Taxonomy and morphological diversity of infructescences Jenkinsella co-occurred with Trochodendroides leaves in the Cretaceous and Paleogene Текст научной статьи по специальности «Биологические науки»

yM 561.5:551.763:551.781

naneo6omaHUKa. 2017. T. 8. C. 92—121

TAXONOMY AND MORPHOLOGICAL DIVERSITY OF INFRUCTESCENCES JENKINSELLA CO-OCCURRED WITH TROCHODENDROIDES LEAVES IN THE CRETACEOUS AND PALEOGENE

L. B. Golovneva, P. I. Alekseev

Komarov Botanical institute RAS, St. Petersburg, Lina_Golovneva@mail.ru

On the basis of new records and reexamination of described fossils a revision of morphology and sys-tematics of fructifications, found in co-occurrence with Trochodendroides Berry leaves was undertaken. The general construction of racemose infructescences and fruits of all known specimens is practically identical. This similarity indicates that these plants were closely related with minor differences that are not sufficient for separate generic designation. We suggest applying the name Jenkinsella Reid et Chandler for dispersed follicular fruits, to fruits in racemes and to infructescences attached to the shoots. This is the earliest appropriate generic name designated for fruits with distinguishable morphology and critical details of inner structures. The diagnosis of the genus Jenkinsella is emended and five new species are described: Jenkinsella krassilovii Golovneva et P. Alekseev, sp. nov., J. knowltonii Golovneva et P. Alekseev, sp. nov., J. conferta P. Alekseev et Golovneva, sp. nov., J. makulbekovii Golovneva et P. Alekseev, sp. nov., J. vilyuensis Golovneva et P. Alekseev, sp. nov. Three new combinations (J. filatovii (Samylina) Golovneva et P. Alekseev, comb. nov., J. jiayinensis (G.P. Feng, C.S. Li, Zhilin, Y.F. Wang et Gabrielyan) Golovneva et P. Alekseev, comb. nov., J. gardnerii (Chandler) Golovneva et P. Alekseev, comb. nov.) are created. Investigation of infructes-cence arrangement in different species of Jenkinsella provides new data, allowing reinterpretation of fertile shoots construction in Joffrea speirsii.

Keywords: Jenkinsella, Nyssidium, Trochodendroides, Cercidiphyllaceae, Cretaceous, Paleogene.

INTRODUCTION

Ovate or elliptical fossil leaves with cuneate to cordate base, crenate or serrate margin, palmate brochi-dodromous venation and long petioles were widespread in the Cretaceous and Paleogene deposits of Northern Hemisphere. Although these leaves have been described since the nineteenth century, their systematic relationships retained for a long time problematic, and they have been assigned to a wide variety of extinct and extant genera: Cocculus, Cercidiphyllum, Trochodendroides, Ziziphus, Macclintockia, Populus (Brown, 1939; Wolfe, 1966; Iljinskaja, 1974b, c; Hickey, 1977; Tanai, 1981). Now they are usually assigned to the genus Trochodendroides (Berry, 1926; Crane, 1984, 1989; Golovneva, Alekseev, 2010). The type species, T. rhomboidea Berry, was described from the Cenomanian of the Dakota Formation, USA (Berry, 1926). The earliest occurrences of this genus are known from the early-middle Albian in North America and Northeastern Asia (Golovneva, Alekseev, 2010). The greatest morphological and systematic diversity of the genus Trochodendroides is observed in the Turonian-Coniacian and Paleocene-Eocene. This genus was a common component of the Late Cretaceous and Paleogene floras from middle and high latitudes (Berry, 1935; Bell, 1949; Kryshtofovich, 1958; Kryshtofovich, Baikovskaya, 1966, Chandrasekharam, 1974; Iljinskaja, 1974c; Hickey, 1977; Tanai, 1981; Budantsev, 1983; Crane, 1984; Golovneva, 1994; Budantsev, Golovneva, 2009; Golovneva, Alekseev, 2010; Manchester, 2014; Yudova, Golovneva, 2014). Investigation of their cuticular features also reveals the similarity with those of living genus Cercidiphyllum from monotypic family Cercidiphyllaceae (Golovneva, Alekseev, 2010).

The genus Alasia was established for associated staminate inflorescences (Golovneva, 2006a). This genus includes three species from the Cretaceous and Paleogene of Siberia and North America. Pollen from one specimen was studied by Krassilov and Kodrul (2008). Pollen grains are small tricolpate with long colpi and a variably microreticulate to verrucate-scabrate ornamentation.

Fossil fruits that co-occurred with Trochodendroides leaves have been known for a long time, but early discoveries were considered as belonging to other genera and families. These distinctive follicular fruits with subparallel longitudinal ridges and transverse striations were first detected by O. Heer (1869, p. 477, pl. 43, fig. 12c, pl. 50, fig. 5, 6, 7) from the Paleocene deposits of Atanekerdluk in West Greenland, and then

named as Nyssa arctica Heer. This author described and figured several single detached elongated fruits, 19—21 mm in length and 9—11 mm in diameter, with short stalk, probable dorsal groove, longitudinal ridges and thin transverse striae, that really were only superficially similar with fruits of modern Nyssa (pl. I, fig. 12, 13). Although subsequently this species was used as basionym for several generic combinations, the original specimens from Greenland were never reexamined or refigured. Fruits of Carpolithus follicularis Heer, also described from Atanekerdluk (Heer, 1869), are probably conspecific with "Nyssa" arctica, but their preservation is worse and distinctive characters are not clear. They are smaller and have no stalk.

Later such fruits were assigned to a wide range of extinct and extant genera: Nyssidium (Heer, 1870; Schmalhausen, 1890; Hollick, 1936; Iljinskaya, 1974a; Crane, 1984), Leguminosites (Lesquereux, 1873, 1878), Berrya (Knowlton, 1930; non Berrya Roxb. 1820),Jenkinsella (Reid, Chandler, 1933), Trochodendro-carpus (Kryshtofovich, 1958), Kenella (Samylina, 1976), Joffrea (Crane, Stockey, 1986). Some authors continued to use the name Nyssa (for example, N. (?) racemosa Knowlton (1898) and N. rostrata A. Pojarkova (1939)). Most of these names are invalid or inappropriate as junior homonyms or synonyms.

The first discoveries of such fruits from North America were described as Carpolithes arachioides Lesquereux, Leguminosites arachioides (Lesquereux) Lesquereux and L. borealis Dawson (Lesquereux, 1873, 1878; Dawson, 1889; Penhallow, 1908; Berry, 1935), and were suggested to have a similarity with leguminous plants. Specimens, described by L. Lesquereux (1873, 1878) and afterwards by D. Penhallow (1908), were fruits attached to the axis (in raceme). However generic name Leguminosites is inappropriate, because this formal genus was erected for another kind of fruits and seeds of fossil Fabaceae from the London Clay (Bowerbank, 1840).

F. H. Knowlton (1930) proposed the name Berrya racemosa (Knowlton) Knowlton for fruits in a raceme from the Paleocene deposits of Colorado, USA. Two of the most complete specimens (Knowlton, 1930, pl. 41, fig. 4, 5) comprised shoots with infructescences. Unfortunately the name Berrya can not be used for this type of fructification, because earlier this name was established for another plant from family Malvaceae.

Pyritized dispersed fruits and locule casts from the early Eocene London Clay Formation were referred to the genus Jenkinsella. Reid and Chandler (1933) suggested a taxonomic position of J. apocynoides Reid et Chandler within the families Apocynaceae or Asclepiadaceae. Thus the systematic relationships of these early records remained obscure.

R. W. Brown (1939) first noted the co-occurrence of these follicular striate fruits with leaves and winged seeds resembling those of extant Cercidiphyllum at the several Paleocene and Eocene sites in North America. Brown assigned all of these remains to single species Cercidiphyllum arcticum (Heer) R. W. Brown, although he indicated, that these infructescences differ from infructescences of modern Cercidiphyllum by their racemose organization and some other characters. Subsequent investigations established numerous differences between the fossil fruits and those of living Cercidiphyllum (Chandler, 1961; Krassilov, 1976, and see later references by Krassilov; Hickey, 1977; Tanai, 1981), but Brown's work had great significance for understanding of nature and systematic relationship of these fossil plants. Some fossils from the Paleocene of Canada were described as Cercidiphyllum fruits in subsequent years (Chandrasekharam, 1974; Basinger, Dilcher, 1983).

W. A. Bell (1949), in his review of uppermost Cretaceous and Paleogene floras of western Alberta, Canada, proposed to unite fruits associated with Trochodendroides leaves under the name Jenkinsella arctica (Heer) Bell. But this binominal was not adopted by other paleobotanists.

Some authors preferred to use the general formal name Carpolithes for this kind of infructescences. M. E. J. Chandler (1961) described fruiting structures attached to the shoot from the British early Tertiary as Carpolithes gardneri Chandler. According to her, the fruits (follicles) were arranged in raceme, singly or sometimes in pairs. L. J. Hickey (1977) also used the name Carpolithes for single fruits and racemose infructescences, creating the combination C. arcticus (Heer) Hickey for specimens from Greenland, Spitsbergen, England and North America. Isolated follicles from the Oligocene of Japan have been referred to Carpites japonicus (Endo) Tanai (1970) and follicles from the Paleogene of Japan to Carpolithes arcticus (Tanai, 1981).

