Cordaticaris

Cordaticaris[lower-alpha 1] (heart-shaped shrimp) is a genus of extinct hurdiid radiodont (stem-group arthropod) that lived in what is now northern China during the middle Cambrian period (Miaolingian, Drumian). This animal was described in 2020 based off remains found in the Zhangxia Formation, located in the Shandong Province.[1] It is differentiated from other members of its family by its unique heart-shaped frontal sclerite (head carapace), and its frontal appendages bearing nine endites and seven more elongated subequal endites.[1] This animal was important as it was the first Miaolingian aged hurdiid known from rock layers outside of laurentia, allowing paleontologists to get a better grasp of this families geographic range in life.[1]

Cordaticaris
Temporal range:
Diagram of the head sclerites of C. striatus
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Class: †Dinocaridida
Order: †Radiodonta
Family: †Hurdiidae
Genus: †Cordaticaris
Sun, 2020
Type species
Cordaticaris striatus
Sun, 2020

Hurdiids like Cordaticaris were the most diverse lineage of radiodonts, both in terms of geographic distribution, and ecological roles. They are differentiated from other radiodont groups by their large head sclerites, their tetraradial mouth-parts, and their appendages bearing around five subequal endites.[2] The diversity of hurdiid head sclerites is notable, with some genera like Aegirocassis and Hurdia possessing long, pointed sclerites.[3][4] While others like Cambroraster and Titanokorys possessed horseshoe-shaped sclerites.[5][6]

Description
Diagram of the oral cone (mouth) of C. striatus

This radiodont is known from a number of specimens, (NIGPAS 173109–173117, 173313), that allow us to get a general sense of its anatomy. The oral cone of the animal (which was a circular shaped mouth that sat underneath the head), was made up of around 32 plates, and was similar in appearance to that of the one possessed by Peyotia. The head sclerite was around 96mm long, and around 93mm wide at its largest. The sclerite bore a spiked end at the front as well as posterolateral notches. The lateral areas of the sclerite were lobate in appearance, and were covered in ornaments like tubercles. The frontal appendages (long grasping appendages at the front of the radiodonts head) consisted of around 9 podomeres, which each bore long overlapping endites. These endites then bore around 20 or so long auxiliary spines, which were shaped like needles.[1]

Classification

The features present in Cordaticaris (cephalic carapace, elongated endites, and the oral cone shape) align it with the hurdiids.[1] In 2022 when describing new remains of the basal hurdiid Stanleycaris, Moysiuk and Caron assigned Cordaticaris to a derived position within the hurdiid family alongside Cambroraster and Titanokorys.[7]

Phylogentic position of Cordaticaris in relation to other radiodonts
Radiodonta

Tamisiocarididae

Anomalocarididae

Amplectobeluidae

Hurdiidae

Stanleycaris

Schinderhannes

Peytoia

Aegirocassis

Hurdia

Pahvantia

Cambroraster

Titanokorys

Cordaticaris

Phylogenetic position of Cordaticaris after Moysiuk & Caron 2022.[8]

Paleoecology
Life restoration of the Linyi Lagerstätte, with Cordaticaris in the upper left corner.

Cordaticaris fossils are known from a site called the Linyi Lagerstätte, which sits above the Panchegou Member within the larger Zhangxia Formation. The site is known for its soft bodied preservation, with some of the arthropod taxa known showing preserved digestive systems. According to the 2022 paper that analyzed the site, there are "35 fossil taxa, including four trilobites, one agnostoid, at least nine soft-bodied arthropods, two lophophorates, at least seven sponges, one chancelloriid, one priapulid, seven problematica, four macroalgae and four trace fossils".[9] There are at least two genera of radiodonts known, Cordaticaris (which is the most abundant non-trilobite arthropod at the site), and a currently unnamed amplectobeluid known from several frontal appendages.[9]

Notes
  1. From Latin cordatus for "heart-shaped", and "caris" for "shrimp"

References
  1. Sun, Zhixin; Zeng, Han; Zhao, Fangchen (2020-08-01). "A new middle Cambrian radiodont from North China: Implications for morphological disparity and spatial distribution of hurdiids". Palaeogeography, Palaeoclimatology, Palaeoecology. 558: 109947. Bibcode:2020PPP...558j9947S. doi:10.1016/j.palaeo.2020.109947. ISSN 0031-0182. S2CID 224868404.
  2. Pates S, Lerosey-Aubril R, Daley AC, Kier C, Bonino E, Ortega-Hernández J. 2021. The diverse radiodont fauna from the Marjum Formation of Utah, USA (Cambrian: Drumian) PeerJ 9:e10509 https://doi.org/10.7717/peerj.10509
  3. Van Roy, Peter (12 March 2015). "Fossils of huge plankton-eating sea creature shine light on early arthropod evolution". The Conversation. Retrieved 16 March 2015.
  4. Daley, Allison C.; Budd, Graham E.; Caron, Jean-Bernard (October 2013). "Morphology and systematics of the anomalocaridid arthropod Hurdia from the Middle Cambrian of British Columbia and Utah". Journal of Systematic Palaeontology. 11 (7): 743–787. doi:10.1080/14772019.2012.732723. ISSN 1477-2019. S2CID 86465719.
  5. Moysiuk, J.; Caron, J.-B. (31 July 2019). "A new hurdiid radiodont from the Burgess Shale evinces the exploitation of Cambrian infaunal food sources". Proceedings of the Royal Society B: Biological Sciences. 286 (1908): 20191079. doi:10.1098/rspb.2019.1079. PMC 6710600. PMID 31362637.
  6. Caron, J.-B.; Moysiuk, J. (2021). "A giant nektobenthic radiodont from the Burgess Shale and the significance of hurdiid carapace diversity". Royal Society Open Science. 8 (9): 210664. Bibcode:2021RSOS....810664C. doi:10.1098/rsos.210664. PMC 8424305. PMID 34527273.
  7. Moysiuk, Joseph; Caron, Jean-Bernard (8 July 2022). "A three-eyed radiodont with fossilized neuroanatomy informs the origin of the arthropod head and segmentation". Current Biology. 32 (15): 3302–3316.e2. doi:10.1016/j.cub.2022.06.027. ISSN 0960-9822. PMID 35809569. S2CID 250361698.
  8. Moysiuk, Joseph; Caron, Jean-Bernard (8 July 2022). "A three-eyed radiodont with fossilized neuroanatomy informs the origin of the arthropod head and segmentation". Current Biology. 32 (15): 3302–3316.e2. doi:10.1016/j.cub.2022.06.027. ISSN 0960-9822. PMID 35809569. S2CID 250361698.
  9. Sun, Z.; Zhao, F.; Zeng, H.; Luo, C.; Van Iten, H.; Zhu, M. (2022). "The middle Cambrian Linyi Lagerstätte from the North China Craton: a new window on the Cambrian evolutionary fauna". National Science Review. 9 (7): nwac069. doi:10.1093/nsr/nwac069. PMC 9273334. PMID 35832778. Retrieved 2 April 2023.
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