Backbones, jaws and skulls. Vertebrates like us are characterised by internal skeletons, especially the vertebral column. But it wasn’t always bone – when the first vertebrates appeared in the Cambrian and Ordovician, much of their skeletons were cartilage; some still are today.
But make no mistake, the creatures of Vertebrata would dominate the seas, crawl up onto land (and sometimes even go back to the ocean in spectacular fashion) and become some of the most beloved prehistoric and living beasts we know.
Not to mention that some of the strangest early vertebrates are our ancestors.
Here’s the amazing story of prehistoric vertebrates…
About Vertebrates
Vertebrata Class & Scientific Classification
Domain: Eukaryota
Kingdom: Animalia (Metazoa)
Subkingdom: Eumetazoa
Infrakingdom: Bilateria
Superphylum: Deuterostomia
Phylum: Chordata
Subphylum: Vertebrata
Vertebrata is the crown group of all vertebrate animals, meaning it’s the lineage of all living and extinct true vertebrate animals that’s closely related to but still separate from the earlier stem vertebrates.
A Phylogeny of Early Vertebrates
Phylogenetic analysis shows that the first crown-group vertebrates must have appeared in the Cambrian and immediately split into two clades represented by modern, living species: Cyclostomes and Gnathostomes. We know this because we have Cambrian Cyclostome fossils, even though fossils of Gnathostomes (jawed vertebrate-line fossils don’t show up until the Ordovician, they are distinctly different.
Most of the big vertebrates we know and love (including us humans) are on the Gnathostome line.
True Vertebrate Time-Frame: When they Appear on Earth
Using phylogeny, we have to assume that all vertebrates must have originated from a shared common ancestor at the start of the Cambrian because we have fossils of actual vertebrates in the Cambrian.
Conodonts are cyclostome vertebrates, and the first family of Proconodonts appears at the very end of the Cambrian with Eoconodontus Notchpeakensis whose fossils are found between 489.5–485.4 million years ago (Miller et al. 2015).
That goes right up to the Ordovician boundary, when the next Conodont, Iapetognathus Fluctivagus appears. But some people contend Conodonts appear even earlier in the Cambrian – it’s hotly debated as Conodonts are used as index fossils in biostratigraphy.
Unique Vertebrate Body Features
You might be surprised to learn that scientists distinguish vertebrates from non-vertebrates by only 3 body features – the vertebrae, braincase and three-part brain.
Characteristics (Synapomorphies) of Vertebrates
All vertebrates inherited the chordate features of a notochord, dorsal nerve chord and post-anal tail, plus uniquely vertebrate anatomical characteristics:
- Vertebral column: Bony or cartilaginous vertebrae around the ancestral notochord and nerve chord to make up the backbone or spine.
- Neurocranium: Cartilaginous or bone brain casing/skull.
- Tri-Patrite brain: A brain with 3 distinct lobes: Olfactory (smell), Optic (sights) and Otic (hearing).
What are Vertebrates Exactly?
Vertebrates are all living and extinct members of the crown group Vertebrata within the kingdom of Animalia. They are distinguished from invertebrates by their backbone or spinal column, a skeletal structure that houses and protects the spinal cord, a key part of the nervous system.
This group encompasses a wide array of life forms, ranging from the smallest fish to lizards, reptiles, the mightiest dinosaurs that once roamed the Earth, and even mammals like us humans.
The presence of a vertebral column, alongside other physiological features such as a highly developed brain and an internal skeleton, sets vertebrates apart from other organisms in the animal kingdom (Holland et al. 1994).
Are humans vertebrates?
Yes, humans are vertebrates. We belong to the class Mammalia, which developed out of Synapsida, a form of Amniote, which falls under the crown group Vertebrata, under the phylum Chordata.
Like all vertebrates, humans possess a backbone that’s part of an internal skeleton, providing support and protection for the spinal cord while also serving as an anchor for muscles, facilitating movement and flexibility.
This structural feature is integral to our development, posture, and locomotion, just as it is in our evolutionary cousins – fish, reptiles and amphibians.
