The Geiseltal fossil collection from southern Sachsen-Anhalt Germany contains remarkably well-preserved fossils of middle Eocene age. These include several crocodylian skulls, representing at least four different genera with a fifth genus represented by two mandibular rami. As sites with this many crocodylian genera are unknown in modern ecosystems, it has been hypothesized that these crocodylians may have differences in habit as compared to living crocodylians. In order to test similarities between the Geiseltal crocodylians and extant species, an analysis was conducted using geometric morphometrics to quantify shape in crocodylian skulls of all living species (n = 218) and all well-preserved crocodylian skulls of the Geiseltal fauna (n = 28). A relative warps analysis was used to quantify and compare skull shape, revealing Allognathosuchus and Boverisuchus to be very distinct from each other as well as from Asiatosuchus and Diplocynodon. Overlap in shape alone exists between some Diplocynodon and some Asiatosuchus, but there was significant difference in adult size. When compared with extant crocodylians, three Geiseltal genera occupied distinctly non-modern morphospace in the first two relative warps axes. Comparison of the diets of living crocodylians with similarly shaped skulls was used to reconstruct the prey preferences of the Geiseltal crocodylians, revealing differences in specialization. During the middle Eocene high global temperatures, partitioning of prey preference may have allowed this group to attain its higher than usual diversity, reducing the amount of direct competition.

Eusuchians with deep snouts and labiolingually compressed teeth are known from the Palaeogene of Laurasia. These are usually referred to Pristichampsinae, but the type species, Pristichampsus rollinati, is based on insufficiently diagnostic material and should be treated as a nomen dubium. At least two Lutetian species formerly referred to Pristichampsus can be recognised – Boverisuchus magnifrons in Germany and possibly elsewhere in Europe, and Boverisuchus vorax, new combination, in western North America. Material from the middle Eocene of Italy and Texas may represent distinct species. A phylogenetic analysis confirms their close relationship and also supports a relationship with two Asian forms – early Eocene Planocrania datangensis and Palaeocene Planocrania hengdongensis. The name Planocraniidae Li 1976 is applied to this group. A distinctive quadrate with a prominent dorsal peak between medial and lateral hemicondyles is known only in Boverisuchus, and although the teeth of Planocrania are flattened, they are not serrated. Planocraniids maintain a phylogenetic position as the sister group to Crocodyloidea+Alligatoroidea, but this part of the tree is unstable and discovery of older, more primitive planocraniids will help resolve conflicts on the phylogenetic relationships of extant crocodylian lineages.