Benjamin Bomfleur

Fossilized nuclei and chromosomes reveal 180 million years of genomic stasis in royal ferns.

Cytologically Informative Fossils Fossilization processes tend to destroy fine-cell structure but, exceptionally, Bomfleur et al. (p. 1376) have found examples of fossil ferns from the Jurassic in which subcellular structures, including organelles such as nuclei and chromosomes, are well-preserved. Comparative and quantative analyses show that these cells closely resemble the fossil nuclei of extant cinnamon ferns, Osmundastrum cinnamomea, which indicates that this group of ferns has remained virtually unchanged for 180 million years. Fern fossils provide evidence that nuclear shape, size, and chromosomal content have changed little since the Jurassic. Rapidly permineralized fossils can provide exceptional insights into the evolution of life over geological time. Here, we present an exquisitely preserved, calcified stem of a royal fern (Osmundaceae) from Early Jurassic lahar deposits of Sweden in which authigenic mineral precipitation from hydrothermal brines occurred so rapidly that it preserved cytoplasm, cytosol granules, nuclei, and even chromosomes in various stages of cell division. Morphometric parameters of interphase nuclei match those of extant Osmundaceae, indicating that the genome size of these reputed “living fossils” has remained unchanged over at least 180 million years—a paramount example of evolutionary stasis.

Triassic floras of Antarctica: Plant diversity and distribution in high paleolatitude communities

ABSTRACT Continental Triassic sequences in Antarctica are among the most continuous and best represented in Gondwana. Triassic fossil plants have been collected sporadically from Antarctica since the beginning of the twentieth century, but our knowledge of the vegetation during this time has dramatically increased during the last three decades. Here we review the fossil record of Triassic plants as representatives of natural groups from sites along the Transantarctic Mountains, using the fossils as evidence for successive vegetational changes through the Triassic, taking into account that these plant communities were living under particular high-latitude (70° or higher) paleoclimatological conditions, including a polar light regime. Even though our knowledge of the Triassic floras of Antarctica is still incomplete, this survey shows that these floras were remarkably diverse. Lycopsids, equisetaleans, ferns, seed ferns, ginkgoaleans, and conifers were major components of the landscape in Antarctica during this time. The diversity of gymnosperms is exceptional, with almost every major clade of seed plants present, despite the high paleolatitude; however, each clade is often represented by only one or a few genera. The occurrence of permineralized peat, along with compression-impression floras, has increased our knowledge of the morphology, reproductive biology, and evolution of many of the plants in these floras. In general, floral changes in Antarctica during the Triassic can be recognized elsewhere in Gondwana, especially in South America, although a strict correlation based on macrofossils is still not possible. Thus, this contribution represents the first attempt to bring together information on Triassic floras from continental Antarctica (excluding the Antarctic Peninsula) within a biostratigraphic framework and thereby to compare these floras with those from lower latitudes.

Systematics and Paleoecology of a New Peltaspermalean Seed Fern from the Triassic Polar Vegetation of Gondwana

A new Triassic seed fern is described on the basis of a large collection of well-preserved plant compressions from the Upper Triassic of Mt. Falla, Queen Alexandra Range, central Transantarctic Mountains. The foliage is simple entire-margined to pinnatifid to partly pinnate and is assigned to Dejerseya lobata (Jones et de Jersey) Herbst emend. nov. Associated with these leaves occur two new reproductive structures. The ovulate organ Matatiella dejerseyi sp. nov. is a lax, conelike structure with primarily shield-shaped megasporophylls that are dissected into three to four narrow lobes, each bearing a single recurved, naked ovule. The pollen organ Townrovia polaris sp. nov. consists of a slender axis arising from a covered reproductive bud, bearing pinnately arranged, stalked, elongate receptacles each with ∼20 unilocular, clavate pollen sacs; the pollen is bisaccate nontaeniate with an irregular longitudinal sulcus and coarse saccus endoreticulations, corresponding to the dispersed pollen Falcisporites australis. Similar pollen grains occur in the micropylar canals of seed cuticles of M. dejerseyi. Co-occurrence data indicate that the three taxa are probably different organs from one plant species. This new seed fern is assigned to the Matatiellaceae, which we place into the Peltaspermales because of structural similarities with vegetative and reproductive organs of other peltaspermalean seed ferns. It appears that several Triassic Gondwanan plant fossil taxa of currently uncertain affinities—such as Pachydermophyllum, Linguifolium, Carpolithus mackayi, and Andersonia—may belong to the Matatiellaceae as well. We suggest that the matatiellacean peltasperms were opportunistic, early successional plants that were particularly successful in colonizing stressed wetland environments in polar latitudes during the Triassic.

