Xenomorph Runner

Height

• 6'-7'2"

Weight

• 200lbs - 320 lbs.

Skin color

• Red-brown

Distinctions

• Quadruped movement
• Domed skull
• Red-brown colored body

The Runner, also known as the Dog Alien, Ox Alien or Scout, is an adult form of the species Xenomorph XX121 spawned from a quadrupedal host animal (such as a dog). Runners, as their name implies, are fast and agile, and can spit acid from their mouths. They are considered "stage IV" Xenomorphs and molt into Sentries once they've secured a hive and a regular source of hosts.
Runners have variously been portrayed as being slightly larger and slightly smaller than typical human-spawned Aliens, differences that no doubt derive from the animal that hosted the creature.
Characteristics
Runners are physically quite different to human-spawned Xenomorphs due to the species' tendency to "inherit" aspects of its host's physiology through the DNA reflex. In the case of the Runner, the adult has most notably taken on its host's quadruped posture, with digitigrade hind legs. Like Drones, Runners have smooth domed carapaces, and they are also one of the few Xenomorphs not to have the distinctive dorsal tubes typical of many other castes. They also have a more barrel-shaped chest, similar to many quadrupedal animals. Their skin is tinted brownish-red as opposed to the more usual grey-black.
While capable of standing and walking on their hind legs, Runners typically remain in their quadrupedal stance when moving and this makes them among the fastest Xenomorphs. They are equally capable of traversing floors, walls and ceilings at speed on all fours. However, physically Runners are not as tough as Drones, relying on their speed and agility to outmaneuver threats rather than strength to overcome them. A Runner also tends to use its tail attack (which stuns the victim) more often than the Drone. They can also run into prey with crushing speed and weight.
Gestation
Unlike other Xenomorph Chestbursters, they tend to be born fully formed and only needs to grow larger. It is theorized that this could be a result of the Xenomorph Chestburster being unable to escape its host's chest cavity at the typical interval (likely due to its higher structural rigidity). Furthermore, the Xenomorph Chestburster is considerably larger than a typical specimen when it finally emerges from the corpse, indicating it had already begun maturing within.
Intelligence
Runners, being generally fewer in number than other Xenomorph types, utilize stealth in their attacks, and have been known to take advantage of their ability to spit acid some distance, often hanging back from targets and striking from range, perhaps behind the cover of assaulting Drones, Runners will often wait until their prey is alone before ambushing them, although they have been known to strike at members of larger groups if an opportune target presents itself.
The intelligence of Runners is often debated. It has been theorized that Xenomorphs gain intellectual/mental as well as physical traits from their host, and that this may influence the adult creature's level of intelligence and instinctual behavior.