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

Viersen, Allart P. Van; Koppka, Jens

doi:10.3140/bull.geosci.1610

Cited by 6 publications

(9 citation statements)

References 15 publications

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“…), A. speculator (Alberti, ), Morocops chattertoni (Khaldi et al ., ) ( Morocops Basse, = Barrandeops McKellar & Chatterton, ; see van Viersen et al . ), and M . granulops (Chatterton et al ., ).…”

Section: Methodsmentioning

confidence: 94%

Functional integration for enrolment constrains evolutionary variation of phacopid trilobites despite developmental modularity

et al. 2019

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Modularity and integration are variational properties expressed at various levels of the biological hierarchy. Mismatches among these levels, for example developmental modules that are integrated in a functional unit, could be informative of how evolutionary processes and trade-offs have shaped organismal morphologies as well as clade diversification. In the present study, we explored the full, integrated and modular spaces of two developmental modules in phacopid trilobites, the cephalon and the pygidium, and highlight some differences among them. Such contrasts reveal firstly that evolutionary processes operating in the modular spaces are stronger in the cephalon, probably due to a complex regime of selection related to the numerous functions ensured by this module. Secondly, we demonstrate that the same pattern of covariation is shared among species, which also differentiate along this common functional integration. This common pattern might be the result of stabilizing selection acting on the enrolment and implying a coordinate variation between the cephalon and the pygidium in a certain direction of the morphospace. Finally, we noticed that Austerops legrandi differs slightly from other species in that its integration is partly restructured in the way the two modules interact. Such a divergence can result from the involvement of the cephalon in several vital functions that may have constrained the response of the features involved in enrolment and reorganized the covariation of the pygidium with the cephalon. Therefore, it is possible that important evolutionary trade-offs between enrolment and other functions on the cephalon might have partly shaped the diversification of trilobites.

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Section: Methodsmentioning

confidence: 94%

Functional integration for enrolment constrains evolutionary variation of phacopid trilobites despite developmental modularity

et al. 2019

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“…1); Khebchia Formation, upper Emsian. A locality log is unavailable but the sequence is very similar to that in Bou Tserfine (van Viersen et al, 2017). Numerous complete, at times slightly disarticulated trilobites occur in a marly bed, informally called Cyphaspis couche, near the summit of the Hollardops Limestone Member.…”

Section: Localities (Morocco)mentioning

confidence: 93%

“…and Psychopyge sp. (Becker et al, 2004c;Brett et al, 2012;van Viersen & Holland, 2016;van Viersen et al, 2017;van Viersen & Lerouge, 2019;AV, pers. comm.…”

Section: Palaeoecology Of Trilobites From the Basal Khebchia Formatio...unclassified

Functional morphology, coaptation and palaeoecology of Hollardops (Trilobita, Acastidae), with descriptions of new species and two new genera from the Devonian of Morocco

Viersen¹,

KLOC²

2022

Geol. Belg.

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A group of asteropygine trilobites with 10 thoracic segments from the lower Emsian to lowermost Eifelian of western Europe and northwest Africa is deemed monophyletic. Available names for this clade are Hollardops Morzadec, 1997, Philipsmithiana Lieberman & Kloc, 1997, Modellops Lieberman & Kloc, 1997 and Pennarbedops Bignon & Crônier, 2013, the first of which has priority. Well-preserved Hollardops specimens from southern Morocco have revealed previously undescribed details of the mineralised exoskeleton that are interpreted here as coaptative and sensory devices. It is proposed that Hollardops, like many other asteropygines, practised a dual mode of coaptation: fully locked enrolment was alternated with a retracted pygidium, allowing temporary influx of oxygenated seawater and excretion through slits between the pygidial lappets. This putative ‘breathing device’ enabled the trilobite to remain enrolled for a longer period of time while maintaining vital body functions. A poor understanding of the problematic type species of Hollardops, H. mesocristatus (Le Maître, 1952), has clouded actual diversity in Algeria and Morocco. Hollardops klugi sp. nov. is the oldest known member of the genus and extends its confirmed stratigraphic range into the lower Emsian. Two species, H. kyriarchos sp. nov. and H. multatuli sp. nov., are recorded from just above the base of the upper Emsian. Additionally, H. angustifrons sp. nov., H. luscus sp. nov. and the first well-preserved specimens of H. boudibensis Morzadec, 2001 are recorded from the upper Emsian. The types of H. hyfinkeli (Lieberman & Kloc, 1997) and H. burtandmimiae (Lieberman & Kloc, 1997) are refigured and original species concepts reiterated. Feruminops Haas, 1968, including its junior subjective synonym Morzadecops Bignon & Crônier, 2013, from the lower Emsian of Morocco and Türkiye, may comprise the sister group of Hollardops. Additionally, the enrolment strategies and systematics of several other members of Asteropyginae are discussed. Platykardiapyge gen. nov. (type species: Metacanthina maderensis Morzadec, 2001) is erected for a group of Pragian–early Emsian asteropygines from Morocco, Spain and Türkiye with a widely heart-shaped pygidium and comparatively many pygidial pleurae, among other features. Bignonops gen. nov. (type species: Kayserops tamnrhertus Chatterton et al., 2006) is erected for some species previously included in Gandlops Bignon & Crônier, 2013. Minicryphaeus suavius sp. nov. is described from the lower Emsian of Morocco. The identity and generic affinity of the oldest known asteropygine, Ganetops gdoumontensis (Asselberghs, 1930) from the Pridolian of Belgium, are discussed.

