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Zlatkocarpus
gen. nov., a new angiosperm reproductive structure with
monocolpate-reticulate pollen from the Late Cretaceous (Cenomanian) of
the Czech Republic
JiŘÍ KvaČeka; Else Marie Friisb
a The National Museum, Prague, Czech Republic b The Swedish Museum of Natural History,
Stockholm, Sweden
Online publication date: 18 May 2010
To cite this Article KvaČek, JiŘÍ and Friis, Else Marie(2010) '
Zlatkocarpus
gen. nov., a new angiosperm reproductive
structure with monocolpate-reticulate pollen from the Late Cretaceous (Cenomanian) of the Czech Republic', Grana, 49:
2, 115 — 127
To link to this Article: DOI: 10.1080/00173134.2010.481845
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ISSN 0017-3134 print/ISSN 1651-2049 online © 2010 Collegium Palynologicum Scandinavicum
DOI: 10.1080/00173134.2010.481845
Grana, 2010; 49: 115–127
SGRA
Zlatkocarpus gen. nov., a new angiosperm reproductive structure
with monocolpate-reticulate pollen from the Late Cretaceous
(Cenomanian) of the Czech Republic
Zlatkocarpus, a new Cretaceous angiosperm
JIRÍ KVACEK1 & ELSE MARIE FRIIS2
1The National Museum, Prague, Czech Republic, 2The Swedish Museum of Natural History, Stockholm, Sweden
Abstract
A new genus, Zlatkocarpus gen. nov., is described from the Peruc Korycany Formation (Cenomanian) of the Bohemian
Cretaceous Basin in the Czech Republic based on inflorescence axis, fruits and pollen. Two species are assigned to the new
genus, Zlatkocarpus brnikianus and Z. pragensis. Zlatkocarpus has a compound inflorescence consisting of primary axes bearing
semi-decussately arranged spikes. Each spike has helically arranged unicarpellate and unilocular fruits. Each fruit appar-
ently contains a single, orthotropous seed. The stigma is indistinct and sessile at the apex. The fruit wall has distinct globular
protrusions (probable resin bodies). The fruits are supported at the base by a small floral cup and a bract. Pollen grains
adhering to stigmatic areas and also on other surfaces of the fossil are monocolpate with a long colpus and an open reticulum.
The pollen is similar to dispersed pollen broadly referred to the extinct pollen genus Retimonocolpites, but none of dispersed
pollen genera are suitable for accommodating the fossils described here.
Keywords: basal angiosperms, Chloranthaceae, fossil flowers, inflorescences, infructescences, mesofossils, Myricanthium,
Zlatkocarpus, Retimonocolpites
The Peruc-Korycany Formation from the Bohemian
Cretaceous is rich in angiosperm remains and the
flora, sometimes referred to as the Peruc Flora, is
one of the classical leaf floras that has greatly influ-
enced early ideas on the Cretaceous radiation of
angiosperms. The first major studies of the flora
were those of Velenovský (e.g., 1882, 1883, 1884,
1885a, 1885b, 1889). In more recent years, the flora
has been studied by Zlatko and Jirí Kvacek (e.g.,
Kvacek, Z., 1992; Kvacek, J., 1995, 1998, 1999;
Kvacek & Knobloch, 1997; Kvacek & Eklund,
2003) with the description of many new taxa and
revisions of previously described taxa. Currently,
more than 120 species of angiosperms have been
identified. The fossils are mainly preserved as impres-
sions and compressions in consolidated sediments
and in rare cases show reproductive organs attached
to leafy stems (Velenovský, 1889; Velenovský &
Viniklár, 1926, 1927, 1929, 1931; Kvacek, Z., 1992).
Recently, three-dimensionally preserved mesofossils
were discovered in the Peruc-Korycany Formation.
Combined studies of mesofossils and macrofossils
provide an excellent opportunity to assemble more
complete reconstructions of inflorescence structure
in mid-Cretaceous angiosperms and the plants that
produced the reproductive organs (Eklund &
Kvacek, 1998; Kvacek, J., 2000; Kvacek & Eklund,
2003; Kvacek et al., 2005). These reproductive
structures are small and borne in elongated inflores-
cences/infructescences and include species such as
Mauldinia bohemica Eklund and J. Kvacek (Lau-
raceae), Pragocladus lauroides J. Kvacek and Eklund
(Lauraceae) and several species of Myricanthium.
