The only palaeophiid known from Mali is Palaeophis colossaeus, one of the largest known snakes. Although palaeophiids are generally considered to be aquatic, there is a continuum of morphologies ranging from those that suggest a relatively unspecialized morphology, to those that are highly modified for aquatic life. Palaeophis colossaeus is a representative of the former group, with rather broad vertebrae, and ribs that are not set ventrally on the centrum. The presence of these characters has led to the suggestion that P. colossaeus represents the basal condition of the family, albeit as a late occuring member.
However, it should be noted that the body type of snakes in general is particularly suited for swimming, and among living snakes, even those that show few of the recognized anatomical aquatic adaptations are capable swimmers. Palaeophis africanus is often included in the group of palaeophiids that are morphologically unspecialized, but the vertebrae show greater mediolateral compression than in other species of that assemblage, suggesting some specialization for an aquatic lifestyle.
Estimates of body size of Palaeophis colossaeus have been reported to exceed 9 m. Using a regression of cotylar width on body length, the total body length of P. colossaeus is estimated to be 12.3 m. Thus, P. colossaeus was larger than any other known palaeophiid, was the largest known sea snake, and exceded the size of any living snake species. It is exceeded in size only by the Paleocene boid Titanoboa from Colombia.
Complicating efforts to estimate its size is the fact that it is known only from isolated vertebrae. In fact, no palaeophiine snake is known from a complete specimen, and very few are known from articulated material at all. The closest possible relative known from a nearly complete skeleton is the small species Archaeophis proavus, from Monte Bolca in Italy, that has more than 500 vertebrae in total, a number that exceeds the vertebral count reported for living snakes (up to 440). This discrepancy means that any estimates of lentgh for palaeophiids based on comparisons with modern snakes may underestimate the actual size of the snake.
All living snakes are predatory carnivores, and no evidence exists that suggests palaeophiids were any exception. More difficult to determine is whether palaeophiids were macrophagous, that is, had the ability to consume prey of larger diameter than themselves. To settle this question, cranial material is necessary. The closest putative relatives of Palaeophis with skulls, A. proavus and “Archaeophis turkmenicus”, provide contradictory evidence as to the kinetic capabilities of the skull. Archaeophis proavus has been hypothesized to have a kinetic skull similar to that of many living snakes, whereas A. turkmenicus is reported to have less mobile cranial joints. If the skull of P. colossaeus was closer to that of A. proavus, the upper limit for the size of consumable food would have been quite large. Contemporaneous species that could have been part of the diet of a large, macrophagous snake include sharks, lungfish, pycnodonts and other large fishes, dyrosaurid crocodyliforms and turtles. It is also not certain whether palaeophiids were constrictors. If palaeophiids were macrophagous it is likely they would have killed large prey before attempting to consume them to prevent serious damage to their heads in the process.
We have reconstructed the palaeophiids as living in nearshore environments, where their fossils are often found, associated with mangroves and estuaries. They are known, for example, from similar deposits in El Fayum, and are comparatively rare in sediments interpreted as pelagic or open ocean. Our data is consistent with the hypothesis that genus Palaeophis known from Mali was probably not pelagic