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The chitinozoans from the Ludlow series (silurian) of the type area and adjacent regions.

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posted on 2015-11-19, 09:03 authored by Stuart John Eyre. Sutherland
Chitinozoans have been recovered from throughout the Ludlow Series of the type area around Ludlow and adjacent regions. Collections contain 12 genera and 42 species including 11 new species: Calpichitina (Calpichitina) granosa, Eisenackitina toddingensis, Cingulochitina gorstyensis, Belonechitina mortimerensis, Rhabdochitina wakefieldi, Ancyrochitina aymestreyensis, Ancyrochitina gogginensis, Ancyrochitina narcissus, Angochitina milleri, Gotlandochitina dinhamensis, Gotlandochitina swifti. and 21 forms under open nomenclature. Conochitina dominates the late Wenlock and early Gorstian assemblages with Cingulochitina more common in the later Gorstian. The late Gorstian is characterised by species belonging to Belonechitina. Chitinozoan abundance and diversity decreases throughout the late Ludfordian, where Eisenackitina philipi often dominates assemblages. A detailed biostratigraphy has permitted a greater biostratigraphical resolution than was previously possible using chitinozoans. A scheme of 12 informal chitinozoan biozones is established for the type Ludlow Series. Chitinozoans have been used to test oceanic circulation models. Changes in chitinozoan assemblages have identified an event within the Middle Elton Formation (Gorstian Stage) and from the base of the Lower Leintwardine Formation (Ludfordian Stage). As the radiation event in the Gorstian occurs within the lithologically homogeneous Middle Elton Formation, it is concluded that chitinozoan faunas are not facies dependent. The faunal turnover in the Middle Elton Formation and the Lower Leintwardine Formation is believed to be related to changes in global climate and nutrient availability on the shelf. A distinctive chitinozoan assemblage is recorded from the top of the Lower Bringewood Formation and includes C. (Calpichitina) granosa, A. narcissus, Fungochitina pistilliformis and significant numbers of Angochitina elongata. This assemblage is repeated at the base of the Ludfordian. These species are regarded as Lazarus taxa and interpreted as responding to specific environmental conditions on the shelf. Due to the hermetically sealed nature of the chitinozoan vesicle and their chain forming habit, the idea that chitinozoans most likely represent the eggs of a marine metazoan is generally supported.


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University of Leicester

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  • Doctoral

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  • PhD



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