West of Eden is a 1984 science fiction novel by Harry Harrison, followed by two sequels: Winter in Eden and Return to Eden.Set in an Alternate History where dinosaurs never went extinct (outside of North America, where modern mammals and eventually humans evolved), the story centers around the conflict between humans and the Yilanè, a race of intelligent amphibious reptiles. The main character, Kerrick, is a human who was raised by Yilanè.
Alternate Prehistory: The K-T extinction event never occurred; the dinosaurs are still around, and intelligent mosasaurs rule most of the world, with mammals abundant only in North America.
Badass Boast: The scientist Ambalasei thinks rather highly of herself:
"Fat gilded-beetle to be crushed! Decayed worm from the lowest dungpit! Before you stands Ambalasei highest of the high, eistaaTranslation Leader of a city. of science, intelligence of the world, possessor of infinite powers. I should sentence you to death for your ill-speaking. I consider that now."
Bizarre Alien Biology: Intelligent mosasaurs that reproduce like seahorses. Their bio-engineered tools are even more bizarre: living dart guns, microscopes that are actually highly modified frogs, squid and icthyosaur vehicles...
Blue and Orange Morality: The Yilanè's Bizarre Alien Biology leads to them having a strange moral compass. For example, lying is impossible (and the concept never even occurs to them until Vaintè learns about it from Kerrick), and they are absolutely loyal to their communities to the point of dying upon exile; exiles who don't seize up and die are completely insane by Yilanè standards.
Call A Dinosaur A Smeerp: Nearly all the dinosaurs depicted are referred to by their Yilanè names ("epetruk" for T. rex, "nenitesk" for Triceratops and so on.)
Guilt-Free Extermination War: Explored. The majority of Yilanè just see massacring ustuzou (humans) as pest control, and most humans return the favor. Vaintè at first considers useful ustuzou like Kerrick to be worth keeping around as tools (and later becomes psychotically obsessed with their destruction), but the Daughters of Life recognize ustuzou as sapient beings worthy of life and respect. Kerrick (after rejoining the humans) rejects the position that Yilanè are Always Chaotic Evil, and draws a demarcation between Yilanè who are killing humans and Yilanè who humanity can coexist with.
Interspecies Sex: "Romance" isn't the right word for it, but we don't have a simple trope for interspecies rape.
Lady Land: The Yilanè — females control politics, science, and the military; males are artisans, poets and brood mares.
Language Of Truth: The nature of Yilanè language and thought processes makes them incapable of lying...until Vaintè discovers the concept after seeing Kerrick do it.
Lizard Folk: The Yilanè, human-sized bipedal mosasaurs.
Living Ship: Yilanè sail the seas using genetically modified icthyosaurs with a compartment in their dorsal fin. They also have modified squid as smaller boats.
Living Weapon: ...specifically a genetically modified lizard that shoots poisoned darts.
Mr. Seahorse: Yilanè reproduce in a similar manner to, you guessed it, seahorses.
My Country, Right or Wrong: Hardwired into Yilanè biology. If a Yilanè is exiled from its city, its body shuts down. Some of them, however, are loyal to something other than their city, and their shutdown reflex will occur in response to different stimuli. The Yilanè are not quite sure how to cope with this.
Organic Technology: Everything used in Yilanè society is a product of genetic engineering. Even the ancient Yilanè began by hunting using living crabs instead of stone tools, though one Yilanè scientist suggests that early on, the Yilanè did indeed use "artefacts."
Starfish Aliens: The Yilanè are somewhat humanoid in shape, but quite different in physiology and psychology. The main conflict of the trilogy stems from them and humans being mutually repulsed by their differences.
Starfish Language: A complicated combination of spoken words, positioning/gestures and color signals, described as so difficult that many Yilané never even get the hang of it.
Thunderbolt Iron: The knives Kerrick and his father wear are made of "skymetal."
Translation Convention: A given, as the English language doesn't actually exist in the setting. The Yilanè's Starfish Language is sometimes rendered with odd syntax ("Fish of great size abound. Desire to catch/eat. Will small/soft go with us?"), especially in Return to Eden.