5GEODIVERSITAS 2004 26 (1) Publications Scientifiques du Musum national dHistoire naturelle, Paris. www.geodiversitas.com
A minute mid-Cretaceous flower from Siberia and implications for the problem of basal angiosperms
Valentin A. KRASSILOVInstitute of Evolution, University of Haifa,
Mount Carmel, Haifa, 31905 (Israel)and Palaeontological Institute, 123 Profsojusnaya,
Moscow 117647 (Russia)email@example.com
Lena B. GOLOVNEVABotanical Institute, 2 Popova, St. Petersburg (Russia)
Krassilov V. A. & Golovneva L. B. 2004. A minute mid-Cretaceous flower from Siberiaand implications for the problem of basal angiosperms. Geodiversitas 26 (1) : 5-15.
ABSTRACTA new taxon of fossil angiosperms, Callicrypta chlamydea n. gen., n. sp., isestablished for a minute pistillate flower less than 2 mm wide from the mid-Cretaceous (Cenomanian) of East Siberia. It is preserved as compression,showing under SEM a calyx of six sepals, a biserrate corolla and an apocar-pous gynoecium. Pollen grains adhering to the perianth are like in Freyantha,a staminate flower from contemporaneous deposits. These floral structuresare compared with the Amborellaceae and Menispermaceae suggesting a pos-sible link between these families, with implications for the current concept ofbasal angiosperms.
RSUMDcouverte dune petite fleur dans le Crtac moyen de Sibrie et ses implicationsdans le problme des angiospermes basaux. Un nouveau taxon dangiosperme fossile, Callicrypta chlamydea n. gen., n. sp.,du Crtac moyen de Sibrie orientale, est dcrit. Le matriel qui lui est rap-port se compose dune petite fleur carpellaire de moins de 2 mm de largeur.Lexamen au SEM montre un calice six spales, une double corolle et ungynce apocarpe. Des grains de pollen sont galement conservs et associs la fleur carpellaire, une disposition qui est dj connue chez Freyantha. Cesfleurs sont compares avec celles des Amborellaceae et des Menispermaceae,elles partagent certaines caractristiques qui indiqueraient une parentpossible avec ces familles. Le concept dangiosperme basal est discut.
KEY WORDS Plant morphology,
flower, basal angiosperms,
ranunculids, pollination ecology,
Siberia, new genus,
MOTS CLSMorphologie vgtale,
fleur, angiospermes basaux,
ranunculides, cologie de la pollinisation,
Sibrie, nouveau genre,
We describe a new fossil flower that is the smallestof the hitherto found, yet showing a high degree ofmorphological accomplishment of its miniatureparts and having a certain bearing on the problemof basal angiosperms (Mathews & Donoghue1999; Qiu et al. 1999; Sampson 2000; Endress2001; Hesse 2001). This find supports our earlierview that small size and dicliny are primitivewhereas large perfect flowers are derived (Krassilov1984, 1997). It contributes to a diversity of earlyranunculids comprising forms related to the pres-ent-day Ranunculaceae, Menispermaceae,Sargentodoxaceae and even Paeoniaceae as a linkto the Dilleniales, hence fairly differentiated in themid-Cretaceous already (Vakhrameev & Krassilov1979; Krassilov et al. 1983; Krassilov 1984;Krassilov & Golovneva 2001).
MATERIAL AND METHODS
The material was obtained by bulk macerationof a slab from the plant-bearing clay horizon inthe lower part of Timerdyakhskaya Formation(Cenomanian) in the middle reaches of theTyung River about 200 km upstream of itsconfluence with the Vilyuy River, easternSiberia. The locality has been described inVakhrameev (1958) and the recent finds ofhamamelid remains are reported in Maslova &Golovneva (2000). The flower was picked fromamong the mesofossil debris, cleaned from theremaining rock matrix with hydrofluoric acid,cleansed in distilled water, photographed withstereomicroscope, mounted on SEM stub andcoated with gold. No parts were removed. Thepollen grains sticking to the perianth andcarpels were noticed when scanning the flowerwith CAMSCAN.
