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*Corresponding author (email: lssjjh@mail.sysu.edu.cn)

• RESEARCH PAPER • May 2012 Vol.55 No.5: 728–732

doi: 10.1007/s11430-012-4395-2

First record of extinct fruit genus Chaneya in low-latitude tropic of South China

FENG XinXin & JIN JianHua*

State Key Laboratory of Biocontrol, Guangdong Key Laboratory of Plant Resources and School of Life Sciences, Sun Yat-sen University, Guangzhou 510275, China

Received September 27, 2011; accepted February 28, 2012; published online March 23, 2012

Fossil reproductive structure from the Eocene of the Changchang Basin (Hainan Island, South China) is recognized as Chaneya hainanensis sp. nov. This new species is characterized by persistent corolla of five obovate petals with three subparallel pri-mary venation linked by arching secondary veins, circular central disk bearing two orbicular ovaries or fruit bodies. This dis-covery confirms the presence of the extinct fruit genus Chaneya in low-latitude tropical area, providing significant fossil evi-dence for investigating the origin, migration, and phytogeography of this genus and discussing the Tertiary floristic exchanges among North America, eastern Asia, and Europe. Considering the distribution of this genus and its extant relatives and the climate changes during the Cenozoic, we hypothesize that Chaneya was a widespread tropical or subtropical taxon, but, with climate cooling, became extinct in northern latitudes and evolved into Picrasma (Simaroubaceae) and Rutaceae mainly in modern tropics and subtropics.

Chaneya, Eocene, low-latitude tropic, Changchang Basin, South China

Citation: Feng X X, Jin J H. First record of extinct fruit genus Chaneya in low-latitude tropic of South China. Sci China Earth Sci, 2012, 55: 728–732, doi: 10.1007/s11430-012-4395-2

The extinct fruit generic name Chaneya was established by Wang and Manchester [1] to accommodate wind-dispersed fossil fruits consisting of an accrescent hypogynous calyx of five obovate sepals and one or more globose fruit bodies. This kind of reproductive structure is well represented in the Tertiary fossil records of the Northern Hemisphere and was particularly widespread in the Eocene of North America [2–4]. Its precise taxonomic position, however, had been the subject of debate over the years. Heer [3] assigned speci-mens from the Tertiary of Europe to Porana (Convolvu-laceae) that is distributed in tropical and subtropical areas of eastern Asia. Weyland [5] transferred similar European fos-sils from Porana to Monotes (Dipterocarpaceae), which is found on the tropical island of Madagascar, off the east

coast of Africa. MacGinitie [6] moved taxonomically the North American fossils from Porana to Astronium (Anacar-diaceae), which is another genus confined to central and South America with grossly similar modern fruits. All of these assignments, however, are based mainly on morpho-logical features with rare examination of anatomical traits and gynoecium characters. After examining the cuticle de-tails of excellently preserved specimens from the Miocene flora of Shanwang, China, and gynoecium features of specimens from North America, Wang and Manchester [1] argued this type of fossil fruit is similar but not identical to any extant genus mentioned above. Existing in several ex-tant families, this reproductive structure may be viewed as having convergent evolutionary features. Therefore, a new genus, Chaneya, is proposed for these fossil fruits. Accord-ing to the sepal size and stratigraphic position, specimens from the Eocene of North America and Miocene of eastern

Feng X X, et al. Sci China Earth Sci May (2012) Vol.55 No.5 729

Asia were recognized as Chaneya tenuis (Lesquereux) Wang et Manchester and Chaneya kokangensis (Endo) Wang et Manchester respectively. After comparisons with abundant modern plants, Wang and Manchester [1] pro-posed Picrasma (Simaroubaceae), a genus distributed from the Western Himalayas to Japan, Malaysia, and Fiji, as an extant relative.

Teodoridis and Kvaček [7] reexamined Heer’s original materials from the Miocene of Öhningen, Germany, and other materials from the Most Basin (Czech Republic) as Chaneya oeningensis (Unger) Teodoridis et Kvaček ac-cording to their morphological and cuticle traits. They in-terpreted the five-lobed structure as persistent corolla, rather than calyx on the basis of their observation of what ap-peared to be sepal remnants below the enlarged whorl in specimens of Chaneya and the long persistent corolla and caduceus calyx in the apocarpous gynoecium of extant Pic-rasma, and then emended the diagnosis of Chaneya. They considered the dark spots on the persistent corolla to be glandular cavities with the remains of smaller resinous bo- dies and consequently proposed Rutaceae as another possi-ble affinity. Manchester and Zastawniak [8] reassigned other similar specimens from the upper Miocene of Sośnica (Poland), as Chaneya membranosa (Goepp) Manchester et Zastawniak, extending this genus into the late Miocene of central Europe.

All previously illustrated populations are from modern middle-latitude temperate areas of the North Hemisphere. In this article, we introduced a new species from the low-latitude tropic of South China, and propose a new hypothesis to ad-dress the origin and migration of this genus.

