Shucaris

Shucaris Temporal range: Early Cambrian,
MicroCT of the holotype, a frontal appendage
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	†Dinocaridida
Order:	†Radiodonta
Genus:	†Shucaris Wu et al., 2024
Species:	†S. ankylosskelos
Binomial name
†Shucaris ankylosskelos Wu et al., 2024

Shucaris (IPA: [ʃuˈkaː.ris]) (meaning "Shu's shrimp") is a genus of radiodont of uncertain taxonomic placement from the Lower Cambrian Maotianshan Shales in Yunnan, South China. The type and only species is S. ankylosskelos, known from multiple specimens comprising frontal appendages, multiple endites, gnathobase‐like structures, a nearly complete body, a head carapace complex, and one body flap associated with setal blades.

Description

Shucaris is known from multiple specimens which were all referred to S. ankylosskelos by Wu et al. (2024). The holotype, JS-0972B, consists of an isolated frontal appendage. The paratypes, JS-1950 and JS-0658, comprise a nearly complete body specimen and one partial disarticulated gnathobase-like structure, and a head carapace complex and one body flap associated with setal blades, respectively.

Etymology

The generic name is Shucaris (IPA: [ʃuˈkaː.ris]). 'Shu' honours Professor Degan Shu, the pioneer in the research on the Chengjiang biota and the academic leader of the Early Life Research Team at Northwest University. 'Caris', translating to ‘shrimp’ from Latin, is a commonly used suffix for marine euarthropods. The specific name, ankylosskelos (IPA: [aŋkylosːtɛgɔs]), derives from the Greek words for 'curved' and 'leg' respectively, alluding to the curved frontal appendage.

Classification

In previous studies, Shucaris was referred to as "Radiodont C" and has been recovered as an amplectobeluid and a basal anomalocaridid. The results of some of these papers' phylogenetic studies have been reproduced below:

McCall 2023: Majority-rule (50%) consensus

Anomalocarididae Anomalocaris canadensis Anomalocaris aff.canadensis Anomalocaris daleyae Innovatiocaris Anomalocaris magnabasis Amplectobeluidae Laminacaris sp. Guanshancaris Laminacaris chimera Ramskoeldia Radiodont C Innovatiocaris? sp. Innovatiocaris? multispiniformis "Anomalocaris" sp. (Balang) Parker Slate Radiodont Houcaris consimilis? Houcaris consimilis Houcaris saron Amplectobelua aff. trispinata Amplectobelua trispinata Lyrarapax unguispinus Amplectobelua stephenensis Lyrarapax trilobus

Zheng 2022: Parsimony-Implied weights (K=3)

Radiodonta Hurdiidae Innovatiocaris Anomalocaris kunmingensis Laminacaris Radiodont C 'Anomalocarididae' Anomalocaris canadensis Anomalocaris aff. canadensis Ramskoeldia Tamisiocarididae Amplectobeluidae

Wu et al. (2024) recovered Shucaris as a radiodont of uncertain relation—often as a member of the Anomalocarididae—in their phylogenetic analyses. Their results are shown below:

Topology A: Parsimony-Equal weights

Anomalocarididae Shucaris Amplectobeluidae Anomalocaris spp. Paranomalocaris spp. Ramskoeldia Lenisicaris spp.

Topology B: Parsimony-Implied weights (K=3) & Topology C: Parsimony-Implied weights (K=7)

Anomalocarididae Shucaris Anomalocaris spp. Ramskoeldia Lenisicaris pennsylvanica Lenisicaris lupaata Caryosyntrips Paranomalocaris spp.

Despite this however, Wu et al., (2024) discuss novel features Shucaris possesses such as "more podomeres in the claw region than all amplectobeluids and most anomalocaridids", leading them to recover Shucaris as "the most basal taxon within Anomalocarididae or a sister taxon to the clade comprising amplectobeluids and anomalocaridids".

Paleobiology

Shucaris had an abnormally small oral cone, suggesting that it likely chewed up prey with its gnathobase-like structures and then swallowed it. This implies that it had a similar diet to amplectobeluids, with both being nektobenthic predators consuming hard-shelled prey.