What happened to the creatures that remain in the present? We know Rex, Sid and Nancy are Abby's pets. But other? Look my theories and say yours!
Oliver Leek's creatures
I have two ideas.
1. If ARC don't go to save creatures, Future Predators and Smilodon flees, climbing on a roof. The Smilodon attacks humans, ARC found it and sent it through anomaly. Four FP (Future Predator) returns, another be sent through anomaly or killed by ARC. Raptors killed one Mer Creature, another attacks Arthropleura, but FP and scorpion killed Arthropleura. Mer creature later stomped by Scutosaurus, one Raptor falled and get leg trauma. One FP killed by raptor, another - by scorpion. Later raptors and future predators killed scorpion. Later creatures died of starvation.
2. If ARC go to save creatures, future creatures be killed, extincted - sended to anomalies. Smilodon be in ARC to 4.7, in 4.7 it sended to anomaly. Raptors sended in 3.10 or 4.1. Scutosaurus, Arthropleura, Scorpion - i don't know.
One Hyaenodon
We know one Hyenodon falled to death. But possibly it stand alive and live in ARC! It lives in ARC all 5 season and sended only later Primeval series.
Spring-heeled Raptor
I think it owned by ARC and live all 5 season and later. It possible sended in anomaly or live all life in ARC. But possible it died of PBFD virus (birds lost feathers of this sickness and dies).