''Syncaris pasadenae'' is an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

species of freshwater

shrimp Shrimp are crustaceans (a form of shellfish) with elongated bodies and a primarily swimming mode of locomotion – most commonly Caridea and Dendrobranchiata of the decapod order, although some crustaceans outside of this order are refer ...

in the family

Atyidae Atyidae is a family of shrimp, present in all tropical and most temperate waters of the world. Adults of this family are almost always confined to fresh water. This is the only family in the superfamily Atyoidea. Genera and species The follow ...

. It lived in the

drainage basin A drainage basin is an area of land where all flowing surface water converges to a single point, such as a river mouth, or flows into another body of water, such as a lake or ocean. A basin is separated from adjacent basins by a perimeter, t ...

of the

Los Angeles River , name_etymology = , image = File:Los Angeles River from Fletcher Drive Bridge 2019.jpg , image_caption = L.A. River from Fletcher Drive Bridge , image_size = 300 , map = LARmap.jpg , map_size ...

, near

Pasadena Pasadena ( ) is a city in Los Angeles County, California, northeast of downtown Los Angeles. It is the most populous city and the primary cultural center of the San Gabriel Valley. Old Pasadena is the city's original commercial district. Its ...

, San Gabriel and

Warm Creek Warm, WARM, or Warmth may refer to: * A somewhat high temperature * Kindness Music * ''Warm'' (The Lettermen album), 1967, and the title song * ''Warm'' (Johnny Mathis album), 1958, and the title song * ''Warm'' (Herb Alpert album), 1969 * ' ...

, and was originally described from material collected near where the Rose Bowl now stands. A reference to "freshwater shrimps" in a tributary of the

Santa Ana River The Santa Ana River is the largest river entirely within Southern California in the United States. It rises in the San Bernardino Mountains and flows for most of its length through San Bernardino and Riverside Counties, before cutting through ...

from 1927 may also refer to ''S. pasadenae.'' At the time it was described, in 1897, it was noted as "common" in the streams where it was found. Its habitat was destroyed by channelization of streams and none of the streams where this species was once found remain in a natural state. It has not been seen alive since 1933, despite extensive searching, and is the only

recent The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene together ...

species of shrimp known to have gone extinct. Due to its extinction prior to detailed study, little is known of the natural history of this species. However, based on collected specimens, it seems likely that this species had a winter breeding season, as does its closest relative, ''

Syncaris pacifica ''Syncaris pacifica'' is an endangered species of freshwater shrimp in the family Atyidae that occurs only in a limited range within the northern San Francisco Bay Area, California, USA. Specifically, this species occurs only in 17 stre ...

''. Breeding in the winter is likely an adaptation to the annual precipitation cycle of the area, which results in the freshwater streams where this species occurred nearly drying up in the summer, making summer a disadvantageous time for reproduction.

References

{{Taxonbar, from=Q3935211 Atyidae Freshwater crustaceans of North America Extinct animals of the United States Endemic fauna of California Extinct invertebrates since 1500 Species made extinct by human activities Extinct crustaceans Crustaceans described in 1897 Taxonomy articles created by Polbot