Myricanthium was first compared to extant members
of Myricaceae (Velenovský, 1889). New studies
show, however, that it is probably not related to
Myricaceae or other eudicots, and that fossils
assigned to the genus are heterogeneous with some
Correspondence: Jirí Kvacek, Department of Palaeontology, National Museum, Václavské nám. 68, 115 79, Praha 1, Prague, Czech Republic.
E-mail: jiri_kvacek@nm.cz
(Received 3 June 2009; accepted 21 March 2010)
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116 J. Kvacek and E. M. FriisJ. Kva M. Friis
species perhaps related to Chloranthaceae (Kvacek
& Eklund, 2003). The heterogeneity of Myricanthium
is also supported by the present study. Unfortu-
nately, the type material for Myricanthium is poorly
preserved, but reinvestigation of M. pragense J. Kvacek
& Eklund shows that it is distinct from the type
material of Myricanthium (type species M. amenta-
ceum Velenovský) and we have therefore included
the species in a new genus, Zlatkocarpus (Z. pra-
gensis). In addition to this species, we have also
recognised another similar species that is here
described as a new species, i.e. Z. brnikensis.
Materials and methods
The fossil plants described here were isolated from
sandy mudstone collected in the clay pit near the village
Brník, 60 km east of Prague (49° 58′ 59″ N, 14° 54′ 56″
E – Zlatkocarpus brnikensis) and Hloubetín-Hute, north-
east suburb of Prague (50° 06′ 34″ N, 14° 33′ 20″ E
– Z. pragensis) within the Peruc-Korycany Formation
of the Bohemian Cretaceous Basin (sensu Cech et al.,
1980). Palynological data show a late mid-Cenomanian
age for the formation (Pacltová, 1977, 1978).
The Brník section is interpreted as a deep palaeo-
valley filled with fluvial sandstones and mudstones.
It consists of two major parts. The basal part
consists of fine granulated sands and claystones and
represents fluvial sediments of a meandering river
and floodplains. The upper part consists of sand-
stones interpreted as sediments of incised valley fill
of a braided river (Ulicný in Nguyen Tu et al.,
2002). Fossil plants are recorded in the lower part,
which consists of claystone bodies of various thick-
nesses. The fossil bearing claystone is also a resource
for mining. Currently, a number of fern, conifer and
angiosperm leaves have been recorded including
Gleichenia spp., cf. Anemia fremontii Knowlton,
Pagiophyllum sp., lauralean foliage “Eucalyptus”
angusta Velenovský, “Aralia” formosa Velenovský,
Dicotylophyllum velenovskyi Knobloch, Liriodendropsis
simplex (Newberry) Newberry, and others. Sandstones
of the upper part are usually barren or contain only
poorly preserved leaf impressions.
The material from Prague, Hloubetín-Hute
(Kvacek, J., 1992a, 1992b), was described for the
first time by Kvacek and Eklund (2003). It was
collected from a temporary excavation for the base-
ment of Hotel Pramen in Prague. Unfortunately, the
section was not documented sedimentologically.
Currently, 27 taxa have been recorded including
various ferns assigned to Gleichenia spp., conifers
assigned to “Sequoia” heterophylla Velenovský,
Quasisequoia crispa (Velenovský) J. Kvacek, Geinitzia
sp., Brachyphyllum sp., several angiosperm leaf taxa
including Grevilleophyllum constans (Velenovský)
Velenovský, “Eucalyptus” angusta Velenovský and
Cocculophyllum cinnamomeum (Velenovský) Velenovský,
Proteophyllum araliopsis Velenovský & Viniklár,
P. productum Velenovský & Viniklár, P. minutum
Velenovský & Viniklár, angiosperm reproductive
structures (Mauldinia bohemica, Pragocladus lauroides
J. Kvacek & Eklund) and several unnamed reproduc-
tive structures (see Kvacek & Eklund, 2003).
