Fossil Leaf Research Articles

New records for the Middle Siwalik flora of eastern Nepal and their climatic significance

The Siwalik plant fossils are important in understanding the climate change caused by the uplift of the Himalaya. The plant fossil assemblages are abundantly known from Nepal's central and western Siwalik sediments. However, they are poorly known from the Siwalik of the eastern region from where the modern Indian Summer Monsoon (ISM) enters Nepal. That is why fossils of this region are important in understanding the evolutionary history of ISM in Nepal. In the present communication, we report four new fossil leaf impressions/ compressions, namely Thelypteridaceophyllum tertiarum Joshi and Mehrotra of the family Thelypteridaceae, Calophyllum suraikholaensis Awasthi and Prasad of the Calophyllaceae, Albizia siwalica Prasad of the family Fabaceae, and Daphnogene makumensis Mehrotra, Dilcher et Lott of the family Lauraceae from the well-dated Middle Siwalik (∼9.5 Ma) sediments of eastern Nepal. The aforementioned and previous fossil records suggest that seasonal or monsoonal rainfall was present during the deposition of the sediments.

Fig leaf from the Middle Siwalik sediments of eastern Nepal with implication on biogeography and palaeoclimate

The Siwalik flora is important in understanding the orogeny of the Himalayas and the resulting climate change. Though the fossil records from the eastern Himalayan Siwalik of Nepal are sparse, we report a fossil leaf impression/ compression of Ficus precunea Lakhanpal from the Middle Siwalik (upper Miocene–lower Pliocene) sediments of eastern Nepal. The characteristic leaf venation pattern and morphological details suggest its strong affinity with the extant species of F. semicordata Buch.-Ham. ex Sm. The fossil assemblage indicates the presence of seasonal forests during the depositional period in the region.

An inclusion of Melastomataceae leaf from the Miocene amber of Simojovel de Allende, Chiapas, México

Melastomataceae Jussis a family well represented in tropical biomes and is characterized by a distinctive venation pattern in its leaves. The worldwide fossil record consists mainly of leaves that date back to the Palaeocene. However, this family is poorly represented in the fossil record in Mexico. Here, we show a new finding of a Melastomataceae leaf preserved as inclusion in amber outcrops in Chiapas that preserves evidence of the complex Miocene ecosystem through well-preserved fossil organisms. The morphological characteristics described were based on shape and venation patterns and compared with extant or fossil organisms with similar patterns, allowing us to assign individuals to one of the genera and species hypotheses, or name them as a new species. The fossil leaf has ovate to elliptical lamina, nanophyll size, long petiole, and basal acrodromous venation, with one pair of secondaries emerging from the petiole and merging at the leaf apex and opposite percurrent epimedial tertiary veins. This combination of characteristics are typical of Miconia Ruiz & Pavón and have not been observed together in any leaf recordings for this family, proposing a new fossil species. This discovery confirms the presence of Melastomataceae in Southern Mexico during the Miocene, which was once part of the tropical rainforest of the Simojovel Formation of Chiapas, Mexico.

Re-investigation of the Mesozoic cycad genus Chilinia: Fossil record, diversity, spatio-temporal distribution, and palaeoclimate implications

Chilinia is an extinct genus of cycads, established by Li and Ye in 1964 based on leaf fossils from the Lower Cretaceous in Jilin Province, China. Morphologically, the genus Chilinia closely resembles Ctenis, another cycad foliage genus, in having pinnately divided leaves with laterally inserted pinnae on the rachis and reticulate venation but differs mainly from the latter in having toothed or irregularly lobed rather than entire-margined pinnae. Fossil records show that up to now, nine species of Chilinia have been reported worldwide, representing an index fossil plant in the Jurassic to Early Cretaceous. In this study, we present a comprehensive overview of all reported Chilinia fossils from a systematic palaeobotanical perspective. Fossil records indicate that Chilinia mainly occurred in the middle–high latitudes of the northern and southern hemispheres in Pangea from the Middle Jurassic to Middle Cretaceous. Combined evidence from the morphology of Chilinia and its floral patterns suggests that the genus probably lived in humid warm-temperate palaeoclimatic conditions with brief seasonal variations.