1 Material and methods

The Changchang Basin (19°38′03″N, 110°27′04″E, Figure 1) is located near Jiazi Town, Qiongshan County, in the north-ern portion of Hainan Island, South China. The Changchang Formation is well developed in this basin and the unique specimen (CCF018) under study was collected from the coal-bearing series of this formation. Although not radioi-sotopically dated, the Changchang Formation has been con-sidered early Eocene to early late Eocene in age based on the palynological assemblage [10]. Associated plant fossils previously collected from this formation include ferns (Os-munda and Salvinia), gymnosperm (Nageia), and abundant angiosperms (Cinnamomum, Alseodaphne, Nelumbo, Liqui- dambar, Castanea, Lithocarpus, Quercus, Myrica, Juglans, Palaeocarya, Paraphyllanthoxylon, Acer, Sabalites, and Musophyllum) [11].

The specimen is preserved only as impression but the diagnostic venation details of perianth and gynoecium traits are excellently revealed. Perianth margins not exposed in the initial fracture were exposed by chipping away addi-tional sediments with needles while examined with dissect-ing microscope. Macroscopic images were photographed with Sony DSC-TX55 digital camera and microscopic im-ages showing details of perianth venation were obtained by Leica S8ap0 and relevant photography program.

In this article, terms used in describing perianth follow the standard terminology for architectural description of dicotyledonous leaves [12, 13]. Morphological comparative work with European, North American, and Asian specimens is based on refs. [1, 7, 8].

Figure 1 Location of the Changchang Basin on Hainan Island, China [9].

730 Feng X X, et al. Sci China Earth Sci May (2012) Vol.55 No.5

2 Taxonomical description

Order: Sapindales Family: Simaroubaceae DC. vel Rutaceae Juss. Genus: Chaneya Wang et Manchester

Species: Chaneya hainanensis Feng et Jin, sp. nov.

Holotype. Fruit part specimen (CCF-018a) (Figure 2(a)).

Paratype. Fruit counterpart specimen (CCF-018b) (Figure 2(b)).

Horizon. Changchang Formation, Eocene. Locality. Changchang Basin, Hainan Island, South

China. Repository. Biological Museum of Sun Yat-sen Uni-

versity, Guangzhou, China. Derivation of specific epithet. The specific name is

derived from the fossil site’s name––Hainan. Diagnosis. Persistent corolla pentamerous, actinomor-

phic. Petals entirely margined, obovate; the bases widely cuneate, adnate; the apices rounded. Petal venation consist-ing of three primary longitudinal subparallel veins, craspedodromous to camptodromous. Central disk circular, bearing two orbicular ovaries or fruit bodies.

Description. Persistent corolla is five-lobed, actino-morphic, ca. 21 mm in diameter (Figure 2(a)). Petals are entirely margined, obovate, subequal in size (average 9.5 mm long and 3.1 mm wide); petal bases are widely cuneate and adnate with each other, surrounding the central disk; the apices are rounded; sinuses between petals are acute to right, smooth (Figure 2(b)). Venation of petals consists of three primary longitudinal subparallel veins; midvein is slightly stronger and extends to the apex; the lateral veins appear

weaker and camptodromous; all three main veins originate independently from the petal base (Figure 2(c)). Secondary veins arise from the longitudinal primary veins at acute an-gles, commonly meeting those from adjacent longitudinal veins to form distally arching cross veins (Figure 2(d)). Central disk is circular, bearing two clear orbicular ovaries or fruit bodies (Figure 2(e), 2(f)). Orbicular dots––resin bodies or glands––are not observed on the surface of the perianth.

3 Comparative morphology

Although cuticle details are not available due to thin texture of the persistent perianth, morphological features including petal shape and size, venation structure, and gynoecium characteristics confirm its affinity to Chaneya. The Eocene Hainan fruit is compared with the four previously illustrated Chaneya members in morphological features, stratigraphic and geographic position (Table 1).

Teodoridis and Kvaček [7] graphed the ranges in petal length and width of the Chaneya members, utilizing the perianth dimension to differentiate them. In comparison, petals of C. kokangensis (5–10 mm) and C. membranosa (6–14 mm, mean 10.6 mm) are remarkably wider than that of the Hainan specimen (3.1 mm) (Table 1). While dimen-sion of the Hainan specimen falls within the size ranges of C. oeningensis, its narrowly obovate petals differ dramati-cally from the broadly elliptical petals of the latter [7, Plates I and II]. The Eocene Hainan fruit resembles C. tenuis mostly in petal size, shape, and the three subparallel longi-tudinal venations. On the contrary, a remarkable feature of the Hainan Eocene fruit is that petal bases are adnate with

Figure 2 Chaneya hainanensis Feng et Jin, sp. nov. from the Changchang Basin, Hainan Island, South China (CCF-018). (a) Fruit with persistent five-lobed perianths, CCF-018a; (b) counterpart of the same specimen, CCF-018b; (c) enlargement of petal lobe showing three primary longitudinal subpar-allel veins, CCF-018b; (d) drawing of (c) showing the venation details; (e) enlargement of (a) showing the circular central disk (arrows); (f) enlargement of (b) showing the impressions of two orbicular ovaries or fruit bodies (arrows). Scale bars: 5 mm for (a) and (b), 2 mm for (c), 4 mm for (d), 1 mm for (e) and (f).

