Tetraclinis Salicornioides -CUPRESSACEAE Int Jour of Plant Sciences 2000

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Int. J. Plant Sci. 161(2):331–344. 2000.q 2000 by The University of Chicago. All rights reserved.1058-5893/2000/16102-0016$03.00

CONES, SEEDS, AND FOLIAGE OF TETRACLINIS SALICORNIOIDES (CUPRESSACEAE) FROMTHE OLIGOCENE AND MIOCENE OF WESTERN NORTH AMERICA: A GEOGRAPHIC

EXTENSION OF THE EUROPEAN TERTIARY SPECIES

Zlatko Kvacek, Steven R. Manchester,1 and Howard E. Schorn

Charles University, Faculty of Science, Albertov 6, 12843 Prague 2, Czech Republic; Florida Museum of Natural History, University of Florida,Gainesville, Florida 32611, U.S.A.; and Museum of Paleontology, University of California, Berkeley, California 94720, U.S.A.

The cupressaceous genus Tetraclinis is recognized from the Oligocene and Miocene of western North Americaon the basis of co-occurring seed cones, seeds, and foliage branches. Morphological and anatomical compar-isons with the two previously recognized European Tertiary species indicate that the North American specimensare morphologically inseparable from Tetraclinis salicornioides (Unger) Kvacek. The North American taxonis treated as a new variety, T. salicornioides (Unger) Kvacek var. praedecurrens (Knowlton) comb. et stat. nov.,and is distinguished from the European representatives, T. salicornioides (Unger) Kvacek var. salicornioides,by slight anatomical differences in the leaf epidermis. Although cones and seeds of the fossil species are closelysimilar to those of extant Tetraclinis articulata, the foliage is more “spreading,” composed of flattened segmentswith fused facial and lateral leaves that are apparently adaptive for a more mesic climate. The recognition ofT. salicornioides in western North America along with the absence of Tetraclinis in the fossil and recent floraof eastern Asia provide evidence for communication of the species across the North Atlantic during the earlyor middle Tertiary.

Keywords: cones, Cupressaceae, Europe, foliage, North America, paleobotany, Tertiary.

Introduction

The cupressaceous genus Tetraclinis Masters has a singleextant species, Tetraclinis articulata (Vahl) Masters, that isnative to warm, summer-dry climates of northern Africa,Malta, and southern Spain. In addition, the genus has an ex-cellent fossil record in the Tertiary of Europe based upon fossilcones, seeds, and foliage (Kvacek 1989; Kovar-Eder and Kva-cek 1995; Mai 1996). Two fossil species have been recognized:Tetraclinis brachyodon (Brongniart) Mai et Walther (Early Eo-cene to Early Pliocene) and Tetraclinis salicornioides (Unger)Kvacek (Middle Eocene to Early Pliocene), although some au-thors merge these species into a single entity (Mai 1996, 1997).In this article we recognize another representative of Tetraclinisfrom the Oligocene and Miocene of North America on thebasis of associated cones, seeds, and foliage similar to the Eu-ropean fossil T. salicornioides. This occurrence, as recentlyrecorded by Meyer and Manchester (1997), confirms that Te-traclinis was formerly distributed outside of Europe and north-ern Africa.

Tetraclinis has bilaterally symmetrical seed cones composedof four slightly uneven valvate scales and seeds that are basallycordate with a pair of large membranous wings. Leaves of thesingle extant species are arranged in pseudowhorls and arevery reduced, rather like those of incense cedar (Calocedrusdecurrens [Torr.] Florin). However, in the Tertiary of Europe,two kinds of foliage have been distinguished. Foliar branchlets

1 Author for correspondence; e-mail [email protected].

Manuscript received March 1999; revised manuscript received October 1999.

of T. brachyodon (Brongniart) Mai et Walther have reducedleaves that are difficult to distinguish from those of the extantspecies. Those of T. salicornioides are broader and more flat-tened and appear to be adapted to more mesic conditions. Thegeneric identity of these foliage types has been confirmed bythe recovery of specimens that show a physical connection withthe characteristic seed cones of Tetraclinis.

In this article we review the taxonomy and distribution ofthe North American population; provide a full description ofthe cones, seeds, and foliage (including new data from cuticularanalyses); and compare the North American population withother fossil Cupressaceae, including European representativesof Tetraclinis. Various morphological and molecular analysescorroborate the merger of the Cupressaceae and Taxodiaceaeinto one group (Eckenwalder 1976; Brunsfeld et al. 1994; Ste-fanovic et al. 1998). To avoid nomenclatural misunderstand-ing, we use the term “Cupressoids” in the sense of Cupres-saceae s.s. in the following text.

Material and Methods

Fossil leaves, seed cones, and seeds were observed in col-lections from the U.S. National Museum (USNM) in Wash-ington, D.C.; the University of California Museum of Pale-ontology (UCMP) in Berkeley; and the Florida Museum ofNatural History (UF) in Gainesville. Oligocene specimens arefrom the Lost Creek, Lyons, and Willamette floras of Oregon(Meyer and Manchester 1997) and the Gumboot Mountainflora of Washington (UCMP loc. PA 399). Miocene specimensare from the Eagle Creek (Chaney 1920), Mollala (Chaneyand Axelrod 1959), and Collawash (U.S. Geological Survey

332 INTERNATIONAL JOURNAL OF PLANT SCIENCES

Table 1

Localities for Tetraclinis salicornioides var. praedecurrens ShowingCo-occurrences of Foliage, Cones, and Seeds

Locality Foliage Cones Seeds

Oligocene:Lost Creek I, Oregon .. . . . . . . . . . . . . . . . . . x x xLost Creek II, Oregon .. . . . . . . . . . . . . . . . . . x x xWillamette, Oregon .. . . . . . . . . . . . . . . . . . . . x ) xLyons, Oregon .. . . . . . . . . . . . . . . . . . . . . . . . . . x ) xGumboot Mountain, Washington .. . . . . x ) )

Miocene:Potlatch Creek, Idaho .. . . . . . . . . . . . . . . . . . x ) xOviatt Creek, Idaho .. . . . . . . . . . . . . . . . . . . . x ) )Molalla, Oregon .. . . . . . . . . . . . . . . . . . . . . . . . x ) )Collawash, Oregon .. . . . . . . . . . . . . . . . . . . . . x ) )Eagle Creek, Oregon .. . . . . . . . . . . . . . . . . . . x ) )Spokane, Washington .. . . . . . . . . . . . . . . . . . x ) )Grand Coulee, Washington .. . . . . . . . . . . . x ) )

[USGS] loc. 9526; Peck et al. 1964) localities of westernOregon, the Potlatch Creek (Brown 1935) and Oviatt Creek(Boyd 1985) floras of Idaho, and the Latah (Knowlton 1926)and Grand Coulee (Berry 1931) floras of Washington. A listof the localities and the organs that have been collected isprovided in table 1.

