Imagination is not the sine qua non of sapience, but it's one of the better traits. And taking apart this lizard is, in many ways the fount of imagination. Its body is a story written in genetics: a story of the sorts of people you once knew, and the way that their ideas and their idiosyncrasies developed when left to themselves for millennia. 

This lizard is not a hunter: its ecology appears derived around devouring fungus, but its body contains elements of zinc and titanium in quantities that necessitate being part of its diet in substantial quantities. This creature can only sustain itself in an ecosystem where historically valuable and rare metallic elements are so commonplace that they suffuse the stationary growth of the region. Can you imagine the planning that went into making this work? The care in timing necessary to have a species like this become emplaced? Somebody probably uttered the word "synergy" at least once in a board room. 

Trace radioactive elements, primarily some amount of curium are present in the creature. Curium is an odd thing to find, since as far as modern science was aware when you last checked, it could only be made synthetically (though was potentially stable in some isotopes once made in this manner, leading to its use in the Sojourner, Spirit, Opportunity, and Curiosity Mars rovers as a power source). This implies that there is some kind of intentional nuclear reaction occurring or that occurred in the environment. The time is impossible to place since the half-life of stable curium is in the tens of millions of years, so detecting whether this is floating around from something somebody did yesterday or a thousand years ago is a rounding error. 

The poison is a powerful tranquilizer. This, at least, functions as you expect, it's just a very large and concentrated dose representing a substantial amount of resources expended by this creature to produce and maintain in such quantities. It raises some questions about the sorts of tools humans in the region might possess: a human who built a dart gun using these spines could fell another human with one shot almost instantly, and you've seen the effect on the region's great cats already. 

Scales are extremely hard, capable of being used to cut or shape rock without chipping, not surprising given the heavy metals present in the body. The cat seemed to have little trouble, but what that's really saying is that the creatures here are evenly matched with each other but their baseline is extremely high capability to endure or manipulate their environment. This is the kind of thing that someone somewhere once sketched on a whiteboard to explain how they were going to find safety in an irradiated zone without thinking about the more subtle implications of a cave system with creatures whose bodies can break rock. 

The creature was cold-blooded, which may explain why it was able to direct so much energy to things like the venom and scales. This implies easy access to places to rest, likely an underground heat source. Probably nuclear? Was this part of the breeding as well, to ensure that the creatures wouldn't spread out of the region? Give them incredible power, ensure they're dependent on a source of energy that can't easily be found elsewhere and would render them highly lethargic if they ever tunneled too far away from their designated zone? This one was close to the surface though. Maybe on the edge of its territory in that case?