| Zhongjianichthys | |
|---|---|
 | |
| Fossil | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Infraphylum: | Agnatha |
| Order: | †Myllokunmingiida |
| Family: | †Myllokunmingiidae |
| Genus: | †Zhongjianichthys Shu, 2003 |
| Species: | †Z. rostratus |
| Binomial name | |
| †Zhongjianichthys rostratus Shu, 2003[2] | |
Zhongjianichthys rostratus[a] is an extinct species basalchordate that lived in theCambrian Period, approximately 518 million years ago, in what is nowSouthwest China. It is sometimes regarded as an early fish, and therefore as one of the first vertebrates in the globalfossil record.
The genus name,Zhongjianichthys, is named after paleontologistYang Zhongjian (1897-1979), who was widely honored as the "Father of Chinese Vertebrate Paleontology".
The eyes ofZhongjianichthys are located behind an antero-dorsal lobe of the head, and the mouth apparently did not have a jaw. It also lacked scales and had a thick skin. In fact, it is known to have had a thicker skin than other early chordates because, unlikeMyllokunmingia, which also lived in the Cambrian, no impressions of itsmyomeres have been found. The ventral fin is low in height, and runs much of the body's length.[3]
AlthoughZhonjianichthys appears more advanced than its relatives due to the back-positioned eyes and the thicker skin, this may be a case ofconvergent evolution and it may not, therefore, be particularly closely related to the ancestors of modern chordates.
Zhongjianichthys' reduced fins may indicate that it was mainly bottom-dwelling and did not swim much. This could have been a factor in the evolution of its comparatively thicker skin, as protection from predators which may have lurked on or near the sea floor.[3]
Zhongjianichthys specimens have been found in the early CambrianMaotianshan shales of China.[3] The shales contain many zones ofKonservat Lagerstatten which have aided in the preservation of this animal's soft body.