Thicker skin, smaller body and lobe-like head extensions. Chinese Cambrian stem vertebrate Zhongjianichthys is an enigmatic member of the prehistoric Myllokunmingiidae family – a close relative of Haikouichthys.
But so little is known of Zhongjianichthys itself. What was it? How did it live? What did it look like, and what can it teach us about the early evolution of vertebrates?
About Zhongjianichthys
Zhongjianichthys Class & Scientific Classification
Domain: Eukaryota
Kingdom: Animalia (Metazoa)
Subkingdom: Eumetazoa
Infrakingdom: Bilateria
Superphylum: Deuterostomia
Phylum: Chordata
Paleo Classification: Stem Vertebrate
Order: †Myllokunmingiida
Family: †Myllokunmingiidae
Genus: †Zhongjianichthys
Species: †Zhongjianichthys Rostratus (Z. rostratus)
Zhongjianichthys Rostratus is part of the Myllokunmingiidae family, a group that diverged from chordates right before the emergence of crown-group vertebrates.
A Phylogeny of Early Chordate-Vertebrate Divergence
Zhongjianichthys Time-Frame: When it Appears on Earth
The stem vertebrate Zhongjianichthys Rostratus, along with other members of the Myllokunmingiidae family, seems to appear in the fossil record during the Middle Cambrian around 518 million years ago.
However, it’s hard to verify since the original publication occurred in China and the fossil itself does not seem to be publicly available. It was found in south China, likely in Yunnan Province, first described by Shu et al. in 2003.
Zhongjianichthys Size Comparison with a Human Diver
Zhongjianichthys Characteristics (Synapomorphies)
Zhongjianichthys shares many traits with its Cambrian cousins, Haikouichthys and Myllokunmingia, including:
- Vertebral elements that hint at the possible evolution of cartilaginous structures around the notochord.
- Possible lobe-like extensions in the head, with potential eyes and cavities that could be interpreted as nasal and otic (hearing) function, which is the possible development of a primitive tri-partite brain.
- Like all members of the Myllokunmingiidae family, Zhongjianichthys seems to have a clearly defined skull, albeit likely cartilaginous.
However, Zhongjianichthys also appears to have had thicker skin than its closer relatives as well as a lobe-like projection from the head (which some say resembles a big nose) and a reduced ventral fin along the bottom of its body all the way to the tail.
Stem vertebrate Zhongjianichthys was small at a mere 1.1cm in length. A trait it shares with all members of the Myllokunmingiidae family.
What is Zhongjianichthys?
Zhongjianichthys Rostratus is an enigmatic stem vertebrate from the Middle Cambrian discovered in China, that’s its own genus and species but forms part of the Myllokunmingiidae family, which features the much better known, at least in Western countries, Haikouichthys and Myllokunmingia.
Like its relatives, Zhongjianichthys was a small, 1.1cm worm/eel-like creature with fins, gills, myomeres and a notochord or a chordate, but also the beginnings of vertebral elements, lobe-like brain structures and skull elements of a vertebrate.
It’s therefore considered a transitionary form from chordates to vertebrates, a.k.a. A stem vertebrate. However, note that it’s hard to get visual confirmation of Zhongjianichthys’ features since it was originally published in China and the information is hard to come by in Western countries.
When and Where Was it First Found?
It’s hard to say with absolute certainty when and where Zhongjianichthys was found precisely, due to the Chinese publication and lack of fossil image evidence in English literature (many citations and references lead to non-existent publications).
Yet it is mentioned and potentially first described by noted Chinese Cambrian biota specialist Dr Degan Shu, who is generally extremely rigorous and trustworthy.
That said, Zhongjianichthys was most likely also found alongside its better-known Myllokunmingiidae relatives, in China’s Yunnan Province, possibly also in Middle Cambrian rock layers of around 518 million years ago.
What are Zhongjianichthys’s Closest Relatives?
Zhongjianichthys is its own genus and species, but it falls into the Myllokunmingiidae family, meaning it’s a relative to some of the biggest stem-vertebrate celebrities of the Cambrian:
1. Haikouichthys
Haikouichthys is an extinct genus of Cambrian chordate and a stem vertebrate of the Myllokunmingiidae family, often heralded as one of the earliest known vertebrates from China, some 518 million years ago.
What’s exceptionally interesting about Haikouichthys is that it lived 518 million years ago, 13 million years BEFORE the first chordate fossil we know of, Pikaia. This is absolutely fascinating because it would mean that there must have been more chordates long before Pikaia, we just haven’t found them yet.
