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.     

Middle Cambrian trilobites from Borehole Nizhny Imbak 219 (northwestern Siberian Platform)

Borehole Nizhny Imbak 219 is situated in the northwestern Siberian Platform. Paleontological material comes from the clayey–limestone series at a depth of 2333.3–2314.3 m referred to the Ovatoryctocara and Kounamkites zones of the Middle Cambrian Amgan Stage and from the overlying limestone series at a depth of 2264.1–2244.0 m referred to the upper part of the Kounamkites Zone and an unnamed zone of the Amgan Stage and also to the Solenopleura patula and Dorypyge olenekensis–Corynexochus perforatus zones of the Middle Cambrian Mayan Stage. The questions of the traditional Lower–Middle Cambrian boundary and the role of Siberian sections in the construction of the International Chronostratigraphic Chart are considered. The trilobites collected are described.     

Pentamerids (Brachiopoda) from the Lower and Middle Devonian of Northeastern Asia

Pentamerids (Brachiopoda) are described from the Lower and Middle Devonian of northeastern Asia: Antirhynchonella cherkesovae sp. nov. belonging to the family Clorindidae and Devonogypa indigirica (Sidjachenko), Vadimia gen. nov. with the type species V. gonensis sp. nov. and V. naanchanensis sp. nov., and Vladimiria gen. nov. with the type species Vl. yanensis sp. nov. all belonging to the subfamily Devonogypinae.     

Note on the gut preserved in the Lower Cambrian Lingulellotreta (Lingulata, Brachiopoda) from southern China

Lingulellotreta malongensis Rong is the earliest known taxon of the family Lingulellotretidae, which is characterized by the presence of a pedicle foramen as well as an internal pedicle tube. New material from the Early Cambrian Chengjiang Lagerstätte of southern China provides improved anatomical knowledge for lingulellotretid species especially for the digestive system. Additional gut fossils exhibit distinctly the anterior portion composed of esophagus and distended stomach, situated in the alleged visceral cavity, with the recurved intestine accommodated inside a hollow pseudointerarea. The frequency of occurrence of this intestinal layout suggests that this is not just an artefact of preservation. The gross configuration of the guts and the way they are preserved in the fossils suggest that they are in situ and, therefore, we can assume that Lingulellotreta had a hollow cavity presumably subtended by the pseuodelthyrium, which was invaded and occupied by the visceral organs. Hence, these fossils demonstrate the dangers of extrapolating crown‐group soft‐tissue configuration to the stem group.     

New spiriferids (Brachiopoda) from the Lower and Middle Devonian of northeastern Russia

New spiriferids (Brachiopoda) are described from the Lower and Middle Devonian of northeastern Russia: Tatjanaspirifer iskrensis sp. nov. and T. magnificus sp. nov. (family Reticulariidae); Cyrtina inveterata Baranov, sp. nov. and Blodgettospirifer gen. nov. with type species B. lezhoevi sp. nov. (family Cyrtinidae).     

Stratigraphic and geographic distribution of acrotretids (Brachiopoda,Lingulata) in the Middle and Late Cambrian

The analysis of the taxonomic composition and distribution of acrotretids (Brachiopoda) in the Middle Cambrian and early Late Cambrian shows that, in the later half of the Cambrian, the order Acrotretida was the most abundant brachiopod order and many of its representatives were cosmopolites. The structure, mode of life, and biological features of acrotretids, along with the arrangement of continents with epicontinental seasmostly in the low latitudes, promoted the wide dispersal of this group on the Earth in the Cambrian.     

Trilobites Plicatolina lucida Lazarenko from the Upper Cambrian of the Kharaulakh Mountains (Northeastern Siberian Platform)

A collection of trilobites of the genus Plicatolina Shaw, 1951 from the upper Ogon’or Formation, Cambrian Section, Chekurovka Anticline (northeastern Siberian Platform, Kharaulakh Mountains), is studied. It is shown that all specimens of this collection belong to the same species, Plicatolina lucida Lazarenko, 1966, but represent different age stages. It is also shown that species of the genus Plicatolina (P. quadrata Pokrovskaya, 1966 and P. yakutica Pokrovskaya, 1966) described from the Upper Cambrian of the Siberian Platform are probably synonyms of P. lucida.     

Cyrtospirifer vjacheslavi, a new cyrtospiriferid species (Cyrtospiriferidae, Brachiopoda) from the Middle Frasnian of the East European Platform

A new spiriferid brachiopod species, Cyrtospirifer vjacheslavi, from the Middle Frasnian of the East European Platform is described. These spiriferide shells from the Middle Frasnian of central European Russia and Middle Timan assigned traditionally to Cyrtospirifer disjunctus for more then a century are not conspecific to British species and are here reassigned to Cyrtospirifer vjacheslavi sp. nov.     

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.     

Trilobites of the suborder Eodiscina from the Lower Cambrian of the northeastern Siberian platform (Khorbosuonka River section)

Trilobites of the suborder Eodiscina from the Lower Cambrian section of the Khorbosuonka River (Siberian Platform, Olenek Uplift) are studied. The stratigraphic distribution of these forms in the section is shown Two new species, Hebediscus sublongus sp. nov. and Korobovia khorbosuonica sp. nov., are described. This is the first occurrence of the genus Korobovia on the Siberian Platform. The new record provides additional data on morphology and expands the paleogeographic range of the genera represented by the newly described species.     

