Extremely fish-like, spiny-backed and a very recent Scottish discovery. Cowielepis is an extinct genus of jawless fish (agnathan) that lived during the Wenlockian portion of the Silurian period, approximately 433 to 427 million years ago.
It’s a Birkeniiforme anaspid, a unique group of early vertebrates that diverged early in the vertebrate lineage, specifically along the Cyclostome lineage, which, despite its fishy appearance, isn’t really closely related to modern-day fish, but instead to jawless fishes like modern hagfishes and lampreys.
Cowielepis is notable for its small size and distinctive median fins along parts of its body that are completely different from the fin structures of true gnathostome-line fishes and suspected spines along its back.
And, unlike more anaspids, we only know Cowielepis’ taxonomic order. We can’t place it in a specific family group yet.
Cowielepis Taxonomy and Classification
- Domain: Eukaryota
- Kingdom: Animalia (Metazoa)
- Subkingdom: Eumetazoa
- Infrakingdom: Bilateria
- Superphylum: Deuterostomia
- Phylum: Chordata
- Subphylum: Vertebrata
- Evolutionary Sig: stem-cyclostome (cyclostomiformes)
- Class: anaspida
- Order: Birkeniiformes
- Family: Unkown
- Genus: Cowielepis
Geological Time and Habitat
- Period: Silurian
- Stratigraphic Range: Wenlock (approximately 433-427 million years ago)
- Habitat: Cowielepis inhabited shallow marine environments, like those found in coastal regions of ancient Scotland. These waters were rich in nutrients, supporting a variety of early vertebrates. Cowielepis likely adapted well to these conditions, swimming through the waters using its elongated body and fin structures for stability.
Evolutionary Significance
As a member of the anaspida, Cowielepis belongs to a group of jawless fishes (agnathans) significant for their early divergence within the vertebrate evolutionary tree. Anaspids, including Cowielepis, are part of the Cyclostome lineage, which makes them closer relatives of modern hagfishes and lampreys than other jawless vertebrates on the gnathostome lineage (which eventually gave rise to jawed vertebrates).
What sets Cowielepis apart from other early vertebrates is its lack of paired fins – an absence that was typical for anaspids. Instead, it possessed small, median fins along its body, a feature that likely evolved independently from the paired fins found in other vertebrates.
This highlights the unique evolutionary path that anaspids took, with their fin structures developing differently from other early fishes.
Physical Characteristics
Cowielepis was a small jawless fish, estimated to be around 10-15 cm in length.
Its body was more robust and very fish-like, and like other anaspids, it lacked paired pectoral or pelvic fins, a feature that sets it apart from many other early vertebrates.
Instead, Cowielepis had a series of small, median fins along its body, which likely helped it stabilise while swimming – although these body fins were entirely their own thing, not homologous to gnathostome fish fins we know today at all.
Its tail was hypocercal, meaning the vertebrae extended into the lower lobe of the tail, while a fin formed the upper part of the caudal fin.
Cowielepis Synapomorphies
Cowielepis inherited all the normal vertebrate features, including a vertebral column: bony or cartilaginous vertebrae around the ancestral notochord and nerve chord to make up the backbone or spine; a neurocranium: cartilaginous or bone brain casing/skull; tri-partite brain: a brain with 3 distinct lobes: Olfactory (smell), Optic (sights) and Otic (hearing).
And then on top of those, it developed completely unique Anaspid features:
- Hypocercal Tail: where the bones of the vertebral go down into the bottom of the tail, with a fin structure making up the top of the caudal.
- Body fins and unbroken single fin-like structures that are not homologous and seem to be a completely independent evolution from the fins of fish we know today – in fact, most modern Cyclostomes do not have fins at all.
Intriguing Mysteries Around Cowielepis
One of the intriguing aspects of Cowielepis and other anaspids is the gap in the fossil record. They should be around for almost 100 million years before we actually see them in the fossil record.
See, although molecular clock data suggests that anaspids were among the first vertebrates to diverge from the common vertebrate ancestor, which means they should have been around since the Cambrian 541 and 485.4 million years ago, their fossils only start to appear in the Silurian period – that’s an embarrassing 100 million-year gap we just can’t account for.
In fact, anaspids are more primitive than even conodonts, who are definitely around in the Cambrian. So the questions remain: Did anaspids simply live in places they didn’t fossilise? Have we simply not found them yet? Or is there something wrong with our understanding of where vertebrates came from?
Cowielepis helps fill part of the evolutionary picture, but the mystery of their earlier history remains.
Discovery & Classification
- Discovery Date: 2008
- Discovery Location: Cowie Harbour fish bed, Stonehaven, Scotland
- Discovering Paleontologist(s): Henning Blom
- Naming: The genus name Cowielepis is a combination of “Cowie,” referring to Cowie Harbour where the fossils were found, and “lepis,” Greek for “scale.”
