Egypt's New Mosasaur Had Jaws Built for Speed

The Second Hunter in the Shale

The Dakhla Shale of Egypt's Western Desert has produced another small marine predator from the last age of dinosaurs. Researchers describe Halisaurus auriculatus as a new species of halisaurine mosasaur — one of the streamlined reptiles that occupied Late Cretaceous seas.

The peer-reviewed description in Acta Palaeontologica Polonica is based on a partial skull and skeleton from lower Maastrichtian rock, roughly 70 million years old, near Teneida in the Dakhla Oasis.

One ancient sea held two close relatives with very different hunting hardware.

A Long, Light Bite

The animal's upper and lower jaws were unusually long and slender. Each carried more than 20 teeth, while the rear attachment point for major jaw muscles sat farther back than in related forms. The anatomy points to a bite that closed quickly but delivered less force.

Its quadrate — a skull bone involved in the jaw joint and ear region — was stranger still. Enlarged notches and thin bony processes formed a ring around the passage associated with the hearing apparatus. The authors interpret that construction as a specialised ear unlike those of other known halisaurines.

• The long jaws favoured rapid capture over crushing power.
• The high tooth count created a narrow trap for small prey.
• The modified ear suggests a distinct sensory adaptation, although its exact performance is unknown.

The fossil does not reveal a preserved stomach or a recorded chase. Diet and hunting style are anatomical inferences, not observed behaviour.

Sharing a Cretaceous Sea

Halisaurus hebae, another species from the same formation, had shorter, more powerful jaws. Finding both animals together makes simple replacement unlikely. Instead, their contrasting skulls support niche partitioning: close relatives dividing food or hunting conditions inside the same ecosystem.

The new species also strengthens the picture of North Africa as a centre of halisaurine diversity. These were not interchangeable little mosasaurs beneath the famous giants. Their jaws and ears were splitting the sea into different ways of making a living.

Extinction erased both hunters. Their bones preserved the separation between them.