Rewan, The Crater

Dispersed per-mineralized cones, stems, rhizomorphs and roots attest to a diversity of pleuromeids in the Early Triassic Bowen Basin of eastern Australia. The lack of organic connection precludes whole plant identification and the material is assigned to form-taxa. Cones are referred to Cylostrobus clavatus Cantrill et Webb, sp. nov., a bisporangiate cone, and Pleuromeia renifomis Cantrill et Webb, sp. nov., a monosporangiate cone. The stem Pleurocaulis rewanense Cantrill et Webb, gen. et sp. nov. has a central exarch protostele surrounded by an aerenchymous inner cortex. Two unlobed rbizomorphs with internal anatomy are recognized, Helicorhiza duckworthensis Cantrill et Webb, gen. et sp. nov. and Cidarophyton rewanense. Duckworthia isoeteformis Cantrill et Webb, gen. et sp. nov. is a form taxon for roots that are monarch with an eccentric vascular bundle and were presumably borne by the rbizomorphs. The anatomy of the plants in conjunction with the sedimentary setting and high palaeolatitudes suggests that the Bowen Basin lycopsids were small ephemeral plants that exploited seasonally wet conditions. 0

Proceedings of the Geologists' Association, 2016

The Rhaetian marine transgression, which occurred across Europe in the latest Triassic, 205.5 Ma, famously deposited one or more bone beds. Attention has generally focused on the basal bone bed alone, but here we explore this bed, and a stratigraphically higher bone bed at the top of the Westbury Formation, and compare the faunas. The Rhaetian at Hampstead Farm Quarry, Chipping Sodbury, Gloucestershire, UK, has produced more than 26,000 identifiable microvertebrate remains, including teeth and scales of chondrichthyan and osteichthyan fishes, as well as vertebrae of sharks, bony fishes, ichthyosaurs, and plesiosaurs. The higher bone bed ('bed 9') contains more small specimens than the basal bone bed, and they are also less abraded, suggesting less transport. Both bone beds yield largely the same taxa, but Rhomphaiodon minor and rare Vallisia coppi and Sargodon tomicus are found only in the basal bone bed. Duffinselache is reported only from units above the basal bone bed, but low in the Westbury Formation, and durophagous teeth only from two horizons. Four out of nine chondrichthyan species are common to both bone beds, whereas Rhomphaiodon minor and Ceratodus are absent, and hybodonts in general are rarer, in bed 9. Bed 9 is the richer source of marine reptile remains, including ichthyosaur teeth, jaw fragments, vertebrae, rare plesiosaur teeth and vertebrae, and a few Pachystropheus vertebrae and limb bones. Whereas the basal bone bed represents considerable transport and possible storm bed deposition associated with the onset of the Rhaetian Transgression, bed 9 was deposited under a lower energy regime.

Journal of Vertebrate Paleontology, 2003

The Triassic timescale based on nonmarine tetrapod biostratigraphy and biochronology divides Triassic time into eight land-vertebrate faunachrons (LVFs) with boundaries defined by the first appearance datums (FADs) of tetrapod genera or, in two cases, the FADs of a tetrapod species. Definition and characterization of these LVFs is updated here as follows: the beginning of the Lootsbergian LVF ¼ FAD of Lystrosaurus; the beginning of the Nonesian ¼ FAD Cynognathus; the beginning of the Perovkan LVF ¼ FAD Eocyclotosaurus; the beginning of the Berdyankian LVF ¼ FAD Mastodonsaurus giganteus; the beginning of the Otischalkian LVF ¼ FAD Parasuchus; the beginning of the Adamanian LVF ¼ FAD Rutiodon; the beginning of the Revueltian LVF ¼ FAD Typothorax coccinarum; and the beginning of the Apachean LVF ¼ FAD Redondasaurus. The end of the Apachean (¼ beginning of the Wasonian LVF, near the beginning of the Jurassic) is the FAD of the crocodylomorph Protosuchus. The Early Triassic tetrapod LVFs, Lootsbergian and Nonesian, have characteristic tetrapod assemblages in the Karoo basin of South Africa, the Lystrosaurus assemblage zone and the lower two-thirds of the Cynognathus assemblage zone, respectively. The Middle Triassic LVFs, Perovkan and Berdyankian, have characteristic assemblages from the Russian Ural foreland basin, the tetrapod assemblages of the Donguz and the Bukobay svitas, respectively. The Late Triassic LVFs, Otischalkian, Adamanian, Revueltian and Apachean, have characteristic assemblages in the Chinle basin of the western USA, the tetrapod assemblages of the Colorado City Formation of Texas, Blue Mesa Member of the Petrified Forest Formation in Arizona, and Bull Canyon and Redonda formations in New Mexico. Since the Triassic LVFs were introduced, several subdivisions have been proposed: Lootsbergian can be divided into three sub-LVFs, Nonesian into two, Adamanian into two and Revueltian into three. However, successful interregional correlation of most of these sub-LVFs remains to be demonstrated. Occasional records of nonmarine Triassic tetrapods in marine strata, palynostratigraphy, conchostracan biostratigraphy, magnetostratigraphy and radioisotopic ages provide some basis for correlation of the LVFs to the standard global chronostratigraphic scale. These data indicate that Lootsbergian ¼ uppermost Changshingian, Induan and possibly earliest Olenekian; Nonesian ¼ much of the Olenekian; Perovkan ¼ most of the Anisian; Berdyankian ¼ latest Anisian? and Ladinian; Otischalkian ¼ early to late Carnian; Adamanian ¼ most of the late Carnian; Revueltian ¼ early-middle Norian; and Apachean ¼ late Norian-Rhaetian. The Triassic timescale based on tetrapod biostratigraphy and biochronology remains a robust tool for the correlation of nonmarine Triassic tetrapod assemblages independent of the marine timescale.