Specimens were extracted from the mudstone by
bulk maceration and treated through standard
techniques as described in Eklund and Kvacek
(1998). The material was preliminary examined
using Wild and Olympus binocular microscopes.
More detailed examinations were done using a
scanning electron microscope (Phillips 515 and
Hitachi S-4300). All specimens and preparations are
deposited in the palaeobotanical collections of the
National Museum, Prague (NMP).
Systematic palaeontology
Genus Zlatkocarpus gen. nov.
Derivation of generic name. – After Zlatko Kvacek in
recognition of his contribution to our understanding
of the Cretaceous and Tertiary vegetation of the
Bohemian Massif.
Generic diagnosis. – Flowers sessile, aggregated in
spikes; each flower supported by a persistent bract
arranged helically along an elongated axis. Flowers
apparently unisexual. Pistillate flowers consisting of
a single carpel surrounded by a floral cup. Stigmatic
area sessile, indistinct. Fruit: a one-seeded berry.
Fruit wall parenchymatous with resin bodies embed-
ded in the tissue under the epidermis. Pollen adher-
ing to the surface of fruits of Retimonocolpites-type,
monocolpate, reticulate-columellate with smooth
muri.
Type species. – Zlatkocarpus brnikensis sp. nov.
Other species. – Zlatkocarpus pragensis (J. Kvacek &
Eklund) comb. nov.
씮
Figure 1. Zlatkocarpus brnikensis sp. nov. A. Larger fragment of secondary axis with helically arranged fruits, holotype, F 3143. B–E. Details o
f
the holotype: B. Fruit with well pronounced perianth; C. Stigmatic area with adhering pollen; D. Attachments of fruits to secondary axis, note
perianth and small bracts; E. Detail of fruits with well pronounced resin bodies. Scale bars – 1.5 mm (A); 600 μm (B, D, E); 30 μm (C).
Downloaded At: 13:57 31 January 2011
Zlatkocarpus, a new Cretaceous angiosperm 117
Downloaded At: 13:57 31 January 2011
118 J. Kvacek and E. M. FriisJ. Kva M. Friis
Figure 2. Zlatkocarpus brnikensis sp. nov. A–D. Detached fruits: A. With periant in basal part, F 3145; B. With perianth in basal part,
opposite side of (A); C. Fruit from holotype, F 3143; D. With perianth in basal part, F 3147. Scale bars – 600 μm (C); 400 μm (A, B, D).
Downloaded At: 13:57 31 January 2011
Zlatkocarpus, a new Cretaceous angiosperm 119
Zlatkocarpus brnikensis sp. nov.
(Figures 1–3)
Derivation of specific epithet. – From the Brník local-
ity, where the fossil was discovered.
Specific diagnosis. – Floral cup large, encircling
the basal part of fruit for about one third of the
total length of the fruit. Fruits elliptical in outline
with slightly pointed apex and base. Pollen with
heterogeneous reticulum and distinct colpus margin.
Holotype designated here. – NMP F 3143; illustrated
here in Figures 1–3.
Paratypes designated here. – NMP F 3144–F 3147.
Type locality. – Clay pit near the village of Brník, 60
km east of Prague, Czech Republic (49° 58′ 59″ N,
14° 54′ 56″ E).
Type horizon and age. – Peruc Member, Peruc-Kory-
cany Formation, Cenomanian, Late Cretaceous.
Description. – All specimens are pistillate, preserved
in the fruiting stage. The most informative specimen
(the holotype, F 3143) is a fragment of a spike, about
6.5 mm long and 2.5 mm wide. It has about 50 fruits
borne in a helical arrangement (Figures 1–3). The
inflorescence axis is about 0.6 mm wide and charac-
terised by transversely aligned wrinkles. Fruits are
densely spaced and born in the axils of small triangu-
lar bracts, spaced at a distance of 0.5–1 mm, each
with a long free tip about 0.12–0.15 mm long. The
other specimens (F 3144–F 3147) are isolated fruits.
