Ampelognathus

MEANING: Grapevine jaw

PERIOD: Late Cretaceous

CONTINENT: North America

Ampelognathus is a small basal ornithopod dinosaur. The dentary of Ampelognathus generally resembles those in other small ornithopods, but is slightly twisted along its length so that the teeth in the back of the jaw pointed somewhat inward. Ampelognathus measured about 80 cm in length, and 2 kg im body mass.

Abstract from paper: Sediments of the Woodbine Group exposed in northeastern Texas were deposited along the southwestern margin of Appalachia as a series of near-shore, shoreline, distal lowland swamp, lake, and fluvial deposits during a regression of the Western Interior Seaway in early and middle Cenomanian time. The Lewisville Formation (upper Woodbine Group) of north Texas preserves the most diverse terrestrial fossil assemblage known from Appalachia, but remains of small ornithischian dinosaurs have been conspicuously absent from it. An almost complete left dentary from the Lewisville Formation represents a new, small-bodied ornithopod taxon, Ampelognathus coheni gen. et sp. nov. The dentary is generally similar to those in non-iguanodontian ornithopods such as Hypsilophodon, Changchunsaurus, Haya, and Convolosaurus. Ampelognathus occupied an expected but previously missing component of the ‘mid’ Cretaceous terrestrial fauna of southwestern Appalachia. The growing diversity of fossil vertebrates and renewed paleobotanical study in the Lewisville Formation reinforces the importance of the unit’s fossil record for understanding eastern North American terrestrial ecosystems during an important transitional period in the earliest Late Cretaceous.

Ampelognathus is from the Early Cretaceous. The Cretaceous is the third and final geological period of the Mesozoic Era, with the Early Cretaceous making up roughly the first half, lasting from about 143 to 100 million years ago. The poles were ice-free, due to the relatively warm climate, and forests extended into high latitudes. The continued breakup of the continents created new coastlines and isolated landmasses, influencing the evolution of distinct dinosaur faunas.

It was a time of transition, as many groups of animals and plants began to take on more modern forms while others declined or disappeared. Pterosaurs continued to thrive, though early birds were becoming more diverse and widespread. Mammals remained small but adapted to a variety of ecological niches. In the oceans, ichthyosaurs and plesiosaurs were common, and early mosasaurs began to appear.

Dinosaurs remained the dominant land animals, with groups like iguanodontians, spinosaurids, and carcharodontosaurids rising to prominence. While sauropods declined in some regions, they remained abundant in the Southern Hemisphere. The first true ceratopsians appeared, and ankylosaurs replaced stegosaurs in their niche. Dromaeosaurs and other small theropods diversified. During this time, the first flowering plants evolved, gradually changing global ecosystems by providing new food sources for herbivores.

Ampelognathus is a basal ornithopod. Ornithopoda is one of the most succesful clades of the ornithischia. While later members of the group, like the hadrosaurs, grew into large, complex herbivores with sophisticated chewing mechanisms, their more basal relatives were far more modest in scale and anatomy. These early ornithopods, often found in Jurassic and Early Cretaceous deposits, were generally bipedal, lightly built, and fast-moving. These animals had long hind limbs, stiffened tails for balance, and small, beaked skulls suited for cropping low vegetation.

Many basal ornithopods appear to have relied on speed and agility to evade predators, rather than armor or social defense. Their teeth were simple compared to the dental batteries of hadrosaurs, but they show early signs of adaptations for plant processing, such as offset jaw joints and cheek-like structures to help hold food in the mouth. Despite their relatively primitive status in the ornithopod family tree, these dinosaurs were both ecologically important and evolutionarily pivotal. Over millions of years, this lineage gave rise to a wide variety of herbivores that would eventually dominate Late Cretaceous ecosystems across the globe.