Comparative material of Tetraclinis salicornioides var. sal-icornioides and T. brachyodon from the Tertiary of Europewas examined in collections the Museum National d’HistoireNaturelle in Paris (MNHN; collections of Brongniart and Sa-porta), the Museum fur Naturkunde der Humboldt-Universitatin Berlin (collection of D. H. Mai), the Museum Joanneum inGraz, Austria (collection of Unger), the Universitat Graz (col-lection of Ettingshausen) from the National Museum in Prague(NM), and Charles University (Faculty of Science) in Prague(PRC). These materials were supplemented by material fromthe other institutions acknowledged in Buzek et al. (1976),Knobloch and Kvacek (1976), and Kvacek (1989).

Cuticles were prepared for light microscopy using specimensfrom the Oligocene Willamette flora and the Miocene Latah,Potlatch Creek, and Mollala floras of Idaho. The cuticle wasmacerated with routine methods (Knobloch and Kvacek 1976),using Schultze’s solution and KOH (5%), and the cuticle wasthen studied with transmitted light and scanning electron mi-croscopy (SEM). Isolated cuticles for SEM were prepared byspreading the fragments on the moistened emulsion surface of4-mm-square pieces of photographic film that were subse-quently glued to the aluminum stubs.

Systematics

Family—Cupressaceae

Genus—Tetraclinis Masters

Tetraclinis salicornioides (Unger) Kvacek var.praedecurrens (Knowlton) comb. et stat. nov.

(Fig. 1A–1E, 1G, 1H; Fig. 2A–2G, 2I–2L;Fig. 3A–3E; Fig. 4A, 4C, 4D)

Basionym. Libocedrus praedecurrens Knowlton 1926,USGS Prof. Pap. 140:28, pl. 8, fig. 8 [foliage].

Synonyms. Fokienia praedecurrens (Knowlton) Chaneyand Axelrod 1959, Carnegie Inst. Wash. Publ. 617:145, pl.14, fig. 8 [foliage].

Callitris potlatchensis Brown 1935, J. Paleontol. 9:575, pl.67, fig. 16. Brown 1940, J. Wash. Acad. Sci. 30:347, fig. 6[seed].

Tetraclinis potlatchensis (Brown) Meyer and Manchester1997 (“potlachensis”), Univ. Calif. Publ. Geol. Sci. 141:64, pl.3, figs. 1–9 [seed and cone].

Fokieniopsis praedecurrens (Knowlton) Meyer and Man-chester 1997, Univ. Calif. Publ. Geol. Sci. 141:64, pl. 3, figs.10–14 [foliage].

Description. Cone wide-ovate, valvate; cone scales ap-parently four (but sometimes only three preserved) in opposingpairs, incompletely preserved, dimorphic, one pair ca. 1.3times wider than the other, thick and woody, widely ovate,length 7–8 mm, width 9–12 mm, base cordate, apex rounded;abaxial surface of cone scale with a mucro positioned ca. one-third of the distance from the base to the apex of scale; surface

of scale wrinkled, except for a smooth, broadly elliptical area(fused bract) at the base surrounding the mucro, hemisphericalin outline; adaxial surface of scales with fine striations radi-ating from the base.

Seed with two wings, symmetrical, reniform to broadlyovate, base cordate to sometimes truncate, apex obtuse torounded, overall width 7–12 mm, length 4–7.5 mm; wingsequal, much wider than seed body, thin, lateral marginsrounded; seed body ovate, apex acute, base rounded, length3–7 mm, width 2–3.5 mm, longitudinal striae radiating frombasal attachment scar and converging toward bilobed micro-pylar tip and demarcating elliptical resin vesicles.

Foliage twigs with mostly opposite branching. Branchletsflattened with four-ranked dimorphic scale leaves borne inpseudowhorls. Leaves dimorphic, facial and lateral scalelikeleaves with rounded to bluntly mucronate apices. Facial andlateral leaves of each pseudowhorl fused (usually) most of theirlength to form a cladode-like dorsiventrally flattened segment.Lateral leaves do not overlap between adjacent nodes, and thefacial leaves overlap only slightly or not at all. Segments cov-ered by stomata on both surfaces, cuticular membrane thick,leaves amphistomatic. Abaxial side of fused leaves composedof several longitudinal, vaguely differentiated nonstomatal andstomatal areas. Ordinary cells of nonstomatal areas quadran-gular-polygonal, usually much elongated, 35–100 mm long and20–30 mm wide. Anticlinal walls very regularly finely undulate(to straight); sinuses of the undulation with papilloid thick-enings. Longitudinal stomatal areas containing short rows ofclosely spaced stomata or irregularly oriented stomatal groupsseparated by nonstomatal areas. Stomata monocyclic, irreg-ularly oriented, stomatal pit quadrangular to polygonal, 20–30mm wide, including a thick Florin ring. Ordinary cells betweenstomata triangular to polygonal, more or less isodiametric,(12–) 30–37 mm across or quadrangular, elongate, 15–30 mmwide and up to 70 mm long. More or less distinct papillae instomatal areas, broad prominent papillae near the segmentbase. Small quadrangular crystal cavities in the cuticularmembrane observed near the terminal part of a foliar segment.Free tips or free margins of the scale leaves with marginalpapillae forming prominent crests. Cuticles of adaxial side of

KVACEK ET AL.—CUPRESSACEAE IN THE NORTH AMERICAN TERTIARY 333

Fig. 1 Cones and seeds of Tetraclinis. A–E, Tetraclinis salicornioides var. praedecurrens from the Oligocene of Lost Creek Reservoir, Oregon,#2.5. A, Cone in lateral view showing apically rounded basally cordate cone scale and the attachment to stalk with free-tipped foliar segments;USNM 450636. B, The same cone as in fig. 1A, with portion of the facing cone scale removed to show the pair of lateral cone scales behind.C, An opened cone transversely compressed, with three of the cone scale visible; UF 10152. D, One large lateral cone scale (right) and a pairof opened cone scales (top and bottom), showing position of the mucro; UF 10151. E, Counterimpression of the specimen in fig. 1D, showingthick, woody nature of the cone scales. F, Extant Tetraclinis articulata, apical view, showing the four cone scales, Algeria; US 2039727, #3.G, Seed showing two wings attached to ovate seed body, proximal ends of the wings truncated by folding; UF 10163, #3. H, Another seedshowing longitudinal resin vesicles on the seed body and large lateral wings; UF 10164, #3. I, European specimen for comparison: cones of T.salicornioides var. salicornioides from Suletice, Czech Republic; NM G7535A, #2.5. J, Cone of extant T. articulata (Vahl) Masters fromMarrakech, Morocco (PRC), lateral view, #2.5. K, Seed of T. salicornioides var. salicornioides from Markvartice, Czech Republic; NM G2785,#4. L, M, Seeds from the cone in fig. 1J, #2.5.


