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An introduction to the journal is presented which includes articles on topics including analysis of polytrichacean moss phylogeny, overall patterns of phylogeny for marattialean ferns and dipteridacean ferns and flowering plant evolution and phylogeny from fagalean inflorescences.

Premise of the Study: The fossil record of Agathis historically has been restricted to Australasia. Recently described fossils from the Eocene of Patagonian Argentina showed a broader distribution than found previously, which is reinforced here with a new early Paleocene Agathis species from Patagonia. No previous phylogenetic analyses have included fossil Agathis species. Methods: We describe macrofossils from Patagonia of Agathis vegetative and reproductive organs from the early Danian, as well as leaves with Agathis affinities from the latest Maastrichtian. A total evidence phylogenetic analysis is performed, including the new Danian species together with other fossil species having agathioid affinities. Key Results: Early Danian Agathis immortalis sp. nov. is the oldest definite occurrence of Agathis and one of the most complete Agathis species in the fossil record. Leafy twigs, leaves, pollen cones, pollen, ovuliferous complexes, and seeds show features that are extremely similar to the living genus. Dilwynites pollen grains, associated today with both Wollemia and Agathis and known since the Turonian, were found in situ within the pollen cones. Conclusions: Agathis was present in Patagonia ca. 2 million years after the K‐Pg boundary, and the putative latest Cretaceous fossils suggest that the genus survived the K–Pg extinction. Agathis immortalis sp nov. is recovered in a stem position for the genus, while A. zamunerae (Eocene, Patagonia) is recovered as part of the crown. A Mesozoic divergence for the Araucariaceae crown group, previously challenged by molecular divergence estimates, is supported by the combined phylogenetic analyses including the fossil taxa. [ABSTRACT FROM AUTHOR]

Premise of the Study: Equisetum is the sole living representative of Sphenopsida, a clade with impressive species richness, a long fossil history dating back to the Devonian, and obscure relationships with other living pteridophytes. Based on molecular data, the crown group age of Equisetum is mid‐Paleogene, although fossils with possible crown synapomorphies appear in the Triassic. The most widely circulated hypothesis states that the lineage of Equisetum derives from calamitaceans, but no comprehensive phylogenetic studies support the claim. Using a combined approach, we provide a comprehensive phylogenetic analysis of Equisetales, with special emphasis on the origin of genus Equisetum. Methods: We performed parsimony phylogenetic analyses to address relationships of 43 equisetalean species (15 extant, 28 extinct) using a combination of morphological and molecular characters. Key Results: We recovered Equisetaceae + Neocalamites as sister to Calamitaceae + a clade of Angaran and Gondwanan horsetails, with the four groups forming a clade that is sister to Archaeocalamitaceae. The estimated age for the Equisetum crown group is mid‐Mesozoic. Conclusions: Modern horsetails are not nested within calamitaceans; instead, both groups have explored independent evolutionary trajectories since the Carboniferous. Diverse fossil taxon sampling helps to shed light on the position and relationships of equisetalean lineages, of which only a tiny remnant is present within the extant flora. Understanding these relationships and early character configurations of ancient plant clades as Equisetales provide useful tests of hypotheses about overall phylogenetic relationships of euphyllophytes and foundations for future tests of molecular dates with paleontological data. [ABSTRACT FROM AUTHOR]

Premise of the Study: Dipteridaceae is a lineage of ferns that has existed from the early Mesozoic and is known for its extensive fossil record. By integrating information from all described extant and extinct genera into a single phylogenetic study, this paper aims to examine the taxonomy of the group on a whole and explore character evolution within the lineage across time. Methods: A morphological matrix of 51 characters was developed for 72 species (43 extinct and 29 extant) based on published information. Morphological characters were combined with nucleotide sequences for four chloroplast genes (rbcL, atpA, atpB, and rps4) for extant taxa, and combined parsimony analyses were conducted to infer evolutionary trends in the group. Key Results: Dipteridaceae was found to be monophyletic and characterized by highly anastomosing minor veins forming a meshwork of areoles with free‐included veinlets. Based on our analyses, we recognize six previously described genera (i.e., Goeppertella, Thaumatopteris, Clathropteris, Digitopteris, Dipteris, and Cheiropleuria) and one new genus (i.e., Sewardalea). Fossils currently described as Dictyophyllum, Kenderlykia, Hausmannia, and Protorhipis are ambiguously placed on the tree and are recognized as possibly unnatural morphogenera. Conclusions: Overall, the evolutionary trend in Dipteridaceae has been toward increasing complexity in the venation pattern and laminal fusion. Only the Hausmannia‐type frond with dichotomizing primary veins and relatively fused lamina persisted in the later part of the Mesozoic to the present. Within the crown group, we see evidence of re‐radiation of frond forms in Dipteris and Cheiropleuria. [ABSTRACT FROM AUTHOR]

