Occurrence of the eudemersal radiodontCambrorasterin the early Cambrian Chengjiang Lagerstätte and the diversity of hurdiid ecomorphotypes

Abstract

<jats:title>Abstract</jats:title><jats:p>Radiodonts are a diverse clade of Lower Palaeozoic stem-group euarthropods that played a key role in the emergence of complex marine trophic webs. The latest addition to the group, <jats:italic>Cambroraster falcatus</jats:italic>, was recently described from the Wuliuan Burgess Shale, and is characterized by a unique horseshoe-shaped central carapace element. Here we report the discovery of <jats:italic>Cambroraster</jats:italic> sp. nov. A, a new species from the Cambrian Stage 3 Chengjiang Lagerstätte of South China. The new occurrence of <jats:italic>Cambroraster</jats:italic> demonstrates that some of the earliest known radiodonts had already evolved a highly derived carapace morphology adapted to an essentially eudemersal life as sediment foragers.</jats:p>

Occurrence of the hurdiid radiodontCambrorasterin the middle Cambrian (Wuliuan) Mantou Formation of North China

“…In addition, Cambroraster represents the first discovery of hurdiid radiodonts in North China. This group has been found previously in Laurentia (e.g., Briggs et al, 2008;Daley et al, 2009Daley et al, , 2013Caron et al, 2010;Pates et al, 2017Pates et al, , 2018Pates et al, , 2019aLerosey-Aubril and Pates, 2018;Kimmig et al, 2019), South China (e.g., Liu, 2013;Zeng et al, 2017;Liu et al, 2020), West Gondwana (e.g., Van Roy and Briggs, 2011;Van Roy et al, 2015), and Baltica (e.g., Chlupác and Kordule, 2002;Daley and Legg, 2015). The discovery of a hurdiid in North China indicates that this group as a whole had a good dispersal ability, which could have contributed to its successful colonization in various ecological niches (Daley and Budd, 2010;Vinther et al, 2014;Van Roy et al, 2015;Lerosey-Aubril and Pates, 2018;Moysiuk and Caron, 2019).…”

“…As one of the two main lineages of Radiodonta, Hurdiidae Lerosey-Aubril and Pates, 2018 is characterized by a tripartite head sclerite complex and frontal appendages with pectinate ventral spines. This family includes Peytoia Walcott, 1911, Hurdia Walcott, 1912, Pahvantia Robison and Richards, 1981, Zhenghecaris Vannier et al, 2006, Schinderhannes Kühl et al, 2009, Stanleycaris Pates et al, 2017 (Caron et al, 2010), Aegirocassis Van Roy et al, 2015, Tauricornicaris Zeng et al, 2017, Ursulinacaris Pates et al, 2019a, and Cambroraster Moysiuk and Caron, 2019 and was diverse and successful in different ecological niches in the middle Cambrian (Miaolingian) and later (e.g., Daley and Budd, 2010; Van Roy et al, 2015; Lerosey-Aubril and Pates, 2018; Moysiuk and Caron, 2019; Liu et al, 2020). The genus Cambroraster , first discovered from the Burgess Shale (Moysiuk and Caron, 2019), is readily distinguishable from other hurdiid taxa by its central head sclerite with deep posterior notches, a rounded anterior margin, and posterolateral processes bearing multiple spines.…”

The diverse radiodont fauna from the Marjum Formation of Utah, USA (Cambrian: Drumian)

“…Radiodonts greatly differed in size, ranging from millimetres to meters in length ( Van Roy, Daley & Briggs, 2015 ; Lerosey-Aubril & Pates, 2018 ; Liu et al, 2018 ; Pates et al, 2020a ), and had variable body shapes that impacted their swimming capabilities. Radiodonts are typically reconstructed as nektonic animals (also referred to as ‘free swimmers’ hereafter), with the possible exception of the eudemersal Cambroraster ( Moysiuk & Caron, 2019 ; Liu et al, 2020 ). Forms with elongate swimming flaps and reduced cephalic sclerites (amplectobeluids and anomalocaridids; Daley & Edgecombe, 2014 ; Cong et al, 2014 , 2016 , 2017 , 2018 ; Liu et al, 2018 ) were likely more agile swimmers than those with comparatively reduced, but paired flaps, and cylindrical bodies made semi-rigid by the presence of an elongate cephalic carapace (e.g.…”

Disparate compound eyes of Cambrian radiodonts reveal their developmental growth mode and diverse visual ecology

“…The radiodont head also features a range of sclerites or carapace elements that have only come to light in the past 15 years ( 15 ). These include separate dorsal and lateral cephalic plates [as in Anomalocaris ( 10 , 16 ), Amplectobelua ( 13 ), and Lyrarapax ( 6 )], an integrated carapace composed of dorsal and lateral elements [as in Hurdia ( 17 )], or in one unusual example, an expanded, horseshoe-shaped carapace [as in Cambroraster ( 10 , 18 , 19 )].…”