Fig. 2 Foliar branches of T. salicornioides var. praedecurrens and salicornioides, all #2.5. A–G, T. salicornioides var. praedecurrens. A, Typeof Knowlton 1926, pl. 8, fig.8, p. 28, from Miocene of Latah flora, Spokane, Washington; USNM 36873. B, Branch from the Oligocene Lyonsflora, Oregon, showing opposite ultimate branches; USNM 450640. C–G, From Oligocene of Lost Creek Reservoir, Oregon. C, Twig showingopposite branching with cuneiform medial segments giving rise to ultimate branches with simple, obovate segments; UF 10158. D, Elongatesegments from proximal part of shoot showing arrested lateral growth and free tips of the lateral leaves; UF 10161. E, Series of elongate foliarsegments from the proximal part of a twig; UF 10160. F, Similar twig with more robust segments; UF 10159. G, Succession of three medialcuneiform foliar segments; UF 10153. H, T. salicornioides var. salicornioides shoot from Kundratice showing three kinds of foliar segments:narrow elongate proximal segments and cuneiform medial segments giving rise to simple lateral ultimate segments; NM G 2172. I–L, Isolatedfoliar segments of T. salicornioides var. praedecurrens from Lost Creek Reservoir, Oregon. I–K, Cuneiform segments of the branch junction,showing five main veins. I, UF 10154. J, UF 10155. K, UF 10157. L, Segment of an ultimate branch with three veins; USNM 450637.


Fig. 3 Cuticle of Tetraclinis salicornioides. A, Medial cladode-like segment of T. salicornioides var. praedecurrens from which cuticle wasremoved for epidermal anatomy, from Potlatch Creek, Idaho; UF10887, #5. B, A lateral segment, cleared showing incomplete fusion of leaves,from Oviatt Creek, Idaho; UF 18580-31378, #5. C, Free tip of the lateral leaf, lying on dorsal surface, showing adaxial and abaxial cuticlefolded together with stomata on each; USNM 36873 (prep. 1), #40. D, Facial leaf, abaxial surface showing groups of closely spaced stomata;USNM 36873 (prep. 1), #200. E, Cuticle from near the base of segment in fig. 3A, showing longitudinally aligned epidermal cells and thearrangement of stomata in rows, #200. F, T. salicornioides var. salicornioides from the Oligocene site Markvartice, western Czech Republic,for comparison with the North American specimens; PRC MR 134-B, #200. G, Same as fig. 3E, by phase-contrast light microscopy, showingthe papillate nature of the epidermal cells, #400.

leaves thin, finely papillate, densely covered with stomata ofthe same type as that seen on the abaxial surface.

Holotype. USNM 36873, railroad cut in Spokane, Wash-ington, Miocene Latah flora, Washington (Knowlton 1926),fig. 2A; fig. 3C, 3D.

Additional specimens. Oligocene—UF 10153-10158,10161, 10575; USNM 450637; UF 10162-10165; USNM42333; UF 10151, 10152, 10576; USNM 450636 (Lost Creek,Oreg.; UF localities 243, 244); UF 9086; USNM 450641,450644 (Willamette flora, Oreg.; UF locality 15784). Mio-cene—UF 10887 (Potlatch Creek, Julietta, Idaho; UF locality18597); UF 26762, 26763 (Lower Salmon River, Idaho; UFlocality 18598); UF 31378 (Oviatt Creek, Idaho; UF locality18580); UCMP 4421 (Mollala, Oreg.); Field Museum Chicago22335 (Eagle Creek, Oreg.).

Additional localities. In addition to the localities indicatedabove, specimens are known from the Miocene floras of Col-lawash, Oregon, and Grand Coulee, Washington (Chaney andAxelrod 1959).

Discussion. In the above description, we combine theseeds previously assigned to C. potlatchensis Brown with the

foliage previously called F. praedecurrens (Knowlton) Chaneyand Axelrod, together with the associated cones, under thenew combination T. salicornioides var. praedecurrens. Thecombination of these organs under the same name is justifiedby the co-occurrence of the seeds and foliage at five localities,by the co-occurrence of the cones, seeds, and foliage at twolocalities (table 1), and by the previously recognized co-occurrence and physical attachment of similar foliage, cones,and seeds of T. salicornioides in the Tertiary of Europe (Kvacek1989).

Brown (1935, 1940) was the first to recognize the cupressoidaffinity of the seeds from the Miocene of Idaho and the Oli-gocene of Oregon, and he named them C. potlatchensis. Hisgeneric assignment was based upon a correct comparison withthe extant Tetraclinis articulata (Vahl.) Masters, which waspreviously placed under the synonym Callitris quadrivalvisVentenant. Although not found in situ within the cones, theassociated seeds coincide in size and configuration with thearea for seed attachment within the fossil cones, thereby sup-porting our conclusion that the cones and seeds represent thesame species. The cones and seeds are remarkably similar to


Fig. 4 Cuticle of Tetraclinis salicornioides in SEM. A, T. salicornioides var. praedecurrens. Inner side of cuticle showing anticlinal walls ofordinary cells with thickenings, Potlatch Creek, Idaho; UF 10887, #500. B, T. salicornioides var. salicornioides from the Early Miocene ofPlesna, western Czech Republic, for comparison with the North American specimen, inner side of cuticle showing strongly papilla-like thickeningson anticlinal walls of ordinary cells and a stoma; PRC V-146-112, #500. C, T. salicornioides var. praedecurrens, outer side of the cuticle,showing stomata and papillae; UF10887, #500. D, Same, enlarged to show stomatal aperture and surrounding Florin ring; UF10887, #1500.

those of T. salicornioides (Unger) Endlicher from the Tertiaryof Europe (Kvacek 1989; Kvacek and Walther 1995).

