The diverse radiodont fauna from the Marjum Formation of Utah, USA (Cambrian: Drumian) (original) (raw)
Related papers
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.
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.
A NEW METAZOAN FROM THE MIDDLE CAMBRIAN OF UTAH AND THE NATURE OF THE VETULICOLIA
Palaeontology, 2005
A new metazoan, Skeemella clavula gen. et sp. nov., is described from the Middle Cambrian Pierson Cove Formation of the Drum Mountains, Utah, USA. Skeemella is similar to vetulicolians, but differs from other examples of this group in the relative proportions of the anterior and posterior sections, the large number of divisions, and the elongate bifid termination. The posterior section is arthropodan in character. The similarity of this fossil to vetulicolians throws hypotheses of their deuterostome affinity into question and highlights their problematic sta- tus.
Journal of Paleontology, 2023
The Cambrian (Miaolingian; Wuliuan) Spence Shale Lagerstätte of northern Utah and southern Idaho is one of the most diverse Burgess Shale-type deposits of Laurentia. It yields a diverse fauna consisting of abundant biomineralized and locally abundant soft-bodied fossils, along a range of environments from shallow-water carbonates to deepshelf dark shales. Panarthropods are the dominant component throughout the deposit, both in time and space, but whereas the trilobites and agnostoids are abundant, most of the soft-bodied taxa are only known from very few specimens. Additionally, the knowledge of soft-bodied panarthropods is currently largely limited to locations in the Wellsville Mountains of northeastern Utah. This contribution describes 21 new soft-bodied panarthropods from six locations, including the first occurrences of soft-bodied panarthropods in the High-Creek, Smithfield Creek, Spence Gulch, and Two-Mile Canyon localities. Additionally, we report the presence of bradoriids-i.e., Branchiocaris pretiosa Resser, 1929, Perspicaris? dilatus Robison and Richards, 1981, Naraoia? sp. indet., Thelxiope cf. T. palaeothalassia Simonetta and Delle Cave, 1975, and Tuzoia guntheri Robison and Richards, 1981-for the first time from the Spence Shale Lagerstätte; the first reported occurrence outside of the Burgess Shale for Thelxiope cf. T. palaeothalassia; and the first Wuliuan occurrence of Tuzoia guntheri. We also report on a new hurdiid carapace element and additional specimens of Buccaspinea cooperi? Pates et al., 2021, Dioxycaris argenta Walcott, 1886, Hurdia sp. indet., and Tuzoia retifera Walcott, 1912. This new material improves our understanding of the panarthropod fauna of the Spence Shale Lagerstätte and substantially increases our understanding of the distribution of the described taxa in time and space.