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“…Basse (2003) recorded a second pygidium from the Lauch Formation that he tentatively assigned to his species while commenting that its morphology is not very representative. van Viersen et al (2017b), who suggested that a descendant of the latter was first able to cross the Rheic Ocean in the earliest Eifelian. Notwithstanding the similarities between early Eifelian Morocops and Geesops species, the middle Eifelian marks a change in the general morphology of Geesops: the glabella becomes narrower (tr.…”

Section: Holotype Irsnb A13273 Articulated Specimen (Figs 4e-h)mentioning

confidence: 99%

“…It has dorsoventrally low eyes with maximally four lenses per dorsoventral files, as against five in all our specimens and the holotype. It also has the palpebral lobe lower than the palpebral area, among other features to potentially link it to Morocops (van Viersen et al, 2017b).…”

Section: Holotype Irsnb A13273 Articulated Specimen (Figs 4e-h)mentioning

confidence: 99%

Early Middle Devonian trilobites and events in the Nismes – Vireux-Molhain area, southern border of the Dinant Synclinorium (Belgium, northern France)

Viersen

Taghon²,

Magrean³

2019

Geol. Belg.

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Well-preserved trilobite specimens are recorded from Eifelian strata between the villages of Nismes (southern Belgium) and Vireux-Molhain (northern France). In the area of study the lower Eifelian Vieux Moulin Member of the Jemelle Formation crops out. The diversified trilobite associations of this unit occur in dark shales and siltstones during a deepening phase and replace the comparatively poorly diversified trilobite fauna of the underlying Eau Noire Formation. This overturn of the local trilobite fauna might, in part, be considered a regional expression of the globally recognised Choteč Event. A marked influx of exotic trilobites in the Vieux Moulin Member is provisionally referred to the local Vieux Moulin Event. Trilobite diversity peaked in the middle Eifelian part (Chavées Member) of the Jemelle Formation before drastically dropping in the upper part of this formation. The manifestations in the Ardennes of the eastern North American Bakoven and Stony Hollow Events can neither be confirmed nor rejected based on the currently available data. New taxa from the early Eifelian part of the Jemelle Formation in the area of study are Asteropyge boeckae sp. nov., Asteropyge eonia sp. nov., Asteropyge filoxenia sp. nov., Cyphaspis insolata sp. nov., Cyphaspis iuxta sp. nov., Diademaproetus pertinax sp. nov., Geesops icovellaunae sp. nov., Gerastos kesselaeri sp. nov., Kettneraspis eftychia sp. nov., Pedinopariops ceuthonymus sp. nov., Pedinopariops richterianus geminus ssp. nov., Scabriscutellum archinalae sp. nov., Septimopeltis akatastasia sp. nov. and Tropidocoryphe insciens sp. nov. Our material includes exceptionally rare, well-preserved specimens from the famous “Mur des douaniers” locality near Vireux-Molhain. Additionally, Astycoryphe rugocauda sp. nov. is described from the lower Eifelian Couvin Formation (southern Belgium) and Gerastos silvicultrix sp. nov. from the uppermost Emsian Heisdorf Formation (German Eifel).

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

Cited by 6 publications

References 15 publications

Functional integration for enrolment constrains evolutionary variation of phacopid trilobites despite developmental modularity

Functional integration for enrolment constrains evolutionary variation of phacopid trilobites despite developmental modularity

Functional morphology, coaptation and palaeoecology of Hollardops (Trilobita, Acastidae), with descriptions of new species and two new genera from the Devonian of Morocco

Early Middle Devonian trilobites and events in the Nismes – Vireux-Molhain area, southern border of the Dinant Synclinorium (Belgium, northern France)

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