The ammonoid “Trachyphyllites costatum”Arthaber (1927), based on a single specimen from an erratic boulder of presumed Late Triassic (Norian age) fromTimor, (Indonesia), was originally described as a phylloceratid but later recognized as a true lytoceratid by Basse (1952) and Schindewolf (1961), and used byWiedmann (1966a, 1966b, 1970) to support his idea of a polyphyletic origin of the post-Triassic ammonoids and of the Late Triassic roots of the lytoceratids. New collections of additional specimens and associated taxa from other erratic boulders in the type locality have confirmed observations (Tozer 1971; Krystyn 1978) that the age of the original boulder was misinterpreted, and have shown that “Trachyphyllites” is actually of Early Jurassic (Hettangian) age. An unpublished generic revision of the entire superfamily Lytoceratoidea by Hoffmann (2009) has shown that “Trachyphyllites costatumArthaber” is a junior synonym of Analytoceras hermanni (Gümbel, 1861), a taxon thought by Wähner (1894) to be a subjective synonym of Analytoceras articulatum (J. Sowerby, 1831) We reestablish the species Analytoceras hermanni (Gümbel, 1861) for Analytoceras articulatum “Type B” (Wähner 1894), which is characterized by a wide umbilicus and a small whorl expansion rate. The morphologically distinct “TypeA” (Wähner 1894) corresponds to the type species of Analytoceras, A. articulatum (J. Sowerby, 1831). A revised phylogeny of the Early Jurassic lytoceratids is presented.

2005

ABSTRACT.—The Sonsela Member of the Petrified Forest Formation at Petrified Forest, Arizona and the Tres Lagunas Member of the Santa Rosa Formation in east-central New Mexico yield vertebrate fossil assemblages (faunas) that are intermediate in composition between the Adamanian and Revueltian lvfs in that they include co-occurrences of the phytosaurs Rutiodon and Pseudopalatus and the unique taxon Typothorax antiquum.

Since the first scientific excavations, it has been apparent that the Snyder quarry represents a unique vertebrate fossil assemblage. This assemblage includes an apparent xenacanthid shark, semionotid and redfieldiid fish, a metoposaurid amphibian, a probable procolophonid reptile, a cynodont, an apparent lepidosauromorph, abundant specimens of the phytosaur Pseudopalatus, the aetosaurs Typothorax coccinarum Cope and Desmatosuchus chamaensis Zeigler, Heckert and Lucas, the rauisuchian Postosuchus (sensu stricto), a sphenosuchian and theropod dinosaurs referable to Eucoelophysis. Archosaurs dominate the assemblage, and the phytosaurs, and aetosaurs are all treated separately elsewhere in this volume. The xenacanth apparently pertains to the "Xenacanthus" moorei group and, if it is not a contaminant from screenwashing processes, is one of the youngest xenacanth sharks known. Most osteichthyan fossils at the Snyder quarry are isolated scales and bones, though an incomplete, articulated semionotid has been recovered. The sole metoposaurid fossils recovered to date are a fragmentary, large centrum and isolated teeth that probably pertain to Buettneria and would thus be one of the youngest Buettneria records known. The possible procolophonid fossil consists of a single tooth and remains problematic. The cynodont is represented by an incomplete left distal humerus. The lepidosauromorph is based on an incomplete jaw fragment bearing many pleurodont teeth. The archosaur fauna is somewhat typical of Revueltian Chinle faunas in that it includes the phytosaur Pseudopalatus and the aetosaur Typothorax coccinarum, both index taxa of the Revueltian (early-mid Norian) land-vertebrate faunachron. Rarer archosaurian taxa include the aetosaur Desmatosuchus chamaensis, the theropod dinosaurs, the rauisuchian Postosuchus and the indeterminant sphenosuchian. The rauisuchian is represented by fragmentary postcrania that, from their disparate sizes, clearly represent at least two different individuals.