Trilobites from the Lower Devonian of the south-eastern Anti-Atlas System, South Morocco

Abstract

Trilobiten aus dem Unter-Devon des sªAnti-Atlas, Sª Mit 10 Abbildungen, 11 Tabellen und 16 Tafeln GUNNAR SCHRAUT Kurzfassung in der vorliegenden Arbeit werden Trilobiten aus dem Unter-Devon (Pragium -Ober-Emsium) des sª Anti-Atlas (Sª abgebildet und beschrieben. Es handelt sich dabei haupts~ichlich um Rheinische Formen, welche dem obersten Pragium und dem Ober-Emsium angeh6ren. Altere Taxa aus der Herzynisch-b6hmischen Fazies liegen ausschliel31ich aus dem Pragium vor. 19 Arten und Unterarten konnten von insgesamt 8 verschiedenen Lokalitfiten (Fundpunkte und Profile) aufgefunden werden. Neu sind die folgenden f'ª Taxa: Paralejurus elayounensis n. sp., Phacops (Phacops) saberensis torkozensis n. ssp., Phacops (Phacops) vogeli n. sp., Reedops intermedius chlupaci n. ssp. und Treveropyge marokkensis n. sp. Arduennella maillieuxi (ASSELBERGHS 1923) und Parahomalonotus planus planus (KOCH 1883) werden erstmals aus dem Unter-Devon (oberstes Pragium) von Marokko beschrieben. Die schon bekannten Formen besitzen Vertreter im Rheinischen Schiefergebirge (Deutschland), in der Bretagne (Frankreich), in B6hmen (Tschechische Republik) und in Spanien. Konsequenterweise bedeutet dies, daB die genannten geographischen Bereiche im mittleren und oberen Unter-Devon durch einen flachen Schelf ohne deutlich ausgel~r~igte pal~iobiogeographische Schranken miteinander verbunden waren und/oder geographisch nicht weit auseinander lagen. Abstract[Trilobites from the Lower Devonian of the south-eastern Anti-Atlas System, South Morocco.] --This paper deals with trilobites from the Lower Devonian (Pragian -Upper Emsian) from the south-eastern part of the Anti-Atlas System (South Morocco). Nineteen species and subspecies were determined from 8 different Lower Devonian localities, and these are described, figured and compared to similar forms.The following species and subspecies are new: Paralejurus elayounensis n. sp., Phacops (Phacops) saberensis torkozensis n. ssp., Phacops (Phacops) vogeli n. sp., Reedops intermedius chlupaci n. ssp. and Treveropyge marokkensis n. sp. Most of them represent rhenish forms from the uppermost Pragian and the Upper Emsian. Hercynian-bohemian forms are only present in the Pragian Stage. Arduennella maillieuxi (ASSELBERGHS 1923) and Parahomalonotus planus planus are recorded for the first time in the Devonian of Morocco. Since most of the species are well known forms from the Rheinisches Schiefergebirge (Germany), Brittany (France), Bohemia (Czech Republic) and from Spain there must have been very close paleobiogeographic relations. Therefore a shallow marine shelf with no paleobiogeographical boundaries probably existed between this regions and/or they were located very close together.

Homalonotid trilobites from the Silurian and Lower Devonian of south-eastern Australia and New Zealand (Arthropoda: Trilobita: Homalonotidae)

“…For the morphologically convergent species, it is the continuity of the axial furrow anteriorly in Trimerus (and the fusion of the anteriormost axial ring and pleural rib in Digonus) that distinguishes the genera. Hence, Homalonotus crassicauda from the Emsian of Germany, known only from pygidia and previously interpreted as a temporally disjunct representative of Trimerus (Wenndorf, 1990, Schraut, 2000 clearly belongs in Digonus. The Lochkovian North American H. major Whitfield, 1881 is best assigned to Trimerus rather than to Digonus, because the pygidial axial furrow is deep and distinct anteriorly.…”

“…Pygidia of delphinocephalus differ from those of johannis and vomer in having shallower ring furrows and pleural furrows, and a short spinelike process posteriorly. In outline, the depth of the pygidial furrowing and presence of a posterior spine a single pygidium documented from the Upper Silurian of Morocco (Alberti, 1970, Schraut, 2000 closely resembles pygidia of delphinocephalus and is also assigned to the subgenus. Baldis et al, 1976) describe the species as having a raised glabella with distinct S1-S3, subcircular-ovate swellings on L1, and strongly defined paraglabellar areas, features characteristic of the subgenus.…”

The phacopine trilobite genera Morocops Basse, 2006 and Adrisiops gen. nov. from the Devonian of Morocco

“…This site was described by van Viersen & Holland (2016), who provided a list of trilobite species occurring here. A specimen of Morocops torkozensis (Schraut, 2000a) was collected by one of us (DH) from marls in the upper part of the Hollardops Limestone Member (Khebchia Formation). A log of this locality is not available, but that particular member is a comparatively thin, characteristic regional marker that was described from the nearby locality of Bou Tserfine.…”

“…6) described the type horizon as Rich 3 (= El Ansar Formation, upper Emsian), as an interval between beds 21 and 22, and as the lower part of unit 22 in the lowermost part of the Khebchia Formation. Schraut (2000a) Becker et al (2004a) discussed the Torkoz IIa section and assigned the lower part of unit 22 to the Oui-n-Mesdoûr Formation which underlies the Khebchia Formation, while mentioning abundant P. (P.) saberensis torkozensis and Hollardops mesocristatus in the overlying Hollardops Limestone Member. It leads us to the most parsimonious explanation that the types came from the upper Emsian at Torkoz IIa and more specifically, probably from the basal part of the Khebchia Formation.…”

“…It leads us to the most parsimonious explanation that the types came from the upper Emsian at Torkoz IIa and more specifically, probably from the basal part of the Khebchia Formation. Schraut's (2000a) types are deformed and partially exfoliated specimens. We record a well-preserved specimen from the basal part of the Khebchia Formation at the nearby locality of Tadachacht, which is, as far as could be compared, indistinguishable from the types.…”