Known Species of Cowielepis
The only known species within this genus is Cowielepis ritchiei, which was named in honour of Dr Albert C. Ritchie, a Scottish palaeontologist who contributed significantly to the study of these fossils.
Behaviour and Ecology
Like other anaspids, Cowielepis likely had a lifestyle adapted to a filter-feeding or scavenging role in the nutrient-rich waters of the Silurian period. Its fish-like body and the presence of median fins suggest that it was a relatively agile swimmer, navigating its environment efficiently despite the absence of paired pectoral and pelvic fins.
The unique tail structure of Cowielepis, with its hypocercal design, would have been critical for stability and manoeuvrability in the water.
As a jawless fish, Cowielepis would have relied on its gill structures to filter food particles from the water or scavenge for small organisms.
Its presence in fossil beds alongside other early vertebrates indicates that it was part of a diverse marine ecosystem.
Fossil Discoveries
A fossil of Cowielepis was, as far as we know, only discovered once and in one location: Cowie Harbour fish bed in Stonehaven, Scotland.
The fossil deposits around this area are part of the Wenlock epoch, dating back approximately 433-427 million years.
And the specific Cowielepis fossil is an exquisite full-body fossil, showing us nearly the entire creature’s body structure in phenomenal detail.
Scientific Research and Theories
Cowielepis has been the subject of scientific study, most notably by Henning Blom, who described a new anaspid species from the Cowie Harbour fish bed in 2008. Blom’s research, published in the Journal of Vertebrate Paleontology, examined the morphology and phylogeny of Cowielepis within the broader context of anaspid evolution.
Although Cowielepis could definitely be placed within the anaspid order of Birkeniiformes, its taxonomic family remains a mystery.
Current Specimen Collection Locations
It’s unclear where the physical specimen is kept, yet the data exists in:
- The Paleobiology Database
Another Curios Aspect of Cowielepis
Despite being a jawless vertebrate, Cowielepis and other anaspids possess a fish-like appearance, with elongated bodies and fin structures. However, these features evolved independently and are not homologous to the true fins of jawed fishes. This convergence in form makes anaspids such as Cowielepis particularly interesting, as they provide insight into the varied evolutionary strategies of early vertebrates.
While modern cyclostomes like lampreys and hagfishes have eel-like bodies, some anaspids, including Cowielepis, exhibit more fish-like characteristics. This resemblance is deceptive, as the underlying structures of anaspids are quite different from true fishes. The evolutionary trajectory of anaspids, from the fish-like forms of the Silurian to the more eel-like forms of later genera, is a fascinating example of convergent evolution.
Extinction Theories
The extinction of Cowielepis and other anaspids likely coincided with environmental changes at the end of the Silurian period. Changes in sea levels, shifts in marine ecosystems, and the emergence of more competitive vertebrates may have contributed to the decline of anaspids. The exact causes of their extinction remain speculative, but the fossil record shows that Cowielepis and its relatives did not survive into the later periods when jawed vertebrates began to dominate.
Interesting Facts & Trivia
- Cowielepis ritchiei was named in honour of Dr Albert C. Ritchie, a Scottish palaeontologist who played a significant role in studying the fossils from Cowie Harbour.
- The fish bed at Cowie Harbour, Scotland, where Cowielepis was discovered, is a well-known site for early vertebrate fossils.
- The discovery of Cowielepis provides insight into the early evolutionary history of jawless vertebrates, particularly those on the Cyclostome lineage.
Additional Resources & References of Cowielepis
Blom, H. (2008). A new anaspid fish from the middle Silurian Cowie Harbour fish bed of Stonehaven, Scotland. Journal of Vertebrate Paleontology, 28(3), 594–600.
Discover More Cool Anaspids
Cowielepis is of an unknown family in the Silurian, much like its Devonian cousin Kerreralepis. But we do know that they both are part of the Birkeniiformes order of anaspids alongside the likes of Rytidolepis, Birkenia, Pharyngolepis, Pterygolepis and Lasanius.
It’s also closely related to Rhyncholepis, the genus that famously replaced Anaspis – for whom the clade was named – and its close relative, Rytidolepis.
Being from Scotland, it shares its discovery locations with the likes of Trimpleylepis and the super freaky Jamoytius.
Museums with Anaspid Collections & Exhibits
- The on-site museum at Miguasha in Canada
- Swedish Museum of Natural History
- Hunterian Museum and Art Gallery at the University of Glasgow
- Natural History Museum Denmark
- Grant Museum of Zoology, London
- The Royal Ontario Museum, Canada
- American Museum of Natural History
- University of California Museum of Paleontology
Documentaries Featuring Early Jawless Vertebrates Similar to Anaspida like Cowielepis
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
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. Life on Our Planet Episode 2
2023
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.
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. 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!
5. 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.
6. 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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