Devonian

Flood-dominated fluvio-deltaic system: a new depositional model for the Devonian Cabeças Formation, Parnaíba Basin, Piauí, Brazil

by Luiza Ponciano

Ponciano and Della Fávera (2009)
Anais da Academia Brasileira de Ciências 81(4): 769-780

The depositional model of the Cabeças Formation is re-evaluated in the context of the Devonian paleogeography of the... more The depositional model of the Cabeças Formation is re-evaluated in the context of the Devonian paleogeography of the Parnaíba Basin, and with particular reference to similarities between the formation’s facies associations on the eastern border of the basin and the flood-dominated fluvio-deltaic system facies that have been discussed in recent literature. The widespread occurrence and nature of sigmoidal clinoforms (with asymptotic cross-stratification and climbing ripples) of the Cabeças Formation are here considered as strong evidence of flood-influenced depositional settings. Sandy strata of the Passagem Member, in the vicinity of Pimenteiras and Picos (Piauí State), are interpreted as the distal part of fine-grained mouth-bar deposits interbedded with delta-front sandstone lobes showing hummocky cross-stratification. Richly fossiliferous levels, with diverse megainvertebrates and plant cuticles, occur within the delta-front lobes and the distal mouth-bar deposits, reflecting continuation of shallow marine conditions.


O modelo deposicional da Formação Cabeças é reinterpretado no presente estudo com base no contexto paleogeográfico da Bacia do Parnaíba durante o Devoniano e na similaridade entre as fácies encontradas na Formação Cabeças com as fácies características dos sistemas flúvio-deltaicos dominados por inundações. O tipo das clinoformas sigmoidais (com estratificação cruzada assintótica e laminação cruzada cavalgante), e a sua predominância na Formação Cabeças, são consideradas como as principais evidências da influência de inundações nesta unidade. Depósitos do Membro Passagem, localizados nos arredores das cidades de Pimenteiras e Picos, são interpretados como o componente distal de um tipo de barra de desembocadura com a predominância de arenitos finos a conglomeráticos, intercalados com lobos arenosos tabulares de frente deltaica com estratificação cruzada hummocky. Diversos intervalos fossilíferos, com abundantes macrofósseis de invertebrados e fragmentos vegetais, ocorrem tanto nos lobos de frente deltaica quanto nos depósitos distais de barra de desembocadura, ainda no contexto de um paleoambiente marinho raso.
Palavras chave: Bacia do Parnaíba, Devoniano, Formação Cabeças, sistema flúvio-deltaico dominado por inundações, lobos de frente deltaica, depósitos de barra de desembocadura, estratificação cruzada hummocky.

A new species of Ivdelinia Andronov, 1961 from the Moroccan Givetian and its palaeoecological and palaeobiogeographical implications

by Christian Klug

Franchi F, Schemm-Gregory M, Klug C (2012)

The collection and study of benthic fauna from Middle Devonian carbonate buildups of the Maider Basin in the eastern... more The collection and study of benthic fauna from Middle Devonian carbonate buildups of the Maider Basin in the eastern Anti-Atlas of Morocco permitted the taxonomic revision of previously described brachiopods from this area. Rhynchonellids dominate the brachiopod fauna. In this work, however, the focus is put on the description of a new gypidulid species, Ivdelinia pulchra, which belongs to the family Gypidulidae (subfamily Ivdelininae), found among the brachiopods from the Aferdou el Mrakib reef mound. It represents the youngest Ivdelinia species so far described and is compared with other ivdelinids. Ivdelinia pulchra occurs as densely packed communities which lived in a carbonate predominant environment during the earlier stage of reef mound growth, suggesting a more or less allochthonous state of these communities. However, this taxon does not properly belong to the reef guild. In addition we discuss the palaeoecology of the new species.

