Inflorescences and Compound Leaves of the Extinct Platanus Neptuni

Acta Palaeobotanica 50(1): 5–15, 2010

We dedicate this paper to our friend Harald Walther on the occasion of his 80th birthday

Infl orescences and compound leaves of the extinct Platanus neptuni complex in the Oligocene of Oregon, USA

STEVEN R. MANCHESTER 1 and ZLATKO KVAČEK 2

1 Florida Museum of Natural History, University of Florida, Gainesville Florida, USA; e-mail: steven@fl mnh.ufl .edu 2 Charles University, Faculty of Science, Institute of Geology and Palaeontology, Albertov 6, CZ 128 43 Prague 2, Czech Republic; [email protected]

Received 2 February 2010; accepted for publication 22 April 2010

ABSTRACT. The extinct species Platanus neptuni (Ettingshausen) Bůžek, Holý & Kvaček, formerly reported on the basis of infructescences, staminate infl orescences and associated foliage from the Late Eocene to Late Miocene deposits of Europe, is now recognized also in North America, based on a population dominating the Late Oli- gocene Yaquina fl ora of coastal Oregon. Staminate infl orescences are of the same morphology as in Europe: globose to ellipsoidal, each borne solitarily on a thick, elongate peduncle. A circumsissle raised scar is visible around the peduncle at the base of infl orescence heads – a feature diagnostic of the extinct Platanus subgenus Glandulosa Kvaček, Manchester & Guo. Contrary to the European records, which are more variable in foliage (simple to compound tri- and pentafoliolate), the leaves at the Yaquina locality are exclusively trifoliolate, shar- ing short petioles expanded at the base, as in many European populations of P. neptuni morphoforma fraxinifolia (Johnson & Gilmore) Kvaček & Manchester. The preservation in coarse deposits precludes anatomical investiga- tion, but the morphology of both leaves and reproductive structures provides evidence for confi dent assignment to the same species previously recognized only from Europe.

