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The Last Marine Crocodillian

October 30, 2014

Ikanogavialis

A story about the Murua Gharial, the world’s last truly marine crocodillian.

***

Midday passes on the shallow seas around Woodlark Island. Beneath the greenish-cyan surface, a mixed landscape of fringe reefs and seagrass plains spreads on for miles in the shallows, the coral formations seemingly producing fortresses, around and above the marine grasslands, like a bizarre fairy tale land. Compared to the world above the surface, time seems to be slower here, the blades of seagrass moving slowly in accordance to the currents and tides while fish and invertebrates move about with only the occasional flashes of speed. Even the herds of dugong that graze on the expanses seem to move slowly, chewing their chud calmly and the digging motions on the ocean substrate resulting in sand falling down more slowly than on land. The sea turtles, of course, aren’t any faster; green sea turtles rip blades of sea grass with their beaks, hawkbills bite on marine invertebrates the same way, and flatbacks do both. Sea snakes pass calmly between the corals or above the plains, while a lone tiger shark rips an albatross cadaver without pressing for time. In the distance, a pod of spinner dolphins offers some motion and velocity, but they quickly scatter to deeper waters.

Dugongs, sea snakes, sea turtles, dolphins, albatrosses. These are all marine tetrapods, distant descendents of the first fish to crawl to land that returned to the sea, for a variety of reasons, and by no means the first to do so. With the exception of the sea turtles and the albatross, which are more ancient, all of these have ventured into the sea in the last 56 million years, taking advantage of the Cretaceous mass extinction that barred the oceans of other similar returnees, exploring their newfound condition and diversifying into a variety of species. The key players have changed a lot across time, but most of these groups have persisted and endured, ruling the oceans as their largest and most impressive inhabittants alongside the sharks. A scene like this could easily be set on the Eocene or Miocene, the major differences being different types of whales, a different type of shark, and a different type of sea snake.

Yet another tetrapod also swims about in this scene, also the member of a group that lasted throught mst of the age of the mammals, with as much claim as the dolphins and the sea turtles as a quintessencial marine tetrapod. Yet, only here does it still remain, having disappeared from the rest of the world.

It rests on the ocean surface, sluggish even for the standards of the other animals, moving its and legs tail slowly every once in a while to steer. At first sight, it resembles the saltwater crocodiles that also occur in the Solomon Islands, sauropsids that, while frequently seen at sea, are not true marine animals, their ideal habitat being freshwater environments. Yet this is a true marine tetrapod, and it shows, having several distinct anatomical differences from the saltwater crocodile: a thicker barrel-like body, shorter and more paddle-like legs, a smaller osteoderm armour in every sense of the word – the scutes are smaller and less thick, they are less expensive and they are greatly reduced in number -, and a thicker, more robust tail, with longer caudal scutes, offering a more proper fin-like visage. With its slender, thin jaws, it most closely resembles the gharials from the rivers of India – and, at the time of this scene, Indonesian islands -, but it also differs from them, most notably in the forward facing eyes, as opposed to the googly “stalks” gharials have.

Smaller than either crocodillian at a length of 2.3 meters, this gray-black coloured animal is the last member of a group of marine sauropsids known as gryposuchines. Gryposuchines were but one of several lineages of Cenozoic marine crocodillians, that dominated coastoal waters all over the world. These animals saw the rise of marine mammals like seals and whales, and were not one bit affected, co-existing with their synapsid counterparts all across the age of the mammals. Gryposuchines in particular were a late lineage that prospered in the Miocene, common in the coastoal environments of South America, alongside many bizarre varieties of cetaceans and pinnipedes, while similar species like Gavialosuchus patrolled North Atlantic waters.

