Though known only from fragmentary remains, Tahulalepis represents an extinct genus of Anaspid, a jawless fish (agnathan) on the Cyclostome lineage of vertebrates that lived from the Ludfordian Stage of the Silurian Period to the Pridoli Epoch, approximately 423.0 to 419.2 million years ago.
Discovered primarily in boreholes and outcrops in Estonia, Tahulalepis is notable for its distinctive scale structure and affiliation with the early vertebrate evolutionary lineage of Cyclostomiformes, adding to our understanding of the Birkeniiformes order of anaspids.
In this post, we explore where exactly Tahulalepis fits on the Tree of Life (taxonomy), when and where it lived, how it went extinct, what its fossils look like, its physical characteristics (synapomorphies), discovery information, scientific mysteries, where you can go to see its fossils, documentaries featuring Maurylepis and it’s kin, and more…
Tahulalepis 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: Tahulalepididae
- Genus: Tahulalepis
- Species: Tahulalepis elongituberculata, Tahulalepis kingi
Geological Time and Habitat
- Period: Silurian
- Stratigraphic Range: Ludfordian Stage of the Silurian Period to the Pridoli Epoch (approximately 423.0–419.2 million years ago)
- Habitat: Tahulalepis lived in shallow marine environments characterised by diverse ecosystems rich in early vertebrate species. It likely inhabited regions similar to those seen in today’s shallow seas, taking advantage of nutrient-rich waters found around ancient boreholes and outcrops in Estonia.
Evolutionary Significance
As a member of the Anaspida class, Tahulalepis offers unique insights into the early vertebrate evolution along the Cyclostome lineage (truly jawless vertebrates), making Tahulalepis and its anaspid relatives closer in relation to modern hagfish and lampreys.
In the past, it was assumed that very fish-like vertebrates like Tahulalepis might have been the precursors to modern fish – the gnathostome lineage. But this was found to be untrue. Despite Tahulalepis and other anaspids’ very fishy appearance, their fish and body shape are merely convergent, they are much closer related to the more eel-like and truly jawless vertebrates such as conodonts.
Physical Characteristics
Though all the specimens are fragmentary, it’s estimated to be between 10–15 cm in length. Tahulalepis features a unique scale structure, which is characterised by elongated tubercles. This scale morphology is distinct among anaspids and suggests adaptations unique to Tahulalepis.
Tahulalepis Synapomorphies
As an early vertebrate, Tahulalepis shared several foundational features with other early vertebrates:
- Vertebral Column: Bony or cartilaginous vertebrae that surround the ancestral notochord and nerve cord, creating a backbone or spine.
- Neurocranium: A protective brain casing made of cartilage or bone.
- Tri-partite Brain: Like other vertebrates, Tahulalepis had a brain divided into three distinct lobes: olfactory (smell), optic (sight), and otic (hearing).
Specific to Anaspida, Tahulalepis displayed:
- Hypocercal Tail: The vertebrae extend into the bottom of the tail, with the upper lobe formed by fin structures.
- Body Fins: Although specifics for Tahulalepis are unknown, many anaspids had elongated, unbroken fins along the body that are convergent and not homologous to modern-day fish fins at all.
Intriguing Mysteries Around Tahulalepis
Maurylepis, like many other anaspids, raises fascinating questions about early vertebrate evolution. The genus’s scale structure, with its elongated tubercles, sets it apart and may indicate unique environmental adaptations.
Furthermore, Tahulalepis and related anaspids offer insights into an evolutionary lineage that predates the fossil record by nearly 100 million years.
See, since anaspids display body features that make them primitive members of cyclostomata, we know they must have diverged from the main cyclostome line as early as the Cambrian – even before conodonts.
The problem with that is: We don’t find their fossils until 100 million years later in the Silurian. So, either we don’t know how to recognise early members or our understanding of early vertebrate evolution is wrong, or there’s yet another scintillating Cambrian discovery somewhere out there just waiting for a rockstar scientist to find it.
Discovery & Classification
- Discovery Date: 2002
- Discovery Location: Various boreholes and outcrops in Estonia, including the Tahula 709 borehole and Kuressaare Stage.
- Discovering Paleontologist(s): Henning Blom, Tiiu Märss, Carl Miller
- Naming: The genus name Tahulalepis is derived from the locality “Tahula” and “lepis,” meaning “scale” in Greek.
Known Species of Tahulalepis
There’s a reference to two species names within this genus, the easily verifiable Tahulalepis elongituberculata and some obscure references to a Tahulalepis kingi. The species elongituberculata refers to the elongated tubercular shape of its scales, a distinguishing feature of this genus.
Behaviour and Ecology
Although specific behavioural evidence is unavailable, Tahulalepis likely shared ecological characteristics with other anaspids, possibly serving as a filter feeder or scavenger. Its distinctive scale structure may have provided additional benefits, such as protection from predators or hydrodynamic advantages.
Fossil Discoveries
The fossils of Tahulalepis were primarily discovered in boreholes and outcrops in Estonia, dating to the Ludfordian Stage of the Silurian Period. These fragmentary fossils, though limited, offer insights into their morphology and serve as a critical reference point for understanding anaspid diversity.
There are at least 7 Estonian fossils. And then there is an eighth, from Sweden.
Scientific Research and Theories
The study of Tahulalepis has been supported by works such as those by Blom et al. (2002), which examine the diversity and distribution of birkeniid anaspids in the Northern Hemisphere. These studies enhance our understanding of Tahulalepis and related genera within early vertebrate evolutionary frameworks.
Current Specimen Locations
There are 8 known specimens of Tahulalepis, recorded within collections at:
- TalTech (Tallinn University of Estonia) fossil collections – 7.
- Palaeozoological Collections (PZ) in Sweden – 1.
Extinction Theories
Like other anaspids, Tahulalepis likely faced extinction due to environmental changes during the Silurian Period. Shifts in sea levels, marine ecosystem dynamics, and the rise of more advanced vertebrates likely contributed to its eventual extinction.
Interesting Facts & Trivia
- Tahulalepis elongituberculata is named for the elongated, tubercular structure of its scales, a unique trait in early vertebrates.
- The genus name Tahulalepis references the locality of its discovery, Tahula, adding geographic context to its scientific story.
- Anaspids are a baffling anomaly among early vertebrates, so fish-like yet not closely related to what we think of as “fish”.
Additional Resources & References of Tahulalepis
- 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.
- 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.
Discover More Cool Anaspids
Tahulalepis 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 Tahulalepididae family along with Trimpleylepis.
Some close relatives might include the Rhyncholepididae family, with more fragmentary genera like Rytidolepis, Schidiosteus, Vesikulepis, Silmalepis and Maurylepis that are basically only known from their scales and small fragments.
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 Tahulalepis
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 and Silurian 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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