Fossil Conifer Research Articles

Fossil conifers from the Middle Jurassic of the Northern Caucasus, Russia: female and male cones, leafy shoots and anatomically preserved wood

Fossil conifers from the Middle Jurassic of the Northern Caucasus, Russia: female and male cones, leafy shoots and anatomically preserved wood

A new species of Pseudotsuga (Pinaceae) from the lower Miocene of Lesvos, Greece, and its palaeogeographical and palaeoclimatic implications

Pseudotsuga Carrière is commonly known as Douglas-fir, a minor genus attributed to Pinaceae. Four extant species are included in this genus, with dispersed distribution in East Asia and western North America. Pseudotsuga possesses a number of fossil records of needled leaves, seed cones, and seeds. Nevertheless, few reliable fossil wood of this genus has been specifically investigated. Here, we describe some anatomically well-preserved petrified fossil wood from the lower Miocene of Lesvos Island, Greece, as Pseudotsuga lesvosensis n. sp. The studied fossil wood remains are characterized by the presence of normal axial and radial resin canals, piceoid cross-field pitting, along with distinctive helical thickenings in cell walls consistent with Pseudotsuga. The present fossil conifer further enriches the species diversity of the Miocene Petrified Forest in Lesvos. The first report of Pseudotsuga lesvosensis from the southern Europe in this study extends the tempo-spatial distribution patterns of Pseudotsuga and contributes to further understanding of its origin and evolutionary history. The occurrence of P. lesvosensis fossil wood, as well as other palaeontological macrofloral composition evidence, indicates a humid warm temperate to subtropical climatic condition during the early Miocene within the Lesvos, which differs significantly from the current Mediterranean climate.

Reconstruction of an enigmatic Pennsylvanian cone reveals a relationship to Sphenophyllales.

We studied the 3D morphology of a small, well-preserved cone from the Pennsylvanian Mazon Creek Lagerstätte to characterize its structure and determine its systematic affinity. Previously tentatively assigned to the enigmatic Tetraphyllostrobus, we show that it differs in key respects from that genus as described. We systematically compared the new fossil with relevant Paleozoic cone genera and employed advanced imaging techniques, including scanning electron microscopy, Airyscan confocal super-resolution microscopy, optical microscopy, and X-ray microcomputed tomography to visualize and reconstruct the fossil cone in 3D. The analyses demonstrate unequivocally that the sporophylls of the new Mazon Creek cone are arranged in whorls of six and have characters typical of Sphenophyllales, including epidermal cells with undulatory margins and in situ spores assignable to Columinisporites. The combination of characters, including sporophyll arrangement, anatomy, and spore type, supports the establishment of Hexaphyllostrobus kostorhysii gen. et sp. nov. within Sphenophyllales. Furthermore, we show that Tetraphyllostrobus, although originally described as possessing smooth monolete spores, actually possesses Columinisporites-type spores, indicating that it, too, was most likely a sphenophyll. The recognition of Hexaphyllostrobus contributes to our knowledge of Pennsylvanian sphenophyll diversity, and in particular increases the number of species with in situ Columinisporites-type spores. Attribution of Hexaphyllostrobus to Sphenophyllales calls into question current interpretations of Tetraphyllostrobus suggesting that future research on better-preserved macrofossil material may demonstrate a sphenophyllalean relationship.

Pinaceous evolution illuminated by additional diversity of Early Cretaceous seed cones

An anatomically preserved fossil conifer seed cone has been discovered near Ono, California, providing additional evidence for the diversification of Pinaceae during the Aptian Stage of the Early Cretaceous. The specimen was measured and photographed, and then serial anatomical thin sections were prepared by the cellulose acetate peel technique. Selected peels were mounted on microscope slides, viewed, and photographed with transmitted light microscopy. Structure of the seed cone is similar to that of living and extinct representatives of the Pinaceae in the occurrence of helically arranged and imbricating foliate bract/scale complexes consisting of a small bract that subtends an ovuliferous scale bearing two inverted winged seeds on the adaxial surface. However, details of bract/scale complex vasculature, a wing that is obviously lateral to the seed body, and distinctive histological features reveal that this cone represents a new genus of extinct Pinaceae. This new genus of fossil conifers, represented by a seed cone of unique structure, further enriches the known diversity of Early Cretaceous Pinaceae. When added to the existing record of fossil seed cones, the new genus and species, Onostrobus elongatus Rothwell et Stockey, highlights knowledge that among early-diverging lineages of Pinaceae there has been considerable Cretaceous and Paleogene evolution that is reflected by variations among subtle characters that are recognizable only from anatomically preserved specimens.

