William D. Tidwell

A review of selected triassic to Early Cretaceous ferns

After becoming nearly extinct during the Permian, the ferns began a slow recovery during the Triassic as the climate of the earth moderated. As a result, a considerable number and variety were present and widely distributed during the Jurassic and Early Cretaceous. However, with the rapid expansion of the angiosperms during the Late Cretaceous, the ferns once again became reduced in variety and greatly restricted in distribution. Some of the Mesozoic ferns are rather primitive and obviously are closely related descendants of Paleozoic taxa. Such ferns are assigned mostly to the Marattiaceae, Guaireaceae, Osmundaceae, and Gleicheniaceae. The majority of the Mesozoic ferns, however, are distinctive and appear to have originated during that era. These fossil ferns generally fit into modern orders and families such as the Matoniaceae or the Dipteridaceae. In some cases, it is difficult to clearly distinguish some of the Mesozoic ferns from living genera.

Tomlisonia thomassonii, gen. et sp. nov., a permineralized grass from the upper miocene Ricardo Formation, California

Abstract A permineralized specimen of grass assigned to Tomlinsonia thomassonii gen. et sp. nov. was collected from the Upper Miocene Ricardo Formation of California. It shows Kranz anatomy and the C 4 photosynthetic pathway. The plants posses underground rhizomes with roots resembling the extant grass Paspalum commersonii Lamarck. Sheathing leaf bases wrap around an erect culm. Anatomical details of the culm and leaf sheats are ksimilar to pooid, panicoid and some bambusoid grasses. Leaf lamina is characterized by mesophyll tissue that exhibits a low interveinal distance of only 3–5 cells between vascular bundles. The occurrence of this fossil grass in the Ricardo Formation suggests, at least by the Miocene, the establishment of a Mediterranean chaparral type grassland in the Mojave desert region and climatic condition conducive to the growth and expansion of several grass species.

Interconnected reproductive and vegetative remains of Populus (Salicaceae) from the middle Eocene Green River Formation, northeastern Utah

A new specimen from the Middle Eocene Evacuation Creek Member of the Green River Formation in northeastern Utah shows a twig with several leaves of Populus wilmattae Cockrell and a fruiting raceme attached. This specimen establishes for the first time the type of fruits borne by P. wilmattae and provides additional characters with which to assess its taxonomic and evolutionary status. An associated seed shows attached placental hairs like those of extant species of Populus. The Green River fossil differs from extant Populus species in having basically palmate leaf venation and in bearing its fruiting axis on a young twig. In other aspects, the fossil species is remarkably similar to the extant species Populus mexicana.

A new fossilized tree fern stem, Nishidacaulis burgii gen. et sp. nov., from Nebraska-South Dakota, USA

Abstract A permineralized tree fern stem assigned to the new genus and species Nishidacaulis burgii was collected from northwestern Nebraska. Although collected in the basal conglomerate of the Upper Eocene-Lower Oligocene Chadron Formation, it was most likely reworked from sediments of Early Cretaceous age in the Black Hills, South Dakota. The stem appears to have had radial symmetry and was surrounded by persistent leaf bases and adventitious roots. Uniseriate, multicellular epidermal trichomes are also persistent on and around the stem. A sclerenchymatous sheath around the solenostelic stele is absent. Leaf and petiolar traces are undivided throughout and are modified reverse omega- or U-shaped with incurved ends. Mucilage cells or cavities occur in the outer phloem of the petiolar vascular strand, but are lacking in the fundamental tissue of the petiole. This new genus may represent a transitional form in a possible lineage from Upper Jurassic-Lower Cretaceous “ Cibotium ” tasmanense to Upper Cretaceous C. iwatense and extant members of Cibotium . The basal pinna trace being derived from the adaxial corner only of the petiolar vascular strand in N. burgii indicates the original plant had a small or reduced basal pinna and a short petiole. Its entire frond was more or less rhombic, suggesting a habit with an erect stem with radiating fronds forming a crown.

A review of the genus Paraphyllanthoxylon

Abstract Thirteen species of petrified wood have been assigned previously to the genus Paraphyllanthoxylon which was established by Bailey (1924) as representative of the section Phyllanthoideae of the family Euphorbiaceae. Madel (1962) considered the genus Paraphyllanthoxylon representative of only the Glochidion wood group of the section Phyllanthoideae. This necessitates the establishment of a new genus, Phyllanthoideoxylon , for fossil woods which have characteristics in common with several of the other wood groups in the section Phyllanthoideae. The thirteen previously identified species of Paraphyllanthoxylon are reviewed and compared with the characteristics of the genus. Eleven of these species are retained in Paraphyllanthoxylon Bailey (emend. Madel), one ( P. bangalamodense ) is assigned to Phyllanthoideoxylon nov. gen. and one ( P. keriense ) is transferred to Bridelioxylon Ramanujam.