Premise of the Study: We describe a new araucarian species, Araucaria lefipanensis, from the Late Cretaceous flora of the Lefipán Formation, in Patagonia (Argentina) based on reproductive and vegetative remains, with a combination of characters that suggest mosaic evolution in the Araucaria lineage. Methods: The studied fossils were found at the Cañadón del Loro locality. Specimens were separated into two leaf morphotypes, and their morphological differences were tested with MANOVA. Key Results: The new species Araucaria lefipanensis is erected based on the association of dimorphic leaves with cuticle remains and isolated cone scale complexes. The reproductive morphology is characteristic of the extant section Eutacta, whereas the vegetative organs resemble those of the sections Intermedia, Bunya, and Araucaria (the broad‐leaved clade). Conclusions: The leaf dimorphism of A. lefipanensis is similar to that of extant A. bidwillii, where dimorphism is considered to be related to seasonal growth. The leaf dimorphism in A. lefipanensis is consistent with the paleoclimatic and paleoenvironmental reconstructions previously suggested for the Lefipán Formation, which is thought to have been a seasonal subtropical forest. The new species shows evidence of mosaic evolution, with cone scale complexes morphologically similar to section Eutacta and leaves similar to the sections of the broad‐leaved clade, constituting a possible transitional form between these two well‐defined lineages. More complete plant concepts, especially those including both reproductive and vegetative remains are necessary to understand the evolution of ancient plant lineages. This work contributes to this aim by documenting a new species that may add to the understanding of the early evolution of the sections of Araucaria. [ABSTRACT FROM AUTHOR]

* Premise of the study: Agathis is an iconic genus of large, ecologically important, and economically valuable conifers that range over lowland to upper montane rainforests from New Zealand to Sumatra. Exploitation of its timber and copal has greatly reduced the genus's numbers. The early fossil record of Agathis comes entirely from Australia, often presumed to be its area of origin. Agathis has no previous record from South America. * Methods: We describe abundant macrofossils of Agathis vegetative and reproductive organs, from early and middle Eocene rainforest paleofloras of Patagonia, Argentina. The leaves were formerly assigned to the New World cycad genus Zamia. * Key results: Agathis zamunerae sp. nov. is the first South American occurrence and the most complete representation of Agathis in the fossil record. Its morphological features are fully consistent with the living genus. The most similar living species is A. lenticula, endemic to lower montane rainforests of northern Borneo. * Conclusions: Agathis zamunerae sp. nov. demonstrates the presence of modern-aspect Agathis by 52.2 mya and vastly in creases the early range and possible areas of origin of the genus. The revision from Zamia breaks another link between the Eocene and living floras of South America. Agathis was a dominant, keystone element of the Patagonian Eocene floras, along side numerous other plant taxa that still associate with it in Australasia and Southeast Asia. Agathis extinction in South America was an integral part of the transformation of Patagonian biomes over millions of years, but the living species are disappearing from their ranges at a far greater rate. [ABSTRACT FROM AUTHOR]

