aut6noma de Mexieo, Ciudad Universitaria, Apartado Postal 70-296,04510 Mexieo D.F., Mexieo. Downloaded from Brill.com09/26/2021 11:47:13AM via free access 262 IAWA Bulletin n.s., Vol. 11 (3), 1990 sen ted by a diverse array of twigs, branches Material and Methods and roots. The first angiosperm vegetative Seven rosaceous axes have been found in stern described from Princeton was Eorhiza the Princeton chert (Allenby Formation). The arnoldii, a dicotyledonous rhizome of un­ locality is 8.4 km south of Princeton, British certain affinities (Robison & Person 1973). Columbia on the east side of the Similkameen Recently, Cevallos-Ferriz & Stockey (1990b) River. Fossils occur in a seetion consisting of described Liriodendroxylon allenbyensis, of an interbedded sequence of chert and coal the family Magnoliaceae, based on several with an occasional thin ash bed replacing a twigs and one branching specimen. They chert layer. Forty-nine exposed layers of noted that many of the vegetative axes in the chert have been recorded and systematical­ chert have weil preserved phloem, cortex, ly sampled (Stockey 1987). The locality has epidermis and/or periderm. These authors been referred to as locality 'I' (Boneham stressed the importance of extraxylary tissues 1968) and the 'Princeton chert locality' in the identification of the Princeton fossil (Basinger 1976; Stockey 1984, 1987). The twigs, especially phloem and primary cortical Allenby Formation of the Princeton Group tissues, since some characteristics of juvenile has been dated as Middle Eocene based on wood differ in mature wood (Page 1979). palynology (Rouse & Srivastava 1970), Rosaceous leaf rernains have been reported mammals and fishes (Russell 1935; Gazin from Cretaceous sediments (Hughes 1976), 1953; Wilson 1977, 1982), and potassium­ but it is not until the early Tertiary that flow­ argon dating (Hills & Baadsgaard 1967). ers and fruits are found (Dorofeev 1963; Ba­ Fossils are preserved as silica perminerali­ singer 1976). During the early Tertiary Ro­ sations. All chert blocks were cut into slabs saceae underwent an important adaptative and studied in serial seetions using a modi­ radiation forming a characteristic component fied cellulose acetate pe el technique and of the broad-leaved deciduous vegetation hydrofiuoric acid (Joy et al. 1956; Basinger (Wolfe 1987). Rosaceous remains ofMiddle & RothwellI977). Peel seetions were mount­ Eocene age from the northwestern United ed in Eukitt or Coverbond xylene soluble States and southwestern Canada occur at mounting medium for microseopie exarnina­ severallocalities from Princeton and Joseph tion. Creek, British Columbia, and Republic, In addition to taxa described in the pub­ Washington (Wolfe & Wehr 1988). From lished literature, twigs of extant Crataegus these 10calities about 40 taxa have been iden­ punctata Jacq. (ALTA 10621, UAPC-ALTA tified based on leafremains (Wolfe & Wehr SI 1827), and Prunus pennsylvanica L. (AL­ 1988). Among these leaves are members of TA 72159, UAPC-ALTA SI 1828) were the subfamilies Spiraeoideae, Maloideae, Ro­ compared anatomically to the fossil wood. soideae, and Prunoideae. Rosaceous flowers Wood was dehydrated in 10%, 30%, and from the Princeton chert, Paleorosa similka­ 50% EtOH followed by a tert-butyl alcohol meenensis Basinger (1976), has now been series (Johansen 1940). Paraplast Plus me­ shown to be a member of the subfamily Spi­ dium was used for infiltration and embed­ raeoideae, tribe Sorbarieae (Cevallos-Ferriz ding. Seetions 10-13 ~m thick were cut on a et al. 1990). rotary microtome and stained with safranin­ In the present study a new species, Prunus fast green. allenbyensis Cevallos-Ferriz & Stockey n. sp. The wood identification process was aided (Rosaceae) is described based on vegetative by the computer-assisted identification sys­ stern and wood remains. Anatomical differ­ tem GUESS v. 1.1 and NCSU wood data­ ences in axes of several ages are compared to base (Wheeler et al. 1986; LaPasha & Wheeler similar types of variation seen in extant trees. 1987). All averages represent aseries of 25 This provides the basis for understanding separate measurements (Carlquist 1988). some differences between the anatomy of All specimens are housed in the Uni ver­ young sterns, twigs and more mature wood sity of Alberta Paleobotanical Collection of this fossil plant. (UAPC-ALTA). Downloaded from Brill.com09/26/2021 11:47:13AM via free access Cevallos-Ferriz & Stockey - Eocene Prunus allenbyensis 263 Systematic description thin cuticle. Secondary phloem with alternat­ ing discontinuous bands of tangentially ori­ Class: Magnoliopsida ented fibres and thin-walled cells. Dilated Order: Rosales phloem rays, one to several cells wide, with Farnily: Rosaceae dark contents. Phelloderm up to three cells Subfarnily: Prunoideae thick of rectangular cells. Phellern of concave Genus: Prunus L. cells up to five cells thick. Species: Prunus allenbyensis Cevallos-Ferriz et Stockey n. sp. Description Five twig fragments, averaging 1.0 x 0.7 Etymology - The specific epithet allen­ x 4.0 cm (Fig. 1), a larger branch, 2.3 x 2.0 byensis refers to the abandoned rnining town x 9.3 cm (Fig. 2), and one wood fragment, of Allenby near which the Princeton chert 10- more than 9.4 cm in diameter (Fig. 10; > 16 cality is found. years) have been found in the chert. Anatom­ Holotype - P1095 A (Figs. 14,24,26), ical similarities in primary and secondary tis­ B (Figs. 17, 19,22), P1095 C (Figs. 2,4, sues of all of these vegetative remains enable 9, 11, 13, 15, 16, 23, 25), D (Fig. 8); us to interpret them as belonging to a single Paratypes - Pl184 B (Figs. 1,7); Pl235 taxon. A (Figs. 3, 6, 10,21), D (Figs. 12, 18,20); PlnO C (Fig. 5). Anatomy 0/ the first five growth increments Diagnosis - Pith composed of thin-wall­ Primary tissues - The twigs and the ed polyhedral cells and smaller polyhedral branching specimen are characterised by the thick-walled cells with dark contents either presence of a heterocellular pith and tangen­ organised in rows or scattered at centre, and tially arranged vertical traumatic ducts in the a peri-medullary zone of thick-walled oval secondary xylem. Most pith cells are