Lasanius (aka Lasania) is an extinct genus of jawless fish from the Silurian period. Known for its primitive features and streamlined body, Lasanius provides important insights into the early stages of vertebrate evolution.
Taxonomy and Classification
Kingdom: Animalia
Phylum: Chordata
Class: Anaspida
Order: Lasaniiformes
Family: Lasaniidae
Geological Time & Habitat
Geological Time Period: Silurian (approximately 430 million years ago)
Typical Environment: Lasanius inhabited shallow marine environments, likely favouring coastal areas with rich food sources.
Discovery & Classification
Date: Early 20th century
Discovery Location: Scotland
Discovering Paleontologist(s): Sir E. Ray Lankester
The genus Lasanius was described based on fossils found in Scotland, significantly enhancing our understanding of early vertebrate morphology.
Physical Characteristics
Size and Weight: Lasanius was a small fish, typically around 10-15 centimetres in length.
Unique Features: It had a streamlined body with a simple head structure, lacking extensive bony armour. Its body was covered with small scales. Its body shape can be somewhat compared to modern streamlined fish-like sardines.
Synapomorphies
Lasanius had a hypocercal tail, where the vertebrae extend downward into the lower lobe of the tail, making it more developed than the upper lobe. It also had unique body fins along the entire sides of its body, which are not homologous with the fins seen on modern fish. All members of the class Anaspida are vertebrates but true agnathians on the Cyclostome line of the vertebrate tree, meaning they are more closely related to hagfishes, lampreys, and conodonts than to today’s fish.
Known Species
Lasanius megaloptera
Behaviour & Ecology
Diet: Likely a filter feeder, consuming small particles and microorganisms from the water.
Behaviour: Lasanius was probably an active swimmer, using its streamlined body to navigate efficiently in its shallow marine habitat.
Ecological Interactions: Coexisted with other early vertebrates and a variety of invertebrates, contributing to the complex ecosystems of the Silurian seas.
Fossil Discoveries
Significant Discoveries Timeline: Early 20th century: First described by Sir E. Ray Lankester.
Key Paleontologists: Sir E. Ray Lankester, Erik Stensiö
Fossil Sites: Scotland; Ludlow Bone Bed, England. These sites are crucial for studying the diversity of Silurian vertebrates.
Current Specimen Locations
Natural History Museum, London
National Museum of Scotland.
These institutions hold some of the most complete and well-preserved specimens.
Scientific Research & Theories
Recent Studies: Focus on the anatomical features and phylogenetic position of Lasanius within early vertebrates.
Scientific Debates: Discussions continue about the evolutionary significance of Lasanius and its relationship with other early jawless fish.
Extinction Theories
Theories and Debates: Lasanius and other anaspids faced extinction towards the end of the Silurian period, likely due to changing environmental conditions and competition with emerging jawed vertebrates.
Cultural & Historical Impact
Pop Culture and Media: Lasanius is not widely featured in popular media but is occasionally mentioned in scientific discussions about early vertebrate evolution.
Pop Culture Influence: The genus remains largely unknown outside of paleontological circles.
Interesting Facts & Trivia
Primitive Features: Lasanius’ simple head structure and lack of extensive bony armour make it distinct among other early vertebrates.
Streamlined Body: Its streamlined shape suggests a lifestyle that prioritized agility and speed in the water.
Discover More Fascinating Anaspids
Lasanius has some famous cousins like Birkenia, Pharyngolepis, Pterygolepis and Rhyncholepis (previously known as Anaspis, the genera that gave Anaspids their name but has since fallen away).
Other extremely interesting Anaspida are the Canadian discovery with the insanely large hypocercal tail, Endeiolepis and Scotland’s spiny-backed Cowielepis and Devoniankerreralepis.
Documentaries Featuring Some Awesome Early Vertebrates Like Lasanius
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. 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.
3. 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!
4. 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.
5. 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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