A revision of the conifer Sphenolepis kurriana (Dunker) Schenk from the Wealden of Germany and England

The scale-leaved fossil conifer Sphenolepis kurriana (Dunker) Schenk is redescribed from the Wealden floras of Germany and England. The revised study of this fossil species encompasses specimens remaining in the nineteenth century Dunker Collection in the Museum für Naturkunde, Berlin, from which a neotype is selected; figured specimens in the Museum of Geology, Georg-August-Universität, Göttingen and the Rufford Collection in the Natural History Museum, London. Dispersed samples more recently collected from debris-beds in the English Wealden show cuticular details of particularly well-preserved leaf-bases and leaves. To date, Sphenolepis kurriana (Dunker) Schenk is the only non-cheirolepidiaceous conifer species confirmed as present in both the English and German Wealden floras. In situ cones, identified as female, indicate a taxodiaceous Cupressaceae affinity for S. kurriana.

Some Features of the Shoot Systems in Representatives of the Tribe Sequoiae, Cultivated in Russia

The article focuses on the growth rates of three extant species belonging to the tribe Sequoiaceae: Metasequoia glyptostroboides, Sequoia sempervirens and Sequoiadendron giganteum. The material was collected from botanical garden collections on the Black Sea coast of the Caucasus and Crimea. During a long growing season, all three species form shoot systems of varying complexity: from unbranched shoots consisting of a single elementary shoot to sylleptically branched multi-axial systems. In S. giganteum, the shoot systems formed during an extra-bud growth period are similar to those of other Cupressaceae species and partly to those of Pinaceae. In Metasequoia glyptostroboides and Sequoia sempervirens, sylleptically branched shoot systems are differentiated into several variants: on orthotropic shoots in the upper part of the growth, plagiotropic branches are sylleptic and continue to grow after the orthotropic part of the shoot system has stopped growing. Plagiotropic sylleptic lateral shoots continue to branch into second-order lateral shoots. Similar structures are found in Araucaria and archaic fossil conifers. M. glyptostroboides and S. sempervirens have phyllomorphic branches of the same appearance as those described for Tsuga canadensis. Plagiotropic lateral sylleptic shoots continue to branch into second-order lateral shoots. Similar structures are known in Araucaria and fossil archaic conifers. M. glyptostroboides and S. sempervirens have phyllomorphic branches of the same appearance as described for Tsuga canadensis. These species are also characterized by buds formed serially below the sylleptically growing shoot. In M. glyptostroboides, the phyllomorphic branches fall off annually, and their perennial bases form a growing, basisympodially shortened shoot. The renewal bud is not located under the bark, as in Taxodium distichum.

Geographical and morphological changes of conifers in Yunnan, China during the Cenozoic in response to climatic changes

Yunnan province, known as a hot spot of plant diversity, is located in Southwest China and on the southeastern margin of the Qinghai-Tibet Plateau. Today, there are four families, 21 genera and 56 species of conifers found in Yunnan. Three families, 15 genera and 44 species of fossil conifers have been reported from the Cenozoic in Yunnan. In this study, we investigated the fossil conifers from the Cenozoic in Yunnan and their corresponding living species and evaluated the distribution and climatic conditions of the extant genera. Based on this analysis, paleoclimates of the fossils were reconstructed to determine the migration patterns of these conifers in response to climatic changes caused by the uplift of the Qinghai-Tibet Plateau. Our analyses show that the cooling trend led to a southward expansion and migration of conifers to warm and humid climate areas since the early Oligocene. In addition, the drought tendency led to the disappearance of certain conifer species from Yunnan, and the strengthening monsoon climate resulted in the migration of conifers eastward to eastern China or coastal areas, westward to western Yunnan, southeast Tibet and northern Myanmar and northward to dry and cold North China and North Korea. Likely adaptive morphological changes also occurred among the conifer species. The study also revealed that the diversity and composition of conifers in Yunnan have changed significantly since the early Oligocene with the uplift of the Qinghai-Tibet Plateau and climatic changes and that the extant lineages of Yunnan conifers appeared in the late Miocene.

