Zhongjianichthys

Zhongjianichthys rostratus[lower-alpha 1] is an extinct basal chordate that lived in the Cambrian period, approximately 518 million years ago. It is sometimes regarded as an early fish, and therefore as one of the first vertebrates. Zhongjianichthys is named after Zhongjian in China.

Zhongjianichthys
Temporal range: Cambrian Stage 3,
Artist's reconstruction
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Infraphylum: Agnatha
Order: †Myllokunmingiida
Family: †Myllokunmingiidae
Genus: †Zhongjianichthys
Shu, 2003
Species:
†Z. rostratus
Binomial name
†Zhongjianichthys rostratus
Shu, 2003[2]

Physical characteristics

The eyes are located behind the antero-dorsal lobe and the mouth apparently did not have a jaw. It lacked scales, and had a thick skin. It is known to have had a thicker skin than other chordates at that time because, unlike Myllokunmingia, 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 convergent evolution and it may not, therefore, be particularly closely related to the ancestors of modern chordates.

Ecology

Zhongjianichthys' reduced fins may indicate that it was mainly bottom-dwelling and did not swim much. This could have been a factor in its evolution of thicker skin, as protection from predators.[3]

Locations

Zhongjianichthys specimens have been found in the early Cambrian Maotianshan shales of China.[3]

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.


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