''Caryosyntrips'' ("

nutcracker A nutcracker is a tool designed to open nuts by cracking their shells. There are many designs, including levers, screws, and ratchets. The lever version is also used for cracking lobster and crab shells. A decorative version, a nutcracker doll ...

") is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of stem-

arthropod Arthropods ( ) are invertebrates in the phylum Arthropoda. They possess an arthropod exoskeleton, exoskeleton with a cuticle made of chitin, often Mineralization (biology), mineralised with calcium carbonate, a body with differentiated (Metam ...

which known from Canada, United States and Spain during the middle

Cambrian The Cambrian ( ) is the first geological period of the Paleozoic Era, and the Phanerozoic Eon. The Cambrian lasted 51.95 million years from the end of the preceding Ediacaran period 538.8 Ma (million years ago) to the beginning of the Ordov ...

. It was first named by Allison C. Daley and Graham E. Budd in

2010 The year saw a multitude of natural and environmental disasters such as the 2010 Haiti earthquake, the Deepwater Horizon oil spill, and the 2010 Chile earthquake. The 2009 swine flu pandemic, swine flu pandemic which began the previous year ...

, being the type species ''Caryosyntrips serratus''.

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 The Wheeler Shale (named by Charles Walcott) is a Cambrian ( 507 Ma) fossil locality world-famous for prolific agnostid and ''Elrathia kingii'' trilobite remains (even though many areas are barren of fossils) and represents a Konzent ...

and

Marjum Formation The Marjum Formation is a Cambrian geological formation that overlies the Wheeler Shale in the House Range, Utah. It is named after its type locality, Marjum Pass, and was defined in 1908. The formation is known for its occasional preservation of ...

, United States, and

Valdemiedes Formation The Mesones Group is a Cambrian geologic group in Spain. It preserves numerous soft-bodied and hard-shelled taxa such as echinoderms and trilobites. It is often stated to contain the Mansilla, Murero and Valdemiedes Formations, however just as of ...

, Spain. The latter contain a large specimen, which was initially misidentified as a body remain of

lobopodian Lobopodians are members of the informal group Lobopodia (), or the formally erected phylum Lobopoda Cavalier-Smith (1998). They are panarthropods with stubby legs called lobopods, a term which may also be used as a common name of this group as w ...

("''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 Durophagy is the eating behavior of animals that consume hard-shelled or exoskeleton-bearing organisms, such as corals, shelled mollusks, or crabs. It is mostly used to describe fish, but is also used when describing reptiles, including fossil t ...

, feeding on hard-shelled organisms. Other structures remain unknown, although a specimen with paired appendages possibly contain other fragmental head sclerites as well. The size of ''Caryosyntrips'' differed between each species. The largest species is ''C. serratus'' which is estimated around long. Other species are much smaller, with the body lengths of ''C. camurus'' and ''C. durus'' estimated up to and respectively. The largest possible specimen (MPZ 2009/1241), identified as ''C.'' cf. ''camurus'', would have belonged to an individual measuring between long.

Taxonomic affinities

As of 2010s, ''Caryosyntrips'' was long considered to be a basal

radiodont Radiodonta is an extinct order of stem-group arthropods that was successful worldwide during the Cambrian period. Radiodonts are distinguished by their distinctive frontal appendages, which are morphologically diverse and were used for a variety ...

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

External links