Vesikulepis is an extinct genus of anaspid, a jawless fish (agnathan) that lived during the Homerian to Ludfordian stages of the Silurian Period, approximately 430.5 to 423.0 million years ago.
The genus name Vesikulepis is derived from the Latin “vesicula,” meaning “small sac” or “blister,” combined with “lepis,” meaning “scale,” a reference to its distinct scale pattern.
Although only fragmentary fossils have been discovered, Vesikulepis offers valuable insights into the diversity of early vertebrates within the Birkeniiformes order.
Vesikulepis Taxonomy and Classification
- Domain: Eukaryota
- Kingdom: Animalia (Metazoa)
- Subkingdom: Eumetazoa
- Infrakingdom: Bilateria
- Phylum: Chordata
- Subphylum: Vertebrata
- Evolutionary Lineage: Stem-cyclostome (Cyclostomiformes)
- Class: Anaspida
- Order: Birkeniiformes
- Family: Rhyncholepididae
- Genus: Vesikulepis
- Species: Vesikulepis funiforma
Geological Time and Habitat
- Period: Silurian
- Stratigraphic Range: Homerian Stage (Wenlockian Series) to Ludfordian Stage of the Silurian Period (approximately 430.5–423.0 million years ago)
- Habitat: Vesikulepis seems to have inhabited shallow marine environments rich in nutrients, likely around modern-day Saaremaa Island, Estonia. These early seas supported diverse vertebrate life, and Vesikulepis would have been a part of this ancient ecosystem, swimming with its distinctive elongated body.
Evolutionary Significance
Vesikulepis belongs to the Anaspida, a group of jawless fishes that diverged early in vertebrate evolution along the Cyclostome lineage. This evolutionary path places it closer to modern hagfish and lampreys, distinct from other jawless fish on the gnathostome (jawed) line.
Unlike many early vertebrates, Vesikulepis and other anaspids did not evolve bony armour. Instead, they feature unique scale patterns and convergent fin-like structures that highlight their unique evolutionary strategy.
Physical Characteristics
While the fossils of Vesikulepis remain fragmentary, it is estimated to have been around 10–15 cm in length, with an elongated body covered by a distinctive scale pattern. The species name funiforma, meaning “rope-like shape” in Latin, may refer to its elongated, cylindrical body shape.
The scales on discovered specimens resemble blisters or sac-like structures, a feature that set Vesikulepis apart from other early vertebrates.
Vesikulepis Synapomorphies
As a vertebrate, Vesikulepis shared core features common to other early vertebrates:
- Vertebral Column: Bony or cartilaginous vertebrae surrounding 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, Vesikulepis had a brain divided into three distinct lobes: olfactory (smell), optic (sight), and otic (hearing).
Specific to Anaspida, Vesikulepis also exhibited:
- Hypocercal Tail: The vertebrae extended into the lower lobe of the tail, while the fin structure made up the upper part of the caudal fin.
- Body Fins: While fragmentary fossils leave many details about the fins of Vesikulepis speculative, other anaspids displayed unbroken fins running along the entire body, distinct from the paired fins seen in later gnathostomes.
Intriguing Mysteries Around Vesikulepis
Vesikulepis, like many other anaspids, raises questions about the evolution of early vertebrates.
Its unique scale pattern, described as sac-like, offers insight into the diversity of scale development among early jawless fishes.
Moreover, the fossil record of anaspids, including Vesikulepis, leaves a 100-million-year gap between their likely molecular origins (calculated to be in the Cambrian) and their appearance in the fossil record: the Silurian.
There’s a 100 million years where anaspids should have been around, we just can’t find the evidence – suggesting that their ancestors may have lived in environments that did not favour fossilisation or that we can’t identify or have simply not yet discovered their earlier remains.
Discovery & Classification
- Discovery Date: 2002
- Discovery Location: Saaremaa Island, Estonia
- Discovering Paleontologist(s): Henning Blom, Tiiu Märss, and Carl Miller
- Naming: The genus name Vesikulepis is derived from the Latin “vesicula,” meaning “small sac” or “blister,” and “lepis,” meaning “scale.”
