New data on eurypterids (Eurypterida,Chelicerata) of the upper Carboniferous of the Donets Basin

Eurypterid finds are described from the Carboniferous (Kasimovian) localities Lomuvatka (Luhansk Region, Ukraine) and Kakichev (Rostov Region, Russia). These eurypterids are supposedly juveniles of Adelophthalmus carbonarius Chernyshev, 1933, the only eurypterid previously described from the Donets Basin.     

New species of the genus Adelophthalmus (Eurypterida, Chelicerata) found in the Middle Devonian of Khakassia

Two new eurypterid species, Adelophthalmus kamyshtensis sp. nov. and Adelophthalmus dubius sp. nov., are described from the Middle Devonian of Khakassia. The new species are among the earliest known members of the genus Adelophthalmus and the earliest members of this genus known outside Europe and North America.     

Note on the morphology and systematic position of Alkenopterus burglahrensis (Chelicerata: Eurypterida: Eurypterina) from the Lower Devonian of Germany

The holotype of the eurypterid Alkenopterus burglahrensis from the Lower Devonian (Siegenian) of the Westerwald area (Rhineland-Palatinate, SW Germany) is re-examined. In contrast to a previous concept, this species has flattened distal podomeres seven and eight and a movable flattened spine on the seventh podomere of the sixth prosomal appendage (podomere VI-7a). Based on the presence of such a slender paddle, A. burglahrensis has to be regarded as a basal ‘swimming eurypterid’ (Eurypterina) and is formally transferred here to the family Onychopterellidae, extending the stratigraphical range of this family into the Lower Devonian.     

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) Hunsrück 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.      

On the Emsian (Lower Devonian) arthropods of the Rhenish Slate Mountains: 5. Rare and poorly known eurypterids from Willwerath, Germany

In addition to the previously known eurypterid taxa from Willwerath, remains ofParahughmilleria hefteri, Erieopterus sp., andJaekelopterus rhenaniae are described and figured. Body parts of small pterygotids are interpreted as representing juveniles ofJ. rhenaniae. To further substantiate this interpretation an analysis of telson ontogeny in the SilurianAcutiramus macrophthalmus of New York State, another well-known pterygotid, is included. As a result, it is suggested thatPterygotus juvenis is a juvenile and thus a junior synonym ofA. macrophthalmus. The genital appendages ofJ. rhenaniae show no segmentation and consequently the family Jaekelopteridae is rejected. The palaeoenvironment of the Willwerath eurypterid association, dominated byAdelophthalmus andRhenopterus, is interpreted as a shallow brackish to freshwater/terrestrial setting in a deltaic transitional facies. In contrast,Parahughmilleria-dominated eurypterid associations from the Rhenish Slate Mountains seem to be confined to lagerstätten where a marine influence is more obvious than at Willwerath.     

On some aspects of parallel evolution in Chelicerata

A study is made of some aspects of parallel evolution in Chelicerata. Definitions are given of parallel evolution, convergence, homology and analogy. It is pointed out that the concept of parallel evolution (parallelism) is initially formed in an empirical way, and that a judgment must be based on formal criteria. Particular attention is paid to the rôle of gene regulation in parallel evolution, to the special case of convergence as a result of heterologous regulatory mechanisms, to parallel evolution in homonomous structures (and the superposition of parallelisms and divergences), and to parallelism in the evolution of characters used in higher classification.     

Anatomical reinvestigation ofArchaeopteris macilenta from the Upper Devonian (Frasnian) of South China

Archaeopteris macilenta is one of the most widespread plants in the Late Devonian.Based on fossils from the Frasnian Huangjiadeng Formation,Yichang District of Hubei Province,for the first time we study in detail the anatomy of this progymnosperm plant in South China.Ultimate axes are protostelic with three xylem sympodia and lack secondary tissue.Penultimate axes are eustelic,bearing eight sympodia and a thin band of secondary xylem.Radially symmetrical sympodia of mesarch primary xylem produce traces of appendages in a spiral arrangement.Archaeopteris macilenta and A.halliana (A.roemeriana) are dominant in the Frasnian and Famennian,respectively.Comparisons with these two species from other tectonic plates indicate consistent stelar architectures.Global spread,continuous occurrence,and identical anatomy during the Late Devonian indicate that Archaeopteris survived the Frasnian-Famennian extinction event.In this time,endemic genera and cosmopolitan taxa,including Archaeopteris,suggest the palaeogeographic isolation of South China and certain associations with other plates.     

A Gigantic Sarcopterygian (Tetrapodomorph Lobe-Finned Fish) from the Upper Devonian of Gondwana (Eden,New South Wales,Australia)

Edenopteron keithcrooki gen. et sp. nov. is described from the Famennian Worange Point Formation; the holotype is amongst the largest tristichopterids and sarcopterygians documented by semi-articulated remains from the Devonian Period. The new taxon has dentary fangs and premaxillary tusks, features assumed to be derived for large Northern Hemisphere tristichopterids (Eusthenodon, Hyneria, Langlieria). It resembles Eusthenodon in ornament, but is distinguished by longer proportions of the parietal compared to the post-parietal shield, and numerous differences in shape and proportions of other bones. Several characters (accessory vomers in the palate, submandibulars overlapping ventral jaw margin, scales ornamented with widely-spaced deep grooves) are recorded only in tristichopterids from East Gondwana (Australia-Antarctica). On this evidence Edenopteron gen. nov. is placed in an endemic Gondwanan subfamily Mandageriinae within the Tristichopteridae; it differs from the nominal genotype Mandageria in its larger size, less pointed skull, shape of the orbits and other skull characters. The hypothesis that tristichopterids evolved in Laurussia and later dispersed into Gondwana, and a derived subgroup of large Late Devonian genera dispersed from Gondwana, is inconsistent with the evidence of the new taxon. Using oldest fossil and most primitive clade criteria the most recent phylogeny resolves South China and Gondwana as areas of origin for all tetrapodomorphs. The immediate outgroup to tristichopterids remains unresolved – either Spodichthys from Greenland as recently proposed, or Marsdenichthys from Gondwana, earlier suggested to be the sister group to all tristichopterids. Both taxa combine two characters that do not co-occur in other tetrapodomorphs (extratemporal bone in the skull; non-cosmoid round scales with an internal boss). Recently both ‘primitive’ and ‘derived’ tristichopterids have been discovered in the late Middle Devonian of both hemispheres, implying extensive ghost lineages within the group. Resolving their phylogeny and biogeography will depend on a comprehensive new phylogenetic analysis.     

