The thought occurred to me recently that different animals have different body parts that function in different ways., Therefore, it is reasonable to assume that some animals have more joints than others. Which vertebrate has the most?
I’d go with one that has the longest tail.
Since snakes are “all tail”, maybe one of those?
A cursory Google search says that giant pythons can have as many as 600 vertebrae, with all the corresponding ribs and joints.
I think specifically the Reticulated Python is the longest known snake.
The reticulated python (Python reticulatus) of south-east Asia, Indonesia, and the Philippines regularly exceed 6.25 m (20 ft 6 in), and the record length is 10m (32 ft 9.5 in) for a specimen shot in Celebes, Indonesia in 1912.
I suppose that depends on whether we’re counting the interface between two vertebrae as a “joint”. If we don’t, then the answer is probably whatever vertebrate has the most fingers/toes.
And if that’s where we’re going, then we need to ask whether we’re looking at extraordinary individuals, or what’s normal for a species. Most cats, for instance, have 18 toes total, five on each front paw and four on each rear, but polydactyly is fairly common in cats, and they have been observed with as many as 28 toes in total. There might be some animal of some other species with even more.
Since facet joints (between vertebrae) are real, and snakes can have over 650 vertebrae with 8 joints between each vertebra, snakes would seem to be #1 in joint count.
Although when I saw the thread title, the first vertebrate I thought of was Tommy Chong.
I think the question is not “which member of the phylum chordate has the most vertebrae?” but “which member of the phylum chordate has the most joints?”
??
Well, yeah, but if vertebrae count, it’s awfully hard for non-vertebrae joints to compete. Humans have more than most vertebrates, and yet I I only count 71 or 72 (depending on whether you count the two sides of the jaw as one joint or two).
So snakes are unfair to humans when it comes to winning the joint count battle?
This is definitely one of the weirder threads to which I’ve contributed.
Is there such a thing as facet joint denial? 
“Officer, it is just oregano in a hand-rolled.”
I don’t know what the OP has in mind but perhaps one definition that would be useful is the number of joints that have dedicated muscles and tendons to move them independently (unlike the human spine, which although having up to 33 vertebrae, below the neck you can’t move individual vertebrae in isolation). This would rule out snakes, but also require counting bones in a different way.
Based on that definition, the last joint in each finger (but not thumb) is not a joint. At least I can’t bend those without also bending the next joint up. There may be others in the human body that would also not qualify.
I can. And you can probably also bend the other finger joints without bending the last one, and then move the last one while the others stay still.
But if we’re counting by musculature, how do we count joints with multiple degrees of freedom like the shoulder and the hip?
I can.
The shoulder is one joint that can be moved independently of other joints, which meets my criteria. The degrees of freedom doesn’t come into play. Knee, hip, elbow shoulder–all one joint. The wrist and ankle would be more of a problem to define, though. And not sure if the connections between the malleus, the incus, and the stapes are “joints.”
My point was that out spine might be dozens of “joints” but they can’t be effectively used as joints. Due to the musculature they act more like a like a gooseneck lamp than a series of joints.
Come to think of it, each shoulder is at least two joints, because you’re moving both of them when you shrug. Still doesn’t get non-vertebra joints anywhere near vertebrae.