Is biodiversity promoted in rift-associated basins? Evidence from Middle Jurassic conifers from the Otlaltepec Formation in Puebla, Mexico

The Jurassic Period is an important moment in the origin and evolution of modern conifer lineages. They dominated most of the land plant communities, as reported in different high latitude floras worldwide. However, there have been few reports of Middle Jurassic conifers from low latitude regions of Western Laurasia, such as Mexico. Most data on the composition of these Jurassic Mexican floras come from other plant lineages that thrived in different rift-associated basins, like the Tlaxiaco Basin and the Ayuquila Basin. Here we describe six new fossil conifers from the Middle Jurassic Otlaltepec Formation, Puebla, Mexico. Based on morphological features, we identify the following genera: Brachyphyllum, Platycladium, Podocarpites, and Masculostrobus and propose two new species (Brachyphyllum dimorpha Morales-Toledo & Cevallos-Ferriz, sp. nov. and Platycladium mexicanum Morales-Toledo & Cevallos-Feriz, sp. nov.). The description of the first ovulate cone for the Middle Jurassic of Mexico is provided, as well as a conifer foliage of uncertain affinities. Based on the available data we discuss the implications of the fossil record from the Otlaltepec Formation in context of the break-up of Pangea and how the conifer diversity seems to be increased by the rifting process through separating plant communities in different basins. Finally, this work contributes to the knowledge of conifer diversity at low latitude floras from Western Laurasia during the Middle Jurassic.

Exceptionally well‐preserved seed cones of a new fossil species of hemlock, Tsuga weichangensis sp. nov. (Pinaceae), from the Lower Miocene of Hebei Province, North China

AbstractTsuga (hemlock) is a small genus of 10 extant species in the Pinaceae, with a disjunct distribution in East Asia and eastern and western North America. Reliable species‐level identification of Tsuga fossils depends on the discovery of seed cones with intact bracts, but such cones are rare in the fossil record. Here we describe a new fossil species of hemlock as T. weichangensis sp. nov. based on exquisitely preserved seed cones with nearly complete bracts from the Lower Miocene of Weichang, Hebei Province, North China. This fossil species displays a mosaic of characters between Tsuga and Nothotsuga. The well‐developed and slightly exserted bract scales of T. weichangensis are reminiscent of Nothotsuga, but other characters, such as nonleaved peduncles and tongue‐shaped bract scales, in addition to monosaccate pollen found at the same fossil locality, suggest an affinity closer to Tsuga. Cladistic analysis based on 15 morphological characters and a molecular backbone constraint supports the assignment of these fossil cones to Tsuga rather than Nothotsuga, and places the fossil species of T. weichangensis in an unresolved polytomy within the genus Tsuga. The occurrence of Tsuga seed cone fossils indicate the paleoclimate in the Miocene of Weichang was warmer and more humid than today's climate, which is consistent with the paleoclimate reconstructed by paleopalynology.

A conifer Pagiophyllum yafraiensis sp. nov. from the Jurassic Khashm az Zarzur Formation, Yafran, Jebel Nefusa – Libya.

The Jurassic flora from the Khashm az Zarzur Formation in the vicinity of Yafran village in Jebel Nefusa, northwestern Libya was studied. Among which a new species of fossil conifer, Pagiophyllum yafraiensis sp. nov. was described and illustrated. This new species occurred in association with Piazopteris branerii, Brachyphyllum sp., Hirmerella sp., Otozamites sp., and Samaropsis sp. According to the stratigraphic position of the Khashm az Zarzur Formation dated as (Callovian-Oxfordian), however, a Late Jurassic (Bathonian-Tithonian) age has been assigned palynologically. The global paleogeographical distribution of the genus Pagiophyllum is also illustrated herein.

