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Systematic Work (systematic + work)

Distribution by Scientific Domains

Life Sciences	60%

Selected Abstracts

Plumage-based phylogenetic analyses of the Merops bee-eaters

IBIS, Issue 3 2004
D. BRENT BURT
I review previous systematic work on the family Meropidae and present phylogenetic hypotheses derived from my analyses of colour, pattern and shape variation in 30 plumage regions among species and subspecies in this family. Consistent patterns are seen across shallow portions of the trees. Uncertainty remains concerning the placement of several deep branches within this group's phylogeny. In particular, the phylogenetic placement of Meropogon forsteni and Merops breweri, M. ornatus, M. hirundineus and M. boehmi remains uncertain. The biogeographical patterns in the resultant trees are similar with either a Southeast Asian or African origin for the family, with most of the early diversification occurring in Africa, and with multiple independent subsequent invasions of non-African areas. [source]

Stalked crinoids from a Jurassic tidal deposit in western North America

LETHAIA, Issue 1 2000
CAROL M. TANG
This is the first systematic and paleoecological study of a crinoidal limestone (encrinite) from the Jurassic System of North America. The encrinite is part of a shallow-water tidal facies of the Middle Jurassic Carmel Formation located at Mount Carmel Junction (southwestern Utah, U.S.A.) and may represent one of the youngest shallow-water encrinites in the geological record. In the past, the crinoid at this locality was referred to as Pentacrinus asteriscus, a name used to describe almost all of the crinoid columnals found throughout the Jurassic of the U.S. western interior. However, systematic work indicates that the crinoid is Isocrinus nicoleti and is the first non-endemic crinoid to be reported from North American Jurassic strata. Although articulated pinnules and arms have been found, I. nicoleti occurs predominantly as well-preserved, partially articulated columnals. The crinoids occur within a tidal complex consisting of ooid shoal, tidal channel, and lagoonal facies. The unique environmental and ecological conditions which existed in the southernmost end of the Jurassic North America seaway may have allowed for the development of this crinoid colony and subsequent deposition of the encrinite. [source]

New Phylogenetic Analysis of the Family Elephantidae Based on Cranial-Dental Morphology,

THE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 1 2010
Nancy E. Todd
Abstract In 1973, Vincent Maglio published a seminal monograph on the evolution of the Elephantidae, in which he revised and condensed the 100+ species named by Henry Fairfield Osborn in 1931. Michel Beden further revised the African Elephantidae in 1979, but little systematic work has been done on the family since this publication. With addition of new specimens and species and revisions of chronology, a new analysis of the phylogeny and systematics of this family is warranted. A new, descriptive character dataset was generated from studies of modern elephants for use with fossil species. Parallel evolution in cranial and dental characters in all three lineages of elephants creates homoplastic noise in cladistic analysis, but new inferences about evolutionary relationships are possible. In this analysis, early Loxodonta and early African Mammuthus are virtually indistinguishable in dental morphology. The Elephas lineage is not monophyletic, and results from this analysis suggest multiple migration events out of Africa into Eurasia, and possibly back into Africa. New insight into the origin of the three lineages is also proposed, with Stegotetrabelodon leading to the Mammuthus lineage, and Primelephas as the ancestor of Loxodonta and Elephas. These new results suggest a much more complex picture of elephantid origins, evolution, and paleogeography. Anat Rec, 2010. © 2009 Wiley-Liss, Inc. [source]

Phylogeny and phylogenetic classification of the antbirds, ovenbirds, woodcreepers, and allies (Aves: Passeriformes: infraorder Furnariides)

CLADISTICS, Issue 4 2009
Robert G. Moyle
The infraorder Furnariides is a diverse group of suboscine passerine birds comprising a substantial component of the Neotropical avifauna. The included species encompass a broad array of morphologies and behaviours, making them appealing for evolutionary studies, but the size of the group (ca. 600 species) has limited well-sampled higher-level phylogenetic studies. Using DNA sequence data from the nuclear RAG-1 and RAG-2 exons, we undertook a phylogenetic analysis of the Furnariides sampling 124 (more than 88%) of the genera. Basal relationships among family-level taxa differed depending on phylogenetic method, but all topologies had little nodal support, mirroring the results from earlier studies in which discerning relationships at the base of the radiation was also difficult. In contrast, branch support for family-rank taxa and for many relationships within those clades was generally high. Our results support the Melanopareidae and Grallariidae as distinct from the Rhinocryptidae and Formicariidae, respectively. Within the Furnariides our data contradict some recent phylogenetic hypotheses and suggest that further study is needed to resolve these discrepancies. Of the few genera represented by multiple species, several were not monophyletic, indicating that additional systematic work remains within furnariine families and must include dense taxon sampling. We use this study as a basis for proposing a new phylogenetic classification for the group and in the process erect new family-group names for clades having high branch support across methods. [source]

Lymph node metastases in the lower neck

CLINICAL OTOLARYNGOLOGY, Issue 3 2003
W. Giridharan
Lymph node metastases in the lower neck Current knowledge suggests that lymph node metastases in the lower neck (supraclavicular fossa and posterior triangle) are associated with a poor survival. Very little systematic work has been published on this subject. This was a retrospective study carried out on a database where all patients were entered in a prospective manner over a 35-year period using a standard pro-forma. Data on 168 patients presenting with a lower neck node metastasis were retrieved. The main outcome measures were: association between variables and tumour-specific survival. Data were displayed in contingency tables and analysed by chi-square and categorical modelling. Recurrence and survival were plotted in a cause-specific manner using the Kaplan Meir method. Differences in curves were analysed using the log rank test. Multivariate analysis was carried out using Cox's proportional hazard model. The only association was between site and node level and histology. Head and neck tumours were associated with squamous histology (P = 0.0004) and supraclavicular nodes (P = 0.0047). Survival time was not significantly different when lower-neck lymph node metastasis from the head and neck was compared to non-head and neck metastasis: 5-year survival 30% and 10% respectively (P = 0.1363). Survival with posterior triangle metastases was significantly better than supraclavicular metastases (P = 0. 0059), confirmed on multivariate analysis. Laterality of metastasis had no effect on survival (P < 0.0001). There was no significant difference in survival between squamous and non-squamous metastases on Cox regression (P = not significant). There were 85 head and neck primaries including lymphomas, 53 infraclavicular primaries and 30 unknown primaries. There were 73 squamous cell carcinomas, 27 adenocarcinomas, 34 lymphomas, 28 undifferentiated tumours and six other tumours. Nearly half the primary tumours were below the clavicle. Survival was unaffected by laterality, primary site or histology, but was better for posterior triangle nodes. [source]