A. N. Kryshtofovich (Kryshtofovich, 1958; Kryshtofovich, Baikovskaya, 1966) established a new genus Trochodendrocarpus for this kind of follicular fruit with Nyssa arctica as its type species. He included in synonymy of the name Trochodendrocarpus arcticus (Heer) Kryshtofovich the species Nyssa rostrata Pojarkova, Jenkinsella arctica (Heer) Bell, Nyssidium ekmanii Heer, N. geminatum Schmalhausen, Leguminosites arachioides Lesquereux, Berrya racemosa (Knowlton) Knowlton. Kryshtofovich (1958) described the morphology of dispersed fruits from the Rarytkin and Tsagayan floras of eastern Russia and reviewed the distribution of these fruits in the Late Cretaceous and Paleocene floras of northern Asia and North America.

Subsequently, V. A. Krassilov (1973, 1976) described more completely preserved infructescences under the name Trochodendrocarpus arcticus (Heer) Kryshtofovich based on new findings from the Paleocene Upper Tsagayan Formation in the Amur Region of Russia. He interpreted this fructification as a paniculate in-fructescence. According his description the axis of infructescence bears several alternating lateral racemose branches with spirally arranged crowded styled pods, borne in pairs or single on short stalks.

I. A. Iljinskaja (1974a) considered genus Trochodendrocarpus as invalid, because names Nyssidium and Jenkinsella had priority before Trochodendrocarpus. Besides that Kryshtofovich didn't provide a generic diagnosis. Later Krassilov tried to validate the name Trochodendrocarpus by retypification and chose a neotype from the Tsagayan locality (Krassilov, Fotyanova, 1995). However this solution was unsuccessful, because Kryshtofovich stated Nyssa arctica as the type species for the genus Trochodendrocarpus and that its type came from the Paleocene of Greenland.

Iljinskaja (1974a) suggested using the name Nyssidium Heer as the earliest appropriate generic name for this kind of fruits. This genus was established by Heer (1870) for five new species of elongated dispersed fruits from the Paleocene of Spitsbergen. These fruits differ from those of Nyssa arctica by smaller sizes and some other features (Budantsev, Golovneva, 2009), but drawings of both fruit types in the Heer's monographs look very similar (pl. I, fig. 1). Therefore many authors treated fruits from Greenland and Spitsbergen as congeneric or even conspecific.

The name Nyssidium was used sometimes in previous years. It was first applied after Heer by J. Schmalhausen (1890), who described two species: N. spicatum Schmalhausen and N. geminatum Schmalhausen from the Turonian-Coniacian deposits of the New Siberian Islands. The figured specimens of second species are very similar to "Nyssa" arctica fruits and probably congeneric. The first species possibly presents another type of fructification.

Later, A. Hollick (1936) identified numerous racemes of follicular fruits from the Tertiary deposits of Alaska with Nyssidium ekmanii Heer from Spitsbergen.

Iljinskaja synonymized five species of genus Nyssidium, described by Heer, under the name N. ekmanii Heer and chose the lectotype on the basis of specimens figured by Heer. The second species, Nyssidium arcti-cum (Heer) Iljinskaja was created as new combination with Nyssa arctica. The lectotype of latter species was also chosen by Iljinskaja (Heer, 1869, pl. 43, fig. 12c). She considered that Nyssidium arcticum differs from N. ekmanii only by bigger sizes and more acute apices.

Infructescences, fruits and seeds from the British early Tertiary were reexamined by P. R. Crane (1984). He united branched racemose infructescences previously assigned to Carpolithus gardneri and fruits Jenkinsella apocynoides as a single species Nyssidium arcticum (Heer) Iljinskaja and indicated, without explanation, another lectotype for this species (Heer, 1869, pl. 50, fig. 6). The morphology of fruits was described in detail. Some of them contained winged seeds in situ, similar with those described by Brown. Crane also reconstructed a whole Nyssidium plant and compared its fructification and foliage with those of extant Cer-cidiphyllum, supposing that these plants were closely related. For associated leaves Crane (1984) applied separate names Trochodedroidesprestwichii (De la Harpe) Crane.

The point of view by Iljinskaja and Crane was widely accepted and Nyssidium arcticum was recorded from many Late Cretaceous and Paleogene floras of Northern Hemisphere (Budantsev, 1983; Crane, 1984; McIver, Basinger, 1993; Golovneva, 1994,). The fruits from different localities varied in size and shape, but all of them were usually attributed to one species because of wide variability of fruits in each site and overlapping variability ranges from different sites.

Abundant specimens from the upper Paleocene Paskapoo Formation, the Joffre Bridge locality, Alberta, Canada, allowed describing the most complete Cercidiphyllum-like plant (Crane, Stockey, 1985). Joffrea speirsii Crane et Stockey is known from shoots, leaves, pistillate inflorescences, infructescences, winged seeds and seedlings. Associated staminate inflorescences were described later as Alasia (Golovneva, 2006a). The investigation of Joffrea speirsii revealed the presence of both long and short shoots and different details of carpels and fruits. With these findings knowledge of Cercidiphyllum-like fossil plants has increased considerably.

On the basis of this material a more comprehensive comparison of all known complete fructification structures and living Cercidiphyllum was undertaken. Crane and Stockey (1985, 1986) considered the infructescences of all Cercidiphyllum-like plants as a raceme. Remains of infructescences from the Upper Tsagayan Formation, described as Trochodendrocarpus arcticus, they also interpreted as leafy twigs, bearing racemose fructifications rather than panicle. Infructescences of Trochodendrocarpus from the Amur Region and Nyssidium arcticum from England were apparently produced on the long shoots, and unlike the con-

dition in Joffrea, which had infructescences on short lateral shoots. The condensed inflorescences in the modern Cercidiphyllum were hypothesized to have evolved from the racemose type seen in Joffrea and other fossil species, accompanied by a change in suture orientation (Crane, Stockey, 1986). Genus Joffrea was interpreted as an extinct representative of the family Cercidiphyllaceae. But Krassilov and Fotyanova (1995) continued to treat specimens from the Upper Tsagayan Formation as branched infructescences, which obviously have been shed as a unit. They indicated that there are no definite leaf scars near the base of side branches and concluded that these plants are more closely related to Hamamelidaceae.

N. M. Makulbekov (1988) described Trochodendrocarpus asiaticus Makulbekov from the Paleocene of Mongolia. These infructescences were produced on short lateral shoots like in Joffrea speirsii.

Later, well-preserved infructescences, attached to the long shoots, were documented in detail from the Paleocene of north-east China as Nyssidium jiayinense G. P. Feng, C. S. Li, Zhilin, Y. F. Wang et Gabrielyan (Feng et al., 2000). The authors interpreted these infructescences as paniculate, like "Trochodendrocarpus arcticus" from the Upper Tsagayan Formation.

Recently the Nyssidium fruits from the type locality Cape Staratschin (the Barenzburg Formation) were refigured and redescribed in a monograph dealing with revision of the Paleogene Spitsbergen flora (Budantsev, Golovneva, 2009). Heer described five species from this locality, which were subsequently joined under the name N. ekmannii (Iljinskaya, 1974a; Budantsev, Golovneva, 2009).

The fruits of the type species of Nyssidium resemble in a general way the individual fruits of Cercidiphyl-lum-like plants, but they differ in being twice smaller and without evidence of follicular nature. The fruits of "Nyssa" arctica and other remains of this kind are follicles. They are gradually attenuated at the base into a short stalk and at the apex into a terminal style, have suture grooves, longitudinal or oblique ridges diverging from ventral suture, and transverse striae. The apex and base of Nyssidium are rounded and longitudinal ridges are thinner, more regular and meridional, converging near the base and the top of the fruit. They have no suture grooves and transverse striation. Only one specimen (lectotype) has an unclear stalk (pl. I, fig. 1). There is no evidence that Nyssidium had the fruits arranged in a raceme and winged seeds inside. It's most likely that the similarity of "Nyssa" arctica and Nyssidium ekmanii is only superficial. Really, Nyssidium ekmanii has so few distinctive features (small size, elongated shape and ribbed surfaces) that may be fit with many systematically different taxa. Heer never united fruits of "Nyssa" arctica and Nyssidium under one name. We believe that Nyssidium corresponds to another type of fruits or possibly seeds.

Although the name Nyssidium is now widely used, it should be rejected for the racemes and isolated follicles, associated with Trochodendroides leaves. Any case, delimitation of this kind of fructification from other similar remains will be problematic. For example, Samylina (1961) has described elongated fruit (or seed?) with longitudinal ridges from the Neocomian of Russian Far East as Nyssidium orientale Samylina. Although the characters of this fruit correspond to diagnosis of type species Nyssidium ekmanii (excluding size), its affinity, not only to Cercidiphyllum-like plants, but to angiosperms in general is doubtful. The affinity of N. spicatum from the Late Cretaceous of the New Siberian Islands (Schmalhausen, 1890) is also uncertain.

Unfortunately all these investigations have not resolved nomenclature problems, connected with fructifications associated with Trochodendroides leaves. This diversity is impossible to analyze in the network of present generic nomenclature. The genus Joffrea was created for a hypothetical whole plant, not only for the infructescence that was designated as holotype (Crane, Stockey, 1985). The names Trochodendrocarpus and Berrya are inappropriate as well as the name Nyssidium are now rejected for this kind of infructescence.

Numerous new records of complete fructifications from Northeastern Asia and other regions forced us to undertake the revision of morphology and names, which were given to these fossils at different times.

The general construction of racemose infructescences and fruits of all known specimens is practically identical. This similarity allows supposing that these plants were closely related and differences are not sufficient for separate generic designation. The main distinguishing feature between these fructifications is position of infructescence on either short or on long shoots. Other differences in shape, sizes, number of fruits per infructescence, in dehiscence mode, frequency of bicarpellate flowers and crowding of follicles are not sufficient for separate generic designation and sometimes may depend on preservation and maturity of fruits and also from author's interpretations. To avoid further confusion, we recommend considering all known findings under one generic name and differentiating them specifically.

