Thrips pollination of Mesozoic gymnosperms
Enrique Peñalvera, Conrad C. Labandeirab,c,1, Eduardo Barróna, Xavier Delclòsd, Patricia Nele, André Nele,
Paul Tafforeauf, and Carmen Sorianof
a
Museo Geominero, Instituto Geológico y Minero de España, Madrid E-28003, Spain; bDepartment of Paleobiology, National Museum of Natural History,
Smithsonian Institution, Washington, DC 20013; cDepartment of Entomology and Behavior, Ecology, Evolution and Systematics Program, University of
Maryland, College Park, MD 20742; dDepartament d’Estratigrafia, Paleontologia i Geociències Marines, Facultat de Geologia, Universitat de Barcelona,
E-08071, Spain; eCentre National de la Recherche Scientifique Unité Mixte de Recherche 7205, Entomologie, Muséum National d’Histoire Naturelle,
Paris F-75005; Département Sciences de la Vie et Santé, AgroParisTech, Paris F-75231, France; and fEuropean Synchrotron Radiation Facility, Grenoble,
F-38000, France
Edited by David L. Dilcher, Indiana University, Bloomington, IN, and approved April 10, 2012 (received for review December 13, 2011)
paleoecology
| paleoethology | coevolution | plant–insect interactions
M
id-Mesozoic gymnosperms are a globally diverse assemblage
of seed plants of which only four lineages persist today. Of
these, about 600 species of conifers and the sole surviving ginkgophyte species, Ginkgo biloba, are obligately wind pollinated (1).
By contrast, many of the about 100 gnetophyte species and somewhat over 300 species of cycads are insect pollinated (2, 3). Recent
examination has documented the prominent, often obligate, insect
mutualisms occurring among these two, latter gymnosperm clades
(1–3) and the rarity of wind pollination (2, 4–6). For gnetophytes,
a broad spectrum of small-sized, inconspicuous insects are pollinators, especially flies, but also moths, beetles, small wasps, thrips,
and occasionally bees (2, 5, 6). Cycads are pollinated by equally
specialized but, overall, more taxonomically circumscribed beetle
lineages, especially weevils (3, 4), and a lineage of thrips (7–9).
Occasionally, both insect groups pollinate the same cycad species
(7, 8). Even so, Mesozoic evidence for insect pollination of gymnosperms has been sparse and indirect (1, 10–12), although the
remaining seed-plant group, angiosperms, has received considerable support for pollination during the Late Cretaceous and Cenozoic (1, 13–16). Here, we report on four female thrips found in
four pieces of Early Cretaceous (Albian) amber from Spain (SI
Text), bearing abundant gymnospermous pollen associated with
specialized body structures (Figs. 1 and 2). This unique gymnosperm–thrips association provides a distinctive pollination mode
during the mid-Mesozoic that includes a specialized structure for
collecting pollen, suggesting subsocial behavior and extending the
breadth of nonangiospermous pollination mutualisms.
Thrips are minute, diverse insects that feed on pollen grains,
plant tissues, fungi, and small arthropods (9, 17, 18), also known
for their stereotyped punch-and-suck feeding style for extracting
protoplasts from a variety of cell types and pollen grains (19).
Historically, discussion of thrips as pollinators has been controversial, because these minute insects do not fit the general profile
of an effective pollinator (9, 17, 18), although they now are
documented as pollinators of basal angiosperms (15, 20) and
eudicots such as dipterocarps (18). Individuals transport from
www.pnas.org/cgi/doi/10.1073/pnas.1120499109
several to a few hundred pollen grains to flowers (18) or cones
(Table S1); for example, Cycadothrips chadwicki can deliver up to
5,700 pollen grains per ovule to Macrozamia communis cycad
cones in an afternoon (8). Several species of Cycadothrips are efficient pollinators of endemic Australian Macrozamia cycads (7, 8,
21). Besides pollination of gnetaleans and cycads, thrips species
are collected from male cones of conifers and are implicated in
pollen feeding (22) but without effective pollination. No thrips or
other insect ever has been reported as transferring pollen to
modern, obligately wind-pollinated Ginkgo biloba (1).
Systematic Paleontology
The systematic paleontology is as follows: Insecta Linnaeus,
1758; Thysanoptera Haliday, 1836; Melanthripidae Bagnall, 1913;
Gymnopollisthrips Peñalver, Nel & Nel gen. nov.; Gymnopollisthrips minor Peñalver, Nel & Nel gen. et sp. nov. (type species of
genus, here designated); Gymnopollisthrips maior Peñalver, Nel &
Nel sp. nov.
Etymology. The generic name is a combination of Gymno, referring to the gymnosperm origin of the vectored grains (Greek);
pollis (Latin, meaning pollen); and thrips (Greek, meaning
“woodworm”), which is a common suffix for thysanopteran
genera and is of neutral gender. The specific epithets minor and
maior (Latin) mean smaller and larger in size, respectively.
Diagnosis (Females). Specialized setae with small seriate rings that
are regularly spaced along their length (ring setae) are distributed
in a bilaterally symmetrical manner on certain body regions.
Antennae are nine-segmented. Antennal segment II is asymmetrical with a small prolongation at the ventro-lateral apex.
Antennal segments III and IV each have one rounded and large
apical plate-like sensory area in lateral-external position. Antennal segments VI to IX are clearly distinct from each other.
The head has ocellar setae I arising on a conical tubercle. The
forewing is not falcate, but broad, slightly narrowed at the apex,
with two complete, main longitudinal veins and five crossveins;
the anterior fringe is short, and the posterior fringe is straight.
The apex of the abdomen is elongated, not rounded. Abdominal
Author contributions: E.P., C.C.L., E.B., and A.N. designed research; E.P., C.C.L., E.B., X.D.,
P.N., A.N., P.T., and C.S. performed research; P.T. and C.S. contributed new reagents/
analytic tools; E.P., C.C.L., E.B., X.D., P.N., and A.N. analyzed data; and C.C.L. wrote
the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
Data deposition: The data and procedures reported in this paper corresponding to the
scan parameters, reconstructed slices, 3D volume extraction, and resulting movie of the
holotype specimen of Gymnopollisthrips minor are available online at the Paleontological
Online Database of the European Synchrotron Radiation Facility, http://paleo.esrf.eu (amber inclusions and Spain sections).
1
To whom correspondence should be addressed. E-mail: [email protected].
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.
1073/pnas.1120499109/-/DCSupplemental.
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EVOLUTION
Within modern gymnosperms, conifers and Ginkgo are exclusively
wind pollinated whereas many gnetaleans and cycads are insect
pollinated. For cycads, thrips are specialized pollinators. We report
such a specialized pollination mode from Early Cretaceous amber of
Spain, wherein four female thrips representing a genus and two
species in the family Melanthripidae were covered by abundant
Cycadopites pollen grains. These females bear unique ring setae
interpreted as specialized structures for pollen grain collection,
functionally equivalent to the hook-tipped sensilla and plumose
setae on the bodies of bees. The most parsimonious explanation
for this structure is parental food provisioning for larvae, indicating subsociality. This association provides direct evidence of specialized collection and transportation of pollen grains and likely
gymnosperm pollination by 110–105 million years ago, possibly
considerably earlier.
A
5 mm
C
B
0.2 mm
1
5
2-4
E
2-4
20 µm
D
F
20 µm
G
100 µm
H
0.2 mm
0.1 mm
20 µm
J
200 µm
Fig. 1. Mesozoic pollinator association between a gymnosperm host plant and an insect
pollinator from the Early Cretaceous of Spain.
(A) Amber piece containing six specimens of
the thrips genus Gymnopollisthrips (Thysanoptera: Melanthripidae), five of which are
indicated by arrows (MCNA-9516). (B) Photographic image of G. minor with attached
Cycadopites-type pollen grains (holotype MCNA10731, intact female) in dorsal aspect. (C)
Photographic image of G. minor and associated pollen in ventral aspect (same scale as B).
(D) Camera lucida drawings of G. minor, based
on B and C above. Wings in ventral view have
been omitted for clarity; Cycadopites type
pollen grains are indicated in orange. (E)
Specialized ring setae of the distal forewing
of G. minor. (F) Magnified ring seta from E,
showing four rings. (G) Prominent ring seta of
the distal abdomen of G. minor, showing the
adherence of 12 clumped pollen grains of
Cycadopites. (H) Detail of mostly clumped
pollen grains from wing setae of G. minor. (I)
Enlargement of grains in a clump of pollen
attached to wing setae indicated in H at left.
(J) Detail of Cycadopites type pollen grains on
the dorsal surface of G. minor in B above.
segments IX and X have very long setae. Sclerotized ovipositor is
upwardly curved.
anterior longitudinal vein and ca. 16 setae on posterior longitudinal vein.
G. minor Peñalver, Nel & Nel gen. et sp. nov
See Figs. 1 B–D and H–J and 2I and Movie S1.
G. maior Peñalver, Nel & Nel sp. nov
See Fig. 2A and Figs. S1–S3.
Holotype. MCNA-10731 and paratype MCNA-9472, housed at the
Holotype. Specimen MCNA-9283, housed at the Museo de
Museo de Ciencias Naturales de Álava, Vitoria-Gasteiz, Spain, are
both complete females with pollen loads (ca. 140 and ca. 15 grains,
respectively). The holotype was imaged by synchrotron holotomography to better study the pollen distribution (Movie S1).
Ciencias Naturales de Álava, Vitoria–Gasteiz, Spain, is a complete female carrying ca. 137 pollen grains.
