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Do you ever wonder about the different kinds of dinosaurs and how they’re classified? Do you want to know why some are more similar to birds or reptiles and if they were all carnivorous?
In that case, this is the right place to start. This post will explore the main types of dinosaur families and their characteristics. 
Main Dinosaur Families and Groups
Dinosaurs are divided into two main groups based on their hip bone arrangement: saurischians (lizard-hipped) and ornithischians (bird-hipped). The saurischians have their lower bones of the hips pointing away from each other, and the ornithischians have those bones pointing backwards. Interestingly, the birds we see today are descendants of the saurischians dinosaurs.
The saurischians are further divided into theropods and sauropodomorphs. Theropods are bipedal carnivorous dinosaurs and the main ancestors of birds. The sauropodomorphs sub-type consists of quadrupedal, herbivorous long-tailed sauropods and the “prosauropods.” The ornithischians consist of different types, and all of them have a beak bone at the tip of their lower jaw.
These two groups of dinosaurs branch out into fifteen main families, as follows.
1) Tyrannosaurs
Tyrannosaurs (tyrant reptiles) were ferocious killers of the Cretaceous period and belonged to the theropods group. They had peg-like teeth with a strong bite that could crush the bones to devour their prey’s nutritious marrow. Based on their brain cavity research, we can tell that they were clever and could also hunt effectively with the help of their sharp noses and vision. They were ruthless killers and preyed on the herbivorous dinosaurs and other theropods. The most famous of the tyrannosaurs was the Tyrannosaurus rex (T. rex).
2) Sauropods
Sauropods were gigantic herbivorous dinosaurs, some of them almost a hundred feet tall and weighing a hundred tons. They had thick bodies and long necks and tails. Two main types of sauropods were the titanosaurs (vertical neck) and diplodocoids (whip-tailed). Titanosaurs are believed to be the largest terrestrial creatures to ever walk on earth. Since they had hollow bones with air sacs all over their bodies, they were lighter in weight than they looked.
The way they breathed was very effective; they used all the air sacs and the lungs to get huge amounts of oxygen. Another feature that made their large size feasible was the columnar legs. Their graviportal front legs had no toes and bore all the weight. An interesting fact about the sauropods is that they laid many small eggs.
3) Ceratopsians
Ceratopsians were herbivorous horned-face and frilled dinosaurs, including the famous Triceratops and Pentaceratops. Their large frilled horned skull comprised one-third of their body. Size-wise, you can compare them to an average elephant. One of the ceratopsian types, protoceratops, weighed about a few hundred pounds, not a lot compared to the other creatures of that era. Some Asian ceratopsians were as small as a cat. The smaller bipedal ones had quilled tails, while the larger quadrupedal varieties had frills.
4) Eumaniraptora
Eumaniraptoras belong to theropods and include dromaeosaurids (raptors), birds, and troodontids. You must have heard of famous eumaniraptoras like Microraptor, Deinonychus, Velociraptor, Utahraptor, and Troodon. Dromaeosaurids and Troodontis had curved claws on each foot. Raptors were bipedal and had three-fingered hands and large brains, and many were covered with feathers.
5) Theropods
Theropods were large bipedal carnivorous dinosaurs, such as the Tyrannosaurus, Ceratosaurs, Abelisaurs, Allosaurs, Megalosaurs, and the early Triassic period dinosaurs. They were killers and preyed relentlessly upon the herbivorous dinosaurs and other small mammals.
6) Titanosaurs
Titanosaurs were sauropods from the early Cretaceous period. These herbivores and the largest terrestrial beings were found worldwide in all the geographical locations, unlike many other groups. Also, they were quadrupedal and known to have tough scales and defensive feathers. Popular types of titanosaurs are Argentinosaurus and Giraffatitan.
7) Ankylosaurs
Ankylosaurs were the last dinosaurs to roam the earth 65 million years ago, before the extinction event. They had tough body armor, which would even put an M-1 tank to shame. Although, they weren’t quick-witted and were also slow quadrupeds due to their short legs.
These dinosaurs reached their evolutionary peak in the late Cretaceous period when they developed thick armor to survive the deadly predators. Ankylosaurs were distributed worldwide; in fact, the first dinosaur remains ever found in Antarctica were of Ankylosaurs.
8) Feathered Dinosaurs
There were various similarities between the dinosaurs and birds in the Mesozoic era, as some of them had feathers. You can also learn about instances of feathered dinosaurs unearthed around the world, like Sinornithosaurus and Sinosauropteryx in China.
Most of the feathered dinosaurs belonged to the theropods group. Feathers serve the primary purpose of providing insulation to the birds. The jury is still out on how some dinosaurs evolved into the birds we know today.
9) Hadrosaurs
Hadrosaurs were duck-billed dinosaurs and were among the last dinosaurs to exist on earth. These herbivores were gigantic, had strong beaks to graze vegetation, and lots of cheek teeth, up to 1,000 in some varieties. We bet you wouldn’t find them the most attractive of all dinosaurs, given their squat torsos and huge and stiff tails. Some popular duck-billed dinosaurs are Anatotitan, Hypacrosaurus, and Shantungosaurus.
10) Ornithomimids
As the name suggests, Ornithomimids were birdlike but more similar to the wingless ratites, as they couldn’t fly and were rather land-bound. These theropods were omnivores and enjoyed their meat and plant-based diet equally. There’s paleontological evidence to suggest that these were the fastest dinosaurs ever, and could run at the speed of about 50 miles an hour. Some of the earliest ornithomimids were Pelecanimimus and Harpymimus.
11) Ornithopods
Ornithopods (bird-footed) were small or medium-sized herbivorous dinosaurs and were mostly bipedal. They had birdlike hips, feet with three to four toes, and strong jaws and teeth. The ornithopods Iguanodon and Mantellisaurus are among the first dinosaurs to be excavated and named. Due to the fact they were some of the weakest dinosaurs in the food chain, they’re said to roam the woodlands and plains in vast herds in the Mesozoic Era.
12) Pachycephalosaurs
Pachycephalosaurs were two-legged plant-eaters and had an oddly thick skull. However, don’t mistake their skull size for their brains, as they weren’t very clever. Paleontologists believe that the progenitor species were relatively small and roamed in herds. It’s also a common belief that the males in the species used to head-butt each other to assert dominance.
On the other hand, some think that they head-butted the predator’s flanks to protect themselves. Among other pachycephalosaurs known for their distinct skulls were the Wannanosaurus and Stegoceras.
13) Prosauropods
Prosauropods were small to mid-sized plant-eaters that roamed in the present-day region of South America in the late Triassic period. They could walk on two and four legs as well. Some researchers believe that they occasionally ate small amounts of meat with their vegetarian diet. Some of the earliest genera are Efraasia, Camelotia, Plateosaurus, Sellosaurus, Thecodontosaurus, and Massospondylus.
14) Stegosaurs
Stegosaurs were spiked and plated herbivorous dinosaurs having lived in the Late Jurassic to Early Cretaceous periods. There’s still ongoing research on the exact function of the plates; it could have been a way to dispel heat. Some famous stegosaurs were Stegosaurus, Dacentrurus, and Gigantspinosaurus.
15) Therizinosaurs
Therizinosaurs (rake reptiles) were bipedal herbivorous theropods. They had a bizarre appearance, with their potbellies, feathers, lanky limbs, and long claws. Some researchers refer to them as pandas of the Late Cretaceous due to the shape of their claws they use to collect vegetation and fight the predators.