The earliest generic name originally designated for fruits of Cercidiphyllum-like plants with distinguishable morphology and critical details of inner structures is Jenkinsella Reid et Chandler. We recommend applying the name Jenkinsella to dispersed follicular fruits, fruits in raceme and infructescences, attached to the shoots.

Now we include 10 species in this genus: Jenkinsella apocynoides Reid et Chandler, J. arctica (Heer) Bell, J. filatovii (Samylina) Golovneva et P. Alekseev, comb. nov., J. krassilovii Golovneva et P. Alekseev, sp. nov., J. gardnerii (Chandler) Golovneva et P. Alekseev, comb. nov., J. knowltonii Golovneva et P. Alekseev, sp. nov., J. jiayinensis (G. P. Feng, C. S. Li, Zhilin, Y. F. Wang et Gabrielyan) Golovneva et P. Alekseev, comb. nov., J. conferta P. Alekseev et Golovneva, sp. nov., J. makulbekovii Golovneva et P. Alekseev, sp. nov., J. vily-uensis Golovneva et P. Alekseev, sp. nov.

The first name, J. apocynoides, is applied to the permineralized fruits from the London Clay Formation for which many morphological and anatomical details were revealed Crane (1984). The second name, J. arctica, we recommend to use as broadly defined species to accommodate fruits preserved mostly as impression without anatomical details. Variations in shape and size usually do not provide sufficient basis for separation of morphological species. The raceme of third species, J. filatovii, come from the early-middle Albian Omsukchan Formation of the Kolyma River basin, Northeastern Russia. The other seven species are represented by infructescences, attached to the shoots.

MATERIAL

Infructescences and fruits of Jenkinsella were investigated from numerous localities from Spitsbergen, North America and Eurasia.

Type material of "Nyssa" arctica comes from the Paleocene Atanekerdluk Formation in West Greenland. The specimens were collected by E. Whymper in 1867 and are stored in Natural History Museum, London (specimen V.11319).

The genus Nyssidium was described from the Paleocene carbonaceous shale of the Barenzburg (Firkant-en) Formation outcropping near Cap Staratschin (Festningsodden) at western coast of Green Harbour, Spitsbergen (Heer, 1870; Budantsev, Golovneva, 2009). Type material of Nyssidium was examined in the Swedish Museum of Natural History (specimens with prefix S).

Jenkinsella apocynoides comes from the London Clay Formation (early Eocene), Great Britain. The type specimens were collected by D. J. Jenkins in Herne Bay, and are stored in Natural History Museum, London.

The remains of J. filatovii come from early-middle Albian deposits of the Omsukchan and the Toptan formations (Samylina, 1976), Kolyma River basin, Northeastern Russia (Fig. 1). The collections are housed at the Komarov Botanical Institute, St. Petersburg (specimens with prefix BIN).

The original material, described by Krassilov (1976) as Trochodendrocarpus arcticus (Heer) Krysh-tofovich, has recently been reexamined in detail and assigned to new species Jenkinsella krassilovii. The specimens were collected by Krassilov in the locality Belaya Gora (the White Mountain). It is situated in Amur Region (Russian Far East) along the Bureya River bank near the mouth of the Darmakan River. Previously this section was considered as the stratotype of the Tsagayan Formation (Krassilov, 1976). Now the Maastrichtian-Paleocene deposits of the Zeya-Bureya basin are joined in the Tsagayan Group. The plant-bearing beds belong to the Darmakan (Upper Tsagayan) Formation and are dated as the Paleocene (Bugdaeva et al., 2001; Sun et al., 2007). The specimens of J. krassilovii are deposited in the Institute of Biology and Soil Science, Far East Branch Russian Academy of Sciences, Vladivostok (prefix IBSS) and partly in the Komarov Botanical Institute.

Infructescences of J. jiayinensis were previously described as Nyssidium jiayinense (Feng et al., 2000). Material is stored in National Museum of Plant History of China, Institute of Botany, Beijing (prefix CBP). Specimens of excellent preservation were discovered from the deposits of the Wuyun Formation in eastern part of Heilongjiang Province, north-east China. The megafossil flora from the Wuyun coal mine contains many common species with the Tsagayan floral assemblage. Therefore the Wuyun Formation was correlated with the Darmakan Formation of the Tsagayan Group and its age is also considered as the Paleocene, may be slightly younger, then age of the Darmakan Formation (Sun et al., 2002, 2005, 2007).

The remains of J. makulbekovii come from the Paleocene deposits of the Naran-Bulak Formation, Southern Gobi, Mongolia, (Makulbekov, 1988). The collections are housed at the Palaeontological institute RAS, Moscow (specimens with prefix PIN).

Two more types of these infructescences were found recently in the Cretaceous deposits of Siberia. The specimens of J. conferta were collected from the deposits of the Sym Formation in the Kiya River basin, Western Siberia by L. Golovneva and P. Alekseev in 2008. The site with fossil plants is located in 10 km from Mariinsk town in Kemerovo Region, near Archekas Hill (Fig. 1). The Sym Formation consists of light grey, weakly cemented sandstone with lenses of dark grey siltstone and mudstone with a total thickness about 300 m (Golovneva, Shczepetov, 2010). The Archekas assemblage is very similar in composition with

Fig. 1. Localities of Jenkinsella in Northern Asia.

the Antibes assemblage from Antibes quarry near Mariink. Both these assemblages were joined in the An-tibes flora and dated as the Coniacian—Santonian (Alekseev, 2014; Alekseev et al., 2014). Plant remains are stored at the Komarov Botanical Institute.

The specimens of J. vilyuensis were collected by geologist G. I. Mirkin in 1963 from the Turonian-Co-niacian deposits of the upper part of the Timmerdyakh Formation, the Vilyui River basin, Eastern Siberia. The Timmerdyakh Formation consists of cross-bedded sandstones and tabular siltstones and mudstones that were accumulated in channel, floodplain and lake environments (Golovneva, 2005, 2006b). The collections are housed at the Komarov Botanical Institute.

SYSTEMATICS Family CERCIDIPHYLLACEAE

Modern fam. Cercidiphyllaceae includes only one genus Cercidiphyllum, distributed in China and Japan. It contains two species: C. japonicum Sieb. et Zucc. and C. magnificum (Nakai) Nakai (Fu, Endress, 2001). This family was placed in Trochodendrales (Dahlgren, 1980), in Hamamelidales (Cronquist, 1981) or was treated as a separate order Cercidiphyllales (Takhtajan, 1996). Recently the family is considered a member of Saxifragales (APG III, 2009).

Fossil Cercidiphyllaceae are significantly more diverse than modern and are represented by several genera. The most complete plant was described under the name Joffrea. It is based on shoots, leaves, pistillate inflorescences, infructescences, winged seeds, and seedlings (Crane, Stockey, 1985).

The majority of authors considered dispersed fossil leaves from the Cretaceous and Paleogene deposits as belonging to genus Trochodendroides. It is known from the late Albian, and more than fifty species are described from numerous localities of Northern Hemisphere (Golovneva, Alekseev, 2010).

The genus Alasia was established for male inflorescences (Golovneva, 2006a). This genus includes three species from the Cretaceous and Palaeogene of Siberia and North America. Pollen from one specimen was studied by Krassilov and Kodrul (2008).

For dispersed fruits and raceme infructescences we proposed to use the name Jenkinsella. The dispersed winged seeds from follicular fruits have no distinctive generic name. Kryshtofovich and Baikovskaya (Bai-kovskaya, 1956; Kryshtofovich, Baikovskaya, 1966) suggested name Trochodendrospermum for them, but it is invalid, because was not typified by any species. L. J. Hickey (1977) described winged seeds as Carpolithes lunatus Hickey. The anatomy of seeds did not investigated yet.

Fossils from the Oligocene associated with Cercidiphyllum infructescences usually are included in modern genus Cercidiphyllum (Jahnichen et al., 1980; Manchester, Meyer, 1987; Kovar-Eder at al., 1998). But this name also used for dispersed leaves from more ancient deposits from the Paleocene (Iljinskaya, 1974b; Chandrasekharam, 1974; Budantsev, 1983).

Genus JENKINSELLA Reid et Chandler

Type species: J. apocynoides Reid et Chandler, Great Britain, the London Clay Formation, late Paleocene-early Eocene.

Original diagnosis (Reid, Chandler, 1933). Fruit ovoid, pointed at both ends, one-celled, many-seeded; placentation parietal (?) along a ventral suture, exocarp formed of transversely aligned cells with many equidistant longitudinal strands of fibers; endocarp formed of transversely aligned fibers. Length 8—11,4 mm, diameter 4—6 mm.

Diagnosis emended. Infructescences racemose with spirally arranged follicles, borne in pairs or singly on short stalks attached to short side branches of the infructescence axis. Follicles are ellipsoidal, oval or obovate in outline, elliptic to circular in transverse section, tapering at the base into a short stalk and at the apex into a terminal style, with subparallel longitudinal ridges and fine transverse striation. Ventral sutures of single follicles are oriented usually adaxially with respect to the inflorescence axis, and follicles borne in pairs have the ventral sutures opposite each others. The follicle wall three-layered, with thin epidermis, mesocarp with longitudinal fibres and endocarp with thin transverse fibers. Seeds numerous, winged, crescent-shaped; lying transversely one above the other within the locule; attached along ventral suture in two rows.