Locality and Age. The specimens were collected from the Albian
Peñacerrada I amber site, Escucha Formation, eastern area of
the Basque–Cantabrian Basin, northern Spain (SI Text).
Diagnosis. As for the genus, additional characteristics include the
following: plate-like sensory areas on antennal segments III and
IV are longitudinally elongated and cover approximately half of
the segment length. The pronotum is slightly rectangular, bearing two pairs of lateral setae. The forewing has ca. 18 setae on
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Locality and Age. Locality and age of G. maior are the same as
those of G. minor.
Diagnosis. G. maior differs from G. minor by less setose antennae,
strong setae on the dorsal side of the head, four pairs of lateral
setae on a subcircular pronotum, a forewing with ca. 24 setae on
anterior longitudinal vein and ca. 21 setae on posterior longitudinal vein, and plate-like sensory areas on antennal segments
III and IV covering a third of the segment length. The area on
segment III is longer than wide vs. wider than long on segment
IV. In addition, G. maior is larger by one-third.
Peñalver et al.
A
B
18
16
14
12
10
0
16
C
20
18
22
24
l
w
D
0.5 cm
20 µm
E
J
20 µm
F
20 µm
0.2 mm
G
H
50 µm
50 µm
Systematic Placement of the Genus
This genus (see SI Text for description of the subordinate species
and detailed systematic placement) is attributable to the Aeolothripidae–Melanthripidae–Merothripidae group of families,
supported by the wing venational synapomorphy: “capture of M
by RP and the formation of a combined RP+M” (23). Attribution to the family Melanthripidae is supported by the presence of
a projection in the anterior part of the vertex where ocellar setae
I are situated, as in the genus Ankothrips (24), one of the four
extant genera recognized within this family. Ankothrips also is
characterized by the apex of antennal segment II ventro-laterally
prolonged into a lobe, although this is weakly developed in some
specimens. This character is present in the fossils as a pronounced asymmetry of segment II with a more developed ventrolateral apex; however, it is shorter than in Ankothrips. Moreover,
extant Ankothrips species frequently bear enlargement of platePeñalver et al.
Fig. 2. Features of thrips and gymnosperm
remains. (A) Camera lucida drawings of Gymnopollisthrips maior and detail of antennae
showing the planated sensory structures on
segments III to IV (segment III plus IV 130 µm
in length); Cycadopites-type pollen grains are
indicated in orange (holotype MCNA-9283,
intact female). (B) Length (horizontal axis)
and width (vertical axis) measurements in
microns of pollen grains from G. minor (black
circle) and G. maior (white square). Measurement scheme is provided in C below; data are
available in Table S2. (C) Length (l) and width
(w) measurements taken on pollen grains
displayed in B above. (D) Two macerated
ovulate organs of cf Nehvizdyella sp. and leaf
of Eretmophyllum sp. from Spanish Albian
deposits of amber. (E) Pollen grain attached
to the base of a specialized ring seta of the
abdominal margin of G. minor. (F) The same
seta and pollen grain in E above but at
a lower focal level, showing pollen grain
margin attached to setal ring. (G) Pollen grain
attached to the base of an abdominal ring
seta. (H) Three abdominal ring setae, two
with attached pollen grains at their bases. (I)
Accumulation of ca. 150 Cycadopites-type
pollen grains adjacent to a thrips, possibly
attributable to falling pollen being concentrated in viscous resin. (J) Enlargement of
several grains from cluster at I. E–I are from
the holotype of G. minor.
like sensoria on antennal segments III and IV, which is not as
broad as in the fossils. Melanthripids appear phytophagous,
feeding and breeding within flowers, and the pattern of host
exploitation typically involves monophagy by most members (25).
The twelve species of Ankothrips are from western United States,
southwestern Africa, and Europe; monophagous host relationships seem to exist for some taxa, but one is common on Yucca
whipplei (Agavaceae), another one on Adenostema fasciculata
(Rosaceae) flowers, and the four European species are associated with the mature reproductive tissues of the conifers Juniperus and Cupressus (24).
Discussion
The female fossil specimens transported large quantities of
pollen grains, similar to extant species of Cycadothrips but considerably more than loads borne by most angiosperm-pollinating
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20 µm
0.1 mm
thrips (18) (Table S1). These data indicate that Gymnopollisthrips was an efficient transporter of pollen grains. The ability of
thrips to carry pollen grains would depend on the stickiness of
the grains (26) and the number and structure of their setae (18).
Gymnopollisthrips has abundant, long, specialized setae containing seriate rings as a distinctive structural feature (SI Text).
These setae are located only on external, protruding body parts
and wing apices, which often exhibit attached single and clusters
of pollen particularly at their bases (Fig. 2 E–H). We interpret
ring setae as a unique structural modification of Gymnopollisthrips to increase the scope of thrips for attachment of pollen
grains. That interpretation is based principally on their exclusive
location on external, protruding parts of the body, with the
higher surface area provided by the rings and the abundance and
clumped nature of captured pollen grains. Indeed, thrips ring
setae were a specialized structure for collecting pollen grains,
unknown in modern insect species. Accordingly, pollen grains
could be trapped passively or actively using stereotyped movements, although compelling evidence is not available. In addition, there are pollen grains concentrated on the dorsal or
ventral regions of the body (Figs. 1 B–D and H–J and 2A). This
distribution is consistent with initial attachment of pollen grains
along the setae, followed by active relocation using the legs for
better pollen transport that would prevent detachment during
flight (SI Text). Remaining pollen on ring setae would represent
less accessible grains and grain clumps.
Pollen grains associated with the thrips are monosulcate, psilate
in ornamentation, prolate to suboblate in shape, and minute in size
(average 20.4 μm long and 12.6 μm wide). Each grain shows acute
to rounded polar margins and generally an elongate-oval external
sulcus for the entire length of the grain. Often the sulcus is wider at
its ends and constricted toward the equatorial area where its
margins may overlap. The sulcus margin is simple but sometimes
folded. The exine is on average 1.3 μm thick. The pollen grains
belong to the gymnosperm form-genus Cycadopites and, in general, has a slightly smaller size than Jurassic and Cretaceous
specimens of the genus, such as C. follicularis, C. durhamensis, and
principally C. fragilis (SI Text).
Evidence strongly supports a ginkgoalean or possibly cycad as
the source of the Cycadopites pollen on Gymnopollisthrips. These
two affiliations are based mostly on: (i) macrofloral abundance
and the taphonomic context of Eretmophyllum (Fig. 2D) in relevant, Albian Spanish amber outcrops, indicating a ginkgoalean
assignment; and (ii) some pollen structural features that suggest
a cycadalean affinity (Fig. 2C and SI Text). Ginkgoaleans and
cycads are dioecious, having separate male and female organs,
often on different individuals.
Apart from the abundance of pollen grains of the same morphotype on thrips bodies and the presence of specialized setae (SI
Text), these grains show features consistent with insect pollination.
Stickiness, minute size, and clumping suggest an insect pollination
system based on correlates with extant insect-pollinated seed plants
(15, 26–28). These pollen features have been associated with insect
pollination in ancient angiosperms (16, 29). Intergrain stickiness
evidently caused the observed clumping, suggesting that a pollenkitt-like substance was present on the pollen surface, analogous to
some extant cycads, which are pollinated by both insects and aerial
transfer (28). Extant gymnosperms lack adhesive surface compounds or other clumping-induced structures (26), indicating that
modern gymnosperms may be poor analogs for the variety of reproductive modes during the Cretaceous (11). Nevertheless, several
basal lineages of Early Cretaceous angiosperms apparently were
pollinated by insects vectoring clumped pollen (15, 16, 29).
We infer that a Gymnopollisthrips–gymnosperm active pollination mutualism was present at Peñacerrada I, also based on
analogous, similar pollen grains occurring in several extant Cycadothrips–Macrozamia mutualisms from Australia, and on the small
size and the lack of Cycadopites in the amber-bearing sediment
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consistent with gymnospermous entomophilous pollen (7, 8).
Additionally, pollen grains identical in structure and size (Fig. 2 B
and C and Tables S2 and S3) were transported by both species of
Gymnopollisthrips, suggesting that these taxa were accessing the
same gymnosperm species or minimally the same host genus, implicating possible monophagy. The uniquely specialized ring setae
of female Gymnopollisthrips would have afforded better fitness for
the initial collection and secondary transport of pollen, evidently
functionally equivalent to the hook-tipped sensilla and plumose
setae on bee bodies (30) used by females to capture and vector
distant pollen grains for larval food provision.
The value of ring setae would have operated under multiple
selective regimes. The inferred active transportation of pollen
grains could be explained as parental food provisioning for larvae, which perhaps promoted subsocial colony formation (31).
The identified insect pollinator belongs to a distinct genus of the
family Melanthripidae, an extant clade of the order Thysanoptera. Modern thrips show varied behaviors that can include
parental care ranging from solitary to gregarious, colonial, subsocial, and eusocial habits, the last of which can exhibit morphologically and behaviorally specialized individuals into castes
(31–33). Scarce but direct evidence of parental care/eusociality
in insects has been reported only in Cenozoic ambers, principally
ants, but never in Cretaceous amber, possibly attributable to
preservational limitations. In contrast, these behaviors have been
widely inferred from structural proxy characters.
The hypothesized presence of subsocial behavior, reinforced by
parental care, has not been found in extant Melanthripidae. By
comparison, some modern thrips species are subsocial (31, 32)
whereas others, especially some Phlaeothripidae, are eusocial with
all life-stages congregating, such as in gall chambers (33). Although the microhabitat of Gymnopollisthrips larvae remain uncertain, sites amid host-plant interstices seem most reasonable.