New Upper Cambrian Lingulata (Brachiopoda) from the Agyrek mountains (northeastern central Kazakhstan)

Two new genera, Repkinella and Aristotreta, and five new species from the class Lingulata (Brachiopoda) are described from the Upper Cambrian olistolith limestone enclosed in the Upper Ordovician olistostrome from the Agyrek mountains (northeastern Kazakhstan). The family Curticiidae Walcott et Schuchert is referred to the order Lingulida, not order Acrotretida, where it was previously placed.     

New Atrypids (Brachiopoda) from the Lower Devonian of Northeast Russia

New atrypids are described from the Lower Devonian of Northeast Russia: Musalitinispira, gen. nov. with type species M. dogdensis, sp. nov. (subfamily Atrypinae), Spinatrypina (Spinatrypina) krivensis, sp. nov., and Datnella, gen. nov. with type species D. datnensis (Baranov, 1995) (subfamily Spinatrypinae).     

Systematic position and composition of the superfamily Notanoplioidea Gill, 1969 (Brachiopoda, Articulata)

The systematic position of several genera of articulate brachiopods grouped around Notanoplia Gill is controversial. Notanoplia was established in 1950 within the order Chonetida; this genus and several externally similar genera, which were established later, were referred by different authors to the orders Orthida, Strophomenida, Chonetida, Atrypida, Spiriferida, or considered as incertae sedis. The morphological analysis of the shell of Notanoplia and the related genera Boucotia and Costanoplia supports the placement of these genera in a separate superfamily, Notanoplioidea, within the order Strophomenida. Other genera similar in the shell outline and shape to Notanoplia and conditionally considered as related to it probably belong to other strophomenid superfamilies or other orders.     

Revision of Echmatocrinus from the Middle Cambrian Burgess Shale of British Columbia

Echmatocrinus from the Middle Cambrian Burgess Shale of British Columbia was originally described as the earliest crinoid(?) known from the fossil record. Recently, Conway Morris and Ausich & Babcock have questioned whether Echmatocrinus is in fact an echinoderm, comparing it instead to cnidarians with a polyp-like body and pinnate tentacles, and other authors are beginning to use this reinterpretation. We studied the well-preserved holotype of Echmatocrinus brachiatus, two paratypes, and 18 new specimens recovered from different levels in the Burgess Shale sequence at three localities. All are preserved as pyrite films in dark shale with relatively little relief, suggesting a lightly skeletized body. Complete specimens have a long, slightly tapering, large-plated attachment stalk, a conical cup or calyx with numerous small to medium-sized irregular plates, and 7–10 short arms with heavier plating and (in the holotype) soft appendages alternating from opposite sides of several arms. Several morphologic features indicate that Echmatocrinus is an echinoderm and has crinoid affinities: (1) Sutured plates, shown by darker depressed sutures, slightly raised plate centers, and oriented plate ornament, cover all major parts of the body; (2) reticulate surface ornament in the pyrite film on the plates of all specimens matches the ornament in the Burgess Shale edrioasteroid Walcottidiscus, an undoubted echinoderm, but not the pyritized surfaces of other metazoans in the fauna; (3) this distinctive ornament may represent the surface expression of microporous stereom; (4) possible ligament or muscle pads are present between the arm ossicles to fold and unfurl the more heavily plated arms. Within the echinoderms, only crinoids commonly have a calyx attached by a stalk or stem to the substrate and bear erect, moveable, uniserial arms for feeding. Although Echmatocrinus shows some resemblance to octocorals in overall body shape as an attached suspension feeder, almost all the details are different, indicating that Echmatocrinus is most likely unrelated to this group. All complete specimens of Echmatocrinus are attached to hard substrates, either another fossil or skeletal debris. The new specimens indicate that Echmatocrinus was twice as common (about 0.02%) in the Burgess Shale fauna as previously recorded and represents one of the earliest attached, medium-level, skeletized, suspension feeders or microcarnivores in the fossil record.     

Shell structure of punctate spiriferids (Brachiopoda) from the East European Platform

The shell structure of the Devonian punctate spiriferids Theodossia Nalivkin, 1925, Pyramina Ljaschenko, 1969, Warrenella Crickmay, 1953, Eoreticularia Nalivkin, 1930, Thomasaria Stainbrook, 1945 from the order Spiriferida Waagen, 1883, and also Cyrtina Davidson, 1858 and Punctospirifer North, 1920 from the order Spiriferinida Ivanova, 1972 from the Devonian and Carboniferous of the East European Platform is described.     

A comparative study of Lower Cambrian Halkieria and Middle Cambrian Wiwaxia

Two Cambrian lepidote metazoans known from different respective types of preservation have been compared in order to elucidate their biology and affinities. The widely distributed Lower Cambrian Halkieria is represented by isolated hollow sclerites, probably of originally calcareous composition. The Middle Cambrian Wiwaxia is known from the Burgess Shale as isolated sclerites (scales and spines) and as more or less complete individuals. Although Halkieria sclerites were mineralized and those of Wiwaxia were probably not, there are fundamental structural and morphological similarities between the two. Both bad an imbricating scaly and spiny armour consisting of hollow sclerites with a longitudinally fibrous structure. The sclerites did not grow, but were probably moulted during the course of ontogenetic growth. Halkieria and Wiwaxia are regarded as closely related. Both are referred to the Order Sachitida He 1980. The sclerite armour of Halkieria is reconstructed on the template provided by Wiwaxia. The interpretation of sachitid sclerites as protective armour is an alternative to the interpretation by Jell (1981, Alcheringa 5 )that sachitid sclerites were respiratory organs in an animal of probable annelid affinities. Sachitids are interpreted as sluggish, benthic deposit feeders that do not belong to any recognized phylum.