Only four seed cone specimens have been recovered fromthe North American record, and they are all from the Oli-gocene Lost Creek locality of the Bridge Creek flora in Oregon(Meyer and Manchester 1997). One is compressed laterally(fig. 1A, 1B), and the others are compressed transversely orslightly obliquely with the scales opened (fig. 1C–1E). One ofthe specimens shows only three enlarged cone scales, indicatingthat one was arrested in development, as is also sometimesobserved in the European fossil and extant cones of Tetraclinis(Zablocki 1928, pp. 188–189).

Cones with four dimorphic valvate cone scales provide de-cisive support for the assignment of these fossils to Tetraclinis.The fossil seeds also compare favorably with those of extant

Tetraclinis in their bisymmetry, cordate base, large wings, andresin vesicles on the seed body. As in the European fossils ofT. salicornioides (Kvacek 1989), the North American seeds areless prominently cordate than are the seeds of extant T. arti-culata. The lower position of the mucro on the abaxial surfaceof the cone scale provides an additional character that distin-guishes these fossils from the modern species and that under-scores the similarity with the European fossils. In extant T.articulata, the mucro usually occurs in the upper one-fourthof the cone scale, near the apex. In the two cones in whichthis can be observed among the Lost Creek specimens (fig. 1A,1D), the mucro is situated ca. one-third of the distance fromthe base toward the apex of the cone scale. In the Europeanrepresentatives of T. salicornioides, the mucro ranges in po-sition from the lower one-third (Kelber and Gregor 1987, pl.


3, fig. 3) to a maximum of one-half of the length of the conescale (Schloemer-Jager 1960, pl. 1, fig. 15).

Foliage of T. salicornioides var. praedecurrens was formerlyassigned to Fokienia based on similarities in leaf morphologyby Chaney and Axelrod (1959). However, in the living Fok-ienia hodginsii Dunn, the branch segments are concave on theunderside (rather than biconvex), the leaves are not fused, andthe apices of facial and lateral leaves are more acute (McIverand Basinger 1990, pp. 1613–1614, figs. 16, 17). As observedby Meyer and Manchester (1997), the fossil foliage from theseNorth American localities is morphologically indistinguishablefrom that of the widespread European Tertiary species T.salicornioides.

Until being recognized as Tetraclinis—a recognition that wasinfluenced by the attached cones and associated seeds (Kvacek1989)—the European foliage specimens were considered tobelong to an extinct genus, for which the names Hellia Unger[nom. invalid: generic diagnosis lacking; three species wereattributed to the genus, but a generitype was not designated](e.g., Mai 1963; Friis 1977) and Libocedrites Endlicher (e.g.,Knobloch and Kvacek 1976; Mai and Walther 1978; Pala-marev et al. 1991; Wilde and Frankenhauser 1998) had longbeen applied. We use the term cladode-like in reference to thefoliar branch segments. They are distinguished from true clad-odes (derived from branches without leaves) by their derivationfrom leaves plus the branch. The cladode-like segments consistof mutually fused dimorphic scale leaves borne in pseudo-whorls. The nearly complete fusion of lateral and facial leavesdoes not occur among extant Cupressaceae (not even in theextant species of Tetraclinis) but does occur in both the Eu-ropean and North American populations of T. salicornioides.

The cladode-like branches typically disaggregate at succes-sive nodes into short segments that may be found dispersed inthe sediment (fig. 2I–2L; fig. 3A, 3B). These internode seg-ments occur in four forms: the first are simple segments fromthe ultimate portions of twigs and branches (e.g., fig. 2A–2C).They are elliptical or obovate and have three main veins (e.g.,fig. 3B). The second kind are medial segments that representthe junctions at which one or two side branches arise (e.g.,fig. 2A, 2H–2K; fig. 3A). They are obovate to wedge shaped,with a jagged distal end and five visible veins, the outer pairof which are similar to those of the ultimate segments and theinner pair of which leads to the branches. The third kind arenarrow segments situated in the proximal portion of the shoot.They are approximately parallel sided over most of their lengthbut are abruptly enlarged distally, with free tips on the lateralleaves, which subtend arrested axillary branches (fig. 2D–2F).The fourth kind of segment, which is typically situated belowthe cones, is shorter, less dimorphic, and has free tips (fig. 1A,1B). As a result of fusion, the boundaries between individualleaves cannot be discerned further down the segment, exceptin rare cases of incomplete fusion (e.g., fig. 3B; Friis 1977)and in branches bearing cones (Kvacek 1989).

Friis (1977) made detailed comparisons of T. salicornioides(Unger) Kvacek (as Hellia salicornioides) foliage segments withextant cupressoid genera and observed some agreement withextant T. articulata, both in terms of epidermal structure andin the external and internal morphology. She noted, however,that the extant species is distinguished by markedly xero-morphic characters with deeply depressed stomatal bands and

without stomata on exposed surfaces. Tetraclinis salicornioideshas wider leaves covered by stomata on the abaxial sides, andit bears dense stomata on the adaxial sides of the free partsof leaves. These features are consistent with the mesic habitatthat can be inferred for both varieties of T. salicornioides,based upon the floristic associations in which they occur.

We consider it appropriate to place the North Americanmaterial in the same species as the European fossils, T. sali-cornioides, because the morphology of the foliage and of theseeds fully coincides. Although the geographic disjunctionmight lead one to expect distinct species, the morphologicaldifferences are slight. The cones tend to be slightly larger inthe North American specimens, but this may be attributed todifferences in preservation type (impression vs. compression),and there is overlap in the dimensions (cone width 9–12 mmvs. 3–10 mm). Without the aid of leaf cuticular characters(mainly stomatal arrangement), it would be difficult to makeany distinction between the North American and Europeanpopulations.

Varietal status for the North American material is supportedby differences in epidermal anatomy. In the European material,the arrangement and shape of epidermal cells are less regularthan in the North American Miocene material. The anticlinalwalls usually bear thickenings and are more intensively un-dulate (figs. 3F, 4B vs. fig. 3D, 3E, and fig. 4A), and thepericlinal walls more often have distinct papillae. Stomata aregenerally more widely scattered. However, the epidermal char-acters of the Oligocene foliage (from the Willamette flora) areless different from the type European representatives of thespecies. This indicates an increasing divergence of the Euro-pean and American populations that may have arisen follow-ing their geographical separation.

Conspectus of the Fossil Representatives of Tetraclinis

Some authors (Mai 1997, 1998; Ferguson et al. 1998) main-tain that only a single species, Tetraclinis brachyodon (includ-ing Tetraclinis salicornioides), existed in the European Tertiary.However, in our investigation of numerous fossil occurrencesof Tetraclinis, we confirmed that there are indeed distinguish-ing criteria (in both the seed cones and the foliage) that supportrecognition of the two species, as indicated in the key anddescriptions below.

