Bract-scale Complexes Research Articles

Cunninghamia taylorii sp. nov., a Structurally Preserved Cupressaceous Conifer from the Upper Cretaceous (Campanian) Horseshoe Canyon Formation of Western North America

The fossiliferous ironstone deposits of the Upper Cretaceous Horseshoe Canyon Formation in the Drumheller badlands, Alberta, Canada, contain a diverse, anatomically preserved flora. Within this assemblage occur abundant stems, leafy shoots, leaves, ovuliferous cones, and pollen cone clusters that are here described as a new species of Cunninghamia. The stems have persistent leaf bases and plagiotropic branching. Some stems show several growth increments, and the cortex and pith are made up of resin canals, large parenchymatous cells, and lysigenous cavities. Leafy shoot axes have parenchymatous cells, resinous cells, lysigenous cavities, and resin canals within the cortex and pith. The leaves are helically arranged, lanceolate to falcate, with two abaxial stomatal bands, a large central resin canal, and two smaller lateral canals. The ovuliferous cones have numerous helically arranged bract scale complexes. The bracts and three-lobed ovuliferous scale are variously ornamented. Anatomical features of bract...

The seed cone Eathiestrobus gen. nov.: Fossil evidence for a Jurassic origin of Pinaceae

Pinaceae and nonpinoid species are sister groups within the conifer clade as inferred from molecular systematic comparisons of living species and therefore should have comparable geological ages. However, the fossil record for the nonpinoid lineage of extant conifer families is Triassic, nearly 100 million years older than the oldest widely accepted Lower Cretaceous record for Pinaceae. An anatomically preserved fossil conifer seed cone described here extends the stratigraphic range of Pinaceae nearly 30 million years, thus reducing the apparent discrepancy between evidence from the fossil record and inferences from systematic studies of living species. Material was prepared as serial thin sections by the cellulose acetate peel technique, mounted on microscope slides, and viewed and photographed using transmitted light. A large cylindrical cone consisting of bract-scale complexes that diverge from the cone axis in a helical phyllotaxis has bracts and scales that separate from each other in the midregion and are of equal length and of nearly equal width. The cone has two inverted and winged seeds that are attached to the adaxial surface of each cone scale and, thus, represents an early member of the Pinaceae. Eathiestrobus mackenziei gen. et sp. nov. extends the fossil record for well-documented members of the family Pinaceae from the Lower Cretaceous to the Kimmeridgian Stage of the Upper Jurassic. This species also clarifies the set of characters that are diagnostic for seed cones of Pinaceae and reveals possible plesiomorphic characters for seed cones of the family.

The conifer Araucaria bladenensis and associated large pollen and ovulate cones from the Upper Cretaceous Ingersoll shale (Eutaw Formation) of Alabama

Araucarian conifer remains from the Upper Cretaceous Ingersoll shale Konservat-Lagerstätte (Eutaw Formation) of Alabama include shoots of Araucaria bladenensis, an associated pollen cone, an ovulate cone, and an isolated bract-scale complex that were probably produced by the same plant species. Well-articulated A. bladenensis specimens with preserved cuticles reaffirm the original generic determination and show similarity to branches of the extant species A. bidwillii. The large pollen cone is remarkable as the earliest example comparable in size and pollen sac number to those of the largest extant Araucaria species. The co-occurrence of this cone with Upatoia barnardii in the Eutaw Formation also demonstrates that typical, small araucarian fossil pollen cones coexisted during the Late Cretaceous with modern appearing, large-coned species. The intact ovulate cone is large and ovoid but poorly preserved. An associated bract-scale complex displays lateral wings and a ligule. Comparisons with other fossil and extant araucarian conifers indicate affinity with section Bunya, making this the first North American record of the section. These fossils reaffirm that araucarian conifers were a significant component of the southeastern US Cretaceous flora, and provide a temporal and biogeographic context for the currently unexplained transition from small to large pollen cones in the family.

