Godfrey S. Nowlan

False teeth: conodont-vertebrate phylogenetic relationships revisited

ABSTRACT An evidence-based reassessment of the phylogenetic relationships of conodonts shows that they are not “stem” gnathostomes, nor vertebrates, and not even craniates. A significant group of conodont workers have proposed or accepted a craniate designation for the conodont animal, an interpretation that is increasingly becoming established as accepted “fact”. Against this prevailing trend, our conclusion is based on a revised analysis of traditional morphological features of both discrete conodont elements and apparatuses, histological investigation and a revised cladistic analysis modifying that used in the keystone publication promoted as proof of the hypothesis that conodonts are vertebrates. Our study suggests that conodonts possibly were not even chordates but demonstration of this is beyond the scope of this paper. To summarize, in conodonts there is low cephalization; presence of simple V-shaped trunk musculature and unique large-crystal albid material in the elements; lack of a dermal skeleton including characteristic vertebrate hard tissues of bone, dentine and enamel; lack of odontodes with bone of attachment and a unique pulp system; lack of segmentally-arranged paraxial elements and dermal elements in median fins, all of which supports neither a vertebrate nor a craniate relationship for conodonts.

Exceptionally preserved Late Ordovician biotas from Manitoba, Canada

There are few body fossil biotas known from early Paleozoic accretionary shorelines, and very few examples of Ordovician soft-bodied assemblages. This study documents two recently discovered biotas from separate sedimentary basins in Manitoba, Canada, that provide unique information about tropical shoreline communities shortly before the Late Ordovician extinction event. Each site represents a distinct depositional environment, but they share biotic elements, including eurypterids, xiphosurids, and large problematic tubes. The William Lake biota, representing more restricted conditions, includes jellyfish that are among the best hydromedusan body fossils known. Rocks at the Airport Cove site, deposited under more open circulation, contain scolecodonts and noncalcified algae. These biotas have some parallels with the recently described Middle Ordovician Winneshiek Lagerstatte, but are also similar to some Late Silurian assemblages. Considered together, early Paleozoic marginal marine deposits are a rich but as yet poorly known source of paleobiodiversity data.

High-resolution 87Sr/86Sr chemostratigraphy of the Silurian: Implications for event correlation and strontium flux

Analyses of 87Sr/86Sr in Silurian conodonts recovered from localities in North America and Europe representing 13 of the 14 defined Silurian conodont zones provide a high-resolution record of seawater chemistry for the Silurian Period. These data, which are characterized by little or no scatter, depict several high-frequency cycles superimposed on a gradual longer term rise in 87Sr/86Sr for the Silurian. High-frequency cycles have a duration of about one conodont zone, and many correlate with sequence boundaries recognized around the world. These data provide a much higher resolution image of secular changes in 87Sr/86Sr during the Silurian and may require a rethinking of models of strontium isotope flux in marine basins.

Geochemical anomalies near the Ordovician‐Silurian boundary, Northern Yukon Territory, Canada 1

Basinal strata spanning the Late Ordovician extinction have been determined for major and trace elements, and isotopes of C, O and S. A marked increase in organic C, and siderophile (i.e., Ni, V) and chalcophile (i.e., Zn, Cd, Hg, As, Sb, Se and Mo) elements is observed at a level that is no older than the base of the G. persculptus Zone. In sections for which isotopic data are available, these anomalies coincide with decreases in δ 13 C values, suggesting a major biomass reduction, and δ18O values, indicating a warming trend. At the same time, δ34S values in pyrite become highly positive indicating reduced bottom‐water conditions. These results suggest that a rapid inversion of stratified ocean water causing a brief but widespread episode of anoxic surface waters may have been the immediate cause of extinction. The ultimate cause of extinction is unknown, although the magnitude and apparent global synchroneity of the extinction suggest that it was of catastrophic effect. The chalcophile and siderophile e...

Silurian vertebrate biozonal scheme

Abstract Improved vertebrate biozonal scheme is presented for the Silurian: boundaries of all zones have been revised; andnew zones Valyalepis crista in the Lower Llandovery and Loganellia avonia in the Lower Wenlock part of the succession have been established

EARLY CAMBRIAN METAZOAN EGGS, EMBRYOS, AND PHOSPHATIC MICROFOSSILS FROM NORTHWESTERN CANADA

Abstract Three-dimensionally phosphatized, spherical fossils, interpreted as metazoan eggs and embryos on the basis of taphonomic features and cleavage patterns, are reported for the first time from the Cambrian of North America. These microfossils occur with a phosphatized biota of skeletonized fossils, including specimens indicative of the earliest Cambrian Anabarites–Protohertzina Zone in the Wernecke Mountains of eastern Yukon Territory, northwestern Canada. They range in size from 0.25 mm to more than 1.0 mm in diameter and can be referred to two genera, Olivooides Qian, 1977 and Archaeooides Qian, 1977. The North American discovery extends the biogeographic range of earliest Cambrian eggs and embryos from coeval successions in China and Siberia, suggesting a wide geographic distribution of these taxa, and emphasizes the crucial role of local environmental and taphonomic conditions in preserving this phosphatic window into the record of early animal evolution. In addition to previously reported taxa, the phosphatized biota also include indeterminate spheroids, fused clusters of Protohertzina siciformis Missarzhevsky, 1973, the enigmatic rodlike fossil Zhejiangorhabdion comptum Yue and Zhao, 1993, phosphatized fossils, including Paradoxiconus typicalis Qian et al., 2001, protoconularid Carinachites sp., and phosphatic tubes assigned to Hyolithellus cf. H. isiticus Missarzhevsky, 1969, cf. Pseudorthotheca sp., and ?Rugatotheca sp.

