Systematic biostratigraphy: A solution to problematic classification systems in biostratigraphy

Systematic biostratigraphy is based on the exclusive use of monophyletic marker taxa. Non-monophyletic, or artificial, marker taxa have been shown to change biostratigraphic correlations, a situation that can be rectified by using systematics to ensure that marker taxa are monophyletic or natural. Both hypothetical and real examples demonstrate the validity of the methodology. The foraminiferal genera Praemurica and Parvularugoglobigerina are examples of non-monophyletic marker taxa. Cladistic results permit the reclassification of both genera, and a revision of foraminiferal biostratigraphy. Systematic biostratigraphy ensures the use of monophyletic marker taxa, preventing artificial classifications from hindering biostratigraphic correlations and producing more accurate, and stable, biostratigraphic zonations.     

Higher elasmobranch phylogeny and biostratigraphy

Living sharks, skates and rays share several derived skeletal characters that are absent in most extinct elasmobranchs, suggesting a monophyletic group of 'higher' elasmobranchs. Within this group opinions vary as to phylogenetic relationships, although three broad groups are generally recognized. Arguments for and against monophyly of these group (batoids; squalomorphs; galeomorphs) are examined. Many of their contained taxa are also of questionable validity. Cladistic analysis of living galeomorphs reveals a sequence of characters supporting monophyly of the group as whole, but not of its more generalized contained taxa. The temporal distribution of fossil galeomorphs corroborates the hypothesis of relationship suggested by neontological data; i.e. there is considerable stratigraphic harmony with Recent phylogenetic data.     

Toward an improved Silurian conodont biostratigraphy

Silurian conodonts have been widely reported and many species have worldwide distribution. However, present zonations utilizing them have many limitations and no single scheme provides a suitable standard. A good standard zonation for Silurian conodonts is desirable, but impossible at our present state of knowledge. Environmental differentiation, the rapid evolution of several unrelated conodont lineages and the lack of distributional data are the principal factors producing this situation. Existing Silurian conodont zonations are evaluated, and zonal schemes based on well documented phylogenetic lineages are advocated. Eight datum planes are proposed as an additional biostratigraphic framework in the system. These are the Distomodus staurognathoides Datum, Pterospathodus amorphognathoides Datum, Pterospathodus Extinction Datum, Kockelella walliseri Datum, Kockelella variabilis Datum, Ancoradella ploeckensis Datum, Kockelella Extinction Datum and Ozarkodina crispa Datum. Six of these datum planes are based on the evolutionary appearance of the datum-defining species. Extinction datum planes correspond to a significant level of extinction amongst the conodont-bearing animals.     

Tithonian ammonoid biostratigraphy in eastern Himalayan Tibet

The Tithonian and Lower Berriasian sediments in the eastern Himalayas of Tibet contain an extensive sequence of ammonoid fauna. New collections in situ through the Lanongla, Pure, Gucuo and Jiapeila sections have facilitated a major revision of the ammonoid assemblages. Probably due to depositional facies segregation, the Belemnopsis galoi-bearing beds can be regarded as the oldest Tithonian sediments in which the basal Tithonian ammonoid Kossmatia is not present. The Lower Tithonian includes the Virgatosphinctes-Aulacosphinctoides and Uhligites-Aulacosphinctes assemblages; the Upper Tithonian includes the Haplophylloceras pingue, Blanfordiceras wallichi and Haplophylloceras strigile-Corongoceras-Himalayites assemblages. The Spiticeras assemblage is suggested to be from the Lowermost Berriasian. The new ammonoid assemblages at well-defined levels in Himalayan Tibet provide some crucial links for correlation with other regions of the SW Pacific domain where these ammonoid genera have been widely distributed.     

