The Fossils of Rhodoleia Champion (Hamamelidaceae) in Europe
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Acta Palaeobot. 41(2): 161–175, 2001 I would like to dedicate this work to Professor Leon Stuchlik to express my gratitude for long years of friendship, research cooperation and support, often in difficult times. The fossils of Rhodoleia Champion (Hamamelidaceae) in Europe DIETER HANS MAI Natural History Museum, Invalidenstrasse 43, D-10115 Berlin, Germany Received 10 December 2000; accepted for publication 27 September 2001 ABSTRACT. Four species of the genus Rhodoleia Champion from the European Upper Cretaceous, older and younger Tertiary are described. The formal species Saxifragaceaecarpum bifolliculare Menzel is revised also to Rhodoleia. All species are essential elements in rainforest-like laurel forests under subtropical humid climatic conditions, and provide a good example of Engler’s theory of a “palaeotropical geoflora”. KEY WORDS: Rhodoleia, Hamamelidaceae, palaeotropical geoflora, Upper Cretaceous, Tertiary, Europe INTRODUCTION A curious fossil seed cluster from the Upper RHODOLEIA Cretaceous attracted the author’s attention in CHAMPION EX HOOKER F. the 1980s. Together with E. Knobloch he was able to assign these structures to the south- Bot. Magaz. 3(6), pl. 4509 (1850) east Asian genus Rhodoleia Champion from the Hamamelidacae (Rhodoleioideae) (Kno- bloch & Mai 1986), because of their resem- CARPOLOGY blance to similar seeds from the Upper Eocene (Mai & Walther 1985). Their presence in the Rhodoleia championii Hook.f. Tertiary was puzzling. Light was shed on this Fig. 1A; Pl. 1 figs 1–3, Pl. 2 figs 1–3, mystery by material from Herzogenrath Pl. 3 figs 1–6, Pl. 4 figs 1,2 (Lower Rhineland) which Menzel (1913) had described as Saxifragaceaecarpum bifollicu- The Rhodoleideae consisting of the recent lare. In one part of a capsule imbricatedly ar- monotypic genus Rhodoleiea Champion, differ ranged seeds were found which resembled the from the related Hamamelidaceae in such curious cluster from the Upper Cretaceous. characters as shape and venation of the Investigations of all the fossil fruits and leaves, condensed inflorescences in simple seeds belonging to Rhodoleia Champion were heads and, primarily, in their fruits and seeds. subsequently investigated followed, almost im- The multiovulate carpels are worthy of note. mediately, by analysis of characteristic struc- The ovary is semi-inferior being fused below tures of the seed testa under the SEM. This the middle with the slightly elongated hypan- technique had previously been impossible due thium. The carpels are compressed, woody, to lack of proper equipment. bifid and pointed, two-septate and four-valved The genus has some significance for the his- (Pl. 1 fig. 1). The capsules are fused, 5 to 10 tory of vegetation as is also mentioned in this per head. Dehiscence is both loculicidal and monographic study. septicidal. The pericarp is woody or leathery. 162 diameter for fruiting heads, capsule length 6– 10 mm and seeds 3.5–5.5 mm × 2.5–3.5 mm; larger size has been reported for fertile seeds (Vink 1957, Melchior 1964, Mai & Walther 1985). FOSSIL FINDINGS The fruits and seeds of Rhodoleia Cham- pion were first described in the fossil state by Mai and Walther (1985). The present author succeeded in determining 6 seeds in widely va- rying states of preservation, taken from the Upper Eocene at Weißelster Basin (Saxony), as Rhodoleia bellmannii Mai in Mai & Walther. Better preserved and more abundant fossil Fig. 1. Schematic view of seeds of Rhodoleia (Hi = hilum, material was obtained from the grey clays of Mi = micropyle, R = raphe). A – Rhodoleia championii Hook.f.; the Upper Maastrichtian (Upper Cretaceous) B – R. bifollicularis (Menzel) comb. nov.; C – R. bellmannii Mai in Mai & Walther; D – R. cretacea Knobloch & Mai; from Walbeck in the Allertalgraben, south of E – R. hercynica Mai (after Mai 1968, 1987; Mai & Walther Oebisfelde (Saxony – Anhalt). In addition to 1985; Knobloch & Mai 1986, emended) several round and wedge-like single seeds, gatherings were also made of being coalified seeds which were identified as seed clusters in the locule of a capsule. This material was de- The exocarp is single and very often separated, scribed by Knobloch and Mai (1986) as Rhodo- the endocarp horny or cartilaginous. The two leia cretacea. styles of the carpel are relatively long and nar- One year later Mai (1987) described two row and slightly divergent at the apex, indicat- further seeds with the suggestion of a wing ing the former presence of the stigma which from the Upper Palaeocene clays of a drilling had fallen off during the ripening of the fruit. at Gonna near Sangerhausen (Saxony – An- Each locule of the capsule has many (10–20) halt) as Rhodoleia hercynica. seeds which are compressed, angular in shape From the time