Judith E. Skog

George Mason University | GMU · Department of Biology

Premise: Reinvestigation of previously described fossil plants using improved techniques can provide insights for additional characters resulting in better family assignments and relationships to modern plants, as in this new study of the fossil fern Acrostichopteris from the mid-Cretaceous. The discovery of new species within genera provides addi...

The Nomenclature Committee on Fossils has been dealing with numerous conservation proposals for names of fossil-genera that originally contained a hyphen (Doweld in Taxon 62: 638–642. 2013). Doweld correctly indicated that Art. 60.9 in the International Code of Nomenclature for algae, fungi, and plants (the Melbourne Code, McNeill & al. in Regnum V...

Specimens that had been previously considered to represent a fertile fern, Onychiopsis psilotoides (Stokes et Webb) Ward from the English Wealden, have been restudied and are here considered to represent a new genus (Tanydorus) in a new family within the Lycopodiales. Evidence for this new classification of the material includes the combination of...

An analysis of morphological data for 13 species with 33 characters and molecular data for 14 species from the chloroplast DNA intergenic spacer region trnL-F indicates that species of the genus Anemia fall into two well-supported subgenera, Anemiorrhiza and Anemia. In addition, one species of the genus Mohria appears to belong within Anemia. Altho...

To resolve phylogenetic relationships among all genera and subgenera in Osmundaceae, we analyzed over 8,500 characters of DNA sequence data from seven plastid loci (atpA, rbcL, rbcL–accD, rbcL–atpB, rps4–trnS, trnG–trnR, and trnL–trnF). Our results confirm those from earlier anatomical and single-gene (rbcL) studies that suggested Osmunda s.l. is p...

Restudy of Stockmans' [Stockmans, F., 1968. Végétaux Mésodévoniens récoltés aux confins du Massif du Brabant (Belgique). Mém. Mus. Roy. Hist. Nat. Belg. 159, 1-49.] Middle Devonian Langoxylon asterochlaenoideum clarifies many details of its anatomy. The main axis has a large multi-ribbed actinostele from which traces of two size classes depart in a...

available online: http://www.iapt-taxon.org/historic/2006.htm

Phylogenetic relationships among 48 species representing the nine sections within the fern genus Elaphoglossum were investigated using cpDNA sequence data from rbcL, trnL-F, and rps4-trnS. Elaphoglossum is shown to be a well-supported, monophyletic genus containing five major clades. Mapping of morphological characters onto the molecular phylogeny...

Three new species of Aurealcaulis, A. burgii, A. dakotensis, and A. nebraskensis, are described from three localities in southwest South Dakota and northwest Nebraska. Aurealcaulis burgii is characterized by having a pair of leaf traces that fuse in the outermost layers of the outer cortex or immediately outside the stem to form a C-shaped vascular...

Athyrium filix-femina (Lady Fern) comprises a complex of homoploid (n = 40) taxa, distributed over much of the northern hemisphere and extending into South America, whose evolutionary relationships are poorly understood and whose taxonomic treatment is problematic. The A. filix-femina complex of North America comprises as many as four taxa with ove...

The paleobiogeography of the extant leptosporangiate fern families present in the Mesozoic is reviewed based mainly on data from megafossils that possess enough characters to be assigned to a family. Times of first appearances are discussed for each family, followed by their distribution throughout the Mesozoic. Paleolatitudes and climatic conditio...

Permineralized rhizomes of two new species of Solenostelopteris Kershaw, S. leithii, and S. medlynii, are described from the Upper Jurassic Morrison Formation from the Steiner and Scott's localities north of Greybull, Wyoming, and from Fremont Junction, east of Mt. Ellen, and Mussentuchit Wash sites in Utah. The species are characterized by having...

A new fossil fern is described from the early Albian age (early Cretaceous) Silty Beds of Bedfordshire, England, and assigned to the extant genus Gleichenia of the Gleicheniaceae. The pinnules and rachis fragments are three-dimensionally preserved as charcoal. The rachis is 2-4 mm in diameter with a C-shaped vascular bundle and appears to grow from...

Fensome, R. A., Jansonius, J. & Skog, J. E.: Typification and names of fossil plants – a review and discussion. – Taxon 47: 695‐702. – ISSN 0040‐0262. The rules surrounding the designation of nomenclatural types to fossil plant taxa, including the definitions of the various kinds of type and the related requirements for valid publication, are found...

The specimens assigned to the genus Dryopterites Berry were reexamined and details of the reproductive characters including the spores are described for the first time. Based upon this new information about the ferns, two species have remained in the genus Dryopterites with one designated as the type species (D. virginica) and a lectotype for this...

