Celtis popsii, Wheeler & Manchester, 2021

Wheeler, Elisabeth A. & Manchester, Steven R., 2021, A Diverse Assemblage Of Late Eocene Woods From Oregon, Western Usa, Fossil Imprint 77 (2), pp. 299-329 : 304-305

Celtis popsii sp. nov.

Text-fig. 2a–f

H o l o t y p e. Designated here. UF 279-34460 (Textfig. 2a–f). Minimum estimated axis diameter 28 cm.

P l a n t F o s s i l N a m e s R e g i s t r y N u m b e r.

PFN002695 (for new species).

R e p o s i t o r y. Paleobotany Collections , Florida Museum of Natural History , Gainesville, Florida, USA .

E t y m o l o g y. Named in honor of Raymond “Pops” Shepherd, who loved and respected the natural beauty of our earth, father of Mark Shepherd, generous supporter of the J. C. Raulston Arboretum.

T y p e l o c a l i t y. UF 279. About 3 km east of Post,

Crook County, Oregon, USA.

Type stratum and age. John Day Formation, Eocene.

D i a g n o s i s. Growth rings distinct, wood ring-porous to semi-ring-porous, earlywood zone with multiple rows of earlywood vessels, latewood vessels in diagonal-tangential arrangement. Perforations simple. Intervessel pitting crowded alternate; vessel-ray pitting oval with reduced borders. Axial parenchyma paratracheal, vasicentric to confluent. Rays <10-seriate, heterocellular, sheath cells present.

D e s c r i p t i o n. Growth rings distinct. Wood ringporous to semi-ring-porous.

Earlywood zone 2–4(4+) rows deep with vessels solitary and in radial multiples of 2–3. Latewood vessels in radial multiples and clusters arranged diagonally and in tangential bands ( Text-fig. 2a, b ). Tangential diameter of earlywood vessels 126 (18), 88–166 µm; perforations exclusively simple; intervessel pits crowded alternate, mostly polygonal in outline ( Text-fig. 2c ), medium-large, 7–11; vessel-ray parenchyma pits oval in outline, not crowded, borders slightly reduced ( Text-fig. 2d ); vessel element lengths average 380 (141) µm; thin-walled bubble-shaped tyloses present.

Fibers mostly non-septate, possibly a few septate, pits not observed, likely thick-walled.

Axial parenchyma vasicentric-confluent ( Text-fig. 2a, b ), strands mostly of 4 cells.

Rays 1–5(–6) cells wide; tendency to two size classes as 2–3-seriate rays are rare, sheath cells present in most of the wider rays ( Text-fig. 2e, f ); heterocellular with procumbent body cells and 1–2(–5) marginal rows of square and upright cells. Multiseriate ray height average 737 (169) µm; 4–6/ mm. Possibly crystals in somewhat enlarged upright marginal ray parenchyma cells.

C o m p a r i s o n s w i t h e x t a n t w o o d s.A search of InsideWood for the combination: wood not diffuse-porous (5e), tangential bands of vessels (6p), simple perforation plates (13p), alternate intervessel pitting that is not small to minute (22p 24a 25a), non-septate fibers (66p), vasicentric parenchyma (79p), heterocellular rays of two size classes (103p 104a 105a) with sheath cells (110p) only returned species of Celtis (Cannabaceae) . If vessels in a diagonal arrangement (7p) is used instead of vessels in a tangential arrangement, again only Celtis has that combination of features.

Celtis is a widespread genus with ca. 60 species, mostly trees, that occurs in temperate and tropical regions (Africa, Asia, Central and South America, North America, Southern Europe; Sattarian 2006, Mabberley 2017). InsideWood includes coded descriptions of 25 species and images of 22 species.