An Early Devonian nonagonal orthoconic cephalopod from Morocco

by Christian Klug

CHRISTIAN KLUG, BJÖRN KRÖGER AND KENNETH DE BAETS

A new specimen of a Dalejan (Late Emsian, Early Devonian) orthoconic cephalopod is described from the southwestern... more A new specimen of a Dalejan (Late Emsian, Early Devonian) orthoconic cephalopod is described from the southwestern Tafilalt (Anti-Atlas, Morocco). It has a nonagonal cross section (with nine edges) and resembles Kionoceras. Since it differs in several characters from Kionoceras, we introduce the new taxon Amessouiceras enneagon gen. et. sp. nov. and shortly discuss evolutionary events among cephalopods in the Early Devonian.

Zlíchovian faunas with early ammonoids from Morocco and their use for the correlation between the eastern Anti-Atlas and the western Dra Valley.

by Christian Klug

DE BAETS, K., KLUG, C. & PLUSQUELLEC, Y. (2010)

Two sections were sampled and measured at Mdâour-El-Kbîr (Dra Valley, western Anti-Atlas) and at eastern Ouidanemore Two sections were sampled and measured at Mdâour-El-Kbîr (Dra Valley, western Anti-Atlas) and at eastern Ouidane
Chebbi (Tafilalt, eastern Anti-Atlas). In situ elements of two partially limonitized and one carbonatic fauna were found
in both sections. We report this fauna from the upper Merzâ-Akhsaï Formation and the lower Mdâour-el-Kbîr Formation
at Mdâour-el-Kbîr for the first time. Based on these faunas, we recorded a correlation of the early Emsian (Zlíchovian)
strata in the Tafilalt and the Dra Valley regions, which are about 350 km apart. Additionally, new ammonoid finds
(Teicherticeras cf. senior, Lenzites gesinae, Weyeroceras angustus) are figured and described including the stratigraphic
context. The diagnoses of Lenzites gesinae and Weyeroceras angustus are emended. Tabulate corals (Michelinia
mdaourensis sp. nov., Petridictyum sp.) found in both the Tafilalt and Dra Valley are figured and described for the first
time. • Key words: early Emsian, Ammonoidea, Tabulata, Micheliniidae, biostratigraphy, Anti-Atlas, Morocco.

Devonian pearls and ammonoid−endoparasite co−evolution

by Christian Klug

by KENNETH DE BAETS, CHRISTIAN KLUG, and DIETER KORN

Raised shell projections on the inner shell walls that form pits on the internal moulds of Devonian ammonoids have... more Raised shell projections on the inner shell walls that form pits on the internal moulds of Devonian ammonoids have been
known for several decades. New specimens from Morocco reveal novel details of these structures; most, if not all, of
which consist of a capsule of ammonoid shell that covers tiny tubes attached to the outer (= lateral or ventral) shell wall
from the inside. In accordance with comparable Recent occurrences of similar structures in molluscs, we use the term
“pearls” for these structures and the pits they form on the internal moulds. The nature of these encapsulated tubes is de−
scribed and discussed. Because of the presence of these tubes inside the pearls, pearl arrangement, and their similarity to
Recent mollusc occurrences, the tubes are interpreted as traces of parasitoses. The pearls and pits were grouped into five
types based on differences in morphology, size, and arrangement. Then, having used these traits to perform a simple
cladistic analysis, the resulting cladogram was compared to the phylogeny of ammonoids. Based on this comparison, it
appears likely that the parasites underwent a co−evolution with the ammonoids, which lasted 10 to 15 Ma. Patterns of evo−
lutionary events include co−speciation, “drowning on arrival” (end of parasite lineage near base of a new host clade), and
“missing the boat” (parasite lineage does not adapt to a new host clade, thus not evolving a new parasite clade). Because of
the lack of fossilised soft tissue, only speculations can be made about the systematic affiliation of the parasites, their
life−cycle, infection strategy, and ecological framework. Some co−occurring bivalves also have pits reminiscent to struc−
tures caused by trematodes in Recent forms. Based on the available information, the tubes are interpreted as artefacts of
trematode infestations, which, if correct, would extend the fossil record of parasitic trematodes into the Early Devonian.