The infructescences alternate, bearing on short or long shoots, developing from lateral or apical buds. Distinct joints there are in the point where each raceme is attached to the shoot and between the side branch of infructescence axis and the follicle stalk.

Jenkinsella apocynoides Reid et Chandler Pl. I, fig.10

Jenkinsella apocynoides Reid et Chandler, 1933, p. 481, pl. 28, fig. 1—5. — Chandler, 1961, p. 84, pl. 8,

fig. 18—20.

Nyssidium arcticum (Heer) Iljinskaja, in Crane, 1984, p. 211, pro parte, fig. 35—48.

Holotype: dispersed pyritized fruit, spec. V.23088, Great Britain, Herne Bay, the London Clay Formation, early Eocene; Reid et Chandler, 1933, pl. 28, fig. 1, 2.

Description (after Chandler, 1961; Crane, 1984). Infructescences are racemose, bearing single or paired follicles. Follicles are ellipsoidal to sub-ovoid, elliptic to circular in transverse section, gradually attenuated at the base into a short stalk and at the apex into a terminal style. Total length of follicles, including the stalk and style, is 8—11,4 mm, diameter 4—6 mm. Follicle dehiscing by a single suture along the full length of the locule. Fruits wall is approximately 0,5 mm thick, with coarse longitudinal ridges and grooves; wall of two distinct layers, epidermis not seen. Mesocarp is 0,3 mm thick, formed of stout longitudinal fibrous bands approximately 150 |im wide, separated by areas with fine transverse striations. Suture flanked by a longitudinal fibrous band on either side, other longitudinal bands diverging at a low oblique angle across the follicle surface, occasionally branching and anastomosing, becoming more or less parallel to the midline

opposite the suture. Inner layer of follicle wall (endocarp) is 0,2 mm thick, formed of many layers of transverse tightly packed fibers, which cover the entire locule surface except close to the suture.

Along the edges of the suture on the locule-cast are two ridges 0,5 mm wide with numerous (50—60) evenly spaced small circular scars arranged in one-two irregular rows, representing, probably, the casts of placentae. The scars of one row are alternating with those of the other.

Seeds borne on the ridges on either side of the suture, arranged transversely in two rows within the locule; their long axes aligned dorsiventrally. The straight margins are contiguous along the mid-line of the fruit with the convex margins against the fruit wall. Seeds are tapering proximally, truncate or shallow notched at the hilar end, broader and more rounded at the distal end, 3,2—4,6 mm long, maximum width 0,8—2,3 mm at about the middle of the seed. Seed body is narrowly obovate to narrowly elliptic, 1,2—3,4 mm long, 0,6—1,2 mm in maximum width. Seed body positioned proximally and lying oblique to the long axis of the seed parallel to the straighter proximal portion of the convex seed margin, sometimes separated from it by a narrow strip of the wing. Surface of the seed body and the wing with fine longitudinal striation; striation frequently converging in the distal part of the wing, or towards the chalaza.

Remarks. These fruits were described firstly as locule-casts from the London Clay Formation. Later impressions of similar fruits both dispersed and joined in racemose infructescences were discovered in the Woolwich and Reading Beds. Chandler (1961) and Crane (1984) regarded all these fossils as belonging to the same species (Jenkinsella apocynoides Reid et Chandler and Nyssidium arcticum (Heer) Iljinskaja, respectively). Three-dimensional specimens from the London Clay Formation exhibit much more details of inner structure of these fossils than can be seen on impressions. But there is not any evidence to distinguish more than one species in the British early Tertiary, until better material will be discovered. However we don't attribute to this species shoots with several infructescences, described as Carpolithes gardnerii Chandler owing to another type of completeness of this fossils (not only infructescences, but infructesceces attached to the shoots). These specimens are placed in the species Jenkinsella gardnerii.

Jenkinsella arctica (Heer) Bell Pl. I, fig.12, 13

Jenkinsella arctica (Heer) Bell, 1949, p. 57, pl. 4, fig. 6, pl. 44, fig. 1.

Nyssa arctica Heer 1869, S. 477, Taf. 43, Fig. 12c, Taf. 50, Fig. 5, 6. — Heer, 1876, S. 80, Taf. 19, fig. 1—9. Cercidiphyllum arcticum (Heer) R. W. Brown, 1939, p. 492, pro parte, pl. 54, fig. 1, 4, 13, pl. 56, fig. 3—5;

1962, p. 70, pro parte, pl. 37, fig. 1, 23, 24, pl. 38, fig. 5, 6, 15. Trochodendrocarpus arcticus (Heer) Kryshtofovich, nom. illeg., 1958, p. 113, pl. 13, fig. 4. — Budantsev, 1983, pl. 14, fig. 2, pl. 16, fig. 3—6. — Philippova, Abramova, 1993, p. 132, pl. 74, fig. 6—8. — Budantsev, 2006, p. 64, pl. 17, fig. 5—7. — Philippova, 2010, p. 109, pl. 8, fig. 6, 7. Nyssidium arcticum (Heer) Iljinskaja, 1974a, p. 124, pl. 53, fig. 9-13. — Kvacek, Manum, Boulter, 1994, p. 111, pl. 3, fig. 10. — McIver, Basinger, 1993, p. 37, pl. 20, fig. 5, 6, pl. 21, fig. 3, pl. 22, fig. 1-3. — Go-lovneva, 1994, p. 84, pl. 12, fig. 711, pl. 29, fig. 1, 2, pl. 67, fig. 1, pl. 68, fig. 2. — Budantsev, Golovneva, 2009, pl. 16, fig. 8, pl. 86, fig. 4, 5, 11. — Manchester, 2014, text-fig. 7, fig. 4. Carpolithes arcticus (Heer) Hickey, 1977, p. 151, pl. 53, fig. 3-7. — Tanai, 1981, p. 474, pl. 9, fig. 2—5. — Tao,

Xiong, 1986, p. 131, pl. 7, fig. 5, 5a. Sabalites fructifer Lesqureux, 1878, p. 114, pro parte, pl. 11, fig. 3a. Nyssa (?) rostrata A. Pojarkova, 1939, p. 668, fig. 17. Carpolithes arachioides Lesquereux, 1873, p. 403.

Leguminosites arachioides (Lesquereux) Lesquereux, 1878, p. 301, pl. 59, fig. 14. — Ward, 1887, p. 65,

pl. 29, fig. 2. — Penhallow, 1908, p. 61, fig. 14. — Berry, 1916, p. 249, pl. 48, fig. 9. — Berry, 1935, p. 64. Leguminosites borealis Dawson (non Heer 1883), 1889, nom. illegit., p. 72, pl. 10, fig. 7. Nyssidium ekmanii auct. non Heer; Hollick, 1936, p. 159, pl. 30, fig. 4b, pl. 120, fig. 8—12. N. geminatum Schmalhausen, 1890, p. 16, pl. 1, fig. 30, 30a. Carpites japonicus (Endo) Tanai, 1970, p. 503, pl. 19, fig. 3, 5. Cercidiphyllum sp., Chandrasekharam, 1974, p. 23, pl. 9, fig. 72, 73, pl. 13, fig. 91.

Lectotype (Iljinskaja, 1974a): dispersed fruit, V.11319; Heer, 1869, pl. 43, fig. 12c sub. nom. Nyssa arctica Heer, West Greenland, the Atanekerdluk Formation, Paleocene (non Heer, 1869, pl. 50, fig. 6 as stated by Crane, 1984). — Pl. I, fig. 12.

Diagnosis emended. Follicular fruits both dispersed and in racemose infructescences. The follicles spirally arranged, single or in pair, on short stalks, attached to short side branches of the inflorescence axis, with remnants of style, with subparallel longitudinal or oblique ridges and thin transverse striation. Follicles elliptic, oval or obovate in outline, elliptic to circular in transverse section. Seeds numerous, winged, crescent-shaped.

Remarks. This species is established for remains of fruits and infructescences, for which only characters of outer morphology are known. In the Cretaceous and Paleogene deposits many such fruits were described. In different localities these follicular fruits distinguished in their shape and sizes. However the distinction of separate species is practically impossible in consequence of high variability and overlapping ranges of morphological characters.

Jenkinsella filatovii (Samylina) Golovneva et P. Alekseev, comb. nov.

Pl. I, fig. 6—8

Kenella filatovii Samylina, 1976, Cretaceous Flora of the Omsukchan, p. 94, pl. 48, fig.. 7—10, 11а, 13а. Nyssidium filatovii (Samylina) Golovneva, in Golovneva, Alekseev, 2010, p. 158, pl. 19, fig. 7—9.

Holotype: dispersed fruit, spec. BIN 511/24, Northeastern Russia, the Kolyma River basin, the Sugoy River, the Omsukchan Formation, early-middle Albian; Samylina, 1976, pl. 48, fig. 9. — Pl. I, fig. 7.

Description. Follicular fruits are single or in raceme, narrowly ellipsoid or narrowly obovate, 13—16 mm in length and 4—6 mm in diameter. Base is cuneate, decurrent, with short stalk. Apex is rounded or acute with attenuate curve style 2—3 mm in length. Outer surface of fruits has thin subparallel longitudinal striation.

Remarks. This species differs from Jenkinsella arctica and J. apocynoides by narrow elongated fruits with rather long curve style and also by thinner longitudinal striation. The follicles of J. filatovii are similar with young follicles of J. jiayinensis that have comparable size, long tapering styles up to 4 mm and poorly developed locules and longitudinal ridges.

Jenkinsella krassilovii Golovneva et P. Alekseev, sp. nov.

