Caryosyntrips serratus (ROM 57161) – Holotype, part and counterpart. Individual claw. Specimen length = 78 mm. Specimen dry – direct light (top row), dry – polarized light (bottom row). Walcott Quarry.
© Royal Ontario Museum. Photo: Jean-Bernard Caron
Caryosyntrips was initially assigned to Radiodonta (Daley and Budd 2010), the group that includes Anomalocaris (Collins 1996), as the hardened appendages of these animals are typically the only remains that preserve. However, phylogenetic analyses (Vinther et al. 2014; Lerosey-Aubril and Pates 2018; Moysiuk and Caron 2021) have failed to resolve its precise relationship with radiodontans and a placement outside of this group remains possible.
Caryosyntrips – from the Greek karyon meaning “nut,” and syntrips, a mythical fiend who smashed pottery; thus, a nut smasher, referring to the nutcracker-like morphology of the paired appendages
serratus – from the Latin serratus, “saw-edged.”
Burgess Shale and vicinity: none
Other deposits: C. camurus from the Spence Shale Member of the Langston Formation and C. durus from the Wheeler Formation of Utah, U.S.A. A specimen identified as C. cf. camurus has also been recovered from the Valdemiedes Formation of Spain (Pates & Daley, 2017, but see Pates et al., 2018; Zhuravlev & Gámez Vintaned, 2018).
The Walcott and Raymond Quarries on Fossil Ridge. Also known from the Tulip Beds (S7) on Mount Stephen.
The Burgess Shale material was first noticed and illustrated as “Dinocarida A” in Caron (2005)), and formally designated as Caryosyntrips serratus by Daley and Budd (2010). Pates and Daley (2017) later revised the taxonomy and described new occurrences of the genus outside of the Burgess Shale.
This species is known from eleven isolated appendages from the Burgess Shale. Appendages are elongate and triangular in outline, with a length that ranges between 58 mm and 114 mm. Segmentation of the appendage is weakly developed due to partial fusion, but 14 podomeres (segments) can be distinguished. Each appendage is straight and rigid, with no movement occurring at the podomere boundaries. Each podomere has one thick, short spine on the inner margin, and several smaller spines on the outer margin, giving the latter a serrated appearance. The distal end of the appendage tapers to a point, and a single terminal spine is slightly curved. Most appendages are isolated, but a single paired specimen shows that the appendages were oriented with their thick spines in opposition. This particular specimen is loosely associated with other potential unidentifiable remains of the body of the animal.
Carysyntrips serratus is extremely rare. Most specimens (8) come from the Walcott Quarry.
Caryosyntrips serratus is assumed to have had a similar mode of life to other radiodontans, meaning that it swam through the water column actively searching out prey. It has been suggested to have fed by moving the rigid appendages at their bases, bringing their medial spinous margins together in a scissor-like motion (Daley and Budd 2010). While some other radiodontans like Stanleycaris may have shared this general mode of functioning (Moysiuk and Caron 2021), the particularly rigid appendages of Caryosyntrips are uniquely specialized, arguing that this species was adapted to hard-shelled prey (Pates and Daley 2017).
None