C30 and C31 steranes in Permian fossil conifers Protophyllocladoxylon

Steroids with alkyl groups at C-2 and C-3 are not known yet in any living organism, while 4-methylsteranes are previously thought specific to 4-methylsteroids bio-synthesized by limited types of organisms, such as dinoflagellates, microalgae, and certain bacteria. Here we investigate the occurrence of C30 2α-, 3β-, 4α-methyl-24-ethylcholestanes, C31 3β,24-diethylcholestanes, and 3,4-dimethyl-24-ethylcholestane, which are tentatively identified in fourteen fossil conifer Protophyllocladoxylon trunk samples from the upper Permian Wutonggou and Guodikeng formations in northwest China. In contrast to the paucity of alkyl steranes in the background sediments, abundant C30 4α-methyl-24-ethylcholestanes in fossil conifers from diverse fluvial–lacustrine environments suggest that conifers were the most likely biological origin for the 4-methyl steranes in conifer trunk samples, although origins from associated fungi might also be possible. Alternatively, these C-4 methyl steranes might have possible algal or prokaryotic origins. It is noteworthy that diagenetic methylation or bacterial alkylation at early stages of diagenesis during burial may have caused a re-arrangement of classical 24-ethylsterols that were bio-synthesized by plants to generate C-2 and C-3 alkylated steranes. This study reports the presence of 4-methylsteranes in conifer fossils for the first time, pointing toward a likely origin from higher plants. This study also provides the first report of C-2 and C-3 alkylated steranes in plant fossils, a.llowing for the possibility that plants may produce functionalised sterol precursors of orphan alkylsteranes that are abundant in geological sediments but whose functionalised precursors are not known from any living organisms.

Cathaya vanderburghii, a misnomer for European Neogene fossil cones

AbstractSome fossil seed cones from the European Neogene identified to the genus Cathaya and published as a fossil‐species, Cathaya vanderburghii, are shown not to belong to Cathaya. In this paper, fossil C. vanderburghii is transferred to Nothotsuga and recombined as Nothotsuga vanderburghii comb. nov. An amended diagnosis and detailed description of N. vanderburghii are given. The fossil cones are characterised by ovoid to conical shape, rhombic to suborbicular and auriculate scales, and slightly exserted ligulate‐spathulate bracts with dentate margin and acute apex.

Frenelopsis antunesii sp. nov., a new cheirolepidiaceous conifer from the Lower Cretaceous of Figueira da Foz Formation in western Portugal

Shoots of cheirolepidiaceous conifers assigned to the fossil genus Frenelopsis are very common in Portuguese Early Cretaceous mesofossil floras. In this study, a new cheirolepidiaceous conifer Frenelopsis antunesii is described from the Lower Cretaceous (upper Aptian –lower Albian) of Figueira da Foz Formation at the Carregueira site, close to the small village of Juncal, in western-central mainland Portugal. The new fossil conifer is described based on morphological characters of vegetative shoots and cuticular features. The new species, Frenelopsis antunesii, is characterised by branching segmented shoots with three leaves per node, leaf surfaces distinctly covered by trichomes, leaves with thick cuticles and stomata arranged in short rows. The stomatal apparatus is composed of four or rarely five subsidiary cells. The morphological and anatomical features documented here support the view that Frenelopsis antunesii likely grew in a semiarid to arid climate.

