Deino is based on mythological dragons, and only its name is based on dinosaurs. From bulbapedia:
Origin
Deino is based on a
dragon, specifically an infant form of the
Yamata no Orochi, or possibly even
Zmey Gorynych. Due to its blindness and the fact that it is only found near water in a
cave, Deino may also be based on a
cave salamander.
Name origin
Deino may be a combination of
dino (short for
dinosaur) and
ein (German for
a, and part of the German for
one,
eins). It may also derive from δεινός
deinos (Ancient Greek for
terrible). It may also refer to dinosaurs and other prehistoric animals such as
Deinosuchus and
Deinonychus. Deino is also the name of one of the
Graeae, the three sisters in Greek mythology who shared one interchangeable eye, leaving two blind while one could see.
Monozu may be a combination of
mono (prefix meaning
one) and 頭
zu (head). Its full name literally means "one head".
Source:
https://bulbapedia.bulbagarden.net/wiki/Deino_(Pokémon)#Origin