Michael Streng

A new Burgess Shale–type assemblage from the “thin” Stephen Formation of the southern Canadian Rockies

A new Burgess Shale–type assemblage, from the Stephen Formation of the southern Canadian Rocky Mountains, is described herein. It occurs near Stanley Glacier in Kootenay National Park, 40 km southeast of the type area near Field, British Columbia. While at least a dozen Burgess Shale localities are known from the “thick” Stephen Formation, the Stanley Glacier locality represents the first discovery of Burgess Shale–type fossils from the “thin” Stephen Formation. The Cathedral Escarpment, an important regional paleotopographic feature, has been considered important to the paleoecologic set- ting and the preservation of the Burgess Shale biota. However, the Stanley Glacier assemblage was preserved in a distal ramp setting in a region where no evidence of an escarpment is present. The low- diversity assemblage contains eight new soft-bodied taxa, including the anomalocaridid Stanleycaris hirpex n. gen., n. sp. (new genus, new species). Pelagic or nektobenthic predators represent the most diverse group, whereas in relative abundance, the assemblage is dominated by typical Cambrian shelly benthic taxa. The low diversity of both the benthic taxa and the ichnofauna, which includes diminutive trace fossils associated with carapaces of soft-bodied arthropods, suggests a paleoenvironment with restrictive conditions. The Stanley Glacier assemblage expands the temporal and geographic range of the Burgess Shale biota in the southern Canadian Rockies, and suggests that Burgess Shale–type assemblages may be common in the “thin” Ste- phen Formation, which is regionally widespread.

A PROPOSED CLASSIFICATION OF ARCHEOPYLE TYPES IN CALCAREOUS DINOFLAGELLATE CYSTS

Abstract The phylogenetic significance of archeopyles in calcareous dinoflagellates cysts has been evaluated, and a classification model is developed that focuses on the archeopyle categories and types established for organic-walled dinoflagellates by Evitt (1967, 1985). Several of Evitts archeopyle categories are presently recognized within the calcareous dinoflagellate cysts: apical, intercalary, and combination archeopyles, which are here subdivided into eight archeopyle types and several variations. Archeopyles that cannot be assigned to a distinct type, and those with outlines that do not allow an accurate interpretation, are together placed in a separate category: miscellaneous archeopyles. The stratigraphic distribution of the different archeopyle types reveals a phylogenetic trend characterized by an increase of the number of plates involved in archeopyle formation. The first calcareous dinoflagellate cysts to appear in the late Triassic have a monoplacoid apical archeopyle. The first taxa that show an archeopyle involving more than one plate are from the Early Cretaceous, with the first triplacoid apical archeopyle appearing at the Berriasian/Valanginian boundary. This is followed by the first combination archeopyle, which includes six plates, in the middle Aptian. Epitractal archeopyles originated no earlier than the early Oligocene. At the beginning of the Paleogene, species with a combination archeopyle increased in abundance, progressively replacing species possessing an apical archeopyle that dominated during the Mesozoic. Newly described species are: Calciodinellum clamosum, accommodating the two subspecies Calciodinellum clamosum subsp. clamosum Autonym, and Calciodinellum clamosum subsp. latum; Calciodinellum kerguelense; Fuettererella belliata; and Pernambugia? patata. New combinations are: Cervisiella operculata (Bramlette and Martini, 1964); Praecalcigonellum sulcatum (Keupp, 1979a); and Praecalcigonellum dolium (Keupp, 1979b). Because of the new interpretation of their archeopyles we emend the following genera: Cervisiella Hildebrand-Habel, Willems, and Versteegh, 1999; Echinodinella Keupp, 1980; Fuettererella Kohring, 1993a; and Pernambugia Janofske and Karwath in Karwath (2000). The species Orthopithonella? minuta and Pirumella johnstonei, which have been previously synonymized with Fuettererella deflandrei, are retained as independent taxa.

