Proposed Early Cambrian cephalopods are chimaeras, the oldest known cephalopods are 30 m.y. younger

Peer reviewe

Devonian hyoliths in South Africa, and their palaeoenvironmental significance

Hyoliths, an extinct group of molluscan or mollusc-like invertebrates that secreted elongate conical shells, are relatively uncommon and often overlooked members of Middle Palaeozoic marine fossil assemblages. They have been recorded from a number of widespread localities in the argillaceous Gydo and Voorstehoek Formations of the Bokkeveld Group. Most of the specimens are crushed or are without opercula and other taxonomically important features of the aperture and therefore must remain indeterminate. The hyoliths occur in bioturbated mudstones along with brachiopods, trilobites, bivalves, gastropods, crinoids, cephalopods and conulariids. This assemblage is interpreted as representing an inner shelf community that occupied quiet waters below wave base seaward of the prograding Bokkeveld deltas. Unlike many of the other elements of the shelf community, the epifaunal, deposit-feeding hyoliths are not found in the shallower water communities and can be taken as diagnostic of the offshore environments

Grandes hitos de la Explosión Cámbrica: asociación bentónica macrobioclástica en el Piso cámbrico inferior 2 del Olenek Uplift, Siberia ártica

The basal Cambrian Stage 2 strata of the Olenek Uplift host diverse assemblages of macroscopic fossils, which closely resemble certain small skeletal taxa early reported from this section and typical for the Terreneuvian Epoch. Herein studied macroscopic assemblage includes helcionellid, stenothecid and kharkhaniid molluscs, and anabaritids and circothecid hyoliths. Among the assemblage, only anabaritids and some citrcothecid hyoliths exhibit relics of calcite shell, whereas most of the fossils reveal no evidence of rigid biomineralized exoskeleton. Hence, at least these problematic Cambrian organisms had reached macroscopic sizes (up to 35 mm long) and were covered with calcite shells at the very beginning of the Cambrian Age 2.Los estratos basales del Piso cámbrico 2 del Olenek Uplift albergan diversos conjuntos de fósiles macroscópicos, que se asemejan mucho a ciertos pequeños taxones esqueléticos documentados en esta sección y típicos del Terranoviense. En este caso, la asociación macroscópica estudiada incluye moluscos helcionélidos, estenotécidos y kharkhánidos, así como hiolitos de tipo anabarítido y circotécidos. Entre ellos, sólo los anabarítidos y algunos hiolitos circotécidos muestran restos de concha calcítica, mientras que la mayoría de los fósiles carecen de exoesqueleto rígido biomineralizado. Por tanto, al menos estos organismos cámbricos problemáticos habrían alcanzado tamaños macroscópicos (de hasta 35 mm de largo) y estaban cubiertos con conchas calcíticas al principio del Pisp cámbrico 2

New middle Cambrian hyolith genus and species and echinoderm ossicles from the Georgina Basin, Australia

The study herein describes a new genus and species of orthothecid hyolith and numerous echinoderm ossicles. The internal mold of the hyolith bears an apical ridge and is of uniform width, distinguishing it from other known hyoliths. Biological significance of its internal apical structure is unclear, though hypotheses proposed include a streamlining effect and presence of a terminal spine on the original shell. Inclusion of the supposed Circotheca stylus depicted in Dzik (1980: fig. 7) into this species expands the newly described hyolith’s geographic range to Baltica and extends its temporal occurrence into the Late Cambrian. Some of the ossicles resemble echinoderm taxa (e.g., stylophorans and eocrinoids), but many ossicle morphologies share little to no similarities to known Cambrian echinoderms. Several fragmented ossicles bear phosphatic casts around their pores similar to Cantabria labyrinthica remains. Such results suggest that C. labyrinthica may represent echinoderm ossicles, not lobopodian plates as originally proposed by Clausen and Álvaro (2006)

Sedimentology and palaeontology of the Withycombe Farm Borehole, Oxfordshire, England

