Looking deceptively like a fish, Kerreralepis is an extinct genus of jawless fish (agnathan) that lived during the Lochkovian Stage of the Early Devonian, approximately 419.2 to 410.8 million years ago.
But looks can be deceiving – it’s not a fish like we know them but a Birkeniiforme anaspid, a unique group of early vertebrates that diverged early in the vertebrate lineage, specifically along the Cyclostome lineage, more closely related to weirdo hagfishes and lampreys than modern-day fish.
A recent discovery, Kerreralepis is notable for its small size and body fins 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 Kerreralepis’ taxonomic order. We can’t place it in a specific family group yet.
Kerreralepis Taxonomy and Classification
- Domain: Eukaryota
- Kingdom: Animalia (Metazoa)
- Subkingdom: Eumetazoa
- Infrakingdom: Bilateria
- Superphylum: Deuterostomia
- Phylum: Chordata
- Subphylum: Vertebrata
- Evolutionary Lineage: Stem-cyclostome (Cyclostomiformes)
- Class: Anaspida
- Order: Birkeniiformes
- Family: Unknown
- Genus: Kerreralepis
- Species: Kerreralepis carinata
Geological Time and Habitat
- Period: Devonian
- Stratigraphic Range: Early Devonian, Lochkovian Stage (approximately 419.2 to 410.8 million years ago)
- Habitat: Kerreralepis lived in shallow, nutrient-rich marine environments, likely near the coastal regions of ancient Scotland. These waters provided an ideal habitat for early vertebrates like Kerreralepis, which used its elongated body and fin structures to navigate efficiently through these ancient seas.
Evolutionary Significance
As a member of the Anaspida, Kerreralepis belongs to a group of jawless fishes that diverged early in the vertebrate evolutionary tree.
Anaspids are unique in that they belong to the Cyclostome lineage, making them more closely related to modern hagfish and lampreys than other jawless vertebrates on the gnathostome lineage.
Unlike many other early vertebrates, Kerreralepis lacks the bony armour that many Agnathans (jawless fishes) developed.
Instead, its body is covered in scales, but these scales are not homologous to the bony scales of gnathostome-line vertebrates. Neither are Kerreralepis’s hypocercal tail and body fins – they are a separate development from the true fins in other fish.
Physical Characteristics
Kerreralepis was a small vertebrate jawless fish (agnathan), measuring about 5 cm in length.
Its body was fish-like, covered with a distinctive scale pattern, and lacked the paired fins typical of many early vertebrates.
Kerreralepis Synapomorphies
As a vertebrate, Kerreralepis shared several fundamental features with other early vertebrates:
- Vertebral Column: Kerreralepis possessed bony or cartilaginous vertebrae around the ancestral notochord and nerve cord, forming the backbone or spine.
- Neurocranium: A cartilaginous or bony brain casing protected its brain.
- Tri-partite Brain: Like other vertebrates, it has a brain divided into three distinct lobes: olfactory (smell), optic (sight), and otic (hearing).
Specific to anaspida, Kerreralepis also exhibited:
- Hypocercal Tail: The bones of the vertebrae extended into the bottom of the tail, while the fin structure made up the top of the caudal fin.
- Body Fins: Unbroken single fins running along its body, distinct from the paired fins found in gnathostome vertebrates.
Intriguing Mysteries Around Kerreralepis
A significant gap in the fossil record marks anaspids like Kerreralepis.
See, molecular clock data suggests that anaspids diverged very early in vertebrate history along the Cyclostome lineage, possibly during the Cambrian, yet their fossils only start to appear in the Silurian.
That’s an embarrassing 100 million-year gap.
And leads us to wonder if we’re just not recognising early anaspids, if they lived in places they didn’t fossilise or if their fossils are still out there somewhere, waiting to be found.
Discovery & Classification
- Discovery Date: 2012
- Discovery Location: Island of Kerrera, Scotland
- Discovering Paleontologist(s): Henning Blom
- Naming: The genus name Kerreralepis is derived from “Kerrera,” the island where the fossils were found, and “lepis,” the Greek word for scale.
Known Species of Kerreralepis
The only known species within this genus is Kerreralepis carinata, named for the keel-like structure of its preanal plates.
Behaviour and Ecology
Kerreralepis was likely a filter feeder or scavenger, relying on its gill structures to extract food particles from the nutrient-rich waters it inhabited.
Its small, elongated body, coupled with its unique fin structures, made it an agile swimmer, well-adapted to its shallow marine environment.
The hypocercal tail of Kerreralepis would have provided stability and manoeuvrability, allowing it to navigate effectively in the coastal waters of Devonian Scotland.
Fossil Discoveries
The fossil of Kerreralepis was discovered on the island of Kerrera in Scotland, within deposits dating to the Early Devonian.
The fossil is well-preserved, showcasing the body structure, scale pattern, and fin configuration of this early vertebrate.
This discovery provides crucial insights into the anatomy and evolution of anaspids.
Scientific Research and Theories
Henning Blom’s 2012 study, published in Palaeontology, described the Kerreralepis genus, focusing on its unique features within the Birkeniiformes order.
The research explored the evolutionary implications of this new genus, particularly in relation to the early divergence of anaspids and their placement within the Cyclostome lineage.
Current Specimen Locations
While it is unclear exactly where the fossil specimens of Kerreralepis are housed, they are referenced in the Paleobiology Database. Scottish institutions may also hold the physical specimens.
Another Curios Aspect of Kerreralepis
Despite being a jawless vertebrate, Kerreralepis and other anaspids possess a fish-like appearance, with elongated bodies and fin structures that seem to have evolved independently and are not homologous to the true fins of jawed fishes.
This convergence in form makes anaspids such as Kerreralepis 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 Kerreralepis, 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 Devonian genera, is a fascinating example of convergent evolution.
Extinction Theories
The extinction of Kerreralepis and other anaspids likely resulted from environmental changes during the Devonian.
Rising sea levels, shifts in marine ecosystems, and increased competition from more advanced vertebrates may have driven anaspids to extinction.
Interesting Facts & Trivia
- Kerreralepis carinata was named for its keel-like preanal plates, a unique feature among anaspids.
- Despite its fish-like appearance, Kerreralepis is more closely related to modern hagfish and lampreys than to true fish.
- The discovery of Kerreralepis helps fill a gap in the fossil record of early vertebrates, offering insight into the Cyclostome lineage’s evolutionary path.
Additional Resources & References of Kerreralepis
- Blom, H. (2012). New Birkeniid anaspid from the Lower Devonian of Scotland and its phylogenetic implications. Palaeontology, 55(3), 641–652.
Discover More Cool Anaspids
Kerreralepis is of an unknown family in the Devonian, much like its Silurian cousin Cowielepis. 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.
Being from Scotland, it shares its discovery locations with the likes of Trimpleylepis and the super freaky Jamoytius.
And, being Devonian, Kerreralepis lived alongside anaspids like Endeiolepis, Vilkitskilepis and Euphanerops.
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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