PALYNOLOGY AND MICROPALEONTOLOGY OF THE CLAM BANK FORMATION (LOWER DEVONIAN) OF WESTERN NEWFOUNDLAND, CANADA

Abstract Sandstone and siltstone samples collected from the lowest part of the Clam Bank Formation in western Newfoundland contain a distinctive monospecific conodont assemblage of Ozarkodina remscheidensis eosteinhornensis and O. remscheidensis ssp., confidently dated as Late Ludlow through Lochkovian. Palynomorph assemblages of terrestrial spores, acritarchs, chitinozoans, scolecodonts and plant fragments are relatively abundant and diverse in the lower 250 m of this formation. Taxa include the cryptospore genera Cymbohilates, Acontotetras, Hispanaediscus, Laevolancis, and Tetrahedraletes, spore genera Ambitisporites, Aneurospora, Apiculiretusispora, Emphanisporites, Retusotriletes, Synorisporites, Vermiverruspora, and a new species Stellatispora fahraeusi. Acritarchs include the taxon Triangulina sanpetrensis and chitinozoa include Angochitina chlupaci. Palynomorphs indicate a Lochkovian age, corresponding with the Apiculiretusispora sp. E zone from Europe. In well preserved samples from this section, ...

A NEW EURYPTERID (CHELICERATA) FROM THE UPPER ORDOVICIAN OF MANITOULIN ISLAND, ONTARIO, CANADA

Abstract A new genus and species of eurypterid (Eurypterida: Chelicerata) is described as Orcanopterus manitoulinensis from the Upper Ordovician Kagawong Submember (Upper Member) of the Georgian Bay Formation, Manitoulin Island, Ontario, Canada. The material comprises several partial specimens in addition to disarticulated carapaces, appendages, metastomas, opisthosomal segments, and telsons. Associated fossils include rare bryozoans, a conularid, ostracodes, and conodonts. A restricted marine lagoon, or very shallow subtidal to intertidal environment is inferred. This assemblage, perhaps representing an accumulation of molted exuviae, was apparently preserved as the result of rapid burial by carbonate muds and silts during a storm event. O. manitoulinensis shares a number of traits with both the Hughmilleriidae and the Carcinosomatidae. Diagnostic features include curved preabdominal segments, a petaloid A metastoma with deep anterior emargination, spiniferous appendages of Carcinosoma type, paddle with enlarged, symmetrical podomere 9, and a xiphous telson. It is only the fourth (the first Canadian) well-documented Ordovician eurypterid genus, and provides the oldest reliable record of the Hughmillerioidea to date.

MIDDLE TO UPPER CAMBRIAN LINGULIFORMEAN BRACHIOPODS FROM THE DEADWOOD FORMATION OF SUBSURFACE ALBERTA AND SASKATCHEWAN, CANADA

Abstract Limestone beds intercalated within a succession of sandstones, siltstones, and shales of the subsurface Deadwood Formation, cored in two wells in Alberta and Saskatchewan, yielded twelve species assigned to eight genera of organophosphatic brachiopods (Subphylum Linguliformea). The nine species recovered from the Alberta well are Marjuman (late Middle to early Late Cambrian) in age. Three of these species, Neotreta davidi Popov, Berg-Madsen, and Holmer, 1994; Picnotreta debilis Henderson and MacKinnon, 1981; and Stilpnotreta magna Henderson and MacKinnon, 1981, are associated with the Mindyallan (early Late Cambrian) of Queensland, and are previously unknown from Laurentia. This brachiopod fauna occurs with a diverse fauna of paraconodont species. The Saskatchewan well yielded three species of Linnarssonella, belonging to the upper Steptoean to the lower Sunwaptan (middle Late Cambrian). One new subfamily, Neotretinae, is erected, and two new species, Rhondellina albertensis, and Linnarssonella tubicula are described. Linnarssonella elongata Bell, 1941, is reinstated as a valid species. This fauna occurs with a diverse fauna of paraconodont species and is overlain, 226 feet higher, by conodonts of the Early Sunwaptan Proconodontus Zone.

The conodont Iapetognathus and its value for defining the base of the Ordovician System

Nicoll et al. (1999, Brigham Young University Geology Studies 44, 27–101) published the taxonomy of species of the ramiform conodont Iapetognathus Landing in Fortey et al. (1982, The Cambrian–Ordovician boundary: sections, fossil distributions, and correlations, National Museum of Wales, Geological Series No. 3, Cardiff, 95–129) and its ancestor Iapetonudus Nicoll et al., 1999. Cooper et al. (2001, Episodes 24, 19–28) used the First Appearance Datum of Iapetognathus fluctivagus Nicoll et al., 1999 to mark the base of the Ordovician System at Green Point, Newfoundland. Terfelt et al. (2012, Lethaia 45, 227–237) re-evaluated Iapetognathus at Green Point and made several taxonomic and stratigraphic conclusions, nearly all of which we refute herein.