Whole-Plant Concept and Environment Reconstruction of a Telemachus Conifer (Voltziales) from the Triassic of Antarctica

We present a whole-plant concept for a genus of voltzialean conifers on the basis of compression/impression and permineralized material from the Triassic of Antarctica. The reconstruction of the individual organs is based on a combination of organic connections, structural correspondences, similarities in cuticles and epidermal morphologies, co-occurrence data, and ex situ palynology. The affiliated genera of organs include trunks, branches, and roots (Notophytum); strap-shaped leaves with parallel venation (Heidiphyllum compressions and permineralized Notophytum leaves); seed cones (Telemachus and Parasciadopitys); pollen cones (Switzianthus); and bisaccate pollen of Alisporites type. Structural similarities lead us to suggest that Parasciadopitys is the permineralized state of a Telemachus cone and should be treated as a junior synonym. Biotic interactions involving the reconstructed conifer genus include plant-insect interactions (oviposition by Odonata) and not less than five different types of plant-fungal interactions, including two distinct endomycorrhizal associations, two probable seed parasites, and epiphyllous fungi. A representative whole plant is reconstructed as a 10–15-m-tall, seasonally deciduous forest tree with a vertical, narrow-conical crown shape. We interpret these Telemachus trees as the dominant components of peat-forming conifer swamps, forest bogs, and immature bottomland vegetation in the Triassic high-latitude river basins of southern Gondwana. In architecture, growth habit, and many ecological characteristics, the Telemachus conifers appear to be comparable to extant larch (Larix). Owing to the large amount and often exquisite preservation of the material, this conceptual whole-plant genus represents one of the most completely reconstructed ancient conifer taxa to date.

Triassic leech cocoon from Antarctica contains fossil bell animal

Our understanding of the evolution of life on Earth is limited by the imperfection of the fossil record. One reason for this imperfect record is that organisms without hard parts, such as bones, shells, and wood, have a very low potential to enter the fossil record. Occasionally, however, exceptional fossil deposits that preserve soft-bodied organisms provide a rare glimpse of the true biodiversity during past periods of Earth history. We here present an extraordinary find of a fossil ciliate that is encased inside the wall layer of a more than 200 Ma leech cocoon from Antarctica. The microfossil consists of a helically contractile stalk that attaches to a main body with a peristomial feeding apparatus and a large C-shaped macronucleus. It agrees in every aspect with the living bell animals, such as Vorticella. Vorticellids and similar peritrichs are vital constituents of aquatic ecosystems worldwide, but so far have lacked any fossil record. This discovery offers a glimpse of ancient soft-bodied protozoan biotas, and also highlights the potential of clitellate cocoons as microscopic “conservation traps” comparable to amber.

Plant assemblages from the Shafer Peak Formation (Lower Jurassic), north Victoria Land, Transantarctic Mountains

Abstract The Jurassic plant fossil record of Gondwana is generally meagre, which renders phytogeographic and palaeoclimatic interpretations difficult to date. Moreover, plant fossil assemblages mainly consist of impressions/compressions with rather limited palaeobiological and palaeoecological significance. We here present a detailed survey of new Early Jurassic plant assemblages from the Pliensbachian Shafer Peak Formation, north Victoria Land, Transantarctic Mountains. Some of the well-preserved fossils yield cuticle. The floras consist of isoetalean lycophytes, sphenophytes, several ferns, bennettitaleans, and conifers. In addition, three distinct kinds of conifer shoots and needles were obtained from bulk macerations. The composition of the plant communities is typical for Jurassic macrofloras of Gondwana, which underscores the general homogeneity of Southern Hemisphere vegetation during the mid-Mesozoic. Altogether, the plant fossil assemblages indicate humid and warm temperate conditions, which is in contrast to recent palaeoclimatic models that predict cool temperate climates for the continental interior of southern Gondwana during the Jurassic. However, there is no evidence for notable soil development or peat accumulation. The environmental conditions were apparently very unstable due to intense volcanic activity that resulted in frequent perturbation of landscape and vegetation, hampering the development of long-lived climax communities. Cuticles of bennettitaleans and conifers show xeromorphic features that may have been beneficial for growth in this volcanic environment.

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 bracts include a well-defined hypodermal layer and resin canals with adaxial traces. A single vascular trace enters the complex and divides to produce the ovuliferous-scale trace and bract traces. Ovules/seeds are ovoid and weakly winged. The pollen cone–bearing branch apices show stalks of at least 17 pollen cones arranged in a pseudowhorl. Each stalk consists of an inflated base surrounded by 5–6 scale-like leaves. The anatomy and morphology of the fossil material agrees so closely with that of modern Cunninghamia that we are confident in describing it as a new species of this genus, Cunninghamia taylorii sp. nov. The present material provides a rare opportunity to contribute toward a better understanding of the specific variation, biology, ecology, and evolutionary history of cunninghamioid Cupressaceae.

