Dallasaurus

Dallasaurus is an extinct genus of small mosasauroid marine reptiles known from Late Cretaceous fossils in Texas. Its anatomy preserves features linking land-dwelling lizards with later, fully aquatic mosasaurs.

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Mosasauroidea: Mosasauroidea is a group of extinct squamate reptiles that includes mosasaurs and their close relatives. Dallasaurus is an early member of this broader group.
Aguja Formation: The Aguja Formation is a Late Cretaceous rock unit in Texas containing diverse terrestrial and marine fossils. Dallasaurus fossils were recovered from this formation.
Paddle (limb): A paddle is a flattened limb adapted to propel or steer an animal through water. Dallasaurus had limbs less specialized as paddles than those of later mosasaurs.
Mosasauroid evolution: Mosasauroid evolution is the diversification and anatomical change of mosasauroids from early relatives to later marine forms. Dallasaurus is evidence for an early, less aquatic phase of that history.
Mosasaurs: Mosasaurs were extinct marine squamates that diversified during the Cretaceous Period. Dallasaurus helps illuminate the early evolution of this later, more aquatic group.
Late Cretaceous: The Late Cretaceous is the final epoch of the Cretaceous Period, spanning about 100.5 to 66 million years ago. Dallasaurus lived during this interval.
Hydrodynamics: Hydrodynamics is the study of how fluids move and exert forces on objects. Water resistance shaped the body forms of increasingly aquatic mosasauroids.
Paleontology: Paleontology is the scientific study of ancient life through fossils. Fossil comparison established Dallasaurus as a distinct extinct genus.
Squamata: Squamata is the reptile order that includes lizards, snakes, and their extinct relatives. Dallasaurus belongs to the squamate lineage.
Texas: Texas is a state in the southern United States with extensive Cretaceous fossil-bearing rock formations. Its known Dallasaurus fossils come from Texas.