Though only a few fragmentary remains have been found, we know Ramsaasalepis was an extinct genus of Anaspida, a jawless fish (agnathan) on the Cyclostome lineage of vertebrates that lived during the Silurian Period, approximately 427–419 million years ago.
Discovered in Skåne, South Sweden, Ramsaasalepis is notable for its distinctive scale structure and fin folds, which provide rare insights into the evolutionary diversity of early vertebrates within the Birkeniiformes order (though the genus is in its own family, Ramsaasalepididae).
In this post, we explore where exactly Ramsaasalepis fits on the Tree of Life (taxonomy), when and where it lived (geological context), what makes it scientifically unique (physical traits and synapomorphies), its discovery history, intriguing mysteries, and the role it played in the ecosystem of Silurian seas.
Ramsaasalepis 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: Ramsaasalepididae
- Genus: Ramsaasalepis
- Species: Ramsaasalepis porosa
Geological Time and Habitat
- Period: Silurian
- Stratigraphic Range: From the Ludlow to Pridoli stages of the Silurian Period, approximately 427–419 million years ago.
- Habitat: Ramsaasalepis likely thrived in nutrient-rich, shallow marine environments characteristic of Silurian seas. These habitats supported diverse vertebrate life, and Ramsaasalepis played a key role in this ancient ecosystem alongside other Anaspida and early vertebrates.
Evolutionary Significance
Ramsaasalepis belongs to the class Anaspida, a jawless vertebrate group representing an early evolutionary divergence along the Cyclostome lineage. This evolutionary path places them closer to modern hagfish and lampreys, distinct from other technically jawless fishes in the Gnathostome lineage.
Unlike many of its contemporary early vertebrates, Ramsaasalepis displayed neither bony armour nor the dermal development typical of the other Agnathans on the Gnathostome line. Its detailed scale structure and fin folds underscore its unique evolutionary strategy within the Birkeniiformes order, albeit in its own family, named Ramsaasalepididae.
Physical Characteristics
Although its fossils remain fragmentary, Ramsaasalepis is estimated to have measured 10–15 cm long. Its scale pattern and fin folds distinguish the genus, features that set it apart from related genera like Vesikulepis or Tahulalepis.
Ramsaasalepis Synapomorphies
As a vertebrate, Ramsaasalepis shared several key traits with other early vertebrates, including:
- Vertebral Column: Cartilaginous or bony structures around the notochord and nerve cord, forming a backbone.
- Neurocranium: A cartilaginous or bony braincase.
- Tri-partite Brain: Divided into olfactory, optic, and otic lobes.
Unique Features Specific to Ramsaasalepis:
- Hypocercal Tail: Where the vertebrae extend into the bottom lobe of the tail, supporting a fin on the upper side.
- Fin Folds: Running along its body, these unbroken fins highlight independent body-fin evolution, distinct from the paired fins of Gnathostomes.
Intriguing Mysteries Around Ramsaasalepis
Like other Anaspida, Ramsaasalepis raises profound questions about early vertebrate evolution. Molecular clock data suggests that Anaspids were among the first Cyclostomes to diverge after the emergence of Vertebrates during the Cambrian. Yet their fossil record does not appear until the Silurian — an over 100 million-year gap.
This 100-million-year-long absence suggests there could still be many undiscovered anaspids fossils, or environmental factors did not favour their fossilisation. Either that or, we have to improve our understanding of early vertebrate evolution a little more.
Additionally, the distinct fin folds and scale patterns of Ramsaasalepis offer a unique look into the evolutionary pathways that developed independently of Gnathostomes.
Discovery & Classification
- Discovery Date: 2003
- Discovery Location: Skåne, South Sweden
- Discovering Paleontologists: Henning Blom, Tiiu Märss, and Carl Miller
- Naming: The genus name reflects its unique morphological characteristics and scale patterns, though its etymology remains unpublished.
Known Species of Ramsaasalepis
- Ramsaasalepis porosa: Derived from the Latin porosus, meaning “porous,” likely referring to the texture of its scale structure.
Behaviour and Ecology
While specific behaviours of Ramsaasalepis are speculative due to limited fossil evidence, it likely occupied a similar ecological niche to other Anaspids. These small, jawless fishes may have acted as filter feeders or scavengers in Silurian shallow seas. Their shape and likely fin folds would have helped them swim, enabling them to thrive in nutrient-rich marine environments.
Scientific Research and Theories
Key research into Ramsaasalepis has focused on its evolutionary implications. Studies such as those by Blom et al. (2003) examine the detailed morphology of its scales and fins, situating it within the Cyclostome lineage of vertebrates. This research contributes to a broader understanding of Anaspida diversity and their role in early vertebrate ecosystems.
Current Specimen Locations
Specimens of Ramsaasalepis are housed in research collections at:
- Sweden’s Geological Research Institutions
- Estonian Museum of Natural History
Extinction Theories
Like many Anaspids, Ramsaasalepis likely faced extinction due to environmental shifts during the Silurian Period. Changing sea levels, competition from more advanced vertebrates on the Gnathostome lineage, and evolving ecosystems may have contributed to its decline.
Interesting Facts & Trivia
- The species Ramsaasalepis porosa is named after the Latin “porosus,” meaning “porous,” a reference to its distinctive scale patterns.
- Its fossils provide rare insights into the evolutionary diversity of early Cyclostomes, challenging our understanding of vertebrate morphology.
- Discovered in Sweden, its presence in this region highlights the geographical spread of Silurian marine ecosystems.
Additional Resources & References
- Blom, H., Märss, T., Miller, C. G. (2003). A new birkeniid anaspid from the Upper Silurian of Skåne, south Sweden. GFF, 125(2), 57–61. DOI:10.1080/11035890301252057.
Discover More Cool Anaspids
Trimpleylepis is part of the Birkeniiformes order of anaspids alongside the likes of Rhyncholepis, Birkenia, Pharyngolepis, Pterygolepis and Lasanius, etc.
Specifically, it’s in its own family of Ramsaasalepididae, but is perhaps close to the Birkeniidae family members like Vilkitskilepis, Ctenopleuron, Birkenia and Hoburgilepis.
It might even be closely related to other fragmentary Anaspids from the Silurian, such as the Septentrioniidae, including Liviilepis, Manbrookia, Ruhnulepis, Spokoinolepis and Septentrionia.
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 Ramsaasalepis
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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