Myllokunmingia is an extinct genus of primitive jawless fish that lived during the Cambrian period, approximately 518 million years ago, in what is now the Yunnan Province of China. It was discovered alongside Haikouichthys, another genus of primitive jawless fish, in 1999 and is considered to be among the earliest known vertebrate animals in the fossil record. The holotype of the type species, Myllokunmingia fengjiaoa — and the only uncontroversial specimen thereof — was found in the Yuanshan member of the Qiongzhusi Formation in the Eoredlichia Zone near Haikou at Ercaicun, Kunming City, Yunnan, China.

Description

The holotype is 28 mm long and 6 mm high. The animal has a distinct head and body with a forward, sail-like (1.5 mm) dorsal fin and a ventral fin fold further back (probably paired). The head has five or six gill pouches with hemibranchs. In the body, there are 25 muscle segments (myomeres) with rearward-facing, double-V-shaped chevrons. There is a notochord, a pharynx and a digestive tract that may run all the way to the rear tip of the animal. A mouth cannot be clearly identified. There may be a pericardial cavity. There are no fin radials. The tip of the tail in the holotype is buried in sediment. However, subsequent studies led by the British paleontologist Simon Conway Morris identified both genera to be distinct on the basis of different gill arrangement, the absence of branchial rays in Myllokunmingia and the myomeres having a more acute shape in Haikouichthys.

Nevertheless, Hou et al. in 2017 in their book, The Cambrian Fossils of Chengjiang, China, suggested that specimens referred to Myllokunmingia, Haikouichthys and Zhongjianichthys may be taphonomic variants (i.e., of the same animal but in different states of decay) and due to what they argue to be the lack of certainty in the reliability of the distinguishing characters between the three taxa, they follow the opinion of Hou et al., 2002, and use Myllokunmingia for all of them.

See also

  • Zhongjianichthys
  • Yunnanozoon
  • Pikaia
  • Metaspriggina
  • Nuucichthys
  • Emmonsaspis

References

  • http://www.sciencenews.org/sn_arc99/11_6_99/fob1.htm
  • https://web.archive.org/web/20030511135309/http://www.gs-rc.org/repo/repoe.htm
  • Lower Cambrian vertebrates from south China
  • Oldest fossil fish caught

la:Myllokunmingia fengjiaoa