Original descriptions of taxa. For coccolithophores, and many calcispheres, these are pages from the Farinacci & Howe Catalog of Calcareous Nannofossils. In other cases (e.g. non-calcifying haptophytes) the data is directly compiled on this site. The "Catalogue of Calcareous Nannofossils" was originally compiled by Prof A. Farinacci 1969-1989, since 2000 it has been updated and extended by Richard Howe - see The Farinacci and Howe Catalog - an Introduction.
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Original Description Diagnosis. Coccoliths which possess a rim composed of three shields, the elements of each shield displaying very little or no imbrication and joined along radial or near radial sutures; the distal shield may be vertically extended. The central area si wide and may be filed with a variety of crossbars and grills.
LM characteristics. Large dark shields in p-c with constituent elements usually visible. Dark to grey in c-p. The three-shielded structure is occasionally seen in side view. Extra details from original publication Remarks. The genus Mazaganella has a morphology quite distinct from most other coccoliths of the Lower Jurassic. The two species included in this genus are both large, elliptical coccoliths which possess a fairly narrow rim composed of three shields of non-imbricating, radial elements and a central area spanned by a composite plate or cross bearing a central spine. The type species, M. pula, has adpressed shields and resembles members of the Cretaceous family Arkhangelskiellaceae, which have a similar shape, rim construction, and central area filling. However, the second species of Mazaganella, M. protensa, which clearly evolved from the first, shows a modification to this rim structure with the distal shield elements being vertically extended. This trend is similar to that seen in the Biscutaceae with the evolution of Calyculus, although this genus possesses only two shields. The only other coccoliths in the Lower Jurassic with a similar rim morphology to M. protensa is a species of Triscutum which is found in the late Toarcian of the Picun Leufu and Brenha sections and in the Middle Jurassic in north-west Europe (Dockerill 1987). Both genera have a similar rim construction with the trend towards vertical extension, first seen in M. protensa, continued in Triscutum. The two genera do differ, however, with species of Triscutum in the Middle Jurassic having complex central area grills as opposed to the composite plate and crosses of Mazaganella. Thus, any evolutionary development between the two genera would have involved central area modifications but as this is often observed in coccolith lineages it appears quite feasible. The two genera Mazaganela and Triscutum are thus thought to be closely related and are grouped together in the Mazaganellacee. The only other three-shielded coccoliths found in the Lower Jurassic, Bussonius prinsii and B. leufuensis, are only superficially similar in structure to Mazaganella and Triscutum and are actually constructed from imbricating and inclined elements and are evolutionary relations of Lotharingius. The Mazaganellaceae is at present placed in the Order Podorhabdales due to the non-imbricating and radial nature of their rim elements. Further work may reveal that their true affinities lie elsewhere as they do not appear typical of this group.
Included genera. Mazaganella, Triscutum.
Range. Sinemurian to Middle Jurassic.
References:
Bown, P. R. (1987a). Taxonomy, evolution, and biostratigraphy of Late Triassic-Early Jurassic calcareous nannofossils. Special Papers in Palaeontology. 38: 1-118. gs
Dockerill, H. J. (1987). Triscutum, a distinctive new coccolith from the Jurassic. Bulletin des Centres de Recherches Exploration-Production Elf-Aquitaine. 11: 127-131. gs
Mazaganellaceae: Catalog entry compiled by <% compiler %>. Viewed: 13-4-2026
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