Pabwehshi

Pabwehshi pakistanensis is a Late Cretaceous crocodyliform known from the Pab Formation of Balochistan, Pakistan. Its best fossil preserves the front of the snout with the upper and lower teeth locked together, an uncommon view of how a fossil animal actually closed its jaws. A second fragment adds part of the lower jaw, but the back of the skull and the rest of the skeleton remain unknown. Pabwehshi is included in the ancient crocodylomorph catalogue.

The teeth form a zigzag cutting arrangement with enlarged, serrated crowns. That anatomy supports a powerful bite that could pierce and slice tissue. It does not identify a particular prey animal. Its often-repeated assignment to Baurusuchidae is plausible, but depends on a small, incomplete sample rather than a complete skull.

Quick facts

Discovery and the Vitakri fossils

Muhammad Sadiq Malkani found the holotype, GSP-UM 2000, at Vitakri 16. Thomas Wilson, Malkani and Philip Gingerich described the genus and species in 2001. The name combines a local place-name with a word for a crocodile-like animal; pakistanensis marks the country of origin. The original is held by the Geological Survey of Pakistan in Quetta, and the University of Michigan collection has a cast catalogued as UM 14127.

The holotype includes the paired premaxillae, parts of the maxillae and nasals, the vomer, portions of the dentaries and the right angular. The right side is more complete; the left is more weathered. A second specimen, GSP-UM 2001, preserves the fused front of both dentary branches from Vitakri 3. It agrees in size and tooth pattern, while showing areas hidden by the closed mouth of the holotype. These are separate fossils, not parts of one assembled skeleton.

A short snout with unusually placed nostrils

In cross-section the preserved snout is D-shaped or nearly triangular. At the level of the fifth tooth position, its height is about three quarters of its width; toward the tip the dimensions become closer. The external nostrils opened at the end of the snout and extended back to around the third tooth. A raised bony rim borders them, with a small pocket-like recess in the rear upper corner.

These details help diagnose the front of the skull, but they do not reveal its full profile. The eye region, braincase and jaw joint are missing. A reconstruction that gives Pabwehshi the deep skull of a well-known baurusuchid borrows from relatives; it is not a direct measurement of this animal.

How the teeth met

Each premaxilla carried three teeth. The third was the largest and projected below the lower jaw, fitting between its second and third teeth. A large second maxillary tooth occupied a notch between lower-jaw positions five and six. In the lower jaw, the third and sixth teeth were enlarged and entered spaces or pits in the upper jaw, while the fourth and fifth were much smaller. This alternating arrangement produced two large upper and two large lower crowns working against one another.

The crowns were long, flattened from side to side and serrated along both front and back edges. The original study counted about 2.8 denticles per millimetre along an edge. Such a blade-like surface could cut tissue, unlike the rounded crushing teeth of some other crocodyliforms. No stomach contents, coprolite or bitten prey fossil ties a specific animal to Pabwehshi, so naming a dinosaur as its prey would go beyond the evidence.

Relationships and what remains unresolved

The original authors placed Pabwehshi in Baurusuchidae, a group of mostly terrestrial South American predators, based on the reduced front tooth row, enlarged canines and serrated teeth. Later studies have varied: some analyses group it with baurusuchids, some place it near sebecids or peirosaurids, and others find its position unstable. The 2023 reassessment again recovered it within Baurusuchidae, potentially making it the group's only known member outside South America.

That result has a biogeographic consequence only if the anatomy and classification are secure. Maastrichtian Pakistan lay on the Indian subcontinent, after it had separated from other Gondwanan landmasses. One fragment cannot establish a route or date for dispersal. The name remains useful and the biting anatomy is striking, while exact body length, locomotion, habitat preference and family-level position are still limited by missing bones.

The two specimens help in different ways. The closed bite in GSP-UM 2000 exposes the interaction of upper and lower teeth, whereas GSP-UM 2001 shows the front of the lower jaw without the upper row obscuring it. Their agreement supports referral to one species, but neither adds the skull roof or the postcranial skeleton. This asymmetry matters: the strongest claims concern the cutting bite, while full-body art and precise size estimates depend on comparisons with better-known relatives. The preserved snout is not a scale model of the whole animal.