Early Oligocene Callitris and Fitzroya (Cupressaceae) from Tasmania

This paper documents Early Oligocene fossilized foliage and ovulate cones from Lea River, Tasmania and identifies them as belonging to two extant southern hemisphere Cupressaceae genera, Callitris and Fitzroya. Most importantly, it sheds some light on evolutionary trends within Callitris, a genus with numerous extant Australian species and two extant New Caledonian species. Callitris has a very poor fossil record and, because of the present absence of a molecular data set that includes all species, its phylogeny remains somewhat ambiguous. Although Fitzroya foliage has previously been described from a number of Tasmanian sites, this is the first recording of fertile material. The ovulate cones of the Callitris and Fitzroya macrofossils are characterized by bract-scale complexes in two whorls of three and are subtended by scale-like leaves in whorls of three. The fossilized foliage specimens consist of scale-like leaves in whorls of three. These morphological characteristics are only exhibited by three extant southern hemisphere cupressaceous genera, Callitris, Actinostrobus, and Fitzroya. The assignment of the fossils to extinct Callitris and Fitzroya species is made by comparisons with species from these three extant genera. Although much of the Lea River flora are wet rainforest taxa, the Callitris fossils have characteristics of both wet- and dry-adapted extant species.

A new species of Tsuga (Pinaceae) from the middle Eocene of Axel Heiberg Island, Canada, and an assessment of the evolution and biogeographical history of the genus

The fossil record of Tsuga (Endl.) Carrière (Pinaceae) indicates that the genus was distributed throughout North America and Eurasia from the Late Cretaceous to the Plio-Pleistocene. Examination of the spatial and temporal distribution patterns of Tsuga fossils indicates that the exchange of representatives between North America and Europe occurred across the North Atlantic land bridges prior to their demize at the end of the Eocene, while exchange between North America and Asia occurred throughout the Cenozoic across the Beringian Corridor. The discovery of well-preserved seed cones of Tsuga swedaea sp. nov. from the middle Eocene (Lutetian/Uintan; 41.3–47.5 Myr) sediments of the Buchanan Lake Formation at Napartulik, Axel Heiberg Island, Canadian High Arctic provides a basis for re-assessment of the fossil record of the genus and an evaluation of the variability of morphological features seen in this taxon. Assignment of these fossil seed cones to the genus Tsuga is based almost entirely on a suite of anatomical features seen in the fossils that have been deemed diagnostic from studies of extant representatives of the genus. Among living representatives of Tsuga, species discrimination is based mainly on the morphological features of the leaves, seed cones and shoots. However, the degree of inter- and intraspecific variability of the characters examined among living representatives of Tsuga is considerable, which has made species-level circumscription and interpreting phylogenetic relationships within the genus difficult. Examination of the bract-scale complexes of T. swedaea and those of all extant species of Tsuga indicates that bract morphology, together with the ovuliferous scale morphology is distinct for each species and useful for species-level circumscription. Based on anatomical and morphological characters of the seed cones and bracts, those of T. mertensiana (Bong.) Carrière most closely resemble the fossil seed cones. However, the differences between T. swedaea, T. mertensiana and all other species of fossil Tsuga cones described in the literature are significant and allow for the erection of a new fossil species. Consideration of the entirety of the fossil record of Tsuga indicates that the earliest representatives of the genus closely resembled T. mertensiana and that diversification of the genus occurred mainly during Miocene and Pliocene time as global climate cooled and new habitats formed in response to major orogenic events.

Reconstruction of the Jurassic conifer Sewardiodendron laxum (Taxodiaceae)

Compressed seed cones and pollen cones of Sewardiodendron laxum are described from the Middle Jurassic of Yima, Henan, central China. They are either organically attached to or associated with leafy shoots. Seed cones are terminally borne. Each cone is ovate to elongated, up to 6.5 cm long and 3.5 cm wide, and consists of a stout axis and numerous helically arranged bract-scale complexes. The bract protrudes beyond and is partially fused with the reduced ovuliferous scale. The ovuliferous scale bears approximately six inverted, small, and flattened seeds. Pollen cones are borne in terminal clusters. Microsporophylls are helically arranged, each bearing three abaxial, basally fused pollen sacs. Pollen is assaccate, rounded, and with an inconspicuous pore. Morphological, structural, and cuticular features of seed cones, pollen cones, and leafy shoots of S. laxum are compared with those of fossil and extant conifers. S. laxum is included in Taxodiaceae and believed to have its closest affinities with a Mesozoic conifer Elatides and a group of Cunninghamia-like conifers. It is reconstructed as a half-evergreen tree that lived in a humid, warm-temperate climate.

