Now Pelyon, that great fin-backed lord
Who raised the solar sail upon his spine
To warm himself at dawn and hoard
The sun's heat like a living solar shrine—
Pelyon had been master of the land
Through all the later Carboniferous age:
Dimetrodon's great bulk held proud command
Of every hollow and of every stage
Where synapsid life had tried to be—
The sprawling gait, the cold blood of the night,
The morning sunning to gain energy
Before the hunt: a slow but proven right
Of conquest over those who had no sail,
No way to warm their blood except by sun,
No strategy but wait until the stale
And frigid morning finally was done.
But Pelyon's dominion was a bridge—
A first attempt at solving the great need
For warmth—the sail was answer to a ridge
Of cold that warmer flesh could supersede,
And in the later Permian there arose
From Synaps' lineage a different kind
Who found the answer not through dorsal shows
Of spine-fin but through working of the mind
And body into something new: Theraps—
The therapsid law of upright walking—
Stood from the ground and closed the sprawling gaps
That Pelyon's ancestors kept stalking
With elbows out and belly near the earth.
Theraps pulled his legs beneath his mass
And stood more upright—and with every birth
Of that new posture, every stride would pass
More energy to speed than to the fight
Against the ground's own gravity—the ones
Who stood upright could run both day and night
With lungs not compressed by their own tons
Of body pressing down on them: for when
You sprawl, the ribs that carry lungs must bear
The body's weight with every stride, and then
The sprint and breathe become a choice—compare
The crocodile who cannot sprint for long
Before he gasps—the sprawling gait binds breath
To step, so every stride must be the strong
One traded for the air beneath.
But Theraps stood above the ground's demand
And breathed while running—lungs released
From duty to the ribs' supporting hand—
And this was more than merely increased
Speed or endurance: this was the first step
Toward something warmer, something that could run
Through cold of night and early morning's slept-
Through chill and still be hot enough to hunt.
Theraps found new arrangements for the jaw—
The dentary bone grew larger, grew
To dominate the face, and teeth with more
Complexity replaced the uniform row
Of simple cone-teeth that his forebears kept:
Incisors for the grip, a canine fang
For piercing deep, and cheek-teeth that adept
At grinding followed as the jaw-hinge sprang
Into a new position—Theraps moved
Toward the mammal mouth before the name
Of mammal had been coined, and he improved
Each generation toward the goal of flame
Within the body that would never need
The sun to kindle it—internal heat
That Cynos would achieve, that final creed
Of warm-bloodedness where cold and heat compete
No longer—but that came later. For now
Theraps walked the Permian land in pride,
His uprightness a covenant, his vow
To be not passive sun-warmed but inside-
Warmed by the burning of his food, the slow
Combustion of the prey he ate to run
Through every night and morning's cold below
The horizon of the rising sun.
The dinocephalia rose as great
And heavy-headed masters of the plain—
Theraps' largest children, who create
A living battering ram that drove the grain
Of fear through every creature on the land—
Thick skulls for head-butting, wide and stout,
They ruled the middle Permian firsthand
Before their own extinction's sudden rout.
And Theraps branched in many directions wide:
The hunters and the hunted, large and small,
The armored and the swift and those who tried
The burrowing life beneath it all.
But all of them agreed on this one truth:
The sprawling gait was ending, and the age
Of upright walking had arrived—the proof
Was written in each trackway on the stage
Of Permian red desert: prints that show
The feet beneath the body, not spread wide—
The law of Theraps told the world: below
The body is where limbs were meant to guide.
Honor the therapsid who stood tall
And turned the solar sail to inner flame—
Who gave the mammal's gait to one and all
And wrote upright into life's own name.