The first remains of Euthecodon were described by French paleontologist Léonce Joleaud based on material collected by the Bourg de Bozas expedition between 1900 and 1903 in Ethiopia.

Euthecodon differs from any other known longirostrine crocodilian in its deeply scalloped rostral margins, each tooth sitting in its own bony sheath, separated from the next by a notable constriction of the rostrum, given the skull a saw-like appearance when viewed from above.

The nasal bone bears a prominent ridge leading up to the eyes, giving its forehead a sloping appearance somewhat similar to that of Crocodylus checchiai.

Notably, the skull table of Euthecodon is comparably small and almost square in shape, with oval supratemporal fenestra (not circular as in gavialoids).

In particular specimen KNM-ER 757 from the Koobi Fora Formation, a skull measuring 96 cm (38 in), was calculated to yield a length of 7.2–8.6 m (24–28 ft), accounting for a change in proportion in large sized crocodiles.

Brochu and Storrs however note that this estimate was achieved by using the proportions of nile and saltwater crocodiles, which differ significantly in skull to body ration when compared to longirostrine taxa.

According to their research, Euthecodon shows a series of adaptations present in E. arambourgi and progressively exaggerated in E. nitriae, reaching their peak with E. brumpti.

This latter interpretation is favored by the fact that Euthecodon was clearly already present in East Africa by the early Miocene, as indicated by the remains from Ombo and Rusinga Island.

For instance, Euthecodon differs from gavialids and most tomistomines in its small supratemporal fossae and the relatively gradual narrowing of the rostrum (something much more abrupt in gharials).

[18][19] Phylogenetic analysis utilizing molecular (DNA sequencing), stratigraphic (fossil age) and morphological data recovers Osteolaeminae, as shown below, with Mecistops as a close relative of Euthecodon.

Throughout their evolutionary history, many Pseudosuchian groups that evolved elongated skulls (Thalattosuchia, Tethysuchia and many gavialoids) also show enlarged supratemporal fossae.

The extremely elongated yet fragile rostrum, trap-like interlocking teeth and raised nares and orbits all indicate a piscivorous diet and aquatic lifestyle, perfected by the Pliocene to Pleistocene Euthecodon brumpti.

Mecistops cataphractus, the modern slender-snouted crocodile, also shows a longirostrine snout morphology, but is more generalist, feeding on amphibians, crustaceans and birds in addition to fish.

[15] Both Moghara and Gebel Zelten preserve fluvio-marine environments yielding fossils of sharks, dolphins and sawfish alongside catfish, anthracotheres, carnivorans, proboscideans and primates.

Gebel Zelten is especially well understood, the environment being reconstructed as rivers banked by tropical forests coming from the south and feeding into a large lagoon, while the intermediate areas are covered by savanna.

Although some crocodilians of the area (Crocodylus, Tomistoma and possibly Gavialosuchus) have been found on both sides of the Mediterranean, Euthecodon seemingly never ventured outside of Africa.