Canarium

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 : 63-65

Genus Canarium L.

Text-fig. 5n–q

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

PAL 772361.

D e s c r i p t i o n. Fruit elliptic in lateral view (Textfig. 5n, o), rounded-triangular in cross section (Textfig. 5p), 27 mm long with a minimum equatorial diameter of 15 mm and a maximum equatorial diameter of 17.6 mm, the variation likely due to slight compression. Each corner of the triangular cross-section defined by a ridge which is poorly defined at the base but becomes strongly expressed apically, the ribs curving in on each other at the apex, but not touching, instead over-arching a small apical point ( Text-fig. 5p ). Each ridge with a central groove, the groove more defined towards the apex. The three ridges separate three elongate embayments on each of the three sides of the endocarp ( Text-fig. 5p ). Each embayment has grooves adjacent to the adjoining ribs and a central groove running up the middle of the face, the three grooves defining two low, longitudinal ridges running up each face. Base with an ill-defined point of attachment.

D i s c u s s i o n. The shape of the fossil, coupled with the three strong longitudinal ridges, suggests a valvate endocarp, such as found in the Cornaceae L. (some Nyssa L., Davidia BAILL. ) or Verbenaceae J.ST. -HILL.(e.g., Tectona grandis L.f.). However, the strength of the three lateral ridges and their overarching structure at the apex is most consistent with endocarps of Canarium involving a central, woody and resistant receptacle (see illustrations in Han et al. 2018). Interpreted as Canarium , then within the embayments formed by the receptacle are three separate endocarps enveloped by a common mesocarp and a fleshy exocarp ( Leenhouts 1956, 1959). The mesocarp forms a germination valve over each locule that is shed at maturity ( Hill 1933). While internal morphological and anatomical details to confirm this morphological interpretation are lacking, the presence of “ Canarium type ” pollen from the Wagon Bed Formation ( Leopold and MacGinitie 1972) supports this interpretation. Also from this formation, Fiero and Jones (1990) report a wood that they felt could be attributed to one of four families, including the Burseraceae .

Fossil fruits of Canarium are known from the Paleogene of Europe ( Gregor and Goth 1979, Collinson et al. 2012), Egypt ( Bown et al. 1982) and New Jersey, USA ( Tiffney 1999), and from the late Oligocene to Miocene in Asia ( Han et al. 2018). Although the foliage of Canarium is not particularly distinctive, the genus has been reported based on leaflet impressions from the middle Eocene of northern ( MacGinitie 1941) and southern ( Myers 1990) California; Hickey (1977) described Canariophyllum L.J.HICKEY from the latest Paleocene – early Eocene of North Dakota. Endocarps reported as Bursericarpum E.REID et M.CHANDLER from the London Clay ( Reid and Chandler 1933, Chandler 1961) and the Clarno Formation of Oregon ( Manchester 1994) represent the same family, but they are individual pyrenes rather than the trilocular syncarpous fruit that characterizes Canarium .

of nut showing four lobes of the locule separated by primary and secondary septa. l: Virtually extracted locule cast in two lateral views and in apical and basal view. m–q: USNM PAL 772354. m: Half nutshell, lateral surface view. n: Lateral view, rotated 90° from (m). o: Apical view, with radiating grooves. m, n, o: Micro-CT scan surface renderings. p: Internal view of nut naturally cleaved, displaying the locule, depth map image. q: Enlarged view in same orientation of (p), palladium-coated, reflected light, showing pseudo-cellular radiating mineral fibers. r–w: Carya USNM PAL 772348. r–t: Micro-CT scan surface renderings. r: Lateral surface view of smooth nutshell. s: Lateral view of nutshell half, rotated 90° from (r). t: Apical view of nutshell half. u: Basal view, showing radiating grooves, reflected light, palladium coated. v: Internal view of nutshell displaying the locule, micro-CT surface rendering. w: Same view, micro-CT depth map image.

The genus consists of 75 ( Leenhouts 1959) to 108 species ( Lam 1932) of the Old World tropics. According to Leenhouts (1959), three species are native to Africa, Madagascar and the Mauritius, two to Australia, and the remainder occur from India east through Melanesia. These include canopy trees, shrubs and “pseudolianas” ( Leenhouts 1959) which generally inhabit low elevation primary and secondary rainforests in monsoonal climates.

Figures

Text-fig. 5. Anacardiaceae (a–m), Burseraceae (n–q). Scale bars = 1cm. a–f: Pentoperculum sp. a–c: USNM PAL 772360. a: Lateral view of endocarp, apex up; three germination valves visible, the central clearly displaying the bipartite nature of the valve, reflected light, palladium coated. b: Apical view displaying six locules, with two preserved germination valves at the lower left, reflected light, palladium coated. c: Basal view of the endocarp, the locules suggested by swellings; note point of attachment, micro-CT scan surface rendering. d–f: Pentoperculum sp. USNM PAL 772359, reflected light, palladium coated. d: Lateral view of a probable 6-loculed endocarp, apex up; a single intact germination valve in the center, displaying the central lineation that divides it in two. e: Apical view; two bi-partite germination valves are visible, indicated by arrows to the middle cleavage line of two of the valves. f: Basal view, the locules suggested by the undulations in the margin. g–i: Indet. Spondioideae. USNM PAL 772358, reflected light, palladium coated. g: Lateral view of multi-locular endocarp, apex up. h: Apical view showing finely punctuate surface and peripheral locule cavities. i: Basal view. j–m: Cf. Pleiogynium USNM PAL 772357. j: Lateral view of the multi-locular endocarp, apex up; note intact germination valve on left and exposed locule facing the viewer, micro-CT scan surface rendering. k: Lateral view, rotated about 30° from (j), showing three exposed locules, reflected light, palladium coated; note bipartite locule lining at center. l: Apical view of the multilocular endocarp; the locule with intact germination valve at the upper right, reflected light, palladium coated. Arrows to each locule. m: Basal view showing central point of attachment and prominent radiating ridges aligned with the locules, micro-CT scan surface rendering. n–q: Canarium, USNM PAL 772361. Scale bar = 1cm. n: Lateral view of endocarp directly facing one germination valve flanked by two strong ridges; apex up; specimen coated in sodium nitrate and photographed by R. A. Scott. o: Lateral view facing one of the three pronounced ridges, flanked to the left and right by two germination valves; apex up. p: Apical view displaying the three strong ridges, arching over the apex and flanking three deep embayments, covered with germination valves. q: Basal view, the three ridges being less pronounced. o–q: Reflected light, palladium coated.