Lower Emsian Research Articles

Lower Emsian (Lower Devonian) conodonts from southwestern and central Guangxi, South China: Implications for palaeogeographic reconstructions

Conodont biostratigraphy is investigated in the Poyuan, Shangkou, and Menggong sections in Guangxi, and the Lower Emsian (Lower Devonian) excavatus and nothoperbonus zones are partly recognized. Combining the Lower Devonian conodont framework and lithological successions to date, the process of the Early Devonian northeastward stepwise transgression in South China is more elaborated in detail herein. It is proved that the differentiation of the “Xiangzhou Facies” and the “Nandan Facies” in South China took place in the nothoperbonus Zone. A series of high‐resolution Early Devonian palaeogeographic maps of South China is illustrated in this study.

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.

The oldest ammonoids of Morocco (Tafilalt, lower Emsian)

During a fieldtrip of the 10th International Cephalopod Symposium to the Tafilalt (SE Morocco), a fauna with the so far oldest ammonoid of the region was discovered at the top of the basal Emsian Deiroceras Limestone of Jebel Mech Irdane. The new material confirms the record of a single, poorly preserved specimen of the same age from Ras El Kebbar in the northwestern Tafilalt. All specimens are assigned within the Chebbitinae n. subfam. (Mimosphinctidae) to Praechebbites debaetsi n. gen. n. sp., which differs from the slightly younger Chebbites reisdorfi mostly in the lack of a dorsal lobe and dorsal imprint zone. In the conodont succession, the new species and genus falls in the top of the Eolinguipolygnathus excacatus M114 Zone, which has been proposed to define in future the base of the Emsian. Since the new taxon is morphologically already advanced, it is likely that even older ammonoids with loosely coiled conchs will be discovered in the future. A block from a Lower Carboniferous olistostrome of the adjacent Tinerhir region contained the gyroconic Ivoites n. sp. only. The global comparison of oldest ammonoid faunas shows the rarity of assemblages assigned to Lower Devonian (LD) III-B, often dated by conodonts and dacryoconarids. These faunas display a high level of endemism, which suggests that ammonoid origin and early evolution took place in regional populations with a restricted dispersal of genera and species.

Revision of the Early Devonian tabulate coral Pleurodictyum bifidum from New South Wales

Plusquellec, Y. & Wright, A.J., October 2017. Revision of the Early Devonian tabulate coral Pleurodictyum bifidum from New South Wales. Alcheringa 41, xxx–xxx. ISSN 0311-5518.The tabulate coral Pleurodictyum bifidum Jones, 1944, from the Early Devonian (Pragian or lower Emsian) Garra Formation of central New South Wales, Australia is revised on the basis of the holotype and three other specimens. It is selected as the type species of the new monotypic genus Bifidomeria (Family Roemeriidae), which differs from Roemeria in its strictly cerioid corallum, its bifid septal spines and aspects of its microstructure. Study of the detailed microstructure of two other tabulate corals from the Devonian of New South Wales has led to the following revised generic assignments: Michelinia progenitor Chapman, 1921, previously assigned to Roemeripora, is assigned to Roemeria, and Holacanthopora clarkei Wright & Flory, 1980 is assigned to Michelinia.Yves Plusquellec [yves.plusquellec@univ-brest.fr], Université de Bretagne Occidentale, CNRS-UMR 6538 ‘Domaines océaniques’, Laboratoire de Paléontologie, UFR Sciences et Techniques, 6 avenue Le Gorgeu, CS 98837, F-29283 Brest, France; Anthony Wright [tony.wright@optusnet.com.au], GeoQuEST Research Centre, School of Earth & Environmental Sciences, University of Wollongong, Wollongong NSW 2522, Australia.