The importance of Precambrian microfossils for modern biostratigraphy

A new model of the distribution of Proterozoic microorganisms is developed, based on studies of Riphean and Vendian silicified and organic-walled microfossils from the reference sections of northern Eurasia, and on their comparison with other known microfossil assemblages. Within the interval from 2.0 to 0.535 Ga, seven successive informal global microphytological units (referred to as proterohorizons) are determined: (1) Labradorian proterohorizon occupies the upper part of the Lower Proterozoic (Paleoproterozoic), 2.0–1.65 Ga; (2) Anabarian proterohorizon, Lower Riphean-lower Middle Riphean (lower and middle Mesoproterozoic), 1.65–1.2 Ga; (3) Turukhanian proterohorizon, upper Middle Riphean (upper Mesoproterozoic), 1.2–1.03 Ga; (4) Uchuromayan proterohorizon, lower Upper Riphean (lower Neoproterozoic), 1.03–0.85 Ga; (5) Yuzhnouralian proterohorizon, upper Upper Riphean (upper Neoproterozoic without Ediacaran); (6) Amadeusian proterohorizon, Lower Vendian (Ediacaran), 0.6–0.55 Ga; and (7) Belomoryan proterohorizon, Upper Vendian (Ediacaran), 0.55–0.535 Ga.     

A review of the Cambrian biostratigraphy of South Australia

Cambrian rocks in South Australia occur in the Stansbury, Arrowie, eastern Officer and Warburton Basins. The succession in the Stansbury and Arrowie Basins can be divided into three sequence sets (supersequences), 1, 2 and 3. Sequence set 1 can be divided into five third-order sequences: 1.0, 1.1A, 1.1B, 1.2 and 1.3. Trilobites from the Stansbury and Arrowie Basins are restricted largely to the lower part of the succession. Four trilobite zones are recognized: Abadiella huoi (latest Atdabanian–earliest Botoman), Pararaia tatei, Pararaia bunyerooensis and Pararaia janeae Zones (all Botoman). Trilobites higher in the succession are known from only a few horizons and in part correlate with the upper Lower Cambrian Lungwangmiaoan Stage of China, equivalent to the top Toyonian. Pagetia sp. has been reported in the Coobowie Formation of the Stansbury Basin, thus suggesting an early Middle Cambrian age.The Cambrian faunas of the Warburton Basin range in age from early Middle Cambrian (Late Templetonian) to very Late Cambrian, although the richest faunal assemblages are late Middle Cambrian (Ptychagnostus punctuosus to Goniagnostus nathorsti Zones). Conodonts, including Cordylodus proavus, occur in a Datsonian fauna.The Arrowie Basin contains the most complete and best studied archaeocyath succession in the Australia–Antarctica region. The Warriootacyathus wilkawillensis, Spirillicyathus tenuis and Jugalicyathus tardus Zones from the lower Wilkawillina Limestone (Arrowie Basin) and equivalents are correlated with the Atdabanian. Botoman archaeocyathids occur higher in the Wilkawillina Limestone. The youngest (Toyonian) archaeocyath fauna in Australia occurs in the Wirrealpa Limestone (Arrowie Basin).Brachiopods and molluscs of the Arrowie and Stansbury Basins can be divided into four biostratigraphic assemblages. Several informal Early Cambrian SSF biostratigraphic assemblages are recognized. Probable tabulate-like corals occur in the Botoman Moorowie Formation. Seven informal acritarch assemblages occur in the Early Cambrian of the Stansbury and Arrowie Basins. Trace fossils may mark the Precambrian–Cambrian boundary. Only two of several tuffaceous horizons from the Stansbury and Arrowie Basins have been dated (i) a date of 522.0 ± 2.1 Ma from the Heatherdale Shale of the Stansbury Basin, about 400 m above latest Atdabanian archaeocyathids and (ii) a date of 522.0 ± 1.8 Ma from the lower part of the Billy Creek Formation in the Arrowie Basin. Neither date is regarded as reliable.     

Early Tremadocian (Ordovician) graptolite biostratigraphy and correlation

A revision of the early Tremadocian graptolites of the genus Rhabdinopora shows that Rhabdinopora proparabola from the Xiaoyangqiao section, Dayangcha, North China is the oldest species of the genus. Early Tremadocian species of Rhabdinopora can be differentiated easily by the construction of their nemata. The earliest species, Rhabdinopora proparabola, lacks a nema, while a multibranched nema is present in Rhabdinopora campanulatum (= Rhabdinopora parabola). The Rhabdinopora proparabola, Rhabdinopora campanulatum, Rhabdinopora flabelliformis (Anisograptus matanensis Biozone) and Rhabdinopora anglica biozones can be correlated worldwide. A short interval at the base of the Ordovician System does not contain any planktic graptolites.     