Pl. II, fig. 1—7

Trochodendrocarpus arcticus (Heer) Kryshtofovich, nom. illeg., Krassilov, 1973, p. 173, Fig. 7

A—H. — Krassilov, 1976, p. 60, pl. 21, fig. 1. — Krassilov, Fotyanova, 1995, p. 88.

Etymology — in honor of Russian paleobotanist V. A. Krassilov.

Holotype (designated here): shoot with infructescences of follicular fruits, spec. IBSS 563/221, Russia, the Amur Region, the Bureya River basin, the Belaya Mountain locality, the Darmakan (Upper Tsagayan) Formation, Paleocene. — Pl. II, fig. 6, 7.

Diagnosis. The long shoots bear widely spaced alternate lateral racemose infructescences. The in-fructescences are 50—100 mm long and bear 8—14 crowded follicles at distance of approximately 2—4 mm. A distinct swollen joint is visible where each raceme is attached to the long shoot. The follicles are borne in pairs or singly on short, longitudinally striated stalks 2—3 mm long. Side branches of the infructescences axis are very short. Follicles are widely elliptical in outline, suborbicular in transverse section, 15—30 mm long, 7—12 mm in diameter. The style is about 3 mm long, straight or slightly curved, reflexed. Fruits demonstrate various stages of dehiscence from a short apical split to complete separation of valves.

Description (after Krassilov, 1973, 1976). The long shoots bear several widely spaced alternate lateral racemose infructescences. The best-preserved specimen reaches 30 cm long and bears 6 racemes at intervals of 30—50 mm. The five racemes are in lateral position. Position of upper infructescence is unclear, because apical part of shoot is badly preserved. The infructescences are up to 100 mm long and bear 8—14 crowded follicles at distance of approximately 2—4 mm. The elongation of raceme axis is probably continued up to the fruit dehiscence. The raceme is gradually becoming looser. A distinct joint is visible where each raceme is attached to the long shoot. The follicles are spirally arranged, borne in pairs or singly on short, longitudinally striated stalks. The junction between the infructescence axis and the follicle stalk is invisible, although some of the dispersed follicles appear to have become detached at this point. Follicles are elliptical in outline, suborbicular in transverse section, up to 30 mm long. The style is about 3 mm long, straight or slightly curved. The dorsal face shows a median groove and subparallel longitudinal ridges. The ventral face has more prominent suture and ridges, diverging obliquely. The orientation of

ventral sutures in the follicles is unclear. Internal casts show fine transverse striation of the inner surface. The ventral suture is marked on the internal cast as a conspicuous groove, flanked with ridges. There are series of fruits demonstrating various stages of dehiscence from short apical split to complete separation of valves. The valves are persistent. In some fruits elongated incrustation were found, that were interpreted as row of overlapping seeds (Krassilov, 1973). Dispersed seeds were also found in association. They are winged, crescent-shaped or horse-shoe shaped. The wing is curved, clasping the seed body, with maximum width about the middle, gradually narrowed into apex. The wing surface is covered with very fine, crossed striation. The seed body is elongate-elliptical to narrowly lanceolate, 2—3 mm long, with longitudinally striated surface.

Remarks. Krassilov (1976) treated all Cercidiphyllum-like leaves from the Upper Tsagayan Formation as one species — Trochodendroides arctica (Heer) Berry and supposed that these leaves and "Trochodendro-carpus arcticus" reproductives structures belonged to one plant species. Iljinskaja (1972, 1974c) considered these leaves as belonging to three different genera: Cercidiphyllum, Trochodendroides and Cocculus. The rather large ovate leaves (6—10 cm long) with attenuate apex, cuneate to cordate base and crenate margin, which are usually associated with Jenkinsella krassilovii, she assigned to Trochodendroides amurensis (Kry-sht. ex Iljinskaja) Iljinskaja.

Jenkinsella jiayinensis (G.P. Feng, C.S. Li, Zhilin, Y.F. Wang et Gabrielyan) Golovneva et P. Alekseev, comb. nov.

Nyssidium jiayinense G. P. Feng, C. S. Li, Zhilin, Y. F. Wang et Gabrielyan: Feng et al., 2000. Nyssidium

jiayinense sp. nov. (Cercidiphyllaceae) of the Early Tertiary from north-east China, p. 475, fig. 1—28.

Holotype: shoot with infructescences of follicular fruits, spec. CBP 9654, China, Heilongjiang Province, Jiayin county, Jiayin coal field near Wuyun village, the Wuyun Formation, Paleocene; Feng et al., 2000, fig. 1—3.

Diagnosis emended. The long shoots bear several widely spaced alternate lateral and one terminal racemose infructescences. The infructescences are up to 40—70 mm long and bear 14—20 crowded or sparsely arranged follicles. A distinct swollen joint is visible where each raceme is attached to the long shoot. The follicles are occurring always in pairs. Their common stalk has conspicuous joint between the base of stalk and side branch of infructescence. Side branches are orientated spirally at the infructescence axis. Ventral sutures of follicle in pairs are opposite each other. Follicles are 14—28 mm long, elliptic or obovate in outline, elliptic to circular in transverse section, and gradually tapering into terminal style 2—4 mm long. Young follicles are narrowly elliptic in outline, 13—15 mm long, with a long tapering style. Follicles dehisced only along the ventral suture. Seeds are winged and crescent in outline with one edge convex and the other straight to slightly concave. Seeds are often 3—5 mm long and 1—3 mm wide. Seed body is narrowly elliptic, lying oblique to the long axis of the seed and parallel to the straight proximal portion of the concave seed margin. Seed body is 2—3 mm in long axis and 1—2 mm in short axis.

Description. The best-preserved specimen (holotype) is represented by a shoot up to 90 mm long with three lateral racemes; shoot tip is aborted. Two other specimens ended by infructescence, which was developed from apical bud (Feng et al., 2000, fig. 9, 10, 12). Some axes of racemose infructescence have small transverse ridges in the base (Feng et al., 2000, fig. 7), that may be interpreted as bud scale scars or small basal bracts scars.

Feng et al. (2000) noted, that fact of considerable variation of follicle size perhaps indicates the different developmental stages. Young follicles were 14—16 mm long with long tapering styles up to 4 mm and with poorly developed locules and longitudinal ridges. Mature follicles reached 20—28 mm long and had short styles about 2 mm long and well developed locules and ridges.

Comparison. Reproductive shoots ofJenkinsella jiayinensis are very similar with shoots ofJ. krassilovii. There is no distinct difference in the follicle morphology between these taxa, but the follicle number per raceme in J. krassilovii is 8—14, while in the racemose ofJ. jiayinensis it is 14—20. The follicles in J. jiayinensis occurring always in pairs and opened along the ventral suture only, but in J. krassilovii the paired follicles are predominate and fruits demonstrate various stages of dehiscence from short apical split to complete separation of valves. The infructescences in J. jiayinensis have crowded or sparsely arranged follicles and common fruit stalks attached to rather long side branches of infructescence axis with marked joint in the base. Follicles are apparently abscised at this joint. In J. krassilovii follicles in raceme are always crowded and side branches of infructescence axis are very short and practically invisible.

Remarks. Following to Krassilov (1973), Feng et al. (2000) have interpreted these reproductive units as paniculate infructescence, but we considered them as shoots with racemose infructescences because racemes have marked swollen junction and bud ring in the base.

Leaves with crenate margin assigned to Trochodendroides arctica (Heer) Berry by Tao and Xiong (1986, p. 124, pl. 2, fig. 8; pl. 6, fig. 7; pl. 7, fig. 1—4; pl. 16, fig. 2) have been found in the same sedimentary layer as the infructescences and are considered to be linked to J. jiayinensis.

Jenkinsella gardnerii (Chandler) Golovneva et P. Alekseev, comb. nov.

Carpolithes gardnerii Chandler, The Lower Tertiary floras of southern England. I. Palaeocene floras: London Clay flora, 1961, p. 85, pl. 9, fig. 1—5. Nyssidium arcticum (Heer) Iljinskaja, Crane, 1984, pro parte, p. 211, fig. 18, 26a.

Holotype: shoot with infructescences of follicular fruits, spec. V.15335-7, southern England, the Reading Beds, upper Paleocene; Chandler, 1961, pl. 9, fig. 1.

Diagnosis emended. The terminal shorten shoot bearing lateral and apical racemose infructescences. The junction between the infructescence axis and shoot is marked by a swollen joint. Short shoot is marked at both ends by bud rings. Under these rings there are rows of several small (1,0—1,5 mm in diameter) sub-circular scars with irregular transverse ridges above and below. Spirally arranged and widely spaced (5—6 mm apart) follicles are elongate sub-elliptical in outline, attenuated into stalk and style, dorsal margin less curved than ventral, style slightly reflexed. Length of fruits is 20—25 mm; diameter 6—8 mm. Mode of follicle dehiscence is unclear. The follicles occur singly or occasionally in pairs on common stalk, borne on short side branches of infructescence axis with a conspicuous joint at the base of the stalk.

Comparison. This species is represented only by holotype. It display upper part of shorten shoot with one incomplete apical and one incomplete lateral racemose infructescences. The way of attachment of third fragmented infructescence is uncertain. Other fertile shoots, illustrated by Crane (1984), preserved not so well and did not show clear characters of raceme attachment.

Jenkinsella gardnerii differs from J. krassilovii and J. jiayinensis by arrangement of infructescences at terminal shorten shoot and by predominance of single follicles. Widely spaced follicles of J. gardnerii with conspicuous joint at the base and rather long side branches of infructescences are very similar with the same structures ofJ. jiayinensis. Because the racemes of J. gardnerii are not complete, more detailed comparison is impossible.

