Eusthenodon
Eusthenodon (Greek for “strong-tooth” – eusthenes- meaning “strong”, -odon meaning “tooth”) is an extinct genus of tristichopterid tetrapodomorphs from the Late Devonian period, ranging between 383 and 359 million years ago (Frasnian to Famennian). They are well known for being a cosmopolitan genus with remains being recovered from East Greenland, Australia, Central Russia, South Africa, Pennsylvania, and Belgium. Compared to the other closely related genera of the Tristichopteridae clade, Eusthenodon was one of the largest lobe-finned fishes (approximately 2.5 meters in length) and among the most derived tristichopterids alongside its close relatives Cabonnichthys and Mandageria.
| Eusthenodon Temporal range: Late Devonian | |
|---|---|
| Skull | |
| Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Sarcopterygii |
| Clade: | Tetrapodomorpha |
| Clade: | Eotetrapodiformes |
| Family: | †Tristichopteridae |
| Genus: | †Eusthenodon Jarvik, 1952 |
| Species | |
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The large size, predatory ecology, and evolutionarily derived characters possessed by Eusthenodon likely contributed to its ability to occupy and flourish in the numerous localities across the world mentioned above. Eusthenodon is attributed to being just one of many cosmopolitan genera within the "Old Red Sandstone" fish faunas of the Upper Devonian. As a result, it has been hypothesized that diversification of Eusthenodon and other morphologically similar tristichopterids were not restricted by biogeographical barriers and were instead limited only by their individual ecologies and mobility.
Most of the Eusthenodon remains found at these globally distributed localities consisted largely of cranial elements and largely not known from complete skeletons. Consequently, the majority of available literature covering Eusthenodon primarily focus on the intricacies of the bones associated with the skull in order to investigate the genus and while others draw conclusions from the known characters of Tristichopteridae. Johanson & Ahlberg (1997), in their assessment of new sarcopterygian material, present such conclusions proposing Eusthenodon likely possessed the same trifurcate or diamond-shaped caudal fin with an axial lobe turned slightly dorsally known in other tristichopterids (referred to as eusthenopterids by Johanson) along with a triangular-shaped first dorsal fin.