On the taxonomic status of some Glyptodontidae (Mammalia,Xenarthra, Cingulata) from the Pleistocene of South America

The anatomical and taxonomic knowledge of some groups of Glyptodontidae (Mammalia, Cingulata) is still very poor. In addition, a strict typological/morphological taxonomic criterion was used in recognizing many taxa, especially during the second half of the 19th century and the first of the 20th century. This particular situation resulted in a clear overestimation diversity, mainly with respect to the South American glyptodonts. In this scenario, this paper analyzes the taxonomic status of some Glyptodontinae through a precise comparative study with well characterized taxa. The main results show that the genera Pseudothoracophorus Castellanos (P. depressus) and Chlamydotherium Lund, one species of the genus “Boreostracon” Simpson (B. corondanus), and one species of the genus Glyptodon Owen (G. falkneri), actually represents juvenile specimens referable to Glyptodon Owen; the genus Neothoracophorus Ameghino (N. elevatus) could be related either to Glyptodon Owen or Glyptotherium Osborn. Another species, Heteroglyptodon genuarioi, presents an almost identical morphology compared with the recognized species of Glyptodon (e.g. G. munizi and G. reticulatus). In this sense, the diagnostic characters described for Glyptodon perforatus Ameghino, a taxon with biostratigraphic relevance since it is characteristic of the Lujanian Age/Stage (late Pleistocene-early Holocene), are also present in other species of Glyptodon, especially G. reticulatus and G. clavipes, very frequent taxa in southern South America.     

New Middle Devonian conodont data from the Dong Van area,NE Vietnam (South China Terrane)

Middle Devonian conodonts from the Si Phai section in NE Vietnam are described. The section ranges from the Middle Devonian ensensis to timorensis conodont zones to the Late Devonian rhomboidea conodont Zone. A rich overall assemblage is described, including 27 taxa of species or subspecies rank and 11 taxa described in an open nomenclature. Among the dominant Polygnathus forms, four new taxa are described: Polygnathus linguiformis saharicus subsp. nov., Polygnathus linguiformis vietnamicus subsp. nov., Polygnathus rhenanus siphai subsp. nov., and Polygnathus xylus bacbo subsp. nov. Conodont assemblages are attributed to polygnathid, polygnathid-klapperinid, and klapperinid conodont biofacies representing hemipelagic to pelagic environments. The klapperinid biofacies, unreported in the previous literature, are here attributed to offshore areas of the external shelf. The taxonomic compositions of the studied conodont assemblages, as well as their CAI characteristics (CAI 4–5), suggest a palaeogeographic affinity of the studied strata to the Chinese Devonian Guangxi Basin, and the South China Terrane in general. Furthermore, the conodont biofacies and the palaeogeographic distribution of the fauna are discussed.     

First Fossil Xiphosuran (Chelicerata,Xiphosura) Egg Clutch from the Carboniferous of Khakassia

A new formal genus with a new species Xiphosuroides khakassicus gen. et sp. nov. is established for a clutch of nine eggs containing embryos, presumably xiphosurans (Chelicerata, Xiphosura, Bellinurina). This unique specimen comes from the Lower–Middle Carboniferous Sarskaya Formation of Khakassia (Izykhskie Kopi locality). If the hypothesis of the xiphosuran nature of these eggs is correct, the specimen described in this paper is the first certain record of fossil xiphosuran eggs and embryos.     

Conodont biostratigraphy of the Yujiang Formation (Emsian,Lower Devonian) at Shizhou,Guangxi, South China

We study conodonts from the upper part of the Shizhou Member of the Yujiang Formation in Liujing area for the first time. Relatively abundant conodonts were collected from six sampling levels located between the uppermost part of the Shizhou Member to the lowermost part of the Daliancun Member at the Shizhou section, Liujing, Guangxi. The material includes Polygnathus excavatus excavatus Carls and Gandl, P. excavatus ssp. 114 Carls and Valenzuela-Ríos, P. nothoperbonus Mawson, P. perbonus (Philip) as well as ?Ozarkodina? midundenta (Wang and Ziegler) and ?O.? prolata Mawson. The lowest record of P. nothoperbonus is documented 0.35 m below the boundary between the Shizhou and Daliancun members. Correlation of conodont biostratigraphy between the Shizhou and Liujing sections indicates that the upper part of the Shizhou Member (partially) belongs to the excavatus Zone and the Daliancun Member belongs to the nothoperbonus Zone.     

On Late Jurassic and Early Cretaceous oysters (Bivalvia,Ostreidae) from northern Siberia

The morphology and taxonomic value of morphological features of Late Jurassic and Early Cretaceous oysters from northern Siberia are considered. A new species, Deltoideum exoticum Kosenko, sp. nov. is described.     

A new species of Adelophthalmus (Eurypterida) from the lower carboniferous of the Krasnoyarsk Region

A new species of Adelophthalmus, a genus recorded infrequently in the former Soviet Union, is described from the Tournaisian of the Krasnoyarsk Region.