KEYWORDS: Platanaceae, Oligocene, Europe-North America disjunction

INTRODUCTION

Patterns of plant distribution in the north- America and Europe (Platanites), while others ern hemisphere refl ect a long history of inter- were apparently more confi ned in distribution. and intracontinental dispersal, with many The extinct clade of plane trees known as Pla- examples of genera whose ranges have dimin- tanus subgenus Glandulosa Kvaček, Manches- ished over time. There are numerous exam- ter & Guo, with compound leaves and elliptical ples of genera known from the early Tertiary to obovate unlobed laminae, was distributed of western North America that also occur in widely during the Palaeocene, with occur- Europe and/or Asia (Manchester 1999, Man- rences of P. bella in western Greenland, Wyo- chester et al. 2009, Hably et al. 2000). In ming in North America, and Xinjiang, north- the Platanaceae, some genera are known to western China (Kvaček et al. 2001). However, have populated both Asia and North America the related species, P. neptuni, known from (Macginitiea, Platimeliphyllum) or both North infl orescences, and infructescences as well as 6 distinctive 3- (sometime 5-) foliolate to sim- PLATANACEAE ple leaves, has only been recognized from the European Tertiary, where it was a prominent Platanus L., subgenus Glandulosa Kvaček, component of vegetation in Late Eocene to Manchester & Guo Miocene fl oras. We now report a newly recog- nized disjunct occurrence of P. neptuni from Platanus neptuni (Ettingshausen) Bůžek, the Oligocene of coastal Oregon, western USA, Holý & Kvaček (Plates 1–3) which is important for its biogeographic impli- cations, as well as providing additional sup- port for the previously hypothesized linkages DESCRIPTION OF THE YAQUINA of foliage and reproductive structures as parts POPULATION of the same extinct plant (Kvaček & Manches- ter 2004, Kvaček 2008). F o l i a g e. Morphoforma fraxinifolia (John- son & Gilmore) Kvaček, Manchester & Guo. Leaves trifoliolate, medial leafl et slender, MATERIAL AND METHODS elongate-lanceolate (?), about 20–27 mm wide. Medial leafl et narrow cuneate, symmetrical, Outcrops near Newport, Oregon, USA, were the shortly petiolulate with acute lamina base subject of fi eld work and unpublished studies by James and apex. Lateral leafl ets sessile, slightly McClammer (1978), yielding several hundred speci- broader than the medial, arising at angle of mens now archived at the US National Museum. An 30–45º, at base strongly asymmetric, in rare additional smaller collection was made by Manches- cases the pair of lateral leafl ets connate with ter in 2004 (deposited at Florida Museum of Natural History-UF), from one of the original sites of McClam- the rachis for a short distance, in which cases mer, situated on a steep hill above a road cut of the they appear basally fused by their outer mar- south Yaquina Bay highway at river marker 25 (GPS: gins (Pl. 1, fi g. 2). Leafl et apices acute, mar- 44°34.95′N; 124°00.76′W), Lincoln County, Oregon. gins bluntly dentate, usually in upper parts of The fossil plants occur in sandstones and siltstones leafl ets only, teeth small, closely spaced, acute representing a deltaic unit between the lower and upper marine tongues of the Yaquina Formation. No to obtuse, with straight to convex basal side associated radiometric dates are available, but marine and straight to concave apical side, sinuses biostratigraphy has indicated the formation may range shallow, rounded; venation camptodromous from the uppermost Oligocene to Lower Miocene. to semicraspedodromous, midrib straight in According to McClammer’s unpublished work, the terminal leafl et, and almost straight in lat- fl oral horizon occurs in the upper part of the lower third of the formation, below foramineral assemblages eral leafl ets, arising from slightly expanded assigned to the Zemorrian foramiferal stage (a stage uppermost part of petiole, secondary veins spanning from Early Oligocene to earliest Miocene; arched, regularly spaced, arising at wide Prothero 2003), and between thick marine sequences angles and looping well within the lamina, containing molluscan faunas diagnostic of the “Blakely interspaced with intersecondary and tertiary Stage” (Weaver et al. 1944) in the West Coast provin- cial chronology. On the other hand, molluscan workers veins forming a regular reticulum, abmedial placed the entire Yaquina Formation in the Juanian side veinlets arising from loops of secondar- provincial molluscan stage (Addicott 1976, 1981), rang- ies either entering teeth or forming a second ing from Late Oligocene to Early Miocene (ca. 24–29 series of smaller loops, from which veinlets Ma; Squires 2003).” also enter teeth, higher-order veins in ± iso- Leaves and reproductive structures were obtained by fracturing the fossiliferous sediment along the bed- diametric meshes. ding plane with a hammer and chisel. For the prepara- Staminate infl orescences (Pl. 2, fi gs 1–4) tion of in situ pollen, small pieces were mechanically globular to ellipsoidal (7–10 mm diameter), removed from a staminate infl orescence with the aid formed of densely packed stamens on a small of the collodion-transfer-fi lm technique. The fi lm was central receptacular core, borne on a stout cleaned in hydrofl uoric acid and after rinsing treated in very dilute KOH, and mounted on glass slides peduncle up to16 mm long and 2 mm thick. for observation by transmitted light microscopy. In A prominent thickening occurs on peduncle spite of several attempts to remove the leaf cuticles at the junction with the head (Pl. 2, fi g. 1). by the same procedure, no cellular structures were Anthers elongate, 2.0–2.3 mm long, sessile obtained. We compared the North American fossils with those from many sites in Europe, housed in vari- with prominent, apiculate connectives (Pl. 2, ous museum collections previously cited in Kvaček and fi g. 3). Perianth not recognizable. Pollen grains Manchester (2004). (Pl. 2, fi gs 5, 6) prolate, 20–22 by 18–20 μm; 7 tricolpate, colpi extending ca 90% of the length populations. In fact, the only site yielding such of the grain. Sculpture fi nely reticulate. foliage with fused leafl ets is the Late Oligocene Associated pistillate infl orescences not seen Verőcemaros locality in Hungary (Hably 1982, but probable infructescences (Pl. 3) are pre- pl.3, fi gs 1–2, as Debeya hungarica). The usual served as globose heads bearing numerous condition (see Walther 1985, Kvaček & Man- stout sessile, narrow-ovate achenes. Achenes chester 2004) is for the leafl ets to be com- often abraded, but sometimes with intact per- pletely free, often shortly petiolulate. In a new sistent straight styles. Borne singly on stout occurrence at Janda, North Serbia the trifoli- peduncle (rarely preserved). olate leaf forms suggest only seemingly fused bases of lateral leafl ets, which merely overlap S p e c i m e n s. USNM 508221, 508222, 508228, (Djordević-Milutinović 2009). The shape of the 508229, 508232, 508233, 508235–508240, leafl et bases is broad rounded, not cuneate 537854, 537855, 537864, UF 19054–46575, as in other European populations with com- 46599, 46603, 46604. pound foliage (see Kvaček & Manchester 2004, Fig. 7). In other respects, i.e. short petiole with expanded base, venation, kind and distribu- DISCUSSION tion of teeth, the North American population matches the type collection of P. neptuni mf. Our assignment of this Oligocene popula- fraxinifolia from the Lough Neagh core in tion of Platanus neptuni from western Oregon Ireland (Johnson & Gilmore 1921) and other to the same species as the European fossils is occurrences in Europe. supported by distinctive features of both veg- Although no living Platanus species has etative and reproductive structure. The char- compound leaves nor the unusual surround- acters shared with the European populations ing scar at the junction of the peduncle and include: 1) trifoliolate leaves with short, basally infl orescence head, placement of P. neptuni expanded petioles, and the same kind of vena- in the Platanaceae is supported by: 1) the tion and margin (Pl. 1); 2) globose to ellipsoid arrangement of the leafl ets, which in 5-leaf- infl orescences borne singly on stout peduncles leted forms has a pedate (rather than strictly with a prominent circular thickening at top of palmate) arrangement matching the primary the peduncle (Pl. 2, fi g. 1); 3) prolate, tricol- venation of a 5-lobed simple leaf of extant Pla- pate, reticulate pollen (Pl. 2, fi gs 5, 6). tanus species, while 3-leafl eted forms show the The North American population differs from same arrangement as the lobes of a trilobed most European occurrences in the uniformly tri- simple leaf of extant species. 