Ninetooth pebble crab (Cycloxanthops novemdentatus)

Classification (WoRMS)

Full classification as recorded by WoRMS: Kingdom: Animalia · Phylum: Arthropoda · Class: Malacostraca · Order: Decapoda · Family: Xanthidae · Genus: Cycloxanthops.

Accepted name: Cycloxanthops novemdentatus · Authority: (Lockington, 1877) · Taxonomic status: accepted · AphiaID: 444237.

Synonyms and superseded combinations recorded for this taxon: Cycloxanthops rugosa Holmes, 1900; Cycloxanthus californiensis Rathbun, 1894; Xanthodes novemdentatus Lockington, 1877; Xanthodes novem-dentatus Lockington, 1877.

Source: World Register of Marine Species (WoRMS) — https://www.marinespecies.org/aphia.php?p=taxdetails&id=444237 (CC BY 4.0). Accessed 2026-09-25.

Biology and life history (SeaLifeBase)

Measured values published by SeaLifeBase for Cycloxanthops novemdentatus. Only fields the database actually holds for this species are shown; these are database values, not aquarium guidance.

Habitat zone: benthic.

Source: SeaLifeBase species summary (SpecCode 26841) — https://www.sealifebase.se/summary/Cycloxanthops-novemdentatus.html (CC BY-NC 3.0 — non-commercial use only). Accessed 2026-09-25.

Distribution and occurrence records (GBIF)

531 georeferenced occurrence records for Cycloxanthops novemdentatus are published through GBIF from 3 countries or marine areas. The map above plots 18 distinct locations from a sample of 531 records, omitting 13 inland records that carry an institution's coordinates rather than a collection site; it shows where the species has been observed and reported, not a modelled range.

Most records by country or area: United States of America (514); Mexico (16); Panama (1).

Source: GBIF Occurrence Search (taxonKey 2227862) — https://www.gbif.org/occurrence/search?taxon_key=2227862&has_coordinate=true (records CC0 / CC BY); WoRMS distribution records (MarineRegions) — https://www.marinespecies.org/aphia.php?p=taxdetails&id=444237 (CC BY 4.0); Natural Earth 110m basemap — https://www.naturalearthdata.com/ (public domain). Accessed 2026-09-25.

Description and natural history (Wikipedia)

Cycloxanthops novemdentatus is typically brown or red in color, but can also be purple. Individuals of this species often have dark or light markings on their shell which are still present after molting, however, shell color may change over time. This organism gets its common name from the two sets of anterolateral teeth on the front edge of its carapace, each set consisting of nine teeth. The carapace can reach up to 3.75 inches in width.

Immature individuals can be distinguished from adults by the width of the third and sixth abdominal segments, the length of marginal abdominal hair, a sparse layer of hair on the swimmerets, and the presence of a structure known as a lock mechanism in males. After individuals reach approximately 6.5 mm in carapace width, sexual dimorphism is apparent due to the different size and shape of abdominal segments.

Cycloxanthops novemdentatus is the largest member of the family Xanthidae found in California.

Cycloxanthops novemdentatus can be found in the eastern Pacific Ocean, from Monterey, CA to Baja California, but is most abundant in the southernmost portions of coastal southern California.

Cycloxanthops novemdentatus lives in rocky intertidal and subtidal habitats to a depth of 240 m. Younger crabs are typically found in higher regions of the intertidal than adults.

Cycloxanthops novemdentatus has been observed cracking open and feeding upon purple sea urchins. It is also known to eat other crab species.

When threatened, C. novemdentatus may freeze in place. It is thought that this is an attempt to remain undetected.

Source: Wikipedia: Cycloxanthops novemdentatus — https://en.wikipedia.org/wiki/Cycloxanthops_novemdentatus (CC BY-SA 4.0). Accessed 2026-09-25.