Diagnostic key to fossil Tetraclinis species:I. Branching mostly alternate, leaf fusion incomplete, sto-

mata lacking on abaxial side, bract of the seed cone elongate,mucro on abaxial surface of seed cone scale typically subter-minal ) Tetraclinis brachyodon (Brongniart) Mai et Walther

II. Branching mostly opposite, leaf fusion mostly complete,stomata present on abaxial side, bract of the seed cone broaderthan long, mucro typically subcentral to subbasal ) Tetraclinissalicornioides (Unger) Kvacek

Tetraclinis brachyodon (Brongniart) Mai et Walther (syn.Thuytes callitrina Unger, Callitrites brongniartii

Endlicher, nom. illegit. superfl.)

Morphology and anatomy. This species is based on steriletwigs from Middle Eocene strata in Paris–Mont Rouge/Cha-tillon (lectotype: Brongniart 1822, pl. 5, fig. 3A, no. 78, Mus.


Nat. Paris; see fig. 5E). Its leaf segments are nearly isomorphic,very slender, arranged in pseudowhorls with 2 (–4) subparallellongitudinal grooves marking the junctions of incompletelyfused scale leaves (fig. 5E, 5F, 5K, 5L). Branching is alternateand rarely opposite. The abaxial epidermis is composed ofnonpapillate straight-walled cells, with stomata confinedmostly to the grooves between the scale leaves (Givulescu1975; Kvacek 1989; our fig. 5M). Seed cones (from variouslocalities, including Armissan, Aix-en-Provence, St. Zacharie,Radoboj, and Haring; e.g., our fig. 5A–5D, 5G) are broadlytruncate conical to globular, attached singly to the twigs; thefused bract elongate, ascending often more than two-thirds ofthe cone scale length and mostly indistinct, with a subterminalto rarely subcentral umbo. Seeds (fig. 5H, 5I) bilaterallywinged, deeply to shallowly cordate, rarely truncate.

Occurrence and stratigraphic range. Europe to Trans-caucasia, Early Eocene to Early Pliocene.

Tetraclinis salicornioides (Unger) Kvacek (syn. Libo-cedrites salicornioides [Unger] Endlicher)

Morphology and anatomy. This species is typified by ster-ile twigs from the Miocene of Radoboj (lectotype: Unger 1841,pl. 2, fig. 1, no. 76680, Landesmuseum Joanneum, Graz, Aus-tria). Leaf segments are more or less broad and well flattenedand remarkably polymorphic according to their positionwithin sprays. They consist of fully fused scale leaves in pseu-dowhorls, with grooves between lateral and facial leaves barelyvisible in the uppermost part of the segments (fig. 2B–2L) or,more rarely, reaching toward the segment base (e.g., Friis 1977;our fig. 2A). Branching is opposite to rarely alternate. Abaxialepidermis composed of more or less strongly papillate cellswith finely undulate anticlinal walls and stomata in irregulargroups or longitudinal lines over the whole surface of the seg-ments (figs. 3B–3G, 4A–4D). Seed cones are rarely found inattachment to the twigs (from the localities of Haselbach,Suletice-Berand, Florsheim, and Kreuzau), singly or in pairs.They are broadly ovate (broader than long), and the fusedbract is broader than long and roundish to broadly cordatewith a subbasal to subcentral umbo (fig. 1A–1F). Bilaterallywinged seeds are shallowly cordate to truncate (fig. 1G, 1H,1K).

Occurrence and stratigraphic range. Variety salicornioidesis distributed from Europe to Transcaucasia, Middle Eoceneto Early Pliocene (Kvacek 1989). The second variety, prae-decurrens, discussed below, is distributed in western NorthAmerica.

Tetraclinis salicornioides (Unger) Kvacek var.praedecurrens (Knowlton) Kvacek andManchester, comb. et stat. nov. (syn.Libocedrus praedecurrens Knowlton,

Callitris potlatchensis Brown)

Morphology and anatomy. This variety is based on a ster-ile twig from the Miocene Latah flora in Washington (holotype:Knowlton 1926, pl. 8, fig. 8, USNM 36873; our fig. 2A; fig.3C, 3D). It differs from the type variety only by its epidermalanatomy, consisting of more regular arrangement and shapeof epidermal cells, less distinctly thickened and less intensively

undulate anticlinal walls, and stomata that are more closelyspaced and in more regularized rows (figs. 3E, 4A).

Occurrence and stratigraphic range. Western UnitedStates, Oligocene and Miocene (Meyer and Manchester 1997).

Contrary to the opinions of some authors (Friis 1977;Palamarev et al. 1991; Wilde and Frankenhauser 1998; E. M.Friis, personal commmunication, 1998), the above differencesprobably do not warrant the assignment of T. salicornioidesto an extinct genus (i.e., Libocedrites Endlicher). The combi-nation of quadrivalved seed cones with noncolumellate di-morphic cone scales and with bilaterally broadly winged seedsis unique among the Cupressoids and is diagnostic of extantTetraclinis (Krausel 1938; Mai and Walther 1978; Kvacek1989; Martinetto 1995; Mai 1997; Meyer and Manchester1997). We chose to consider the unusual cladode-like foliageand branching pattern of T. salicornioides as features of sub-ordinate taxonomic value. In fact, some rare foliage formsmentioned above (fig. 2A) intergrade morphologically with thetypical foliage of T. brachyodon. The latter fossil speciesmatches extant T. articulata in most respects, both in its foliageand seed cones. The close linkage between T. salicornioides,T. brachyodon, and T. articulata weakens the argument fortreating any part of this complex as an extinct genus.

Cones of Cupressinites curtus Bowerbank (Tetraclinis curta[Bowerbank] Mai 1997) from the Early Eocene London Clayflora appear, based on the published descriptions and illustra-tions (Bowerbank 1840), to be similar to Tetraclinis, and withadditional study, they may provide important informationabout the early differentiation of the Tetraclinis cone mor-phology. D. H. Mai (personal communication, 1997) studiedthe available material and did not hesitate to include it intoTetraclinis. However, these cones are reported to be up to five-scaled (Collinson 1983), and no information on their foliageis available.

Cones and Seeds of Cupressaceae

The small number of cone scales and their decussate (ratherthan helical) arrangement, combined with their highly fusedbract and scale, are features that confirm the affinities of thesefossils with the Cupressoids. Seed cones of extant Cupressoidsrange from more or less globular to elongate and may havepeltate, imbricate, or valvate cone scales that may be woodyto leathery or fleshy. Verticillate arrangement of scales occursin some Callitroidae of the Southern Hemisphere. The com-bination of globose cones and four valvate, unequal, woodycone scales, combined with the peculiar broadly elliptic andbasally cordate seeds, indicates an affinity to extant Tetraclinis.