Taxodium wallissii Sp. Nov.: First Occurrence of Taxodium from the Upper Cretaceous

Exceptionally well-preserved silicified remains of a new species of Taxodium have been recovered from the Late Cretaceous (ca. 70 million years old) sediments of the Horseshoe Canyon Formation near Drumheller, Alberta, Canada. Specimens include three-dimensionally preserved branches bearing dimorphic leaves, pollen cones, pollen, seed cones, and seeds. The abundance and quality of preservation of these remains have allowed for detailed examination of morphological and anatomical features for comparison with extant representatives of the Taxodiaceae. The vegetative axes bear taxodioid leaves and rare cupressoid leaves; staminate and pistilate axes are subtended entirely by cupressoid leaves. The seed cones are erect, short-stalked, and globose, arranged alternately on branches, and bear up to fifteen helically arranged, deciduous bract-scale complexes. Each cone scale bears two more or less triangular seeds. Vasculature and arrangement of the resin canals of the cone scales are much more complex than that ...

The Triassic conifer seed cone Glyptolepis

A new species of the voltzialean seed cone Glyptolepis is described from the Late Triassic of Germany. Specimens of Glyptolepis richteri sp. nov. are large (up to 14.0 cm long, 3.5 cm wide) and contain numerous small, helically arranged bract scale complexes. Each cone scale is composed of eight uniform lobes, each with an obtuse apex. The bract is fused to the long cone scale stalk and expands distally into a somewhat diamond-shaped laminar unit that completely covered the underlying cone scale. A reconsideration of other fossils assigned to Glyptolepis suggests that all except the type material of Glyptolepis keuperiana Schimper, are erroneously assigned to the genus. Although Glyptolepis is considered a key taxon in some concepts of conifer phylogeny, evidence is presented to suggest that most reconstructions of this genus are based on inaccurate interpretations of unrelated cones.

Anatomy and relationships of petrified seed cones of the Cupressaceae, Taxodiaceae, and Sciadopityaceae

Morphological features and the affinities of petrified seed cones of the Taxodiaceae, Cupressaceae, and Sciadopityaceae are reevaluated. TheCunninghamia-like plants are the earliest record of the families.Parataiwania explains the divergence ofTaiwania from aCunninghamia-like ancestral form by loss of ovuliferous scale and sclerenchyma.Sequoia-like allies probably diverged from a Cretaceous transitional plant likeYezosequoia and are most diversified in the Late Cretaceous.Yubaristrobus andArchicupressus suggest monophyly ofTaxodium and its allied genera of the Taxodiaceae and the Cupressaceae. The Cupressaceae may be derived from a taxodiaceous plant with orthotropous seeds, acquiring a reniform arrangement of the vascular bundles of the bract-scale complex, decussate or whorled phyllotaxis, and spherical cones consisting of a small number of bract-scale complexes. The Cretaceous fossils of the Sciadopityaceae suggest the ancient origin of the family.

Structure and affinities of the petrified plants from the cretaceous of Northern Japan and Saghalien XIIIYubaristrobus gen. nov., A new Taxodiaceous cone from the upper cretaceous of Hokkaido

Yubaristrobus is a new genus of the Taxodiaceae based on a permineralized seed cone from the Upper Cretaceous of Hokkaido. The type species,Y. nakajimae sp. nov., is characterized by peltate bract-scale complexes consisting of a completely-fused bract and scale. The bract-scale complexes are spirally arranged as in most taxodiaceous genera. Their vascular arrangement is specialized and unique in the Taxodiaceae and suggests a relationship with the Cupressaceae.

Structure and affinities of the petrified plants from the cretaceous of northern Japan and Saghalien XI A cupressoid seed cone from the Upper Cretaceous of Hokkaido

Archicupressus is a new genus of the Cupressaceae based on a permineralized conifer female cone from the Upper Cretaceous of Hokkaido. The type species,Archicupressus nihongii sp. nov., is characterized by peltate bract-scale complexes consisting of a completely fused bract and scale bearing erect seeds. Bract-scale complexes are arranged in whorls of three on the cone axis. Each complex has a bristle-like projection, the bract apex, at the top. Affinities to some genera in the Cupressaceae are discussed.