The robustness of some Carboniferous fossil leaf venation networks to simulated damage.

Biological networks vary widely in their architecture and functional properties. Branching networks are good for transportation efficiency, while networks including loops offer good resistance to damage, and examples of these two topologies are found in leaf venation networks. The first plants with reticulate (loopy) leaf venation evolved in the Pennsylvanian of the Carboniferous, but the responses of different venation network architectures from this time period to damage are currently largely unknown. Here we address this issue with a computational analysis of venation network robustness that is focused on fossil leaves from the Pennsylvanian. We attacked fossil venation networks with simulated damage to individual vein segments and leaf blades. For both types of attack, branched venation networks are the least robust to damage, with greater robustness shown by the net-like reticulate networks found in the Pennsylvanian. A living angiosperm Betula alba was the most robust in our analysis. This may highlight a role for resistance to damage in the evolution of reticulate leaf venation in the Carboniferous, but further work is needed to answer the broader question of why reticulate leaf venation first evolved in the Pennsylvanian.

The relationship of plant leaf δ13Cn-alkanes and salinity in coastal ecosystems applied to palaeobotany: Case study from the Cenomanian of the Bohemian Cretaceous Basin, Czechia

Stable carbon isotopes in fossil leaf cuticles (n-alkanes, δ13Cn−alkanes) extracted from the sediment are widely used for palaeoenvironmental reconstructions. This approach relies on a series of assumptions (such as the plant-group-specific isotopic range, or the atmospheric CO2 being the major factor for the isotopic values) and leaves out the complexity of the carbon isotope fractionation within the plant through time, space, and different environments. The leaf cuticle is a unique archive of local environmental conditions, which has the potential to constrain individual plant habitat. To explore the applicability of the information gained from the δ13Cn−alkanes from fossil plants, a fossil coastal environment was studied.During the Cenomanian (100.5–93.9 Ma), the basal part of the Bohemian Cretaceous Basin, including locality Pecínov (Czechia), was formed as a result of sea transgression to the Palaeozoic Bohemian Massif triggered by the Alpine orogenesis. Coastal halophytic vegetation growing in this zone of prograding sea has no extant equivalent, and there are uncertainties associated with vegetation distribution or individual taxa habitat.Therefore, we examine the relationship between δ13Cn−alkanes extracted from individual leaves of coastal C3 plants (fossil and modern) and osmotic stress (salinity and drought) to reconstruct the individual plant habitat, thus, vegetation distribution in the coastal zone. We investigated modern mangrove and salt marsh vegetation in New Zealand and the United Kingdom, respectively, as well as transition zones (mangrove invading original salt marshes) for δ13C, soil moisture and salinity to build a calibration of the relationship, which is then applied to the Cenomanian fossil leaves from the locality of Pecínov.We found a positive correlation between water stress (caused by salinity or drought) and the δ13C values of n‐C25, n‐C27, n‐C29 and n‐C31 alkanes when combining all species from all modern localities. However, the absence of a strong correlation within individual species suggests a combination of several factors controlling the carbon isotopic composition. Nevertheless, the general response of δ13C to osmotic stress can be applied to compare the habitat of modern and fossil coastal plants. Thus, by using this relationship, we reconstructed the relative salinity and water stress of individual species of the Cenomanian plants by relating them to modern species-specific ranges of n‐C29 isotopic signatures.We showed that the δ13Cn−alkanes of fossil plant cuticles/leaves can be a valuable tool in the reconstruction of plant habitat and help us understand evolution of fossil environments in time and space. Additionally, our data further confirm that the δ13C acquired from plants should be used with caution when reconstructing global atmospheric CO2 because the osmotic stress can shift the δ13C in plants growing in terrestrial environments, particularly in coastal sea-influenced ecosystems.

