Zhongjianichthys

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, 518 Ma[1] PreꞒ Ꞓ O S D C P T J K Pg N ↓
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".

Physical characteristics

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.

Paleoecology

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]

Locations

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.

Notes

1. Rostratus means beak-like in latin

References

1. Yang, C.; Li, X.-H.; Zhu, M.; Condon, D. J.; Chen, J. (2018). "Geochronological constraint on the Cambrian Chengjiang biota, South China" (PDF). Journal of the Geological Society. 175 (4): 659–666. Bibcode:2018JGSoc.175..659Y. doi:10.1144/jgs2017-103. ISSN 0016-7649. S2CID 135091168.
2. Shu, Degan (2003). "A paleontological perspective of vertebrate origin". Chinese Science Bulletin. 48 (8): 725–735. Bibcode:2003ChSBu..48..725S. doi:10.1007/BF03187041. S2CID 85163902.
3. "Palaeos Vertebrates : Vertebrata : Craniata". palaeos.com. Retrieved 2018-02-04.