Feng X X, et al. Sci China Earth Sci May (2012) Vol.55 No.5 731

Table 1 Comparison of Chaneya species

Species Perianth diameter

(mm) Petal width (mm)

Petal length (mm)

Number of main veins

Gynoecium features Stratigraphic and geo-

graphic position Source

C. tenuis 22–34.5

(mean 27) 2.5–6.5

(mean 5.3) 11–16

(mean 13) 3–5

Two whorls of five carpels; one or two fruit bodies enlarged at

maturity

Eocene of North America and northeastern China

[1]

C. kokangensis 28–40

(mean 36.3) 5–10 12–21 5

Ovaries in two whorls of five; each carpel with one style; at

least one ellipsoidal to globose fruit body enlarged

Miocene of eastern Asia [1]

C. oeningensis ? 2.3–7.1

(mean 4.8) 5.3–11.7

(mean 9.6) 5

Five carpels in one whorl alter-nating with petals; single or two

fruitlets fully mature

Miocene of Germany and Czech Republic

[7]

C. membranosa 25 6–14

(mean 10.6) 8–21

(mean 15.1) 5

Central disk circular to pentago-nal with bearing five distinct

orbicular ovaries or fruit bodies Upper Miocene of Poland [8]

Eocene Hainan fruit

21 3.1 9.5 3 Central disk circular, bearing two enlarged ovaries or fruit

bodies Eocene of South China This paper

each other, surrounding the central disk and sinuses be-tween petals are almost right and smooth (Figure 2(a), (b)), in contrast to C. tenuis, in which sinuses are acute and deeply incised [1]. Therefore, we establish a new species, Chaneya hainanensis sp. nov.

4 Phytogeographic and paleoclimatic implica-tion

Teodoridis and Kvaček [7] drew a map showing Chaneya’s stratigraphic and geologic distribution and proposed its origin and migration route: (1) having originated in the middle Eocene of North America, C. tenuis dispersed across Beringia to eastern Asia during the Eocene, forming this species circum-Pacific distribution; (2) after arriving in eastern Asia, C. tenuis, on the one hand, evolved into an independent eastern Asia species C. kokangensis during the Neogene and alternatively, spread westwards to Kazakhstan in the late Paleogene; (3) then the genus migrated to Europe via the Turgaj migration route during the Oligocene; (4) in the subsequent Miocene, Chaneya extended across Near East towards Kazakhstan.

Picrasma (Simaroubaceae) is distributed from the West-ern Himalayas to Japan, Malaysia, and Fiji [1], and another relative proposed by Teodoridis and Kvaček [7], Rutaceae is also principally tropical and subtropical taxon. Chaneya populations, however, are discovered mainly from modern temperate middle latitude-areas of the world [7, Figure 4].

Given the similarity in environmental requirement of the fossils and their contemporary counterparts and the climate change during the Cenozoic, we hypothesize that Chaneya might be a widespread tropical to subtropical taxon during climatically warm intervals of the Eocene of North America and eastern Asia. With the dramatic climate cooling at the Eocene-Oligocene boundary, C. tenuis went extinct in North America, but Chaneya in eastern Asia survived and possibly evolved into the Miocene C. kokangensis and al-

ternatively, spread westwards through Kazakhstan to Eu-rope, being flourished in the warm early and middle Mio-cene. Thereafter, all of Chaneya populations might have become extinct in temperate zones of the Northern Hemi-sphere because of the climatic cooling after the middle Mi-ocene and evolved into Picrasma (Simaroubaceae) and Ru-taceae mainly in extant tropics and subtropics.

Chaneya was recovered from the Dalianhe coal mines, Yilan Country, northeastern China with an early to late Eo-cene age [14]. This record is earlier than the middle to late Eocene occurrences in western North America and therefore, Chaneya’s dispersal direction across Beringia is uncertain, depending on new Tertiary records in high latitudes of Alaska or northeastern Russia. The discovery of C. hai-nanensis confirms the existence of Chaneya in Eocene low-latitude tropic of South China. Since the Changchang Formation is not later in geologic age than the North Amer-ican fossil localities, we assume that eastern Asia might be the area of origin of Chaneya.

This study was supported by National Natural Science Foundation of Chi-na (Grant Nos. 40972011, 31070200), National Basic Research Program of China (973 Program) (Grant No. 2012CB822003), the joint Project of National Natural Science Foundation of China and Russian Foundation for Basic Research (Grant Nos. 41111120083, 11-04-91175), Guangdong Natural Science Foundation (Grant No. 10151027501000020), and Key Project of the Sun Yat-sen University for inviting foreign teachers and Scientific Research Fund, Hongda Zhang, Sun Yat-sen University. We thank Mr. Wang Zhao of the Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, for his collaboration in the fieldwork on Hainan Island. We also thank Shan Xueqi, School of Life Sciences, Sun Yet-sen University for drawing the perianth venation and Ms. Margaret Joyner, University of Florida, for editing the manuscript.

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