First flower inclusion and fossil evidence of Cryptocarya (Laurales, Lauraceae) from Miocene amber of Zhangpu (China)

Lauraceae have one of the oldest fossil records of angiosperms with the earliest known evidence from the mid-Cretaceous. However, most of these records are based on leaves, especially from the Cenozoic of Asia, which are often challenging to assign to extinct or extant genera or species. In contrast, fossils of reproductive organs are more informative, but remain scarce. We here described the first Cenozoic Lauraceae flower of Asia and confirmed the presence of Cryptocarya in the Miocene Zhangpu flora (Fujian Province, south-eastern China) based on an amber inclusion. We scanned the specimen using synchrotron radiation-based micro-computed tomography (SRμCT) and then compared the fossil with extant flowers of the genus. The present fossil flower is small, bisexual, and polysymmetric, with a whorled and trimerous perianth and androecium along with a hypanthium around the gynoecium. The perianth comprises six undifferentiated tepals, the androecium consists of nine stamens and three innermost staminodes, and the gynoecium of a single carpel with a superior, unilocular (and uniovulate) ovary. Our study also shows that the fossil shares an unusual position of the typical staminal glands and a short androecial tube on the rim of the hypanthium with at least one extant Australian species of Cryptocarya, which have not been reported before. Nowadays, Lauraceae are still present in tropical to subtropical regions, mostly in American and Asian rainforests. The discovery of many Lauraceae leaf fossils in Zhangpu, as well as the amber flower of this study, is consistent with the current reconstruction of the amber source environment as a megathermal seasonal rainforest during the Mid-Miocene.

Putative Celtis Leaves from Eocene Patagonia are Allied with Asian Anacardiaceae

The most common macrofossils in the highly diverse flora from Laguna del Hunco (early Eocene of Chubut, Argentina) are “Celtis” ameghinoi leaves, whose true affinities have remained enigmatic for a century. The species accounts for 14% of all plant fossils in unbiased field counts and bears diverse insect-feeding damage, suggesting high biomass and paleoecological importance. The leaves have well-preserved architecture but lack cuticles or reproductive attachments. We find that the fossils only superficially resemble Celtis and comparable taxa in Cannabaceae, Ulmaceae, Rhamnaceae, Malvaceae, and many other families. However, the distinctive foliar morphology conforms in detail to Dobinea (Anacardiaceae), a genus with two species of shrubs and large herbs ranging from India’s Far East and Tibet to Myanmar and central China, and we propose Dobineaites ameghinoi (E.W. berry) gen et. comb. nov. for the fossils. This discovery strengthens the extensive biogeographic links between Eocene Patagonia and mainland Asia, provides the first fossil record related to Dobinea, and represents a rare Gondwanan macrofossil occurrence of Anacardiaceae, which was widespread and diversified in the Northern Hemisphere at the time. The diverse leaf architecture of Anacardiaceae includes several patterns usually associated with other taxa, and many other leaf fossils in this family may remain misidentified.

Evidence for the evolutionary history and diversity of fossil sweetgums: leaves and associated capitate reproductive structures of Liquidambar from the Eocene of Hainan Island, South China

AbstractExtant species of Liquidambar L. exhibit a disjunct distribution between western and eastern Asia and eastern North America to Central America, with the highest species diversity being in China. In this study, two new species of Liquidambar are described from the Eocene of Hainan Island, South China: L. hainanensis on basis of the leaf fossils, and L. ovoidea based on compressions of infructescences. The co‐occurrences of L. hainanensis leaves, associated infructescences of L. ovoidea and dispersed pantoporate pollen grains have the combination of morphological features peculiar to the genera Liquidambar and former Semiliquidambar and Altingia. This is considered further palaeobotanical justification for the placement of these three genera into a single genus, Liquidambar, proposed earlier based on molecular markers. Our data provide evidence for the occurrence of an ancestral polymorphic group of Liquidambar species (L. maomingensis with associated capitate infructescences, L. bella, L. hainanensis and L. ovoidea) during the Eocene in South China, and corroborate the view that South China could have been a centre of Liquidambar speciation during the Eocene. The morphological similarity of L. hainanensis leaves to those of the extant species L. orientalis from Western Asia and the North American L. styraciflua may support the importance of both the North Atlantic Land Bridge and the Bering Land Bridge for the dispersal of Liquidambar. Analysis of fossil species of Liquidambar from eastern Asia also contributes to further understanding of patterns in the taxonomic diversity and evolutionary history of this genus.

