Systematics, preservation and biogeography of radiodonts from the southern Great Basin, USA, during the upper Dyeran (Cambrian Series 2, Stage 4)

Abstract

Anomalocaris, the most well‐known genus of the diverse stem euarthropod group Radiodonta, was first reported over 100 years ago from the Burgess Shale (Canada). This large Cambrian apex predator was later treated as occurring in the southern Great Basin (California and Nevada, USA). We re‐evaluate the systematic affinities of previously described material from the Pioche Formation, Nevada, and the Latham Shale, California, and describe the first radiodonts from the Pyramid Shale Member, Carrara Formation, California. Latham Shale (Cambrian Series 2, Stage 4, upper Dyeran) specimens previously assigned to Anomalocaris are reinterpreted as Ramskoeldia consimilis?, an amplectobeluid previously known only from the Chengjiang biota (Cambrian Series 2, Stage 3). Younger material from the Pioche and Carrara Formations (Series 2, Stage 4) is described as a new Anomalocaris species, A. magnabasis. This new species sheds light on the two‐part structure of Anomalocaris ventral endites, a potentially important character for distinguishing species, and reveals a sequence of five disarticulation stages for frontal appendages. The oldest Hurdia from Laurentia is also reported from the Pioche Formation (Cambrian Series 2, Stage 4). A changeover in taxonomic composition of the Radiodonta in the southern Great Basin is recognized: Anomalocaris replaces Ramskoeldia in the upper Dyeran, but it is not associated with a replacement of local olenelloid trilobites or seen in radiodonts elsewhere in Laurentia. These new data, combined with a summary of known radiodont occurrences, suggest that Anomalocaris species did not have large geographical distributions, when compared with other radiodonts such as Hurdia and Caryosyntrips.

New exceptionally preserved panarthropods from the Drumian Wheeler Konservat‐Lagerstätte of the House Range of Utah

“…2009, 2013; Pates et al . 2018a, 2019; this study). The two species are distinguished based on the shape of the central (H‐) element of the cephalic carapace only (Daley et al .…”

“…(2018) (see also Pates et al . 2019) proposed to restrict it to the genera Amplectobelua and Ramskoeldia only, using as diagnostic characters the presence of three pairs of gnathobase‐like structures, and an endite on the fifth podomere of the distal articulated region that is longer than the one borne by its third podomere. A. stephenensis is known from frontal appendages alone, and in most specimens the very short nature of the endites on P2–9 prevents a confident assessment of their relative lengths.…”

“…2018; Pates et al . 2019). Last, the Wheeler specimen also represents the youngest occurrence of the family Amplectobeluidae, which has not been found in younger radiodont‐bearing Konservat‐Lagerstätten yet (e.g.…”

A new species of the deuterostome Herpetogaster from the early Cambrian Chengjiang biota of South China

“…For instance, the documented diversity of early deuterostomes in Cambrian BST deposits continues to climb. This study also suggests that there may be a close biogeographic relationship between Herpetogaster from the Cambrian stage 3 of South China and the Cambrian stage 4 and Wuliuan stage of Laurentia (for a recent discussion of biogeography of Cambrian BST deposits in South China and Laurentia see Pates et al 2019). However, whether this biogeographic relationship is related to patterns of faunal migration or instead simply reflects an incomplete knowledge of Herpetogaster diversity and distribution awaits future discoveries.…”

A miniature Ordovician hurdiid from Wales demonstrates the adaptability of Radiodonta

“…[15][16][17][18][19][20]) to North America (e.g. [7,12,13,[21][22][23][24][25][26][27][28][29]), Europe [25,30,31], North Africa [32,33] and Australia [34][35][36], reflecting the widespread nature of these (mostly) nektonic animals across different palaeocontinents from the equator to the poles.…”