First record of eurypterids (Chelicerata, Eurypterida) from the Lower Devonian (Lower Emsian) Hunsrück Slate (SW Germany)

For the first time, fossils of unquestionable eurypterid origin are documented from the renowned Lower Devonian Hunsruck Slate Lagerstatte in southwestern Germany. The gnathobase of a coxal plate and a body segment can be attributed to pterygotid eurypterids, probably to Jaekelopterus rhenaniae. These body parts from the Hunsruck Slate once more confirm the extraordinary large size that could be attained by this Rhenish eurypterid. Based on the usual occurrence in marine–terrestrial transitional facies elsewhere in the Rhenish Devonian, rareness in the Hunsruck Slate, and poor preservation, the Hunsruck Slate pterygotid remains are most probably allochthonous, and eurypterids are considered nongenuine elements of the ‘Hunsruck Slate biota.

Pragian and lower Emsian (Lower Devonian) conodonts from Liujing, Guangxi, South China

LU, J.-F., QIE, W.-Q. & CHEN, X.-Q., July 2016. Pragian and lower Emsian (Lower Devonian) conodonts from Liujing, Guangxi, South China. Alcheringa 40, xxx–xxx. ISSN 0311-5518.Lower Devonian (Pragian and Emsian) conodonts are described from the Liujing section in Guangxi, South China, highlighting the phylogeny of early polygnathids and establishing the basis for faunal correlations with deposits throughout the world. Records of Eognathodus kuangi sp. nov. and E. nagaolingensis Xiong increase the biodiversity of the Pragian eognathodids in South China and represent intermediate stages and probably the latest eognathodids in the evolutionary succession from Eognathodus to Polygnathus. During this evolutionary succession, the degeneration of the sulcus (or the flattening of the upper platform surface) is the most important morphological change, especially in the eognathodid lineage. Polygnathus trilinearis, P. pireneae and P. sokolovi are recognized together for the first time in South China. The contemporaneous occurrences of the kitabiformis and sokoloviformis morphs of P. pireneae with P. sokolovi and their respective similarities to P. kitabicus and P. sokolovi suggest that the latter two species are phylogenetically linked with P. pireneae. Evidence from the Liujing section also favours Polygnathus probably having evolved from Eognathodus in a tropical or subtropical area.Jian-feng Lu* [lujfivan@sina.cn] and Xiu-qin Chen [xqchen@nigpas.ac.cn], Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, 39 East Beijing Road, Nanjing 210008, PR China; Wen-Kun Qie [wkqie@nigpas.ac.cn], Key Laboratory of Economic Stratigraphy and Palaeogeography, Nanjing Institute of Geology and Palaeontology, 39 East Beijing Road, Nanjing 210008, PR China. *Also affiliated with University of Chinese Academy of Sciences, Beijing 100049, PR China.

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).

The first record of Early Devonian ammonoids from Belgium and their stratigraphic significance

The first ammonoids from the Lower Emsian (Devonian) of Belgium are described. They belong to the Anetoceratinae, which show the most plesiomorphic characters of all ammonoids. This is the second report of Early Emsian ammonoids within the Rhenish facies of the Rhenish Slate Mountains (Belgium, Germany), in this case from the Belgian part of the Eifel (Burg Reuland). It highlights the possible importance of ammonoids for the correlation of the Emsian in its traditional German sense and the Emsian in the global sense as delimited by the GSSPs. Newly collected, age-significant brachiopods of the genera Arduspirifer and Euryspirifer and other previously reported fossils indicate a middle or late Early Emsian (Singhofen or Vallendar) age (in German sense) for this locality. We extend the range of Ivoites schindewolfi outside of the Hunsruck Basin and further corroborate an age younger than Ulmen for parts of the Hunsruck Slate.

Reassessing Devonotarbus, a phalangiotarbid arachnid from the Lower Devonian (Siegenian and Emsian) of the Rheinisches Schiefergebirge (SW Germany)

Seven further specimens of the hitherto only known Devonian phalangiotarbid Devonotarbus Poschmann, Anderson and Dunlop, 2005 are described. Thus, the genus is recorded from four different localities of Siegenian (Hombach and Burglahr) and Lower Emsian (Willwerath and Alken) age, respectively, but the specific identity of Siegenian and Emsian specimens remains unproven. The new material suggests that this Devonian phalangiotarbid possessed more than six eye lenses, tergites five and six fused into a diplotergite, and an almost terminally situated anal operculum. It thus notably deviates morphologically from its younger Permocarboniferous relatives, and a new family, Devonotarbidae nov. fam., is proposed to accommodate Devonotarbus.

