The right premaxilla is incomplete, lacking its rostral portion. It preserves the postero-ventral edge of the external naris, a large premaxillary-maxillary notch for the placement of a hypertrophied lower tooth, and the palatal process of the premaxilla. In lateral view, the facial exposure of the premaxilla is high, almost vertical, and slightly dorsoventrally convex (Fig. 1A). The dorsal contact with surrounding bones is not preserved. The alveolar border is strongly convex with the lowest point coincident with the placement of the largest premaxillary tooth, as seen in other mesoeucrocodylians (Baurusuchus and Stratiotosuchus; [11], [13] and [38]). Ornamentation of the external surface exhibits disparities. The posterior half has deep, irregular grooves that continue over the maxilla; the rostral portion has a shallow ornamentation with small furrows and, just below the ventral edge of the external naris, there is a large, rounded depression that differs in texture from the remaining bone (Fig. 1). This depression, usually called perinarial area, is smooth and caudal-dorsally bordered by a relatively elevated rim that makes this region deeper. Dorsally, within the depression, there are two, relatively large, vascular foramina, as in Baurusuchus. This structure was possibly related to the soft tissue of the snout that would possibly regulate the opening and closure of the naris, as seen in some terrestrial crocodyliforms, in order to regulate the loss of water. This depression is also observed in other sebecosuchians such as Iberosuchus [1] and both species of Baurusuchus [13] and [38], in the basal notosuchian Simosuchus [7], and in peirosaurids such as Uberabasuchus [12] and Stolokrosuchus [28]. In several basal notosuchians, a perinarial region with the above-mentioned features is absent, showing only a small smooth area bordering the external naris, as observed in Notosuchus (MACN-PV-RN 1040). Immediately above the last premaxillary tooth, there are two large vascular foramina, and several irrigating vascular openings of small size.

In lateral view, the preserved border of the external naris is straight, with an acute angle between the caudal-dorsal and caudal-ventral rims. The shape and orientation of the ventral border of the external naris suggest that this opening was greatly laterally exposed. Despite the incomplete condition of the rostral portion of the premaxilla, the external naris seems to be relatively wide in rostral view, and elongated in lateral view.

The presence of a conspicuous paracanine depression located near the premaxilla–maxilla contact is widely spread among sebecosuchians, peirosaurids, trematochampsids, and in a few basal crocodyliforms (Orthosuchus [32]). In basal notosuchians and araripesuchids, this feature is absent.

In ventral view, the premaxilla preserves its palatal process, with a rough median surface to contact its left counterpart. This process is transversely narrow, suggesting that the rostrum, at the level of the hypertrophied tooth, was very narrow (Fig. 1B). The premaxilla palatal process is anteroposteriorly short, with two large vascular foramina and a small depression close to the rostral rim. This boundary, located at the level of the penultimate premaxillary tooth, is posteriorly concave and represents the border of the incisive foramen (or premaxillary fenestra), entirely enclosed into the premaxilla (Fig. 1B). In Wargosuchus, the incisive foramen and surrounding area seem to be highly vascularised. When observed anteriorly or dorsally, the palatal process of the premaxilla has a deep concave depression located posteriorly to the border of the incisive foramen and immediately medial to the lower edge of the external naris. This fossa is directly associated with the narial passage and seems to represent the recess area for a gland, possibly related to the nasal epithelium.

In lateral view, the contact of the maxilla with the premaxilla is irregular, as shown in Fig. 1A, located close to the posterior edge of the paracanine depression. In the preserved portion, a foramen on the suture is not evidenced. In median view, part of the suture is evident at mid-height. In addition, just at the lower and mid-level of the paracanine depression, the premaxilla has a rough surface to accommodate the palatal process of the maxilla (Fig. 1B). Behind the diastematic paracanine depression, the maxilla alveolar border is partially broken; however, there is a rounded, large edge that may represent the mesial border of the alveolus for the first maxillary tooth.

The available portion of the skull roof includes part of nasals, fragments of the lachrymals, both prefrontals, a portion of the fused frontals, and the left palpebral bone (Fig. 2). In dorsal aspect, the bones are deeply ornamented with deep, irregular grooves that become anastomozed in the nasals.

The posteriormost portion of both nasals is the only preserved part. The median suture, with its counterpart, is not evident (possibly due to the strong ornamentation). The nasal has a wide contact with the prefrontal and a very small median contact with the acute rostral projection of the frontals (Fig. 2A). The suture of both nasals with the prefrontal bone is transversal and interdigited. The nasal is strongly, dorsally concave, forming a low surface with regard to the remaining portion of the skull roof. When observed laterally, the concavity of the nasals makes a notorious step in the dorsal profile of the skull, the skull roof (posterior to the level of the orbit) being more elevated than the snout.

In ventral view, the nasal is wedge-like, lying over the lachrymals and prefrontals. It has a median crest formed by the median joint of both nasals that runs posteriorly until the contact with the frontals. The frontals, in addition, form the remaining posterior portion of the crest. This crest, formed by the nasals and frontals, is deep and separates medially the olfactory depressions that would lodge the olfactory bulbs (see below).

The prefrontals are the most notorious preserved bones, with a great dorsal exposure. In dorsal view, they are fairly rhomboidal, with two different surfaces. The medial surface is anteroposteriorly elongated and triangular. This portion of the bone is strongly ornamented, with a main deep groove diverging posteriorly and small furrows randomly distributed. The prefrontal contacts the frontal through a large, laterally concave suture. Both prefrontals converge rostrally, but they do not contact at midline; they are separated by a small cranial process of the frontals (Fig. 2A). The lateral surface of the prefrontal is separated from the rest of the skull roof by a step. This surface is large, almost unornamented, and provides support for the palpebral bone. The right palpebral is missing, exposing the dorsal surface of the lateral process of the prefrontal and its contact with the lachrymal (Fig. 2A).

