Nouvelles études micropaléontologiques sur le stratotype de la limite Campanien-Maastrichtien à Tercis (SO France) : les gilianelles (microproblematica) extraites par acétolyse

Odin, G.S.; Lethiers, Alexandre

doi:10.4267/2042/6697

Cited by 5 publications

(4 citation statements)

References 6 publications

(4 reference statements)

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“…Several morphologies have been described since, confirming that gilianelles constitute an original, cohesive group. Similar microproblematica were illustrated twenty years ago by Willems (1990), but their significance as an original microfossil group has been realized only recently (Odin and Lethiers 2006; Odin 2008 a ). A summary of current knowledge of this group is presented here in English for the first time, with the hope of arousing the attention of the palaeontological community.…”

supporting

confidence: 61%

“…Tests of gilianelles show morphological adaptations which make it likely that they occupied various niches. Most are clearly consistent with a planktonic mode of life, but a few possibly were benthic (Odin and Lethiers 2006; Odin 2009 b ). An adaptation to a planktonic life style was assumed by Odin and Lethiers (2006) to be reflected in the development of projections (Pl.…”

Section: Distributionmentioning

confidence: 87%

“…Most are clearly consistent with a planktonic mode of life, but a few possibly were benthic (Odin and Lethiers 2006; Odin 2009 b ). An adaptation to a planktonic life style was assumed by Odin and Lethiers (2006) to be reflected in the development of projections (Pl. 1, species 2, 7), the orientation of the test along an axis of symmetry with an aboral prolongation acting as a ballast keel (see Pl.…”

Section: Distributionmentioning

confidence: 87%

“… Gilianelles represent the remains of living organisms, in the form of a calcareous unilocular envelope called a test. A single aperture invariably is present, its diameter being about one‐tenth of that of the test. Exclusive of expansions, test size ranges between 80 and 200 μ m. Tests invariably display basic axial symmetry. In life, the aperture was situated at the top (see video in Odin and Lethiers 2006). Test wall thickness is fairly constant (15 μ m); wall consists of a single layer of carbonate crystals, arranged roughly radially. Test surface with a crochet‐like nanostructure (‘structure en napperon’ in French), the ‘stitches’ being 5–10 μ m wide and usually arranged radially and concentrically. …”

Section: General Characteristics and Diversity Of Gilianellesmentioning

confidence: 99%

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Gilianelles: Late Cretaceous microproblematica from Europe and Central America

Odin

2011

Palaeontology

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During the last two decades, a range of microfossils have been collected from strata of Late Cretaceous (Coniacian-Maastrichtian) age. The name gilianelles has been coined to accommodate these microproblematica. On the basis of many thousands of specimens, typical features of this group have now been assessed. Distinctive traits are calcareous unilocular, basically axially symmetrical test, in the size range 80-200 lm, with a single-layered wall of radially arranged crystals, 15 lm thick, the outer surface with a crochet-like nanostructure, a small-sized aperture (one tenth of test diameter), situated on the upper surface in vivo. Secondary criteria include modification of axial test symmetry into radial or bilateral symmetry, development of expansions, either spiny or laminar and presence of longitudinal and latitudinal ornament. To date, 60 taxa have been described from northern Spain to northern Germany and from Central America. Evolutionary patterns of gilianelles are diverse, with both short-and long-ranging forms, some of which comprise lineages that were affected by a marked crisis dated at about 73 Ma. This event is here illustrated by the tribe Coraliellini, of which a key taxon, Coraliella cognatio, is described as new. Previous interpretations of Gilianelles as dinoflagellate cysts are discussed and rejected.

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supporting

confidence: 61%

Section: Distributionmentioning

confidence: 87%