We present the first cladistic analysis of extant ferns based on morphological characters. Our data set consisted of 77 vegetative and reproductive morphological/anatomical characters recorded on a broad sampling of 50 extant pteridophyte taxa, with representatives of all major fern groups, and one seed plant (Cycas). An annotated list of both reta...

This study includes a comprehensive examination of existing collections, extensive field work over two summers and literature searches. Based upon this data source the lower vascular plants of the Dakota Formation (Cenomanian) from five localities in Kansas and Nebraska were studied. Thirteen species can be recognized including one lycophyte, one s...

The Isoetaeeae is considercd 10 bc a monotypic family with about 150 species (Tryon and Tryon, 1982). They note that some authors place fossils in the genus !soel;les Munster (1842). /soiiles as a genus has been assigned to fossil plants that look like Isoetites but differ in stem or leaf morphology or in which some plant paI1 is lacking. lsoi!t;re...

Discovery of compression/impression megafossil material from the Cenomanian (mid-Cretaceous) in Kansas documents the occurrence of the genus Marsilea during this age. Only vegetative material has been found as complete plants; associated structures that may be fertile structures could belong to the genus also. This new fossil species extends the me...

Discovery of compression/impression megafossil material from the Cenomanian (mid-Cretaceous) in Kansas documents the occurrence of the genus Marsilea during this age. Only vegetative material has been found as complete plants; associated structures that may be fertile structures could belong to the genus also. This new fossil species extends the me...

Based on characters of the fertile fronds, two species of fossil ferns from the Lower Cretaceous Potomac Group of the U.S.A., originally described as species of Osmunda by Fontaine in 1889, are transferred to the genus Anemia. The two species display primitive characters for that genus. Analysis of these and other characters of Anemia and related s...

Occurrences of lycopsid megafossils and their spores in the Mesozoic are reviewed. Subarborescent lepidodendralean forms diversified in the early Mesozoic before going extinct in the early Jurassic, although herbaceous, Isoetes-like forms-considered here also to be lepidodendraleans-survived to the present day as represented by the sole surviving g...

The genus Camerosporites Leschik 1956 is here emended and the seven species attributed to it are reduced to four. Assemblages of Camerosporites isolated from Upper Triassic strata from sites in the eastern U.S. (the Newark, Culpeper, Richmond, Taylorsville, and Danville basins) and the western U.S. (Chinle Formation) consistently segregate into thr...

A fossil fern described originally by W. Fontaine as Aspidium heterophyllum has been reexamined. Based upon characteristics of the sorus, indusium, sporangium, and spores the plant belongs to the family Matoniaceae. There is no genus within the family to which the fossil can be assigned; thus, a new genus (Delosorus) is proposed. This report increa...

A fossil fern described originally by W. Fontaine as Aspidium heterophyllum has been reexamined. Based upon characteristics of the sorus, indusium, sporangium, and spores the plant belongs to the family Matoniaceae. There is no genus within the family to which the fossil can be assigned; thus, a new genus (Delosorus) is proposed. This report increa...

The first occurrence of attached fertile structures to foliage assignable to the form genus Triphyllopteris Schimper is reported from the early Carboniferous Price Formation of southwestern Virginia. Sporangium-bearing branch systems consisting of a basal undivided foliar region and a distal much-divided fertile region are described as a new specie...

Lagenospermum imparirameum Arnold, originally described from a few specimens of cupulate seeds borne on two or three times dichotomous branches, is now shown to be borne on more complex branching systems. Details of the cupule and seed morphology are added and an emended diagnosis of the taxon is given. A new species,Gnetopsis hispida, is described...

Ibyka gen. n. is described from late Middle Devonian compressions and petrifactions collected in eastern New York State. It is a robust plant of which three orders of branching and ultimate appendages (leaves) are known. The latter dichotomize up to five times, are arranged spirally on all orders of branching, are three-dimensional, and all orders...

Study of herbarium specimens and of living populations of Hudsonia plants over several seasons showed a wider range of variation than could be accommodated by the present nomenclature of the genus. Four characters (leaf length, pedicel length, leaf hairiness, and ovary hairiness) were found to form distinct associations on a scatter diagram. Ecolog...

A fossil plant compression specimen is described that consists of a nonlaminate, pinnate branch system bearing terminal synangia. The synangia are about 2 mm long and consist of four sporangia each of which includes about 400 spores. The fossil seems to be most closely related to certain species of Zeilleria and is tentatively regarded as the micro...