International audienceThe study of Devonian Colombian trilobites and inarticulate brachiopods allows to recognize two biostratigraphic levelswithin the Floresta Formation. The first level, in the lower part of the formation, is late Emsian in age, and yields 14 distincttrilobite taxa, including Colombianaspis carvalhoae gen. et sp. nov. The second one, in the upper part of the formation,is assigned to the Givetian based on the co-occurrence of the genera Dipleura and Greenops; this is the first recordof a Givetian age for the upper part of the Floresta Formation. The inarticulate brachiopods collected from the uppermostpart of the formation suggest a Givetian age. Inarticulate brachiopods as well as the trilobites show close affinities withthe North Eastern Americas Realm, but they also suggest European affinities. The late Emsian occurrence of calmoniidsfrom Colombia is indicative of restricted faunal exchanges with the Malvinokaffric Realm

La sous‐famille Asteropyginae regroupe des Trilobites de la Famille Dalmanitidae qui se sont développés pendant environ 40 millions d'années, du Lochkovien au Frasnien (Dévonien). Leur extension géographique, des Appalaches à la Birmanie, et leur diversification spécifique (225 espèces environ), ont subi des variations pendant cette période. La comparaison des changements de paléoenvironnement avec l'évolution des Asteropyginae, en particulier sur la base des courbes de variations eustatiques, montre la possibilité de relations entre les deux phénomènes. Après une période lente de diversification des Asteropyginae au Lochkovien‐Praguien en Europe el en Afrique du Nord, le processus s'accélère au cours de l'Emsien conduisant au nombre maximal de genres et d'espèces. Au passage Emsien‐Eifelien. une phase transgressive provoque une crise importante au sein de ce groupe, Pendant le Givetien et le Frasnien inférieur se produit une deuxième phase de développement, moins importante que la précédente, mais qui est accentuée par la radiation adaptative liée à la migration du groupe vers les Appalaches et l'Afghanistan. Cette phase est interrompue au Frasnien supérieur. Le groupe décline alors et ne franchit pas la limite Frasnien‐Famennien, l'extinction se situe juste sous l'événement ‘Kellwasser supérieur’, phase de transgression maximale. *Trilobites, Asteropyginae, Devonien, Evolution, Environnement. The subfamily Asteropyginae brings together trilobites of the family Dalmanitidae, which developed for about 40 million years from the Lochkovian to the Frasnian (Devonian). Their geographical extension, from the Appalachian Mountains to Burma, and their specific diversification (about 225 species) underwent variations during that time. The comparison of the palaeoenvironmental changes with the evolution within Asteropyginae, particularly on the basis of eustatic variation curves, shows possible relations between the two phenomena. After a slow diversification period of the Asteropyginae in Europe and North Africa during the Lochkovian and the Pragian, the process accelerates in the course of the Emsian, thus leading to the maximum number of genera and species. Near the Emsian‐Eifelian boundary, a transgressive phase produces a dramatic crisis within the group. During the Givetian and the Lower Frasnian a second phase occurs, less important than the former, but which is accentuated by the adaptive radiation linked with the group's migration toward the Appalachians and Afghanistan. An important change occurs during the Upper Frasnian. The group declines and fails to cross the Frasnian‐Famennian boundary; its extinction takes place just beneath the Upper Kellwasser event, the phase of maximum transgression.

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Studies of fossils collected from the Nictaux–Torbrook and Bear River synclines (Nova Scotia) allow a reexamination of the Siluro-Devonian stratigraphy of the Meguma terrane. The location of this terrane relative to the main paleocontinents of the circumatlantic domain during this period is discussed. Wenlockian, Ludlovian, and Pridolian biostratigraphic horizons have been dated. The benthic fauna of the Torbrook Formation are assigned here to the Lochkovian, Pragian, and Lower Emsian. The Pridolian fauna shows northern European affinities. Thus, the Meguma terrane probably belonged to the North Atlantic domain, as for the Avalon terrane, and occupied a southern position in the "Euramerica" plate during this period. The Devonian fauna belongs to the "old world realm" and shows north Gondwanian and Rhenish affinities. As early as the Lochkovian, species known from both the Rhenish and north Gondwanian domains are recognized in Meguma, as well as others reported so far only from northwestern Africa, Iberian Peninsula, and (or) Armorican Massif. The presence of Rhenish fauna confirms the postulated location for the Meguma terrane during the Upper Silurian since this fauna is representative of southern Baltica marginal areas in Europe. On the other hand, the presence of north Gondwanian fauna implies close relationships with western European margin of Gondwana. The lack of a wide oceanic gap separating north Gondwana and Euramerica can explain the faunal exchanges during Lower Devonian times between western Europe and easternmost Appalachian province despite the presence of a physical barrier.

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