Discussion of ‘Gisbornian (Caradoc) graptolites from New South Wales, Australia: systematics, biostratigraphy and evolution’ by B. Rickards, L. Sherwin and P. Williamson

Vandenberg, A.H.M.

doi:10.1002/gj.939

Cited by 7 publications

(4 citation statements)

References 10 publications

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“…sp., associated with rare specimens of the trilobite Triarthrus. This fauna, comparable with that described from the Keenans Bridge locality west of Orange NSW (VandenBerg 2003), is roughly equivalent to the Dicellograptus ornatus Biozone in Nevada (Štorch et al 2011), Zone 13 (Rectograptus truncatus intermedius Zone) in the Marathon region of Texas (Goldman et al 1995), the Amplexograptus prominens Biozone of Anticosti, Quebec (Stewart and Mitchell 1997), the Dicellograptus complanatus Biozone to lower Dicellograptus complexus Biozone in South China (Mu et al 1993, Chen et al 2000, and the Dicellograptus complanatus Biozone of Britain (Zalasiewicz et al 2009). ) is an isolated rocky mound, raised more than 200 m above its base The Cambrian and Ordovician deposits had not previously been reported from the area and on existing geological maps the exposed sedimentary rocks were referred to the Devonian.…”

Section: Malachis Hill Formationsupporting

confidence: 85%

“…Subsequent studies have focussed on Late Ordovician forms, commencing with Jenkins et al (1982) who described Eastonian (Katian) graptolites from Narooma on the NSW south coast. Identifications and age implications of a supposed Gisbornian (i. e. Sandbian) fauna from west of Orange (Rickards et al 2001;Sherwin and Rickards 2000) were contested and corrected by VandenBerg (2003) who determined the age as early Bolindian. The most recent publications on NSW graptolites involved documentation of a fauna of mid-Katian age from north of Canberra (Williamson and Rickards 2006), and description of near-contemporaneous dendroids from west of Wellington (Percival and Quinn 2012).…”

Section: Historic Overviewmentioning

confidence: 99%

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The Ordovician Exposed: Short Papers, Abstracts, and Field Guides for the 12th International Symposium on the Ordovician System

Leslie¹

2015

TSR

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Section: Malachis Hill Formationsupporting

confidence: 85%

Section: Historic Overviewmentioning

confidence: 99%

The Ordovician Exposed: Short Papers, Abstracts, and Field Guides for the 12th International Symposium on the Ordovician System

Leslie¹

2015

TSR

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“…Si. mirabilis has a unique structure that is quite difficult to interpret from the available material but may be a highly derived descendant of Cryptograptus (see Vandenberg 2003), although it is very much younger than any other known representative of that clade.…”

Section: Genus Parareteograptus Mu 1974 Emend Hereinmentioning

confidence: 99%

Uppermost Ordovician (upper Katian-Hirnantian) graptolites of north-central Nevada, U.S.A.

Štorch¹,

Mitchell²,

Finney³

et al. 2011

Bull. Geosci.

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Forty-three graptolite species belonging to fifteen genera are described from the upper Katian ornatus and pacificus biozones and Hirnantian extraordinarius and persculptus biozones of Vinini Creek and Martin Ridge reference sections of north-central Nevada. Approximately half of the species described have not been previously recorded from Nevada, six species are left in open nomenclature. Infraorder Neograptina and Styracograptus gen. nov. are erected. The maximum graptolite diversity is in organic-rich black shale in the lower part of the pacificus Biozone in the Vinini Formation. Species diversity decreased abruptly at the top of the Diceratograptus mirus Subzone, recognized herein in the upper part of the pacificus Biozone. Faunal turnover reached a peak in the lower part of early Hirnantian extraordinarius Biozone where long-dominant Ordovician clades (diplograptines) are rapidly replaced by normalograptids (Neograptina), presumably evolved in, and invading from, a less-temperate higher latitude. Eight late Katian diplograptine species recur in the upper part of the extraordinarius Biozone but, in contrast to their former abundance, are present there only as very rare individuals. Even more unusually, eight diplograptine species (members of Dicellograptus, Anticostia, Rectograptus, Paraorthograptus, Phormograptus, Styracograptus and Appendispinograptus) also reappear in the uppermost part of the Vinini Creek section, well into the persculptus Biozone (which is topped by a prominent stratigraphic unconformity). These occurrences record a complex extinction pattern among graptolites that involved a radical but extended ecological reorganization rather than a synchronous global collapse of the pre-glacial ecosystem. The biozonation applied in the Nevadan sections correlates well with those established in the Yangtze Platform of China, southern Kazakhstan, north-eastern Siberia and Northern Canada. •

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“…For example, some of the best-sampled fossil groups can have exceptionally long ghost branches. Among the well-sampled planktonic graptolites, the late Ordovician Sinoretiograptus appears to be most closely related to early glossograptids (Vandenberg 2003), implying a 15–20 Myr ghost branch. Under a homogenous Poisson process of sampling, it would be extremely unlikely to observe such a long gap in sampling of a lineage and simultaneously observe the high sampling frequency of other graptoloid taxa in the Ordovician.…”

Section: Introductionmentioning

confidence: 99%

Comparingcal3and other a posteriori time-scaling approaches in a case study with the pterocephaliid trilobites

Bapst

Hopkins

2016

Paleobiology

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Reconstructing the tree of life involves more than identifying relationships among lineages; it also entails accurately estimating when lineages diverged. Paleontologists typically scale cladograms to time a posteriori by direct reference to first appearances of taxa in the stratigraphic record. Some approaches use probabilistic models of branching, extinction, and sampling processes to date samples of trees, such as the recently developed cal3 method, which stochastically draws divergence dates given a set of rates for those processes. However, these models require estimates of the rates of those processes, which may be hard to obtain, particularly for sampling. Here, we contrast the use of cal3 and other a posteriori time-scaling approaches by examining a previous study that documented a decelerating rate of morphological evolution in pterocephaliid trilobites. Although aspects of the data set make estimation of branching, extinction, and sampling rates difficult, we use a multifaceted approach to calculate and evaluate the rate estimates needed for applying cal3. In agreement with previous simulation studies, we find that the choice of phylogenetic dating method impacts downstream macroevolutionary conclusions. We also find contradictory evolutionary inferences between analyses on ancestor–descendant contrasts (based on ancestor trait reconstruction methods) and maximum-likelihood parameter estimates. Ancestral taxon inference in cal3 corroborates previously hypothesized ancestor–descendant sequences, but cal3 suggests greater support for budding cladogenesis than anagenesis. This case study demonstrates the potential and wide applicability of the cal3 method and the benefits afforded by choosing cal3 over simpler a posteriori time-scaling approaches.

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Discussion of ‘Gisbornian (Caradoc) graptolites from New South Wales, Australia: systematics, biostratigraphy and evolution’ by B. Rickards, L. Sherwin and P. Williamson

Cited by 7 publications

References 10 publications

The Ordovician Exposed: Short Papers, Abstracts, and Field Guides for the 12th International Symposium on the Ordovician System

The Ordovician Exposed: Short Papers, Abstracts, and Field Guides for the 12th International Symposium on the Ordovician System

Uppermost Ordovician (upper Katian-Hirnantian) graptolites of north-central Nevada, U.S.A.

Comparingcal3and other a posteriori time-scaling approaches in a case study with the pterocephaliid trilobites

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