Dromaeosauridae

Utahraptor ostrommaysorum, a dromaeosaurid

Dromaeosauridae is a family of bird-like theropod dinosaurs, closely related the Troodontidae family and belonging to the Deinonychosauria clade. The name Dromaeosauridae means "running lizard," derived from the Greek word "dromeus" meaning "runner."

Dromaeosaurs first appeared during the late Jurassic period in the form of primitive Maniraptors, and died out in the late Cretaceous period 66 million years ago. Their widespread fossils have been found in every continent except for Australia, suggesting that dromaeosaurs were a highly successful species of dinosaur.

Dromaeosaurs belong to the broad group of medium-sized theropod dinosaurs referred to as the "raptors," meaning "birds of prey."

Characteristics

General characteristics

Dromaeosaurids were a group of medium-sized theropod dinosaurs. They peaked during the Cretaceous period. They were considerably fast, but less so than is portrayed in movies, reaching speeds of around 25-50 mph when sprinting.

Their body-plan consisted in a relatively large skull, serrated teeth, narrow snout, and forward-facing eyes, that suggested binocular vision. Futhermore, they had a S-shaped neck, like many other theropods, and a relatively short and deep trunk. Like other maniraptorans, they had long arms, that could be folded against the body, like modern birds do, and large hands with three fingers, the hands facing each other. Their tail were long and stiff tails, with bony tendons.  Their most common characteristic was a retractable second toe with sickle-claw on each foot. They used to hold this toe high to the ground, in a hyperextended position, as they walked on the other two toes.

All of the dromaeosaurids were covered in feathers. Their entire body, except the snout, hands, and feet were covered in short stage v feathers. Their arms and tail, instead were covered in longer, more specialized feathers, called remiges (on the arms) and rectrices (on the tail). The first fossil found with evidence of feathers was the Sinornithosaurus millenii.

Size

A Size Comparison of many Dromeaosaurids

Dromaeosaurids were small-to medium-sized dinosaurs, the smallest being Mahakala (at 0.70 m - 2ft) and the largest being Utahraptor (up to 7m - 24ft).

Behavior

Dromaeosaurids may have been social animals that lived in packs, but given that no modern birds of prey have complex social groups, only living together to reproduce and rear young, this is not regarded as scientific fact as of now. However, Deinonychous fossils have been found together, near a Tenontosaurus fossil, suggesting that they hunted together. This could mean also that they had a sort of unorganized social behavior, like modern Komodo Dragons. But recent discoveries like the extensive dromaeosaurid tracking found in 2007, in Shandong, China, suggested that at least some species lived in social packs, living and hunting together.  

Intelligence and senses

Studies on their brain-size ratio suggested that Dromaeosaurids were some of the smartest dinosaurs, second only to Troodon. Their intelligence may have a little higher than the average rabbit, but did not have the same cognitive abilities of a domestic dog.

Their vision was very good, as they had binocular vision, being able to notice distances, and most likely even colors, as modern birds do.

Also studies on their olfactory bulbes revealed that they had similar olfactory ratios to those of tyrannosaurids, suggesting that they had an acute sense of smell.

Classification

• Xiaotingia zhengi;
• Pyroraptor olympius;
• Mahakala omnogovae;
• Neuquenraptor argentinus;
  • Microraptor gui
  • Sinornithosaurus millenii
  • Deinonychus antiirhopus
  • Velociraptor mongoliensis
  • Balaur bondoc
  • Utahraptor ostrommaysorum

  1/6
• Shanag ashile;
  • ​Unenlagiinae:
    • ​Rahonavis ostromi;
    • Buitreraptor gonzalezorum;
    • Austroraptor cabazai;
    • Unenlagia comahuensis ;
  • Microraptorinae:
    • Graciliraptor lujiatunensis;
    • Hesperoryncus elizabethae;
    • Tianyuraptor ostromi;
    • Zhenyuanlong suni
    • Microraptor gui;
    • Sinornithosaurus millenii;
  • Eudromaeosauria:
    • Dromaeosaurinae:
      • Achillobator giganticus;
      • Atrociraptor marshalli;
      • Dromaeosaurus albertensis;
      • Utahraptor ostrommaysorum;
      • Deinonychus antirropus
      • Dakotaraptor steini
    • Velociraptorinae:
      • Linheraptor exquisitus;
      • Bambiraptor feinbergi;
      • Tsaagan mangas;
      • Saurornitholestes langstoni;
      • Adasaurus mongoliensis;
      • Velociraptor mongoliensis
      • Velociraptor osmolkae

​See also

Troodontidae