Each fruit is encircled by a floral cup, about 0.3–
0.6 mm long (Figures 1A, B, 2A–D). The floral cup
is broadly triangular in abaxial view. In adaxial view it
has an irregular outline with one or two additional
tips (Figure 2B, D). The floral cup is closely adhering
to the fruit and apparently fused to the fruit wall at
least at the base. Epidermal cells are isodiametric,
about 16–25 μm in diameter, and irregularly
arranged. No stomata or trichomes were observed.
The nature of the floral cup is unclear, although its
position suggests that it is a perianth.
Fruits are elliptical in outline with slightly pointed
apex and base, about 0.8–1.2 mm long and 0.45–0.7
mm wide (Figures 1A, B, D, E, 2A–D). The stigmatic
area is sessile and non-protruding, seen as a circular
area of indistinct cells about 0.8–0.1 mm in diameter
(Figure 1B, C, E). The surface of the fruit is irregu-
larly bulging from densely spaced resin bodies embed-
ded in the fruit wall under the epidermis (Figure 1A).
The epidermis consists of distinct, almost isodiamet-
ric, irregularly arranged epidermal cells, about 10–25
μm × 20–50 μm, with convex outer periclinal walls
(Figure 2A, B). The fruits are interpreted as unicar-
pellate. The single seed is apparently orthotropous.
Pollen occurs abundantly on the surface of the
fruits, typically close to the stigmatic area and near
the margin of the floral cup (Figure 1C). Grains
are monocolpate and coarsely reticulate, circular
to broadly elliptical in equatorial outline, with an
equatorial diameter of about 12–18 μm (Figure
3A–F). The colpus is straight and does not reach
the equator. Typically, the grains are folded in the
colpus area and the margin is usually hidden (Fig-
ure 3A, B), but a single specimen shows a distinct
colpus margin (Figure 3D). The reticulum is het-
erogeneous; smaller lumina are about 0.05–0.2 μm
in diameter and larger lumina are up to about 0.4–
0.8 μm in diameter (Figure 3E). Muri are narrow
and low with a flattened to rounded and smooth
profile, about 0.2–3 μm wide; columellae are irreg-
ularly spaced, about 0.3 μm long. Columellae and
reticulum easily detach from the foot layer (Figure
3C, D).
Zlatkocarpus pragensis (J. Kvacek & Eklund) comb.
nov. – (Figures 4–6)
Basionym. – Myricantheum pragense (Kvacek & Eklund,
2003, p. 1025, figures 4, 5).
Emended diagnosis. – As in Kvacek and Eklund (2003)
with the following addition: Floral cup short, about
one fourth of the total length of the fruit, most pro-
nounced adaxially. Pollen with almost homogeneous
reticulum.
Holotype. – NMP F 2892 (see Kvacek & Eklund,
2003).
Material. – NMP F 2893, F 2895–F 2898, F 3148–
F 3155, F 3461–F 3565.
Type locality. – Hloubetín-Hute, north-eastern suburb
of Prague, Czech Republic (50° 06′ 34″ N, 14° 33′
20″ E).
Type horizon and age. – Peruc Member, Peruc-Kory-
cany Formation, Cenomanian, Late Cretaceous.
Description and comments. – The type material (holo-
type and paratypes) originally ascribed to Myri-
cantheum pragense by Kvacek and Eklund (2003)
includes remnants of compound inflorescence/
infructescence axes (Figure 4H) as well as isolated
secondary axes (spikelets) with or without attached
floral organs (Figure 4A–C). The spikelets with the
attached floral units and the empty inflorescences/
infructescence fragments are assigned to the same
species based on the characteristic secondary bracts
and rare remnants of fruits in the empty inflores-
cences/infructescence. Additional material includes
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120 J. Kvacek and E. M. FriisJ. Kva M. Friis
Downloaded At: 13:57 31 January 2011
Zlatkocarpus, a new Cretaceous angiosperm 121
axes with a various number of fruitlets attached (F
2547, F 3148, F 3149, F 3151, F 3152, F 3461).
