A poorly diversified trilobite association from the lower Emsian (Lower Devonian) in the Sankt Vith area (East Belgium)

A poorly diversified trilobite association is recorded from an outcrop near the village of Breitfeld, Sankt Vith area, East Belgium. The co-occurrence of Arduennella maillieuxi (Asselberghs, 1923) and Burmeisterella quadrispinosa Wenndorf, 1990 in the Breitfeld locality is suggestive of an early lower Emsian age. The outcropping rocks are provisionally attributed to the lower part of the Our Formation (lower Emsian) as opposed to previous assignment to the “Quartzophyllades de Saint Vith” or Sankt Vith Formation (Pragian). Some nomenclatoral notes are provided on the types of A. maillieuxi as the lectotype could not be traced; a cast of the lectotype as well as several paralectotypes of this species are illustrated. Our material of B. quadrispinosa includes cephalic remains that bring new insights into the morphology of this species. A third species, Treveropyge hellemondi sp. nov., is furthermore described. Palaeobiogeographic affiliations of the trilobite association are discussed. A tentative first step is proposed towards trilobite-based correlations of Emsian strata in the Ardenno-Rhenish Mountains.

Beethovenia n. Gen. y Plicostropheodonta Sokolskaya, 1960 (Strophodontidae Caster, 1939), del Devónico Inferior de Europa occidental