2) the unusual foliolate leaf form. Most European occurrences epidermal structure found both on the leaves are typically more variable in leafl et number, and reproductive organs, including anomo- either with occasional pentafoliolate (Ireland; cytic stomata with thickened periphery, fi nely Klausa, Germany) or prevailingly simple leaves, undulate anticlinal cell walls and multicellu- with exceptional apical lobes on simple leaves lar trichome bases occasionally bearing large (most occurrences in the Boreal province). The disk-shaped glands, 3) stamens with short fi la- Yaquina site has not yielded the tubular remains ments or sessile, having elongate lateral pollen of stipules (known mainly just from the Eocene sacks and domed to apiculate connectives, 4) and Oligocene of north Bohemia), nor young tricolpate reticulate pollen, 5) fruits bearing pistillate infl orescences. In both North America a single style and dispersal hairs. and Europe infructescences apparently do not The petiole base in Platanus neptuni cov- fall into fruitlets in the mature stage, unlike liv- ers the bud, as in Platanus subgen. Platanus ing Platanus. The associated female heads from and contrary to subgen. Castaneophyllum Yaquina are more robust, often with straight Leroy. Although some collections included in remains of styles, while in fully preserved speci- the synonymy for this species (Bůžek et al. mens in Europe they are apically slightly curved 1967, Kvaček & Manchester 2004) were pre- (Bůžek et al. 1967, pl. 2). viously included in extinct genera of Platan- The tendency for the lateral leafl ets to be aceae, in particular to Dewalquea and Debeya, slightly fused together at the extreme base, as we explained (Kvaček et al. 2001), that these observed among some of the Yaquina specimens genera were both established on Cretaceous (Pl. 1, fi g. 2), is uncommon in the European and Palaeocene fossil leaves that appear to be 8 distinct from P. neptuni. We adopted the phi- collection from Yaquina. Although not as losophy that this extinct species can be accom- abundant, infl orescences and infructescences modated in the extant genus, but in the extinct were also commonly observed. During our ten- subgenus, Glandulosa. tative inspection of the collection some other The hypothesized whole plant reconstruc- plants associated have been noticed: a fern tion of Platanus neptuni, including leaves with goniopterid type of venation, Metasequoia (compound to simple), dispersed stipules, sta- and taxodioid foliage, pine twigs with needles minate and pistillate infl orescences, infructes- in dense fascicles (? Strobus type), a seed cences and fruits is supported by shared epi- cone (Pinus type) and male cones, cupressoid dermal anatomy from the Markvartice and twigs with attached seed cones of the Chamae- Habartov localities (Bůžek et al. 1967), by the cyparis type, Pseudolarix (see Gooch 1992), platanaceous characters of the separate organs and dicots including Cornus-like and lauroid as judged by comparison with the correspond- entire leaves, rare lobed to coarsely crenulate ing organs of extant species of Platanus, and leaves with palinactinodromous venation of the by the co-occurrence of these organs at numer- Platanus type and very common morphotypes ous European localities. The additional case of with palmate venation of the “Acer arcticum” co-occurrences of the same kind of leaves and type recalling Ampelopsis, betulaceous foliage, reproductive structures at the Yaquina local- Fagus, legume leafl ets, Hydrangea fl owers, ity, far from the type area of the species, fur- and some more leaf fragments of dubious affi n- ther strengthens the basis for regarding these ities, and, among monocots, a leaf resembling organs as representing the same source plant Smilax. The assemblage seems to be composed although they have not been found in physical prevailingly of deciduous arboreal elements attachment in the fossil record. It is also note- including Platanus neptuni. worthy that the Yaquina population appears The accompanying vegetation at Yaquina to be exclusively trifoliolate, without variation differs greatly compared with that in the fl o- to pentafoliolate or simple as occurs at some ras containing abundant P. neptuni in Europe. other sites in Europe (Klausa, Kučlín, Bílina – Plants typically associated with abundant see Kvaček and Manchester 2004). European P. neptuni in Europe (Kučlín, Markvartice, sites with exclusively occurring trifoliolate Suletice, Flörsheim) include thermophilic ele- leaf forms are exceptional, e.g. Janda in North ments like Tetraclinis salicornioides, Caloced- Serbia (Djordević-Milutinović & Dulić 2009), rus, Engelhardia, Sloanea, and lauroids and in a few others trifoliolate form predominates, much lower diversity of broad-leaved decidu- e.g. Mesta Graben (Palamarev et al. 1999). ous elements, such as Cercidiphyllum, Acer, We maintain a distinction between the Early Betulaceae, and Ulmaceae. Palaeogene Platanus bella and the Late Palae- ogene to Miocene species, P. neptuni. A subtle ACKNOWLEDGEMENTS difference is in the more frequent intersecond- We dedicate this paper in celebration of Prof. Har- aries of the former (Kvaček et al. 2001, Fig. 3E) ald Walther and his infl uence on this and numerous while in P. neptuni the intersecondaries are other palaeobotanical investigations. We appreciate usually lacking or single, short and incomplete, help extended by Jonathan Wingerath, US National and widely spaced apart from the secondaries. Museum, Washington for access and help with cura- In addition, we do not have suffi cient evidence tion of the Yaquina collection. We thank Johanna Eder for helpful review comments and Terry Lott for help in to merge P. bella and P. neptuni, because the proofi ng and fi nal formatting of the manuscript. The infl orescences and infructescences of P. bella study was fi nancially supported by the Grant Agency have not been found from any of the Palaeocene of the Czech Republic (GAČR), project No. 205/08/0643 sites where the foliage has been found; hence and the research scheme No MSM 002162085, Czech precluding more detailed comparison with the Republic. full suite of organs known from P. neptuni. REFERENCES ASSOCIATED FLORA ADDICOTT W.O. 1976. Molluscan paleontology of The trifoliolate leaves of Platanus neptuni the lower Miocene Clallam Formation, northwest- are seen on nearly every slab coming from ern Washington. US Geol. Surv. Prof. Paper, 976: the McClammer’s site 04 in the USNM 14203 1–44. 9