Pollen attached to the stigma surface (Figure 5A,
D, E) is monocolpate and coarsely reticulate, circular
to ellipsoidal in equatorial outline, with an equato-
rial diameter of about 8–10 μm. The reticulum is
almost homogeneous with only a few smaller lumina
(Figure 6A–D). Larger lumina are about 0.1–0.3 μm
in diameter. Muri are narrow and low with slightly
triangular and smooth profile, about 1 μm wide
(Figure 6D). Columellae are about 0.3 μm long and
widely spaced.
Zlatkocarpus pragensis is in general structure very
similar to Z. brnikensis, but the inflorescence/infruct-
escences are more completely preserved showing a
compound organisation with lateral spikelets
arranged in a semi-decussate to helical arrangement
along the main axis (Figure 4H). Zlatkocarpus pragensis
differs mainly by its much smaller floral cup that is
also much more pronounced at the abaxial side than
on the adaxial side (Figure 4G). Fruits are broadly
elliptical to almost circular in outline with an almost
smooth surface and with a thick cuticle (Figure 4D, G).
The stigmatic area is sessile and circular similar to
that in Z. brnikensis.
Discussion
Recognition of the new genus
Zlatkocarpus is based on structurally preserved inflo-
rescence/infructescence axes with attached floral/
fruiting units and adhering monocolpate pollen with
a semitectate-reticulate pollen wall. Muri of the
reticulum are smooth without supratectal ornamen-
tation. Similar dispersed pollen grains are typically
assigned to the pollen genus Retimonocolpites. The
current use of this dispersed pollen genus is very
broad and taxa included in Retimonocolpites clearly
represent a heterogeneous assemblages of lineages with
some species probably related to monocototyledons
and others perhaps related to various basal lineages
of angiosperms (Friis et al., 2010).
Comparison of Zlatkocarpus with extant plants
indicates that this fossil may represent an extinct
lineage of basal angiosperms. It shows some similarity
with Chloranthaceae, but the fossil inflorescences
have distinct helical phyllotaxis in contrast to the
prevailing decussate phyllotaxis of Chloranthaceae.
However, pollen very similar to that of Zlatkocarpus
has been found in unequivocal Araceae (Friis et al.,
2010) and affinity of Zlatkocarpus with early diverging
monocots cannot be excluded.
Fossil inflorescences/infructescences similar in
gross morphology to the fossils described here are
known from several other Early and mid-Cretaceous
floras. They are particularly similar to a variety of
inflorescences/infructescences from the Peruc
flora of the Bohemian Basin generally assigned to
the extinct genus Myricanthium. The type species,
M. amentaceum, was established by Velenovský
(1889) based on compression/impression material
that lacks details on supporting organs or flowers.
Later studies have identified structurally preserved
material together with the compression/impression
fossils that clearly demonstrates that Myricanthium-
like fossils from the Bohemian Cretaceous include a
diverse and heterogeneous complex of plants
(Kvacek, Z., 1992; Eklund & Kvacek, 1998; Kvacek
& Eklund, 2003). Currently, three species have been
distinguished. Mauldinia bohemica and Pragocladus lau-
roides both have bisexual and trimerous flowers and
were assigned to the Laurales (Eklund & Kvacek,
1998; Kvacek & Eklund, 2003). Myricanthium pragense
was described for fossils with unisexual and simple
flowers and was tentatively compared with extant
Chloranthaceae (Kvacek & Eklund, 2003).
Because of the poor preservation of the type material
of Myricanthium amentaceum it is unknown whether
this species had unisexual or bisexual flowers and
detailed comparison with the structurally preserved
fossils is not possible. We therefore suggest that the
genus Myricanthium is reserved for inflorescences/
infructescences for which details of floral units and
supporting organs are uncertain and exclude M.
pragense from the genus. Instead a new genus, Zlatko-
carpus, is established for organically preserved inflo-
rescences/infructescences bearing densely packed,
simple floral units supported by small bracts borne hel-
ically along an elongated axis as described here, includ-
ing Z. brnikensis as a new species and Z. pragensis
transferred from Myricanthium. In Z. pragensis, the
spikes are clearly secondary axes from a compound
spike. The secondary axes are borne in a semi-decussate
to helical arrangement. Although the inflorescences of Z.
