Twice-Told-Tales: Danger - Dinosaurs at Large!

It is the summer of 1977 on Earth-One, and the summer of 1968 on Earth-Two. Each world finds themselves plagued by disturbances in time, with humans shifted from the centuries they were born into past eras, with monsterous dinosaurs taking their place in the 20th century. The cause for these odd occurences on parallel worlds is due to green caped time-masters wearing white masks, genetically modified opponents they must face, and cosmic radiation due to celestrial objects. These three factors conspire into strange tales.

On Earth-Two, the villian known as Psycho-Pirate secretly manipulates a fallen felon named Gat Benson, using remnants of the green Starheart meteor to transform him into a giant. Causing terror due to both his appearance and radiation he emits, Gat attracts the attention of the Justice Society charter member known as the Spectre. 

While attempting to use time-suspension and altering time cycles in order to calm an anxious crowd, Spectre inadvertently teleports some citizens of Gateway City to America' colonial era and prehistoric era. While attempting to retrieve these innocents, he exposed some of them to predactory pterodactyls and draws a tyrannosaurus rex back to the present. After battling the beast, Spectre returns it to its era.

On Earth-One, the villian known as Chronos secretly used his temporal technology to retrieve a comet from the future, a comet with special powers over time. Inadvertently, the comet is pulled along with it the crew of future Colonel Tommy Tomorrow into a prehistoric era, where they faced predactory pterodactyls and a tyrannosaurus rex that mutated into the humanoid Tyranno Rex. 

While using his vessel to transport his crew and the comet through a portal back to the future, they end up meeting Captain Comet. As an honorary member of the Justice League, he was working with other Leaguers to subdue the time-displaced dinosaurs. When Tomorrow's vessel arrives in the 20th century, in includes a stowaway in Tyrano Rex, seeking to reclaim the comet. During a battle with Captain Comet and Chronos, Rex in transformed back into a T-Rex, then sent back to its own time.

The villains, Psycho-Pirate and Chronos, are each brought to justice by the heroes with the help of Tommy Tomorrow and Jim Corrigan. While the green meteor globe on Earth-Two is dropped and thus smashed to pieces, the comet is destroyed as well. The Globe was tied to Earth-Two's Green Lantern and his power source, while the comet quite possibly was the Earth-One version of the comet that Lantern's old foe Vandal Savage gained his immortality from centuries earlier on his native world. And while their schemes with these extraterrestrial objects failed, Chronos and Psycho-Pirate would extract from this situation the means to gain greater manipulations over that which they craved. For Chronos, actual time travel that he would use versus the World's Finest Team of Superman and Batman, and for Psycho-Pirate, control over the emerald energy of the meteor through Green Lantern.