Ginkgoalean pollen organs generally lack protection for larvae,
albeit their ovulate organs and associated vegetative structures
would provide concealed enclosures for larval development. A
pollination system in which there was transport of pollen by a female thrips that ended in larval feeding on an ovulate cone is more
consistent with a ginkgoalean rather than a cycad host, in which the
larvae would have fed directly on the male cones. In addition,
ovulate reproductive organs assigned to the form-genus Nehvizdyella (Fig. 2D), affiliated with Eretmophyllum foliage, are common in several Early Cretaceous Spanish amber deposits (SI Text).
This proposed system differs from recent Cycadothrips and Macrozamia mutualisms, including taxa inferred to have diversified
during the later Miocene (34). The differences include absence of
a specialized structure in Cycadothrips to attach pollen grains and
the pattern of adults and larvae inhabiting principally pollen cones
that eventually emit a strong, repugnant odor inducing individuals
to leave the male plant and visit the ovulate cone. This timed
“push” of pollen cones overlaps with the “pull” of ovulate cones
causing short-distance flights that result in pollination (21).
The Gymnopollisthrips–gymnosperm mutualism occurred toward the end of the third phase of the plant–insect associational
fossil record (1), established in the wake of the end Permian extinction and replaced by the mid-Cretaceous angiosperm ecological expansion (13). Our discovery shows that within this
interval, some thrips lineages may have been among the “primeval
pollinators” (9). This antiquity of thrips as pollinators (9) has been
based on recent cycad-pollinating Cycadothrips as a member of
a basal or otherwise early-appearing thysanopteran clade (35).
This issue merits further investigation for several reasons. Firstly,
the phylogeny of major thrips clades related to Cycadothrips
remains unresolved. Secondly, it may be premature to extend
phylogenetic inference (36, 37) from the biology of recent Cycadothrips (7, 8) to taxa of Mesozoic thrips (38–40). Current evidence indicates that Cycadothrips may have acquired plant
associational attributes with Macrozamia host species relatively
Peñalver et al.
of which currently are angiosperm pollinators (17, 18) (Table S3).
For earliest angiosperms, small insects such as thrips could have
been pollinators of small, inconspicuous flowers dominated by the
rewards of pollen and perhaps thermogenesis, volatile scents, but
avoiding nectarial secretions, oils, and resins (5, 13, 20). Although it
is uncertain whether additional seed plant–thrips associations
other than the gymnosperm–melanthripid association were established during the Mesozoic, it is evident that several, modern thysanopteran genera associated with angiosperms were present by
the Early Eocene (38). The ancient associations between gymnosperms and their insect pollinators were extinguished either
through loss of their plant hosts or exist today on cycads, possibly as
depauperate relicts. Our study also indicates that modern gymnosperms may be poor analogs for understanding the diversity of
pollination modes in their Mesozoic relatives.
Methods
The specimen preparation, photography, and synchrotron imaging procedure followed the following steps. Amber initially was screened for
inclusions, then embedded in a stable epoxide resin under vacuum, and finally ground and polished with a water-fed flat lap. Embedding stabilizes the
amber, preventing oxidation and permitting an accurate viewing of the
bioinclusion. Subsequently, photomicrography was performed with a digital
camera attached to a stereomicroscope (Olympus BX51). Later specimens
were drawn using a drawing tube Olympus U-DA attached to the stereomicroscope. One holotype specimen was imaged at the BM05 beamline of the
European Synchrotron Radiation Facility at Grenoble, using propagation
phase-contrast X-ray synchrotron microtomography. Procedure details are
provided in SI Text.
ACKNOWLEDGMENTS. We thank the staff of the Museo de Ciencias
Naturales de Álava in Spain for preparation, curation, and access to specimens. We thank Bernard Gomez from the University of Lyon-1 and Jose
Fig. 3. Hypothesis of thysanopteran–seed plant pollinator relationships, indicating the colonization of cycads, angiosperms, and probable ginkgoaleans. The
numbered fossil and modern occurrences of thrips taxa are as follows: 1, Cyphoneurodes patriciae; 2, Burmacypha longicornis; 3, Triassothrips virginicus; 4,
Kazachothrips triassicus; 5, Karataothrips jurassicus; 6, Cretothrips antiquus; 7, extant Cycadothrips chadwicki; 8, Gymnopollisthrips minor, G. maior; 9,
Tethysthrips libanicus; 10, Tethysthrips hispanicus; 11, several extant genera; 12, several occurrences in Lebanese amber; 13, Hispanothrips utrillensis; and 14,
Rohrthrips libanicus. References and additional data supporting the numbered thrips fossil and modern occurrences, thysanopteran phylogeny, and the
geological age of plant groups are provided in SI Text.
Peñalver et al.
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EVOLUTION
recently (34). Thirdly, the three extant species of Cycadothrips live
only on species of the Australian genus Macrozamia. A relationship between Macrozamia and the Lepidozamia–Encephalartos
sister clade would suggest a 200–135 Ma (largely Jurassic) age for
the “Macrozamia” lineage (41). The oldest documented fossils of
this cycad genus are from the Paleogene of Australia (42), suggesting a latter diversification and possibly a rather recent age for
Cycadothrips as well (34). Lastly, the abundance and diversity of
other cycad hosts, some representing ancient Mesozoic lineages,
lack pollinating thrips, consistent with a recent, Australian
origin for the Cycadothrips–Macrozamia association. These considerations indicate that major biological differences exist between
the gymnosperm–Gymnopollisthrips and the cycad–Cycadothrips
mutualisms, and ecologically uniformitarian extensions from the
recent to the Mesozoic are premature.
Nevertheless, the Thysanoptera is a likely ancient group of
gymnosperm pollen feeders, indicated by the possible consumption
of Late Permian noeggeranthialean spores by representatives of
the stem-group Thripida (43) and subsequent pollinator associations that evolved with two or three, major, seed-plant clades.
These associations are as follows: (i) between angiosperms and
principally thripids (plus possibly Melanthripidae on gymnosperms
and angiosperms) that presumably commenced during the Early
Cretaceous angiosperm radiation (15, 20); (ii) between modern
cycads and Cycadothrips (7, 8) that may have mid-Cretaceous
antecedents (38–40); and (iii) between Early Cretaceous ginkgoaleans or cycads and the fossil melanthripids reported herein
(Fig. 3). Circumstantial evidence for mid-Cretaceous angiosperm–
thrips associations includes early angiosperm floral structure consistent with thrips pollination (15, 18, 20), and the presence of the
earliest known Thripidae and Phlaeothripidae (40), many members
Baruchel and Tamzin Lafford from the European Synchrotron Radiation Facility for their help. Finnegan Marsh did the illustrations. We thank Peter
Cloetens, Jean-Claude Labiche, Alejandro Homs, Antonia Beteva, Alessandro
Mirone, and Max Langer from the European Synchrotron Radiation Facility
for assistance with the imaging and 3D reconstruction of specimens. E.P.
acknowledges European Union Synthesys Grant FR-TAF-5126 to study Cretaceous thrips. This study was supported by the Spanish Ministry of Economy
and Competitiveness project CGL2011-23948/BTE. This is contribution 174 of
the Evolution of Terrestrial Ecosystems consortium at the National Museum
of Natural History, in Washington, DC.
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Supporting Information
Peñalver et al. 10.1073/pnas.1120499109
SI Text
Historical Context of Gymnosperm–Thrips Pollination. Plant–insect
pollination mutualisms in certain cycad species consist of faithful
pollination by specialist thrips pollinators that consume hostplant items such as pollen and tissues. Interactive insect behaviors in this process often are mediated by chemical and physical
cues, such as volatile chemical emissions (1, 2) and cone thermogenesis (3), that serve in luring insects to their host plants.
Such insect-mediated pollination is more efficient than wind
pollination (4), and these pollinator mutualisms could be ancient
for some taxa (5–7), extending into the preangiospermous Mesozoic. The greater efficiency of insect over wind pollination
recently has been supported by the most basal and geochronologically earliest clade of cycads, the Cycadaceae, possessing various clades of beetle pollinators (1, 8–12), as well as
pollen laden coprolites occurring in Middle Triassic male cones
of a related taxon (13). Additionally, there are mid-Mesozoic
and earlier Permian occurrences of prepollen and pollen feeding
of seed plants by suspect Coleoptera and Thysanoptera (9, 14).
As in modern cycads, the fossil record indicates that extinct seedplant lineages previously considered fundamentally wind-pollinated also included taxa that display evidence consistent with
insect pollination (15, 16). The fossil evidence in support of midMesozoic seed-plant–insect associations and likely pollination
has included insect mouthpart structure (16, 17), partly consumed ovulate and pollen organs and associated tissues (13, 15),
ovulate organ structure (15, 16), external pollen features (18,
19), pollen associated with heads and mouthparts of suspect
insects (15, 20), and the extant biologies of relevant insects and
their gymnospermous hosts (9, 21–23). The current gymnosperm–thrips association adds to this repertoire of associations
and represents an additional instance of such an interaction
from amber.
Synchrotron Imaging Procedure. The holotype specimen of Gymnopollisthrips minor gen. et sp. nov. (Fig. 1 B and C) was imaged
at the BM05 beamline of the European Synchrotron Radiation
Facility at Grenoble, France, using propagation phase-contrast
X-ray synchrotron microtomography. This technique reveals
structural detail on samples lacking sufficient contrast for X-ray
absorption techniques (24–26). To facilitate the 3D processing of
the data, an algorithm for single-distance phase retrieval developed by Paganin et al. (27) was implemented. The algorithm
developed by Paganin et al. already has been successfully applied
for imaging on fossils (28) but, in the present case, was modified
because the sample to image profile did not fit conditions for the
application of such an algorithm.