of Menzel (1913) a related and imbricate. Most are sterile and wingless type of seed was frequently mentioned in pub- with only a few fertile, triangular in cross-sec- lications, but, from the taxonomic point of tion, compressed and narrowly winged. The view, it was incorrectly assigned to Saxifraga- ventral margin of the seed is mostly arched ceaecarpum bifolliculare Menzel (Raniecka-Bo- and the dorsal one angled. From the dorsal browska 1962, Mai 1968). In the present paper margin the hilum is visible as a crevice or dis- locule casts of seed clusters from the Middle tinct rim. The raphe extends from the hilum to Miocene of Herzogenrath near Düren (Lower the chalaza, relatively being sharp-edged at Rhineland ) and the Lower Miocene quartzites first but ultimately becoming filiform. The of Osieczów (Lower Silesia) are recognised as micropyle is apical, sometimes forming a small fossil fruits and seeds of Rhodoleia bifollicu- point, more often appearing as a small hole. It laris (Menzel) comb. nov. and prove the conti- is always directed outwards and upwards (epi- nued presence of this genus in the Miocene of tropous) (Pl. 2 fig. 2). Europe. The testa of the seed is hard, with an indis- The characteristic fruits and seeds of seve- tinct polygonal sculpture on the outer surface ral species of Rhodoleia Champ. are, therefore, (Pl. 3 figs 1, 2) which is often matt. At the dor- known in Europe from the Upper Cretaceous sal margin papillate sculptured elements are to the younger Tertiary. However, no fossil very often developed (Pl. 3 fig. 1). They consist leaves, wood or pollen have so far been found. of round cells with thickened walls. The ven- tral margin or wing shows longitudinal struc- KEY TO SPECIES ture of isodiametric cells with strongly undu- late walls (Pl. 3 fig. 4). The dimensions of re- 1. Seeds large, 2.0–4.0 mm in diameter . 2 cent diaspores are approximately 10–25 mm – Seeds small, only 1.2–2.0 mm in diameter . 3 163 2. Seeds winged on one margin, wing distinctly de- stitute, Warsaw Nos 103–105) – Lower veloped, opposite margin bearing the hilum and Miocene (Floral zone VI). raphe; relatively thin-walled. Seeds in two longi- tudinal rows, imbricately arranged in a fusiform lo- cule . R e m a r k s. In Mai’s revision of Menzel’s Rhodoleia bifollicularis (Menzel) comb.nov. (1913) original materials the author (Mai – Seeds wingless with only a slight wedge-like exten- 1968) gave a detailed description of this taxon. sion opposite the margin bearing the angled hilum The ovary consists of two carpels, fused from and raphe; relatively thick-walled . base to apex, leathery to slightly woody, com- Rhodoleia bellmannii Mai in Mai & Walther pressed, 16–21 mm long, 8–11 mm wide and 3. Seeds round and wedge-shaped, with the angled 4–5 mm thick. The ovary is semi-inferior, hilum and raphe; relatively thin-walled. Seeds in two longitudinal rows, imbricately arranged in a fused with the hypanthium below the middle. boat-shaped locule-filling . Carpels of unequal length, the larger set ob- Rhodoleia cretacea Knobloch & Mai liquely, extending beyond the tip of the pedicel, – Seeds long, in shape of an orange segment, margin slightly curved, elongate-oval, with a short bearing the hilum and raphe slightly curved, but and beak-like style. The involute margins and not angled; thick-walled . adjacent faces of the carpels are fused below to Rhodoleia hercynica Mai form a thick partial septum towards the base of the loculus. The calyx (receptacle) extends 4–8 mm beyond the base of the pedicel strong- DESCRIPTION OF SPECIES ly involuting the syncarpium (Pl. 1 figs 4–9), Rhodoleia bifollicularis (Menzel) which is semi-inferior. Calyx slightly asymme- comb. nov. tric, extending beyond the larger carpel and, in Fig. 1B, Pl. 1 figs 4–9, Pl. 2 figs 11–15, one case, bearing one, long-triangular, mem- Pl. 3 figs 7, 8, Pl. 4 figs 6, 7 branous lobe. The calyx is covered in longitudi- nal wrinkles, which indicate the vascular Basionym. Saxifragaceaecarpum bifollicu- bundles or points of attachment of the petals. lare Menzel 1913, p. 32, Pl. 4 figs 7–9. Fruits sessile, 2–3 in each fructification. De- H o l o t y p e. Menzel 1913, Pl. 4 fig. 7; MfN hiscence septicidal, from apex to base along Berlin, Orig. No. 407. the suture of the carpels, loculicidal at the apex, so that the valve at the tip is widely Syntype. Pl. 2 fig. 11 in this paper; MfN open (Pl. 1 fig. 4). Placenta straight bearing Berlin, Orig. No. 408. several imbricately arranged ovules. D i a g n o s i s. Inflorescence in heads; carpels The fruit wall is two-layered; the outer (epi- united in an ovary which is semi-inferior on carp) of woody parenchyma contained vessels. account of the presence of a zygomorphic cu- It separates very easily from the thick, inner pule-like hypanthium extending to 1/3 of the part (endocarp) composed of sclerenchyma.