What Were the First Vertebrates on Earth?
It all started with fish-like creatures in the ocean. The very first vertebrate ancestors were Cambrian stem vertebrates like Haikouichthys and Myllokunmingia from 518 million years ago, and later Metaspriggina from 508 million years ago.
The first true crown group vertebrates we have fossils of are Conodonts – starting with Eoconodontus Notchpeakensis from 489.5–485.4 million years ago in the Cambrian, with members of this group stretching all the way to the Triassic period – and jawless fishes (sometimes erroneously referred to as “agnathans”) of the Ordovician, Silurian and Devonian.
Most of the vertebrates we think of when we think backboned animals, though, are Gnathostomes – vertebrates with jaws like T Rex and us.
5 Classes of Vertebrates
Vertebrates are extremely diverse today – so many animals we know have backbones, way too many to list all of them here. So let’s look at the major vertebrate groups throughout time instead…
1. All Fish
Vertebrate evolution starts with fish. Everything you would consider a fish, including Cyclostomes (“circle-mouth” fishes) like the living lineages of lampreys and hagfishes as well as the stem cyclostomes (Conodonts and Anaspida) and all Gnathostomes (jawed fishes).
That means, from those amazing Placoderms (armoured fishes) to Acanthodians (spiny sharks) and Chondrichthyans (cartilaginous fishes like sharks and rays) to Osteichthys (bony fish), including Sarcopterygii (lobe-finned fish like lungfishes, coelacanths and the Tetrapodomorphs which would crawl onto land [see Tetrapods below] and become us land vertebrates), as well as the very early jawless stem gnathostomes such as Heterostracomorphi, Arandaspida, Thelodonti, Galeaspida and Osteostraci, all fish are vertebrates.
2. Tetrapods & Amphibians
When bony fish (Tetrapodamorphs specifically) develop lungs and limbs that enable them to leave the water and crawl onto land, they bring their vertebrate traits with them, becoming Tetrapods – the first vertebrates to live on land.
This includes the Batramorpha line that gives rise to Temnospyndils, the lineage that would lead to Lissamphibia – today’s amphibians (frogs, salamanders and caecilians) and their extinct relatives (Eyrops etc.). But it also includes the Reptilomorpha line, which eventually leads to all amniotes.
3. All Amniotes
Amniotes (creatures who do not have to lay their eggs in water anymore) are also all vertebrates. And this lineage very early on splits into two very distinct lines:
- The Synapsids, which eventually lead to mammals
- And the Diapsids, which eventually lead to lizards and reptiles.
4. The Diapsids (Reptilia)
Diverging from Synapsids just before the Carboniferous, the Total Reptilia group includes Parareptiles and the crown group of Sauria (reptiles) that diverges into Lepidosaurs (lizards and snakes) and Archosaurs – the group that would give rise to crocodiles, turtles, dinosaurs and birds.
5. Synapsids
Starting with all the “Pelycosaurs” like Dimetrodon in the Carboniferous and Permian and eventually leading to Therapsids and those glorious Gorgonopsians, this lineage eventually leads to Cynodonts, who give rise to the Mammaliamorpha and eventually all of us mammals. We are all vertebrates.
Fossil Locations: Where Are Vertebrate Fossils Found?
Vertebrate fossils are common in many sites across the world. Here are a few good ones:
- Early fishes: The Royal Ontario Museum in Canada & Chengjiang fossil site in Yunnan Province, China.
- Placoderms: Gogo Formation, Australia.
- Early Sarcopterygii (Lobe-finned Fishes): Canowindra, Australia & Miguasha National Park, Canada.
- Tetrapodomorphs & Tetrapods: Elgin, Scotland & Valentia Island, Ireland.
- Amniotes: Joggins Fossil Cliffs, Canada.
- Permian Pelycosaurs: Red Beds of Texas, USA.
- Permian Reptiles and Synapsids: Karoo Basin, South Africa.