Lucky rugose corals on crinoid stems: unusual examples of subepidermal epizoans from the Devonian of Morocco

by Christian Klug

    BŁAŻEJ BERKOWSKI,
    CHRISTIAN KLUG (2012)

In the fossil record, evidence for true epizoans, i.e. living animals inhabiting other living host-animals, is rather... more In the fossil record, evidence for true epizoans, i.e. living animals inhabiting other living host-animals, is rather rare. A host reaction is usually needed to proof the syn vivo-settling of the epizoan. Herein, we provide a first report of such an epizoan biocoenosis from various strata of the Early Devonian of Hamar Laghdad, the world-renowned Moroccan mud-mound locality. In this case, solitary rugose corals settled as larvae on crinoid stems, perhaps at a spot where the epidermis was missing for some reason (injury, disease). Both the crinoid and the coral began to grow around each other. By doing so, the affected crinoid columnals formed a swelling, where ultimately only an opening slightly larger than the coral orifice remained. We discuss both macroecological and small-scale synecological aspects of this biocoenosis. The coral profited from its elevated home because it reached into more rapid currents providing the polyp with more food than at the densely populated seafloor, which was probably covered by a coral-meadow around the mounds and hydrothermal vents. □Corals, crinoids, Early Devonian, epizoans, Morocco, Rugosa.

A new species of Ivdelinia Andronov, 1961 from the Moroccan Givetian and its palaeoecological and palaeobiogeographical implications

by Christian Klug

Franchi F, Schemm-Gregory M, Klug C (2012)

The collection and study of benthic fauna from Middle Devonian carbonate buildups of the Maider Basin in the eastern... more The collection and study of benthic fauna from Middle Devonian carbonate buildups of the Maider Basin in the eastern Anti-Atlas of Morocco permitted the taxonomic revision of previously described brachiopods from this area. Rhynchonellids dominate the brachiopod fauna. In this work, however, the focus is put on the description of a new gypidulid species, Ivdelinia pulchra, which belongs to the family Gypidulidae (subfamily Ivdelininae), found among the brachiopods from the Aferdou el Mrakib reef mound. It represents the youngest Ivdelinia species so far described and is compared with other ivdelinids. Ivdelinia pulchra occurs as densely packed communities which lived in a carbonate predominant environment during the earlier stage of reef mound growth, suggesting a more or less allochthonous state of these communities. However, this taxon does not properly belong to the reef guild. In addition we discuss the palaeoecology of the new species.

Morphologie et variations du toit crânien du Dipneuste Scaumenacia curta (Whiteaves) (Sarcopterygii), du Dévonien supérieur du Québec

by Richard Cloutier

Author: Cloutier, R.
Year: 1997
Reference: Geodiversitas, 19: 59–105.

L'étude d'une centaine de crânes du dipneuste Scaumenacia curta (Whiteaves) a permis de mettre en évidence des patrons... more L'étude d'une centaine de crânes du dipneuste Scaumenacia curta (Whiteaves) a permis de mettre en évidence des patrons de variations intraspécifiques. Ces variations s'organisent selon les catégories suivantes : (1) changements de proportions, (2) concurrence spatiale (mineure et majeure), (3) plasticité dans le patron des lignes de fossettes, (4) fusion, et (5) présence d'os anamestiques. Le parcours des lignes de fossettes moyennes et postérieures ainsi que la fusion de croissance des os de la série latérale (os L1 à N) sont les deux caractères qualitatifs les plus variables. Les fusions entre les éléments osseux d'une même série (série médiane et latérale) sont fréquents et se produisent surtout sur le parcours des canaux sensoriels profonds. L'étude des statistiques bidimensionnelles et l'analyse des composantes principales ont permis d'identifier des variations de forme reliées à la taille (allométrie) et des fluctuations de la symétrie bilatérale des os de la série médiane. Les patrons de variation crânienne de Scaumenacia sont comparés à ceux d'autres taxa.