Leaf anatomy of Ningxiaites specialis from the Lopingian of Northwest China

Leaves are important vegetative organs of plants. However, our knowledge of fossil conifer leaves has been mostly obtained from compression or impression specimens. Compared with the abundant impression and compression leaf fossils, permineralized conifer leaf fossils with preserved cellular details are extremely rare. Therefore, leaf anatomies of fossil conifers remain poorly understood. Here, we describe permineralized leaves of a fossil conifer, Ningxiaites specialisFeng, 2012, from the Lopingian Sunjiagou Formation of Northwest China. The leaves are linear and helically arranged on shoot axis. They are characterized by a single vascular bundle surrounded by transfusion tissue, a single-layered endodermis, a thick mesophyll, and a single-layered epidermis. Tracheids in the vascular bundle exhibit helical and scalariform thickenings. The transfusion tissue is of the Pinus-type and composed of transfusion tracheids and transfusion parenchyma. The mesophyll comprises palisade and spongy tissues. The palisade mesophyll consists of thin-walled elongate cells, and is present on the adaxial side of the leaf. The spongy mesophyll comprises subcircular to subrectangular shaped cells and is present on the abaxial side. The hypodermis is discontinuously present beneath the adaxial epidermis and possesses two to three layers of sclerenchyma cells. The epidermis consists of a single layer of rectangular parenchyma covered by a thick cuticle with abundant cylindrical papillae. Stomata are predominantly present on the adaxial leaf surface and are arranged in parallel rows. This is the first report on the leaf anatomy of a Paleozoic conifer from the North China Block and sheds new light on the evolutionary history of conifers.

Evolution of the coniferous seed scale.

The Florin model is the commonly accepted theory of coniferous seed scale evolution. It describes the derivation of extant seed scale morphology from the morphology of fossil conifers via the reduction of complex to simple axillary structures. In this framework the seed scale is composed of a reduced lateral shoot with fertile and sterile appendages which are interpreted as leaf homologues. The Florin model has three crucial problems that we address here: (1) the original derivation series does not take the ontogeny of extant conifers into account, (2) it cannot explain the morphology of all extant conifers and (3) Taxaceae were originally excluded. Examination of seed cones of extant conifers shows that ovules occur in three different positions in the cone: in an axillary position, replacing a leaf or terminating the cone axis. By interpreting the fertile appendage or seed-bearing structure as a leaf, not all positions are possible. The exclusion of Taxaceae from conifers is in stark contrast to recent molecular phylogenetic studies, which include Taxaceae in conifers as sister to Cupressaceae. Therefore, the Florin model does not offer an adequate explanation for taxaceous morphology. We conclude that the seed-bearing structure of conifers cannot be interpreted as homologous to a leaf. In the interpretation we present here, the seed-bearing structure is the modified funiculus of the ovule, multiples of which laterally fuse to form the seed scale. The seed scales of all extant conifers can be derived from a Cunninghamia-like morphology via fusion and reduction of individual funiculi.

Early Cretaceous abietoid Pinaceae from Mongolia and the history of seed scale shedding.

Seed cones of extant Pinaceae exhibit two mechanisms of seed release. In "flexers" the cone scales remain attached to the central axis, while flexing and separating from each other to release the seeds. In "shedders" scales are shed from the axis, with the seeds either remaining attached to the scale or becoming detached. The early fossil history of Pinaceae from the Jurassic to Early Cretaceous is dominated by flexing seed cones, while the systematic information provided by shedding fossil cones has been overlooked and rarely integrated with data based on compression and permineralized specimens. We describe the earliest and best-documented evidence of a "shedder" seed cone from the Aptian-Albian of Mongolia. Lignite samples from Tevshiin Govi locality were disaggregated in water, washed, and dried in air. Fossils were compared to material of extant Pinaceae using LM and CT scans. Lepidocasus mellonae gen. et sp. nov. is characterized by a seed cone that disarticulated at maturity and shed obovate bract-scale complexes that have a distinctive ribbed surface and an abaxial surface covered with abundant trichomes. The ovuliferous scale has ca. 30-40 resin canals, but only scarce xylem near the attachment to the cone axis. Resin vesicles are present in the seed integument. Phylogenetic analysis places Lepidocasus as sister to extant Cedrus within the abietoid grade. The exquisite preservation of the trichomes in L. mellonae raises questions about their potential ecological function in the cones of fossil and living Pinaceae. Lepidocasus mellonae also shows that a shedding dispersal syndrome, a feature that has often been overlooked, evolved early in the history of Pinaceae during the Early Cretaceous.

