Genus Liriodendrites in Cretaceous and Early Paleogene Floras of ...

ISSN 0031-0301, Paleontological Journal, 2009, Vol. 43, No. 10, pp. 1181–1189. © Pleiades Publishing, Ltd., 2009.

Genus Liriodendrites in Cretaceous and Early Paleogene Floras of Northern Asia P. I. Alekseev Komarov Botanical Institute, Russian Academy of Sciences, ul. Professora Popova 2, St. Petersburg, 197376 Russia e-mail: [email protected] Received January 16, 2008

Abstract—Leaves of Liriodendrites Johnson were found in the Gyliakian (Santonian) and Boshnyakovo (Danian) floras of Sakhalin Island, Rarytkin, Koryak, and Kakanaut (Maastrichtian) floras of the Koryak Upland, and Antibes (Coniacian) flora of western Siberia. The study of new finds and revision of earlier collections resulted in the erection of a new species, L. occidentalis P. Alekseev, sp. nov., and creation of two new combinations, L. sachalinensis (Krysht.) P. Alekseev, comb. nov. and L. aeternus (Golovn.) P. Alekseev, comb. nov. The geographical and stratigraphic ranges of Liriodendrites in the Northern Hemisphere were reviewed. Key words: Liriodendrites, Late Cretaceous, northern Asia. DOI: 10.1134/S0031030109100013

INTRODUCTION A leaf lamina divided into two lobes is one of the numerous leaf morphological types of angiosperms. Such a leaf is not very common among angiosperms; however, it appeared as early as the Cenomanian (Liriophyllum Lesq.). Fossil leaves with a bifurcate apex are described as members of several extinct genera (Liriophyllum Lesq., Liriodendrites Johnson, Liriodendropsis Newberry, and Bauhinites Seward) and two modern genera (Bauhinia L. of the Fabaceae and Liriodendron

L. of the Magnoliaceae). The systematic position of the extinct genera is unclear, although magnoliaceous affinity is supposed for Liriophyllum (Dilcher and Crane, 1989). In 2005 and 2007, remains of bilobate leaves were found in the Upper Cretaceous Antibes locality in the Kemerovo Region of western Siberia and were assigned to Liriodendrites. This genus was first described from the Hell Creek Formation (Maastrichtian) in North Dakota of the United States (Johnson,

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Fig. 1. Leaf morphology: (a) Liriodendrites Johnson (after Johnson, 1996); (b) Liriophyllum Lesquereux (after Dicher and Crane, 1994); (c) Bauhinia L. (after Newberry, 1886).

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Fig. 2. Leaf morphology of Liriodendrites sachalinensis (Kryshtofovich) P. Alekseev, comb. nov. (a, b) and Liriodendrites aeternus (Golovneva) P. Alekseev, comb. nov. (c, d): (a) TsNIGR, no. 2069/115; (b) TsNIGR, no. 2069/117; (c) BIN, no. 1200/156; (d) BIN, no. 967A/737. Scale bar 1 cm. PALEONTOLOGICAL JOURNAL

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Fig. 3. Leaf morphology of Liriodendrites occidentalis sp. nov.: (a) BIN, no. 1546/295; (b) BIN, no. 1546/300. Scale bar 1 cm. PALEONTOLOGICAL JOURNAL

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Explanation of Plate1 Figs. 1–2. Leaves Liriodendrites occidentalis sp. nov., western Siberia, Antibes locality, Sym Formation, Coniacian, ×1: (1) BIN, no. 1546/295; (2) BIN, no. 1546/300.