ADDICOTT W.O. 1981. Brief history of Cenozoic among extinct and extant Platanaceae. Intern. marine biostratigraphy of the Pacifi c Northwest. Jour. Plant Sci., 162: 441–458. Geol. Soc. Amer., Special Paper, 184: 3–15. MANCHESTER S.R. 1999. Biogeographical relation- BŮŽEK Č., HOLÝ F. & KVAČEK Z. 1967. Eine bemer- ships of North American Tertiary fl oras. Ann. Miss. kenswerte Art der Familie Platanaceae Lindl. Bot. Garden, 86: 472–522. (1836) im nordböhmischen Tertiär. Monatsber. MANCHESTER S.R, CHEN Z.-D., LU A.-M. Deutsch. Akad. Wiss. Berlin, 9: 203–215. & UEMURA K. 2009. Eastern Asian endemic seed DJORDJEVIĆ-MILUTINOVIĆ D. & DULIĆ I. 2009. plant genera and their paleogeographic history Leaf polymorphism of Platanus neptuni mf. frax- throughout the Northern Hemisphere. Jour. Syst. inifolia (Johnson & Gilmore) Kvaček & Manchester Evol., 47(1): 1–42. from Oligocene deposits at Janda (Mt. Fruška Gora, McCLAMMER J.U., JR. 1978. Paleobotany and stra- Serbia). Bull. Natural Hist. Mus., 2: 7–33. tigraphy of the Yaquina fl ora (latest Oligocene – GOOCH N.L. 1992. Two new species of Pseudolarix earliest Miocene) of western Oregon. MSc Thesis, Gordon (Pinaceae) from the middle Eocene of the Univ. Maryland. Pacifi c Northwest. PaleoBios ,14: 13–19. PALAMAREV E., KITANOV G., BOZUKOV V. HABLY L. 1982. Egerian (Upper Oligocene) macrofl ora & STANEVA K. 1999. Fossil fl ora from the central from Verőcemaros (Hungary). Acta Bot. Acad. Sci. area of the Mesta Graben: the local fl ora of Bou- Hung., 28: 91–111. kovo (Western Rhodopes). Phytol. Balcan., 5(2–3): 27–46. HABLY L., KVAČEK Z. & MANCHESTER S.R. 2000. Shared taxa of land plants in the Oligocene of PROTHERO D.R. 2003. Pacifi c coast Eocene-Oligocene Europe and North America in context of Holarc- marine chronostratigraphy: a review and an update: tic phytogeography. Acta Univ. Carol.-Geol., 44: 1–13. In: Prothero D.R., Ivany, L.C. & Nesbitt E.R. 59–74. (eds), From greenhouse to icehouse: the marine Eocene-Oligocene transition. Columbia University JOHNSON T. & GILMORE J.G. 1921. The occurrences Press, New York. of Dewalquea in the core-bore at Washing Bay. Sci. Poc. R. Dublin Soc., 16: 323–333. SQUIRES R.L. 2003. Turnovers in marine gastro- pod faunas during the Eocene-Oligocene transi- KVAČEK Z. 2008. Whole-plant reconstructions in fos- tion, west coast of the United States: 14–35. In: sil angiosperm research. Intern. Jour. Plant Sci., Prothero D.R., Ivany, L.C. & Nesbitt E.R. (eds), 169: 918–927. From greenhouse to icehouse: the marine Eocene- KVAČEK Z. & MANCHESTER S.R. 2004. Vegetative Oligocene transition. Columbia University Press, and reproductive structure of the extinct Platanus New York. neptuni from the Tertiary of Europe and relation- WALTHER H. 1985. Das Tertiär -Vorkommen der ships within the Platanaceae. Plant Syst. Evol., Gattung Platanus L. im Tertiär des Weiselster- 244: 1–29. Beckens (Bezirk Leipzig, DDR). Hall. Jb. Geowiss., 10: 9–19. KVAČEK Z., MANCHESTER S.R. & GUO SHUANG- XING. 2001. Trifoliolate leaves of Platanus bella WEAVER C.F. et al. 1944. Correlation of the marine (Heer) comb. n. from the Paleocene of North Amer- Cenozoic formations of western North America. ica, Greenland, and Asia and their relationships Geol. Soc. Amer Bull., 55(5): 569–598. 10

