Loganellia

Loganellia is a genus of jawless fish which lived between 430-370 million years ago, during the Silurian and Devonian periods of the Paleozoic.[1] Loganellia belonged to the Thelodonti class and like other Thelodonts possessed scales instead of plate armor.

Loganellia Temporal range: 430–370 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Loganellia scotica (Fossil and model, Museum am Löwentor, Stuttgart)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Superclass:	Agnatha
Order:	†Loganelliformes
Family:	†Loganelliidae
Genus:	†Loganellia Fredholm, 1990
Type species
†Loganellia scotica (Traquair, 1898)
Species
†Loganellia aldridgei †Loganellia cuneata †Loganellia grossi †Loganellia matura †Loganellia prolata †Loganellia scotica †Loganellia sulcata †Loganellia unispinata

Loganellia are thought to be more closely related to the crown group of gnathostomes than conodonts. They are noted for their denticle whorls - oropharyngeal denticles that lined their branchial bars - which are thought to be homologous with other, later gnathostome teeth. In this sense, Loganellia may possess the earliest known dental structures related to modern teeth, and would have evolved in the throat, rather than through dermal denticles or jaws.[1]

Fossil

Loganellia, swimming in a shallow sea 400 million years ago.

Loganellia scotica (Traquair, 1898), drawn by Traquair[2]

References

1. Ungar, Peter (2010). Mammal Teeth: Origin, Evolution and Diversity. Baltimore: Johns Hopkins University Press. p. 77.
2. Goodrich, E.S. (1964) [1909]. "Vertebrata Craniata". In Lankester, Ray (ed.). A Treatise on Zoology. IX. Amsterdam: Asher. p. 197. Includes illustrations by Traquair.