The flower is preserved as a compression withparts radially spreading in four overlapping
whorls (Figs 1A; 2). It appears somewhat zygo-morphic, the longer axis 1.8 mm, shorter axis1.4 mm. However the original symmetrymight have been distorted by a slightly obliquecompression. Hence the flower is describedlater on as actinomorphic or slightly zygomor-phic. The receptacle is not preserved, leaving ahole 0.4 mm wide in the center. Since it israther large in comparison with the carpels itmight have been expanded with divergence ofthe latter. The flower shows three cycles of perianth and anincomplete apocarpous gynoecium inside. Theoutermost perianth members are thin membran-ous sepals, apparently in a single whorl of six, ofwhich five are preserved and the sixth one (bot-tom right in Fig. 1) is required by the symmetry.They are c. 0.6 mm long, elliptical, apicallysmoothly rounded, flat, apparently brittle, with aconspicuous epidermis cell pattern.The next perianth cycle is turned about 25clockwise against the calyx, its members alternat-ing with the sepals and readily distinguishable bybeing shorter, 0.55 mm long, thicker, ovate inoutline, proximally concave, with involute mar-gins and narrow blunt apex. They are slightlyimbricate basally, but apparently distinct(Figs 1C; 2).The innermost perianth segments are clasped bythe outer petals, although they appear slightlydisplaced clockwise (Fig. 1C). The inner petalsare considerably smaller than the outer ones,0.35-0.40 mm long, membranous, roundedovate, flat or only slightly concave, notched at theapex. A better preserved inner petal shows apapillate body at the apical notch that can be anectary (Fig. 1E). The body is thick with distinctborders, of irregular outline, 87 m long, coveredwith dense relatively large hollow papillae that areelongate, apically depressed, leaving ellipticalscars when detached.One of the outer petals (bottom left in Fig. 1A)clasps a tubular appendage 0.24 mm long,0.08 mm thick that appears as a filament of astaminode the distal part of which is squashed(Fig. 1D). Two pollen grains were found stick-ing among the fragments of the distal part,
Krassilov V. A. & Golovneva L. B.
6 GEODIVERSITAS 2004 26 (1)
A new mid-Cretaceous flower from Siberia
7GEODIVERSITAS 2004 26 (1)
FIG. 1. Callicrypta chlamydea n. gen., n. sp. from the Cenomanian of Vilyuy Basin, Siberia, SEM photographs; A, holotype, a pistil-late flower with a calyx, biseriate corolla, and apocarpous gynoecium (see Fig. 2 for interpretation); B, carpel with a short style, ab-axial aspect; C, radial sequence of sepal (S), outer petal (Po), inner petal (Pi) and carpel (C), the carpel is split in the median planeshowing the locule, the position of papillate gland on the inner petal is marked as n; D, tubular structure (staminode?) clasped atbase by the inner petal; E, papillate gland (nectary?) below the apical notch of an inner petal (see n); F, carpel, lateral view, stylemissing. Scale bars: A, 300 m; B, 120 m; C, 90 m; D, 40 m; E, 21 m; F, 70 m.
which can be a mere coincidence, although sta-minodes sometimes produce some amount ofsterile pollen.The carpels facing the observer are in a singlewhorl, widely separated, opposite to the innerpetals or only slightly displaced against them.A carpel in posterior view (Fig. 1B) is ovatewith a broad base, broadly rounded distally,0.4 mm long, with a single style 50 m long. Itshows a median keel and thin striation corres-ponding to longitudinal rows of large epi-dermal cells. The style is filled with a spongytissue, distally slightly expanded and notched,perhaps at the base of stigma that is not pre-served. A carpel in lateral view (Fig. 1F) isgibbose, with an apical notch where the stylewas broken off. It appears incompletely sealednear the apex, but this may be owing to lateralcompression. Still another carpel (Fig. 1C) issplit, showing a single locule. Ovules are notpreserved.
The surface of sepals appears granular owing tothe slightly bulging polygonal epidermal cells dis-posed in longitudinal files. The outer petals aresmooth, with a faint longitudinal striation overthe margins. The inner petals are marked by irre-gularly scattered rounded pits. The carpels areabaxially pubescent, with dense hair bases andoccasionally preserved unicellular hairs c. 10-15 mlong.The pollen grains found sticking to the petals andcarpels are all of the same morphotype, slightlyoblate, tricolpate, reticulate, equatorial aspectrounded-elliptical, polar aspect trilobate, withdeeply incised lobes, equatorial diameter 18-20 m, polar axis 16-18 m. The colpi are slit-like, slightly invaginate, long, nearly reaching thepoles. The surface reticulum is polygonal, scarce-ly differentiated on the colpi margins, with thickmuri and relatively narrow lumina of rounded,elliptical, triangular, elongate, arcuate or irregularshapes (Fig. 3).
Krassilov V. A. & Golovneva L. B.
8 GEODIVERSITAS 2004 26 (1)
FIG. 2. Callicrypta chlamydea n. gen., n. sp., a flower from the Cenomanian of Vilyuy Basin, Siberia, outline of the holotype (seeFig. 1A) showing interpretation of the floral parts. Abbreviations: C, carpel; Pi, inner petal; Po, outer petal; S, sepal; St , staminode?.Scale bar: 150 m.
Our material is fairly different from all hithertodescribed fossil flowers in combining very smallsize with dicliny, hexamerous structure, well dif-ferentiated perianth and apocarpous gynoeciumof many carpels. Most early (mid-Cretaceous)flowers are considerably larger, pentamerous withbracteate perianth of undifferentiated tepals andvariously c