Hadrosaurinae (Hadrosaurines)
Translation: Bulky Lizards
Hadrosaurinae (had-ruh-SAWR-i-nay) is a subfamily of Hadrosauridae. This family of bipedal dinosaurs had slender legs and arms. They were marked by low spines on their pelvic vertebrae. Also called the duck-bills, their snouts were spoon-shaped. Their most striking feature was the crest that adorned their heads. The hadrosaurines lived during the Late Cretaceous Period and flourished in the lands of North America, Europe, and Asia. Anatosaurus, Brachylophosaurus, Claosaurus, Mandschurosaurus, Hadrosaurus, and Lophorohothon,

Hadrosauridae (Hadrosaurids)
Translation: Duck-Billed Lizards
Hadrosauridae (had-ruh-SAWR-ih-day) is a family of commonly referred to as "duck-billed dinosaurs." Bipedal, hadrosaurs could grow up to 40 feet (12 meters) long. Their arms ended in webbed, four-fingered hands. Typically they ate fruit and various sorts of vegetation. Typically hadrosaurs are marked by a crest atop their heads, although some had none. The crest was usually shaped like a long tube or a short hatchet. The dinosaurs of the Hadrosauridae family lived during the Late Cretaceous Period. Anatosaurus, Brachylophosaurus, and Saurolophus.

Hands
A dinosaur's front feet are usually referred to as hands. Because each family of dinosaurs had distinctive hands, they are often used as clues in determining to which dinosaur family fossilized remains belong. Ornithopods typically had five-fingered hands whose bones resembled the arrangement of human hands. The hands of the carnosaurs ranged from five-fingered to two-fingered. The best-known carnosaur, Tyrannosaurus rex, had hands with only two fingers each.

Harpymimidae (Harpymimids)
Translation: Harpy (mythical bird) Mimics
The Harpymimidae (hahr-pee-MYE-mi-day) is a family of ornithomimosaurid (ostrich-like) theropods. Their hands were relatively large, their feet were most likely three-toed, and they were evidently fast runners.

Hearing
Judging from present-day reptiles, hearing among dinosaurs was probably well-developed. Among some dinosaurs with little physical armor, such as ornithopods, hearing was probably acute, since it would have been one of the few defenses available to them. See also Sensory Perception.

Herbivore
Translation: Plant Eater
Herbivore (HER-bi-vor) is the name given to any animal that eats plants. Herbivorous dinosaurs greatly outnumbered those that were carnivorous. Ornithischians and sauropodomorphs were herbivores. See also Carnivore and Omnivore.

Herd
A herd is an assembly of animals, which gathers for mutual protection against predators. It appears that many species of dinosaurs traveled in herds; their footprints have been discovered at trackways. Although the evidence is debatable, it does appear from certain trackways that the adults of some species forced their young to travel in the center of the herd, to shield them from danger. It is worth noting that herding is associated with warm-blooded animals, and this is one of the arguments used for dinosaurs being warm-blooded.

Herrerasauridae (Herrerasaurids)
Translation: Herrera's Lizards
Herrerasauridae (her-ray-rah-SAWR-ih-day) is a family of ceratosaurs. This family of dinosaurs lived during the Middle Triassic Period. They were bipedal and quadrupedal, and the structure of their teeth indicates that they were omnivorous.

Heterodontosauridae (Heterodontosaurids)
Translation: Different Toothed Lizards
Heterodontosauridae (het-er-uh-don-tuh-SAWR-ih-day) is a family of very small ornithopods. They are marked by their unusual teeth: in both upper and lower jaws, they had canine teeth. Heterodontosaurids were bipedal herbivores that lived during the Late Triassic Period. Geranosaurus, Heterodontosaurus, and Lycorhinus.

Homalocephalidae (Homalocephalids)
Translation: Level Head
Homalocephalidae (ho-mah-luh-SEF-uh-lee-day) is a family of pachycephalosaurian dinosaurs. These particular bone heads were small-to-medium in size, and had flat bone heads (in contrast to their relatives, the dome-headed Pachycephalosauridae.)

Homoiotherm
Translation: Uniform Heat A homoiotherm is an animal whose internal temperature remains at the same level no matter what the ambient temperature. These animals are generally warm-blooded, but large cold-blooded animals would have enough body mass to keep a fairly constant internal temperature. See Ectotherm and Endotherm.

Horns
Dinosaurs with horns probably used them for defense against predators, and they may have used them when fighting for mates or settling territorial disputes with members of their own species. Dinosaur horns ranged from little bumps to 2 feet- (61-cm) long nose horns. See Ceratopsians.

Huayangosauridae (Huayangosaurids)
Translation: Huayang Lizards
Members of Huayangosauridae (hwah-YAHNG-o-SAW-ih-day) family are moderately-sized forms of stegosaurs. They retain premaxillary teeth and show evidence of two rows of small, paired dorsal plates. Their tails bore spikes.

Hypsilophodontidae (Hypsilophodonts)
Translation: High-Crested Tooth
Hypsilophodontidae (hip-sih-lo-fuh-DON-tih-day) is a family of small- to medium-sized ornithopods. Hypsilophodonts were bipedal, with five fingers and four toes, and herbivorous. It is thought that they were swift creatures. They flourished during the Late Triassic and into the Cretaceous Periods. Agilisaurus, Atlascopcosaurus, Hypsilophodon, Othnielia, Parksosaurus, and Thescelosaurus.