Species of the Cretaceous Tree Fern Tempskya from Utah

Nine species of the permineralized stems of Tempskya were investigated from the upper Lower Cretaceous Cedar Mountain and Burro Canyon Formations, and the lower Upper Cretaceous Dakota Formation in central and southeastern Utah. Tempskya jonesii, T. stichkae, and T. readii are new and are differentiated on the basis of the radial orientation of their dorsiventral stems, their internodal lengths, the lack of sclerenchyma in the inner cortex of T. jonesii, the three nearly continuous zones of sclerenchyma in the inner cortex of T. stichkae, and the completely sclerotic inner cortex of T. readii. Specimens of T. jonesii and T. minor were collected in growth position near Castle Dale, Utah, which is the first time Tempskya has been collected in this position in North America. Thin leaves were also observed for the first time in Tempskya in specimens of T. wyomingense. Tunnels containing three sizes of fecal pellets are common in tissues of stems, roots, petioles, and epidermal hairs of the false trunks of Tempskya, indicating that three different grazers fed upon these plants. Arbuscules of vesicular-arbuscular (V-A) mycorrhizal fungi occur in some roots of the false trunks of T. jonesii. Specific characters of Tempskya and possible environmental circumstances under which these plants grew are reviewed, and we conclude that they grew under relatively humid conditions in swamps on flood plains.

Protoyucca shadishii gen. et sp. nov., An arborescent monocotyledon with secondary growth from the Middle Miocene of Northwestern Nevada, U.S.A.

Abstract Protoyucca shadishii gen. et sp. nov. is described from permineralized specimens collected from Middle Miocene strata in northwestern Nevada. This species is the first reported permineralized monocotyledon with secondary growth. The stem which grew to 60 cm or more in diameter, consists of a primary cylinder surrounded by a cylinder of secondary tissues. A secondary thickening meristem, secondary cortex and periderm occur outside of the cylinder containing secondary bundles. Associated leaves and lobed stem bases with roots attached are referred to this species. Protoyucca shadishii may have evolved as a potential subtropical ancestor of Yucca at possible dry edaphic sites when a more mesic environment occured in northern Nevada during the Tertiary.

Palmoxylon simperi and Palmoxylon pristina: Two Pre-Cretaceous Angiosperms from Utah

Petrified palm stems (Palmoxylon simperi and Palmoxylon pristina) from the Middle Jurassic Arapien Shale Formation near Redmond, Sevier Country, Utah, are the first unequivocal angiosperms reported from pre-Cretaceous strata.

Two new fossil matoniaceous stem genera from Tasmania, Australia

Two new genera, Tasmanopteris and Heweria, from Tasmania are the first definite permineralized rhizomes assignable to the Matoniaceae. Tasmanopteris richmondii sp. nov., of mide-Mesozoic age, is from the Lune River site in southwestern Tasmania and is composed of four or more annular solenostelos separated by cortices with an inner mesarch xylem ring and outer exarch xylem rings. Secretory canals occur in the cortices between the protoxylem clusters of its outer xylem rings. The specimen of Heweria kempii sp. nov., which is very similar to extant Matonia, was collected from a Lower Tertiary conglomerate in central Tasmania but was reworked from older sediments. Anatomically, the rhizomes of Heweria consist of 3–6 annular solenosteles with the inner and middle xylem rings being mesarch, whereas the outer ring is exarch. Roots arise opposite the protoxylem clusters of the outermost ring. Epidermal hairs on the stems of this genus are like those of living Matonia in being attenuate, uniseriate, and multicellular. Associated venation pattern of partially preserved leaves, isolated sporangia, annuli, and spores in this specimen provide additional support for the relationships of this fossil to modern Matonia.

Grammatocaulis donponii gen. et sp. nov., a permineralized fern from the Jurassic of Queensland, Australia

A permineralized fern stem from Middle to Late Jurassic sediments (Injune Creek Group) in the Wandoan area of southeastern Queensland is assigned to the new genus and species Grammatocaulis donpanii. The stem possesses an ectophloic siphonostele with the xylem divided into an outer zone of long tracheids and an inner zone of short, wide, parenchyma-like tracheids surrounding a pith. Leaf traces are round in cross section in the parenchymatous inner cortex, becoming linear to oblong in the outer cortex and outside of the stem. Petiole bases have sclerotic rings around vascular strands, but lack stipular wings. Some of its outermost petiolar vascular strands assume a C-shape which may be due to distortion. Parenchymatous tissue occurs in the middle of the protoxylem at the ends of the elliptical petiolar vascular strands. At higher levels, the parenchymatous tissue of the strands is found in the metaxylem as well. Nonglandular multicellular scales occur on the petioles. Although the family of this genus is unknown, it is similar anatomically to Grammatopteris of the Anachoropteridaceae from the Late Paleozoic of Europe. If these two genera are related, this specimen suggests more structural diversity, a wider geographic distribution and a longer geologic range for the Anachoropteridaceae than previously known.