Cercidiphyllum alalongum R.A.SCOTT et E.A.WHEELER, 1982

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 : 305-306

Cercidiphyllum alalongum R.A.SCOTT et E.A.WHEELER, 1982

Text-fig. 3a–h

M a t e r i a l. A single specimen (UF 279-24543) with an estimated minimum diameter of 8.8 cm.

D e s c r i p t i o n. Growth rings distinct, marked by bands of radially narrow fibers, difference in vessel diameter between latewood and earlywood vessels of successive rings ( Text-fig. 3a, b ). Wood diffuse-porous.

Vessels predominantly solitary ( Text-fig. 3a, b ), mean tangential diameter 59 (12) µm, 32–86 µm; 82–95–102/ mm 2; perforations all scalariform, 28–47 fine bars (Textfig. 3c); intervessel pits rare, opposite to scalariform (Textfig. 3e); vessel-ray parenchyma pits scalariform; vessel element lengths 980–1,400 µm; tyloses not observed. Faint helical thickenings occasionally observed in vessel element tips ( Text-fig. 3d ).

Fibers non-septate, thick-walled, small (2–3 µm) bordered pits observed on radial walls of some fibers.

Axial parenchyma rare.

Rays 1–2(–3)-seriate, uniseriate portions frequently alternating with multiseriate portions, occasionally width of the uniseriate and multiseriate portions similar ( Text-fig. 3f, g ), markedly heterocellular with upright cells often 2× the height of the procumbent cells ( Text-fig. 3h ), procumbent cells with relatively thick walls and richly pitted, upright and square cells with relatively thin walls; uniseriate rays exclusively of upright and square cells, usually less than 10 cells high; ~12 rays per mm.

Crystals not observed.

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. The combination of diffuse-porous wood (5p), exclusively solitary vessels (9p), scalariform perforation plates with more than 20 bars (17p), opposite-scalariform pits (22a – alternate pits absent), narrow numerous vessels (42a 43a 46a 47a 48a – absence of both medium-wide vessels and fewer than 40 vessels per mm 2), long vessel elements (54p), fibers with bordered pits (62p), axial parenchyma rare-absent (75p), rays 1–3-seriate (97p) and heterocellular rays (104a 105a) occurs in the saxifragalean families Altingiaceae ( Liquidambar L.), Cercidiphyllaceae (Cercidiphyllum) , and Hamamelidaceae ( Corylopsis SIEBOLD et ZUCC. ). Sakala and Privé-Gill (2004) discussed how to distinguish woods of these three genera and concluded that Cercidiphyllum consistently had more bars per perforation plate (to>40 bars) than the other two genera. Based on their criteria this wood has affinities with the Cercidiphyllaceae . Scott and Wheeler (1982) detailed differences between the ray structure of Cercidiphyllum and Corylopsis : rays in Cercidiphyllum have more than two alternating 1-seriate and 2–3-seriate portions and in some rays the 1-seriate and 2–3-seriate portions are of equal width.

Comparisons with fossil woods. Sakala and Privé-Gill (2004) reviewed the occurrences of Cercidiphyllum- like wood and recognized only two species: Cercidiphylloxylon kadanense U.PRAKASH, BŘEZINOVÁ et BŮŽEK ( Prakash et al. 1971) from the Czech Republic, and Cercidiphylloxylon spenceri (D.W.BRETT) H.L.PEARSON from the Paleocene of Scotland and the Eocene London Clay ( Brett 1956, Pearson 1987). Subsequently, Guo et al. (2010) assigned a sample from the Paleocene of China to Cercidiphylloxylon spenceri , and again reviewed the occurrences and criteria for recognizing wood of Cercidiphyllaceae .

Pearson (1987) and Crawley (1989) suggested the Clarno Nut Beds wood Cercidiphyllum alalongum R.A.SCOTT et E.A.WHEELER ( Scott and Wheeler 1982) should be included in Cercidiphylloxylon spenceri ( Pearson 1987) . Ray structure is notorious for its variability, especially differences between juvenile wood and mature wood. Nonetheless, we consider the Nut Beds Cercidiphyllum distinct from the European Cercidiphyllum -like woods, which do not have alternating uniseriate and multiseriate parts. The Chinese sample does, but the parts are not of equal width. Helical thickenings in vessel element tails were not reported for the European or Chinese woods. Admittedly, the preservation of those specimens does not appear to be as good as the Oregon specimens, so helical thickenings might have been difficult to observe.

R e m a r k s. Leaves and fruits with features unique to Cercidiphyllum are not known prior to the Oligocene, although extinct genera attributed to the family are widespread in the Paleocene and Eocene (e.g., Crane and Stockey 1985). This was a major part of the rationale Sakala and PrivéGill (2004) used for assigning the Nut Beds and London Clay Cercidiphyllum -like woods to Cercidiphylloxylon , i.e., these Eocene woods predate the occurrence of “real” Cercidiphyllum . However, the Oligocene Cercidiphyllumlike woods, which are of an age when there is “real” Cercidiphyllum also were placed in Cercidiphylloxylon . It is a matter of opinion, but we do not think there are significant anatomical differences between the Paleocene, Eocene, or Oligocene Cercidiphyllum- like woods and present-day Cercidiphyllum and do not think it necessary to assign the Paleogene woods to Cercidiphylloxylon rather than Cercidiphyllum . This “disconnect” between fossil woods resembling the present-day Cercidiphyllum and fruits that do not may be an example of mosaic evolution within the Cercidiphyllaceae .

C o - o c c u r r i n g f r u i t s / s e e d s. By “real” Cercidiphyllum , we refer to occurrences of fruits with follicles borne in sessile clusters, in association with leaves closely resembling those of extant Cercidphyllum japonicum . Such fossils occur only a few km from the UF 279 wood locality, but in overlying strata considered to be lower Oligocene ( Meyer and Manchester 1997). Brown (1935) used a broader concept of the genus Cercidiphyllum , incorporating fossil infructescences with fruits borne in racemes rather than clusters, associated with Trochodendroides E.W.BERRY leaves which are similar to the leaves of extant Cercidiphyllum . Today such infructescences are usually placed in the extinct genus Jenkinsella E.REID et M.CHANDLER (syn. Nyssidium auct non HEER) ( Golovneva and Alekseev 2017). In Central Oregon, Jenkinsella infructescences are known from the Hancock Canyon site ( Wheeler and Manchester 2014).

Figures

Text-fig. 3. Cercidiphyllum cf. alalongum R.A.SCOTT et E.A.WHEELER, UF 279-24543. a, b: Diffuse-porous wood, exclusively solitary vessels, axial parenchyma rare, thick-walled fibers, TS. c: Scalariform perforation plate with more than 30 bars, RLS. d: Helical thickenings (HT) in vessel element tip, RLS. e: Opposite to scalariform intervessel pits, RLS. f, g: Heterocellular rays 1–2 cells wide, occasionally uniseriate and biseriate portions of similar width, TLS. h: Ray with alternating rows of procumbent and upright (-square) cells, RLS. Scale bars: 200 µm in a; 100 µm in b, f; 50 µm in c, g, h; 20 µm in d, e.