• Premise of the study: Seed cone morphology and anatomy reflect some of the most important changes in the phylogeny and evolutionary biology of conifers. Reexamination of the enigmatic Jurassic seed cone Pararaucaria patagonica reveals previously unknown systematically informative characters that demonstrate affinities with the Cheirolepidiaceae. This paper documents, for the first time, internal anatomy for seed cones of this important extinct Mesozoic conifer family, which may represent the ghost lineage leading to modern Pinaceae. • Methods: Morphology and anatomy of cones from the Jurassic La Matilde Formation in Patagonia are described from a combination of polished wafers and thin section preparations. New photographic techniques are employed to reveal histological details of thin sections in which organic cell wall remains are not preserved. Specific terminology for conifer seed cones is proposed to help clarify hypotheses of homology for the various structures of the cones. • Key results: Specimens are demonstrated to have trilobed ovuliferous scale tips along with a seed enclosing pocket of ovuliferous scale tissue. Originally thought to represent a seed wing in P. patagonica, this pocket-forming tissue is comparable to the flap of tissue covering seeds of compressed cheirolepidiaceous cones and is probably the most diagnostic character for seed cones of the family. • Conclusions: Pararaucaria patagonica is assigned to Cheirolepidiaceae, documenting anatomical features for seed cones of the family and providing evidence for the antiquity of pinoid conifers leading to the origin of Pinaceae. A list of key morphological and anatomical characters for seed cones of Cheirolepidiaceae is developed to facilitate assignment of a much broader range of fossil remains to the family. This confirms the presence of Cheirolepidiaceae in the Jurassic of the Southern Hemisphere, which was previously suspected from palynological records. [ABSTRACT FROM AUTHOR]

Premise: The sooty molds are a globally distributed ecological group of ascomycetes with epiphyllous, saprotrophic habit, comprising several phylogenetically distant taxa (i.e., members of the classes Dothideomycetes and Eurotiomycetes). Their fossil record extends almost continuously back to the early Cretaceous; however, they are hypothesized to have originated in the early Mesozoic. Here, we describe new specimens of sooty molds associated with conifer leaves from Jurassic hot spring deposits of Patagonia, Argentina. Methods: Thin sections of chert samples from the La Matilde Formation, Deseado Massif (Santa Cruz, Argentina) were observed using light microscopy. Results: The fungi occur on the surface and axils of leafy twigs with podocarpaceous affinities, forming dense subicula comprised by opaque moniliform hyphae. Additionally, several asexual and sexual reproductive structures are observed. On the basis of vegetative (i.e., dense subicula composed of moniliform hyphae; hyphae composed of opaque cells deeply constricted at the septa) and reproductive characters (i.e., poroconidial and sympodioconidial asexual stages and diverse spores), two morphotypes were identified with affinities within lineages of the subphylum Pezizomycotina that encompass the ecological group of sooty molds, and a third morphotype was within the phylum Ascomycota. Conclusions: This finding extends the fossil record of sooty molds to the Jurassic and their geographic fossil range to the South American continent. In particular, their association with podocarpaceous conifers is shown to be ancient, dating back to the Jurassic. This new record provides an additional reference point on the diversity of interactions that characterized Jurassic forests in Patagonia. [ABSTRACT FROM AUTHOR]

Premise: Eocene floras of Patagonia document biotic response to the final separation of Gondwana. The conifer genus Araucaria, distributed worldwide during the Mesozoic, has a disjunct extant distribution between South America and Australasia. Fossils assigned to Australasian Araucaria Sect. Eutacta usually are represented by isolated organs, making diagnosis difficult. Araucaria pichileufensis E.W. Berry, from the middle Eocene Río Pichileufú (RP) site in Argentine Patagonia, was originally placed in Sect. Eutacta and later reported from the early Eocene Laguna del Hunco (LH) locality. However, the relationship of A. pichileufensis to Sect. Eutacta and the conspecificity of the Araucaria material among these Patagonian floras have not been tested using modern methods. Methods: We review the type material of A. pichileufensis alongside large (n = 192) new fossil collections of Araucaria from LH and RP, including multi‐organ preservation of leafy branches, ovuliferous complexes, and pollen cones. We use a total evidence phylogenetic analysis to analyze relationships of the fossils to Sect. Eutacta. Results: We describe Araucaria huncoensis sp. nov. from LH and improve the whole‐plant concept for Araucaria pichileufensis from RP. The two species respectively resolve in the crown and stem of Sect. Eutacta. Conclusions: Our results confirm the presence and indicate the survival of Sect. Eutacta in South America during early Antarctic separation. The exceptionally complete fossils significantly predate several molecular age estimates for crown Eutacta. The differentiation of two Araucaria species demonstrates conifer turnover during climate change and initial South American isolation from the early to middle Eocene. [ABSTRACT FROM AUTHOR]