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May 9, 2012
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Palaeontology Seminar

 

Trilobitomorph trunk segmentation: a tale of trilobites, myriapods and their genes

 

Javier Ortega-Hernández,

Department of Earth Sciences,

University of Cambridge

 

Thursday 10th May, 16:00
Neil Chalmers Seminar Room, DC2,

 

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Trilobites are some of the most common and abundant metazoans preserved in the fossil record, but little is known about the intrinsic mechanisms that orchestrate their body organization. The phylogenetic position of trilobites within total-group Euarthropoda, however, allows making inferences about the processes of segment formation in these extinct taxa, as some of the fundamental genetic processes for constructing the body segments are remarkably conserved among extant arthropods. In this talk I will tackle the problem of trilobite trunk segmentation by drawing comparisons with conserved mechanisms for tergite formation, and its associated gene expression, in extant representatives. The results obtained from studying the tergite development in the centipede Strigamia maritima revives old trilobite segmentation models, and suggest that these extinct arthropods had a considerable, and largely unsuspected, degree of developmental complexity.

 

 

For additional details on attending this or other seminars see http://www.nhm.ac.uk/research-curation/seminars-events/index.html

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Zoology Seminars


Evolutionary Aspects of Reproductive Biology and Morphology of Caecilian Amphibians (Gymnophiona)

 

Susanne Kühnel
Institut für Spezielle Zoologie und Evolutionsbiologie, Universität Jena

 

TUESDAY 15th May, 12pm

Neil Chalmers Science Seminar Room (DC.LG16)

 

 

Among extant vertebrates, caecilians are still considered one of the least-explored groups. This small clade of modern limbless amphibians has striking anatomical novelties and exhibits variable life histories including diverse modes of parity and parental care. All caecilian amphibians practice internal fertilization with the aid of a unique copulatory organ: the everted male cloaca. Since the caecilian cloaca is ontogenetically a part of the digestive system it is not a separate structure exclusively dedicated for reproduction, like e.g. the squamate hemipenis. Nevertheless, the male cloaca reveals a complex morphology being equipped with longitudinal ridges, tuberosities or crests and displays a high diversity among species. Here I present my work on general and functional morphology aspects of the male and female caecilian cloaca based on specimens housed in natural history museum collections. The recent comparative evolutionary study includes species representing the major clades and reproductive modes. It aims to reveal the evolution of specific genital morphologies and if morphological patterns are linked to reproductive modes or other life history and morphological aspects in this fascinating group of tetrapods.

 

For additional details on attending this or other seminars see http://www.nhm.ac.uk/research-curation/seminars-events/index.html