Calophyllum (Calophyllaceae) from late Oligocene–Early Miocene of Li Basin, northern Thailand and its biogeographic and paleoclimatic implications

Fossils from tropical Asia, which are far from fully investigated, are important for understanding the evolution of plant diversity and the associated surrounding environment there. In this study, we report, as the first record in Thailand, the well-preserved leaf fossils of Calophyllum Linnaeus (Calophyllaceae) from the upper Oligocene–Lower Miocene lacustrine deposits in Li Basin, northern Thailand. The fossils were identified through detailed comparison with leaves of extant and fossil species. These leaf fossils are assigned to Calophyllum based on several key leaf characteristics such as oblanceolate or oblong in shape, and, dense parallel secondary veins. Based on detailed morphological comparison, these fossil leaves are assigned to C. suraikholaensis Awasthi and Prasad, 1990 and Calophyllum sp. The discovery of Calophyllum indicates a montane subtropical to tropical climate in northern Thailand during the Oligocene–Miocene. Together with previous fossil records, these results suggest that this genus probably originated in India during the Paleogene, and spread from India to Indochina during the Neogene, leading to its modern distribution, which currently prefers tropical climates.

Latest Neogene Paleoclimate Variation in Yunnan, Southwest China, Revealed by Fossil Leaf Physiognomy

AbstractYunnan Province, located in the southeastern margin of the Tibetan Plateau, can provide important information on how climate change was influenced by global cooling. However, its variation patterns in temperature and precipitation during the latest Neogene are not well‐understood. Based on the 357 specimens assigned to 31 morphotypes of plant fossils from the upper Pliocene Ciying Formation in Yiliang County, Yunnan Province, Southwest China, paleoclimate was estimated by Leaf Margin Analysis and Climate Leaf Analysis Multivariate Program. Compared to the present climate, the mean annual temperature and coldest month temperature have not changed significantly since the late Pliocene, whereas the warmest month temperature has decreased significantly. All precipitation‐related parameters have decreased, particularly winter precipitation. Combined with the climatic data of the same period in other areas of Yunnan, the western and eastern Yunnan has shown a similar pattern in temperature variation since the late Pliocene except for central Yunnan; whereas the variation in precipitation does not follow a common law except for a consistent decrease in winter precipitation. Our study reinforced the fact that under the background of global cooling and intensified monsoon systems, different areas of Yunnan exhibit different climatic responses to these changes because of their topographic heterogeneities.

A new extinct conifer Brachyoxylon from the Middle Jurassic in southern China: Wood anatomy, leaf phenology and paleoclimate

The Jurassic System in the Sichuan Basin of eastern Asia is represented by the extensive development of massive thick red beds, mainly composed of purplish-red sandstones and mudstones. Abundant invertebrate and vertebrate fossils have been recovered from these Jurassic red beds. However, fossil woods are much less documented. Here, we describe fossil woods from the Middle Jurassic Shaximiao Formation at Qijiang of Chongqing City in southeastern Sichuan Basin, China, obtaining typical Brachyoxylon anatomy with mixed radial tracheid pitting and araucarioid cross-field pitting. Owing to a novel combination of radial tracheid pitting, cross-field pitting and ray height, a new species, Brachyoxylon qijiangense Xie, Wang et Tian sp. nov. is recognized here. Based on the tree mean sensitivity and leaf retention time analysis, along with the comparison with other invertebrate and leaf fossils in the Shaximiao Formation, the new fossil woods bearing true growth rings with abundant, well-formed earlywood and extremely narrow latewood indicates that B. qijiangense sp. nov. was an evergreen tree growing in a warm and humid climate with mild seasonality during the Middle Jurassic in Qijiang, probably in a flooding-disturbed, streamside condition.