The sample consisted of an amber piece embedded in epoxy
resin and glued on a cover glass. The geometry of the sample
clearly was not adapted for a single-phase retrieval process because of very strong absorption anisotropy during sample rotation. Because the insect structures were principally small in size,
all structures larger than 50 pixels were removed, subtracting to
each projection a copy of itself after a median filtering of 50 pixels.
This operation of subtraction led to complete normalization of
the background and optimization of the contrast of the insect
itself, using the Paganin phase retrieval. To compensate for the
blurring induced by the phase retrieval, a less-than-sharp mask
filter was applied on the radiographs after the phase retrieval.
Residual ring artifacts were corrected on the reconstructed slices
and the volume was converted into a 16-bit tagged image file
format (TIFF) stack file. The 3D images were manually rendered
Peñalver et al. www.pnas.org/cgi/content/short/1120499109
into a movie using a region-growing technique with VGStudiomax (version 2.1) software (Volume Graphics).
The scan was performed using a propagation distance of 24 mm
and beam energy of 20 keV, implemented by a double-crystal
multilayer monochromator. The movie consisted of 1,500 projections, each of which was acquired every 0.8 s over 180 degrees.
To obtain a sufficiently high resolution of the fine structures in
the specimen, a detector giving an isotropic voxel size of 0.75 µm
was used.
The scanned amber piece was translucent (Fig. 2I) and potentially of high scientific value; consequently, it would have
been risky to perform an elevated high-resolution scan. The
equipment setup and protocol mentioned above typically are
used for high-resolution scanning of opaque amber pieces (25,
27, 29). In the case of nonopaque amber, it is common to observe
strong darkening of the amber during synchrotron imaging. Although the darkening can later be removed using UV light exposure, it always is preferable to avoid the potentially damaging
effects of amber darkening and to reduce the dosage to an acceptable minimum level whenever possible, especially when
dealing with potential holotype material. Accordingly, a highefficiency and high-resolution detector was developed that would
reduce the X-ray dose by nearly a factor of 50. This lower dose,
compared with the much more elevated standard, produces
a comparable dynamic level in the data but requires scanning
times of approximately 1 h rather than a few minutes. As
a consequence of a dramatic reduction in total X-ray flux, and
the scanning time limited by the speed of the detector instead of
the X-ray flux, it appeared more reasonable to use the beam of
a bending magnet (BM05), instead of the far higher flux of an
undulator, such as the ID19 beamline (28, 29).
The detector apparatus consisted of a single optical element
from a 20× microscope objective with a 0.4-mm opening that was
coupled with a 9 μm lutetium oxyorthosilicate (LSO) scintillator
(29). The light was projected on a CCD FreLoN camera (30)
containing a new-generation CCD chip (E2V) with a 15-µm pixel
size, yielding five times greater efficiency than the Atmel chip
generally used for these type of experiments. The combination of
the LSO scintillator and a E2V FreLoN camera also allowed
higher efficiency, attributable to scintillator emission as green
light (550-nm emission ray), complimenting the maximum efficiency of the E2V CCD chip, compared with the red light (715
nm) of the usually used Gd3Ga5O12 (GGG) scintillators. The
principal drawbacks of this type of detector are: (i) a notably
slow readout time of 0.6 s per frame; (ii) distortion attributable
to the optical configuration that is corrected by retrodistortion of
the pictures; and (iii) a loss of about 200 pixels on the total field
of view compared with an optical system using both a 10× objective and a 2× eyepiece. Considering that the dose reduction
and the longer scans did not result in darkening of the amber
piece and the resulting data quality was similar to the alternative
rapid and high-dose setup, this modified system was preferable
for scanning by avoiding specimen damage. Because of adjustments to scan duration and dose intensity, some pollen grains
were not detected by our procedure and, thus, not imaged in the
resulting movie.
Geological Context. The Basque–Cantabrian Basin (BCB),
northern Spain, along with other Mesozoic basins of the Iberian
Peninsula, is associated with the opening of the northern part of
the Atlantic. During the Early Cretaceous, sedimentation of the
basin was dominated by sandstones, limestones, and marls that
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were deposited in shallow marine and freshwater environments.
During the lower–middle Albian, at the end of the rift stage,
deltaic and estuarine systems developed and evolved vertically
into a deltaic system dominated by a fluvial–deltaic environment
with siliciclastic input, represented by the Escucha Formation
(31). In general, the amber localities of the BCB are related to
paralic environments in the eastern region (Escucha Fm.), or
paralic–marine environments in the western region (Las Peñosas
Fm.) (32). Spanish Cretaceous amber is principally found in localities distributed in a curvilinear arc from the east to the north
along the Iberian Peninsula, which corresponds approximately to
the seashore during the Early Cretaceous (33).
Two main amber-bearing outcrops are found in the eastern
area of BCB: Moraza, also named Peñacerrada I in Burgos
Province and Peñacerrada II (32) in Álava Province. The amber
from both deposits is known as Álava amber (32). The palynological record suggests an Albian age (Early Cretaceous, ca. 110–
105 Ma) for associated Álava amber. In this area, the Escucha
Fm. is divided into three subunits that, overall, are represented
by a deltaic succession, with a vertical tendency to a regression of
the deltaic system in the lower–middle subunits and a vertical
transgression in the upper subunit (31). The lower subunit is
characterized by gray clays or heterolithic deposits with sparse
intercalations of carbonate sandstones with orbitolinids. The
middle subunit is dominated by sandstones and siliceous microconglomerates from channel fill and abundant coal beds. The
upper subunit consists of gray lutites with intercalations of carbonate sandstones containing marine orbitolinids and bivalves.
Amber is always associated with coal and lignitic beds or organically rich marl levels of the middle subunit, coinciding with
the boundary between the maximum regression and the beginning of the transgression. Amber-bearing strata typically are located within sedimentary deposits of the interdistributary deltaic
bays. One of these amber deposits occurs in Peñacerrada I amber, which has yielded the present thrips specimens and thousands of other arthropod inclusions (32–34).
Systematic Paleontology. Plants. Plant host affinities of the pollen. All
pollen grains adhering to the thrips bodies have the same shape,
minute size [average, 20.4 μm long (range, 17.4–24.9) and
12.6 μm wide (range, 9.3–15.4)] and sulcus and surface features
and, consequently, are assignable to the same pollen form genus.
The exine is 1.3 μm thick (range, 0.7–2.5 μm); some grains show
weak exines that could be incompletely developed, aborted
grains. Clusters of pollen grains occur principally in the holotype
of G. maior sp. nov., despite their occasional detachment from
thrips bodies that evidently occurred during initial resin immersion. These relationships indicate a physical or chemical
basis for intergrain adhesion.
The pollen morphology (Figs. 1 I and J and 2C) corresponds to
the gymnosperm form genus Cycadopites Wodehouse emend
Fensome (35). This genus is based on material described from
the Paleocene near Red Lodge, in Carbon County, southwestern
Montana (36, 37). In particular, the pollen grains are favorably
compared with Jurassic and Cretaceous specimens attributed to
C. follicularis Wilson and Webster (35, 38), and C. durhamensis
Cornet and Traverse (39), but most closely resemble C. fragilis
Singh from the Barremian–Aptian of the Congo Basin (40).
However, the Spanish and African forms are somewhat smaller
than the type specimens of C. fragilis (41). Cycadopites typically
occurs in Mesozoic pollen organs of the Cycadales, Bennettitales, Ginkgoales, Czekanowskiales, Peltaspermales, Pentoxylales, Gnetales (42), and Sanmiguelia, a Late Triassic seed plant
of uncertain relationships (43).
Of the diverse plant groups that produced Cycadopites-type
pollen, only ginkgoaleans, and possibly cycads, are present as
macrofloral remains throughout the amber-bearing outcrops of
the Spanish Albian (32, 44); specimens previously identified as
Peñalver et al. www.pnas.org/cgi/content/short/1120499109
Bennettitales were misinterpreted. In particular, the ginkgoalean
foliage genera Eretmophyllum [sensu Nehvizdya (44–47)] and
Pseudotorellia are two of the three dominant plants represented
(32, 44). It is the more abundant Eretmophyllum that was the
probable source of the Cycadopites pollen vectored by Gymnopollisthrips, based on pollen structure and taphonomic and paleoecologic evidence detailed below. Although the sole surviving
ginkgoalean species, Ginkgo biloba, is obligately wind pollinated
(15), this current condition is a poor analog toward inferring
pollination modes of diverse Mesozoic ginkgoalean taxa, such as
Eretmophyllum; wind pollination in recent G. biloba consequently is uninformative (15, 48). Many Mesozoic ginkgoaleans
produce pollen, in addition to extant G. biloba (Table S1), that
are greater in length than the grains associated with Gymnopollisthrips. These two, albeit subtle, features would provide
support for a cycad host hypothesis, consistent with the study by
Van Konijnenburg–Van Cittert (49) on older, Jurassic pollen
from Yorkshire, United Kingdom.
Only the smaller-sized, elliptic pollen grains from the pollen
organs of the Mesozoic cycads, Androstrobus wonnacotti Harris,
A. szei Harris, and A. balmei Hill (49, 50) and grains from the
pentoxylalean male cone Sahnia nipaensis Mittre (51) could be
affiliated with the clusters of Gymnopollisthrips pollen grains. In
most cases, these four, potentially affiliate fossil species are
variable in shape, ranging from spherical to elliptic. In addition,
the genera Androstrobus and Sahnia are absent from Spanish
Albian amber sites, including Peñacerrada I. Also, our thripsassociated pollen grains are morphologically similar to in situ
pollen grains of the Triassic cycad Delemaya spinulosa, associated with insect coprolites and suggesting insect pollination (13,
17). Cycads of the Zamiaceae, in particular Macrozamia lucida
(18) and M. macdonnellii (5), are the only extant, insect-pollinated clade with species that have pollen grains similar in size
and form to those on Gymnopollisthrips. Nevertheless zamiaceous cycads also are absent from Spanish Albian macroremains.
Comparisons between Gymnopollisthrips borne and similar pollen. In
Table S3, we compared structural features of Cycadopites grains
borne by Gymnopollisthrips with other Cycadopites grains from
major Mesozoic and extant seed-plant clades (49–55). In Table
S2, we measured the lengths and widths of 80 Cycadopites grains
lodged on the bodies of Gymnopollisthrips holotypes (40 from G.
minor and 40 from G. maior) to determine pollen conspecificity
and the possible presence of plant–host selectivity by each pollinator species (Fig. 2B).
Insects. Description of the holotype (MCNA-10731) of Gymnopollisthrips
minor gen. et sp. nov. The characteristics of the macropterous fe-
male are as follows: body length, 973 µm;. long and short specialized setae with regularly seriate small rings (ring setae) along
their length present on the head (anteroventral position), mesopleura, femora, abdomen (lateral and apical positions, almost
only on segments IX and X), and wings (distal fringe and distal
setae on longitudinal veins).
Head. The characteristics of the head are as follows (measurements are in microns): the head is poorly preserved in the dorsal
side (121 long; 152 wide), but an anterior projection of the vertex
is present, only one lateral ocellus is preserved, and only four
interocellar setae are visible; the ventral side of the head is
covered by transverse linear sculpture. The antenna is nine-segmented [total length, 333; segment lengths: segment I, 21; segment II, 45; segment III, 55; segment IV, 52; segment V, 58;
segment VI, 55; segment VII, 27; segment VIII, 24; segment IX,
30]; annulae and microtrichia are present on all antennal segments; planate (plate-like) sensory areas in lateroexternal position on segments III (24 long) and IV (28 long), both
longitudinally elongated and covering approximately half of the
segment length; segment I is short, segment II is asymmetrical
with a small prolongation at ventro-lateral apex, and segments II
to IX are elongate, cylindrical; segments VI to IX clearly distinct
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from each other; segment IX is longer than VIII with ca. seven
subdivisions. The mouthcone reaches the base of the prosternum;
maxillary palps are three-segmented, and labial palps are twosegmented.
Thorax. The characteristics of the thorax are as follows (measurements are in microns): pronotum transverse, 148 long and 194
wide, with the surface finely striate-reticulate; two pairs of long
posteroangular setae [76 long (longest)], two pairs of anteroangular setae, and two pairs of lateral setae; only four pairs of
posteromarginal setae visible (others being covered). The forewing is not falcate, 676 long and 82 wide at midlength, with
microtrichia on membrane; presence of two complete main
longitudinal veins, one crossvein between them slightly basal with
respect to half of the wing length plus two crossveins at 2/5 of the
wing length and other two slightly distal with respect to 3/5 of the
wing length, between longitudinal veins and wing margins; longitudinal veins bearing an uninterrupted row of long setae (18
setae in anterior vein and 15–17 in posterior one, up to 48 long).
Longitudinal veins ending 55 of wing apex. Anterior margin with
a row of setae and a row of short fringe cilia. Posterior fringe
straight and not very long (182 the longest). Hindwing narrow,
slightly narrowed at apex, not falcate, circa 645 long and 76 wide
at midlength, with one slightly sclerotized longitudinal vein
closer to the posterior wing margin, reaching the wing apex, with
microtrichia on membrane and with fringe not undulate (fringe
near the wing apex is 90 long). Mesonotal surface with transverse
linear sculpture. All coxae, femora and tibiae with fine transverse
sculpture. Foreleg 455 long (femur 182 long and 79 greatest
width, tibia 185 long and 39 greatest width, tarsus 58 long and
arolium 30 long); forefemur strongly incrassate with a row of
dorsal setae; tibia with two stout setae on ventral position [better
visible in the paratype (MCNA-9472)]; tarsus (90 long) without
a distal hamus. Midlegs are 348 long. Hindleg is 409 long; femur
with 2–3 dorsal, large setae; tibia with a row of dorsal setae
progressively longer toward distal position and two strong ventrodistal setae. Tarsi are two-segmented.
Abdomen. The characteristics of the abdomen are as follows
(measurements are in microns): abdomen with apex slender;
pleurites present; abdominal tergites with transverse linear
sculpture and sternites with reticulate sculpture. Abdominal
tergite X is obscure; trichobothria not observed; strong lateral
setae on segments I to VIII; segment IX with two or three pairs of
short and strong lateral setae; segment X with four pairs of long
and strong setae (specialized ring setae, see diagnosis and below)
and about 11 pairs of shorter setae as illustrated (Fig. 1D); longest
pair, 170 long, is close the basal part of the segment. The ovipositor is upwardly curved, ca. 300 long, with margin apparently
serrate and bearing a few lateral fine setae.
Description of the holotype (MCNA-9283) of Gymnopollisthrips maior
sp. nov. For the macropterous female (Fig. S1), the body length is
1,312 µm. Long specialized ring setae with regularly slightly
marked rings along their length are present on abdominal segments IX and X; a few ring setae, but shorter, are present on the
thorax and hind femur.
Head. Measurements are in microns. The head is quadrangular
(142 long; 142 wide); ocellar setae I arise on a conical tubercle
(Fig. S3), ocelli are not preserved; interocellar setae are strong
(39 long), and three pairs of strong postocular setae are present
(about 39 long); the ventral and dorsal sides of the head are
covered by transverse linear sculpture. The antenna is ninesegmented (total length, about 380; lengths of segments: II, 48;
III, 66; IV, 67; V, 49; VI, 46; VII, 34; VIII, 34; IX, 35); annulae
and microtrichia are present on all antennal segments; plate-like
sensory areas in lateroexternal position are present on segments
III (18 long; 23 wide) (Fig. S2) and IV (24 long, 18 wide); segment I is short, with two strong setae distally; segment II is
asymmetrical, with a small prolongation at ventro-lateral apex;
segments II to IX are elongate, cylindrical; segments VI to IX
Peñalver et al. www.pnas.org/cgi/content/short/1120499109
are clearly distinct from each other; segment IX has ca. seven
subdivisions (Fig. S3). The mouthcone reaches the base of the
prosternum; maxillary and labial palps are obscure.
Thorax. Measurements are in microns. The pronotum is nearly as
long as wide (176 in length; 185 width), with the surface apparently not striate–reticulate; two pairs of long posteroangular
setae [85 (longest) and 42 long, respectively], two pairs of anteroangular setae, and four pairs of lateral setae are present; seven
pairs of posteromarginal setae are present. The forewing is not
falcate (758 long and 118 wide at midlength), with microtrichia
on the membrane; two complete main longitudinal veins are
present, with one crossvein between them slightly basal with
respect to half of the wing length plus two crossveins at two-fifths
of the wing length and other two distal with respect to three-fifths
of the wing length, between longitudinal veins and wing margins;
longitudinal veins bear an uninterrupted row of long setae (about
24 setae on anterior vein and about 21 on posterior one, up to 45
long). Longitudinal veins end 75 of the wing apex. Clavus with
a row of five long setae (up to 39 long) and a discal seta is visible
on left forewing (30 long). Anterior margin with a row of setae
plus a short fringe is present. The posterior fringe is straight and
long (288 the longest). The hindwing is narrow, slightly narrowed
at apex, not falcate, ca. 642 long and 91 wide at midlength, with
one slightly sclerotized longitudinal vein closer to the posterior
wing margin, reaching the wing apex, with microtrichia on
membrane and with long fringe not undulate (182 the longest).
Mesonotal surface has transverse linear sculpture. Fine transverse sculpture on legs is only observed on coxae and hind
femora. Forefemur is incrassate (about 165 long and 103 greatest
wide), with a row of strong dorsal setae (about 15 setae); foretibia (about 175 long) has two stout setae on ventral position;
tarsus (90 long) and is without a distal hamus. Midfemur is 39
long, tibia is 160 long, and tarsus is 82 long. The greatest width of
hindfemur is 55, and bears with two strong dorsal setae; tibia
(252 long) has a row of dorsal setae progressively longer distally
and two strong ventrodistal setae; tarsus is 94 long. Tarsi are twosegmented.
Abdomen. The abdomen with apex is slender; pleurites are present; abdominal sternites have transverse linear sculpture; strong
lateral setae are present on segments I to VIII; segment IX has
three pairs of short and strong lateral setae and two large ventral
setae [88 µm (the longest)]; segment X has four pairs of long,
strong lateral setae, from which one pair is specialized ring setae
(see below), plus ca. nine pairs of shorter setae as illustrated
(Fig. 2A); the longest pair (182 µm long) is close to the basal part
of the segment. Tergite X is obscure, and the potential presence
of trichobothria is unclear. Ovipositor is upwardly curved, ca. 440
long, with margin apparently serrate and bearing a few lateral
fine setae.
Other specimens. Apart from the type specimens, described
above, an additional female was found with ca. 50 pollen grains
distributed ventrally, principally on her abdominal terminus.
This specimen (MCNA-9516) and an adjacent, additional incomplete specimen, both bearing antennal sensilla and specialized ring setae characteristic of the genus, occur in a small, dark
amber piece (Fig. 1A), which also contains four males. Because
of poor preservation and difficulty of observing characters, these
specimens remain identified as Gymnopollisthrips sp. Males lack
both special setae and attached pollen grains, and despite their
bad preservation, they can be identified as males by the presence
of prominent abdominal tergal spines. In addition, the amber
piece contains a group of ca. 70 isolated grains positioned at 2.5
mm from the female individual.
Family-level assignment of the thrips genus. These fossils are attributable to the Aeolothripidae–Melanthripidae–Merothripidae
group of families, supported by the synapomorphy “capture of M
by RP and the formation of a combined RP+M” (56). The inner
phylogeny of this clade remains unresolved, so the apomorphies
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that would support assignment to one of the three families are
not clearly defined. As indicated in the main text, an attribution to
the family Melanthripidae is supported by the presence of a projection in the anterior part of the vertex, with ocellar setae I situated apically, paralleling the melanthripid genus Ankothrips (57).
Ankothrips and Gymnopollisthrips also bear an asymmetry of segment II, although in a different conformation (as a ventro-lateral
prolongation at the apex). This is however smaller in the fossils
than the lobes in extant Ankothrips. The sensilla on antennal
segments III and IV of fossils are broader than in Ankothrips but of
about equivalent size to those observed in fossil Archankothrips
varicornis (58, 59), which possesses the characteristic lobes of
Ankothrips on the antennal segment II. As in Ankothrips, the fossils
present stout setae on the apex of the foretibia, a characteristic
also observable in Cranothrips (60) and Dorythrips, whereas in
Melanthrips, the fourth melanthripid genus, these setae are broad
spurs. Other characteristics are congruent with an attribution to
Melanthripidae, particularly the broad forewings (also present in
Aeolothripidae), the long setae on the pronotum (also present in
the merothripid genus Erotidothrips), the nine-segmented antenna
with segments VI to IX clearly distinct from each other and the
antennal segment IX as long as or longer than segment VIII (also
present in the aeolothripid genera Cycadothrips and Dactuliothrips,
and in the merothripid genus Erotidothrips), the disposition of the
setae on antennal segments II and III (which excludes the Aeolothripidae), and broad planate sensilla (this characteristic is also
present in some Aeolothripidae and Merothripidae). Nevertheless, the Cretaceous specimens have a set of remarkable characteristics that preclude them to belong to a recent genus.
Insufficient preservation of the abdomens in all fossil specimens
prevents us to elucidate the presence and morphology of both
trichobothria on tergite X and on the lobes of sternite VII, characteristics present in both Melanthripidae and Merothripidae. In
conclusion, we attribute these fossils to the family Melanthripidae
and await a better resolution of the phylogeny of the three
aforementioned families.
We note that the paratype of Gymnopollisthrips minor (MCNA9472) has forewings with 17 setae on the anterior longitudinal vein
and about 15 setae on posterior longitudinal vein (vs. 18 and 15–
17 in the holotype). These features are best visible in the paratype,
rather than the holotype of this species, in which the forefemur is
strongly incrassate (227 µm in length; 106 µm in greatest width).
Apart from the diagnostic characteristics discussed in the main
text, G. maior differs from G. minor in having slightly more
pronounced linear sculpture on the body, more abundant and
robust setae on head and thorax, and two distal crossveins of the
forewing that are more distally located.
Ring setae. The torus-like rings that form the distinctive
sculpture of the specialized ring setae (Figs. 1 E–G and 2 E–H)
are very conspicuous and present on numerous pairs of setae on
diverse external, protruding parts of the body in G. minor but
less conspicuously so in G. maior. Rings of these unique setae
considered out of context could be confused with small debris
attached to thrips bodies during immersion in resin or regarded
as other extraneous artifacts. Features of these setae that indicate that the presence of rings as an anatomical feature
characteristic of the genus are: (i) ring setae are distributed in
a bilateral symmetrical manner on major body regions, such as
wings; (ii) rings have a regularly spaced occurrence along the
length of each seta; (iii) rings are fundamentally homogeneous
in both shape and size throughout all bearing specimens; (iv)
ring setae are observed on all female Gymnopollisthrips specimens and never have been observed on other insect specimens
(including other thrips) in Spanish amber; (v) holotype specimens occur in transparent amber and lack particles that could be
trapped by the setae during immersion in resin; and (vi) isolated
or irregularly distributed, ring-like particles have not been obPeñalver et al. www.pnas.org/cgi/content/short/1120499109
served attached to other setae from the same Gymnopollisthrips
specimens.
Diverse, special setae in thrips can be related to various activities such as mating, flight, and oviposition, but we infer
a function involving collection and transportation of pollen
grains. Such a function for ring setae is based on several features:
(i) ring setae are typically located in the external, protruding
parts of the body; (ii) rings increase the surface area of each seta,
allowing for potential attachment of pollen grains; (iii) ring setae
have not been observed in thrips specimens that lack attached
pollen grains; (iv) pollen grains associated with ring setae are
always the same palynospecies; (v) ring setae are present in all of
the female specimens (n = 4) of the two species of Gymnopollisthrips; and (vi) the presence of abundant pollen grains in
the basal parts of ring setae and their absence in the distal parts
indicate both a direct association between pollen grains and ring
setae and relocation of pollen grains by the thrips before flight.
The three last circumstances also would be inconsistent with an
accidental presence of pollen grains on the bodies of the thrips
specimens.
Flight in modern thrips is often preceded by several minutes of
abdominal and wing flexing, waving of the forelegs, and wing
combing with the legs (61, 62). Such movements may be involved
in the relocation of pollen grains to other regions of the body,
whereby better transport would be assured. This is a crucial issue, because it has been reported that recent pollinating thrips of
cycads lose approximately half of the pollen grains in transport
from the time they depart male cones until they alight on female
cones (4, 6, 63). It is likely that amber entombment of thrips
laden with relocated pollen occurred in flight soon after departure from a pollen organ.
Paleoecology and Taphonomy. Four important amber deposits are
known from the Spanish Albian (32, 33), some of which were
formerly considered as upper Aptian–lower Albian. The deposits
are El Soplao in Cantabria (44, 45), San Just and Arroyo de la
Pascueta in Teruel Province (46), and Peñacerrada I in Burgos
Province (33, 34). Peñacerrada I is the deposit that contains the
amber pieces with the several thrips inclusions that were covered
by clusters of pollen grains. These deposits originated in deltaic
environments and contain abundant, exceptionally well-preserved
plant cuticles.
Plant assemblages from these deposits are dominated by Frenelopsis, an arborescent cheirolepidiaceous conifer that produced distinctive, abundant pollen grains of Classopollis type.
Less abundant are the foliage genera Eretmophyllum and Pseudotorellia, which produced the rare pollen of Cycadopites type.
An important observation of some earlier authors is that Frenelopsis was one of the amber source plants for the Spanish
Lower Cretaceous (45, 64). This inference is buttressed by the
presence of Frenelopsis axes attached to amber in channel facies
from the El Soplao outcrop (32). Najarro, Menor-Salván, and
coworkers (45, 64) also have ascertained a cheirolepidiaceous
botanical origin for this amber, reinforcing this hypothesis. These
authors determined a cheirolepidiaceous source by characterizing specific biomarkers and other diagnostic compounds of
Frenelopsis foliage, which they compared with known compounds
from amber in the same deposit, concluding that they share the
same botanical attribution.
Both Frenelopsis and Eretmophyllum from Spanish Albian amber outcrops show anatomical evidence for xeromorphy (46, 65,
66). It has been proposed that these plants grew along the lower
reaches of the delta plain, around ponds and interdistributary bays
that record marine and freshwater water input, producing substrates with variable salinity levels (47, 65). Based on analogous
data from the Czech Republic, arborescent Eretmophyllum was
the first unequivocal halophyte among the Ginkgoales. The Czech
data strongly support the conclusion that the ginkgoalean Eret4 of 12
signed to the form-genus Nehvizdyella, were hydrodynamically
transported together despite their different shape, indicating
the absence of long distance transport. Alternatively, the most
similar pollen grains to Cycadopites pollen occurring on Gymnopollisthrips are those found in situ for an Antarctic Triassic
cycad species (13) and the pollen grains of some extant species
of Macrozamia cycads pollinated by Cycadothrips (5, 6, 63).
Thus, some palynological data suggest that cycads may have
been pollinated by Cretaceous thrips. Cycads at Peñacerrada I
may have inhabited the forest understory, perhaps growing
among Frenelopsis plants and producing few vegetative remains
of low fossilization potential, explaining their rarity in cuticle
assemblages.
Palynological examination of the amber-bearing sediments
from the Peñacerrada I deposit also indicates the rare presence
of monosulcate pollen grains, typically cited as Monosulcites sp.
(71), which similarly are scarce in other Albian amber outcrops
throughout Spain (45, 72, 73). This parallel pattern of comparatively rare monosulcate grain distribution would be similar to
that of Cycadopites, if insects were pollinating a source plant of
relatively short stature and producing low levels of pollen within
the understory of dense forests. This situation is found in modern thrips pollinators of short-statured, frequently herbaceous
angiosperms (Table S3). Regional vegetation based on palynological studies reveal that everwet, mixed conifer forests existed
on more elevated alluvial plains, whereas xeromorphic vegetation that included short-statured plants were adapted to coastal
environments, as represented by cheirolepidiaceous conifers,
ferns adapted to dry conditions, gnetaleans, and other seed
plants with psilate and monosulcate pollen grains such as ginkgoaleans and cycads (74).
In conclusion, megafossil and taphonomic data strongly suggest
an association of Gymnopollisthrips with Eretmophyllum. By
contrast, palynological evidence is more indicative of a Gymnopollisthrips–cycad association, allowing for a viable hypothesis of
an association with cycads.
mophyllum occupied water-stressed environments within a coastal
salt marsh (65). Altogether, these data suggest that the ginkgoalean taxa grew very close to the resiniferous plants.
The presence of several amber-entombed individuals of the two
Gymnopollisthrips species that vectored abundant and body-adhering Cycadopites pollen grains indicates that the local Peñacerrada I assemblage included resiniferous plants and at least
one pollinated gymnosperm. This proposed pollination mutualism involved thrips, miniscule insects that are not particularly
efficient in flight, as are very small insects, such as mymarid and
mymarommatid wasps with highly reduced wings that lack veins
(or are very reduced) and instead bear numerous long fringe
setae. This type of flight effectively results in swimming through
air as a viscous medium (67) and represents a type of pollination
indicating the proximity of Gymnopollisthrips to their host plant
or plants. Gymnopollisthrips and other insect taxa probably arrived at and were entrapped in resin flows soon after their flight
from male plant-host organs.
Our examination of the 3D coverage of pollen grains on the
G. minor holotype (specimen MCNA-10731) supports this inference (Movie S1). The G. minor specimen is covered by ca. 140
pollen grains on the thorax and distal abdomen (Fig. 1 B–D).
Adjacent to this thrips, 1 mm distant, is a small, internal amber
surface covered by ca. 150 pollen grains (Fig. 2 I and J). Another
isolated cluster containing about 70 grains occurs in the amber
piece bearing specimen MCNA-9516 at 2.5 mm from this female
thrips with pollen loads (ca. 50 pollen grains) (Fig. 1A). The
paratype specimen of G. minor bears only ca. 15 pollen grains on
the ventral part of the abdomen and an additional few grains on
the dorsal aspect. The holotype specimen of G. maior contains
ca. 137 pollen grains in contact with its thoracic ventral surface,
but some of them are detached and form an attenuated tail (Fig.
2A and Fig. S1). This phenomenon has been observed in Cenozoic ambers with other obligate pollinators (68), such as bees
and fig wasps that possess structures for pollen grain attachment
(68, 69). For the Peñacerrada I thrips, several grains, often in
clusters, contact the basal parts of the long ring setae of the distal
abdomen and ventral wing surfaces (Figs. 1 H–J and 2 E–H). The
four thrips carrying pollen grains are females; parallel observations show that modern female Cycadothrips pollinate
Macrozamia cycads and transport a notably higher quantity of
pollen grains than males (6). These distributions of clustered and
isolated grains of monospecific pollen in amber may be explained
by the plant hosts simultaneously possessing both insect and
wind types of pollination (ambophily), occurring in a few extant
species of cycads (2, 70).
An important aspect of fossil thrips pollination inferred from
amber inclusions and associated macrofossils is the parautochthonous nature of Spanish Albian deposits, indicating that
ginkgoalean and cycad plants could have been the source of the
Cycadopites pollen. In addition to the ecological conditions required by the cheirolepidiaceous Frenelopsis and ginkgoalean
Eretmophyllum, at El Soplao, there are Frenelopsis vegetative
shoots that are commonly branched up to four ranks, suggesting
parautochthonous deposition (45). Additionally, both abscised
leaves and ovulate reproductive organs of Eretmophyllum, as-
Fossil Taxa for Phylogeny Calibration. The references of the thrips
taxa listed in the legend of Fig. 3 for Thysanoptera phylogeny are as
follows: Cyphoneurodes patriciae (75) (Fig. 3, numbered 1); Burmacypha longicornis (76) (Fig. 3, numbered 2); Triassothrips virginicus (77) (Fig. 3, numbered 3); Kazachothrips triassicus (78) (Fig.
3, numbered 4); Karataothrips jurassicus (79) (Fig. 3, numbered 5);
Cretothrips antiquus (77) (Fig. 3, numbered 6); extant Cycadothrips
chadwicki (6) (Fig. 3, numbered 7); Gymnopollisthrips minor, G.
maior (this report) (Fig. 3, numbered 8); Tethysthrips libanicus (80)
(Fig. 3, numbered 9); Tethysthrips hispanicus (80) (Fig. 3, numbered
10); several extant genera (Table S3) (Fig. 3, numbered 11); several
occurrences in Lebanese amber (81) (Fig. 3, numbered 12); Hispanothrips utrillensis (82) (Fig. 3, numbered 13); and Rohrthrips libanicus (80) (Fig. 3, numbered 14). The Lophioneuridae are
indicated as a sister-group of the Thysanoptera. Represented plant
groups have geological age ranges taken from Taylor et al. (83); the
superimposed thysanopteran phylogeny is mainly from two publications (84, 85), with limited modification. The thysanopteran
phylogeny is calibrated by a geochronology (86).
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x, Johnson SD (2009) Beetle pollination of the fruit-scented cones of the
South African cycad Stangeria eriopus. Am J Bot 96:1722–1730.
71. Barrón E, Comas-Rengifo MJ, Elorza L (2001) Contribuciones al estudio palinológico
del Cretácico Inferior de la Cuenca Vasco–Cantábrica: Los afloramientos ambarígenos
de Peñacerrada (España). Col Paleontol 52:135–156.
72. Peyrot D, Rodríguez-López JP, Lassaletta L, Meléndez N, Barrón E (2007)
Contributions to the palaeoenvironmental knowledge of the Escucha Formation in
the Lower Cretaceous Oliete Sub-basin, Teruel, Spain. C R Palevol 6:469–481.
73. Solé de Porta N, Querol X, Cabanes R, Salas R (1994) Nuevas aportaciones a
la palinología y paleoclimatología de la Formación Escucha (Albiense inferior-medio)
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203–215.
74. Diéguez C, Peyrot D, Barrón E (2010) Floristic and vegetational changes in the Iberian
Peninsula during Jurassic and Cretaceous. Rev Palaeobot Palynol 162:325–340.
75. Beckemeyer RJ, Hall JD (2007) The entomofauna of the Lower Permian insect beds of
Kansas and Oklahoma, USA. Afr Invertebr 48:23–39.
76. Zherikhin VV (2000) A new genus and species of Lophioneuridae from Burmese
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77. Grimaldi DA, Shmakov A, Fraser N (2004) Mesozoic thrips and early evolution of the
order Thysanoptera (Insecta). J Paleontol 78:941–952.
78. Shmakov AS (2008) The Jurassic thrips Liassothrips crassipes (Martynov, 1927) and its
taxonomic position in the order Thysanoptera (Insecta). Paleontol. J 42:47–52.
79. Sharov AG (1972) The phylogenetic relations of the order Thysanoptera. Entomol
Obozr 51:854–858.
80. Nel P, Peñalver E, Azar D, Hodebert G, Nel A (2010) Modern thrips families Thripidae
and Phlaeothripidae in Early Cretaceous amber (Insecta: Thysanoptera). Ann Soc
Entomol Fr 46:154–163.
81. zur Strassen R (1973) Insektenfossilien aus der unteren Kreide. 5. Fossile Fransenflüger
aus mesozoischem Bernstein des Libanon (Insecta: Thysanoptera). Stuttg Beitr
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82. Peñalver E, Nel P (2010) Hispanothrips from Early Cretaceous Spanish amber, and
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83. Taylor TN, Taylor EL, Krings M (2009) Paleobotany: The Biology and Evolution of Fossil
Plants (Academic Press, New York).
84. Heming BS (1993) Functional Morphology of Insect Feeding, eds Schaefer CS,
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85. Mound LA, Heming BS, Palmer JM (1980) Phylogenetic relationships between the
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86. Ogg JG, Ogg G, Gradstein FM (2008) The Concise Geologic Time Scale (Cambridge
Univ Press, Cambridge, UK).
Fig. S1. Habitus of Gymnopollisthrips maior sp. nov. Microphotographs of the holotype in lateral (Upper) and ventral (Lower). Views are at the same scale.
Peñalver et al. www.pnas.org/cgi/content/short/1120499109
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Fig. S2. Planate sensory structure on antennal segment III of Gymnopollisthrips maior sp. nov. Microphotographs in lateral view of the planated sensory
structure (arrows) on segment III of both antennae from the holotype, at same scale.
Fig. S3. Head of Gymnopollisthrips maior sp. nov. Camera lucida drawing of the head in dorsal view. Plate-like sensory areas and conical tubercle with ocellar
setae I are colored in gray.
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Table S1.
Ability of modern thrips to carry pollen
Plant host taxon
Fossil gymnosperms
Gymnosperm indet.
(Ginkgoales or Cycadales)
Gymnosperm indet.
(Ginkgoales or Cycadales)
Extant gymnosperms*
Macrozamia macdonnellii
(Zamiaceae)
Macrozamia communis
(Zamiaceae)
Macrozamia lucida
(Zamiaceae)
Extant angiosperms†
Medicago sativa (Fabaceae)
Eschscholzia californica
(Papaveraceae)
Bellis perennis (Asteraceae)
Prunus domestica (Rosaceae)
Eschscholzia californica
(Papaveraceae)
Beta vulgaris
(Chenopodiaceae)
Castilla elastica (Moraceae)
Shorea lepidota
(Dipterocarpaceae)
Chloranthus serratus
(Chloranthaceae)
Macaranga hullettii
(Euphorbiaceae)
Thrips pollinator taxon
Gymnopollisthrips minor gen.
et sp. nov. (Melanthripidae)
Gymnopollisthrips maior sp.
nov. (Melanthripidae)
No. of thrips
examined
Greatest no. of
grains observed
Average grains
per thrips
Source
2
140
77.5
This report
1
137
137
This report
38 (10)
69 (24)
20.5 (15.1)
1
66 (56)
255 (96)
52.1 (21.6)
2
531 (258)
223 (145)
107 (29.2)
3
130
16
2.3
4
96
20
3.3
4
20
4
2.0
4
16
3
0.2
4
10
3
3
4
2
140
137
4
1,099
72
7.6–25.8
5
70
27
2.43
6
Taeniothrips eucharii (Thripidae)
2
>40
38
7
Neoheegeria sp. (Phlaeothripidae)
91
268
63.6
8
Cycadothrips albrechti
(Aeolothripidae)
Cycadothrips chadwicki
(Aeolothripidae)
Cycadothrips chadwicki
(Aeolothripidae)
Frankliniella tritici
(Thripidae)
Frankliniella tritici
(Thripidae)
Frankliniella minuta
(Thripidae)
Frankliniella tritici
(Thripidae)
Anaphothrips secticornis
(Thripidae)
Thrips tabaci
(Thripidae)
Frankliniella diversa
(Thripidae)
Thrips sp. (Thripidae)
*Counts include thrips departing male cones and no. of thrips subsequently arriving at female cones.
†
Representative examples for comparison, not an exhaustive list from the bibliography.
1.
2.
3.
4.
5.
6.
7.
8.
Mound LA, Terry I (2001) Thrips pollination of the Central Australian cycad, Macrozamia macdonnellii (Cycadales). Int J Plant Sci 162:147–154.
Terry I (2001) Thrips and weevils as dual, specialist pollinators of the Australian cycad Macrozamia communis (Zamiaceae). Int J Plant Sci 162:1293–1305.
Terry LI, et al. (2005) Pollination of Australian Macrozamia cycads (Zamiaceae): Effectiveness and behavior of specialist vectors in a dependent mutualism. Am J Bot 92:931–940.
Lewis T (1973) Thrips, Their Biology, Ecology and Economic Importance (Academic Press, New York).
Sakai S (2001) Thrips pollination of androdioecious Castilla elastica (Moraceae) in a seasonal tropical forest. Am J Bot 88:1527–1534.
Appanah S, Chan HT (1981) Thrips: The pollinators of some dipterocarps. Malaysian Forester 44:234–252.
Luo Y, Li Z (1999) Pollination ecology of Chloranthus serratus (Thunb.) Roem. et Schult. and Ch. fortunei (A. Gray) Solms–Laub. (Chloranthaceae). Ann Bot (Lond) 83:489–499.
Moog U, Fiala B, Federle W, Maschwitz U (2002) Thrips pollination of the dioecious ant plant Macaranga hullettii (Euphorbiaceae) in Southeast Asia. Am J Bot 89:50–59.
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Table S2. Length and width measurements of pollen grains on
Gymnopollisthrips holotypes
Gymnopollisthrips minor
(MCNA-10731)
Gymnopollisthrips maior
(MCNA-9283)
Length (µm)
Width (µm)
Length (µm)
Width (µm)
22.6
21.0
19.3
19.7
22.1
18.6
21.5
21.0
17.7
19.9
18.8
20.2
19.2
19.7
20.6
21.4
19.7
20.0
23.5
22.5
21.1
23.0
21.8
24.9
21.1
21.2
21.0
20.0
19.2
20.6
22.4
19.7
19.2
23.2
19.0
18.6
19.9
22.1
21.5
21.2
10.8
12.5
12.4
9.7
10.4
13.8
9.3
13.7
10.4
12.2
13.6
14.4
11.5
11.6
11.3
12.1
12.3
9.9
12.8
11.2
10.6
12.5
11.6
13.1
14.1
12.4
12.8
12.1
12.2
13.4
11.3
14.1
11.9
10.9
11.7
11.7
15.8
11.3
11.9
15.4
23.5
21.2
19.2
19.9
23.8
22.1
22.1
22.3
21.5
19.2
20.0
20.0
20.0
16.5
20.1
18.4
20.0
20.6
17.4
18.8
19.9
21.9
22.7
19.9
20.2
21.2
21.1
20.0
19.8
19.8
17.7
21.1
18.6
16.7
15.3
18.8
21.6
20.1
21.8
19.3
11.7
11.7
13.3
16.2
14.0
12.9
11.9
14.4
12.5
11.5
10.2
13.1
11.5
9.4
13.5
11.9
13.6
14.2
10.8
12.9
12.5
12.8
14.6
13.3
11.7
9.6
11.3
14.3
15.4
11.5
18.1
13.5
13.9
13.9
13.4
12.4
14.0
11.4
12.6
11.5
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Antevsia zeilleri (Nathorst) Harris
Sahnia laxiphora Drinnan & Chambers
Sahnia nipaensis Mittre
Synangispadixis tidwellii Cornet
29–46.25
24–28
10–22
21–29
30–42.5
23–35
∼12
∼25
22–33
20.5–29.0
24–32
24.5–31
24–33
20–25
∼20
29–42
31
26.3–30.8
20–29.8
20–25
7–17
11–19
20–26
13–23
>13
14.7–25.6
15–19
∼13
14.5–19.5
14.5–19.8
∼13
11.07 ± 0.69
16.9–28.9
∼25
24.18 ± 1.53
24.9–35.9
Macrozamia macdonnellii (Miq.) A. DC.
Macrozamia miquelii (F. Muell.) A. DC.
Ginkgo biloba L.
Cycadeoidea dacotensis Macbride
Williamsoniella coronata Thomas
Androstrobus balmei Hill
Androstrobus szei Harris [light microscopy]
Androstrobus szei Harris [S.E.M.]
Androstrobus wonnacotti Harris [light microscopy]
Androstrobus wonnacotti Harris [S.E.M.]
Delemaya spinulosa Klavins et al.
Ginkgo huttoni (Sternberg) Heer
Ginkgo liaoningensis Liu, Li & Wang
Nehvizdyella bipartita Kvacek,
Falcon–Lang & Dasková
Aegianthus sibiricum (Heer) Krassilov
Antevsia extans (Frenguelli) Townrow
18.70 ± 0.98
34.2–23.8
22.00 ± 1.18
19.78 ± 0.31
20.18 ± 1.12
11.13 ± 1.09
30.32 ± 1.01
27.5–34.3
28.32 ± 0.96
32.72 ± 1.35
38.40 ± 1.82
21.57 ± 1.24
Bowenia spectabilis Hook ex. Hook
Cycas revoluta Thunb.
Dioon edule Lindl.
Encephalartos ferox (G. Bertol.) Lehm.
Lepidozamia peroffskyana Regel
Macrozamia lucida
Width (µm)
12.6 (9.3–15.4)
Length (µm)
20.4 (17.4–24.9)
Taxon
Indet. (Cycadopites pollen form genus)
S.E.M., scanning electron microscopy.
Peltaspermales
Pentoxylales
Pentoxylales
Incertae sedis
Gnetales
Peltaspermales
On Gymnopollisthrips
minor and G. maior
Ginkgoales or Cycadales
Modern taxa
Cycadales
Cycadales
Cycadales
Cycadales
Cycadales
Cycadales
L.A.S. Johnson
Cycadales
Cycadales
Ginkgoales
Fossil taxa
Bennettitales
Bennettitales
Cycadales
Cycadales
Cycadales
Cycadales
Cycadales
Cycadales
Ginkgoales
Ginkgoales
Ginkgoales
Order
Table S3. Morphology of in situ Cycadopites pollen from fossil and extant gymnosperms
1.5
1–1.5
∼0.73
0.5–1
0.57–1.16
1–1.5
>0.56
1.5–2
0.45–0.65
3.0–5.4
4.8–7.2
1.3 (0.7–2.5)
Exine (µm)
Middle Jurassic
Lower and Middle
Triassic
Upper Triassic
Lower Cretaceous
Jurassic
Upper Triassic
Lower Cretaceous
Middle Jurassic
Middle Jurassic
Middle Jurassic
Middle Jurassic
Middle Jurassic
Middle Jurassic
Middle Triassic
Middle Jurassic
Lower Cretaceous
Upper Cretaceous
Extant
Extant
Extant
Extant
Extant
Extant
Extant
Extant
Extant
Lower Albian
Age
Spindle-shaped
Ovoid
Elliptic or circular
Elliptic; tectate–granular
Elliptic; ornamented with pits
Spindle-shaped
Ovoid to spherical
Elliptic to almost circular
Ovoid
Elliptic to almost spherical
Ovoid to broadly ovoid
Elliptic to circular
Broadly ovoid to subspherical
Broadly ovoid (ellipsoidal)
Elongated–elliptic
Elongated–elliptic
Boat-shaped
Elliptic to spherical
Elliptic
Almost spherical
Elliptic
Shape
54
55
51
43
53
54
19
49
50
49
50
49
50
13
49
52
64
5
18
Our data
18
Our data
18
18
18
18
This study
Source
Movie S1. Three-dimensional movie of the holotype specimen of Gymnopollisthrips minor gen. et sp. nov. (MCNA-10731) imaged by synchrotron tomography
to better study the pollen distribution. All of the pollen grains detected by synchrotron tomography have been colored in yellow.
Movie S1
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