Trigonotarbid arachnids from the Lower Devonian (Lower Emsian) of Alken an der Mosel (Rhineland-Palatinate, SW Germany)

New material of the trigonotarbids Alkenia and Archaeomartus from the Lower Devonian type locality Alken an der Mosel/Germany is described. Stormer’s original description of Alkenia is essentially confirmed and supplemented. The genus is placed in Aphantomartidae. In contrast to earlier accounts, we show that Archaeomartus has an anterior diplotergite and a longitudinally three-divided posteriormost (ninth) tergite. The new family Archaeomartidae is proposed. Whether a marginal row of larger tubercles on the opisthosoma can be recognized is strongly influenced by the taphonomic history of the fossil, and sexual dimorphism may also be involved. Thus, we propose that Archaeomartus levis and A. tuberculatus, which can be discriminated solely by the presence or absence of this feature, are synonyms. Furthermore, morphological similarity suggests the possibility that archaeomartids, with their opisthosomal tergites divided into three plates, gave rise to the later (Carboniferous) anthracomartids, specifically through the division of the lateral plates and the ninth tergite. Finally, our reassessment of Archaeomartus shows that ‘A.’ roessleri Dunlop and Brauckmann, 2006 can no longer be adequately maintained in this genus. This younger species from the early Upper Carboniferous of Hagen-Vorhalle, Germany, is reassigned to Namurotarbus n. gen. as Namurotarbus roessleri n. comb.

Annelids from the Lower Devonian Hunsrück Slate (Lower Emsian, Rhenish Massif, Germany)

Abstract: Four new genera and species of annelid, Hunsrueckochaeta hohensteini, Ewaldips feyi, Crocancistrius lutzi and Scopyrites magnus, are described from the Hunsruck Slate (Lower Emsian) of Germany, as well as new material of Bundenbachochaeta eschenbachensis Bartels and Blind, 1995. The specimens preserve details of the appendages and other aspects of the morphology as a result of pyritization. A phylogenetic analysis using the morphological data matrix of Rouse and Fauchald places four of the five genera basal to the Aciculata; the fifth Ewaldips falls within the Scolecida. The diversity of annelids represented in the Hunsruck Slate is similar to that in the other major Palaeozoic Konservat-Lagerstatten that yield them, including the Cambrian Burgess Shale and the Late Carboniferous Mazon Creek biota.

A pyritized lepidocoleid machaeridian (Annelida) from the Lower Devonian Hunsrück Slate, Germany

A machaeridian, Lepidocoleus hohensteini sp. nov., is described from the Hunsrück Slate (Lower Emsian) of Germany. The available material includes a unique example preserving evidence of the soft tissues, only the second machaeridian specimen to do so and the first lepidocoleid. This specimen shows that the plates are attached to alternate segments in the trunk. The morphology is consistent with an annelid affinity of the Lepidocoleidae and confirms the unity of the Machaeridia. This discovery adds an important group to the known diversity of this famous late Palaeozoic marine Konservat-Lagerstätte.

GNATHOSTOME MICROREMAINS FROM THE LOWER DEVONIAN JAWF FORMATION, SAUDI ARABIA

Calcareous horizons in the Qasr and Hammamiyat members (Lower Devonian, ?Pragian and lower Emsian) of the Jawf Formation, northwestern Saudi Arabia, yielded a rich assemblage of microremains from acanthodian, placoderm, chondrichthyan, and sarcopterygian vertebrates. The most abundant elements are scales from acanthodians Nostolepis spp., Milesacanthus ancestralis n. sp., Canadalepis? sp., and Gomphonchus? fromensis, scales and dermal bone fragments from acanthothoracid and ?rhenanid placoderms, and teeth from onychodontids. Rarer occurrences include ?chondrichthyan scales of several different morphotypes, and petalichthid and ?ptyctodontid placoderm elements. The Qasr Member assemblage shows a close resemblance to slightly older faunas from the Lochkovian of Brittany and Spain. The Hammamiyat Member microvertebrate fauna shows closest affinity with that of the stratigraphically lower Qasr Member, with similarities also to coeval faunas from southeastern Australia, late Emsian/Eifelian faunas from west-central Europe, and the Givetian Aztec Siltstone fauna from Antarctica.