Jenkinsella knowltonii Golovneva et P. Alekseev, sp. nov.

Pl. III, fig. 9

Berrya racemosa (Knowlton) Knowlton, nom. illeg., Knowlton, 1930, p. 134, pl. 41, fig. 4, 5.

Nomenclature remarks. The upper part of a raceme with three fruits was firstly found by L. Lesquereux from the Denver Beds at Golden, Colorado, in close association with pinnate palm leaf. He described fruits and leaves under one name Sabalites fructifer Lesquereux (1878), although there is no organic connection between these remains. Later Knowlton (1898) in his "A catalogue of the Cretaceous and Tertiary plants of North America" proposed for this specimen new name Nyssa ? racemosa Knowlton, but this species was not described. Long shoots with infructescences from the Denver Formation were described under invalid name Berrya racemosa (Knowlton, 1930). Therefore we proposed new name for these reproductive structures —Jenkinsella knowltonii, in honor of F. H. Knowlton.

Holotype (designated here): shoot with infructescences of follicular fruits, spec. USNM 37720, USA, Colorado, south face of South Table Mountain, 100 feet below the lava cap, the Dawson arkose, Paleocene, collected by Arthur Lakes, figured by Knowlton, 1930, pl. 41, fig. 5. — Pl. III, fig. 9.

Diagnosis. The long shoots bear several widely spaced alternate lateral racemose infructescences and one apical infructescence. The infructescences are 35—50 mm long and bear 5—7 follicles at distance of approximately 2—4 mm. A bud ring with swollen joint is visible where each raceme is attached to the long shoot. Spirally arranged follicles are borne singly on short side branches of the infructescences axis with a joint at the base of the stalk. Follicles are ellipsoidal or oblong, 10—16 mm long, 4—6 mm in diameter, with acute apex, attenuated into short stalk in the base. Mode of follicle dehiscence is unclear. Orientation of ventral sutures is different.

Description. The most perfect specimen is about 8 cm long. This shoot exhibited apical and lateral racemes (Pl. III, fig. 9). The second shoot has two lateral and one apical racemes, but they are incomplete (Knowlton, 1930, pl. 41, fig. 4). The shoots are 2—4 mm in diameter. The length of infructescence is 35— 50 mm. The axis of infructescence is thick, about 2 mm in diameter, strong, erect. Fruits are single, arranged alternately, widely spaced. They are follicular, 10—16 mm long, 4—6 mm in diameter, 5—7 per infructescence, ellipsoidal, short-pediceled, with acute apex, ventral suture, 12—15 subparallel longitudinal ribs and very numerous, thin transverse striae. Some fruits showed a joint (abscission scars) at the base of the stalk, from which they appear to have been detached at maturity. Orientation of ventral sutures is different. There are not any splits along sutures.

Comparison. Jenkinsella knowltonii is comparable with J. krassilovii and J. jiayinensis in arrangement of infructescences at long shoots. In J. gardnerii they arrange at terminal shorten shoot. New species differs from J. krassilovii by smaller sizes of infructescences and fruits and by widely spaced follicles. From J. jiayinensis it differs by follicle number (14—22 in J. jiayinensis and 5—7 in J. knowltonii) and by predominance of single follicles.

Jenkinsella conferta P. Alekseev et Golovneva, sp. nov.

Pl. III, fig.1—5

Trochodendroides elliptica auct. non (Newberry) Kryshtofovich: Baikovskaya, 1957, p. 84, fig. 7.

Etymology — from Latin "confertus" — congested.

Holotype (designated here): branched shoot with infructescences of follicular fruits, spec. BIN 1564/144, Western Siberia, the Kiya River basin, Archekas hill, the Sym Formation, the Coniacian-Santo-nian. — Pl. III, fig. 1.

Diagnosis. The long shoots bear alternate short shoots 2—2,5 mm apart. Raceme infructescences located on short shoots in terminal position. Each raceme is 15—30 mm long, formed by 15—20 spirally arranged closely spaced follicles. The junction between the twig axis and short shoot is marked by a swollen joint. Short shoots bearing 3—5 alternate, closely spaced leaf scars. The follicles are borne on short stalks singly or sometimes in pairs. Follicles are ellipsoid in shape, small, 5—7 mm long, 2—3 mm in diameter, with acute or slightly attenuate apex and obtuse base attenuated in short stalk 0,5—1 mm long.

Description. The long shoots bear alternate short shoots 2—2,5 mm apart. The long shoots are approximately 2 mm in diameter, smooth, with numerous elliptical lenticels 0,3 mm long. Short shoots are 5—7 mm long and 1,5—1,7 mm in diameter, with several transversal ridges, corresponding to remnants of leaf scars. Raceme infructescences located on short shoots in terminal position. The junction between the twig axis and short shoot is marked by a swollen joint. Racemes are 1,5—3 cm long, consisting of 15—20 spirally arranged and densely spaced follicles. They are ellipsoidal in shape, small, 5—7 mm long, 2—3 mm in diameter, with acute or slightly attenuate apex and obtuse base attenuated in short stalk 0,5—1 mm long. Follicles are borne singly or sometimes in pairs. The side branches of infructescence axis are very short. Outer surface of fruits with 7—9 subparallel longitudinal ridges. The inner surface of the locule with thin transverse stria-tion. Some open follicles are filled with sediment. Internal casts occur rarely.

Comparison. This species differs from other species of genus Jenkinsella by position of racemes at the top of short shoots in terminal position and by very small size of follicles and racemes. However, stout (woody?) axes of racemes, three-dimensional arrangement of fruits and roomy solid follicles with short remnant of style and well developed fibers indicate that these fruits were mature and their small size were not connected with early stage of development.

Remarks. Impressions of the Jenkinsella conferta were found in grey siltstone in which leaf remains of Trochodendroides sibirica (Tcherepnin) P. Alekseev predominated.

Jenkinsella makulbekovii Golovneva et P. Alekseev, sp. nov.

Pl. IV, fig. 1

Trochodendrocarpus asiaticus Makulbekov, nom. illeg., Makulbekov, 1988, p. 70, pl. 13, fig. 1—3.

Nomenclature remarks. This species was firstly described by Makulbekov (1988) as Trochodendrocarpus asiaticus. This species name is invalid, because new species was referred to invalid genus Trochodendrocarpus.

We described this species as belonging to genus Jenkinsella with emended species diagnosis and proposed new name Jenkinsella makulbekovii in honor of N. N. Makulbekov.

Holotype (designated here): shoot with infructescence of follicular fruits, spec. PIN 3957/10-6, Mongolia, Southern Gobi, Naran-Bulak, the Naran-Bulak Formation, Paleocene. — Pl. IV, fig. 1.

Diagnosis. Raceme infructescence located on short shoots in terminal position, 55 mm long, formed by 9 spirally arranged widely spaced follicles. Follicles are ellipsoidal in shape, 12—15 mm long, 3—4 mm in diameter, with acute or attenuate apex, and base, tapering into short (1,5—3 mm long) stalk. Subparallel longitudinal ridges are well developed. The follicles are single, their stalks have conspicuous joint with side branches of infructescence. These branches are rather long, 3—5 mm. Ventral sutures of two upper follicles oriented opposite each other, and ventral sutures of other follicles oriented in different directions.

Description. Short shoot is 6 mm long and 3 mm in diameter, with several transversal ridges, corresponding to remnants of leaf scars. It arranges at the fragment of long shoot. Raceme infructescence located on short shoot in terminal position. The junction between the twig axis and short shoot is marked by swelling. Raceme is 55 mm long, consisting of 9 single, widely spaced follicles. Axis of infructescence is about 2 mm in diameter with thin longitudinal striation, bears spirally arranged side branches 3—5 mm long at distance of approximately 5—6 mm. Follicles are ellipsoid in shape, 12—15 mm long, 3—4 mm in diameter, with acute or attenuate straight apex, and base, tapering into short (1,5—3 mm long) stalk. Longitudinal ridges are well developed, diverge from ventral suture under acute angle and are subparallel near dorsal groove. The stalks of follicles are borne on side branches of infructescence under obtuse angle and with conspicuous joint. Ventral sutures of two upper follicles are oriented opposite each other, and ventral sutures of other follicles are oriented in different directions. Follicle dehiscence is unknown.

Comparison. J. makulbekovii is similar with J. conferta in position of raceme infructescense on the top of short shoot, but it differs in bigger sizes and in widely spaced fruits on long side branches. The fruit shape and arrangement of J. makulbekovii show the most similarity to those of J. jiayinensis, but the latter differs in always paired and bigger follicles and in location of racemes on long shoots. In J. krassilovii follicles in raceme are crowded and side branches of infructescence axis are very short and practically invisible, while in J. makulbekovii follicles are widely spaced and side branches of infructescence axis are rather long. There are several species of Trochodendroides leaves in Paleocene flora of South Mongolia (Makulbekov, 1988), so association of J. makulbekovii fructification with definite kind of leaves is uncertain.

Makulbekov (1988) has described from the Naran-Bulak Formation of Mongolia the second species of follicular infructescence under the name Trochodendrocarpus arcticus. It represented by long shoots with laterally arranged racemes. These fossils are resemble with J. jiayinensis, but poor preservation preclude to their exact comparison and description.

Jenkinsella vilyuensis Golovneva et P. Alekseev, sp. nov.

Pl. IV, fig. 2—4

Etymology — from the Vilyui River.

Holotype (designated here): shoot with infructescences of follicular fruits, spec. BIN 1181/578, Eastern Siberia, the Vilyui River basin, the Tymtaidakh River, site 2730, the Timmerdyakh Formation, the Turonian-Coniacian. — Pl. IV, fig. 3.