Dinocyst biostratigraphy of the Upper Cretaceous of northern Siberia

A stratigraphic chart is developed of the Upper Cretaceous deposits of northern Siberia based on dinocysts. It covers the period from the Upper Cenomanian to the Maastrichtian, including 15 biostratigraphic units (beds with characteristic assemblages or local zones), and is correlated with the inoceram zonation.     

Conodont biostratigraphy of the Early Triassic in eastern Slovenia

The Early Triassic is a critical interval for the study of recovery from the terminal Permian mass extinction, as there are small-scale extinction events, which may have contributed to the delayed recovery. The systematic measuring and sampling of a 12-m-thick section at the Mokrice locality in eastern Slovenia has resulted in the recovery of a conodont fauna from the Olenekian beds. Four conodont zones have been recognized. These zones are in ascending order as follows: the Hadrodontina aequabilis Zone, Platyvillosus corniger Zone, Platyvillosus regularis Zone, and Triassospathodus hungaricus Zone. These conodont zones confirm the proposed conodont biozonation sequence in western Slovenia and have correlation value especially for the western marginal Tethys. Multielement conodont apparatuses of Triassospathodus hungaricus and Platyvillosus regularis have been reconstructed based on conodont elements that were recently obtained from the Slovenian sections. Although the S₂element was not found, the apparatus indicates that the conodont species “Spathognathodus” hungaricus should be assigned to the genus Triassospathodus.     

Causal Characteristics for Ecoepidemiology

We suggest that there are six fundamental characteristics of causation: time order, co-occurrence, preceding causation, sufficiency, interaction, and alteration. The cause precedes the effect (time order). The cause co-occurs with the unaffected entity in space and time (co-occurrence). Causes and their effects are the result of a web of causation (preceding causation). The intensity, frequency, and duration of the cause are adequate and the susceptible entity can exhibit the type and magnitude of the effect (sufficiency). The cause effectively interacts with the entity in a way that induces the effect (interaction). And, the entity is changed by the interactions with the cause (alteration). In contrast to Hill's criteria, the causal characteristics are distinct from the: (1) evidence that is used to document causal characteristics, (2) sources of information used to develop the evidence, and (3) qualities used to evaluate evidence of causal characteristics and body of evidence for the causal relationship. Evidence of causal characteristics can form the basis for assessments of epidemiological studies and can structure an explanatory narrative that is causally relevant and substantive. Six core characteristics may be easier to organize, evaluate, communicate, and for decision-makers to assimilate, remember, and inspire action.     

The Causal Conditioned Reflex

E. A. Asratyan has long been the Director of the Institute of Higher Nervous Activity and Neurophysiology in Moscow. In this article he addresses himself to the difficult problem of accounting for complex forms of animal behavior from the base line of Pavlovian theory. This is the same task Boyko undertakes in his article in this issue, but Asratyan approaches it in a different manner. Going back to the stenographic notes of Pavlov's famous "Wednesdays" (sessions at which he discussed a wide variety of laboratory matters and topics of the day), Asratyan considers the little known concept of the "causal" reflex. From the remarks of the Russian editors of Problems of Philosophy (note 4), it is clear that Asratyan's ideas are by no means universally accepted.     

Valsequillo biostratigraphy. III: Equid ecospecies in Paleoindian sites

Greater precision in North American Pleistocene equid taxonomy makes it now possible to exploit the ubiquitous horse remains in Paleoindian sites as ecological index-fossils. The horses of Central Mexico and the Southern Plains can be sorted by tooth size alone, except for two rare large horses of the Southern Plains. The species endemic to these grasslands and south to Central Mexico are Equus pacificus (large), E. conversidens (small), E. francisci (smallest). The Southern Plains were also occupied by a specialized grazer E. excelsus (Burnet and Sandia caves) and E. occidentalis (Dry and Sandia caves). West of the Rocky Mountains E. occidentalis was dominant. East of the Mississippi River two woodland species are found: E. fraternus and E. littoralis.     

Valsequillo biostratigraphy. IV: Proboscidean ecospecies in Paleoindian sites

Five proboscidean species have been found in Paleoindian sites from North to South America: two open-country adaptations, Mammuthus columbi and Cuvieronius tarijensis, two woodland and riparian forms, Mammut americanum and Mammuthus jeffersonii, and one tropical savanna species, Haplomastodon chimborazi. Their value in biostratigraphy and as ecological index fossils is discussed with particular emphasis on the Central Mexican Paleoindian sites.