Known Species of Vesikulepis
The only known species within the genus is Vesikulepis funiforma. The species name funiforma refers to its “rope-like” body shape, highlighting its elongated form.
Behaviour and Ecology
While little is known about the specific behaviour of Vesikulepis, it likely played a role similar to other anaspids in its ecosystem, acting as a filter feeder or scavenger. Its elongated body, small fins, and hypocercal tail would have made it an efficient swimmer, well-suited to the shallow, nutrient-rich seas of the Silurian Period.
Fossil Discoveries
The fossils of Vesikulepis were discovered on Saaremaa Island, Estonia, within deposits dating from the Homerian to Ludfordian stages of the Silurian Period. These fossils are fragmentary, with their distinct scale pattern providing much of the anatomical data available.
Scientific Research and Theories
Key studies of Vesikulepis include work by Fadel et al. (2015) on the geochemistry of the fossil beds where its remains were found. This research helped to reveal the environmental conditions of the Silurian seas in which Vesikulepis lived. Additionally, Blom et al. (2002) studied the broader evolutionary implications of birkeniid anaspids in the Northern Hemisphere, including Vesikulepis.
Current Specimen Locations
Specimens of Vesikulepis are housed in notable collections, including:
- TalTech fossil collections
- Natural History Museum (London) Collection Specimens
Another Curious Aspect of Vesikulepis
One intriguing aspect of Vesikulepis is its unique scale structure, which earned it the name referencing small sacs or blisters. This feature sets Vesikulepis apart from other early vertebrates, offering an example of the diversity in scale patterns among early anaspids.
Its elongated form and sac-like scales also raise questions about its role in the ecosystem, perhaps serving as a camouflage or a hydrodynamic aid in swimming through ancient Silurian seas.
Extinction Theories
As with other anaspids, Vesikulepis likely faced extinction due to environmental changes during the Silurian Period. Shifts in sea levels and ecosystems, as well as competition from more advanced vertebrates, may have contributed to the decline of Vesikulepis and its relatives.
Interesting Facts & Trivia
- Vesikulepis funiforma was named for its elongated, rope-like body shape, a distinct characteristic among early anaspids.
- The genus name Vesikulepis highlights its unique sac-like scale pattern, a feature that distinguishes it from other anaspids.
- The discovery of Vesikulepis adds to the diversity of Silurian vertebrates found on Saaremaa Island, Estonia.
Additional Resources & References of Vesikulepis
- Fadel, A., Žigaite, Ž., Blom, H., Perez-Huerta, A., Jeffries, T., Märss, T., Ahlberg, P. E. (2015). Palaeoenvironmental signatures revealed from rare earth element (REE) compositions of vertebrate microremains of the Vesiku Bone Bed (Homerian, Wenlock), Saaremaa Island, Estonia. Estonian Journal of Earth Sciences, 64(1), 36-41. DOI: 10.3176/earth.2015.07
- Blom, H., Märss, T., Miller, C. G. (2002). Silurian and earliest Devonian birkeniid anaspids from the Northern Hemisphere. Transactions of the Royal Society of Edinburgh Earth Sciences, 92(3), 263-323. DOI: 10.1017/S0263593300000250
Discover More Cool Anaspids
Vesikulepis is part of the Birkeniiformes order of anaspids alongside the likes of Rhyncholepis, Birkenia, Pharyngolepis, Pterygolepis and Lasanius, etc.
Specifically, it’s part of the Rhyncholepididae family, along with more fragmentary genera like Rytidolepis, Schidiosteus, Vesikulepis, Silmalepis and Maurylepis that are basically only known from their scales and small fragments.
They might even be cousins of other fragmentary specimens, such as the Tahulalepididae, namely: Tahulalepis and Trimpleylepis.
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 Anaspida, Related to Rytidolepis
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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