Diagnosis. The long shoots bear alternate lateral racemose infructescences 22—25 mm apart. Distinct leaf scar is visible under the base of raceme. Racemes are 20—25 mm long and about 10 mm wide, formed by more than 20 spirally arranged closely spaced follicles. The follicles are borne on very short stalks, mostly singly. They are widely elliptical in outline, suborbicular in transverse section, small, 5—6 mm long, 3—3,5 mm in diameter, with slightly attenuate short style and obtuse base. Ventral sutures of follicles oriented in different directions.

Description. The long shoots, about 3 mm thick, bear several alternate racemose infructescences. The best-preserved specimen reaches 6 cm long and bears three lateral racemes at intervals of 22—25 mm. The surface of bark is covered by elliptical lenticels 0,5 mm long. A distinct joint there is in the place of attachment of the raceme to the long shoot. A leaf scar is visible under one raceme. It is triangular in shape, 3 mm wide and 2 mm long with three bundle scars.

Racemes are 20—25 mm long and about 10 mm in diameter, formed by more than 20 spirally arranged closely spaced follicles. Follicles cover practically the whole length of infructescence axis. They are widely ellipsoid in shape, somewhat flattened, small, 5—6 mm long, 3—3,5 mm wide, with slightly attenuate short

style 0,5—0.7 mm long and obtuse base, singly or sometimes in pairs. It is possible to see about 15—20 follicles. Probably their number may be estimated as 20—25. The stalks of follicles and side branches of infructescences are very short. The orientation of ventral sutures in the follicles is different. Follicles are not dehiscent. Their outer surface has several subparallel longitudinal ridges.

Comparison. This species is similar with J. conferta in sizes of follicles and racemes, but differs in arrangement of racemes at long shoots. Other species of genus Jenkinsella differ by bigger sizes of follicles and racemes.

Material. Collection BIN 1181, specimens 577, 579, 582.

DISCUSSION

Comparison of different species of Jenkinsella demonstrates considerable diversity in structure of reproductive shoots, infructescence position, and also in number, sizes and crowding of follicles in infructes-cences (Table 1).

General organization of infructescences is similar in all species of Jenkinsella, where these structures are preserved. This is a raceme with numerous follicles that were borne on short side branches of infructescence axis. Each side branch bears one or two short-stalked follicles. There is the junction between the follicle stalk and the side branch of the infructescence. The follicles or pairs of follicles are often broken away at this joint. This similarity indicates close relationship of all species in spite of differences in position of infructescences.

The differences between species in infructescence and follicle features are insignificant. The size of fruits and racemes varies considerably both within and between species. Length of infructescences is the highest in J. krassilovii (up to 100 mm) and is the smallest in J. conferta (15 mm). Most of follicles range from 14 to 28 mm in length, whereas fruits of J. conferta and J. vilyuensis are significantly smaller, 5—7 mm long. Py-ritized specimens of J. apocynoides from the London Clay are, according Crane (1984), also a little smaller (8—11,4 mm), than compression specimens from the Woolwich and Reading formations.

Especially abundant material was described from the Wuyun Formation of Northeast China (Feng et al., 2000). Examination of different specimens of J. jiayinensis indicates that size and shape of fruits are related also with their maturity. Younger follicles are smaller, more elongated and more flattened, have longer style and less developed fibers. Mature fruits are bigger in length and diameter, sometimes sub-circular, with shorter style and more solid valves with better developed fibers. Similar maturation differences were documented for Joffrea speirsii inflorescences and infructescences (Crane, Stockey, 1985).

Follicle dehiscence varies from short apical split to separation of valves along one or both margins. In most species follicles dehisced only along the ventral suture. Some fruits from the Upper Tsagayan Formation and Reading Beds, however, split into two valves. Krassilov (1976) interpreted opening along both margins as usual way of dehiscence, but this splitting may be also result of drying or mechanical action during burial process. The majority of Jenkinsella fruits do not show any splitting. The follicles can also abscise from the joint at the base of the stalk. It seems, this way of dispersal played also an important role.

The number of follicles per pedicel varies from one to two. Only paired follicles are characteristic for J. jiayinensis. Other species have mainly single fruits. Ventral sutures of paired follicles are facing opposite each others (adaxial orientation). Majority of single fruits do not show clearly the orientation of ventral sutures with respect to the infructescence axis. Some fruits are evidently adaxial, but others are oriented in different directions. Some authors noted twisting of fruits stalks or side branches of infructescence, but others reported abaxial orientation of single follicles (Crane, Stockey, 1986; McIver, Basinger, 1993). Ventral sutures of young follicles are oriented usually adaxially (Feng at al., 2000). The similar patterns of follicles orientation were described for Joffrea speirsii (Crane, Stockey, 1985).

Crowding of follicles depends from length of side branches in infructescence, from length of fruit stalks and from distance between side branches. In J. krassilovii, J. vilyuensis and J. conferta side branches and pedicels are short and their infructescences are crowded. Species J. jiayinensis, J. knowltonii and J. gardnerii have long side branches and fruit stalks and follicles in their infructescences are widely spaced. The degree of crowding can also change with aging. Krassilov (1976) noted that elongation of raceme axis in J. krassilovii is probably continued during maturation and the racemes are gradually becoming looser. The same features are documented for inflorescences and infructescences of Joffrea (Crane, Stockey, 1985).

All species of Jenkinsella, that have racemes attached to the shoot, can be divided into two groups according to position of infructescences (Fig. 2): species bearing infructescences on long shoots and species bearing infructescences at short shoots. The first group consists of J. krassilovii, J. jiayinensis, J. knowltonii and J. vilyuensis. Second group includes J. conferta, J. gardnerii and J. makulbekovii.

Table 1

Comparison of different species oijenkinsella and Joffrea speirsii

Character Jenkinsella krassilovii Jenkinsella jiayinensis Jenkinsella gardnerii Jenkinsella knowltonii Jenkinsella conferta Jenkinsella makulbekovii Jenkinsella vilyuensis Joffrea speirsii

Reproductive shoots long long terminal short long lateral short lateral short long lateral short

Position of infructescence terminal from lateral (and possibly apical) flower buds terminal from lateral and apical flower buds terminal from lateral and apical flower buds terminal from lateral and apical flower buds terminal from apical flower buds terminal from apical flower buds terminal from lateral flower buds axillary ?

Length of infructescence (mm) 50-100 40-70 more than 50 35-50 15-30 55 20-25 more than 137 mm

Arrangement of fruits in infructescence crowded widely spaced widely spaced widely spaced crowded widely spaced closely spaced widely spaced

Follicle number per infructescence 8-14 14-22 about 15 5-7 15-20 9 more than 20 about 40

Number follicles on stalk mainly paired paired mainly single single mainly single single single ? mainly single

Length of follicles (mm) 15-30 14-28 20-25 10-16 5-7 12-15 5-6 18-30

Diameter of follicles (mm) 7-12 4-7.5 6-8 4-6 2-3 3-4 3-3,5 5-10

Distribution Amur Region, Russia Heilongjiang Province, China England Colorado, LISA Western Siberia Mongolia Eastern Siberia Alberta, Canada

Stratigraphie range Paleocene Paleocene Paleocene Paleocene Coniacian-Santonian Paleocene Turonian-Coniacian Paleocene

The species J. krassilovii has long reproductive shoots bearing several lateral racemes. Krassilov (1973, 1976) considered this structure as a panicle and each raceme as a side branch of a large paniculate infructes-cence. He noted that there are no definite leaf scars, and the side branches diverge at regular intervals and angles. Crane and Stockey (1986) interpreted remains of J. krassilovii as leafy twigs, bearing racemose in-fructescences. They supposed that there was a leaf scar where each raceme is attached to the long shoot, and that infructescence developed in the axil of leaf.

Our reexamination of specimens from Krassilov's collection has shown, that there are really no definite leaf scars near the base of infructescences, but there are marked junctions, corresponding to bud rings (annual growth rings). These characters suggest that infructescences were racemose and developed from lateral flower buds without leaves. During maturing the axis of infructescence thickened and probably crushed leaf scar of the preceding season, so it became hardly detectable. In that case each raceme should be considered as terminal infructescence, not as an axillary one.

Many genera of arboreal plants with large infructescences (for example, Populus, Acer and Fraxinus) display similar way of inflorescences arrangement (pl. V). The apical bud usually produces a new leafy long shoot. In J. krassilovii the upper part of long fertile shoot is badly preserved and position of upper infructescence is unclear (apical or lateral). Possibly, it might have leafy twig at the end of reproductive shoot (Fig. 2a). But two fertile shoots ofJ. jiayinensis ended by terminal infructescence, which was developed from apical bud (Fig. 2c). The holotype specimen of J. knowltonii demonstrates the upper part of a long shoot with one apical and one lateral infructescences. The reproductive structures of J. vilyuensis are represented by middle parts of long shoots with several lateral infructescences. So we have no information about construction of their apical parts. The best preserved specimen demonstrates the definite leaf scar near the base of one infructescence axis. It is triangular, about 3 mm wide and 2 mm long with three bundle scars.

Production of infructescences from the apical bud terminates the growth of shoot. Because the long shoots of Jenkinsella with infructescences usually shed as a unit, it is possibly to suggest that most part of them had apical infructescence.