Squamastrobus gen. N., A fertile podocarp from the early cretaceous of Patagonia, Argentina

Squamastrobus tigrensis nov. gen. et sp. has been found in early Cretaceous strata (Baqueró Formation), Santa Cruz Province, Argentina. It is based on branches with squamiform leaves, laterally attached pollen cones and terminally disposed seed cones. The cuticle of leaves and female bract-scale complexes was studied in their general structure and ultrastructure. The pollen cones contain bisaccate pollen grains that are similar both structurally and ultrastructurally with extant and fossil members of the Podocarpaceae. The seed cones are compact structures resembling some taxa found in Mesozoic Gondwana strata. Comparisons made with living and extinct members of the Podocarpaceae suggest some phylogenetic links between Mesozoic cone-bearing forms with the extant genera Microcachrys and Pherosphaera. Finally, some considerations on the origin of Mesozoic podocarps are also included in regard to recently discovered Permian conifers from Gondwana.

A New Taxodiaceous Seed Cone from the Oligocene of Washington

Cunninghamiostrobus goedertii is described as a new species based on permineralized seed cones from the Early Oligocene of Washington. The fossils come from the Makah Formation and were found on the northern shore of the Olympic Peninsula. The cone consists of numerous bract-scale complexes arranged helically around a central axis. Each bract-scale complex has a large bract bearing a small flap of tissue adaxially that represents the ovuliferous scale. Up to three seeds were produced on each complex. The vascular trace to the bract-scale complex diverges from the vascular cylinder of the cone axis as a concentric strand. This divides in the outer cortex of the axis to form a large collateral bract tract abaxially and a minute scale trace adaxially. The latter continues outward to supply the ovuliferous scale. The bract trace divides, forming many strands outward which occur in a row with transfusion tissue between them. Many resin canals also occur in the bract. The new cone combines features found in modern cones of Athrolaxis, Cunninghamia, and Taiwania but is most similar to Cunninghamiostrobus yubariensis from the Late Cretaceous of Japan.

Pityostrobus pubescens, a New Species of Pinaceous Cones from the Late Cretaceous of New Jersey

This new species is based on a single semifusinized cone from the Late Cretaceous (Cenomanian) of New Jersey. The cone is flattened but essentially complete. It is 55 mm long and 8 by 13 mm in diam. Scale apices are thin, rounded, and entire, lacking evidence of an umbo or spine. The vascular cylinder of the cone axis is organized as a series of separate strands. The scale is made up of a basal portion that stands out nearly perpendicular to the cone axis and a sharply upturned distal portion. The bract base has a pronounced abaxial keel. Bract and scale traces diverge from the vascular cylinder of the cone axis separately from one another. A poorly developed interseminal ridge is present at the chalazal end of the seeds. An unusual feature of the cone is the presence of a trichome-bearing epidermis on the cone axis, bract-scale complex, and near the scale apex. Resin canals diverge into the bract-scale complex abaxial to the scale trace with branches becoming adaxial to the scale trace outward. A number of features of the new species occur in cones of Abies, Cedrus, Keteleeria, Larix, Picea, Pseudolarix, Pseudotsuga, and Tsuga as well as in the extinct genus Pseudoaraucaria. Features of Pinus are absent. This suggests that Pseudoaraucaria may have served as an ancestral source for modern genera other than Pinus with Pityostrobus pubescens representing an evolutionary intermediate.

Current status of paleozoic and mesozoic conifers

Florin's hypothesis that modern conifer families except the Taxaceae evolved from the Lebachiaceae through the Voltziaceae is examined using two numerical analyses. The data for both are based on fourteen characters of the bract-scale complex of forty eight fossil and modern conifer taxa. Primitive states of characters are those approximating conditions in Cordaianthus while derived states are features observed in the Voltziaceae and in modern families. Diagrams have been constructed based on percent similarity of derived character states, a phenetic approach, and on the Groundplan-divergence Method of cladistics, more phylogenetic approach. While the results of the two methods differ in detail, they agree generally in support of the hypothesis. Both analyses show a divergence among the Voltziaceae splitting the genera into two distinct groups. One of these groups, which includes most of the genera, shares many features with the Taxodiaceae and may have been ancestral to this family and possibly also the Cupressaceae. Specific precursors of the other modern families within the Voltziaceae are not clear.