Resumen: Se discute el origen, evolución, relaciones y variabilidad ornamental intra-específica de los géneros estrofodóntidos de Europa occidental y N de África, Beethovenia n. g. y Plicostropheo­donta Sokolskaya, 1960. Se describen y figuran las especies cantábricas Beethovenia bachi n. sp., del Praguiense inferior, Plicostropheodonta crassicosta n. sp., del Emsiense inferior, P. latronensis n. sp. y B. beethoveni n. sp., de la parte inferior del Emsiense superior y B. brahmsi n. sp. y P. diffusa (D. & P. Oehlert, 1896), de la parte superior del Emsiense superior, de la que se aportan nuevos datos sobre localidad y estratotipo en el área de Ferroñes. B. bachi n. sp. debió proceder de la especie cantábrica Fascistropheodonta primaeva García-Alcalde, la más antigua del género, del Lochkoviense más alto o Praguiense más bajo, y originaría, a su vez, durante el Praguiense, formas plicostrofeodontoides próximas a B. acutiplicata (Oehlert y Davoust, 1879). De algún antecesor de estas formas, sur­gieron, a su vez, los tipos morfológicos principales de Plicostropheodonta: el representado por la especie-tipo, P. murchisoni (Verneuil y d’Archiac en d’Archiac y Verneuil, 1842), del Praguiense de Alemania, con pliegues radiales tendiendo a debilitarse y desaparecer hacia el margen de la concha, y el de la forma cantábrica P. crassicosta n. sp. con la tendencia contraria, es decir, con pliegues radia­les haciéndose más fuertes distalmente. El origen y relaciones de las formas cantábricas B. beethoveni n. sp., especie-tipo del nuevo género y B. brahmsi n. sp., y B. ? steiningeri (Drevermann, 1907), del Emsiense superior del Macizo Esquistoso Renano de Alemania y, tal vez, de Bélgica, no está claro aún. En cualquier caso, muchas pequeñas formas plicostrofeodontoides-fascistrofeodontoides del Praguiense y Emsiense del dominio paleogeográfico del Viejo Mundo, asignadas habitualmente a P. murchisoni, en Bélgica, Francia, Pirineos, Zona Centroibérica, Portugal y N de África, deben de pertenecer, más bien, a alguna de las especies citadas de Beethovenia o a otras aún no descritas del mismo género. P. crassicosta n. sp. fue, a su vez, la antecesora de P. latronensis n. sp. y ésta, probablemente, de P. diffusa (D. & P. Oehlert, 1896), en el Emsiense superior. Beethovenia y Pli­costropheodonta evolucionaron de manera paralela a lo largo del Praguiense-Emsiense, con aumento progresivo del tamaño y grosor de las paredes de la concha, fortalecimiento de las estructuras inter­nas y pérdida del carácter plicostrofeodontoide puro de la ornamentación radial que se manifiesta en los orígenes de ambos taxones. Ambos géneros se extinguieron, sin dejar descendencia, antes de comenzar el Devónico Medio.Palabras clave: Beethovenia n. gen., Plicostropheodonta, evolución, taxonomía, Europa occidental, N África, Zona Cantábrica (España).Abstract: The origin, evolution, relationships and intra-specific ornament variability in the Western Europe and North Africa strophodontid Beethovenia n. gen. and Plicostropheodonta Sokolskaya, 1960 are discussed. The Cantabrian (N Spain) species Beethovenia bachi n. sp., from the lower Pragian, Plicostropheodonta crassicosta n. sp., from the lower Emsian, P. latronensis n. sp. and B. beethoveni n. sp., from the lower part of the upper Emsian, and B. brahmsi n. sp. and P. diffusa (D. & P. Oehlert, 1896), from the upper part of the upper Emsian, are described and figured. New data concerning to the P. diffusa locus and stratum typicum in the Ferroñes area are given. B. bachi n. sp. must originate from the Asturian Fascistropheodonta primaeva García-Alcalde, 1992, the oldest Fascistropheodonta species, from the uppermost Lochkovian or lowermost Pragian. In turn, B. bachi could be the predecessor along the Pragian of plicostropheodontoid forms close to B. acutiplicata (Oehlert y Davoust, 1879). From the same lineage probably sprung off along the Pragian-lower Emsian interval the main Plicostropheodonta morphological lineages. These lineages are represented on the one hand by the type-species, P. murchisoni (Verneuil y d’Archiac en d’Archiac y Verneuil, 1842), from the Pragian of Germany, with plicostropheodontoid radial folds weakening and losing near the shell margins, and on the other by the lower Emsian Cantabrian form P. crassicosta n. sp. trending to the opposite side, i. e., with plicostropheodontoid radial ornamentation strengthening distally. The affinities between both the Cantabrian forms B. beethoveni n. sp., the type-species of the new genus, and B. brahmsi n. sp., and the German (and maybe Belgian) species B. ? steinin­geri (Drevermann, 1907), are not yet clear. Anyway, many small plicostropheodontoid-fascistro­pheodontoid Pragian and Emsian forms from the Old World paleogeographic domain (Belgium, France, Pyrenees, Central-Iberian Zone, Portugal and North Africa), usually identified as Plicostro­pheodonta murchisoni, could belong rather to some of the described Beethovenia species or to other not yet described from the same genus. P. crassicosta n. sp. evolved near the lower/upper Emsian boundary, P. latronensis n. sp., and from this latter P. diffusa (D. & P. Oehlert, 1896) at the upper part of the upper Emsian. Beethovenia and Plicostropheodonta evolved rather parallely along the Pragian-Emsian times, by increasing the shell size and solidity, strengthening the internal structures and losing the net plicostropheodontoid radial ornamentation characterizing both taxa beginnings, and became extinct with no descent before the Middle Devonian.Keywords: Beethovenia n. gen., Plicostropheodonta, evolution, taxonomy, Western Europe, N Afri­ca, Cantabrian Zone (Spain).

Early Devonian graptolites and graptolite biostratigraphy, Arctic Islands, Canada

The Early Devonian graptolite fauna of the Arctic Islands comprises the highest species content (17 species) in the world. In spite of this richness, no new species have been recognized; instead already-existing species, scattered around the then-known continents, suggest that relatively complete cosmopolitanism held sway for graptolites. Canadian Arctic biozonation is very similar to schemes elsewhere, consisting of the uniformis and hercynicus biozones in the Lochkovian, falcarius in the lower Pragian, and an expanded yukonensis Biozone in the upper Pragian and the lower Emsian. Three genera and 17 species are recognized: “Monograptus” (microdon cf. microdon, microdon curvatus); Neomonograptus (cf. atopus, aequabilis, bardoensis, falcarius, notoaequabilis); and Uncinatograptus (birchensis, craigensis, hercynicus, langgunensis, parangustidens, subhercynicus, telleri, thomasi, uniformis, yukonensis).