LOWER ORDOVICIAN (TREMADOCIAN) LINGULATE BRACHIOPODS FROM THE HOUSE AND FILLMORE FORMATIONS, IBEX AREA, WESTERN UTAH, USA

Abstract Seven genera and eight species of lingulate brachiopods were recovered from the House Limestone and lower Fillmore Formation, Ibex area, Utah, USA. These strata are assigned to the upper Skullrockian Stage and lower Stairsian Stage of the Ibexian Series (Iapetognathus Conodont Zone to Low Diversity Interval) and are correlated with the Tremadocian Series of the Acado–Baltic Faunal Province. The fauna includes two new linguloid species, Spinilingula prisca and Wahwahlingula sevierensis, one new siphonotretoid species, Schizambon obtusus, and two new acrotretoid species, Eurytreta fillmorensis and Ottenbyella ibexiana. The last species is the first record of the genus in North America and suggests a correlation of the basal Fillmore Formation with the Ceratopyge Limestone in Sweden. A Siphonobolus? covered by long hollow spines may be one of the oldest siphonotretides with such ornament. This fauna and those described previously from older Utah strata document the biodiversification of the Cambrian–Ordovician lingulate brachiopods and demonstrate their potential for regional and intercontinental correlation.

AGGLUTINATED PROTISTS FROM THE LOWER CAMBRIAN OF NEVADA

Skeletonized protists (or protoctists) appear as body fossils in the late Neoproterozoic and the lower Cambrian (e.g., Allison and Hilgert, 1986; Lipps, 1992; Culver, 1994; Porter et al., 2003) and are well known from the post-Cambrian fossil record. However, molecular data and biomarkers of groups such as ciliates and foraminiferans indicate a long Precambrian history unrecorded by fossils, and also suggest that foraminiferans were important components of Neoproterozoic protistan communities (e.g., Summons et al., 1988; Wright and Lynn, 1997; Lipps, 2003; Pawlowski et al., 2003). The recent discovery of agglutinated microfossils interpreted as foraminiferans from the Neoproterozoic of Uruguay (Gaucher and Sprechmann, 1999) supports the inferences made from molecular data. Although foraminiferans are known for certain since the earliest Cambrian (e.g., McIlroy et al., 2001), their diversity and variability during the Cambrian is limited to a few agglutinated unilocular genera (e.g., Lipps, 1985; Culver, 1991, 1994; Cope and McIlroy, 1998; Zhigulina, 1999; McIlroy et al., 2001). Among these, Platysolenites Pander, 1851 is one of the best known genera because it has a wide distribution and high abundance in lower Cambrian sediments, especially those of Baltica and Avalonia (e.g., Rozanov, 1983; Lipps and Rozanov, 1996; McIlroy et al., 2001). Whether Platysolenites has an affinity with the foraminifera has been questioned by some authors (e.g., Eichwald, 1860; Rozanov, 1983; Brasier, 1989b), but the similarity of its morphology and wall structure to the foraminiferan genus Bathysiphon Sars, 1872 (e.g., Glaessner, 1978), and the presence of proloculi in Platysolenites (e.g., McIlroy et al., 2001) is strong evidence in favor of an affinity with the foraminifera. It should be emphasized that the preservation of proloculi in Platysolenites is rare, reported only in a few cases (McIlroy et al., 1994, …

Linguliform Brachiopods from the Terminal Cambrian and Lowest Ordovician of the Oaxaquia Microcontinent (Southern Mexico)

