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Extinct genus of jawless fishes From Wikipedia, the free encyclopedia
Zhongjianichthys rostratus[a] is an extinct species basal chordate that lived in the Cambrian Period, approximately 518 million years ago, in what is now Southwest China. It is sometimes regarded as an early fish, and therefore as one of the first vertebrates in the global fossil record.
| Zhongjianichthys Temporal range: Cambrian Stage 3, | |
|---|---|
| |
| Artist's reconstruction | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Order: | †Myllokunmingiida |
| Family: | †Myllokunmingiidae |
| Genus: | †Zhongjianichthys Shu, 2003 |
| Species: | †Z. rostratus |
| Binomial name | |
| †Zhongjianichthys rostratus Shu, 2003[2] | |
The genus name, Zhongjianichthys, is named after paleontologist Yang Zhongjian (1897-1979), who was widely honored as the "Father of Chinese Vertebrate Paleontology".
The eyes of Zhongjianichthys 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, unlike Myllokunmingia, which also lived in the Cambrian, no impressions of its myomeres have been found. The ventral fin is low in height, and runs much of the body's length.[3]
Although Zhonjianichthys appears more advanced than its relatives due to the back-positioned eyes and the thicker skin, this may be a case of convergent 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 Cambrian Maotianshan shales of China.[3] The shales contain many zones of Konservat Lagerstatten which have aided in the preservation of this animal's soft body.
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