A NEW METAZOAN FROM THE MIDDLE CAMBRIAN OF UTAH AND THE NATURE OF THE VETULICOLIA (original) (raw)
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Utah Geological Association Publication 45:291-336, 2016
The middle Cambrian succession of Utah’s West Desert offers an outstanding record of one of the most important periods in Earth history, and in recent decades it has provided one of the most important faunal records of this time interval in the world. A total of 18 formations comprise the middle Cambrian (Series 3) succession of the West Desert and, together, they span the entirety of the series, with the Eokochaspis through Cedaria trilobite zones represented. For more than a century the middle Cambrian strata of the area have been well-known for their abundant, diverse, and well-preserved trilobites, which are especially prominent in the Wheeler, Marjum, and Weeks formations. The paleoenvironmental conditions that promoted the preservation of articulated trilobites and other mineralized organisms also contributed to soft-bodied preservation of Burgess Shale-type biotas in those units. The particularly rich fossil record from this area includes endemic taxa that are unique to the region as well as those found elsewhere in Laurentia and on other paleocontinents. In recent years, understanding of the middle Cambrian biotas from western Utah has increased as new taxa, including many soft-bodied forms, have been discovered. In the past year alone, species diversity from the Wheeler, Marjum, and Weeks formations has been expanded considerably. Taxa new to the Wheeler Formation include the protomonaxonid Lenica cf. hindei, the vetulocystid Thylacocercus ignota, the hemichordate Sphenoecium wheelerensis, and the conulariid Cambrorhytium sp. Those from the Marjum Formation include the arthropod Dytikosicula desmatae, the cambroernid Eldonia ludwigi, and the new pterobranch hemichordate, Sphenoecium wheelerensis. The new arthropod Falcatamacaris bellua from the Weeks Formation joins two other new arthropod taxa described since 2013. The steady increase in taxonomic diversity of these units has contributed greatly to understanding the complex ecosystems that thrived in this region during the middle Cambrian. Recent work has also shed light on the living environments and circumstances surrounding exceptional preservation of the fossil assemblages. The House Range embayment, a deep water trough that first developed at the onset of Wheeler deposition, gradually filled through time, resulting in an overall shallowing upwards sequence and a general decrease in the frequency of soft-bodied preservation.
The diverse radiodont fauna from the Marjum Formation of Utah, USA (Cambrian: Drumian)
PeerJ
Radiodonts have long been known from Cambrian deposits preserving non-biomineralizing organisms. In Utah, the presence of these panarthropods in the Spence and Wheeler (House Range and Drum Mountains) biotas is now well-documented. Conversely, radiodont occurrences in the Marjum Formation have remained scarce. Despite the large amount of work undertaken on its diverse fauna, only one radiodont (Peytoia) has been reported from the Marjum Biota. In this contribution we quadruple the known radiodont diversity of the Marjum fauna, with the description of the youngest members of two genera, Caryosyntrips and Pahvantia, and that of a new taxon Buccaspinea cooperi gen. et sp. nov. This new taxon can be identified from its large oral cone bearing robust hooked teeth with one, two, or three cusps, and by the unique endite morphology and organisation of its frontal appendages. Appendages of at least 12 podomeres bear six recurved plate-like endites proximal to up to four spiniform distal endi...
First palaeoscolecid from the Cambrian (Drumian, Miaolingian) Marjum Formation of western Utah, USA
ACTA PALAEONTOLOGICA POLONICA, 2021
The middle Marjum Formation is one of five Miaolingian Burgess Shale-type deposits in Utah, USA. It preserves a diverse non-biomineralized fossil assemblage, which is dominated by panarthropods and sponges. Infaunal components are particularly rare, and are best exemplified by the poorly diverse scalidophoran fauna and the uncertain presence of palaeoscolecids amongst it. To date, only a single Marjum Formation fossil has been tentatively assigned to the palaeoscolecid taxon Scathascolex minor. This specimen and two recently collected worm fragments were analysed in this study using scanning electron microscopy and energy dispersive X-ray spectrometry. The previous occurrence of a Marjum Formation palaeoscolecid is refuted based on the absence of sclerites in the specimen, which we tentatively assign to an unidentified species of Ottoia. The two new fossils, however, are identified as a new palaeoscolecid taxon, Arrakiscolex aasei gen. et sp. nov., characterized by the presence of hundreds of size-constrained (20-30 µm), smoothrimmed, discoid plates on each annulus. This is the first indisputable evidence for the presence of palaeoscolecids in the Marjum biota, and a rare occurrence of the group in the Cambrian of Laurentia. Palaeoscolecids are now known from nine Cambrian Stage 3-Guzhangian localities in Laurentia, but they typically represent rare components of the biotas.
We describe a weakly biomineralized non-trilobite artiopodan arthropod from the Guzhangian Weeks Formation of Utah. Falcatamacaris bellua gen. et sp. nov. is typified by a thin calcitic cuticle, broad cephalon without eyes or dorsal ecdysial sutures, an elongate trunk with distinctively sickle-shaped pleural spines, and a long tailspine with a bifurcate termination. The precise affinities of Falcatamacaris gen. nov. are problematic due to the presence of unique features within Artiopoda, such as the peculiar morphology of the pleural and posterior regions of the trunk. Possible affinities with aglaspidid-like arthropods and concilitergans are discussed based on the possession of 11 trunk tergites, edge-to-edge articulations and overall body spinosity. The new taxon highlights the importance of the Weeks Formation Konservat-Lagerstätte for further understanding the diversity of extinct arthropod groups in the upper Cambrian.
Journal of Paleontology, 2020
In recent years the plethora of ‘weird wonders,’ the vernacular for the apparently extinct major body plans documented in many of the Cambrian Lagerstätten, has been dramatically trimmed. This is because various taxa have been either assigned to known phyla or accommodated in larger monophyletic assemblages. Nevertheless, a number of Cambrian taxa retain their enigmatic status. To this intriguing roster we add Dakorhachis thambus n. gen. n. sp. from the Miaolingian (Guzhangian) Weeks Formation Konservat-Lagerstätte of Utah. Specimens consist of an elongate body that lacks appendages but is apparently segmented. A prominent feeding apparatus consists of a circlet of triangular teeth, while posteriorly there are three distinct skeletal components. D. thambus is interpreted as an ambush predator and may have been partially infaunal. The wider affinities of this new taxon remain conjectural, but it is suggested that it may represent a stem-group member of the Gnathifera, today represent...