Interspecies Conflict/Pack park 2
4 male Xenos (380kg each) vs allosaurus
2 Arcturus wolves vs utahraptor
Pleistocene polar bear vs arctotherium
Megalania vs titanoboa
4 Arcturus wolves vs Pleistocene polar bear
2 male Xenos 380kg each vs arctotherium
Same park but different predators how would the ecosystem function
I'm removing gray wolves lions & tigers & deinonychus & crocodiles
4 male Xenos (380kg each) vs Allosaurus: The Allosaurus will weigh over 6-7 times as much as a single Xeno. Allosaurus was a large theropod with good hunting skills and a huge bite (sharp blade-like teeth for removing flesh). A single bite from Allosaurus can kill a Xeno, but the cats can prevail with a quick, coordinated attack. The Xenos will need to leap onto an area of Allosaurus where they will be relatively safe from a counter-attack, and that won't be easy. The Xenos' bites are deadly, but they might not make enough headway with a huge dinosaur that's violently resisting before their numbers are reduced. Probably close to 50/50 (slight edge to Allosaurus), unless the Xenos are the upgraded "sentient" ones.
2 Arcturus wolves vs Utahraptor: The Utahraptor will weigh a little over 70% more than each Arturus wolf. The wolves technique of landing quick bites from 2 sides until wearing the quarry down (then grabbing on tightly to pull it down) won't work as well on a Utahraptor as it will on a herbivore of similar size, but their lateral quickness may enable them to succeed on occasion. The Utahraptor has good leaping and turning ability, and has a variety of weapons at its disposal (strong jaws with sharp teeth, grabbing claws on its forelimbs, long claws to kick/slash with). Utahraptor will probably have the slight edge unless the Arcturus wolves are upgraded to "sentient" status.
Pleistocene polar bear vs Arctotherium: Using the top estimates generally considered reasonable for each bear, the Pleistocene polar bear will weigh about 70-75% the weight of the Arctotherium. The Arctotherium (South American short-faced bear) was closest in kin to the spectacled bear (but I'm not saying it was exactly like a scaled-up spectacled bear). I don't consider spectacled bears to be on par with polar bears pound-for-pound due to how each bear uses it muscles and what each bear hunts (or eats), but the Arctotherium has too much of a weight advantage here. I would likely favor the Pleistocene polar bear once it exceeded about 80% of the Arctotherium's weight, and I would heavily favor it at parity. Decent fight, but the Arctotherium has a slight edge.
Megalania vs Titanoboa: These animals were probably similar in weight (each over a ton), but estimations for Megalania varied quite a bit. This would be somewhat similar to Komodo dragon vs rock python (similar in weight; snake close to twice as long). On land Megalania would have the mobility advantage and would have a chance to win. Megalania's bite could rip into Titanoboa, but the bite (with possible bacteria/venom like the modern Komodo dragon) probably wouldn't have the same effect on a reptile as it would on a mammal. It would need to cause enough damage with its bite to disable the snake before its coils wrapped it up. However, if Megalania battled Titanoboa in water, the snake would have a huge advantage. It would wrap around Megalania, and the giant lizard would have no real way to free itself (this would be true on land as well). Overall edge to Titanoboa.
4 Arcturus wolves vs Pleistocene polar bear: The Pleistocene polar bear will weigh close to 4 times as much as each wolf. This will be similar to 4 grey wolves taking on a black bear, but the Arcturus wolves have enhanced attributes (speed, bigger bites, etc.). The wolves should have the ability to make this a close battle if they work as a team, and they will probably be favored.
2 male Xenos (380kg) each vs Arctotherium: The Arctotherium will weigh twice as much as both Xenos combined. Normally 2 big cats won't have the strength to gain positioning against a bear 4 times their own weight, but the Xenos are somewhat enhanced (long teeth, high bite forces, long claws), and can cause a lot of damage leading up to an attempt for a finishing throat-bite. The giant bear's paw usage will enable it to defend itself well (even at close quarters), and its endurance will be solid. The Arctotherium will likely have the edge unless the Xenos are the "sentient" versions (then they will probably be favored).
Park question: I'm assuming you mean the park Lawrence mentioned in "Pack Park" from 7/24/15. Any answers or assessments involving non-real creatures are guesses (not my strong suit).
Xenofelis: Will likely be the dominant entity in the park. Will be able to defend against other predators and predate upon anything as long as their numbers are great enough.
Arcturus wolf: Will likely be the 2nd most dominant entity in the park. Will be able to defend against other predators (but will need at least a 2-to-1 advantage to compete with Xenos) and predate upon anything as long as their numbers are great enough.
