Middle Famennian (Late Devonian) ammonoids from the Anti-Atlas of Morocco. 1. Prionoceras

Korn, Dieter; Bockwinkel, Jürgen; Ebbighausen, Volker

doi:10.1127/0077-7749/2014/0405

Cited by 13 publications

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“…Ontogenetic trajectories of the conch width index ( CWI = ww/dm; black dots) and the umbilical width index ( UWI = uw/dm; white dots) and cross‐sections (scale bars 5 mm) in ammonoids to show evolutionary changes in ontogenetic trajectories. A, Prionoceras lamellosum Korn et al ., , MB .C.22756.1 (Prionocerataceae; middle Famennian; Anti‐Atlas, Morocco). B, Mimimitoceras comtum Korn et al ., , MB.C.25022.1 (Prionocerataceae; late Famennian; Anti‐Atlas, Morocco).…”

Section: Resultsmentioning

confidence: 99%

Iterative ontogenetic development of ammonoid conch shapes from the Devonian through to the Jurassic

Walton

Korn

2017

Palaeontology

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We measured longitudinal growth in conch cross-sections of 177 Devonian to Jurassic ammonoid species to test whether conch ontogenetic development parallels the iterative evolution of pachyconic or globular conch shapes. Ontogenetic trajectories of two cardinal conch parameters, conch width index and umbilical width index, show a few common recurring ontogenetic pathways in terms of the number of ontogenetic phases. The most common, with three phases in the conch width index (decrease-increase-decrease) and umbilical width index (increase-decrease-increase), is termed here C-mode ontogeny (after the Carboniferous genus Cravenoceras). Many of the studied globular Palaeozoic and Triassic species (of the latter, particularly the arcestid ammonoids) share principal patterns in the triphasic C-mode conch ontogeny in closely related groups but also between unrelated groups as well. The repetition of conch growth patterns is an example of convergent evolution of the entire life history of globular ammonoids. The studied Jurassic globular shaped ammonoids deviate from the growth patterns seen in earlier groups showing less pronounced ontogenetic trajectories with nearly isometric or weakly asymmetric growth without distinct phases. This trajectory is termed here M-mode ontogeny (after the Jurassic genus Macrocephalites). No major change in the ontogenetic modes of pachyconic and globular ammonoids occurred moving from the Palaeozoic into the Mesozoic; the survivors of the end-Permian extinction event iteratively developed conch ontogenies similar to those of Palaeozoic forms. In contrast, the Triassic-Jurassic boundary marks the major event with the evolution of some cardinal conch parameters relating to globular ammonoid ontogeny.

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Section: Resultsmentioning

confidence: 99%

Iterative ontogenetic development of ammonoid conch shapes from the Devonian through to the Jurassic

Walton

Korn

2017

Palaeontology

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“…, ; Klein & Korn ; Korn et al . , , b ) and also placoderms (Lehman , ; Rücklin , ; Rücklin & Clément in press). One of the localities (30.733572°N, 4.718793°W) is near the summit of a hill, which is covered by the thick supposed Hangenberg Sandstone equivalent.…”

Section: Methodsmentioning

confidence: 99%

The oldest Gondwanan cephalopod mandibles (Hangenberg Black Shale, Late Devonian) and the mid‐Palaeozoic rise of jaws

et al. 2016

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It is widely accepted that the effects of global sea‐level changes at the transition from the Devonian to the Carboniferous are recorded in deposits on the shelf of northern Gondwana. These latest Devonian strata had been thought to be poor in fossils due to the Hangenberg mass extinction. In the Ma'der (eastern Anti‐Atlas), however, the Hangenberg Black Shale claystones (latest Famennian) are rich in exceptionally preserved fossils displaying the remains of non‐mineralized structures. The diversity in animal species of these strata is, however, low. Remarkably, the organic‐rich claystones have yielded abundant remains of Ammonoidea preserved with their jaws, both in situ and isolated. This is important because previously, the jaws of only one of the main Devonian ammonoid clades had been found (Frasnian Gephuroceratina). Here, we describe four types of jaws of which two could be assigned confidently to the Order Clymeniida and to the Suborder Tornoceratina. These findings imply that chitinous normal‐type jaws were likely to have already been present at the origin of the whole clade Ammonoidea, i.e. in the early Emsian (or earlier). Vertebrate jaws evolved prior to the Early Devonian origin of ammonoids. The temporal succession of evolutionary events suggests that it could have been the indirect positive selection pressure towards strong (and thus preservable) jaws since defensive structures of potential prey animals would otherwise have made them inaccessible to jawless predators in the course of the mid‐Palaeozoic marine revolution. In this respect, our findings reflect the macroecological changes that occurred in the Devonian. [Correction added on 28 July 2016 after first online publication: In the Abstract, the sentence “Vertebrate jaws probably … in the Early Devonian” was amended]