In ventral view, the prefrontals also have a great exposure (Fig. 2A), forming most of the roof of the olfactory cavity. The left prefrontal is more complete, preserving part of the prefrontal pillar (i.e., descending process). The ventral flaring of the prefrontal pillar that would contact the palate (the palatine and the pterygoid) is not preserved. In the right side, the prefrontal pillar is broken, showing a hollow, subtriangular section that might represent the prefrontal recess [54]. The prefrontal pillar is a thin laminar bone, ventrally projected that separates the olfactory cavity from the orbital cavity. The prefrontal pillar has a rounded notch located near the medial contact with the frontal, just lateral to the space for the passage of the olfactory tract and associated vasculature, which constitute the posterolateral edge of the orbitonasal canal, for the passage of the nasal artery and vein [46] and [54] (Fig. 2B). In lateral and posteriorly views, the suture between the prefrontal pillar and the lachrymal descending process is observed, passing just posterior to the lachrymal foramen (Fig. 2C).

The frontals only preserve their rostral portion. They are fused, triangular in shape, with an extremely sharp, acute angle that projects rostrally to meet the nasal through a very small suture. The frontals are ornamented as the remaining bones, but it is noteworthy that they have a deep and wide median groove that runs over all the length of the frontals until the beginning of the nasals, contrary to several notosuchians (Comahuesuchus, Notosuchus, and Mariliasuchus), where there is an axial ridge.

In ventral view, the frontals form the roof and walls of the constricted passage for the olfactory tract and associated vasculature that ends up at the olfactory cavity. The groove of the olfactory tract is laterally bordered by an acute descending process of the frontal, the cristae cranii, which would rostrally contact the prefrontal pillar and form the internal border of the orbitonasal canal (this contact and the internal border of the canal is not preserved in the holotype). At the level of the notch for the olfactory tract and associated vasculature, the frontals have a very low median crest that rostrally becomes more robust and tall. In posterior view, the broken profile of the skull roof exhibits a pneumatic frontal with notorious frontal recesses (Fig. 2C).

The lachrymals are badly preserved. In the left side, it is nonetheless observed that the lachrymal, together with the prefrontal, supports the palpebral and that its ascending process contacts the prefrontal pillar. The lachrymal foramen is clearly observed in posterior view. The lachrymal canal runs rostrally parallel to the olfactory cavity, as evidenced by the endocast and the longitudinal fracture of the available portion of the skull. The lateral surface of the lachrymal is slightly concave and ornamented as the other skull bones.

In the left side of the skull, the palpebral is in natural position. It is very large and deep, even with its posterior border broken off. The ornamentation of the palpebral consists of small furrows, mainly distributed on its medial half. In dorsal view, the procumbent palpebral hides the lateral surface of the lachrymal by means of a robust shelf. With the evidence at hand, we cannot assume about the presence/absence of an additional palpebral bone (i.e., posterior palpebral).

A plastic endocast was done with the skull fragment of MOZ-PV 6134 (Fig. 3) offering an opportunity to explore the internal structure of the posteriormost portion of the nasal cavity of Wargosuchus. Furthermore, it could be a useful tool to obtain characters to reconstruct the phylogenetic relationships among mesoeucrocodylians, at the time when these internal traits become available in the literature.

The plastic endocast shows the presence of large olfactory bulbs (Fig. 3), even much more prominent than in Sebecus [14]. Apparently, they are medially divided by an axial bony septum. In the endocranial cast of Sebecus, the olfactory bulbs seem to be more elongated antero-posteriorly and narrower transversely, lacking both a clear median division and an abrupt bulkiness just passing the frontal notch for the passage of the olfactory tract. In extant crocodylians, the olfactory bulbs are relatively smaller [14] and [43], and in the skull roof, the depression for these bulbs are shallow.

The large size of the depressions for the olfactory bulbs suggests a well-developed olfactory system [15]. Data on the size and shape of the olfactory bulbs is poorly documented in extinct mesoeucrocodylians. In Wargosuchus and Notosuchus (MACN-PV N 106), the olfactory bulbs are greatly developed, even more than in Sebecus, suggesting a specialized adaptation for useful smell. This inference agrees with the terrestrial mode of life of these notosuchians in contrast to extant eusuchians that have a poorly developed olfactory system related to the semiaquatic mode of life.

Other features observed in the endocast of Wargosuchus are the orbitonasal passage for the nasal artery and vein that runs close to the olfactory tract, and the nasolachrymal canal that runs from the nasolachrymal foramen to the olfactory bulbs (Fig. 3). The canals of both sides, in addition, run parallel, although separated by a thin wall.

There are only two teeth preserved in the posterior portion of the premaxilla. Rostrally, this bone is broken off; thus, the precise number of premaxillary teeth remains uncertain. The two posterior premaxillary teeth differ considerably in size between them. The penultimate tooth has a basal circular cross-section, which is less than half the size of the last tooth. Most of the crown of this tooth is broken off, but apparently, it was slightly procumbent anteroventrally. The basal surface of the crown presents neither indication of serrated carinae nor texture enamel.

The last premaxillary tooth is large and caniniform in shape, even lacking its apex. It possible overhangs the lower jaw. It is robust, sub-conical, and slightly curved backward. In lateral view, the mesial border is straight, whereas the distal border is slightly concave. A poorly preserved minute carina with minuscule denticles is present on the disto-labial surface of this tooth. Additionally, the size of the paracanine depression indicates the presence of, at least, one hypertrophied lower tooth, as commonly found among baurusuchids.