Quantitative approach of diversity and decline in late Palaeozoic trilobites. (PDF available on request)

by Rudy Lerosey-Aubril

LEROSEY-AUBRIL R. & FEIST R. 2012. Quantitative approach of diversity and decline in late Palaeozoic trilobites. In: Talent, J.A. (Ed.), Earth and Life: Global Biodiversity, Extinction Intervals and Biogeographic Perturbations through Time, pp. 535-555. Springer Publishing.

Quantitative data reveal a complex evolution of late trilobite diversity. In the Mid- to early Late Devonian, a series... more Quantitative data reveal a complex evolution of late trilobite diversity. In the Mid- to early Late Devonian, a series of extinction events led to a drastic taxonomic impoverishment. In the Famennian, while only two orders remained, originations started to compensate still high extinction rates marking the onset of a remarkable diversification. Though interrupted by the major Hangenberg turnover, the general diversification trend accelerated in the Tournaisian whilst extinctions became modest. Originations notably diminished during the Viséan and the Serphukovian, making the diversity to step down at the level of the Frasnian. It has never been much higher thereafter, despite a profound restructuring of trilobite communities in the early Pennsylvanian permitting the progressive domination of ditomopygines. After another drop in the Kasimovian a period of stasis occurred with very low diversity levels and almost no renewal. The last diversification burst took place in the Wordian, but it ceased rapidly in the Capitanian when the degradation of environmental conditions started to inhibit originations. Thus, the extinction of the Trilobita at the end of the Permian resulted from the disappearance of merely a handful of genera.

Late ontogeny and hypostomal condition of a new cyrtosymboline trilobite from the Famennian of Morocco.

by Rudy Lerosey-Aubril

LEROSEY-AUBRIL R. & FEIST R. 2006. Late ontogeny and hypostomal condition of a new cyrtosymboline trilobite from the Famennian of Morocco. Palaeontology, 49(5): 1053-1068. 

A new species of trilobite, Cyrtosymbole rectifrons, from Famennian marlstones in the south-eastern vicinity of Erfoud... more A new species of trilobite, Cyrtosymbole rectifrons, from Famennian marlstones in the south-eastern vicinity of Erfoud (Tafilalt, Morocco), is described. Silicified sclerites of various sizes allow the description of its late growth sequence, which demonstrates that some characteristic features of the Cyrtosymbolinae are acquired during late ontogeny. Precise examination of exceptionally well-preserved material enables reconstruction of the in situ  position of the adult hypostome, together with a reconsideration of its relation to the dorsal exoskeleton and its morphofunctional capacity for movement. The natant hypostomal condition inferred for C. rectifrons suggests that it is not always possible to deduce the nature of hypostomal attachment from the dorsal morphology alone.

Ontogeny of a new cyrtosymboline trilobite from the Famennian of Morocco.

by Rudy Lerosey-Aubril

LEROSEY-AUBRIL R. & FEIST R. 2005. Ontogeny of a new cyrtosymboline trilobite from the Famennian of Morocco. Acta Palaeontologica Polonica, 50(3): 449-464.

Abundant trilobite remains were recovered from late mid−Famennian marlstones from various sites in Eastern Tafilalet,... more Abundant trilobite remains were recovered from late mid−Famennian marlstones from various sites in Eastern Tafilalet, southeast Morocco. All belong to a single taxon previously identified as Cyrtosymbole (Waribole) prima. This taxon is designated the type species of Osmolskabole gen. nov. A redefinition of this species, including the description of newly discovered, disarticulated exuviae both in limestone and silicified state of preservation, is given. In particular, silicified sclerites of various sizes allow the first complete growth series of a cyrtosymboline proetid to be presented. The close morphological resemblance of its protaspid stages to known proetoid larvae emphasizes the homogeneity of the early ontogeny in this superfamily. The Famennian proetoid anaprotaspis is also of comparable size to that of other Devonian proetoid larvae. However, their size−range is much less than that observed in Carboniferous larvae. This suggests that the survival of proetoid trilobites at the Frasnian - Famennian Kellwasser crisis did not result from a modification of the developmental strategy, as it might have been the case at the terminal Devonian extinction event. Moreover, O. prima possesses a plectrum from the metaprotaspid to the mid meraspid periods. This implies that the natant hypostomal condition is not steadily acquired early in the ontogeny of the Proetida. Thus we preclude the use of this character in the diagnosis of this order.

