Eocarcinus

Eocarcinus Temporal range: Pliensbachian PreꞒ Ꞓ O S D C P T J K Pg N
Holotype (top) and paratype (bottom) specimens
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Malacostraca
Order:	Decapoda
Suborder:	Pleocyemata
Infraorder:	Brachyura
Family:	† Eocarcinidae Withers, 1932
Genus:	† Eocarcinus Withers, 1932
Species:	†E. praecursor
Binomial name
†Eocarcinus praecursor Withers, 1932

Reconstruction based on 2020 reanalysis

Additional paratype specimen

Eocarcinus praecursor is a Jurassic species of decapod crustacean, sufficiently distinct from its relatives to be placed in its own family (Eocarcinidae). ^[1] Often considered the oldest true crab, it was considered by a 2010 study to be an early member of the Anomura. However, a reanalysis in 2020 again found it to be the earliest known stem-group crab. ^[2]

Distribution

It lived during the early Pliensbachian age (Lower Jurassic), ^[3] and has been found in rocks at two sites in the United Kingdom – Mickelton Tunnel (near Aston Magna), Gloucestershire and Runswick Bay, Yorkshire. ^[4]

Description

In many of its characters, it represents a transitional stage between the Glypheoidea and the Middle Jurassic crabs in the Prosopidae. ^[3] Since its ancestors were long-tailed decapods, and its successors were short-tailed crabs, Eocarcinus has been described as "the lobster who decided to become a crab". ^[5] Previously considered to be the oldest known true crab, a 2010 revision concluded that Eocarcinus could not be accommodated among the Brachyura, and was instead transferred to the Anomura. ^[6] However, a 2020 reanalysis found that it was again the earliest known stem-group crab, but that it had not undergone the process of carcinisation. ^[2]

References

1. Sammy De Grave; N. Dean Pentcheff; Shane T. Ahyong; et al. (2009). "A classification of living and fossil genera of decapod crustaceans" (PDF). Raffles Bulletin of Zoology . Suppl. 21: 1–109. Archived from the original (PDF) on 2011-06-06.
2. Scholtz, Gerhard (November 2020). "Eocarcinus praecursor Withers, 1932 (Malacostraca, Decapoda, Meiura) is a stem group brachyuran". Arthropod Structure & Development. 59 100991. Bibcode:2020ArtSD..5900991S. doi: 10.1016/j.asd.2020.100991 . PMID   32891896.
3. M. Krobicki; M. Zaton (2008). "Middle and Late Jurassic roots of brachyuran crabs: Palaeoenvironmental distribution during their early evolution". Palaeogeography, Palaeoclimatology, Palaeoecology . 263 (1–2): 30–43. Bibcode:2008PPP...263...30K. doi:10.1016/j.palaeo.2008.01.025.
4. Danièle Guinot; Marcos Tavares (2001). "Une nouvelle famille de Crabes du Crétacé, et la notion de Podotremata Guinot, 1977 (Crustacea, Decapoda, Brachyura)" (PDF). Zoosystema . 23 (3): 507–546.
5. Anonymous (1932). "The Royal Society Conversazione". British Medical Journal . 1 (3724): 946–947. doi:10.1136/bmj.1.3724.944. S2CID   220003084. JSTOR: 1st page, 2nd page
6. Rodney M. Feldmann; Carrie E. Schweitzer (2010). "Is Eocarcinus Withers, 1932, a basal brachyuran?". Journal of Crustacean Biology . 30 (2): 241–250. Bibcode:2010JCBio..30..241S. doi: 10.1651/09-3230.1 .