Seeds of Cupressaceae are relatively consistent within eachnatural genus and provide characters of diagnostic value, par-ticularly in terms of the disposition and form of the wings.The most common type of seed has two narrow wings (e.g.,Chamaecyparis, Thuja, Thujopsis, Cupressus, and Neocalli-tropsis). The wings may be fully reduced, rarely in a form ofnarrow longitudinal rims (Platycladus, Microbiota, and Jun-iperus), or subapically extended (Calocedrus). Wings of Fok-ienia seeds are rather unequal, spreading, and variable in size.Seeds of some of the Southern Hemisphere genera are distin-guished by the presence of three wings (Fitzroya and Actino-strobus), and others have a single main wing, with a second


Fig. 5 Cones, seeds, and foliage of Tetraclinis brachyodon from the European Tertiary for comparison with Tetraclinis salicornioides. A,Seed cone on twig showing subcentral umbo, small seed cone on twig with subcentral umbos, St. Zacharie, Oligocene; MNHN ZK2, #2.5. B,Small cone with subterminal umbos, St. Zacharie, Oligocene; MNHN ZK3, #2.5. C, One cone of several attached to a twig, Radoboj, MiddleMiocene (orig. Kovar-Eder and Kvacek 1995); Univ. Graz 11424, #2.5. D, Larger cone, Armissan, Upper Oligocene; MNHN 11155, #2.5.E, Lectotype of T. brachyodon, Paris–Mont Rouge/Chatillon, Middle Eocene (orig. Brongniart 1822, pl. 5, fig. 3A); MNHN 78, #2.5. F, Twigshowing alternate branching typical of this species; MNHN s.n., #1. G, Widely opened cone, Aix-en-Provence, Oligocene-Miocene boundary;MNHN s.n., #2.5. H, Seed with deeply cordate base, St. Zacharie; MNHN ZK8, #2.5. I, Seed with very truncate base, Armissan, UpperOligocene (orig. Saporta 1862, pl. 1, fig. 6C); MNHN 11157, #2.5. J, Twig with two terminal male cones (?), Oligocene, St. Zacharie; MNHN16320, #2.5. K, Slender twig, Arcueil, Middle Eocene (orig. Watelet 1866, pl. 32, fig. 3); MNHN 7828, #2.5. L, Detail from fig. 5F, #2.5.M, Abaxial cuticle of the specimen shown in fig. 5F and 5L, #250.

wing that is much reduced (Libocedrus, Austrocedrus, andPilgerodendron). The most common type of seed has twowings that may form only a narrow longitudinal rim (e.g.,Chamaecyparis, Thuja, Thujopsis, Cupressus, and Neocalli-tropsis). The wings may be fully reduced (Platycladus, Micro-biota, and Juniperus) or apically enlarged and fused (Calo-cedrus). Wings of Fokienia seeds are rather unequal, spreading,

and variable in size. Seeds of some of the Southern Hemispheregenera deviate by the presence of three wings (Fitzroya andActinostrobus), and others have only a single large lateralwing, with the other wings being markedly reduced or absent(Libocedrus, Austrocedrus, and Pilgerodendron). In Tetra-clinis, the seeds are principally biwinged, with wings expand-ing basally (e.g., fig. 1L, 1M), but the two innermost seeds of


the cone bear a third wing in the form of a slight medial keel.The unique form of Tetraclinis seeds among the Cupressoidsprovides an important character for the identification of fossilrepresentatives.

Foliage of Cupressaceae

The Cupressoids may have either decussate or verticillatephyllotaxy, but the foliar morphology is variable in terms ofmany features. Pronounced variation occurs during ontogeny,such that acicular leaves (free or partly decurrent) are typicallydeveloped in young stages but survive only exceptionally onadult plants (e.g., Juniperus subg. Juniperus). The acicular fo-liage type tends to make transitions through ontogeny to thescale leaves that prevail in the adult foliage of most genera.Even in mature foliage, there may be considerable foliar var-iation according to position within the shoot system. As a rule,scale leaves of the stalks of seed cones tend to be reduced,shortened, and radially disposed. Branches in cross section maybe either biconvex (tetragonal; octagonal in Neocallitropsis),with more or less homomorphic leaves (e.g., Cupressus andFitzroya), or more or less flattened (to convex-concave) andeither more or less homomorphic (e.g., Pilgerodendron andThujopsis) or with dimorphic leaves (e.g., Fokienia). Even epi-dermal characteristics are of limited value for generic distinc-tions within this family (Florin 1931). Therefore, botanistsdealing with this group of conifers generally prefer the char-acters of seed cones for classification of the family and fordistinction of genera (e.g., Li 1953; Gaussen 1968).

In the Cupressaceae, foliage morphology can vary amongspecies of the same genus (Calocedrus decurrens vs. Calocedrusmacrolepis, Calocedrus formosana). Conversely, multiple gen-era may share the same type of foliage (Chamaecyparis andThuja; Cupressus and Juniperus). Branching patterns are alsovariable within a genus or even a species (Rouane 1973). Op-posite branching is characteristic of some Southern Hemi-sphere Cupressoids (Libocedrus and Austrocedrus), but it oc-curs occasionally in other genera. Opposite branching wasused as an argument by Heer (1855, 1870) and others to assignfossil sterile branches to Libocedrus. However, studies of fossilfoliage with associated or attached cones have revealed thatopposite branching was widespread in various genera of an-cient Cupressoids (McIver 1994).

Leaves of extant Cupressaceae are never fully fused to formcladode-like segments; however, this condition is now knownin two fossil taxa: Tetraclinis salicornioides and Fokieniopsiscatenulata (Bell) McIver et Basinger. Both species are similarin branching architecture and in the presence of fused foliarsegments. They differ in epidermal anatomy and cone mor-phology. It might be tempting to use the specialized feature offully fused, cladode-like segments to relate both taxa. However,this may be a case of convergent or parallel evolution, as istypical of both extant (Chamaecyparis and Thuja) and extinct(Mesocyparis and Chamaecyparis corpulenta) members of thisfamily.

