Caryosyntrips

Etymology

The scientific name Caryosyntrips comes from Greek karyon, "nut"; and syntrips, "the smasher", a spirit from Greek mythology.

Occurrence

Multiple species had been recovered from the Burgess Shale Formation, Canada, Wheeler Shale and Marjum Formation, United States, and Valdemiedes Formation, Spain. The latter contains a large specimen, which was initially misidentified as a body remain of lobopodian ("Mureropodia apae"). While the assignment of "Mureropodia" as a misidentified appendage was controversial, the previous lobopodian affinity was less tenable than the fossil being a Caryosyntrips appendage.

Description

File:Pates & Daley 2017 f03.png|Fossil frontal appendages of C. serratus File:Pates & Daley 2017 f04.png|Fossil frontal appendages of C. camurus File:Pates & Daley 2017 f05.png|Fossil frontal appendages of C. durus File:Pates & Daley 2017 f06.png|Fossil frontal appendage of C. cf. camurus (=Mureropodia apae) File:Mureropodia apae - Xenusia - Lower Cambrian - Murero, Spain.jpg|Digitally enhanced image of C. cf. camarus (=Mureropodia apae) File:20210702 Caryosyntrips camurus frontal appendage mobility.gif|Presumed grasping motion of C. camurus File:20210215 Caryosyntrips size.png|Sizes of various Caryosyntrips specimens, based on the interpretation as radiodonts.

Caryosyntrips is known only from its 14-segmented frontal appendages, which resemble nutcrackers, with the endite (ventral spine)-bearing margin facing each other, and the bell-shaped bases might represent movable articulations with the animal's head. Details of the endites, terminal spines, segmental boundaries and outer margins differ between species. It is thought to have used their frontal appendages in a scissor-like grasping or slicing motion, and were probably durophagous, feeding on hard-shelled organisms. Other structures remain unknown, although a specimen with paired appendages possibly contains fragmentary head sclerites as well.

The size of Caryosyntrips differed between each species. The largest species is C. serratus which is estimated around 20.5 - long. Other species are much smaller, with the body lengths of C. camurus and C. durus estimated up to 13.7 - and 12.2 - respectively. The largest possible specimen (MPZ 2009/1241), identified as C. cf. camurus, would have belonged to an individual measuring between 36.7 - long.

Taxonomic affinities

As of 2010s, Caryosyntrips was long considered to be a basal radiodont of uncertain position, usually resolved in a polytomy between euarthropod and radiodont branches. however more recent papers have found that it may sit outside of the monophyletic Radiodonta all together. Due to the unusual morphology of the frontal appendages and the limited extent of known remains, its position within the arthropod stem-group remains uncertain.

References

References

1. (2017). "''Caryosyntrips'': a radiodontan from the Cambrian of Spain, USA and Canada". Papers in Palaeontology.
2. Allison C. Daley, Graham E. Budd. (2010). "New anomalocaridid appendages from the Burgess Shale, Canada". Palaeontology.
3. (2021-01-19). "The diverse radiodont fauna from the Marjum Formation of Utah, USA (Cambrian: Drumian)". PeerJ.
4. (2011). "A New Early Cambrian Lobopod-Bearing Animal (Murero, Spain) and the Problem of the Ecdysozoan Early Diversification". Springer.
5. (2018). "Response to Comment on "Aysheaia prolata from the Utah Wheeler Formation (Drumian, Cambrian) is a frontal appendage of the radiodontan Stanleycaris" with the formal description of Stanleycaris". Acta Palaeontologica Polonica.
6. (2018). "Comment on "''Aysheaia prolata'' from the Utah Wheeler Formation (Drumian, Cambrian) is a frontal appendage of the radiodontan ''Stanleycaris''" by Stephen Pates, Allison C. Daley, and Javier Ortega-Hernández". Acta Palaeontologica Polonica.
7. (2018-09-14). "New suspension-feeding radiodont suggests evolution of microplanktivory in Cambrian macronekton". Nature Communications.
8. (2018-09-14). "New suspension-feeding radiodont suggests evolution of microplanktivory in Cambrian macronekton". Nature Communications.
9. Jakob Vinther. (2014). "A suspension-feeding anomalocarid from the Early Cambrian". Nature.
10. (September 2014). "Brain structure resolves the segmental affinity of anomalocaridid appendages". Nature.
11. (June 2015). "Anomalocaridid trunk limb homology revealed by a giant filter-feeder with paired flaps". Nature.
12. (2018-06-01). "Origin of raptorial feeding in juvenile euarthropods revealed by a Cambrian radiodontan". National Science Review.
13. (2019-08-14). "A new hurdiid radiodont from the Burgess Shale evinces the exploitation of Cambrian infaunal food sources". Proceedings of the Royal Society B: Biological Sciences.
14. (13 December 2023). "A large pelagic lobopodian from the Cambrian Pioche Shale of Nevada". Journal of Paleontology.