''Archipelepis'' is a genus of extinct thelodont

agnatha Agnatha (; ) or jawless fish is a paraphyletic infraphylum of animals in the subphylum Vertebrata of the phylum Chordata, characterized by the lack of jaws. The group consists of both extant taxon, living (Cyclostomi, cyclostomes such as hagfish ...

ns, and are the most primitive recognized thelodonts of which whole body

fossils A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

are known.Wilson, Mark VH, and Tiiu Märss. "Thelodont phylogeny revisited, with inclusion of key scale-based taxa." Estonian Journal of Earth Sciences 58.4 (2009): 297œ310

/ref> Fossils of bodies and scales are currently known from Late

Telychian In the geologic timescale, the Telychian is the third and final age of the Llandovery Epoch of the Silurian Period of the Paleozoic Era of the Phanerozoic Eon. The Telychian Age was between 438.5 ± 1.2 million years ago (Ma) and 433.4 ± 0.8 M ...

to Wenlock-aged marine strata of northern

Canada Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, making it the world's List of coun ...

.Soehn, K. L., Märss, T., Caldwell, M. W. & Wilson, M. V. H., 2001: New and biostratigraphically useful thelodonts from the

Silurian The Silurian ( ) is a geologic period and system spanning 23.5 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the third and shortest period of t ...

of the

Mackenzie Mountains The Mackenzie Mountains are a Canadian mountain range forming part of the Yukon–Northwest Territories boundary between the Liard and Peel rivers. The range is named in honour of Canada's second prime minister, Alexander Mackenzie. Nahanni ...

, Northwest Territories, Canada. Journal of Vertebrate Paleontology, 21: 651-65

/ref>

Anatomy

Both species have similar body morphology, in that both resembled Tadpole, tadpoles with forked tails. Scale morphology differs in that ''A. bifurcata'' has forked scales with two prong-like spires, and that ''A. turbinata'' has bulbous, pointed scales that resemble upside-down

spinning top A spinning top, or simply a top, is a toy with a squat body and a sharp point at the bottom, designed to be rotation, spun on its vertical Axis of rotation, axis, balancing on the tip due to the gyroscopic effect. Once set in motion, a top will ...

References

External links

* Thelodonti genera Silurian jawless fish Paleozoic life of the Northwest Territories Canadian Arctic Archipelago Silurian first appearances Silurian extinctions Paleozoic life of Nunavut {{Paleo-jawless-fish-stub