Biostratigraphical significance of the Devonian Sinoleperditiini (Ostracoda)

The Tribe Sinoleperditiini (Ostracoda), which is mainly distributed in South China and its adjacent areas, is a single natural group of the Leperditiidae, characterized by the development of a trailing chevron muscle scar. This tribe is known only from the Devonian and ranges through most of the Devonian. The evolutionary trends within the Sinoleperditiini have been well documented and are exemplified by changes in the trailing chevron muscle scar. The main evolutionary change is a tendency of the trailing chevron muscle scar to extend ventrally through time, as demonstrated by the increasing ratio (th/ah) of the vertical height of the trailing chevron muscle scar (th) to that of the adductor muscle scar (ah). The recent discovery of a sinoleperditiine assemblage (th/ah values available) in the middle-upper Lower Emsian Shanglun Formation allows to propose a sinoleperditiine biostratigraphical sequence for the Devonian. This sequence contains 11 assemblages (th/ah value available for each assemblage), which cover all the 7 Devonian stages and some substages. This sequence is particularly useful for correlating and dating Devonian rocks in the littoral clastic, lagoonal and restricted or semirestricted carbonate platform facies where these ostracodes are most abundant and other fossils are uncommon.

A new specimen ofWeinbergina opitzi (Chelicerata: Xiphosura) from the Lower Devonian Hunsriick Slate, Germany

A new specimen of the synziphosurine arthropodWeinbergina opitzi is described from the Lower Devonian (Lower Emsian) Hunsruck Slate of Germany (Rhenish Slate Mountains). It is the smallest and only the fifth specimen of this taxon to be described and is preserved in ventral aspect with exceptional preservation of prosomal and opisthosomal appendages. This specimen confirms the presence of a seventh appendage, similar in morphology to the preceding prosomal appendages, associated with opisthosomal segment one. In addition, at least three opisthosomal plates fringed with teeth are confirmed. Correlation of prosomal appendage podomeres betweenWeinbergina and selected chelicerate taxa shows that appendage structure is most similar to eurypterid appendages III–IV and Araneae appendages III–VI. This is in contrast to modern horseshoe crabs which have fewer podomeres in appendages II–V due to an undifferentiated tibiotarsus.

Ostracods of Thuringian provenance from the Devonian of Morocco (Lower Emsian - middle Givetian; south-western Anti-Atlas)

Ostracods of Thuringian provenance from the Devonian of Morocco (Lower Emsian - middle Givetian; south-western Anti-Atlas)

Bracteophyton variatum gen. et sp. nov., an Early Devonian Plant from the Xujiachong Formation of Yunnan, China

Bracteophyton variatum gen. et sp. nov. is described from the Lower Devonian (upper Pragian–lower Emsian) Xujiachong Formation, Qujing District of eastern Yunnan, China. The smooth axes are mainly isotomous. They terminate in short and compact strobili consisting of lateral fertile units arranged helically. Each fertile unit comprises one or two bracts and an elongate‐ovate adaxial sporangium. The sporangium seems to possess a distal dehiscence around the convex margin. Bracteophyton variatum differs from bract or sporophyll‐bearing plants such as Stachyophyton, Adoketophyton, and the Barinophytales mainly in the shape and variable number of bracts in a fertile unit. In the absence of vegetative microphylls, it is morphologically far less related to the lycopods. Resembling the sporangial arrangement in spikes of some zosterophylls, the spirally inserted fertile units forming terminal compact strobili in B. variatum demonstrate the developmental changes in the apical meristem. Until more is known, this ne...

Tracheid Ultrastructure of Hsüa deflexa from the Lower Devonian Xujiachong Formation of Yunnan, China

We describe the tracheid ultrastructure of Hsua deflexa from the Lower Devonian (upper Pragian–lower Emsian) Xujiachong Formation, Qujing District, Yunnan Province, China. Scanning electron microscopy study of fusainized and permineralized tracheids shows that they are of G‐type, bearing many irregularly distributed perforations. The cell wall consists of a decay‐resistant inner part lining the cell lumen and a nonresistant outer part. The resistant inner part, i.e., the assumed heavily lignified secondary wall, is continuous over the poorly lignified outer part that comprises the primary wall and discontinuous secondary wall. It forms the annular thickening over the discontinuous secondary wall. The heavily lignified secondary wall may be divided into three layers. Minute perforations occur on the entire heavily lignified secondary wall, i.e., between and on the thickenings. Concerning the distribution, density, and diameter of perforations, G‐type tracheids of H. deflexa share some characters of S‐type ...

Devonohexapodus bocksbergensis, a new marine hexapod from the Lower Devonian Hunsrück Slates, and the origin of Atelocerata and Hexapoda

Abstract We describe a new arthropod (approximately 75 mm long) from the Lower Devonian (Lower Emsian) Hunsrück Slates near Bundenbach, western Germany. The specimen is from an isolated piece of rock found on the quarry dump, precluding precise resolution of stratigraphic age. The Hunsrück Slates are marine sediments with a rich fauna of exclusively marine taxa, suggesting that our fossil was also marine. The animal has a small head with large compound eyes and long, filiform, myocerate antennae. Its trunk is divided distinctly into a thorax with three segments and three pairs of slender legs, and a post-thoracic domain composed of 35-40 limb-bearing segments of which the anteriormost are paired, stout, and ventrally-oriented leglets; the three ultimate limb-bearing segments bear longer, posteriorly-oriented and apparently specialised appendages. The overall appearance of the new form is reminiscent of Archaeognatha or Odonata. It is interpreted as a representative of the Hexapoda because of the possession of a three-segmented thorax and three pairs of legs that are clearly distinct from the posterior set. The large number of leg-bearing post-thoracic segments discriminates it from the Insecta, which possess 11 “abdominal” segments maximally, originally also leg-bearing. The formal systematic classification of the organism is: (Hexapoda ( Devonohexapodus bocksbergensis + Insecta (“entognaths” + Ectognatha))). The morphology of the fossil and its environment suggest that the hexapody of hexapods did not evolve as an adaptation to terrestrial locomotion, but was already developed in the marine habitat. No terrestrial arthropods have changed their original tagmosis for biomechanical reasons, for example, no “myriapods” have reduced their leg numbers or modified their trunk to evolve a thorax and abdomen similar to insects. Walking exclusively on uniramous prosomal legs in the Chelicerata also occurred well before terrestrialization of this other euarthropodan group. It is not unlikely that the last common ancestor of the Hexapoda was large and that the small size of extant “entognaths” evolved due to reduction in their stem lineage. Being marine, the new fossil also has considerable impact on hypotheses about the early evolution of Atelocerata (“myriapods” + Hexapoda). For example, if their last common ancestor was aquatic, terrestrialization took place at least twice and tracheal breathing probably evolved independently in both taxa after terrestrialization.

New evidence for the synonymy ofDilophaspis andNahecaris (Phyllocarida; Lower Devonian; Rhenish Massif)

Recently discovered phyllocarids from the early Upper Emsian Wiltz Beds in the Western Eifel Mountains and in eastern Luxemburg are described asDilophaspis frankei n. sp. This species which — according to previous collections — already occurs in the late Lower Emsian, combines morphological characters of the two generaNahecarisJaekel, 1921 andDilophaspisTraquair inWalther, 1903 and, thus, shows thatNahecaris is a subjective junior synonym ofDilophaspis as already suggested byHahn (1990).Dilophaspis is now known from at least four different stratigraphical units: (1) early Emsian (Hunsruck Slate; dating afterWeddige 1996):D. stuertzi (Jaekel, 1921) andD.?balssi (Broili, 1930); (2) late Lower Emsian (Nellenkopfchen Beds, Vallendar Group):D. frankei n. sp.; (3) early Upper Emsian (Wiltz Beds):D. frankei n. sp.; (4) late Upper Emsian (“Kieselgallen-Schiefer”, Kondel Group):D. lataTraquair inWalther, 1903. This succession provesDilophaspis applicable for biostratigraphical dating.