PLATES

Plate 1

Leaves of Platanus neptuni from the Yaquina Formation, Oregon, USA. Scale bars 1 cm

1. Leaf showing a medial petiolulate and two lateral sessile leafl ets and short, basally expanded petiole, USNM 508228 2. Smaller leaf, showing fusion of lateral leafl ets to each other below the terminal leafl et, USNM 508222 3. Leaf with narrow leafl ets and complete petiole, USNM 508233 4. Leaf with subsessile narrow leafl ets, USNM 508232 5. Leaf showing symmetry of median leafl et, strong asymmetry of lateral leafl ets, USNM 508221 6. Well preserved leafl et showing details of higher order venation and serrate margin, USNM 508229 Plate 1 11

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Plate 2

Staminate infl orescences and in situ pollen of Platanus neptuni from the Yaquina Formation, Oregon, USA. Scale bar in fi g. 4 applies also to 1–3

1. Somewhat elongate, ovoid head borne on stout peduncle. Note broadened scar at junction of peduncle and infl orescence, a diagnostic character for the species. USNM 508238 2. Globose infl orescence on stout peduncle, USNM 508236 3. Well preserved globose head, USNM 508235 4. Globose head on stout peduncle, USNM 508240 5. Pollen clump from one of the stamens of the infl orescence in fi g. 3. Scale bar – 20 μm 6. Detail of tricolpate, reticulate pollen, Scale bar – 10 μm Plate 2 13

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Plate 3

Infructescence found associated with Platanus neptuni at the Yaquina fl ora

1. Pedicellate head, USNM 508237 2. Infructescence with isolated fruitlet at right, USNM 508239 3. Abraded infructescence, USNM 537854 4. Abraded infructescence showing central receptacle, USNM 537864a 5. Slab showing numerous abraded heads of different size, USNM 537855 Plate 3 15

S.R. Manchester & Z. Kvaček Acta Palaeobot. 50(1)