1996). The type species L. bradacii Johnson is characterized by leaves with a truncated or cordate base, a deep notch at the apex, pinnate venation, and an entire margin. The midrib ends in the sinus of the apical notch. Before Liriodendrites was found in the Antibes locality, it was only reported from North America. The revision of various bilobate morphotypes from Late Cretaceous and Paleogene floras of North Asia revealed the presence of this genus in the Gyliakian (Santonian) and Boshnyakovo (Danian) floras of Sakhalin Island and the Rarytkin, Koryak, and Kakanaut (Maastrichtian) floras of the Koryak Upland. These leaf remains were previously ascribed to the genus Liriophyllum (Kryshtofovich, 1937; Krassilov, 1979; Golovneva, 1994). Leaves of Liriophyllum are very similar to leaves of Liriodendrites in leaf lamina outlines and in the type of venation (pinnate and brochidodromous) (Fig. 1), but their midrib dichotomizes slightly before the leaf margin, rather than reaches the sinus of the apical notch (Johnson, 1996). Such a similarity can be an obstacle for correct determination, since hitherto published depictions of Liriophyllum do not allow understanding morphological variability within the genus. Liriophyllum was first described from the Albian–Cenomanian of Colorado in the United States (Lesquereux, 1874). Currently, it includes two species: L. populoides Lesq. and L. kansense Dilcher et Crane (Dilcher and Crane, 1989). The present paper describes finds of Liriodendrites in North Asia and analyses the geographical and stratigraphic ranges of this genus. MATERIAL Leaves of Liriodendrites were first described as Liriophyllum sachalinense Krysht. and Bauhinia cretacea Newberry from Sakhalin Island, on the coast of Tatar Strait, near the Mgachi village (Kryshtofovich, 1918, 1937). Later, Krassilov (1979) reported leaves of Liriophyllum sachalinense from the Sakhalin flora. In addition to the Mgachi locality, Krassilov found such leaf remains on the Avgustovka River, upstream of the Boshnyakovo village. Bassed on the presence of this taxon Krassilov (1979) determined the ages of the Gyliakian and Boshyakovo floras as santonian and Donian, respectively. In his revision of Late Cretaceous floras of the Pacific coast, Vachrameev (1966) assigned Liriophyllum sachalinense to the modern genus Bauhinia and formed the combination B. sachalinensis (Krysht.) Vachr. PALEONTOLOGICAL JOURNAL

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I studied the Sakhalin finds of Liriodendrites from the collection amassed by Kryshtofovich, which is kept at Chernyshev Central Research Geological Museum in St. Petersburg (TsNIGR, no. 2069) and on the basis of images published by Krassilov (1979). One more species of Liriodendrites was described from the Koryak Upland as Liriophyllum aeternum Golovn. These fossil leaves were found in the Gornaya River basin, in deposits of the Rarytkin Formation (Late Maastrichtian–Danian), Kakanaut River basin, in deposits of the Kakanaut Formation (Middle Maastrichtian), and in the Emima River basin, in deposits of the Koryak Formation (Late Maastrichtian) (Golovneva, 1994). Collections nos. 967, 1199, and 1200 are kept at the Komarov Botanical Institute (BIN), in St. Petersburg. Fossil leaves from western Siberia are assigned to the new species Liriodendrites occidentalis P. Alekseev, sp. nov. The Antibes locality is situated near the Antibes station, 10 km west of the town of Mariinsk in the Kemerovo Region. Plant remains come from clays and siltstones in kaolinized sandstones of the Sym Formation, dated to the Coniacian–Maastrichtian (Resolution …, 1990). The Antibes floristic assemblage consists of ferns (Asplenium dicksonianum Heer and Heroleandra sp.), ginkgoaleans (Ginkgo ex. gr. adiantoides (Ung.) Heer), conifers (Sequoia sp.), and angiosperms (Trochodendroides Berry, Nyssidium Heer, Paraprotophyllum Herman, “Platanus” L., Liriodendrites, Menispermites Lesq., Araliaephyllum Font., Cissites Heer, and ëelastrophyllum Goepp.). The most typical angiosperms are members of the genera Trochodendroides and Paraprotophyllum. The currently available information about the taxonomic composition of the flora and stratigraphic position of the enclosing deposits suggests the dating of the Antibes flora to the Early Senonian, most probably, Coniacian (Golovneva, 2005). Collection, no. 1546 is kept at BIN. SYSTEMATIC PALEOBOTANY Genus Liriodendrites Johnson, 1996 Liriodendrites sachalinensis (Kryshtofovich) P. Alekseev, comb. nov.

Liriophyllum sachalinense Krysht.: Kryshtofovich, 1937, p. 272, pl. 10, figs. 4, 5; , Krassilov 1979, p. 118, pl. 46, figs. 3–5, pl. 47, figs. 1–3. Bauhinia sachalinensis (Krysht.) Vachr.: Vachrameev, 1966, p. 81, non rite publ. Bauhinia cretacea auct. non Newberry: Kryshtofovich, 1918, p. 53; Kryshtofovich, 1937, p. 275, text-fig. 7.

L e c t o t y p e (designated here). TsNIGR, no. 2069/115; leaf, Sakhalin Island, Mgachi; Arkovo Formation, Santonian; Fig. 2a.