Ovulate Cones of Schizolepidopsis ediae sp. nov. Provide Insights into the Evolution of Pinaceae

Premise of research. The extinct conifer genus Schizolepidopsis is characterized by deeply bilobed ovuliferous scales bearing two adaxial seeds. Although it is frequently placed in Pinaceae, the evidence for a close relationship with the family is mixed. Resolving the affinities of Schizolepidopsis has important implications for the age of Pinaceae because putative reports of the genus extend into the Late Permian. We describe a new species, Schizolepidopsis ediae sp. nov., based on specimens from the Lower Cretaceous of Mongolia and Inner Mongolia, China, that represent the first anatomically preserved occurrences of Schizolepidopsis.Methodology. Specimens were studied using light microscopy, cellulose acetate peels, and X-ray micro–computed tomography. To test relationships between Schizolepidopsis and Pinaceae, we performed conifer-wide phylogenetic analyses that included 10 previously described fossil conifers using DNA sequence data and a new morphological matrix of ovulate reproductive characters. Analyses were performed using Bayesian total evidence and parsimony backbone approaches.Pivotal results. Schizolepidopsis ediae possesses key characters of Pinaceae, including those related to pollination biology. Most analyses placed S. ediae in crown group Pinaceae (abietoid clade), with all other Schizolepidopsis species forming a grade along the Pinaceae stem. Uncertainty in the data indicates that stem group affinities of S. ediae are also possible.Conclusions. Schizolepidopsis ediae provides the first conclusive evidence linking Schizolepidopsis with extant Pinaceae. The phylogenetic relationships between extant Pinaceae and Schizolepidopsis suggest that seed wings evolved along the Pinaceae stem and not with the crown group and that, in combination with developmental genetic evidence, the simple ovuliferous scales of Pinaceae likely evolved from bilobed ovuliferous scales like those of Schizolepidopsis. More broadly, this study provides evidence of a Mesozoic Pinaceae stem group that might extend into the Paleozoic, helping to reconcile the ancient stem divergence of Pinaceae with its relatively recent crown age.

First fossil record of Nothotsuga (Pinaceae) in China: implications for palaeobiogeography and palaeoecology

ABSTRACT Nothotsuga is a monotypic genus of Pinaceae endemic to southern China today. Molecular data indicate that Nothotsuga split from Tsuga during the Palaeogene with the earliest fossils from the upper Eocene of North Europe. However, Nothotsuga fossil has not been reported from China. Here, we describe several well-preserved seed cones from the upper Miocene of Tiantai County, Zhejiang Province, China. The fossil cones are characterised by ovate to elliptic shapes, rhombic to suborbicular and auriculate scales, and exserted subspathulate bracts with dentate margin and acute or acuminate apical cusp. These cones are ascribed to a new species Nothotsuga sinogaia sp. nov. based on detailed comparisons with all extant genera of Pinaceae. The present discovery indicate that Nothotsuga had a more northern distribution during the late Miocene and the increased annual range of monthly-mean temperature might have restricted its modern distribution to several scattered and fragmental areas in southern China.

Seed cones of Tsuga (Pinaceae) from the upper Miocene of eastern China: Biogeographic and paleoclimatic implications

Six well-preserved seed cones of Tsuga with fine bract-scale complexes were discovered from the late Miocene (Tortonian; 9.2–10.8 Ma) deposits of the Shengxian Formation at the border of Ninghai and Tiantai County, Zhejiang Province, eastern China. The fossil cones possess ovate to elliptic shape, spirally arranged and obovate-orbicular ovuliferous scales, and cuneate-rhombic bracts hidden behind the scales with 2-lobed apex. Based on detailed comparison with extant and fossil cones of Tsuga, the present fossils are assigned to Tsuga cf. dumosa (D. Don) Eichler. The discovery of the fossil cones indicate that Tsuga had a wider distribution during the late Miocene than at the present. The increase of the difference in temperature between the coldest and warmest months since the late Miocene had forced Tsuga to retreat from eastern Zhejiang.

The Ancestral Conifer Cone: What Did It Look Like? A Modern Trait-Evolution Approach

Premise of research. Seed conifer cones and their fossil record have been the subject of intensive study over the past century. In those studies, however, the interpretation of fossil cones differs...