Most Cupressoids show distinct Florin rings around the sto-matal cavity and often also show distal papillae on ordinarycells (Oladele 1983). These characters help distinguish the Cu-pressaceae from the Cheirolepidiaceae, which shows papillaeoverlapping the stomatal pits. Distinct Florin rings and papillae

on ordinary cells are clearly developed in both European andNorth American records of fossil Tetraclinis foliage. Distri-bution and arrangement of stomata provide additional diag-nostic characters, but they are not as reliable since they areinfluenced by exposure in light (Fitting 1942). Kvacek (1989)reasoned that the differences in stomatal topography betweenthe species of Tetraclinis probably arose as a result of ecolog-ical factors, such as adaptation to light conditions and hu-midity. In Tetraclinis brachyodon, which occurs earlier in thefossil record (Early Eocene to Early Pliocene), the foliage isonly slightly heteromorphic, and the stomata are confined tothe adaxial surface of the leaf and the area adjacent to the leafmargin. In contrast, the stomata of T. salicornioides (MiddleEocene to Early Pliocene) are scattered all over the surface ofsegments (see Friis 1977), which indicates conditions of diffuselight in closed forests. Tetraclinis brachyodon and T. salicor-nioides commonly occur together, although in indirect pro-portion. Tetraclinis brachyodon grew abundantly in moresoutherly localities in the European Tertiary (Aix-en-Provence,Armissan, St. Zacharie, Haring, Kumi, and Radoboj), whichare associated with subhumid forest vegetation (open semi-evergreen sclerophyllous woodland sensu Mai [1994]). The“xeromorphic” character of the genus has become most pro-nounced in the Mediterranean (summer-dry) type of climate,where Tetraclinis articulata occurs today.

Review of Other Fossil Cupressaceae in Relationto Tetraclinis salicornioides

Putative Cupressoids have been reported from the Jurassicand Early Cretaceous, but there is no convincing evidence ofthis group until the Late Cretaceous. Many of the fossils withdecussate scale leaves similar to those of the Cupressoids canbe distinguished as members of the extinct Cheirolepidiaceae,because the cuticle reveals a papillate rim overlapping the sto-matal pit. Examples include Cupressinocladus ramonensisChaloner et Lorch (1960), Cupressinocladus micromerum(Heer) Pais (1974), and Paleocyparis flexuosa Saporta et Mar-ion teste Neves (1950). A comprehensive revision of such fos-sils is needed to elucidate the earliest records of true Cupres-saceae. One of the Cretaceous fossils formerly assigned toChamacyparis is Chamacyparis cretacea Velenovsky et Vinik-lar from the Cenomanian of Bohemia (Velenovsky and Viniklar1926). Inspection of the type specimens revealed helically ar-ranged needle-like leaves and associated Sequoia-like cones (Z.Kvacek, personal observation). Libocedrus salicornioides cre-tacea Velenovsky (1885) represents a poorly preserved conescale of “Dammara” borealis Heer (Kvacek 1989).

In his classification of the Cupressaceae and Taxodiaceae,which were merged into one family, Eckenwalder (1976) ex-pects primitive traits of the cupressoid group from theNorthern Hemisphere: globular, many-scaled seed cones; cru-ciate, terete branchlets; and arborescent habit. He considersCupressus to be most similar to the probable ancestor of thetribe Cupresseae, from which some members of his subtribe4, namely Tetraclinis, Widdringtonia, Libocedrus, and Aus-trocedrus, “could have originated ) by reduction of the twopairs of ovuliferous cone scales” (Eckenwalder 1976, p. 252).In the view of McIver and Aulenback (1994), however, theearliest known cupressoid seed cones from the Cretaceous bore


four scales, thus differing markedly from the many-scaled Cu-pressus-like cones of the hypothetical ancestor. The first recordof Cupressus-like cones with many scales was not found untilthe late Paleocene or early Eocene (Cupressoconus machenryi(Baily) Boulter et Kvacek [1989] from Ireland). More studieson the cones of Cretaceous conifers are needed to trace thehistory of the Cupressaceae. In this respect, WiddringtonitesEndlicher (W. reichii [Ettingsh.] Heer) and Tetraclinopsis Boyd(T. paututensis Boyd), which have noncolumellate cones with4 [–5] woody valvate cone scales (see Boyd 1992) but helically(?) disposed scale leaves on twigs deserve attention.

Among the Upper Cretaceous foliage with decussate phyl-lotaxy, those showing Florin rings around the stomatal pitsmost likely belong to the Cupressoids. Some of these shootsbear cones. The most common fossils of this kind have beenassigned to Thuja cretacea (Heer) Newberry, were distributedat high latitudes of the Northern Hemisphere (Samylina 1988),and ranged into the Early Tertiary (Thuja ehrenswaerdii [Heer]Schweitzer, Thuja polaris McIver and Basinger). Their coneshave imbricate scales that are similar in most respects to thoseof extant Thuja species (McIver and Basinger 1989). Meso-cyparis (McIver and Basinger 1987; McIver and Aulenback1994; syn. Microconium Golovneva 1988, 1994) differs fromthe extant Cupressoids in that it bears cones in decussate ordistichous pairs. Its globular quadrivalvate and columellatecones resemble those of Chamaecyparis nootkaensis (D. Don)Spach in possessing four more or less equal cone scales (McIverand Aulenback 1994). A true Chamaecyparis, with minutecones of four nearly equal scales, was described from the LateCretaceous of Canada (McIver 1994). None of these taxa hasa foliage with cladode-like segments.

Another species with cladode-like foliar branches resemblingthose of Tetraclinis salicornioides occurs in the Cretaceous andPaleocene and has gone under the names Androvettia caten-ulata Bell, Ditaxocladus planiphyllus Guo et Sun, Fokieniacatenulata (Bell) Brown, Fokienia ravenscragensis McIver etBasinger, Fokieniopsis catenulata (Bell) McIver et Basinger, andLibocedrus catenulata (Bell) Kryshtofovich. It is known fromCanada (Bell 1949; Brown 1962; McIver and Basinger 1990)and from central and eastern Asia (Kryshtofovich and Bai-kovskaya 1966; Romanova 1975; Guo et al. 1984; Samylina1988). Subglobose seed cones with eight to 10 woody scaleswere attached to twigs of this foliage in opposite pairs, as wasobserved in specimens from Saskatchewan (McIver 1992) andXinjiang (S. R. Manchester and S.-X. Guo, unpublished data,1995). Additional comparative work and careful attention tothe nomenclatural rules of priority are needed to verify theappropriate binomial for this species, but for purposes of dis-cussion in this article, we refer to it as F. catenulata (Bell)McIver et Basinger. The seed cones differ from the those ofextant Fokienia Henry et Thomas based on their scales, whichare valvate basally and spatulate to subpeltate apically. Theseeds of this plant remain uncertain. In some cases, the as-sociated seeds illustrated by McIver (1992) show a spinulosewing margin—a character not known in extant coniferousseeds.

