Tough break, Time Thief! I don't intend to stand by and let the world be pulverized by dinosaurs just so you can gain more power! 
DC Special #27 is an issue of the series DC Special (Volume 1) with a cover date of May, 1977.
Synopsis for "Danger: Dinosaurs at Large!"
Captain Comet and Hawkman sit in the Justice League Satellite discussing how they sometimes feel out of touch with other heroes when a comet blazes by and disappears as quickly as it came. In 2056, the same rock almost hits the spacecraft of Tommy Tomorrow and Brent Wood as they are flying a to Vega IV to stop an epidemic. The comet pulls Tomorrow and his starship into Earth's past, where he and his crew encounter dinosaurs, and also opens a time-rift that allows dinosaurs into the 20th century.
Hawkman unilaterally elects Comet an honorary member of the Justice League and asks him to stay on monitor duty as he heads down to Earth to stop the carnage. on the monitors, he sees a costumed figure that's new to him and assumes that Chronos is a hero rather than the time-traveling villain he is. When he goes to Earth to save him from a brontosaurus, telepathy tells him of Chronos' true intentions. He is responsible for opening a rift in time, allowing the ancient animals to terrorize Earth: he tried to capture the comet for its unique abilities but missed and is now trying to retrieve it.
In prehistory, the comet's radiation has evolved a T-Rex into an intelligent being who names himself Tyrano Rex. The malevolent dino tries to kill Morrow, Wood, and the doctor they are transporting to Vega IV—they need the comet to return to the future but Tyrano worships it as a god.
Captain Comet's vast mental powers allow him to close the hole in time with great concentration but before he does, Tomorrow's craft crashes into the present day, with Tyrano in tow. Chronos steals the comet and as it leaves proximity to Tyrano, he reverts into a normal dinosaur which Captain Comet throws back 100 million years to the past. In the chaos, Chronos manages to escape and Comet takes the stranded time travelers back to the Satellite where Superman says he can find a way to return them to the 21st century.
Appearing in "Danger: Dinosaurs at Large!"
Featured Characters:
Supporting Characters:
- Justice League of America
- Aquaman (Cameo)
- Black Canary (Cameo)
- The Flash (Cameo)
- Green Lantern (Cameo)
- Hawkman
- Superman
- Wonder Woman (Cameo)
- Dr. Schmidt (2056 scientist)
- Brent Wood
Antagonists:
- Chronos
- Tyrano Rex (First appearance)
Other Characters:
Locations:
Items:
Vehicles:
- Space Cruiser
Concepts:
Notes
- According to the text page in this issue, Tommy Tomorrow has traveled from 2056 to the present in this story, from sometime between Action Comics #212 and Action Comics #226.
- The only time that Comet uses his Justice League membership is during a three-part Secret Society of Super-Villains story in DC Special Series #6. He also spontaneously helps several Leaguers in Super-Team Family #13 and appears at the wedding of Jean Loring and Ray Palmer in Justice League of America #157.
Trivia
- Not all pre-historical animals seen in this story are actually contemporary: A mastodon can be seen when Tommy Tomorrow is stranded 100 million years ago; however, mastodons didn't appeared in the real world before 4.5 million BC. It was a side-effect of Chrono's comet. Pterodactyls and mastodons aren't dinosaurs: the term "dinosaur" is restricted to just those reptiles descended from the last common ancestor of the groups Saurischia and Ornithischia (clade Dinosauria, which includes birds), and current scientific consensus is that this group excludes the pterosaurs (which includes pterodactyls).
See Also