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Explanation of Plate2 Figs. 1–4. Leaves of Liriodendrites occidentalis sp. nov., western Siberia, Antibes locality, Sym Formation, Coniacian, ×1: (1) BIN, no. 1546/243; (2) BIN, no. 1546/303; (3) BIN, no. 1546/251; (4) BIN, no. 1546/305.

D i a g n o s i s. Leaves 7–9 cm long and 8–9 cm wide. Notch between lobes about 1/4–1/3 of leaf length. Leaf base cordate, and leaf margin entire. Secondary veins in five or six pairs. D e s c r i p t i o n (Figs. 2a, 2b). The leaves are simple, round or ovate, 7–9 cm long and 8–9 cm wide, with a cordate base, a cuneate, or, more rarely, amphorashaped apical notch, reaching 1/4–1/3 of the leaf lamina length. The leaf is entire-margined. The venation is pinnate and brochidodromous. The midrib reaches the apical notch. There are five or six pairs of lateral veins, which are connivent at the leaf base and are arranged in an subopposite manner. The angle of their deviation is 90° at the leaf base, decreasing up to 40°–45° toward the leaf apex. Secondary veins fork in the middle and distal area, forming broken loops. Large loops are in turn connected by a series of smaller loops. Thin

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branching anastomoses between the secondary veins form tertiary venation. Venation of higher orders has not been preserved. C o m p a r i s o n. The type species L. bradacii has a bilobate leaf 8–11 cm long and 9–10 cm wide, with a deep notch between the lobes, which varies from 1/3 to 3/5 of the leaf length, and three to six pairs of secondary veins. Often, the leaf margin is undulate; the base is truncated or slightly cordate. L. sachalinensis differs from the type species by a greater number of secondary veins, entire-margined leaf laminas, smaller notch between lobes, and rounded outlines of the leaf. R e m a r k s. One specimen of Liriodendrites from Sakhalin Island was identified by Kryshtofovich (1918) as Bauhinia cretacea. Later, Vachrameev (1966) transferred Liriophyllum sachalinensis into the genus Bau-

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Fig. 4. Late Cretaceous occurrence of Liriodendrites in the Northern Hemisphere.

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Fig. 5. Geographical range of: (1) North Dakota, Hell Creek Formation (Maastrichtian); (2) Sakhalin Island, Arkovo Formation (Santonian) and Boshnyakovo Formation (Danian); (3) Koryak Upland Rarytkin, Kakanaut and Koryak formations (Maastrichtian– Danian); (4) Western Siberia, Antibes locality, Sym Formation (Coniacian). PALEONTOLOGICAL JOURNAL

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hinia. However, this combination is invalid, since no reference to the basionym was provided. The modern Bauhinia has a bilobate leaf of two fused pinnate leaflets (Owens, 2000). Several significant differences from Liriodendrites and Bauhinia exist in their venation (Fig. 1). O c c u r r e n c e. Sakhalin Island, coast of the Tatar Strait near the village of Mgachi, Arkovo Formation, Santonian; Avgustovka River, Boshnyakovo Formation, Danian. M a t e r i a l. TsNIGR, no. 2069/115–2069/117. Liriodendrites aeternus (Golovneva) P. Alekseev, comb. nov.

Liriophyllum aeternum Golovn.: Golovneva, 1994, p. 108, pl. 7, figs. 1, 6, pl. 72, fig. 5.

H o l o t y p e. BIN, no. 1200/156, Koryak Upland, Kakanaut River, Kakanaut Formation, Maastrichtian (Golovneva, 1994, p. 108, pl. 7, fig. 1); Fig. 2c. D i a g n o s i s. Leaves 11–20 cm long and 12–19 cm wide. Leaf base cordate, and leaf margin entire. Notch between lobes about 1/3–1/2 leaf length. Secondary veins in seven or eight pairs. D e s c r i p t i o n (Figs. 2c, 2d). Leaves are simple; the leaf lamina is bilobate, irregularly oval or round, 11–20 cm long and 12–18 cm wide. The leaf is slightly longer than wide, as long as wide in some specimens, and even slightly wider than long in others. The leaf base is cordate. The apex is rounded and divided into two lobes in its center. The notch between the lobes is amphora-shaped, with a rounded lower extremity, 1/4– 1/3 of the leaf length, 2–4 cm deep and 1 cm wide. The outer sides of the lobes are convex and rounded. The leaf margin is entire. The venation is pinnate. The midrib is thick and distinct up to the vertex of the notch. There are seven or eight pairs of secondary veins, which deviate from the midrib at a nearly right angle; the angle of deviation diminishes toward the apex. Basal veins are directed downward and innerve lobes of the base. Veins of the lower pair have several basiscopic deviations. Usually, veins fork two or three times starting in the middle or in the upper third of the leaf and form large broken loops. Several rows of smaller broken loops deviate from the larger loops toward the leaf margin. The tertiary venation is formed by thin and branching anastomoses. Veins of the forth order form an irregular polygonal net. C o m p a r i s o n. The species differs from L. bradacii in the larger leaves, more numerous secondary veins (seven or eight in the species under description instead of three to six in L. bradacii), non-undulate margin of the leaf lamina, smaller notch between the lobes, and the distinctly cordate base. This species differs from L. sachalinensis in the larger leaves, more numerous secondary veins, and in the deeper notch in the leaf apex. The apical notch is most often amphorashaped, whereas in L. sachalinensis it is most often cuneate or triangular.

