Revision of the Early and Middle Cambrian Acrotretids (Brachiopoda,Linguliformea) from the Siberian Platform

Paleontological Journal - This paper continues our revision of Yu.L. Pelman’s collection of the linguliformean brachiopods and of our own material from the Early–Middle Cambrian of the...     

Revision of the Early-Middle Cambrian Lingulida (Brachiopoda) from the Siberian Platform

Based on Yu.L. Pelman’s lingulid collection and our own material, the Early-Middle Cambrian genus Eoobolus, which was widespread on the Siberian Platform, is revised. The Siberian members of this genus have previously been assigned to Lingulella. Two out of these six members are recognized as valid species: Eoobolus siniellus (Pelman) and E. variabilis (Pelman). Lingulella acuta Pelman and L. linguata Pelman are considered here to be junior synonyms of E. priscus (Poulsen, 1932). The valid species are redescribed and their stratigraphic and geographic ranges are given. A new species, E. pelmani sp. nov., is described. New data on the Eoobolus microornamentation and shell structure are provided.     

First African oryctocephalid trilobites from the Lower–Middle Cambrian boundary interval

Oryctocephalid trilobites from Lower Middle Cambrian strata of the eastern Anti-Atlas, Morocco, are the first described Oryctocephalidae known from Africa. They represent the new genus and species Shergoldiella vincenti. However, a similar species was earlier described as Tonkinella sequei Liñán et Gozalo, 1999, from coeval lower Middle Cambrian strata of the Iberian Chains, northern Spain. This Iberian species is imperfectly preserved and assigned herein to Shergoldiella with reservations. If this assignment is correct, it would reinforce earlier suggested correlations between Morocco and Spain. Nevertheless, Shergoldiella suggests a morphocline from a typical oryctocephalid-type morphology towards the Tonkinella-type morphology. Close similarity with Ovatoryctocara ovata suggests a similar stratigraphic position in accordance with earlier suggested intercontinental correlations.     

Revision of the superfamily Acrotheloidea (Brachiopoda,class Linguliformea,order Lingulida) from the Lower and Middle Cambrian of the Siberian Platform

This paper continues our revision of Yu.L. Pelman’s collection of the superfamily Acrotheloidea (phosphatic brachiopods) and of our own material from the Early–Middle Cambrian of the Siberian Platform. The following representatives of the superfamily Acrotheloidea (order Lingulida, class Linguliformea) are restudied and revised based on new techniques: the genus Botsfordia (family Botsfordiidae Schindewolf, 1955) and the genera Acrothele, Eothele, and Orbithele (family Acrothelidae), which are widespread on the Siberian Platform. Only one out of the three Acrothele species described by Pelman is recognized as a valid species, and one new species of this genus that comprises some part of the brachiopods that Pelman figured and placed in another taxon is described. All these species are described using data on shell microsculpture and microstructure. In addition, the genera Eothele and Orbithele are described for the first time from the Siberian Platform.     

New Cambrian lobopods and chaetognaths of the Siberian Platform

The association of isolated remains of lobopods with a netlike structure, including plates of Microdictyon rozanovi sp. nov. and sclerites with spinelike process of Onychomicrodictyon spiniferum gen. et sp. nov., as well as saberlike sclerites of Protohertzina yudomica sp. nov. interpreted as grasping spines of chaetognaths, is described from the middle part of the Inikan Formation of the Toyonian Stage of the Lower Cambrian (Lermontovia dzevanovskii Zone). The diagnoses and species composition of the genera Microdictyon and Protohertzina are refined.     

Lower-Middle Cambrian boundary in open shelf facies of the Siberian Platform

In the Early and Middle Cambrian (of traditional usage), three broad facies belts were developed over the Siberian Platform. The lithofacies belts comprise evaporitic-carbonate, reef-shoal, and open-marine environments.Trilobites assemblages are most diverse in the open-marine lithofacies (Judoma-Olenek facies), represented especially by the Kuonamka Formation, in the eastern part of the platform. Species, genera and families of trilobites gradually increased through the Middle-Cambrian boundary interval in the Kuonamka Formation. Protolenidae dominated in the time represented by the Lermontovia Zone. In strata assigned to the Anabaraspis Zone, the protolenids disappear, the paradoxidids appear, and the diversity of dorypygids increases. The number of trilobite families increases in the Oryctocara and Kounamkites zones.Well represented in the Kuonamka formation of the eastern Siberian Platform are three levels of trilobites that have potential for global correlation. They are the Oryctocephalus reticulatus (=O. indicus latus), Oryctocephalus indicus, and Ovatoryctocara granulatus levels. The Lower-Middle Cambrian boundary in the South China correlates to the lower part of the Kounamkites Zone of the Siberian Platform.     

Kulm trilobites (Lower Carboniferous) from S-China

Some trilobite remains are described from the Lower Carboniferous/Mississippian (Tournaisian/Viséan boundary) of S-China, representing two species:Liobole (Liobole) devuysti n. sp. andLiobole (Sulcubole) xiangzhouensis n. sp.Liobole is a typical member of the central European Kulm Facies and index fossil for the Erdbachian. For the first time, twoLiobole species are recorded from outside of Europe. They demonstrate that a passage existed between Europe and East Asia across the Palaeotethys through which Kulm trilobites have occupied new geographical regions.      

