Fig 1.
World map showing the distribution of modern and fossil Rhamnaceae.
Gray area indicates the distribution of extant Rhamnaceae. The shapes correspond to different fossilized plant organs and the colors represent different ages. The fossil flowers and leaves described here were collected from the Rancho Grande site in Chubut Argentina. Details of all occurrences shown here are listed in Table 1. The base map was created with Natural Earth Dataset.
Table 1.
Occurrences of fossils attributed to Rhamnaceae, excluding those based on leaf compressions alone.
Fig 2.
Notiantha grandensis Jud, Gandolfo, Iglesias & Wilf, gen et sp. nov.
(A) Flower in transverse view showing pentamerous structure, sepals triangular with a distinct keel, cucullate petals alternating with sepals, stamens antepetalous, and floral disk surrounding a coalified gynoecium. MPEF-Pb 8548a. (B) Counterpart of specimen in ‘A’ showing a sepal with a central keel and two marginal veins converging toward the apex (at arrow) MPEF-Pb 8548b. (C) Composite digital illustration of the flower created from ‘A’ and ‘B’. (D) Flower in longitudinal view showing slender pedicel, floral cup (at arrow), three preserved sepals, and a cucullate petal (at arrowhead). MPEF-Pb 8549. (E) Close-up of the petal in ‘D’ showing clawed structure and the longitudinally folded distal portion of the petal; the overlapping lobes are marked with arrows. MPEF-Pb 8549. (F) Flower in longitudinal view showing slender pedicel and three sepals. MPEF-Pb 8551. (G) Close-up of flower in ‘A’ showing the keeled sepal (at arrowhead), and the notched petal apex (at arrow). MPEF-Pb 8548a. (H) Close-up of flower in ‘A’ showing an anther opposite a petal, and a line suggesting where the anther filament adnate to the petal at its base (at arrow). MPEF-Pb 8548a. Scale bars: A-D, F = 2 mm; E = 0.5 mm; G, H = 1 mm.
Fig 3.
Comparison of fossil (A-F) and modern Rhamnaceae leaves (G-J).
(A) S. grandensis MPEF-Pb 8553 showing overall shape, stout petiole, acute base (at arrow), serrate margin, and acrodromous primary veins. (B) S. grandensis MPEF-Pb 8560 showing its shape, acute to attenuate apex (at arrow), serrate margin, and acrodromous primary veins. (C) S. grandensis MPEF-Pb 8555 showing overall shape, petiole, acute base, serrate margin, and acrodromous primary veins. (D) Close-up of the leaf blade (MPEF-Pb 8552) showing mixed percurrent epimedial tertiary veins running between the medial primary vein (mp) and the lateral primary vein (lp). Note that they form an acute angle to the medial primary vein. (E). S. grandensis MPEF 8563 overall shape, petiole, acute base, serrate margin, and acrodromous primary veins, and an asymmetric, obtuse apex. (F) Close-up of the margin in ‘E’ showing exterior tertiary veins that are looped or terminating at the margin; note the glandular tooth apex (at arrow). (G) Leaf of Sarcomphalus saeri (Pittier) Hauenschild US 2045934 showing ovate blade, petiole, rounded base, acute apex, serrate margin, three acrodromous primary veins, and alternate percurrent epimedial tertiary veins. (H) Leaf of S. saeri US 3554997 showing ovate blade, petiole, rounded base, acute apex, serrate margin with apically oriented teeth, three acrodromous primary veins, distal major secondary veins, and alternate percurrent epimedial tertiary veins. (I) Cleared leaf of Ziziphus sativa Gaertn. (junior synonym of Z. jujuba Miller) NCLC-H 1791 showing ovate to elliptic blade, acute base, acute apex, serrate margin with apically oriented teeth, three acrodromous primary veins. (J) Close-up of the leaf in ‘I’ showing the apically oriented glandular teeth. Note the similarity to ‘F.’ Scale bars: A, B, H = 10 mm; C, E = 5 mm; D = 3 mm; F, J = 2 mm; G = 15 mm; I = 40 mm.
Fig 4.
One of two equally most parsimonious trees based on floral characters and the topology of Hauenschild et al. [23] showing the position of Notiantha sister to the extant Paliureae [Hovenia+Sarcomphalus+Paliurus+Ziziphus] at arrow.
The alternate most parsimonious position in the ziziphoid clade for the fossil flowers is colored in dark green. A = Ampelozizypheae, B = Bathiorhamneae, V = Ventilagineae, R = Rhamneae, Po = Pomaderreae, C = Colletieae, Ph = Phyliceae, U = unplaced genera at tribal level, G = Gouanieae, Pa = Paliureae.
Table 2.
Comparison of fossil flowers assigned to Rhamnaceae.