Abstract Eighteen taxa of linguliform brachiopods, mainly represented by acrotretoids, are reported from the Upper Cambrian (Furongian, Stage 10) and Lower Ordovician (Tremadocian) Tiñu Formation of Oaxaca State, Mexico. At the time of deposition, this area was part of Oaxaquia, which was either a microcontinent or an integral part of the Gondwanan margin. Whereas certain trilobites seem to indicate a Gondwanan affinity, the Tiñu brachiopod faunas show a less definite paleogeographic relationship. Some taxa have previously only been reported from Laurentia (Eurytreta cf. fillmorensis, Eurytreta cf. campaniformis), and one taxon is best known from the Avalon microcontinent (Eurytreta cf. sabrinae). However, the relatively high percentage of new and potentially endemic taxa (Oaxaquiatreta labrifera n. gen. n. sp., Tapuritreta reclinata n. sp., Oaxaquiatreta sp., Eurytreta? n. sp., Acrotretidae n. gen. n. sp., Obolinae gen. and sp. indet.) and the lack of other typical Laurentian, Gondwanan, or Avalonian taxa suggest either a certain degree of insularity of Oaxaquia or reflects a more temperate, unrestricted marine environment during the Early Paleozoic. Other taxa reported from the Tiñu Formation include Semitreta sp., Lingulella? spp., Obolinae gen. and sp. indet., Eoscaphelasma? sp., Ottenbyella? sp. A and sp. B, and Acrotretidae gen. and sp. indet. A, B, and C. Eurytreta and Semitreta are critically reviewed and several taxa previously assigned to them have been excluded. An emended diagnosis for the genus Eurytreta is presented. The presence of delthyrium and notothyrium-like structures in the siphonotretid Oaxaquiatreta n. gen. further strengthens the previously proposed relationship between the Siphonotretida and Paterinida.

Well-preserved mollusks from the Lower Keuper (Ladinian) of Hohenlohe (Southwest Germany)

KurzfassungDie „Unteren Grauen Mergel“, ein wechselhaft siliziklastisch-karbonatisches Schichtglied der oberen Erfurt-Formation (Unterkeuper) des Hohenloher Landes, enthält lokal eine Fauna mit außergewöhnlich gut erhaltenen Mollusken. Zusammen mit einer Untersuchung von Museumsmaterial erlaubt das neue Material die Revision häufiger, aber bisher oft fehlinterpretierter Muschel- und Schneckentaxa. Die Muschelfauna setzt sich zusammen ausBakevellia (B.) subcostata, Myophoria transversa, Unionites brevis undU. donacinus. Schlossbau und Muskelabdrücke der ladinischen ArtBakevellia (B.) subcostata stimmen mit der permischen Typusart der Gattung weitgehend überein. Die interne Morphologie der GattungBakevellia s.s. blieb somit über einen bemerkenswert langen geologischen Zeitraum konstant. WederB. (Neobakevellia) nochB. (Costibakevellia) unterscheiden sich in ihrer Morphologie signifikant vonBakevellia s.s. und sind daher als deren jüngere Synonyme anzusehen.Myophoria transversa unterscheidet sich vonM. vulgaris nicht nur durch einen größeren Winkel zwischen extraarealer Rippe und Arealkante, sondern auch durch die Reduktion der Schlossplatte in der rechten Klappe und einen basal eingebuchteten zentralen Zahn in der linken Klappe. Der morphologische Befund an den untersuchten Stücken der GattungUnionites weist darauf hin, dassUnionites den Anthracosiidae und nicht den Trigonodidae („Pachycardiidae“) zuzuordnen ist.Unionites brevis wurde in der Vergangenheit meist fälschlicherweise unter dem NamenU. letticus beschrieben; tatsächlich gehören beide Taxa vermutlich sogar verschiedenen Familien an. Die zahlreichen Gastropoden der GattungNeritaria zeigen noch die ursprüngliche aragonitische Schalenstruktur und Farbstreifen. Eine detaillierte morphome-trische Analyse belegt, dass die Arten morphologisch bemerkenswert variabel sind. Die Taxonomie ist dagegen im Augenblick nicht exakt darzustellen, weil die Kenntnis der zahlreichen mitteltriadischen Neritarien aus dem Germanischen Becken völlig unzureichend ist. Eine neue Art der Neritarien mit einer ungewöhnlichen,Hologyra-artigen Ornamentierung wird unter dem Namen„Neritaria“ interscripta n. sp. beschrieben.AbstractA mixed siliciclastic-calcareous member (“Untere Graue Mergel“) of the upper Erfurt Formation (Lower Keuper) of the Hohenlohe area locally includes a fauna with exceptionally well preserved bivalves and gastropods. The bivalves includeBakevellia (B.) subcostata, Myophoria transversa, Unionites brevis andU. donacinus. Hinge structure and muscle impressions ofBakevellia (B.) subcostata are virtually identical with those of the Permian type species ofBakevellia B. (Neobakevellia) andB. (Costibakevellia) are regarded as (younger) Synonyms ofBakevellia s.s.Myophoria transversa differs fromM. vulgaris not only by the greater angle between areal carina and extra-areal rib but also by the reduction of the hinge plate in the right valve and by a less clearly bifid central tooh in the left valve. New morphological find (in particular hinge morphology) suggest thatUnionites belongs to the Anthracosiidae rather than to the Trigonodidae (“Pachycardiidae”).Unionites brevis has commonlybeen misidentified asU. letticus. Both taxa most probably belong even to different families. The frequent gastropods of the genusNeritaria retained their aragonitic shell and show color bands. Morphometric analysis indicates a remarkable plasticity. Taxonomic assignment, however, has to remain equivocal because of deficiencies of knowledge on the numerous mid-Triassic neritarian taxa from the Germanic Basin. Neritarian gastropodswith unusualHologyra-type exterior morphology are described as the new species“Neritaria” interscripta n. sp.