Middle Cambrian cystoid (sensu lato) stem columnals from Bornholm, Denmark

A rich material of echinoderm fragments from two Middle Cambrian stratigraphical levels on Bornholm are preserved due to phosphatization of the original calcitic stereom. Preservation of echinoderms in this way - not previously recorded from the Middle Cambrian - permits detailed analysis of the three-dimensional stereom structure. Identifiable are fragments of stylophorans and eocrinoids. Stem columnals, most likely from eocrinoids, show a wide and advanced morphological variation indicating articulation similar to that of crinoids. The material from the Exsulans Limestone/Kalby marl ( Ptychagnostus gibbus Zone) represents stem-bearing cystoids older than Akadocrinus from Bohemia. The Andrarum Limestone ( Sole-nopleura brachymetopa Zone) contains echinoderm fragments from a higher stratigraphical level, a level correlatable with that from which the oldest North American stem–bearing cystoid, Eustypocystis , has been recorded.     

Predation by early Cambrian trilobites on infaunal worms - evidence from the Swedish Mickwitzia Sandstone

Evidence of early Cambrian predation is found in trace fossils from the Mickwitzia Sandstone of VastergÖtland, Sweden. The arthropod burrow Rusophycw dispar was dug down to spreite burrows in such a manner that mere coincidence of place is unlikely. The predator is identified as an olenellacean trilobite, mainly through the presence of a cephalic impression. The prey, a worm that may have been a priapulid, was localized visually or chemically at the spreite-burrows apertures. The predator lacked legs specialized for seizing prey, as indicated by the parallel, but laterally displaced position of the Rusophycus above the spreite burrow. In this stance prey could be gripped by flexing the supposedly spinose legs of one side around it. When a spreite burrow of limited horizontal extension was encountered, parallel orientation was obtained prior to digging, probably through chemical sensing, whereas parallel orientation to an extended burrow required a number of diggings. These traces are important evidence of early Cambrian predation and of the predatorial capability of trilobites. □ Lower Cambrian, Sweden predation, trilobites, priapulids , Rusophycus.     

The biostratigraphic and palaeoenvironmental significance of Lower Cambrian (Botomian) trilobites from the Ak-Kaya section of the Altai Mountains (southern Siberia,Russia)

The presence of one of the oldest records of polycystine Radiolaria in the Lower Cambrian sedimentary sequence of the Ak-Kaya section (Gorny Altai) requires a biostratigraphic dating. The trilobites found recently a few tens of meters below the radiolarian-bearing level belong to Calodiscus resimus Repina, Serrodiscus fossuliferus Repina and Alacephalus aff. contortus Repina; they suggest that this part of the Shashkunar Formation can be correlated with the lower part of the Botomian stage. The absence of eyes in the two former species suggests a mode of life buried in the fine pelagic sediments. Indications of the presence of a strongly developed musculature on the third species point to a palaeoenvironment characterized by a relatively high hydrodynamic regime.     

A new chondrophorine (Cnidaria,Hydrozoa) from the cadiz formation (Middle Cambrian) of California

We describe a new species of chondrophorine hydrozoan,Palaelophacmaea valentinei sp. nov., from the early Middle Cambrian part of the Cadiz Formation of the Marble Mountains of southeastern California. This find extends the stratigraphic range of this genus into the early Middle Cambrian and its geographic range into the western United States. We review various chondrophorine-like fossils and present a tentative chondrophorine phylogeny in light of this find.     

Exceptionally preserved jellyfishes from the Middle Cambrian

Cnidarians represent an early diverging animal group and thus insight into their origin and diversification is key to understanding metazoan evolution. Further, cnidarian jellyfish comprise an important component of modern marine planktonic ecosystems. Here we report on exceptionally preserved cnidarian jellyfish fossils from the Middle Cambrian (approximately 505 million years old) Marjum Formation of Utah. These are the first described Cambrian jellyfish fossils to display exquisite preservation of soft part anatomy including detailed features of structures interpreted as trailing tentacles and subumbrellar and exumbrellar surfaces. If the interpretation of these preserved characters is correct, their presence is diagnostic of modern jellyfish taxa. These new discoveries may provide insight into the scope of cnidarian diversity shortly after the Cambrian radiation, and would reinforce the notion that important taxonomic components of the modern planktonic realm were in place by the Cambrian period.     

A Middle Cambrian edrioasteroid from the Murero biota (NE Spain) with Australian affinities

A Middle Cambrian edrioasteroid belonging to the genus Cambraster is described from the Middle Cambrian Murero biota (Cadenas Ibéricas, NE Spain). Up to now, this genus was known only from Australia and France. This represents the first record of the class Edrioasteroidea in the Cambrian of Spain. Moreover, preliminary results on the diversity and biostratigraphic position of Cincta, Eocrinoidea and Edrioasteroidea from this area are reported.     

New Middle Permian foraminifers (Chitralinidae) from the Karakaya Complex,in northwestern Turkey

One new foraminiferal genus, Rectoformata gen. nov., with two new species, has been described from a Permian limestone block in the Karakaya Complex in the South of the Balya district (Balikesir, northwestern Turkey). The type species of Rectoformata, Rectoformata tekini sp. nov., is characterized by a quadrangular transverse section having a calcareous microgranular wall with fine alveolar structures, whereas Rectoformata acari sp. nov. is recognized by a pentagonal transverse section having a calcareous microgranular wall with fine alveolar structures. The age of the described taxa is assigned as Midian ( = Capitanian) based on the association with small foraminifers and fusulinids. These new taxa are included in the family Chitralinidae, which is emended herein.