Although F. catenulata resembles T. salicornioides by itscladode-like segments, the sterile foliage of the two taxa maybe distinguished by subtle, partly overlapping differences: inF. catenulata, the branch systems are more slender in outline,

the veins to lateral branches often arise well above the baseof the medial leaf segments (Kryshtofovich and Baikovskaya1966, pl. 6, fig. 3; Guo et al. 1984, pl. 1, fig. 5a; McIver1992, text, fig. 1), and the epidermis is nonpapillate andshows straight-walled cells and short rows and groups ofstomata with only narrow Florin rings. In T. salicornioides,the branch system is usually fan shaped (Engelhardt 1886;Ferguson 1971), the pair of vascular bundles leading to thelateral branches arises more often at the base of the leafsegment (fig. 2I–2L), the cuticle is mostly papillate, the cellwalls are usually undulate with thickenings, and the stomataare arranged in longer rows within several longitudinal sto-matal areas. Stomata bear thick Florin rings. In extant Fok-ienia, the foliage is not fused or cladode-like, and the scaleleaves have more densely spaced stomata that occur in nar-row, well-demarcated bands (Florin 1931, pp. 438–440; Z.Kvacek, personal observation).

We studied cuticle from leaves of F. catenulata (Bell) McIveret Basinger from the Paleocene Fort Union Formation of SandDraw, Wyoming (UF locality 18131) for comparison with theT. salicornioides fossils. The specimens examined included apart of the ultimate branch and a large medial segment. Cuticleof the cladode-like segments in F. catenulata is much thinnerthan that of T. salicornioides and lacks papillae. The ordinaryepidermal cells are straight walled to very slightly and finelyundulate, polygonal-quadrangular, and usually isodiametric orup to three times longer than wide (width 15–25 mm, length25–50 mm), becoming narrower and longer on the edges ofthe cladode-like segment. The monocyclic stomata form shortlongitudinal and irregular groups in stomatal areas. The sto-mata are irregularly oriented with apertures that are (12–) 20mm wide and (17–) 25 (–30) mm long and are bordered by athin Florin ring.

The foliar similarities between F. catenulata and T. salicor-nioides can be explained by parallel evolution because theircones are different. The attached cones of Fokieniopsis, calledFokienia ravenscragensis by McIver et Basinger (1990), havetwice as many decussate scales and are borne in opposite pairs.The Tetraclinis fossils have four-scaled cones borne singly orin pairs on the twigs in T. salicornioides (Ferguson 1971; Kva-cek and Walther 1995) or singly in T. brachyodon (Kovar-Ederand Kvacek 1995). Basal cone scales are more or less cordate,and their form is reflected in the shape of the winged seeds.

Biogeographic Considerations

In most systems of conifers, Tetraclinis is classified close tothe group of Afro-Australian genera of the Cupressaceae (Wid-dringtonia Endl., Actinostrobus Miq. ex Lehm., and CallitrisVent.), although it “stands out amongst these as perhaps muchless close to the others” (Page 1990, p. 305). Although someauthors have favored a Southern Hemisphere origin for Te-traclinis (Hart 1987), the fossil record demonstrates that thegenus had a substantial distribution in the Tertiary of theNorthern Hemisphere. Mai (1994, 1997, 1998) indicated thatTetraclinis brachyodon and T. salicornioides were not clearlydistinct species. However, no brachyodon-like foliage has beenrecovered so far in the North American localities of Tetraclinis.Tetraclinis brachyodon tends to have more flattened foliar


shoots, up to three male cones (Saporta 1862), and largerumbos (Gaussen 1968).

The distribution of T. salicornioides indicates that the speciesmust have migrated between western North America and Eu-rope during the early or middle Tertiary. Although it extendedthrough Europe to the Transcaucasus area (Kvacek 1989; Mai1994, 1995; Kovar-Eder et al. 1996), the absence of Tetraclinisfrom localities east of the Caspian Sea indicates that the genusdid not cross Asia. (Z. Kvacek examined the specimen iden-tified as Libocedrus salicornioides from core 138 near theKrugloe Sea, Kazakhstan [Zhilin 1974, p. 97] and observedthat the twig fragment does not consist of cladode-like seg-ments and corresponds most likely to Chamaecyparis orThuja.) Therefore, we infer that T. salicornioides communi-cated directly between Europe and North America, apparentlyacross the North Atlantic. Based upon shared occurrences inthe early Tertiary of North America and Europe, many generaof angiosperms are inferred to have crossed the North Atlanticprior to the rifting apart of Canada, Greenland, Iceland, andScandinavia (Tiffney 1985; Manchester 1999). In North Amer-ica, T. salicornioides has not been recognized prior to the earlyOligocene, and it seems to be restricted to the Pacific North-west (Oregon, Washington, and Idaho), where it persisted atleast to the middle Miocene. The species was more widespreadin Europe, ranging from southern France (Saporta 1865) toTranscaucasia (Kolakovskij and Shakryl 1978, pl. 1, figs. 3,4) and from the middle Eocene to the early Pliocene. Both theNorth American and European varieties with mesophyticallyadapted foliage became extinct by the end of the Tertiary, but

the T. brachyodon type persisted in southern Europe, with theclosely similar extant species Tetraclinis articulata persistingtoday in the western Mediterranean.

Many of the genera shared between Europe and NorthAmerica during the early Tertiary are now found to survive inAsia (Tiffney 1985; Manchester 1994). However, Tetraclinis,which is lacking in Asia today and which is unknown in theTertiary floras of eastern Asia, does not conform to this pat-tern. At the time during which Tetraclinis was spreading be-tween Europe and North America, the Turgai seaway effec-tively blocked many plants from crossing between Europe andAsia. Many other plants succeeded in traversing the Turgairegion as the seaway receded in the Oligocene (see Kvacek1994; Tiffney 1994); however, for unknown reasons, Tetra-clinis remained absent from eastern Asia.

Acknowledgments

Specimens were made available by D. Erwin, W. C. Rember,C. J. Smiley, Scott Wing, Dario De Franceschi, and other keep-ers of the herbaria and fossil collections. Helpful commentswere provided by D. H. Mai, E. E. McIver, and H. W. Meyer.Manuscript review comments were kindly provided by JamesEckenwalder and an anonymous reviewer. This research wassupported cooperatively by Czech Ministry of Education grantME 054 to Z. Kvacek and National Science Foundation grantINT 560260112 to S. R. Manchester.

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Tetraclinis Salicornioides -CUPRESSACEAE Int Jour of Plant Sciences 2000

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