I believe I do have a timeline of events that you might find elucidative.
Russ learns Newt’s name, which leads to a discussion of amphibians and, in particular, why turtles are not amphibians. Newt gives him a brief scientific explanation of the difference between reptiles and amphibians, but Russ does not want to hear more.
Instead, Russ asks Newt for a story about Teenage Mutant Hero Turtles. Having been informed that the turtles names are Michelangelo, Raphael, Donatello and Leonardo, Newt tells Russ a story about turtles in Renaissance Florence.