Celtis

Tiffney, Bruce H. & Manchester, Steven R., 2022, The Early Middle Eocene Wagon Bed Carpoflora Of Central Wyoming, U. S. A., Fossil Imprint 78 (1), pp. 51-79 : 56-57

Genus Celtis L.

Text-fig. 2h–j

M a t e r i a l. Two specimens, silicified. USNM PAL

772342, DMNH EPI.47809.

D e s c r i p t i o n. Endocarp elliptic in lateral view, nearly round in cross section, USNM PAL 772342 – 11 mm long and 8.5 mm wide in the plane of symmetry and 8 mm perpendicular to it ( Text-fig. 2h–j ); DMNH EPI.47809 – 8.8 mm long and 7.4 mm wide in the plane of symmetry and 7.0 mm perpendicular to it. Apex somewhat acute with a point, base rounded with an indistinct pit of attachment. The endocarp marked by a fine groove in the plane of symmetry ( Text-fig. 2j ), extending from the apex to the base, dividing the endocarp into two symmetrical halves. Endocarp surface marked by depressions approximately 0.75 mm in diameter, these running in poorly-defined longitudinal rows of 8 to 9 pits each ( Text-fig. 2h, j ). The inter-depression areas marked by ridges that have uneven high points which create a series of tubercles between the depressions. Endocarp abraded, and no evidence of cellular structure is exhibited on the surface.

D i s c u s s i o n. The Wagon Bed specimens conform to the morphology of the endocarps of Celtis , a common fossil of western North America and of Europe ( Manchester 1989). Celtis phenacodorum (COCKERELL) E.W.BERRY often co-occurs with vertebrate material in the early Eocene of Wyoming, first appearing in late Clarkforkian assemblages and becoming widespread in Wasatchian time ( Gingerich 1989). Samples of C. phenacodorum from western Polecat Bench, Wyoming, illustrated in Manchester et al. (2002: pl. 4, figs O–S) are virtually identical in morphology to the Wagon Bed specimen, except in two respects. First, while the Wagon Bed specimens exhibit a clear lineation on the side of the endocarp in the plane of suture, it appears to lack a secondary keel situated at right angles to the plane of suture. However, as noted above, the surface is abraded, and in Manchester et al. (2002: pl. 4, figs O–S) the minor keel is not particularly apparent. Second, at 11 mm and 8.8 mm in length, the Wagon Bed specimens are somewhat larger than the Paleocene specimens illustrated in Manchester et al. (2002) which average ~ 8.5 mm long, or the early Eocene ones described by Gingerich (1989) which average 5 mm in length. They are also substantially larger than the Celtis from the middle Eocene Clarno flora (average length 4.7 mm). Gingerich (1989) notes that Celtis endocarps commonly occur with vertebrate material, and suggests that their preservation is favored by calcium-rich environments. Modern Celtis is a genus of trees and shrubs that are widespread in temperate and tropical environments of both hemispheres. While most of the endocarps reported in the fossil record are less than a cm in diameter, some of the living tropical species (e.g., C. phillipinensis BLANCO ) have large endocarps similar to the size of this fossil (e.g., Sattarian and van der Maesen 2006).

Family Cannabaceae MARTINOV ( Ulmaceae II )

Genus Aphananthe PLANCH.

Text-fig. 2k–n

M a t e r i a l. One specimen, chalcedony cast. USNM

PAL 772344.

D e s c r i p t i o n. Endocarp elliptical in lateral view and triangular in cross section, 8.3 mm long, 5.5 mm wide on the major axis and 4.7 mm wide on the minor axis ( Text-fig. 2km ). Apex marked by a small protrusion or placental plug. Three raised ridges radiate from the apex, creating the three angles of the endocarp ( Text-fig. 2k ). Base rounded. Much of the surface is very finely papillate, possibly reflecting the surficial cell structure ( Text-fig. 2n ). No details of the endocarp wall structure are preserved.

D i s c u s s i o n. The specimen conforms in endocarp morphology with extant species of Aphananthe documented by Manchester (1989) and accords with Aphananthe maii MANCHESTER of the middle Eocene Clarno flora of Oregon in all characters that are preserved. The coiled embryo seen in the Clarno material ( Manchester 1994) and in extant species is not preserved in this specimen, nor in the similar unnamed species from the late Eocene of Oregon ( Manchester and McIntosh 2007). As with Chandlera , the Wagon Bed flora provides a Rocky Mountain occurrence of the genus in the North American Paleogene record. It is also reported in the Oligocene of western Siberia ( Dorofeev 1982) and the Holocene of Japan ( Miki 1938). The modern genus includes five species of deciduous or semi-deciduous shrubs or trees, three widely distributed from Japan to India and south to Australia, one in Madagascar and one in Mexico ( Todzia 1993, Mabberley 2008).

Figures

Text-fig. 2. Salicaceae (a–g), Cannabaceae (h–n), cf. Betulaceae (o–r). a–g: Saxifragispermum, USNM PAL 772341. Scale bar = 5mm except as indicated. a–b: Lateral, c: apical, and d: basal views of fruit, reflected light, palladium coated; apex at top of (a, b). e: Equatorial transverse section reflected light; arrows indicate presumed seeds, scale bar = 2mm. f: Detail of locule contents extracted from (e), transmitted light, scale bar = 200 Μm. g: Interwoven trichomes or fibers from locule, transmitted light, scale bar = 5 Μm. h–j: Celtis. h, i: USNM PAL 772342, reflected light, palladium coated, scale bar = 5mm. h: Lateral view parallel with plane of dehiscence. i: Lateral view perpendicular to plane of dehiscence. j: DMNH EPI.47809, Celtis in lateral view; showing reticulate sculpture and the vertically-oriented, plane of dehiscence (arrow), scale bar = 5mm. k–m: Aphananthe. USNM PAL 772344, reflected light, palladium coated, scale bar = 5mm. k: Apical view, note triangular cross section and apical plug (arrow). l: Lateral view, apex up. m: Lateral view at 90° to (l). n: Detail of cellular pattern at surface of endocarp, scale bar = 0.5 mm. o–r: