The stomata of ALETHOPTERIS SULLIVANTII and NEUROPTERIS SCHEUCHZERI are actinocytic-haplocheilic similar to those found in various modern cycads and conifers


Reihman M. A., Schabilion J. T. (1985)

American Journal of Botany 72(9): 1392-1396 –


The stomatal apparati of the pteridosperm foliage taxa Alethopteris sullivantii (Lesquereux) Schimper and Neuropteris scheuchzeri (Hoffman) forma decipiens (Lesquereux) Gastaldo were examined from Middle Pennsylvanian coal balls collected from central Iowa.

Standard light optics, Nomarski, and SEM were utilized to study cellulose acetate peels and macerated cuticle material. The stomatal apparati of both taxa are actinocytic-haplocheilic and are similar to those found in various modern cycads and conifers. The previous report by Stidd and Stidd of paracytic-syndetocheilic stomata in A. sullivantii resulted from misinterpretation of the guard cell’s configuration and differentially thickened walls.

Stomata in fossil Syzygium (Myrtaceae)

FIGURE 3. Different stomatal morphologies across subgenera in Syzygium Gaertn. (A) Paracytic stomata in Syzygium branderhorstii Lauterb. (subgenus Syzygium), with large double-lid-cell in center (scale bar = 20 μm). (B) Paracytic stomata in Syzygium paniculatum Gaertn. (subgenus Syzygium), with highly sinuous epidermal cells and a double-lid-cell on the right (scale bar = 40 μm). (C) Anisocytic and cyclostaurocytic stomata in Syzygium claviflorum (Roxb.) Wall. Ex A.M.Cowan & Cowan (subgenus Perikion) with large double-lid-cell in center-right (scale bar = 40 μm). (D) Paracytic, anisocytic, and occasionally staurocytic stomata in Syzygium suborbiculare (Benth.) T.G.Hartley & L.M.Perry (subgenus Syzygium) with double-lid-cell at the bottomcenter (scale bar = 40 μm). (E) Cyclostaurocytic stomata on the cuticle of Syzygium hemilamprum (F.Muell.) Craven & Biffin (subgenus Acmena) (scale bar = 50 μm). (F) Cyclostaurocytic stomata in Syzygium smithii (Poir.) Nied. (subgenus Acmena); note the ring-like arrangement of subsidiary cells with straighter edges than the surrounding epidermal cells (scale bar = 40 μm).

Identifying fossil Myrtaceae leaves: the first described fossils of Syzygium from Australia

Tarran M., Wilson P. G., Paull R., Biffin E., Hill R. S.(2018)

Myall Tarran, Peter G. Wilson, Rosemary Paull, Ed Biffin, Robert S. Hill,


American Journal of Botany: 105(10) – DOI: 10.1002/ajb2.1163

FIGURE 4. General features of fossil and extant cuticles. (A) Light micrograph (LM) of adaxial cuticle from K707, holotype of Syzygium christophelii sp. nov. Mid-center-right is an oil gland. Lidcells are distinguished from hair bases in that they have at least one, usually two or more, cells in the middle of a large ring of subsidiary cells; in contrast, a hair base extends over a smaller ring of radially arranged cells that form a “star-like” pattern in their center (scale bar = 50 μm). (B) LM of abaxial cuticle of Syzygium christophelii, specimen K757; note the random orientation of stomata, damage to cuticle, and lack of recognizable hair-base structures (scale bar = 100 μm). (C) LM of the adaxial cuticle of Syzygium smithii (Poir.) Nied (subgenus Acmena), with a lid-cell structure in the top right. Again, note the absence of recognizable hair-base structures (scale bar = 50 μm). (D) LM of abaxial cuticle of S. smithii showing stomatal surface, again noting the random orientation of stomata, sinuous epidermal cell walls, and absence of recognizable hair-base structures (scale bar = 100 μm). (E) LM of adaxial cuticle of Eugenia reinwardtiana (Blume) A.Cunn. ex DC. (Tribe Myrteae), Australia’s only endemic species of Eugenia, showing regular trichome bases, with distinctive “star-like” underlying epidermal cell morphology (scale bar = 50 μm). (F) LM of cuticle of extant species of Backhousia citriodora F.Muell. showing dense trichomes and stomata on the abaxial cuticle surface. Note elongated epidermal cells in non-stomatiferous area, probably indicating an underlying vein. Note also two different sizes of hair bases, with larger ones occurring in the non-stomatiferous zones overlying the vein (scale bar = 50 μm).

Abstract and figures

Premise of the Study

Although leaves of Myrtaceae are easily identified to family level, very few studies have convincingly identified fossil Myrtaceae leaves to living genera. We used a broadly comparative approach with a large data set of extant taxa to confidently assign the mummified remains of myrtaceous leaves from early Miocene sediments at Kiandra (New South Wales, Australia) to a living genus.


Fossils were identified using a nearest living relative approach, against a database of 232 extant broadleaf rainforest species of Myrtaceae. Leaf cuticles were prepared from 106 species, sourced from herbarium specimens as well as some living individuals, and a further 127 records were assembled from the literature. A set of simple but phylogenetically informative cuticular characters were observed, described, and recorded under both scanning electron microscopy and standard light microscopy.

FIGURE 5. Cuticle damage in the form of cork warts. (A) Light micrograph (LM) of the abaxial cuticle of fossil holotype specimen K707, showing a section of extreme cuticle damage. In the top right corner of the image, a large number of stomata have been damaged by possible fungal or insect attack, and formed stomatal cork warts (scale bar = 100 μm). (B) LM of more damage on the abaxial cuticle of K707 showing a large cork wart in the middle-top-left, with smaller damage marks surrounding (scale bar = 100 μm). (C) LM of adaxial cuticle of extant species Syzygium anisatum (Vickery) Craven & Biffin, showing large-and small-scale damage, which disturbs the otherwise consistent patterns of the epidermal cell impressions on the adaxial cuticle (scale bar = 100 μm). (D) LM of cork wart on the adaxial cuticle of extant species Syzygium paniculatum Gaertn., and a lid-cell to the left. These are the only structures other than epidermal cells commonly visible on the adaxial cuticles of extant Syzygium species (scale bar = 50 μm).

Key Results

A new fossil species of Syzygium Gaertn. is described from mummified remains found in early Miocene (21.5–21.7 Ma) sediments. The fossil taxon is here named Syzygium christophelii sp. nov., in honor of the late Australian paleobotanist David Christophel.


These fossils represent some of the most confidently described Myrtaceae leaf fossils published to date and are the first and oldest described fossil record of Syzygium from Australia. While several fossil parataxa have been illustrated from New Zealand, and several fossil species of Syzygium have previously been proposed in the literature, many of these fossils lack characters for a confident diagnosis.

FIGURE 6. Cyclostaurocytic stomata on fossil taxa. (A) Scanning electron micrograph (SEM) of fossil Holotype K707 showing the underside of the abaxial cuticle and the internal impression of several stomata and epidermal cells (scale bar = 20 μm). (B) SEM of a single stomate showing the arrangement of four subsidiary cells around the guard cells of the stomate (scale bar = 10 μm). (C) Light micrograph (LM) of abaxial cuticle of K707, showing stomatal arrangement and a doublelid-cell at center left (scale bar = 50 μm). (D) LM close-up view of abaxial cuticle of K707 showing subsidiary cell arrangements of three stomata, with four or more subsidiary cells in a ring around the guard cells (scale bar = 20 μm). (E) LM of parataxon “CUT-M-DIE” taken from Pole et al. ‘s (2008) study of Miocene New Zealand fossil Myrtaceae cuticles, compared most favorably with species from Syzygium subgenus Acmena, showing what they called “tangenticytic” stomatal complexes, which we find to be synonymous with the “cyclostaurocytic” stomatal definition proposed by Soh and Parnell (2011) (original scale bar included = 50 μm). (F) LM close-up view of subsidiary cell arrangement of stomate on abaxial cuticle of parataxon “CUT-M-DIE” taken from Pole et al. ‘s (2008) study of Miocene New Zealand fossil Myrtaceae, showing the four or more subsidiary cells in a band around the guard cells (original scale bar included = 20 μm).

Stomata in fossil Laurelia (Atherospermataceae)

Fig. 3. Laurelia otagoensis leaf epidermal cuticles and fruits. A, OU32328, adaxial epidermis. B, OU32680, abaxial epidermis showingdifferentiated laterocytic to staurocytic subsidiary cells. C, OU32328, abaxial surface showing stomate and thickened trichome base. D, OU32412,abaxial surface with almost dicyclic staurocytic stomate, polar t-pieces and polar rods.

Fruits and leaves with cuticle of Laurelia otagoensis sp. nov. (Atherospermataceae) from the early Miocene of Otago (New Zealand)

Conran J. G., Bannister J. M., Lee D. E. (2013)

John G. Conran, Jennifer M. Bannister, Daphne E. Lee,

Alcheringa 37: 496–509 – ISSN 0311-5518 –

Fig. 5. Extant Atherospermataceae leaf and fruit characteristics. A, Doryphora sassafras Endl., pseudocarps formed by the urceolate hypanthium.B, Atherosperma moschatum Labill., mature pseudocarp releasing plumose achenes. C–H, Laurelia novae-zelandiae A. Cunn. C, Cleared leafshowing festooned semicraspedodromous venation and gland-tipped marginal teeth. D, Heavily thickened trichome base. E, Cleared leaf showingvenation. F, Plumose achene. G, Adaxial epidermis with hypodermis. H, Abaxial epidermis with stomata. I–L, Laurelia sempervirens (Ruiz &Pav.) Tul. I, Cleared leaf showing venation. J, Plumose achene. K, Adaxial epidermis. L, Abaxial epidermis with stoma and striated subsidiarycells. M–P, Laureliopsis philippiana (Looser) Schodde. M, Cleared leaf showing venation. N, Plumose achene. O, Adaxial epidermis with oilgland. P, Abaxial epidermis with stomata and striated subsidiary cells. Vouchers listed in Table 1. Scale bars for A–B, E, I, M = 10 mm; C, F, J, N= 5 mm; D, G–H, K–L, O–P = 50 μm.


Laurelia otagoensis sp. nov. Conran, Bannister & D.E. Lee (Laurales: Atherospermataceae) is described from the earliest Miocene Foulden Maar diatomite deposit, Otago, New Zealand.

The new species is represented by mummified fossil leaves with well-preserved cuticle and associated clusters of achenes bearing persistent, long plumose styles. This basal angiosperm family is of significance because of its classic southern disjunctions and ecological importance in extant Gondwana-type rainforests, but has a very sparse fossil record.

The present study describes one of very few convincing leaf fossils for Atherospermataceae and the only definitive fossil fruits. The presence of fossil Laurelia in Oligo–Miocene New Zealand combined with fossil leaf impressions from the late Eocene, Miocene dispersed cuticle and pollen from the Oligocene to Holocene shows that the family has had a long history in Cenozoic New Zealand. These new fossils also support palaeoclimatic data suggesting warmer conditions in the earliest Miocene of New Zealand.


Stomata non-areolate, subsidiary cells more or less differentiated from those of the epidermis, irregularly laterocytic to staurocytic with varying numbers of cells, in some cases bicyclic.

Stomata in fossil monocots

Leaf and inflorescence evidence for near-basal Araceae and an unexpected diversity of other monocots from the late Early Cretaceous of Spain

Sender L. M., Doyle J. D., Upchurch G. R. Jr., Villanueva-Amadoz U., Diez J. B. (2019)
Luis Miguel Sender
, James A. Doyle, Garland R. Upchurch Jr, Uxue Villanueva-Amadoz, José B. Diez,


Journal of Systematic Palaeontology 17(15): 133-1346 – ISSN: 1477-2019 (Print) – 1478-0941 (Online 2018) –


Phylogenetic analyses imply that monocots were a key group in the early radiation of angiosperms, yet they are much rarer than other major clades in the Early Cretaceous macrofossil record.

Here we describe a well-preserved leaf and several inflorescences related to the near-basal monocot family Araceae and abundant monocot leaves of uncertain affinities from two latest Albian localities in north-eastern Spain. Orontiophyllum ferreri sp. nov. has a multistranded midrib, several orders of parallel-pinnate veins, two orders of transverse veins, and paracytic-oblique stomata. This suite of characters (but with both anomocytic and paracytic-oblique stomata) is characteristic today of Orontium in the near-basal araceous subfamily Orontioideae, and later Cretaceous and early Cenozoic leaves assigned to Orontiophyllum have similar architecture.

Sedimentology and anatomy suggest a (semi)aquatic ecology. Other monocot leaves at the same locality are linear and parallel-veined but have similar stomata. Although anomocytic stomata have been proposed as ancestral in monocots, O. ferreri, the associated linear leaves, Albian–Cenomanian cuticles from Australia and Portugal, and extant data are consistent with the hypothesis that variable paracytic-oblique stomata are ancestral

Turolospadix bogneri gen. et sp. nov., from the other locality, includes spadices of ebracteate flowers with four tepals, a central gynoecium, and a long stipe (vs a spathe attached just below the fertile zone as in most Araceae). Phylogenetic analyses indicate that the character combinations seen in O. ferreri and T. bogneri are ancestral for Araceae, and they could be either sister to Araceae or nested within a basal grade of the family. Together with fossils from the Aptian–Albian of Brazil and Portugal, the Spanish fossils indicate that Araceae are among the oldest extant monocot families, but they were associated with diverse linear-leaved monocots of uncertain affinities.

A likely occurrence of polyploidy in Sphenobaiera huangii may result in underestimated paleo-CO2 when applying mechanistic method due to an increase in the size of the stomatal complex

An inter-comparison study of three stomatal-proxy methods for CO2 reconstruction applied to early Jurassic Ginkgoales plants

Zhou N., Wang Y., Ya L., Porter A. S., Kürschner W. M., Li L., Lu N., McElwain J. C. (2020)

Ning Zhou a-b, Yongdong Wangb, Li Ya b, Amanda S. Porter c, Wolfram M. Kürschner d, Liqin Li b, Ning Lu b, Jennifer C. McElwain c,

a Department of Geology, Northwest University, Xi’an 710069, China

b State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, and Center for Excellence in Life and Paleoenvironment, Chinese Academy of Sciences, Nanjing 210008, China

c Department of Botany, School of Natural Sciences, Trinity College Dublin, the University of Dublin, Dublin 2, Ireland

d Department of Geosciences, University of Oslo, N-0316 Oslo, Norway


Palaeogeography, Palaeoclimatology, Palaeoecology 542: 109547 –


• A high degree of consistency in pCO2 and trends are observed in three methods.

• The performance of mechanistic method is improved.

• The genome size may result in overestimated pCO2 when applying mechanistic method.


The inverse relationship between concentrations of CO2 in the atmosphere (pCO2) and the stomatal index of vascular plant has been widely used to estimate ancient levels of atmospheric CO2. However, some atmospheric concentration of CO2 in the geological past (paleo-CO2) estimates show little congruence because they are derived using different correlative methods, or from different fossil plant species with different calibration approaches. Here we apply three methods, including (1) the empirical method of McElwain (1998), (2) the empirical method of Barclay and Wing (2016) and (3) the mechanistic method of Franks et al., (2014) to a single fossil Ginkgo species (Ginkgoites marginatus) to track and assess their consistency of pCO2 estimates for the Early Jurassic. By using an inter-comparison of three methods, a high degree of consistency in pCO2 estimates and trends has been observed in two empirical proxy methods. In addition, the mechanistic method and both the empirical methods also show generally good consistent paleo-CO2 estimates at the bed-level. To test the congruence of paleo-CO2 estimates, we also apply all three methods to one additional Ginkgoalean fossil species (Sphenobaiera huangii). All three methods show species-dependent uncertainty in paleo-CO2 estimates when applied to different Ginkgalean fossil species collected from the same fossiliferous bed. Moreover, considering the potential effect of guard cell size to the mechanistic method, the genome size of fossil and living Ginkgo taxa was analyzed based on the significant positive relationship between genome size and guard cell size. The result demonstrates that a likely occurrence of polyploidy in Sphenobaiera huangii may result in underestimated paleo-CO2 when applying mechanistic method due to an increase in the size of the stomatal complex.

Stomatal density worldwide was responding to significant changes in pCO2 across the K–Pg

Global trends of pCO2 across the Cretaceous-Paleogene boundary supported by the first Southern Hemisphere stomatal proxy based pCO2 reconstruction

Steinthorsdottir M., Vajda V., Pole M. (2016)

Margret Steinthorsdottir a, Vivi Vajda b-c, Mike Pole d,

a Department of Geological Sciences and Bolin Centre for Climate Research, Stockholm University, SE 109 61 Stockholm, Sweden

b Department of Palaeobiology, Swedish Museum of Natural History, SE 104 05 Stockholm, Sweden

c Department of Geology, Lund University, SE-223 62 Lund, Sweden

d Nanjing Institute of Geology and Palaeontology, Academia Sinica (the Chinese Academy of Sciences), 39 East Beijing Road, Nanjing 210008, PR China


Palaeogeography, Palaeoclimatology, Palaeoecology 464: 143–152 –


• A new fossil Lauraceae leaf database from New Zealand spans the K–Pg boundary.

• Latest Cretaceous–mid Paleocene pCO2 was reconstructed using the stomatal proxy.

• On average, pCO2 decreased by ~ 45%, from ~ 570 to ~ 310 ppm, during this time.

• Results are consistent with previously published Northern Hemisphere pCO2 records.

• However, a spike of extremely high pCO2 previously reported at K–Pg was not confirmed.


Reliable reconstructions of atmospheric carbon dioxide concentrations (pCO2) are required at higher resolution than currently available to help resolve the relationship between mass extinctions and changes in palaeo-pCO2 levels. Such reconstructions are needed: 1, at a high temporal resolution for constraining the pre- and post-extinction atmospheres; and 2, at a sufficient spatial resolution to constrain potential inter-hemispheric differences. Here we estimate pCO2 based on fossil Lauraceae leaf cuticle specimens derived from three localities with strata spanning the latest Cretaceous to the mid-Paleocene, including a new Cretaceous–Paleogene boundary (K–Pg) locality, in New Zealand. We use two independent methods of stomatal density-based pCO2 reconstructions; a transfer function calibrated using herbarium material and the stomatal ratio method, producing three calibration sets. Our results based on the mean values of each of the three calibration methods indicate pCO2 ranging between ca. 460 and 650 ppm during the latest Cretaceous, falling precipitously to average values between ca. 360 and 430 ppm across the K–Pg boundary, and further to ca. 305–320 ppm in the mid-Paleocene. A ‘spike’ of extremely high pCO2 at the K–Pg could not be confirmed, but our results are, nonetheless, consistent with previously published pCO2 records from the Northern Hemisphere, and show that stomatal density worldwide was responding to significant changes in pCO2 across the K–Pg.

Stomatal densities of fossil plants can be used to reconstruction past CO2 levels

Sulphur dioxide fumigation effects on stomatal density and index of non-resistant plants: implications for the stomatal palaeo-[CO2] proxy method

Haworth M., Elliott-Kingston C., McElwain J. C. (2012)

Matthew Haworth a, Caroline Elliott-Kingston b, Angela Gallagher c, Annmarie Fitzgerald b, Jennifer C. McElwain b,

a CNR – Istituto di Biometeorologia (IBIMET), Via Giovanni Caproni 8, 50145 Firenze Italy b

School of Biology and Environmental Science, University College Dublin, Belfield, Dublin 4, Ireland

c Department of Hydrology and Geo-environmental Sciences, Vrije Universiteit, De Boelelaan 1085–1087, 1081 HV Amsterdam, The Netherlands


Review of Palaeobotany and Palynology 182: 44–54 –


► Stomatal densities of fossil plants can be used to reconstruction past CO2 levels.

► SO2 may also affect stomatal development and therefore estimates of CO2.

► Seven plants with no resistance to SO2 were grown in controlled environments.

► SO2 resulted in an increase in the ratio of stomatal density to index.

► This ratio may be employed to differentiate between SO2 and CO2 effects on stomata.



The inverse relationship between the number of stomata on the surface of a leaf and the atmospheric concentration of carbon dioxide ([CO2]) in which it developed permits the use of fossil plants as indicators of palaeo-atmospheric [CO2] level (palaeo-[CO2]). This “stomatal method” to reconstruct palaeo-[CO2] is dependant upon stomatal initiation being determined by [CO2]. However, global perturbations to the carbon cycle and climate system throughout earth history are not only characterised by fluctuations in the level of atmospheric [CO2], but also by the release of large volumes of toxic gases such as sulphur dioxide (SO2) into the atmosphere. Recent studies have raised uncertainties into the efficacy of stomatal palaeo-[CO2] proxies during episodes of SO2 fumigation. This study aims to assess the effect of exposure to 0.2 ppm SO2 on the stomatal frequencies of plant species with no evolutionarily acquired resistance to toxic gases in comparison to individuals grown under control conditions and atmospheres of elevated [CO2]. Fumigation with SO2 resulted in a general pattern of increased stomatal density (SD) values, but induced variability in the stomatal index (SI) responses of the plant species studied. Ginkgo biloba exhibited an increase in SI, whereas the araucariacean conifers Agathis australis and Araucaria bidwillii displayed reductions in SI that were indistinguishable from values observed under [CO2] enrichment. These results suggest that the presence of atmospheric SO2 may reduce the effectiveness of stomatal reconstructions of palaeo-[CO2] during intervals characterised by the release of large volumes of toxic gases into the atmosphere. However, exposure to SO2 induced significant increases in the SD/SI ratios of six of the seven species studied. Calculation of the SD/SI ratios of fossil plants may identify any stratigraphic horizons where the stomatal initiation responses of the fossil flora were affected by sudden fumigation with toxic gases, and thus influence palaeo-[CO2] estimates. Therefore the SD/SI ratios of fossil plants may serve as indicators of the effectiveness of stomatal reconstructions of palaeo-[CO2].

Calculated as stomatal ratios, the values generally tracked the CO2 variations predicted by a long-term carbon cycle model confirming the utility of this plant group to provide a reasonable measure of ancient atmospheric CO2 change

Figure 1–9
The lower epidermal characters of extant and fossil Ginkgo leaves. 1. Replica of lower epidermis on G. biloba leaf collected in 1924. Figs. 2–5. Ginkgo biloba (collected in 1998). 2. No significant differentiation between stomata zone and vein zone on a young leaf. 3. Significant differentiation between stomata zone and vein zone on a developed leaf. 4. Developing stomata on a young leaf. 5. Lower leaf epidermis on a developed leaf. Figs. 6–9. Fossil Ginkgo. 6. Lower leaf epidermis of G. coriacea. 7. Lower leaf epidermis of G. huttoni. 8. Lower leaf epidermis of G. yimaensis. 9. Lower leaf epidermis of G. obrutschewii. All scale bars = 100 μm

Assessing the potential for the stomatal characters of extant and fossil Ginkgo leaves to signal atmospheric CO2 change

Chen L.-Q., Li C.-S., Chaloner W. G., Beerling D. J., Sun Q. G., Collinson M. E., Mitchell P. L. (2001)

Li-Qun Chen, Cheng-Sen Li, William G. Chaloner, David J. Beerling, Qi-Gao Sun, Margaret E. Collinson, Peter L. Mitchell,


American Journal of Botany 88: 1309–1315 –


The stomatal density and index of fossil Ginkgo leaves (Early Jurassic to Early Cretaceous) have been investigated to test whether these plant fossils provide evidence for CO2-rich atmosphere in the Mesozoic. We first assessed five sources of natural variation in the stomatal density and index of extant Gingko biloba leaves: (1) timing of leaf maturation, (2) young vs. fully developed leaves, (3) short shoots vs. long shoots, (4) position in the canopy, and (5) male vs. female trees. Our analysis indicated that some significant differences in leaf stomatal density and index were evident arising from these considerations. However, this variability was considerably less than the difference in leaf stomatal density and index between modern and fossil samples, with the stomatal index of four species of Mesozoic Ginkgo (G. coriacea, G. huttoni, G. yimaensis, and G. obrutschewii) 60–40% lower than the modern values recorded in this study for extant G. biloba. Calculated as stomatal ratios (the stomatal index of the fossil leaves relative to the modern value), the values generally tracked the CO2 variations predicted by a long-term carbon cycle model confirming the utility of this plant group to provide a reasonable measure of ancient atmospheric CO2 change.

Bennettitales pCO2 can be reconstructed based on cross-calibration of stomatal densities with those of co-occurring pCO2 responders, such as Ginkgoales

Figure 2. Cycad and fern cuticle micromorphology
A. Lepidozamia perroffskyana (L. hopei morphology is identical). B. Zamia furfuracaea. C. Dicksonia antarctica. D. Cyathea cooperi. E. Stenochlaena palustris. F. Todea barbara. All scalebars = 100 µm

Searching for a nearest living equivalent for Bennettitales: a promising extinct plant group for stomatal proxy reconstructions of Mesozoic pCO2

Steinthorsdottir M., Elliott-Kingston C., Coiro M., McElwain J. C. (2021)

Margret Steinthorsdottir
, Caroline Elliott-Kingston, Mario Coiro, Jennifer C. McElwain,


GFF 143(2-3): 190-201 -Special Issue: Advances in Swedish palaeontology; the importance of fossils in natural history collections – The Department of Palaeobiology at the Swedish Museum of Natural History –


To understand Earth´s climate variability and improve predictions of future climate change, studying past climates is an important avenue to explore. A previously published record of pCO2, across the Triassic–Jurassic boundary (TJB, ~201 Ma) of East Greenland, showed that Bennettitales (Anamozamites and Pterophyllum) responded in parallel to the empirically proven pCO2-responders Ginkgoales, reducing their stomatal densities by half across the TJB, indicating a transient doubling of pCO2. The abundance of fossil Bennettitales in Mesozoic strata and natural history museum collections worldwide offers enormous potential for further stomatal proxy pCO2 reconstructions, but a suitable nearest living equivalent (NLE) should ideally first be identified for this extinct plant group. Using specimens from herbarium collections, three species of cycads, historically considered the best NLE, were tested for pCO2 response, as well as two species of tree ferns, grown in experimental growth chambers. None responded to changes in pCO2, and were consequently rejected as NLEs. Finally, two species of ferns were selected from the literature, and produced very similar pCO2 compared to Ginkgoales. However, these understory ferns are not appropriate NLEs for Bennettitales due to differences in habitat and a distant evolutionary relationship. Future work should test additional plant groups, in particular seed plants such as basal angiosperms and Gnetales, for suitability as NLE for Bennettitales in pCO2 reconstructions, for example through biogeochemical fingerprinting using infrared microspectroscopy. Until an appropriate NLE is identified, Bennettitales pCO2 can be reconstructed based on cross-calibration of stomatal densities with those of co-occurring pCO2 responders, such as Ginkgoales.

Stomata in Podozamites harrisii, Pseudotorellia resinosa and Pseudotorellia palustris

Details: A) Podozamites harrisii; incomplete leafy shoot showing three attached leaves (left). Detail of stomatal band from abaxial leaf cuticle showing cell outlines of transversely oriented, paracytic (monocyclic) stomata (top right). Detail from adaxial leaf cuticle showing rectangular epidermal cell outlines (bottom right). B) Pseudotorellia resinosa; two isolated multiveined leaves (left). Detail of stoma showing lateral subsidiary cells and inner periclinal walls of guard cells (top middle). Detail of outer surface of abaxial cuticle showing stomatal pit with stomatal aperture (bottom middle). C) Pseudotorellia palustris; two isolated multiveined leaves (left). Detail of stoma showing lateral subsidiary cells (top right). Detail of outer surface of abaxial cuticle showing a stoma with papillae (bottom right). Scale bars: A= 1cm, 20μm, 20μm respectively; B= 5mm, 40μm, 40μm respectively; C= 1cm, 20μm, 20μm respectively. Tevshiin Govi lignite, Mongolia, ca. 125 million years before present.

Strap shaped leaf fossils from the Tevshiin Govi locality

Oak Spring Garden Foundation (2021)


May 19, 2021OSGF

The Tevshiin Govi fossil locality is a small coal mine, located approximately 220 km south of Ulaanbaatar, Mongolia. Superbly preserved plant fossils occur three dimensionally, little altered from their original shape and size. Individual plant parts can be extracted whole from the soft lignitic matrix that surrounds them. The Tevshiin Govi locality has yielded a variety of fossil plants, some similar to living conifers and filmy ferns, but others that have no close living relatives.

 Details:  TheTevshiin Govi locality (left); compressed log removed from the sediment (center); cone of Krassilovia compressed in the sediment (upper right); compressed leaf remains preserved as lignite (lower right). Tevshiin Govi lignite, Mongolia, ca. 125 million years before present.