brnikensis are more fragmentary preserved, the similarity
to Z. pragensis suggests that Z. brnikensis also had
compound inflorescences. Each floral unit con-
sists of a single ovary/fruit encircled by a floral
cup. In Z. brnikensis, the floral cup completely
씯
Figure 3. Zlatkocarpus brnikensis sp. nov. A–F. Pollen grains of Retimonocolpites type: A. Group of pollen grains, holotype, F 3143;
B. Pollen with colpus, F 3147; C. Group of pollen grains, two of them with partly detached reticulum, F 3146; D. Pollen with
colpus and partly detached reticulum, F 3147; E. Detail of exine with heterogenous columellae and smooth muri, holotype, F 3143;
F. Pollen adhering on stigma, holotype, F 3143. Scale bars – 30 μm (A); 12 μm (C); 6 μm (B, D, F); 1.2 μm (E).
Downloaded At: 13:57 31 January 2011
122 J. Kvacek and E. M. FriisJ. Kva M. Friis
Downloaded At: 13:57 31 January 2011
Zlatkocarpus, a new Cretaceous angiosperm 123
encircles the ovary/fruit and is fused to the ovary
wall for most of its length. The most straightforward
interpretation of this structure is that it represents a
perianth of several fused parts that are marked on the
cupule margin as extending tips. A complication in this
interpretation is, however, that the floral cup is more
bract-like in Z. pragensis and does not completely
encircle the ovary/fruit as it does in Z. brnikensis. An
interpretation of the floral cup as a supporting bract
rather than a perianth would imply the floral unit
represents a condensed tertiary axis of a com-
pound inflorescence with small naked flowers.
The spherical bodies, probably resin bodies, pre-
served in the ovary wall and other tissues may be
remains of ethereal oil cells.
We have interpreted the fossil flowers and inflo-
rescences as unisexual and pistillate. Most of the
specimens appear to be preserved in a post-anthetic
stage and the possibility that stamens have been shed
from an originally bisexual flower without leaving any
traces cannot be excluded. However, this alternative
is less likely. None of the specimens has any remains
of filaments or scars from detached stamens. In addi-
tion, the floral cup is fused to the ovary wall for most of
its length in Zlatkocarpus brnikensis and shows no
vascularisation or other evidence for the presence of
stamens.
The individual ovaries/fruits of Zlatkocarpus are
very similar to those of Couperites mauldinensis
Pedersen, Crane, Drinnan & Friis from the Ceno-
manian Mauldin Mountain flora of Maryland,
USA (Pedersen et al., 1991) and Couperites sp.
from the early or mid-Albian Puddledock flora of
Virginia, USA (Friis et al., 1997). In both genera,
fruits are apparently berries with a single seed and
the fruit wall is characterised by abundant resin
bodies embedded in the parenchyma tissue below
the epidermis. Both also have a sessile stigma and
monocolpate reticulate pollen, but ovaries/fruits of
Couperites are distinct in having an elongate,
slightly decurrent stigmatic ridge. Pollen grains
have supratectal ornamentation of minute spines.
Seed structure is well-known for Couperites, anatro-
pous and pendant, while it is less clear, but appar-
ently orthotropous in Zlatkocarpus. Fruits of
Couperites are always found isolated and there is no
information on inflorescences structure for this
fossil.
Comparison with dispersed pollen taxa
Pollen grains broadly similar to those observed on
the stigmatic areas of Zlatkocarpus pragense and Z.
brnikensis are common in dispersed palynological
assemblages from the Early and mid-Cretaceous.
This kind of dispersed grains is typically assigned to
the form genus Retimonocolpites or sometimes to Lili-
acidites. Both genera have been used in a very broad
sense and include a diverse and heterogeneous
assemblage of pollen types that are probably system-
atically widely separated.
The type species for Retimonocolpites, R. dividuus
Pierce, was first described from the Cenomanian of
Minnesota, USA, by using light microscopy (LM)
alone. Thus, no details of micromorphology or
ultrastructure were described or illustrated (Pierce,
1961). The presence of a distinct aperture almost
encircling the grain and dividing it into two halves as
well as a reticulum that occasionally separates from
the main body of the grain were mentioned as defining
characters for the species (Pierce, 1961). Other
features that are probably of systematic importance
such as presence or absence of supratectal ornamenta-
tion and ultrastructure of the pollen wall are
unknown. A study of pollen assigned to R. dividuus
from the Early Cretaceous (Late Albian) of Delaware,
USA, using LM, scanning electron microscopy
(SEM) and transmission electron microscopy
(Walker & Walker, 1984), showed distinct striate
ornamentation of the muri, but that pollen has a
long, extended colpus and may not be identical to
the type.