Hyaenodon: Hyaenodon gigas was the largest Hyaenodon species, and may have weighed close to 500kg. It had a very long set of jaws and a bone-crushing bite. Will lose face-to-face battles with Daeodon, Arctotherium, Titanoboa, and Allosaurus. Close battle with Megalania, but will probably lose more times than not. Will be able to predate upon Dryosaurus, any deer, and zebra. All other herbivores will probably be too large unless a large group is hunting. Will look to seize prey items in its massive jaws after running them down, and will likely crush and tear its victims in its teeth.
Daeodon: Daeodon was a giant mammal that somewhat resembled a warthog, but was the size of an American bison. It had a very strong bite, powerful neck muscles, and protruding tusks. It may have commonly scavenged. Would be formidable enough to defend itself against, but may fall victim to an occasional Megalania ambush (may have repelled Megalania face-to-face). Won't defeat Arctotherium in a serious battle, but may drive the huge bear away in a realistic encounter. Will coexist with other herbivores for the most part, but may have occasional conflicts with them. Its huge bite will be its primary tool for offense, but its tusks will come into play in any encounter.
Megalania: Megalania was a giant monitor lizard (but stockier) with similar attributes as modern-day ones (tough hide, sharp teeth, whip-like tail), and may have had a toxic bite like today's Komodo dragons do. Estimates for its size vary, but the upper-end ones place it at close to 1200kg. Will likely ambush prey. Assuming its bite is toxic, it can kill any mammal in the territory with a deep bite, but may not prevail in many face-to-face encounters with the more formidable ones (Daeodon, Titanoboa, hippo, Arctotherium, and certainly Allosaurus). May use the same techniques as the Komodo dragon (ambush, deliver a bite, wait for prey to expire or become defenseless, rip open victim's body with sharp teeth). As with the Komodo dragon, can potentially kill mammals much larger than itself (komodos have killed water buffalo). Elephants and rhinos will repel it with ease, but can be threatened by an ambush. The larger dinosaurs should be safe.
Titanoboa: Huge snake with characteristics similar to an anaconda, but twice as long and several times heavier. As big around as an oil barrel. Ambush predator; at home in the water. Won't bother Arctotherium, and will need to avoid Allosaurus. Will endanger most animals close to its own weight near the water's edge, but won't have the same level of success against them on land. Will primarily predate upon any hooved animals that come to the water's edge or the young of the larger animals that come to drink.
Arctotherium: This huge bear (over 1500kg; 2m at the shoulder) was probably a scavenger as well as a hunter. Would be large enough to defend itself (on most occasions) from any big cat or big cat group. Would need to avoid Allosaurus, as it would not be large enough to fight one off or mobile enough to avoid its attack once it came close. Would be large enough to fight off a saltwater crocodile in the water as long as the water wasn't too deep. May come into occasional conflict with humans with both parties taking the role as hunter from time-to-time. Will bully smaller animals from kills, and will hunt cervids, maybe zebra, and possibly Dryosaurus. Would be a good match for a hippo, but won't likely attempt to tackle one (especially near the water). Won't be able to overpower some of the larger prey items (elephants, rhinos, Stegosaurus, Ankylosaurus).
Pleistocene Polar Bear: Would live in colder regions, and would only have possible contact with gray wolves in regards to competing predators. Only a very large pack of wolves would be able to deter it from its daily routine. It would prey upon elk and moose primarily, and would possibly catch the Alpine ibex on occasion (probably won't encounter other herbivores). Human abodes won't likely be near, so interaction won't be common.
Allosaurus: The most dominant single predator in the park. Fearsome jaws, serrated teeth, huge appetite. Will have no trouble from other predators on most occasions. May bully other predators from their kills. Can potentially kill an subadult elephant, but an adult African elephant will weigh twice as much and will have a very good chance to repel the attacking theropod. The Apatosaurus (formerly known as Brontosaurus) will be targeted quite often, but a large one can defend itself from Allosaurus on occasion. A large white rhino will give an Allosaurus a tough battle, and can injure the dinosaur with its horns. Close fight at close weights. Allosaurus preyed upon Stegosaurus, and would do so here. Stegosaurus was armed with a 4 long spikes on its tail, and these could be swung at an enemy with great effect. A full-grown Stegosaurus would be able to defend itself from an Allosaurus more times than not, but would need to worry when the theropod approached. Dryosaurus and hippopotamus would be potential prey items as well. Ankylosaurus was well armored and had a club of bone on the end of its tail that could be swung with great force. An Allosaurus would risk broken bones in such an encounter. Other animals could be overpowered by Allosaurus, but would be too fast for the dinosaur to catch without an ambush (deer, zebra, elk, etc.). Humans will need to avoid it and take cover.
Humans (Bronze Age): humans would have weapons like swords, spears, axes, etc. Will need to use their intelligence to assess the dangers and opportunities around them. Will likely hunt cervids for food. Will need to have areas of "safe harbor" to retreat to, as even armed humans will be vulnerable out in the open.