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Caryosyntrips serratus

An anomalocaridid with nutcracker-like appendages

Line drawings of the appendages of the anomalocarids.

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Comparative sketches of anomalocaridid frontal appendages (presumed adult sizes) from the Burgess Shale (modified from Daley and Budd, 2010). A. Anomalocaris canadensis (modified from Briggs, 1979). B. Hurdia victoria appendage morph B (drawn from Daley et al. 2009). C. Hurdia victoria appendage morph A (drawn from Daley et al. 2009). D. Laggania cambria? E. Amplectobelua stephenensis. F. Caryosyntrips serratus. Scale bar = 10 mm.


Media 1 of 3 for Caryosyntrips serratus Drawing
Media 2 of 3 for Caryosyntrips serratus Photo
Media 3 of 3 for Caryosyntrips serratus Photo







Dinocarida (Order: Radiodonta, stem group arthropods)


Caryosyntrips is an anomalocaridid. Anomalocaridids have been variously regarded as basal stem-lineage euarthropods (e.g., Daley et al., 2009), basal members of the arthropod group Chelicerata (e.g., Chen et al., 2004), and as a sister group to the arthropods (e.g., Hou et al., 2006).

Species name:

Caryosyntrips serratus

Described by:

Daley and Budd

Description date:



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.”

Type Specimens:

Holotype –ROM57161 in the Royal Ontario Museum, Toronto, Canada.

Other species:

Burgess Shale and vicinity: none.

Other deposits: none.

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Middle Cambrian, Bathyuriscus-Elrathina Zone (approximately 505 million years ago).

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Principal localities:

The Walcott and Raymond Quarries on Fossil Ridge. Also known from the Tulip Beds (S7) on Mount Stephen.

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History of Research

Brief history of research:

This genus was first noticed and illustrated as “Dinocarida A” in Caron (2005), and formally designated as Carysyntrips serratus by Daley and Budd (2010).

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This taxon is known from eleven specimens of isolated appendages. Appendages are straight and tapering in outline, with a length that ranges between 58 mm and 114 mm. Segmentation of the appendage is poor, but at least 12 podomeres (segments) can be distinguished. The appendage is straight and rigid, with no movement occurring at the podomere boundaries. Each podomere has one thick, short spine on the inner surface, and several smaller spines on the outer surface, giving this outer margin 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 the appendages arranged in close proximity, with their thick spine margins in opposition. This particular specimen is loosely associated with potential remains of the body of the animal in the form of some cuticular elements. However, these elements are poorly preserved and might not be of the same animal.


Carysyntrips serratus is extremely rare. Most specimens (8) come from the Walcott Quarry.

Maximum size:

114 mm

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Life habits:

Nektobenthic, mobile

Feeding strategies:


Ecological Interpretations:

Carysyntrips serratus is assumed to have had a similar mode of life to the rest of the anomalocaridids, meaning that it swam through the water column actively searching out prey. Its predatory nature is inferred from the morphology of the appendages, which were heavily spined. The straight, rigid appendages may have pivoted at their proximal attachment points to bring the thick-spine edges of the pair appendages together in a grasping or slicing motion.

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CARON, J. B. 2005. Taphonomy and community analysis of the Middle Cambrian Greater Phyllopod Bed, Brugess Shale. Unpublished Ph.D. thesis, University of Toronto, Toronto, 316 pp.

CHEN, J. Y. D. WALOSZEK AND A. MAAS. 2004. A new 'great-appendage' arthropod from the Lower Cambrian of China and homology of chelicerate chelicerae and raptorial antero-ventral appendages. Lethaia, 37: 3-20.

DALEY, A. C., G. E. BUDD, J. B. CARON, G. D. EDGECOMBE AND D. COLLINS. 2009. The Burgess Shale anomalocaridid Hurdia and its significance for early euarthropod evolution. Science, 323: 1597-1600.

DALEY, A. C. AND G. E. BUDD. 2010. New anomalocaridid appendage from the Burgess Shale, Canada. Palaeontology, 53: 721-738.

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