The type species for Liliacidites, L. kaitangataensis
Couper, was first described from the Late Cretaceous
and Early Tertiary of New Zealand (Couper, 1953).
It is monocolpate, characterised by a distinctly
graded reticulum and muri with beaded supratectal
ornamentation. Liliacidites has often been used as a
repository for other kinds of reticulate pollen, including
grains with a non-graded reticulum and smooth muri.
One of these described by Walker and Walker (1984)
from the Middle-Late Albian of Maryland, USA as
“Liliacidites” minutus (=Clavatipollenites minutus Brenner)
is similar to the grains of Zlatkocarpus pragensis, but the
reticulum in Z. pragensis is denser and number of small
lumen is higher.
The pollen grains observed on the surfaces of
Zlatkocarpus have smooth muri and shorter colpi
씯
Figure 4. Zlatkocarpus pragensis (J. Kvacek & Eklund) comb. nov. A. Basal and medial parts of secondary axis with helically arranged
fruits, holotype, F 2892. B. Apical part of empty secondary axis with bracts, F 3155. C–E. Fragments of secondary axis showing
arrangement of fruits and supporting bracts, F 3154: C. Overview; D. Fruit with its bract and perianth; E. Bract and perianth. F. Details
of empty bracts, detail of (B). G. Isolated fruit with well preserved perianth bearing conspicuous epidermal structure, F 3150. H. Basal
part of primary axis with one secondary axis still attached, F 2894. Scale bars – 5 mm (H); 500 μm (A); 400 μm (B); 300 μm (C, F); 200 μm
(E, G); 150 μm (D).
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124 J. Kvacek and E. M. FriisJ. Kva M. Friis
than in Retimonocolpites dividuus and the Bohemian
pollen is clearly distinct from the type species of
Retimonocolpites. Other pollen grains assigned to
Retimonocolpites that have been studied using SEM are
distinguished from the pollen of Zlatkocarpus by differ-
ences in lumen size and shape, length of columellae, or
Figure 5. Zlatkocarpus pragensis (J. Kvacek & Eklund) comb. nov. A–E. Details of the holotype, F 2892 (see Figure 4A): A. Detail of stigma
with adhering pollen; B. Fruit with resin bodies; C. Basal part of secondary axis with attached fruits; D. Retimonocolpites pollen adhering on
stigma; E. Retimonocolpites pollen adhering near to stigma, with elongate outline. Scale bars – 1 mm (C); 400 μm (B); 30 μm (A); 6 μm (D, E).
Downloaded At: 13:57 31 January 2011
Zlatkocarpus, a new Cretaceous angiosperm 125
presence of supratectal ornamentation. Pollen grains
closely similar to those of Zlatkocarpus have also
been found in situ in stamens borne in distinct aroid
inflorescences (Friis et al., 2010).
Systematic position of Zlatkocarpus
The character combination in Zlatkocarpus is
unusual and based on the data currently available, it
is not possible to place the fossils in a modern family
or order. Monocolpate, reticulate pollen is restricted
to non-eudicot angiosperms. The presence of a
heterogeneous reticulum with smaller and larger
lumina in monocolpate pollen has been suggested as
a defining feature for monocotyledons (Walker &
Walker, 1984), and very similar pollen has been
observed in situ in undisputable Araceae flowers
from the Early Cretaceous of Portugal (Friis et al.,
2010). However, if the resin bodies embedded in the
Zlatkocarpus fruit wall represent ethereal oil cells,
affinities with monocotyledons are unlikely. In
monocots, only Acorus has ethereal oil cells, but
Acorus is distinguished from Zlatkocarpus by its
bisexual flowers, much denser arrangement of the
flowers in the inflorescence, and the tectate-perforate
pollen wall. Among other non-eudicot angiosperms
several corresponding features occur in members of
the Chloranthaceae. Ascarina and Hedyosmum have
unisexual flowers borne in compound spikes and
typically are supported by bracts. Flowers are either
naked or have an epigynous, trimerous perianth that
is fused to the ovary for most of its length and only
free at the top of the gynoecium like in the pistillate
flowers of Hedyosmum.
