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Taxonomic Significance (taxonomic + significance)

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Life Sciences100%

Selected Abstracts

Taxonomic significance of pollen morphology in some taxa of Resedaceae

FEDDES REPERTORIUM, Issue 7-8 2002
S.M. El Naggar
Pollen morphology of 13 species and two subspecies belonging to five genera: CayluseaSt.-Hil., OchradenusDelile, RandoniaCoss., OligomerisCambess., and Reseda L. of Resedaceae in Egypt were investigated by light and scanning microscopy. The pollen grains were examined and separated into three pollen types and six subtypes representing the different taxonomic categories on the basis of pollen morphological characters, principally pollen shape, size and exine sculpture. The palynological results are discussed with respect to current systematic treatments of Resedaceae. According to the present palynological results, Resedaceae is a eurypalynous and not a stenopalynous family. In addition, this work came to the conclusions that further studies on the pollen of Resedaceae will be useful in establishing a phylogenetic relationship. Zur taxonomischen Bedeutung der Pollenmorphologie bei einigen Taxa der Familie Resedaceae Mittels Licht- und Rasterelektronen-Mikroskopie wurde die Morphologie der Pollen von 13 Arten und zwei Unterarten aus fünf Gattungen der Familie Resedaceae Ägyptens untersucht: CayluseaSt.-Hil., OchradenusDelile, RandoniaCoss., OligomerisCambess. und Reseda L. Die untersuchten Pollen wurden in drei Typen mit sechs Subtypen unterteilt. Auf der Basis dieser Pollenmorphologie repräsentieren sie verschiedene taxonomische Kategorien: Pollenform, Größe und Skulptur der Exine. Die erzielten Ergebnisse werden in Bezug auf die gegenwärtige Systematik der Resedaceen diskutiert. Entsprechend den hier vorgelegten Daten sind die Resedaceae eine eury- und nicht stenopalynologische Familie. Zusätzlich ergibt sich aus dieser Studie, dass weitere Untersuchungen an Resedaceen-Pollen sinnvoll sind, um phylogenetische Beziehungen aufzufinden. [source]

Growth and maturation of metatarsals and their taxonomic significance in the jerboas Allactaga and Jaculus (Rodentia: Dipodidae)

ACTA ZOOLOGICA, Issue 2 2005
A. A. B. Shahin
Abstract The development of metatarsals in Allactaga tetradactyla, Jaculus jaculus jaculus and J. orientalis was studied and their taxonomic significance was elucidated. The five metatarsals, as a rule, are developed and ossified in the three species, but variation in the fate of the first and fifth metatarsals was found. Ossification begins in the median part of the metatarsals; however, it appears in the distal part of the digits' phalanges, beginning with the third phalanx. The first metatarsal appears just distal to the entocuneiform and develops as a small, separate bone located either in close contact with the distal end of the entocuneiform in A. tetradactyla or completely fused with it, forming a compound bone, in both of J. j. jaculus and J. orientalis. The second, third and fourth metatarsals differentiate distal to the mesocuneiform, ectocuneiform and cuboid, respectively, and fuse with one another into a single long cannon bone in all species. Nevertheless, the fifth metatarsal differentiates ventro-lateral to the head of the fourth metatarsal and ossifies ventral to the head process of the developing cannon bone. The fifth metatarsal either extends to articulate with the phalanges of the fourth digit in A. tetradactyla or persists as a separate, small bone in both of J. j. jaculus and J. orientalis. On this basis, it is concluded that J. jaculus and J. orientalis are both distinct congeneric species and are somewhat more distant from A. tetradactyla. [source]

Brief communication: Contributions of enamel-dentine junction shape and enamel deposition to primate molar crown complexity

AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 1 2010
Matthew M. Skinner
Abstract Molar crown morphology varies among primates from relatively simple in some taxa to more complex in others, with such variability having both functional and taxonomic significance. In addition to the primary cusps, crown surface complexity derives from the presence of crests, cuspules, and crenulations. Developmentally, this complexity results from the deposition of an enamel cap over a basement membrane (the morphology of which is preserved as the enamel-dentine junction, or EDJ, in fully formed teeth). However, the relative contribution of the enamel cap and the EDJ to molar crown complexity is poorly characterized. In this study we examine the complexity of the EDJ and enamel surface of a broad sample of primate (including fossil hominin) lower molars through the application of micro-computed tomography and dental topographic analysis. Surface complexity of the EDJ and outer enamel surface (OES) is quantified by first mapping, and then summing, the total number of discrete surface orientation patches. We investigate the relative contribution of the EDJ and enamel cap to crown complexity by assessing the correlation in patch counts between the EDJ and OES within taxa and within individual teeth. We identify three patterns of EDJ/OES complexity which demonstrate that both crown patterning early in development and the subsequent deposition of the enamel cap contribute to overall crown complexity in primates. Am J Phys Anthropol, 2010. © 2010 Wiley-Liss, Inc. [source]