A multistage model of preservation in fossil plants from the Llewellyn Formation (Pennsylvanian), St. Clair, Pennsylvania, U.S.A

Exceptionally preserved plant fossils from St. Clair, Pennsylvania, have long been part of museum and private collections. Fossil leaf fragments and stems from the underclay of the Buck Mountain Coal (Reading Anthracite Company quarry), lowest Llewellyn Formation (late Pennsylvanian, Virgilian), combine outer layers of coalified organic material (phytoleim) with strikingly white kaolinite, quartz, and the low-grade metamorphic mineral pyrophyllite in the interior. The surficial dark, coalified material appears to preserve the dense outer layers (cuticle, epidermis, and palisade layer) and some cells of the spongy mesophyll in the fossilized leaves. XRD spectra of separated phytoleim contain graphite peaks. Raman spectra with peaks near 1600 and 1320 cm−1 indicate that the phytoleim is composed of disordered graphitic material. ID/IG ratios from ca. 0.3 to 0.45 are consistent with greenschist facies metamorphic conditions forming the anthracite coal. The interior pyrophyllite is highly crystalline, with large crystals often oriented perpendicular to leaf surfaces. Hydrothermal formation of pyrophyllite requires relatively limited groundwater flow conditions and temperatures between ca. 275 and 350 °C. Although many fossil leaves are compressed, some are near their original thickness. We infer that the remains were replaced prior to significant burial and compression of the sediment by an early-forming mineral phase, possibly pyrite, which was in turn replaced by kaolinite and then pyrophyllite at higher temperature and pressure. Woody structures such as cuticle and veins, which had resisted replacement by the initial low temperature phase, were coalified at higher temperatures.

How similar are the venation and cuticular characters of Glossopteris, Sagenopteris and Anthrophyopsis?

Venation architectures and cuticular micromorphology of leaf fossils play important roles in higher-level taxonomic segregation, as these characters are broadly fixed within major plant clades. Three common fossil plant taxa are characterized by similar-shaped leaves or leaflets and anastomosing venation to such an extent that examples have commonly been assigned to the wrong taxon in past studies where fragmentary or ill-preserved material is available. We use standardized descriptions of vein cross-connection types and stomatal features to compare and contrast the venation patterns and stomatal architectures of these genera. Our reanalysis of the macro- and micromorphology of Glossopteris, Sagenopteris and Anthrophyopsis leaves reveals important differences that help segregate these taxa even on the basis of incomplete specimens. Anthrophyopsis has distinctive alignments of vein cross-connections in the outer lamina and paracytic stomata consistent with those of Bennettitales. Glossopteris has perigenous and monocyclic—normally stephanocytic to actinocytic—stomata commonly protected in pits or by overarching papillae. Sagenopteris has more consistently evanescent midribs and surficial anomocytic or stephanocytic stomata with weakly modified subsidiary cells. Considering the putatively close relationship of glossopterids (Glossopteris), Caytoniales (Sagenopteris) and Bennettitales (here encompassing Anthrophyopsis) resolved as members of the ‘glossophyte’ clade in some past phylogenetic studies, cuticular features suggest that these groups are not closely related. In addition, anastomosing venation, superficially similar to that of Glossopteris, Sagenopteris and Anthrophyopsis appears to have arisen independently in numerous other plant groups suggesting that this character has ecological or physiological benefits and is strongly prone to homoplasy.

Modelling Climate Using Leaves of Nothofagus cunninghamii—Overcoming Confounding Factors