- Dinosaurs: Morrison Formation, USA, Gobi Desert, Mongolia & Jehol Biota, China
- Cenozoic Mammals: La Brea Tar Pits, USA & Messel Pit, Germany
Museum Fossils: Where Can You Go to See Early Vertebrate 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, as well as some spectacular vertebrates for yourself…
Early Fishes: Royal Ontario Museum, Canada
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.
Placoderms, Tetrapodomorphs & Dinosaurs: National History Museum, London
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.
Early Sarcopterygii (Lobe-finned Fishes): Museum of Natural History (Muséum d’Histoire naturelle), Paris, France
Part of 14 sites across France, the Muséum d’Histoire Naturelle was founded during the French Revolution (1790s) and features four main galleries with some spectacular fossils of all types, including early Placoderms and Sarcopterygian fishes.
Amniotes & Dinosaurs: Field Museum, Chicago, US
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.
Permian Pelycosaurs: American Museum of Natural History, New York, US
Situated on the Upper West Side of Manhattan, right across from Central Park, this museum is made up of several interconnected buildings, featuring nearly 45 permanent exhibition halls.
Dinosaurs: Royal Tyrrell Museum of Palaeontology, Alberta, Canada
One of the most famous dinosaur museums in the world, the Royal Tyrrell Museum is situated in Drumheller, right by Dinosaur Provincial Park and houses hundreds of thousands of fossil specimens – hundreds of whom are the original holotype of the species/genus.
Documentaries Featuring some Awesome Early 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. Ancient Oceans
2019
See the full video here.
Not just about vertebrates, but featuring some of the most awesome ancient fishes. This short documentary about early oceans and extinction events has two episodes and is available through Curiosity Stream here.
2. Australia: A Time Traveller’s Guide Episode 2
Richard Smith, 2012
Though not specifically focused on vertebrates, Episode 2 of the charming Australia: A Time Traveller’s Guide (Australia’s First 4 Billion Years) is all about tracking the continent’s record of animals’ invasion of land. Starting off with features of early vertebrate fish Arandaspis to later placoderms and reefs of the Devonian, as well as invertebrate tracks on land in the Silurian.
You can also find it on AppleTV here.
3. Animal Armageddon Episode 2
Animal Planet, 2019
It’s hard to track down a good copy of this one, but Animal Armageddon features quite a few vertebrate evolutionary stories, pegged on the major mass extinctions they faced. This one specifically is during the Devonian, the age of fishes (vertebrates).
Also available on Amazon here.
4. Miracle Planet HD, Episode 3
NHK (Japan) & KCTS (Canada), 1989
Even the remake is now dated, but still lays a great scientific foundation. This episode follows the evolution of fish and the eventual move onto land – featuring none other than Jenny Clack herself. (Before the discovery of Tiktaalik.)
Available on Amazon here.
5. Your Inner Fish
PBS, 2014
Tracking the story of Neil Shubin and team who discovered loads of transitional vertebrate forms, including the famous tetrapodomorph, Tiktaalik.
Watch on PBS here or Amazon here.
6. Life on Our Planet Episode 2
Though not focused on vertebrates specifically, episode 2 of Steven Spielberg’s Netflix documentary, narrated by Morgan Freeman, features a look at early life and the land transition, featuring some vertebrates like Sacabambaspis.
Watch on Netflix here.
7. Mankind Rising
2012
The 2012 TV movie production of Mankind Rising is a single animated journey from the earliest vertebrates ancestors right through to present-day humans – it’s pretty cool, maybe a bit dated, but still a lot of fun!
8. Walking with Monsters
BBC, 2005
A bit older now and flashing past early animals a bit too quickly, this one in the “Walking With” series is still pretty cool for its Cambrian bits. It’s also available via Amazon.
10. 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.
About PrehistoricLife.co
I aim to have everything as up-to-date as possible and will continually update this post. Please notify me of any necessary updates, information you think should be included, and references or citations needed.
Enjoy the journey of discovery through Earth’s ancient past, geology, big ideas and, of course, awesome prehistoric life.