Ontogeny of Drevermannia and the origin of blindness in Late Devonian proetoid trilobites.

by Rudy Lerosey-Aubril

LEROSEY-AUBRIL R. 2006. Ontogeny of Drevermannia and the origin of blindness in Late Devonian proetoid trilobites. Geological Magazine, 143(1): 89-104.

Numerous silicified and calcareous sclerites of various sizes, recovered from the latest Famennian of Thuringia... more Numerous silicified and calcareous sclerites of various sizes, recovered from the latest Famennian of Thuringia (Germany), allow the description of the first complete growth series of a blind proetoid trilobite: Drevermannia richteri. In addition, the partial ontogenetic development of Drevermannia antecurvata sp. nov. and undetermined species, Drevermannia sp. 1, are described. The proetoid anaprotaspides, associated with D. richteri, illustrate that a marked increase in larval size occurred prior to the terminal Devonian extinction event. Considering the homogeneity of larval size in older Devonian proetoids, it is interpreted as evidence that the developmental strategy of these trilobites was significantly modified. Though largely speculative, two alternative hypotheses are proposed to explain this modification. Finally, all three ontogenetic sequences show that ocular structures never develop externally in Drevermannia, but also illustrate that the development of optical nerves is not completely lost in this group. This suggests that blindness in the Drevermannia lineage followed a centripetal mode of eye reduction.

An Inca trilobite from Chile

by Rudy Lerosey-Aubril

Lerosey-Aubril, R. (2004): An Inca trilobite from Chile. Trilobite papers 16, 17-19.

Post-protaspid ontogeny of the blind cyrtosymboline Helioproetus (Trilobita) from the late Famennian of Thuringia, Germany.

by Rudy Lerosey-Aubril

LEROSEY-AUBRIL R. & FEIST R. 2005. Post-protaspid ontogeny of the blind cyrtosymboline Helioproetus (Trilobita) from the late Famennian of Thuringia, Germany. Senckenbergiana Lethaea, 85(1): 119-130.

The almost complete post-protaspid ontogenetic sequence and the hitherto unknown hypostome of a Late Devonian blind... more The almost complete post-protaspid ontogenetic sequence and the hitherto unknown hypostome of a Late Devonian blind proetid,Helioproetus costifusus, are described. The silicified meraspid remains were recovered from the lower part of the Upper Clymenien-Schichten of late Famennian (Dasbergian) age from Breternitz near Saalfeld, Thuringia. The course of the facial suture inH. costifusus is in early ontogenetic stages similar to that of adults of the youngerH. carintiacus, present in the upper part of the same section. This observation suggests an ancestor-descendent relationship between the two species, implying processes of heterochrony. The smallest cranidia of H. costifusus also exhibit a particular overall morphology and a remnant of a straight palpebral suture indicating that this species may have had a sighted cyrtosymboline ancestor. The Early Carboniferous Pedinocoryphe is considered to have evolved in a convergent way from a common rootstock.

End-Devonian extinction and a bottleneck in the early evolution of modern jawed vertebrates

by Lauren Sallan

Persistent predator–prey dynamics revealed by mass extinction

by Lauren Sallan

A microanatomical and histological study of the postcranial dermal skeleton in the Devonian sarcopterygian Eusthenopteron foordi

by Michel Laurin

Scanty evidence and changing opinions about evolving appendages

by Michel Laurin

Microanatomy of the dermal skeleton of Balticaspis latvica (Osteostraci, Middle Devonian)

by Michel Laurin

A microanatomical and histological study of the fin long bones of the Devonian sarcopterygian Eusthenopteron foordi

by Michel Laurin