Fossil leaf anatomy has previously been used as a proxy for paleoclimate. However, the exposure of leaves to sun or shade during their growth can lead to morphotype differences that confound the interpretation of fossil leaf anatomy in relation to climate and prevent reliable paleoclimate reconstruction. This work aims to model the differences in leaf anatomy that are due to various climatic drivers and differences attributable to sun or shade positions, using Nothofagus cunninghamii as the model species. Leaves from the sun and shade parts of three trees have been sampled from each of 11 sites in Victoria and Tasmania, Australia. The gross morphological and cuticular features have been scored and modelled with climate data from the sites. Random forest models can accurately predict Nothofagus cunninghamii contemporary climatic conditions of the spring temperature and summer rainfall based on leaf anatomical measurements. Leaf area, stomatal density and epidermal cell density are the most accurate predictors of whether a leaf grew in the sun or shade. Leaf area is also the strongest predictor of the maximum and minimum spring temperatures and rainfall. The models have implications for the use of fossilised leaves in paleoclimate reconstruction. The models we have built can be used to effectively predict whether a fossil leaf was from a sun or shade position on the tree and thus enable more reliable inference of paleoclimate by removing the confounding issues of variable leaf anatomy due to sun exposure during growth. Finally, these models could conceivably be used to make predictions of past paleoclimatic conditions provided suitable training and validation data on climatic conditions are available.

Past climates and plant migration – the significance of the fossil record

This article is a Commentary on Denk et al. (2023), 238: 2668–2684.

Marginal leaf galls on Pliocene leaves from India indicate mutualistic behavior between Ipomoea plants and Eriophyidae mites

We report a new type of fossil margin galls arranged in a linear series on dicot leaf impressions from the latest Neogene (Pliocene) sediments of the Chotanagpur Plateau, Jharkhand, eastern India. We collected ca. 1500 impression and compression leaf fossils, of which 1080 samples bear arthropod damage referable to 37 different damage types (DT) in the ‘GuidetoInsect(andOther)DamageTypesinCompressedPlantFossils’. A few leaf samples identified as Ipomoea L. (Convolvulaceae) have specific margin galls that do not match any galling DT previously described. This type of galling is characterized by small, linearly arranged, irregular, sessile, sub-globose, solitary, indehiscent, solid pouch-galls with irregular ostioles. The probable damage inducers of the present galling of the foliar margin might be members of Eriophyidae (Acari). The new type of gall suggests that marginal gall-inducing mites on leaves of Ipomoea did not change their host preference at the genus level since the Pliocene. The development of marginal leaf galling in Ipomoea is linked to extrafloral nectaries that do not offer protection against arthropod galling but indirectly protect the plant against herbivory from large mammals.

(2946) Proposal to conserve the name Iris latifolia (Mill.) Voss (Iridaceae) against I. latifolia Heer (fossil Iridaceae)

(2946) Proposal to conserve the name <i>Iris latifolia</i> (Mill.) Voss (<i>Iridaceae</i>) against <i>I. latifolia</i> Heer (fossil <i>Iridaceae</i>)

An efficient method for estimating vein density of Glossopteris and its application

AbstractGlossopteris‐type leaves are the most abundant floristic element from the Gondwanan continent and are recorded throughout the Permian, which was a period of extreme icehouse‐to‐hothouse climatic global change. Fossil leaf traits can be useful for the reconstruction of palaeoenvironments and identification of climatic changes throughout geological time, but the conservative morphology of Glossopteris leaves has thus far made them difficult to use for this purpose. If the characters of Glossopteris can be better quantified then it should make them useful for tracking environmental changes over a wide geographical area and over a long time interval. Venation density is a highly variable leaf trait that might be useful for this purpose. This trait can be calculated, usually as vein length per centimetre squared, but this can be a time‐consuming procedure. In this paper we propose a new rapid method to estimate venation density in a conical sector of Glossopteris leaf lamina using an accurate linear model whose predictors are three linear venation densities, measured as veins per centimetre. In addition to substantially reducing the data collection time, it is less biased and more reproducible than methods applied previously with this leaf type. Using this more robust method, preliminary results significantly distinguish the venation densities of leaves produced in wet and drier ecosystems, matching a pattern similar to modern plants. This is the first survey using a large sample size to reveal that environmental stress controlled the vein architecture of Palaeozoic plants, in a manner similar to plants in modern ecosystems.

Leaf fossils show a 40-million-year history for the Australian tropical rainforest genus Megahertzia (Proteaceae)

Leaf fossils show a 40-million-year history for the Australian tropical rainforest genus Megahertzia (Proteaceae)