The fertile shoots of J. gardnerii exhibit a particular case, being intermediate between short and long. The terminal, completely preserved, fertile short shoot of the holotype is about 13 mm long and bears only

Fig. 2. Schematic reconstruction of fertile shoots of different species ofJenkinsella (a-d) andJoffrea speirsii (f): a — long shoot with alternate lateral infructescences in terminal position and vegetative shoot developing from apical bud (J. krassilovii); b — long shoot with alternate short shoots, bearing singly infructescences in terminal position (J. conferta and J. makulbekovii); c — long shoot with alternate lateral and one apical infructescences (J. jiayinensis, J. knowltonii and J. vilyuensis); d — terminal short shoot with one lateral and one apical infructescences (J. gardnerii); f — long shoot with alternate short shoots, bearing three alternate lateral infructescences (Joffrea speirsii).

two infructescences: lateral and apical (Fig. 2d). Along swollen joints in the base and near the top of this shoot (between upper fertile shoot and previous one and between apical part of fertile shoot and apical inflorescence axis) there are rows of oval scars about 1 — 1,5 mm long that were interpreted earlier as whorl of leaf scars (Chandler, 1961; Crane, Stockey, 1986). We think that these scars are too small for leaves, and more likely they might correspond to bundle scars of leaves or bud scales. Bud rings at the base of racemes, corresponding in size to leaf scars, are in 3—4 times bigger. Because the arrangement of racemes is alternate, most likely, that arrangement of leaves also was alternate, rather than opposite or whorled.

The axes of infructescences of all species have no leaves in their lower part. But in J. jiayinensis some axes of racemes have small transverse ridges in the base (Feng et al., 2000, fig. 7), that may be interpreted as bud scale scars or small basal bracts scars.

In J. conferta and J. makulbekovii reproductive structures were differentiated into long and short shoots (Fig. 2b). Short shoots were alternate and bore several (4—6) leaf scars and solitary terminal infructescences at their apexes. Such features as insignificant length of short shoots, few leaf scars, lenticels at long shoots, small difference between long and short shoots diameters, and shedding reproductive structures as a unit suggest that age of short shoots was no more than one—two years.

The reproductive structures ofJ. conferta resemble that in Joffrea speirsii. This plant also exhibits long and short shoot differentiation. General construction of the racemose infructescences in both species is also similar. However, short shoots of J. conferta bore one terminal infructescence, while short shoots of Joffrea speirsii had at least two infructescences. The best-preserved specimen shows also one additional axis at the apex of the short shoot that was interpreted as a leaf petiole (Crane, Stockey, 1985), although it also may be considered as remains of a third infructescence. In whole, Joffrea was reconstructed as having monopodial short shoots with decussate foliage leaves and with two axillary infructescences (Crane, Stockey, 1985). However this interpretation is not the only possibility. Alternate arrangement of short shoots is in contradiction with reconstructed decussate phyllotaxy of these shoots. Shoots with infructescences did not show such arrangements of scars. Besides that, there is no evidence of axillary position of infructescences and the presence of leaves at the apex of fertile shoots. Reconstruction of inflorescence in axillary position contradicts to suggested anemophily of Joffrea. Flowers and leaves of wind pollinated plants usually develop in different time.

It may be suggested also that two or three alternate infructescences developed in the upper part of the short shoot from lateral flower buds of previous year (or from one terminal and two lateral buds), similarly as in Jenkinsella (Fig. 2f). One more bud without infructescence can be noted in the middle part of reproductive short shoot (Crane, Stocky, 1985, fig. 1). In this case differences between J. conferta and Joffrea speirsii lie only in the number of buds on the short shoots. However, precise arrangement of infructescences on the short shoot of Joffrea has remained obscure. The investigation of additional well-preserved specimens is necessary for confirmation one or another interpretation.

The main distinguishing features between different species of Jenkinsella are position of infructescences on either short or on long shoots, but systematic value of this character can not be completely understood and estimated yet, because majority of species are represented by limited number of specimens. For example, modern representatives of genus Populus show both long and short fertile shoots at one tree (pl. V). They also have short terminal shoots as J. gardnerii (pl. V, fig. 2). But apical buds of Populus produce usually vegetative long or short leafy shoots and development of fertile shoots does not terminate the growth of branch (pl. V, fig. 1, 2). Other genera of Salicaceae, for example, Salix, always have infructescences only on long shoots.

STRATIGRAPHIC AND GEOGRAPHIC DISTRIBUTION

The fossil records of Jenkinsella range from the early-middle Albian to the Oligocene and occur mostly in temperate and subtropical areas of the Northern Hemisphere. J. filatovii represents the earliest occurrence of this genus. These infructescences are associated with small leaves Trochodendroidespotomacensis (Ward) Bell. This species was widely distributed in the lower-middle Albian deposits of Siberia, Northeastern Russia and North America (Golovneva, Alekseev, 2010).

Two species were documented from the Late Cretaceous. Remains of J. vilyuensis were found in the Turonian-Coniacian deposits of the Timmerdyakh Formation, Eastern Siberia. Second species J. conferta from the Coniacian-Santonian deposits of the Sym Formation, Western Siberia, is slightly younger. Other remains of Jenkinsella come from the Paleocene deposits of North America, Northeastern Russia, Mongolia and China.

ACKNOWLEDGEMENTS The study was supported by the Russian Foundation for Basic Research (project No. 16-04-01411). The authors thank S. Manchester for courteously providing the images of J. knowltonii type specimen picture, an opportunity to work with Jenkinsella apocynoides material on loan from Natural History Museum, London and for helpful comments during the preparation of the manuscript.

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PLATE I

1—5, 11 — Nyssidium ekmanii Heer, Spitsbergen, the Barenzburg (Firkanten) Formation, the Paleocene: 1, 2 — lectotype, spec. S050342 (2 — drawing from Heer, 1876, pl. 14, fig. 6); 3 — spec. S50333 (=N. fusiforme Heer); 4 — spec. S50324 (=N. crassum Heer); 5 — spec. S50321 (=N. ekmanii Heer);

11 — spec. S50329 (=N. oblongum Heer).

6—8 — Jenkinsellafilatovii (Samylina) Golovneva et P. Alekseev, Northeastern Russia, the Kolyma River basin, the Omsukchan Formation, early-middle Albian: 6 — raceme infructescence, spec. BIN 510/5; 7 — holotype, spec. BIN 511/24; 8 — spec. BIN 510/6.

9 — Jenkinsella knowltonii Golovneva et P. Alekseev, sp. nov., USA, Colorado, the Dawson arkose, the

Paleocene, spec. USNM 37720, holotype.

10 — Jenkinsella apocynoides Reid and Chandler, southern England, the London Clay Formation, the

early Eocene, spec. V.30482-2 and V.30482-1. 12, 13 — Jenkinsella arctica (Heer) Bell, West Greenland, the Atanekerdluk Formation, the Paleocene:

12 — lectotype, drawing from Heer, 1869, pl. 43, fig. 12c, under name Nyssa arctica Heer; 13 — drawing from Heer, 1869, pl. 50, fig. 6.

Scale bar 1 cm in fig. 1—6, 9—11, 1 mm in fig. 7, 8, 5 mm in fig 12, 13.

PLATE II

1—7 — Jenkinsella krassilovii Golovneva et P. Alekseev, sp. nov., Russia, Amur Region, Bureya River basin, the Upper Tsagayan Formation, the Paleocene: 1 — infructescence, spec. IBSS 563/411; 2, 5 — follicles in pair, spec. BIN 1589/2 (former number IBSS 563/180 in Krassilov, 1976), 2 — enlarged view; 3 — long shoot with infructescence, spec. BIN 1589/1; 4 — the same specimens, attachment of raceme to the shoot, enlarged view; 6, 7 — holotype, spec. IBSS 563/221: 6 — joint in the place, where raceme is attached to the long shoot, enlarged view; 7 — long shoot with infructescences.

Scale bar 0,5 cm.

PLATE III

1—5, 7 — Jenkinsella conferta P. Alekseev et Golovneva, sp. nov., Western Siberia, Kiya River basin, the Sym Formation, the Coniacian-Santonian: 1 — twig with infructescence, spec. BIN 1564/144, holotype; 2 — detached infructescences spec. BIN 1564/156; 3 — infructescence, spec. BIN 1564/140; 4 — spec. BIN 1564/200, cast of follicle; 5, 7 — spec. BIN 1564/138: 5 — twig with several infructes-cences; 7 — infrectescence on the short shoot.

6 — Trochodendroides sibirica (Tcherepnin) P. Alekseev, Western Siberia, Kiya River basin, the Sym Formation, the Coniacian-Santonian, leaves associated with Jenkinsella conferta reproductive shoots, spec. BIN 1564/118.

Scale bar 0,5 cm.

PLATE IV

1 — Jenkinsella makulbekovii Golovneva et P. Alekseev, sp. nov., Mongolia, Southern Gobi, the Naran-Bulak Formation, the Paleocene, short shoot with infructescence, spec. PIN 3957/10-6, holotype.

2—4 —Jenkinsella vilyuensis Golovneva et P. Alekseev, sp. nov., Eastern Siberia, the Vilyui River basin, the Timmerdyakh Formation, the Turonian-Coniacian: 2, 4 — spec. BIN 1185/577: 2 — long shoot with infructescences; 4 — leaf scar near place of raceme attachment, enlarged view; 3 — long shoot with infructescences, spec. BIN 1185/578, holotype.

Scale bar 1 cm.

PLATE V

Structure of fertile shoots in genus Populus.

1 — one-year lateral short shoot with two inflorescences, Populus nigra L.

2 — terminal short shoot with several inflorescences, Populus nigra L.

3 — inflorescences on ultimate long shoot, Populus tremula L.

4 — multiyear lateral short shoots with three inflorescences, Populus tremula L.