Columnar shell structures in early linguloid brachiopods - new data from the Middle Cambrian of Sweden

The records of columnar shell structures of linguloid brachiopods (Class Lingulata, Order Lingulida, Superfamily Linguloidea) are reviewed in the light of the discovery of two new taxa from the Middle Cambrian Forsemolla Limestone Bed of southern Sweden. The linguloid taxa, described here as Eoobolus? sp. aff. E. priscus (Poulsen) and Canalilatus? simplex sp. nov., are both characterised by a columnar shell structure, a structural type that is representative for acrotretoid brachiopods and that has previously only rarely been reported from the linguloids. Though the two taxa are superficially similar to known genera, i.e., Eoobolus and Canalilatus, their shell structure challenges such affiliations, as the shell structure of the type species of these genera is previously unknown. Linguloid families whose morphological characteristics agree the most with those of the new taxa, i.e., the Zhanatellidae and the Eoobolidae, and from which columnar shell structures have been reported, i.e., the Lingulellotretidae and the Kyrshabaktellidae, are reviewed briefly. Many taxa assigned to these families completely lack shell structure data and are in need of restudy in order to elucidate their systematic position. Knowledge of the representative type of shell structure of the various suprageneric taxa within the Linguloidea is considered crucial, in order to unravel their currently poorly resolved phylogenetic relationships.

Setatella significans, a new name for mickwitziid stem group brachiopods from the lower Cambrian of Greenland and Labrador

Setatella significans gen. et sp. nov. from the Lower Cambrian of North-East Greenland, originally described under the name ‘Mickwitzia cf. occidens’, is introduced as a probable stem group brachiopod. Newly collected specimens of Setatella significans from the Forteau Formation of southern Labrador exhibit new morphological details and provide a better understanding of its ontogeny. Setatella significans differs from species of Mickwitzia in having a ventral pseudointerarea and hemiperipheral growth in both valves. Setatella significans probably belongs to the derived stem group of the Linguliformea that can be differentiated from the more primitive Mickwitzia. The geographic range of Setatella is extended to southern Labrador.

