Even the river lords heard the ocean's call.
In the Jurassic seas, while Plesios flew
On four flippers through the deep, and Ichthyos' tall
And dolphin forms still hunted the Tethys blue—
A stranger arrived: the children of Cruros,
The crocodilian kin, the river dragons
Who had survived the end-Triassic's bruise
By staying small and humble—these were the wagons
Of a new marine experiment.
Thalattosuchus—the sea-crocodile—
Was Cruros' answer to the ocean's rent-
Free niches, and his children swam in style
That no one expected from a crocodilian:
Fully marine, with flippers where the feet
Had been, with a fish-tail where the reptilian
Tail had flattened to a vertical beat
Of the water—Thalattosuchus had become
A sea creature, streamlined and salt-tolerant,
With salt glands near the eyes that freed him from
The freshwater dependency—an entrant
To the open ocean from the river-bank.
The Metrion clan—the metriorhynchids—
Were the most marine of all: their rank
Among the crocodylomorphs was the kids
Who ran away to sea and never returned.
Their legs had become paddles, their tails bore flukes,
Their skin had lost the armor scales that burned
With weight in open water—these rebukes
Of every crocodilian convention
Swam the Jurassic seas as sleek and fast
As any marine reptile: the invention
Of the sea-crocodile—a form that passed
Through the Jurassic waters like a dark
And toothy torpedo, catching fish and squid
In jaws that still bore the crocodilian mark
Of the long snout and the interlocking grid
Of teeth—but everything else was ocean:
The body smooth, the limbs reduced to fins,
The tail a propulsive engine of locomotion
That drove them through the surface and the dim
Below with equal ease.
They breathed at the surface—
Lungs, not gills, the amniote's inheritance—
And they may have borne live young, the purposive
And marine adaptation's final dance
With the land abandoned.
For a little while
In the Jurassic's middle age, the seas
Held crocodilians who had crossed each mile
Of evolutionary distance—from the trees
And rivers of their Cruros-ancestry
To the open ocean, fully marine,
Hunting alongside Plesios and the dynasty
Of Ichthyos—three lineages in the marine
Republic, each from a different branch
Of Sauros' family tree: Ichthyos from the deep
And ancient diapsid line, Plesios from the ranch
Of Paraps' turtle-kin, and now the creep
Of Cruros' river-children to the brine.
The teleosaurids—the other clan
Of Thalattosuchus—kept closer to the line
Of shore, like the gharial in a later plan:
Long-snouted, fish-eating, coastal hunters
Who patrolled the Jurassic shorelines and the reefs
In the manner of their river-hunting grunters
But adapted to the salt—the ancient griefs
Of the end-Triassic had pushed them to expand
Beyond the rivers that their fathers knew,
And the Jurassic sea was close at hand
With fish enough for every hungry crew.
The Thalattosuchus clan would fade
Before the Cretaceous dawn—the fully marine
Metriorhynchids leaving no cascade
Of descendants to the later scene—
Their experiment complete, their lesson taught:
That even the most dedicated river-dweller
Can hear the ocean's call and be caught
In the sea's embrace—that every cellar
Of the evolutionary house connects
To every other room, and the crocodile
Who seems forever bound to the river's text
Can rewrite himself in the ocean's style.
For the sea turns no one away who comes
With lungs and will and the willingness to change—
The Jurassic ocean beat its drums
For the river dragon who expanded his range
To the horizon—and found room.
Honor
The thalattosuchians: the crocodile-kin
Who went to sea and earned the ocean's honor
Of a place among its hunters—the genuine
And fully marine crocodylomorphs who proved
That no lineage is locked to a single home,
And the river's child, when the river-banks have moved,
Can make the open ocean into a poem.