New perspectives on transitions between ecological-evolutionary subunits in the “type
interval” for coordinated stasis
James J. Zambito IV, Carlton E. Brett, Gordon C. Baird, Sarah E. Kolbe, Arnold I. Miller
Paleobiology
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We obtained abundance data for post-extinction Genesee Group assemblages primarily
from bulk samples originally collected by Charles Thayer and reposited at the Yale Peabody
Museum (Thayer 1974, Yale Peabody Collection Accession 7112). As part of the present study,
extensive fieldwork and mapping was undertaken to update the stratigraphic context of Thayer's
collections; additional samples were collected from Thayer's localities, as well as other outcrops,
to supplement the samples available from the museum collections. While Thayer's work focused
on the entire Genesee Group, the present study covers only the lowest part of the interval, given
that the primary goal here was to describe the immediate post-Taghanic Biocrisis fauna for the
type region. This interval encompasses the lowermost Geneseo, Unadilla, and Gilboa formations
(latest Givetian, Schmidtognathus hermanni and Klapperina disparilis conodont zones).
We identified taxa in these samples to the species-level when possible using the
taxonomy outlined in Linsley (1994) and subsequent revisions by Bizzarro (1995) and Sartenaer
(in press). For crinoid materials and bryozoan morphotypes, only presence/absence data were
recorded, since individual abundances of these groups are difficult to quantify, but their presence
is still meaningful. Because moldic preservation was common in these siliciclastic-dominated
facies, we used a modified version of the Minimum Number of Individuals (MNI) method
(Gilinsky and Bennington 1994) to prevent overestimation of taxonomic abundances; in this
modified version, both moldic and skeletal material were counted and the MNI methodology was
applied. Sample size volumes were approximately 4 to 8 liters. Ultimately, a dataset of 142
samples containing a total of 124 taxa was developed. Prior to quantitative analysis, taxa
occurring in only one sample (singletons) and samples comprised of a single taxon were
removed, resulting in a final dataset of 133 samples containing 89 taxa.
We then compiled abundance-category data collected by Prosser (1897, 1899) for the
eastern Hamilton (Windom and Cooperstown members of the Moscow Formation) and Genesee
(Geneseo, Unadilla, and Gilboa formations) groups and updated this dataset taxonomically using
Linsley (1994). In the field, we revised the stratigraphic context of Prosser's faunal lists, as we
had for Thayer's collections. In addition, we collected a small number of samples from the
Cooperstown Member during fieldwork to test the reproducibility of our samples with those of
Prosser's for characterizing the Hamilton and Genesee faunas.
To numerically compare our samples with Prosser's, we transformed our dataset to
abundance categories comparable to those used by Prosser. Although not explicitly stated,
information provided by Prosser in his texts (1897 and 1899), indicated that these ranks can be
approximated by the following abundance ranges: very abundant ( > = 40 specimens), abundant
(14-39), common (6-13), rare (3-5), and very rare ( < = 2). The text also suggests that Prosser's
sample sizes were comparable to ours. Direct comparison with our data set was not entirely
straightforward because Prosser did not use the MNI method, such that our abundance counts
were generally less than those in his samples where direct comparisons between the two datasets
were possible based on their occurrences in comparable geographic areas and stratigraphic
intervals. This disparity was expected because the MNI methodology, in effect, minimizes
taxonomic counts. That said, preliminary analyses of the combined dataset showed that virtually
identical results were produced regardless of whether our data set was transformed to abundance
categories using Prosser's inferred abundance distributions, two-thirds of his abundance
distributions, one-half of his abundance distributions, or even just presence/absence. In the
analyses presented herein, we reduced the abundance distributions that Prosser assigned to each
category by approximately two-thirds and assigned our abundance data to the corresponding
categories (see Gilinsky and Bennington 1994 for relevant discussion). Since Prosser did not
collect data on bryozoans, these were removed prior to analysis, as were singletons and samples
containing only one taxon. This culling resulted in a combined dataset of 247 samples comprised
of 140 taxa.
All data used in this study have been added to the Paleobiology Database
(http://paleodb.org; collections associated with References 28312, 29162, 30118, 30119, and
30564). Data matrices analyzed can be found in Supplementary Tables 1 and 2.
Bizzarro, M. 1995. The Middle Devonian Chonetoidean brachiopods from the Hamilton Group
of New York. Documents des Laboratoires de Géologie de Lyon 136:149-189.
Gilinsky, N. J. and J. B. Bennington. 1994. Estimating numbers of whole individuals from
collections of body parts: a taphonomic limitation of the paleontological record.
Paleobiology 20(2):245-258.
Linsley, D. M. 1994. Devonian paleontology of New York; containing the brachiopods, bivalves,
rostroconchs, gastropods, tergomyans, ammonoids, trilobites, eurypterids and
phyllocarids, based on the lithographs of James Hall and John Clarke, Special Publication
- Paleontological Research Institution Vol. 21, 472 pp.
Prosser, C. S. 1897. The classification and distribution of the Hamilton and Chemung series of
central and eastern New York. Annual Report of the Regents - New York State Museum,
2, Report 49:12-13, 83-222.
——. 1899. Classification and distribution of the Hamilton and Chemung series of central and
eastern New York, Part 2. Annual Report of the Regents - New York State Museum, 2,
Report 51:65-315.
Sartenaer, P. in press (anticipated 2012) Reconsideration of the taxonomic position, the
stratigraphic range and the geographic distribution of the New York Frasnian species
Atrypa mesacostale HALL, 1843. Bulletin de l’Institut royal des Sciences naturelles de
Belgique, Sciences de la Terre
Thayer, C. W. 1974. Marine paleoecology in the Upper Devonian of New York. Lethaia
7(2):121-155.