The Family Ciconiidae currently comprises 19 species distributed primarily in the tropical and sub-tropical regions around the world. Recent studies on phylogeny within the genus and families of birds provided a new opportunity for the analysis of the cranial structure in a phylogenetical context. Consequently, the aim was to describe in detail the cranial osteology of the representative species of Ciconia (C. abdimii, C. ciconia, C. episcopus, C. maguari and C. nigra), aiming to compare the characters found amongst the species that form this genus and these with the one from other members of the Family Ciconiidae and determine the family relationships amongst the species, using the methodology of phylogenetic systematic. Cranial osteology has proven to be a good tool for the cladistic analysis of the genus Ciconia, providing osteologic characters that proves the monophyly of the group. The topology of the tree obtained in the present study has revealed itself as well resolved, presenting positive perspectives to the morphologic studies of the genus. The cladogram presented corroborates the hypothesis of the monophyletic characteristic of the Ciconia, the C. ciconia being the most basal of the genus. The topology of the cladogram is: (C. ciconia ((C. nigra (C. abdimii C. episcopus)) C. maguari)). In general, Ciconia presents a specialized skull, with peculiar characteristics and different from what is observed in other groups of birds.

The species of the Ciconiidae family (Ciconiiformes), commonly known as storks, exhibit a cosmopolite distribution, being represented by swamp birds of medium and large size. The present work aimed to describe minutely and comparatively the cranial osteology of Leptoptilus species. The study was performed based on the description of cranial bones of the species Leptoptilus dubius, L. crumeniferus, and L. javanicus. The studied specimens were previously prepared (dry crania and mandibles). Among the studied characteristics, it was possible to observe some structures of systematic importance, such as the zygomatic process, the temporal fossa, the ectethmoid, the superior maxilla, the quadrate bone that interconnects the palate, the neurocranium, and the mandible, performing a key role in the work of cranial kinesis. Leptoptilus javanicus possesses, in the lateral portion of the cranium, an emargination of the rostrodorsal edge of the postorbital process, not observed in either Leptoptilus dubius or Leptoptilus crumeniferus. The fossa ventralis possesses a projection in the caudal extremities in L. dubius and L. crumeniferus, which is absent in L. javanicus. The transpalatine process is present in both L. dubius and L. crumeniferus and is absent in L. javanicus. The pterygoid process of the palatine is short in both L. dubius and L. crumeniferus, and long in L. javanicus. The ectethmoid is reduced in both L. dubius and L. javanicus, whereas in L. crumeniferus, besides being more developed, it presents a “U” shape. Based on the present study, L. dubius and L. crumeniferus are phylogenetically closer to each other than L. javanicus.

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