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“…Phillippsastrea, Middle Devonian), mixed benthic communities (e.g. Red Fauna; (Korn 1999;Korn et al 2014). This stratigraphical interval often also yields placoderm remains of Dunkleosteus; in the Maïder Basin including complete skeletons in huge nodules up to 4 m long (Lehman 1956(Lehman , 1964(Lehman , 1976 Korn 1999;Korn et al 2014).…”

Section: Konzentrat-lagerstätten Of the Eastern Anti-atlasmentioning

confidence: 99%

“…Red Fauna; (Korn 1999;Korn et al 2014). This stratigraphical interval often also yields placoderm remains of Dunkleosteus; in the Maïder Basin including complete skeletons in huge nodules up to 4 m long (Lehman 1956(Lehman , 1964(Lehman , 1976 Korn 1999;Korn et al 2014). This interval contains also abundant microremains of chondrichthyans in the southern Tafilalt Platform (Ginter et al 2002).…”

Section: Konzentrat-lagerstätten Of the Eastern Anti-atlasmentioning

confidence: 99%

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Fossil‐Lagerstätten, palaeoecology and preservation of invertebrates and vertebrates from the Devonian in the eastern Anti‐Atlas, Morocco

Frey

Pohle

Rücklin

et al. 2020

LET

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In some Devonian strata in the eastern Anti‐Atlas, fossil invertebrates are abundant, display a high taxonomic diversity and indicate many shifts in palaeoecology. This is reflected in changes in faunal composition of invertebrates and vertebrates. Fossils of jawed vertebrates of late Lochkovian and younger age have been recorded and are relatively common with their abundance and diversity increasing towards the Late Devonian. Environmental changes in the Devonian also left their mark in the preservation of vertebrates and invertebrates from the Anti‐Atlas, which varies strongly through time and regionally. This variation partially reflects environmental changes linked with the evolution of small marine basins during the disintegration of the continental shelf of Gondwana in this region, fluctuations of the regional sea level and other environmental changes. To improve our understanding of these ecological changes, of shifts in preservation through the succession and of the formation of Fossil‐Lagerstätten, we analysed the mineral composition of some invertebrate and vertebrate samples of Devonian and Early Carboniferous age by Raman spectroscopy and X‐ray diffraction. Additionally, we characterized some of these Fossil‐Lagerstätten using palaeontological and sedimentological parameters. We examined eight Devonian Konzentrat‐Lagerstätten and two Konservat‐Lagerstätten with soft‐tissue preservation (the Famennian Thylacocephalan Layer and the Hangenberg Black Shale of the southern Maïder). The last two are the first Konservat‐Lagerstätten described from the Devonian of North Africa. The taphonomic and oceanic settings suggest that these Konservat‐Lagerstätten are formed because of stagnation (related to vertical restriction of water exchange and water depth rather than limited spatial water exchange and a lateral restriction) in the relatively small Maïder Basin with limited water exchange with the neighbouring Tafilalt Basin. The temporally low oxygen levels in the Maïder Basin are a possible reason for the reduced chondrichthyan diversity (missing demersal and shallow water species) compared to the Tafilalt Platform.

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Middle Famennian (Late Devonian) ammonoids from the Anti-Atlas of Morocco. 1. Prionoceras

Cited by 13 publications

References 0 publications

Iterative ontogenetic development of ammonoid conch shapes from the Devonian through to the Jurassic

Iterative ontogenetic development of ammonoid conch shapes from the Devonian through to the Jurassic

The oldest Gondwanan cephalopod mandibles (Hangenberg Black Shale, Late Devonian) and the mid‐Palaeozoic rise of jaws

Fossil‐Lagerstätten, palaeoecology and preservation of invertebrates and vertebrates from the Devonian in the eastern Anti‐Atlas, Morocco

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