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The Givetian platform of the Ardennes Massif records several alternations between a siliciclastic-carbonate ramp and a carbonate shelf. Usually these depositional contexts are considered as a major disruption implying a perturbation of many ecological parameters. We established the impact of these variations on the biodiversity structure through the study of the trophic organisation. Thanks to a previous microfacies analysis, 550 levels of the Mont d'Haurs section in Givet and ten associated environments were precisely defined. Seven palaeotrophic levels are recognized from micropalaeontological data, including benthic, planktonic, heterotroph and autotroph organisms. The spatial and temporal distributions of these levels have been analysed through means of multivariate analyses. The statistic results show that the distribution of the palaeotrophic levels during periods characterized by a mixed ramp is not significantly different than during carbonate shelf influences. These environmental modifications do not affect the community-type. These results support recent studies performed on different benthic communities occurring in the Givetian of the Ardennes Massif. Indeed, trilobite and ostracod faunas of this period appear more affected by global environmental changes as the Kačák (uppermost Eifelian) and Taghanic (late middle Givetian) events. Moreover, along the proximal-distal transect on the platform, the reef constitutes the most singular environment. However, contrary with the Frasnian reefs of the Ardennes Massif, which consist of carbonate mud mounds laying on a deep mixed ramp, there is no trilobite community that appears restricted to Givetian reefs. Thus global bioevents during the Middle Devonian have a more important control on the biodiversity than the platform morphology. These results support the view that at wide scales (spatial and temporal), the biodiversity responds more positively to ecological disturbances. [ABSTRACT FROM AUTHOR]

During the Devonian the sedimentation on the continental shelves of Ardenne Massif and Boulonnais has changed from a mixed siliciclastic-carbonate ramp (Eifelian), through a carbonate barrier reef (Givetian) and then to a detritic influx with local mud-mounds (Frasnian). Here we analysed the faunistic dynamics of the trilobite associations through the changing environment. We used multivariate analyses (clustering and ordering) to discriminate the trilobite associations within 67 different samples. Three previously known communities and one new were recognised: the Eifelian Mixed association, the Givetian Dechenella association and the two Frasnian Bradocryphaeus and Scutellum-Goldius associations. These trilobite faunas present a progressive ecological specialisation. The Mixed association occurs both in the ramp or carbonated (local reef developed on the ramp) facies without any significant difference in its composition. The Dechenella fauna occurs preferentially close to barrier reefs, but can also survive during short periods of detrital input. The two Frasnian communities show a strong relationship with their environment. The Scutellum-Goldius association is only found in reef systems, whereas the Bradocryphaeus flourishes exclusively in lateral facies. [ABSTRACT FROM AUTHOR]

Traditionally, the evolutionary scenarios of Asteropyginae have been organized in two major clades involving four pygidial patterns. The first cladistic analysis performed on the subfamily maintained the organization in two clades, though the phylogenetic relationships between genera were unexpected compared to the traditional scenarios. Moreover, the previous systematic scheme based on pygidial segmentation was rendered obsolete. In this study, we performed a new phylogenetic analysis from well-known taxa and recent discoveries. Sixty species assigned to 36 genera have been analysed from a dataset of 72 characters. Three more species are used as the outgroup. The 79 most parsimonious trees have a length of 492 steps and a retention index of 0.735. Our analysis confirms the monophyly of Asteropyginae excluding the genusProtacanthina. The phylogenetic pattern is unconventional in that a largely pectinate topology is resolved, rather than two clades corresponding to formerly delimited pygidial morphs. Nevertheless, most relationships between genera suggested in the traditional evolutionary scenarios of the subfamily have been recovered, the main differences being the origin of the group. WhereasTreveropygewas usually considered as the origin of the remaining Asteropyginae, the present results instead identifyDestombesinaas the sister group to all remaining members of the subfamily. From the new phylogenetic pattern, the diagnoses of genera are rewritten in a standard way and to delimit clades more accurately. This work implies modified generic assignments for some species and the erection of four new genera:Minicryphaeusgen. nov.,Gandlopsgen. nov.,Morzadecopsgen. nov. andPennarbedopsgen. nov. The systematic position ofErbenochileis also discussed, the genus no longer being assigned to Asteropyginae. http://zoobank.org/urn:lsid:zoobank.org:pub:C42A54C3-2B8E-439A-8DE0-2F35575F7F40 [ABSTRACT FROM AUTHOR]

The Frasnian representatives of Asteropyginae in the Frasnes area (south Belgium) have long been relatively well-documented when compared to other trilobites in the Devonian of the Ardennes (Belgium, northern France). However, examination of the type material and new collecting by the authors indicate that a taxonomic review has become necessary. Two new species of Bradocryphaeus are recorded, B. vanherlei sp. nov. and B. neptuni sp. nov.; one additional species, B. sp. 20, is known from the pygidium alone. New material is recorded of Bradocryphaeus maillieuxi ( Richter & Richter), which has hitherto been scantily illustrated in the literature. The cephalon of Heliopyge helios (Richter & Richter) is redescribed on the basis of new specimens and its holotype pygidium refigured. [ABSTRACT FROM AUTHOR]