Terreneuvian orthothecid (Hyolitha) digestive tracts from northern Montagne Noire, France; taphonomic, ontogenetic and phylogenetic implications

More than 285 specimens of Conotheca subcurvata with three-dimensionally preserved digestive tracts were recovered from the Terreneuvian (early Cambrian) Heraultia Limestone of the northern Montagne Noire, southern France. They represent one of the oldest occurrences of such preserved guts. The newl...

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Bibliographic Details
Published in:PloS one 2014-02, Vol.9 (2), p.e88583-e88583
Main Authors: Devaere, Léa, Clausen, Sébastien, Alvaro, J Javier, Peel, John S, Vachard, Daniel
Format: Article
Language:English
Subjects:
Animals
Biology
Cambrian
Copyright
Deformation
Digestive system
Digestive tract
Earth Sciences
Feeding Behavior
Filaments
Fossils
France
Gastrointestinal Tract - physiology
Geography
Geology
Infestation
Invertebrates - classification
Invertebrates - physiology
Limestone
Mollusca
Morphology
Ontogeny
Operculum
Paleontology
Phosphates - chemistry
Phylogenetics
Phylogeny
Sipuncula
Taphonomy
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Summary:More than 285 specimens of Conotheca subcurvata with three-dimensionally preserved digestive tracts were recovered from the Terreneuvian (early Cambrian) Heraultia Limestone of the northern Montagne Noire, southern France. They represent one of the oldest occurrences of such preserved guts. The newly discovered operculum of some complete specimens provides additional data allowing emendation of the species diagnosis. Infestation of the U-shaped digestive tracts by smooth uniseriate, branching to anastomosing filaments along with isolated botryoidal coccoids attests to their early, microbially mediated phosphatisation. Apart from taphonomic deformation, C. subcurvata exhibits three different configurations of the digestive tract: (1) anal tube and gut parallel, straight to slightly undulating; (2) anal tube straight and loosely folded gut; and (3) anal tube straight and gut straight with local zigzag folds. The arrangement of the digestive tracts and its correlation with the mean apertural diameter of the specimens are interpreted as ontogenetically dependent. The simple U-shaped gut, usually considered as characteristic of the Hyolithida, developed in earlier stages of C. subcurvata, whereas the more complex orthothecid type-3 only appears in largest specimens. This growth pattern suggests a distinct phylogenetic relationship between these two hyolith orders through heterochronic processes.
ISSN:1932-6203
1932-6203
DOI:10.1371/journal.pone.0088583