A new mobergellan (small shelly fossils) from the Middle Cambrian of Morocco and its significance

A new mobergellan genus and species,Tateltella ranoculata, is described from the early Middle Cambrian (Agdzian Stage) of Morocco. The new taxon is characterized by only four pairs of muscle scars and is furthermore distinguished from other mobergellans by its strongly concave shape and its distally rising muscle scars. The individual specimens ofTateltella ranoculata distinctly vary in size and display different ontogenetic stages. Juvenile, intermediate, and adult stages can be distinguished by means of the development of the muscle scars that differ in Position relative to the apex, size, and distinctness between individual stages. The shell ofT. ranoculata is composed of a succession of thin phosphatic lamellae separated by interlamellar gaps, presumably originally filled by organic material. The interlamellar gaps may be divided by septum-like structures producing discrete cavities. The specimens are the youngest mobergellans known so far and correlation of their stratigraphic position suggests a correspondence with the lower part of the Amgan stage of the Siberian Platform. In addition, they are the first reported mobergellans from the present day continent Africa. Other mobergellan taxa and mobergellan-like species are briefly reviewed and the genusHippoklosmaMissarzhevsky, previously assigned to the Mobergellidae, is excluded from the family due to its different shell structure. An evolutionary trend of reduction in the number of muscle scars from 14 in the early Early Cambrian to only eight in the early Middle Cambrian is apparent among mobergellans.KurzfassungEine neue Gattung und Art der Familie Mobergellidae (incertae sedis),Tateltella ranoculata, wird aus dem unteren Mittelkambrium (Agdzium-Stufe) von Marokko beschrieben. Das neue Taxon ist durch seine einzigartige Kombination von Merkmalen von anderen Repräsentanten der Familie unterschieden. Lediglich vier Paar nach distal ansteigende Muskelabdrücke und eine stark konvexe Form kennzeichnen seine Schale. Die einzelnen Exemplare vonT. ranoculata variieren stark in ihrer Größe und repräsentieren unterschiedliche ontogenetische Stufen. Es können eine juvenile, eine intermediäre und eine adulte Entwicklungsphase unterschieden werden, die durch die unterschiedliche Ausprägung und Position der Muskelabdrücke gekennzeichnet sind. Die Schale vonT. ranoculata besteht aus einer Abfolge von dünnen, phosphatischen Lagen („lamellae“), die durch vermutlich primär mit organischen Material gefüllten Zwischenräume voneinander getrennt sind. Diese Zwischenräume können durch Septeneinschaltungen in einzelne Kammern untergliedert sein. Das stratigraphische Niveau der gefunden Exemplare korreliert mit der unteren Amga-Stufe der Sibirischen Tafel und stellt somit das jüngste bislang bekannte Niveau für Mobergelliden dar. Weitere Vertreter der Mobergelliden werden kurz besprochen, und die bislang zur Familie gezählte GattungHippoklosmaMissarzhevsky wird aufgrund ihrer andersartigen Schalenstruktur von der Familie ausgeschlossen.

A Walcottella-like bradoriid (Arthropoda) from the lower Cambrian of Sweden

Abstract A probable new bradoriid genus and species, represented by a single specimen, is described tentatively as Walcottella? aff. apicalis Ulrich & Bassler from lower Cambrian strata of Sweden. The specimen comes from the Bergmyrhobben section west of Storuman in Västerbotten County, northern Sweden. It was found in mudstone in the lower part of the Grammajukku Formation, co-occurring with a rich acritarch assemblage of the Skiagia ornata-Fimbriaglomerella membranacea acritarch Zone that corresponds to the Schmidtiellus trilobite Zone. The specimen represents one of the oldest bradoriids known from the paleocontinent Baltica. Characteristics of the specimen are a dorsomedian to mid-dorsal acuminate nod and a flattened shell border along the free margin, the latter feature unknown from other bradoriid taxa. The specimen occurs at the same level where the first trilobites were found in the investigated section. The biogeographic affinities of the Baltic bradoriid genera to the bradoriid fauna of Avalonia, western Gondwana and Laurentia are reviewed and discussed.