A reappraisal of Neocalamites and Schizoneura (fossil Equisetales) based on material from the Triassic of East Antarctica

Sphenophytes are a common floral element in the Triassic of Gondwana. Most sphenophyte compression fossils have been conventionally assigned to a few, presumably very widespread species of Neocalamites based on vegetative features of the stems (or pith casts) and the foliage. During recent decades, however, new reports on morphological and anatomical details of some of these fossils have cast doubt on the systematic affinities of many Gondwanan Triassic sphenophytes. Here we describe Neocalamites suberosus (Artabe & Zamuner) nov. comb. et emend. and Schizoneura africana Feistmantel emend. from several Triassic deposits in the central Transantarctic Mountains and Victoria Land, East Antarctica. The material enables a critical reevaluation of morphological and anatomical features that have been historically used to define the two genera, including leaf-base morphology, degree of leaf fusion, stem vasculature and vallecular canals, and features of the nodal diaphragm. The diagnoses of Neocalamites and Schizoneura are emended so that they more accurately reflect recent advances in our understanding of the anatomy and ontogeny of these plants. [Benjamin Bomfleur [bbomfleur@ku]edu], Rudolph Serbet [serbet@ku.edu], Edith L. Taylor [etaylor@ku.edu] and Thomas N. Taylor [tntaylor@ku.edu], Department of Ecology and Evolutionary Biology, and Biodiversity Institute, University of Kansas, Lawrence, KS 66045, USA; Ignacio H. Escapa [iescapa@mef.org.ar], CONICET—Museo Paleontológico Egidio Feruglio, Trelew, Chubut 9100, Argentina. Received 4.7.2012; revised 22.12.2012; accepted 7.1.2013. Bomfleur, B., Escapa, I.H., Serbet, R., Taylor, E.L. & Taylor, T.N., 2013. A reappraisal of Neocalamites and Schizoneura (fossil Equisetales) based on material from the Triassic of East Antarctica. Alcheringa 37, 1–17. ISSN 0311-5518.

Habit and ecology of the Petriellales, an unusual group of seed plants from the Triassic of Gondwana

Premise of research. Well-preserved Triassic plant fossils from Antarctica yield insights into the physiology of plant growth under the seasonal light regimes of warm polar forests, a type of ecosystem without any modern analogue. Among the many well-known Triassic plants from Antarctica is the enigmatic Petriellaea triangulata, a dispersed seedpod structure that is considered a possible homologue of the angiosperm carpel. However, the morphology and physiology of the plants that produced these seedpods have so far remained largely elusive. Methodology. Here, we describe petriellalean stems and leaves in compression and anatomical preservation that enable a detailed interpretation of the physiology and ecology of these plants. Pivotal results. Our results indicate that the Petriellales were diminutive, evergreen, shade-adapted perennial shrubs that colonized the understory of the deciduous forest biome of polar Gondwana. This life form is very unlike that of any other known seed-plant group of that time. By contrast, it fits remarkably well into the “dark and disturbed” niche that some authors considered to have sheltered the rise of the flowering plants some 100 Myr later. Conclusions. The hitherto enigmatic Petriellales are now among the most comprehensively reconstructed groups of extinct seed plants and emerge as promising candidates for elucidating the mysterious origin of the angiosperms.

Osmunda pulchella sp. nov. from the Jurassic of Sweden—reconciling molecular and fossil evidence in the phylogeny of modern royal ferns (Osmundaceae)

BackgroundThe classification of royal ferns (Osmundaceae) has long remained controversial. Recent molecular phylogenies indicate that Osmunda is paraphyletic and needs to be separated into Osmundastrum and Osmunda s.str. Here, however, we describe an exquisitely preserved Jurassic Osmunda rhizome (O. pulchella sp. nov.) that combines diagnostic features of both Osmundastrum and Osmunda, calling molecular evidence for paraphyly into question. We assembled a new morphological matrix based on rhizome anatomy, and used network analyses to establish phylogenetic relationships between fossil and extant members of modern Osmundaceae. We re-analysed the original molecular data to evaluate root-placement support. Finally, we integrated morphological and molecular data-sets using the evolutionary placement algorithm.ResultsOsmunda pulchella and five additional Jurassic rhizome species show anatomical character suites intermediate between Osmundastrum and Osmunda. Molecular evidence for paraphyly is ambiguous: a previously unrecognized signal from spacer sequences favours an alternative root placement that would resolve Osmunda s.l. as monophyletic. Our evolutionary placement analysis identifies fossil species as probable ancestral members of modern genera and subgenera, which accords with recent evidence from Bayesian dating.ConclusionsOsmunda pulchella is likely a precursor of the Osmundastrum lineage. The recently proposed root placement in Osmundaceae—based solely on molecular data—stems from possibly misinformative outgroup signals in rbcL and atpA genes. We conclude that the seemingly conflicting evidence from morphological, anatomical, molecular, and palaeontological data can instead be elegantly reconciled under the assumption that Osmunda is indeed monophyletic.