O c c u r r e n c e. Koryak Upland, Rarytkin Formation (middle subformation), Koryak Formation, and Kakanaut Formation of the Maastrichtian. M a t e r i a l. BIN, nos. 967A/734, 967A/736, 967A/737, 1199/55a, 1199/153, 1200/153, 1200/154, 1200/156, 1200/157, 1200/208, 1200/345, and 1200/347. Liriodendrites occidentalis P. Alekseev, sp. nov. Plate 1, figs. 1, 2; Plate 2, figs. 1–3.

H o l o t y p e. BIN, no. 1546/295; leaf, western Siberia, Antibes locality; Sym Formation, Coniacian (Pl. 1, fig. 1). D i a g n o s i s. Leaves 6–15 cm long and 5–16 cm wide. Usually, leaf base deeply cordate, and leaf margin entire. Notch between lobes 2/5–1/2 leaf length. Secondary veins in five or six pairs. D e s c r i p t i o n (Figs. 3a, 3b). Leaves are simple, round, ovate, or transversely widely-oval, divided into two lobes in the upper part, 6–15 cm long and 5–16 cm wide. The base is cordate. The leaf margin is entire. A fragmentary petiole about 2 cm long is preserved in some specimens. The notch between the lobes is usually amphora-shaped, with a rounded apex. The lobes are widened in their upper parts and gradually become rounded toward the leaf apex. More rarely, the notch is rounded-cuneate. In large leaves, the depth of the notch reaches 1/2 of the leaf length, becoming butterflyshaped at the expense of a short midrib and deeply cordate base. In small leaves, the relative depth of the notch between the lobes is usually smaller. The venation is pinnate and brochidodromous. The midrib is relatively thick, reaching the apical notch. There are five or six pairs of secondary veins. They are subopposite or, more rarely, alternate in the upper part of the leaf. Occasionally, intercalary veins are present. At the leaf base, secondary veins are connivent; usually, the veins of the lower pair are thin and deviate downwards, innerving basal lobes with two or three basiscopic deviations. The secondary veins fork once or twice in the proximal or distal part. Two upper veins innerve the leaf lobes. The second pair runs more or less parallel to the notch margin. Near margin, the secondary veins and their deviations are looping in series of rounded or slightly broken loops. Tertiary venation is represented by thin and branching anastomoses; the areas between them are filled with an irregular polygonal net. C o m p a r i s o n. The species differs from L. bradacii in the more rounded outline of the leaf lamina, number of secondary veins, shorter apical notch, entire margin of the leaf, and in the distinct cordate leaf base. L. occidentalis differs from L. sachalinensis in the larger leaves with more numerous secondary veins and in the deeper apical notch, which is nearly always amphora-shaped. The apical lobes and distinct lobes of the cordate base give the leaf of L. occidentalis a nearly butterfly-like shape, which differentiates this species from L. sachalinensis with its rounded outlines.

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L. occidentalis differs from L. aeternus in the smaller leaves, less numerous secondary veins, and in the relatively deeper apical notch.

REFERENCES 1. D. Dilcher and P. Crane, “Archaeantus: An Early Angiosperm from the Cenomanian of the Western Interior of North America,” Ann. Mis. Bot. Gard. 71 (2), 351–384 (1984).

M a t e r i a l. BIN, collection no. 1546, specimen nos. 243–245, 249, 251, 293–297, 300, 301, 303, 305, and 306.

2. L. B. Golovneva, “Maastrichtian–Danian Floras of the Koryak Mountains,” Tr. Bot. Inst. Ross. Akad. Nauk, No. 13, 1–147 (1994).

