“Why did the dinosaur cross the road?”/“Because chickens hadn’t evolved yet.”

“Why did the chicken cross the road?”/“To get to the other side” is a classic riddle from the 19th century. A dinosaur version is:
 
Q: Why did the dinosaur cross the road?
A: Because chickens hadn’t evolved yet.
       
The joke has been cited in print since at least 1990.
 
     
21 January 1990, Edmonton (Alberta) Journal, “Just Joking,” pg. F6:
Why did the dinosaur cross the road? (Because chickens weren’t invented yet.)
- Glen Sergy, Edmonton
   
5 August 1990, Newsday (Long Island, NY), “Smiles,” Kidsday:
Why did the dinosaur cross the road?
Because there were no chickens at that time.—Christopher Burke, Seaford
 
Google Books
Kids’ Funniest Jokes
Edited by Sheila Anne Barry
New York, NY: Sterling Publishing Company, Inc.
1993
Pg. 80:
Why did the dinosaur cross the road?
Because the chicken hadn’t been invented yet.
JENNIFER SMITH, 8
     
Google Groups: rec.humor
Canonical List Of Animal Humor 1/6
Natural Korn Shellers
11/5/94
(...)
Why did the dinosaur cross the road?
Chickens hadn’t evolved yet.
 
Google Books
Dinosaur Detectives
By Judith Bauer Stamper
New York, NY: Scholastic
2001
Pp. 12-13:
“Why did the dinosaur cross the road?”
 
“I don’t know. To get to the other side?” D.A. guessed.
 
“No, because the chicken hadn’t evolved yet!”
 
Twitter
Elle Viane Sonnet‏
@awkwardgirl
Why did the dinosaur cross the road? ... Chickens hadn’t evolved yet.
6:27 PM - 2 Jul 2008
 
Twitter
keithcarberry‏
@keithcarberry
My sons corny Popsicle joke: Why did the dinosaur cross the road ?  Because chickens hadn’t evolved yet…Crazy stuff Dads do for kids 😊
12:10 AM - 2 Aug 2008
 
Google Books
3000 Jokes, 2997 Laughs
By Mike Haskins
London, UK: Portico
2017
Pg. ?:
Q: Why did the dinosaur cross the road?
A: Because the chicken hadn’t evolved yet.