Euthycarcinoidea

Kottixerxes gloriosus, copyright RCFossils.

Belongs within: Euarthropoda.

The Euthycarcinoidea are a group of primarily aquatic arthropods known from freshwater or brackish water environments in the Late Ordovician or Early Silurian to the Middle Triassic (Vaccari et al. 2004). Their affinities have been the subject of much interest with some authors suggesting a relationship to modern hexapods.

Characters (from Vaccari et al. 2004): Sphaeroidal processes present at lateral edge of articulation between short anterior cephalic tergite and longer posterior cephalic tergite; mandibles present beneath posterior cephalic tergite, with mandible apparently lacking a palp; trunk divided into pedigerous pre-abdomen and narrow, limbless post-abdomen; multiple wide sternites associated with each pre-abdominal tergite, ratio of sternites per tergite increasing posteriorly with decoupling of tergal and sternal segmentation; antenniform pre-abdominal limbs with short segment; slender curved apodeme originating near each limb base.

Euthycarcinoidea [Archicopepoda, Euthycarcinata]
    |--Sottixeriformes B95
    |    |--Pieckoxerxes piekoae (Schram & Rolfe 1982) WA01
    |    `--Sottyxerxes [Sottyxerxidae] WA01
    |         |--S. multiplex Schram & Rolfe 1982 WA01
    |         `--S. pieckoae Schram & Rolfe 1982 RB93
    `--Euthycarciniformes VEE04
         |--+--Kalbarria brimmellae LSE13, WA01
         |  `--Apankura Vaccari, Edgecombe & Escudero 2004 LSE13, VEE04
         |       `--*A. machu Vaccari, Edgecombe & Escudero 2004 VEE04
         `--Kottixerxidae [Euthycarcinidae] WA01
              |--+--Schramixerxes gerem (Schram & Rolfe 1982) LSE13, WA01
              |  `--Smithixerxes Schram & Rolfe 1982 LSE13, WA01
              |       |--*S. juliarum Schram & Rolfe 1982 WA01
              |       `--S. pustulosus Wilson & Almond 2001 WA01
              `--+--Kottixerxes Schram 1971 LSE13, WA01
                 |    |--*K. gloriosus Schram 1971 WA01
                 |    `--K. anglicus Wilson & Almond 2001 WA01
                 `--+--Heterocrania rhyniensis LSE13, VEE04
                    `--+--Arthrogyrinus Wilson & Almond 2001 LSE13, WA01
                       |    `--*A. platyurus Wilson & Almond 2001 WA01
                       `--+--Synaustrus brookvalensis (Riek 1964) LSE13, WA01
                          `--Euthycarcinus LSE13
                               |--E. ibbenburensis VEE04
                               |--E. kessleri Handlirsch 1914 WA01
                               `--E. martensi G88

*Type species of generic name indicated

REFERENCES

[B95] Bousfield, E. L. 1995. A contribution to the natural classification of Lower and Middle Cambrian arthropods: Food-gathering and feeding mechanisms. Amphipacifica 2: 3–34.

[G88] Gray, J. 1988. Evolution of the freshwater ecosystem: the fossil record. Palaeogeography, Palaeoclimatology, Palaeoecology 62: 1–214.

[LSE13] Legg, D. A., M. D. Sutton & G. D. Edgecombe. 2013. Arthropod fossil data increase congruence of morphological and molecular phylogenies. Nature Communications 4: 2485.

[RB93] Ross, A. J., & D. E. G. Briggs. 1993. Arthropoda (Euthycarcinoidea and Myriapoda). In: Benton, M. J. (ed.) The Fossil Record 2 pp. 357–361. Chapman & Hall: London.

[VEE04] Vaccari, N. E., G. D. Edgecombe & C. Escudero. 2004. Cambrian origins and affinities of an enigmatic fossil group of arthropods. Nature 430: 554–557.

[WA01] Wilson, H. M., & J. E. Almond. 2001. New euthycarcinoids and an enigmatic arthropod from the British coal measures. Palaeontology 44 (1): 143–156.

Last updated: 13 March 2022.