The pre-trilobitic lower Cambrian of the Withycombe Formation is a 194 m thick siliciclastic succession dominated by interbedded offshore red to purple and green pyritic mudstone with minor sandstone. The mudstone contains a hyolith-dominated small shelly fauna including: orthothecid hyoliths, hyolithid hyoliths, the rostroconch Watsonella crosbyi, early brachiopods, the foraminiferan Platysolenites antiquissimus, the coiled gastropod-like Aldanella attleborensis, halkieriids, gastropods and a low diversity ichnofauna including evidence of predation by a vagile infaunal predator. The assemblage contains a number of important index fossils (Watsonella, Platysolenites, Aldanella and the trace fossil Teichichnus) that enable correlation of strata around the base of Cambrian Stage 2 from Avalonia to Baltica, as well as the assessment of the stratigraphy within the context of the lower Cambrian stratigraphic standards of southeastern Newfoundland. The pyritized nature of the assemblage has enabled the study of some of the biota using micro-CT, augmented with petrographic studies, revealing pyritized microbial filaments of probable giant sulfur bacteria. We aim to produce the first complete description of the core and the abundant small pyritized fossils preserved in it, and develop a taphonomic model for the pyritization of the “small” shelly fossils

The Oldest Hyolithids (Cambrian Series 2, Montezuman Stage) From The Iapetan Margin Of Laurentia

The recent description of the nevadioid trilobite Buenellus chilhoweensis Webster and Hageman, 2018 established the presence of early Cambrian Montezuman Stage (Cambrian Series 2, Stage 3) faunas in the Murray Shale of Chilhowee Mountain, Tennessee. The description recognized the oldest known age-diagnostic Cambrian trilobite from the Laurentian margin of the former Iapetus Ocean since Buenellus Blaker, 1988 is known otherwise only from the Sirius Passet Lagerstatte on the Innuitian margin of North Greenland. The bivalved arthropods Isoxys chilhoweanus Walcott, 1890 and Indota tennesseens is (Resser, 1938a) have also been described from the Murray Shale, but hyolithids appear to be the dominant body fossils in terms of diversity and abundance. Although poorly preserved, the hyolithids occurring together with Buenellus chilhoweensis are described to improve understanding of the Murray Shale biota. The hyolith assemblages of the Murray Shale and Sirius Passet Lagerstatte are not closely similar, although the poor preservation of both hinders comparison

Coprolites in the Ravens Throat River Lagerstätte of northwestern Canada: implications for the middle Cambrian food web

The Rockslide Formation (middle Cambrian, Drumian, Bolaspidella Zone) of the Mackenzie Mountains, northwestern Canada, hosts the Ravens Throat River Lagerstätte, which consists of two, 1-m thick intervals of greenish, thinly laminated, locally burrowed, slightly calcareous mudstone yielding a low-diversity and low-abundance fauna of bivalved arthropods, ‘worms’, hyoliths, and trilobites. Also present are flattened, circular, black carbonaceous objects averaging 15 mm in diameter, interpreted as coprolites preserved in either dorsal or ventral view. Many consist of aggregates of ovate carbonaceous flakes 0.5–2 mm long, which are probably compacted fecal pellets. Two-thirds contain a variably disarticulated pair of arthropod valves, and many also contain coiled to fragmented, corrugated ‘worm’ cuticle, either alone or together with valves. A few contain an enrolled agnostoid. In rare cases a ptychoparioid cranidium, agnostoid shield, bradoriid valve, or hyolith conch or operculum is present; these are taken to be due to capture and ingestion of bioclasts from the adjacent seafloor. Many of the coprolites are associated with semi-circular spreiten produced by movement of the worm-like predator while it occupied a vertical burrow. Its identity is unknown but it clearly exhibited prey selectivity. Many coprolites contain one or more articulated hyoliths, ptychoparioid trilobites, or outstretched agnostoid arthropods oriented dorsal side up. These are interpreted as opportunistic coprovores drawn to the organic-rich fecal mass while it was lodged near the entrance to the burrow. This argues that hyoliths were mobile detritivores, and agnostoids were mainly nektobenthic or benthic, like the ptychoparioid trilobites. Fecal matter was probably an important source of nutrition in the Cambrian food web

Aspects of geodiversity of Palaeozoic limestones in the Black Mountains of southern France

International audienceAfter a few words about the Black Mountains of Southern France as a geographical and geological object, the paper develop a study of Palaeozoic limestones in "Montagne Noire" from outcrop to landscape, offering a big bunch of geodiversity. This essay is a tribute to our late distinguished colleague Bojan Erhartic, geomorphologist at the Anton Melik Geographical Institute