Not to mention that scientists found over 500 fossil specimens of Haikouichthys, allowing us to much better study and determine its place in the chordate-vertebrate diversion. Discover the evolutionary giant, Haikouichthys.
2. Myllokunmingia
Myllokunmingia Fengjiaoa is a species of extinct stem vertebrates, a classification it shares with all members of the Myllokunmingiidae family, from the Middle Cambrian period, around 517 million years ago. It was found in the Chengjiang assemblages of Yunnan, China in 1999.
Its fossils average only 2.8cm in size and it shows no evidence of biomineralisation, so it had no actual bones, yet its cartilaginous structures show that it is a transitional form between early chordates, such as Pikaia, to true vertebrates.
Discover more of Myllokunmingia.
Is Zhongjianichthys The Ancestor of All Vertebrates?
Not exactly. It’s better understood as a near relative of the ancestral lineage that would eventually give rise to all subsequent vertebrates, humans included.
Zhongjianichthys’s position within the evolutionary tree aids in bridging the gaps in our understanding, showcasing the gradual developments in chordates that led to the sophisticated diversity of vertebrate life.
Fossil Locations: Where Are Cambrian Fossils Like Zhongjianichthys Found?
- Zhongjianichthys itself is only known from the Chengjiang fossil locations in China
- Yet other Cambrian sites include the Burgess Shale in British Columbia, Canada
- The Wheeler Shale in the House Range of western Utah, USA
- The Sirius Passet site in North Greenland is another critical location for understanding Cambrian life.
Museum Fossils: Where can you Go to See Early Chordate and other Cambrian Fossils?
If you live nearby or can make the trip, there are a few great places to go and see some of the first animals and eumetazoans, including bilaterians, protostomes, deuterostomes and chordates, for yourself…
1. Chengjiang Fossil Site Natural History Museum
Being in China, it’s a bit hard to track down English info. But the Chinese government says there is a Chengjiang Fossil Site Natural History Museum. With over 60’000 fossil specimens at its location in Xincun Road, Chengjiang County, Yuxi City in Yunnan province.
2. The Burgess Shale
Did you know you can actually go to the Burgess Shale fossil sites in the Canadian Rockies yourself? You can book a guided hike with The Burgess Shale Geoscience Foundation and visit the Walcott quarry, Mt. Stephen – the works.
Phone 1 (250) 343-6006, email info@burgess-shale.bc.ca or visit their website.
3. Royal Ontario Museum
The Royal Ontario Museum in Toronto, Canada is famous for its connection to the world-famous Cambrian site, the Burgess Shale. They have both an amazing fossil collection if you visit in-person or even here online and a cool virtual sea odyssey you can experience online right now.
Phone: 416 586 8000 (Canada) | or visit their website
4. Smithsonian National Museum of Natural History
The Smithsonian has quite a large Cambrian fossil collection. And it’s completely free! So, if you’re ever in Washington DC, it’s one of the coolest places to go check out Cambrian fossils.
5. The Natural History Museum, London, UK
With a rich collection of fossils and exhibitions that trace the history of life on Earth, the London Natural History Museum’s displays on Cambrian and Precambrian life provide context for the evolution of complex organisms.
Phone +44 (0)20 7942 5000 or visit their website.
6. Field Museum of Natural History, Chicago, USA
Boasting a broad collection of fossils and active in paleontological research, its Evolving Planet exhibition takes visitors through the history of life on Earth, including the Cambrian time.
Phone +1 312 922 9410 or visit their website.
Documentaries Featuring some of the First Chordates & Vertebrates
They’re not always 100% accurate because we make new scientific discoveries all the time. But documentaries at least deliver the gist of the information in a fun and engaging way. Just click play, hit full screen and enjoy hours’ worth of awesome documentaries on first animals, right here…
1. Mankind Rising
2012
This one’s an absolute must for Myllokunmingia fans (Zhongjianichthys’s cousin) because it starts off, right after the anchornworm-like ancestor, with a fish-like creature called “Milo” or “Myllo”, which stands for Myllokunmingiidae or possibly Myllokunmingia itself.
The 2012 TV movie production of Mankind Rising is a single animated journey from the earliest vertebrate ancestors right through to present-day humans. It’s pretty cool, maybe a bit dated, but still a lot of fun!
2. Walking with Monsters
BBC, 2005
This chapter in the “Walking With” series is an absolute must for Haikouichthys fans, because it’s the main character in the Cambrian segments, facing off against the mighty Anomalocaris. It’s also available via Amazon.
3. David Attenborough’s Rise of Animals: Triumph of the Vertebrates
BBC, 2013
Although more focused on the evolution of vertebrates, it’s still an awesome documentary to watch. It’s available to purchase from Amazon.
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