GEOGRAPHICAL AND STRATIGRAPHIC RANGE

3. L. B. Golovneva, “Phytostratigraphy and Evolution of the Albian–Campanian Flora within Siberia,” in Cretaceous System of Russia: Problems of Stratigraphy and Paleogeography. Collection of Papers of The Second All-Russia Conference (S.-Peterb. Gos. Univ., St. Petersburg, 2005), pp. 177–197 [in Russian].

To date, four species of Liriodendrites have been found in Cretaceous floras of the Northern Hemisphere: one, in North America; and three, in Eurasia (Figs. 4, 5). In North America, L. bradacii is only known from the Maastrichtian Hell Creek Formation in North Dakota, the United States (Johnson, 1996). In Eurasia, Liriodendrites is known from Sakhalin Island (L. sachalinensis), Koryak Upland (L. aeternus), and western Siberia (L. aeternus). These localities are restricted to northern Asia; the genus is unknown in Europe. Such a distribution testifies to the existence of floristic relations between North America and North Asia via the Beringia Bridge during the Late Cretaceous.

4. K. R. Johnson, “Description of Seven Common Fossil Leaf Species from the Hell Creek Formation (Upper Cretaceous: Upper Maastrichtian), North Dakota, South Dakota, and Montana,” Proc. Denver Mus. Nat. Hist. Ser. 3, No. 12, 1–47 (1996). 5. V. A. Krassilov, Cretaceous Flora of Sakhalin (Nauka, Moscow, 1979) [in Russian]. 6. A. N. Kryshtofovich, “On the Cretaceous Flora of Russian Sakhalin,” J. Coll. Sci. Imp. Univ. Tokyo 40 (Art. 8), 1–73 (1918).

Such morphological characters of Liriodendrites as an entire leaf margin and bilobate apex can indicate that the taxon was thermophilic (Wolfe, 1993), although its leaf laminas are thin and non-leathery, a characteristic feature of deciduous forms. Species of the genus Liriodendrites are mostly restricted to the south of SiberianCanadian paleogeographic area, with the exception of L. aeternus, known from the Koryak Upland. Remains of Liriodendrites are known from the Late Cretaceous since the Coniacian until Maastrichtian and from the Early Paleocene. The oldest records are known from the Coniacian of western Siberia, which is the most western locality among the known localities. The youngest (Danian) records are known from Sakhalin Island. The maximal specific diversity of Liriodendrites and the most common occurrence of its species occurred in the Maastrichtian (Fig. 4). Three species are known from that time, occurring in North Dakota, Sakhalin Island, and Koryak Upland. So far available information is insufficient to judge about the origin of the genus, its diversification, and further geographical distribution of its members, since new finds are probable, which could contribute to more complete and correct understanding of the evolution of this taxon. Liriodendrites was common in the Northern Hemisphere during most of the Late Cretaceous, although its members were not among dominants of Late Cretaceous floras. PALEONTOLOGICAL JOURNAL

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7. A. N. Kryshtofovich, “Cretaceous Flora of Sakhalin. Mgach and Polovinka,” Tr. Dal’nevost. Filiala Akad. Nauk SSSR, Ser. Geol. 2, 1–103 (1937). 8. L. Lesquereux, “Contrbution to the Fossil Flora of the Western Territories. Part I. Cretaceous Flora,” U. S. Geol. Geograph. Surv. Territories, Report 6, 1–136 (1874). 9. J. S. Newberry, “Description of a Species of Bauginia from the Cretaceous Clays of New Jersey,” Bull. Torrey Bot. C., 20 (1), 77–78 (1889). 10. S. Owens, “Secondary and Tertiary Pulvini in the Unifoliate Leaf of Cercis canadensis L. (Fabaceae) with Comparison to Bauhinia purpurea L.,” Int. J. Plant Sci. 161 (4), 583–597 (2000). 11. Resolutions of the Fifth Interdepartmental Conference on the Stratigraphy of the Mesozoic Deposits of the West Siberian Plain (Tyumen’, May 14–18, 1990) (ZapSibNIGNI, Tyumen’, 1990) [in Russian]. 12. V. A. Vachrameev, “Late Cretaceous Floras of the Pacific Coast of the USSR, Distinctive Features of Their Composition and Stratigraphic Position,” Izv. Akad. Nauk SSSR, Ser. Geol., No. 3, 76–87 (1966). 13. J. A. Wolfe, “A Method of Obtaining Climatic Parameters from Leaf Assemblages,” U. S. Geol. Surv. Bull. 2040, 1–73 (1993).

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