If our interpretation of the floral cup in Zlatokocarpus
as a perigynous perianth is correct, it is comparable
to the perianth of Hedyosmum. The gynoecium in
Chloranthaceae consists of a single carpel with a
Figure 6. Zlatkocarpus pragensis (J. Kvacek & Eklund) comb. nov. A–D. Retimonocolpites pollen, details of F 3155 (Figure 4B): A. Pollen
with colpus, adhering on empty secondary axis; B. Pollen with colpus, adhering on empty secondary axis; C. Pollen with nearly homogenous
reticulum, adhering on empty secondary axis; D. Detail of exine with columellae and smooth muri. Scale bars – 6 μm (A–C); 1.2 μm (D).
Downloaded At: 13:57 31 January 2011
126 J. Kvacek and E. M. FriisJ. Kva M. Friis
single orthotropous ovule. The stigma is sessile.
The phyllotaxis of Chloranthaceae is mostly oppo-
site and decussate, while in Zlatkocarpus only the
secondary spikes are borne in a semi-decussate
arrangement, but floral units are borne in a heli-
cally arrangement. Pollen grains in Chloran-
thaceae are monocolpate-trichotomocolpate in
Ascarina, while the other genera of the family have
more unusual aperture configurations. All have
reticulate pollen grains. Grains with smooth muri
are known in Sarcandra and Chloranthus, but none
of these have monocolpate pollen, while Hedyos-
mum and Ascarina have muri with distinct suprate-
ctal ornamentation.
Simple, unisexual flowers borne in spikes are also
known for some extant members of the Piperales,
but pollen in Piperales is tectate with a continuous,
non-reticulate tectum. Inflorescences in Piperales
are mostly simple spikes, but an exception was
described for the perianthless. Peperomia fraseri
C.DC. has numerous spikes borne along a raceme
(Remizova et al., 2005); it is, however, clearly
distinct from Zlatkocarpus by having bisexual flow-
ers proximally and pistillate flowers distally in the
spikes, a high degree of polymorphism in the struc-
ture of bracts in the same inflorescence, and much
denser secondary branching (Remizova et al.,
2005).
Conclusion
The two new species of Zlatkocarpus described here
add further diversity to the complex of Myrican-
thium-like inflorescences. The organisation of the
inflorescence and flowers is in line with that of many
other Early and mid-Cretaceous angiosperms: flow-
ers are small, often unisexual with few floral parts
and arranged in dense inflorescences. Although the
radiation of eudicot angiosperms was well under way
in the Cenomanian, the diversity of non-eudicot
angiosperms was still much higher in the Cenoma-
nian than later in the Cretaceous and today, and
includes a considerable extinct component. Zlatko-
carpus with its monocolpate pollen clearly belongs to
this non-eudicot component of Cretaceous floras.
The precise systematic placement of Zlatkocarpus is,
however, unclear. Features of the pollen grains may
suggest affinity with monocotyledons, but organisa-
tion of the flowers and fruit does not allow an unam-
biguous phylogenetic assignment. In flower and fruit
characters, the fossils show particular similarity to
some Chloranthaceae, but Zlatkocarpus is distin-
guished from Chloranthaceae by the spiral phyllo-
taxis of the spikes, and the pollen grains differ in
several respects from those of Chloranthaceae.
Acknowledgements
We thank H. Eklund and Y. Arremo, Stockholm, for
help with SEM photographs of Zlatkocarpus pragensis.
This work was supported by SYNTHESYS (SE-
TAF-1153), the Academy of Sciences of the Czech
Republic (grant no. IAA 304070701), the Ministry
of Culture of the Czech Republic (grant no. MK
00002327201), and the Swedish Natural Science
Research Council.
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