Arktocara ("Platanista gangetica") which inhabits the tropics, making it its closest living relative. Allodelphinidae also included the genera "Allodelphis", "Goedertius", "Ninjadelphis", and "Zarhinocetus". Its discovery further reinforces the theory that the Platanistoidea river dolphins originated in the oceans. Of the characteristics it shared with other platanistoids was a cylindrical projection of the periotic bone in the ear, deeply grooved rostral sutures on the beak, the widening of the cranium, a depression on the roof of the orbit in the eye socket, a smaller exposed palatine bone in the roof of the mouth, an elongated and convex spine in the tympanic bulla
St. Pierre Island of "Casuarina equisetifolia" trees up 12 m (40 ft) high on its northwestern part, covering a third of the land area. The trees were originally planted as windbreak for the mining camp, and have unexpectedly thrived and spread. Most of the plant species once found on St Pierre are now gone, including the "Pisonia", Suicide Tree ("Cerbera odollam") and rosemallow ("Hibiscus tiliaceus"). Some "Pemphis acidula" might persist. By about 1960, it was noted that the most common herbaceous plant was "Stachytarpheta indica", while the introduced Indian Blanketflower ("Gaillardia pulchella") had established itself widely. Sisal ("Agave sisalana"), Chinese tiolet ("Asystasia gangetica"),