There is variation in porosity within the genus, and sometimes within a species, related to geography, climate, and leaf retention. Typically, tropical species are diffuseporous, e.g., C. africana BURM. f. , C. gomphophylla BAKER , and C. mildbraedii ENGL. (Africa) and C. schippii STANDL. (Central and South America), while temperate species are ring-porous, e.g., C. laevigata WILLD. , C. occidentalis L. (North America), C. bungeana BLUME , C. sinensis PERS. (temperate Asia), as well as C. australis L. (Mediterranean region). Celtis pallida TORR. , a shrub to small tree native to dry regions of southwest North America, extending to Central and South America, is semi-evergreen and diffuseporous to somewhat semi-ring-porous ( Sweitzer 1971, Wheeler et al. 1988, Zhong et al. 1992, Wood Identification Database Team, FFPRI accessed 2020–2021, InsideWood 2004-onwards). The Asian C. philippensis BLANCO is diffuse-porous in tropical regions and semi-ring- to ringporous in more seasonal environments ( Zhong et al. 1992). One sample each of C. laevigata (BWCw 8303, Florida, USA), C. laevigata var. reticulata (TORR.) L.D.BENSON (SJRw 40228, Texas, USA), and C. biondii PAMP. (CAFw 20246, Jiangxi, southeast China) were semi-ring-porous, rather than ring-porous.

Present-day ring-porous Celtis species usually have only 1–2 rows of earlywood vessels. However, some samples of C. occidentalis (BWCw 8272; BWCw 8456; FPAw 9598), and C. sinensis (TWTw 23448) have multiple rows of earlywood vessels. Ring-porous Celtis generally have wider rays (to 12-seriate) than diffuse-porous species (to 8-seriate, but mostly 1–5-seriate). The anatomy of this Post Hammer wood with its tendency to semi-ring-porosity and rays to 5–6-seriate suggests it grew in a seasonal environment, but one not as pronounced as North Temperate Celtis species experience today.

C o m p a r i s o n s w i t h f o s s i l w o o d s. Apparently, the three generic names – Celtisoxylon T.TRIVEDI ( Trivedi 1971), Celtixylon GREGUSS (Greguss 1943) , Celtoxylon WURZINGER ( Wurzinger 1953) – created for fossil woods thought to resemble Celtis – were not properly diagnosed ( Gregory et al. 2009). Celtisoxylon was applied to a wood from Deccan Intertrappean beds of India but was only mentioned in an abstract without diagnosis or designation of holotype, Celtixylon was never formally diagnosed, and Celtoxylon was used in a thesis, but not formally published.

Woods thought to have affinities with Celtis have been reported from the Miocene of temperate Europe and Asia. Selmeier (1989, 2015) described Celtixylon cristalliferum A.SELM. from the lower and middle Miocene of Germany and compared it to C. palaeohungaricum GREGUSS and C. campestre (E.HOfM.) GREGUSS from the Miocene of Hungary. These latter two species had rays up to 10–12 cells wide, while the widest rays of C. cristalliferum were 6–7-seriate. Celtixylon cristalliferum differs from Celtis popsii because it has a narrower earlywood pore zone with 1–2 (3) rows of large vessels, less well-defined sheath cells in the rays, and not as obvious a tendency to two size classes of rays. The illustration of the Celtixylon sp. (probable Miocene age) that Gottwald (2004) described also shows only 1–2 rows of large earlywood pores.

As detailed above, Celtis popsii differs from other fossil wood species thought related to Celtis and has wood anatomical features that fall within the range of and are unique to Celtis , so we assign it to the genus. To the best of our knowledge, this is the only fossil Celtis wood known from North America.

C o - o c c u r r i n g f r u i t s / s e e d s. To date, there is no record of Celtis in the fruit/seed assemblage of locality UF 279.

Figures

Text-fig. 2. Celtis popsii sp. nov., UF 279-34460. a: Growth ring with earlywood of multiple rows of vessels solitary and in radial multiples; latewood vessels in wavy tangential bands, TS. b: Growth ring boundary, latewood vessels in multiples with axial parenchyma confluent, TS. c: Simple perforation plates, alternate intervessel pits, polygonal in outline, TLS. d: Vessel-ray parenchyma pits to right of VRP, oval in outline, with slightly reduced borders, RLS. e: Rays tending to two sizes, some multiseriate rays with distinct sheath cells, multiseriate rays usually with 1 marginal row of square to upright cells, occasionally with 4 or more; uniseriate rays less than 10 cells high, TLS. f: Detail of multiseriate ray with distinct sheath cells, vessel element end walls, TLS. Scale bars: 200 µm in a, e; 100 µm in b; 50 µm in c, f; 20 µm in d.