Lasanius

Lasanius Temporal range: Early Silurian 443.8 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Lasanius problematicus
Life reconstruction of Lasanius problematicus
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	†Anaspida?
Family:	†Lasaniidae
Genus:	†Lasanius Traquair 1898
Type species
Lasanius problematicus Traquair 1898
Species
L. altus Smith 1958 L. armatus Traquair 1899 L. problematicus Traquair 1898

Lasanius is a genus of basal jawless fish from the Early Silurian, around 443.8 million years ago, known from fossils found near Lesmahagow, Scotland. Specimens range from 13.3 to 74.5 mm in length.^[1]

Lasianus has a pair of eyes, and a notochord, and while it has rows of bony scutes running along its back, it lacks the armour typical of other Paleozoic jawless fish like ostracoderms. There are also structures close to the front of the animal dubbed "chains" and "rods", of unclear function. At the end of the body a hypocercal tail fin was present in the form of a caudal lobe.^[1] Historically, it has often been allied with the anaspids, though other studies found it to be unrelated. A comprehensive redescription published in 2023 found that it was a stem-group cyclostome, more closely related to hagfish and lampreys than to jawed fish.^[1]

• R.H. Traquair M.D. LL.D. F.R.S. (1898) IX.—Notes on Palœozoic fishes.—No. II, Annals and Magazine of Natural History, 2:7, 67–70, DOI: 10.1080/00222939808678013
• Traquair, R. (1899). XXXII.—Report on Fossil Fishes collected by the Geological Survey of Scotland in the Silurian Rocks of the South of Scotland. Transactions of the Royal Society of Edinburgh, 39(3), 827–864. doi:10.1017/S0080456800035237

• Underwhelming Fossil Fish of the Month: February 2016
• Lasanius fossils

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