Then, just about 3 million years ago or so, nearly all marine crocodillians vanished. The exact reasons for this aren’t clear, but the climatic chaos of the Pliocene seems to be a likely culprit, global oceanic cooling rendering many marine environments, such as the western south american coastlines or the North Atlantic, completely uninhabittable for these sauropsids. The changing sea levels also didn’t help, and alongside several seabird lineages and non-delphinid cetaceans, gryposuchines met their end. Only one species survived through that, and it was the distant ancestors of this individual, which were carried away across the Pacific alongside the Fiji iguanas, somewhere in the late Miocene. Now, the Murua Gharial is left to carry on the legacy of its lineage, giving an insight to how the earlier Cenozoic seas functioned.

The individual is a female. She is a rather old animal, around 45 years of age, scars along her tail and flanks detailing numerous encounters with predators, while smaller marks in her jaws indicate years of multiple conflicts with other females for nesting sites. She inhales, and her rest ends, diving as she does. With her forwardly oriented eyes, she spots a beaked sea snake, and delivers a burst of speed with her tail. Before the serpent can evade, the slender jaws snap at the fraction of a second, the shock stunning the squamate and the teeth piercing through its torso. The Murua Gharial doesn’t need to do much beyond opening the jaws and rotate the prey’s immobilised body towards the throat, swallowing the snake as she would a fish.

After that, she swims calmly in the water collumn, her tail providing the undulation necessary for propulsion, while the body remains largely still and the limbs steer. Next to the dugong herd, she couldn’t look anymore alien, yet sea cows have swam alongside crocodillians for most of their evolutionary history. Dugongs, even the calves, are too large to be threatened by a Murua Gharial, so they ignore her, keeping to their grazing. A young bull gets in her way, a problem she solves by walking on top of him, before swimming off. Small fish trail behind her, picking parasites and loose scales from her flanks, but are cautious, even more than when cleaning a shark.

At the distance the tiger shark is still processing the albatross corpse, but the crocodillian doesn’t take any risks and speeds up, rushing towards the shore. For a moment, in her speed she resembles the spinner dolphins, now in more open waters, and indeed both animals are alike in many respects. Dolphins diversified alongside her kin’s radiation in the Miocene, both mammals and sauropsids having evolved in parallel, in the same coastoal waters. The tiger shark notices the hastening movement and briefly begins to speed, but in little time she has gone through the shallow water threshold that the shark can’t pass.

From there on, it’s several meters of shallow water until the waveline is reached. Nurse sharks and rays patrol for mussels, ignoring her as she walks in the bottom, stirring up sand. Not too long ago, many of her kind passed through these shallows in great numbers every day, walking between the shore and their deeper water feeding grounds. Why, when she was young these same shallows saw a constant traffic of adults either going from feeding grounds to shore or from shore to feeding grounds, or simply resting, courting and mating. Now, only she and the odd other passed through, a pattern that has been going on for at least a decade now.

When she finally reaches the waveline, the gravity support water gives her ends, and her graceful posture in water is replaced by an awkward galumphing, similar to that of a seal. In the white sands, these crocodillians only shared the beaches with turtles and non-aquatic animals passing by, but just 3 million years ago the opposite side of the Pacific saw competition between her ancestors and many species of seal and sea lion for beach grounds. She doesn’t get very far, simply making her way some 2 meters from the water, before stopping.

As she basks in the sand, she sees grisly remains, several feet ahead. These belong to her kind, an adult male, in life larger than her at some 3 meters. Now, what remains of his body is mostly his head, and some viscerae, like the kidneys, as well as his emptied out torso. Most of the internal organs, musculature, the tail and the limbs were hastily removed, their points of attachment messily cut, bones broken and ligaments pushed and stressed like the fibers of a cut rope. Blood soaks the sand everywhere, and forms a trail several meters to her left, ending a meter or so away from the waveline. Black headed gulls fight over what’s left, though they are obviously not the culprits.

The identity of the killer can be seen on a small stone near the corpse: a cutting tool, a knife. The female doesn’t need to know who caused this: one of her scars, bearing still a hook, is testemony of her previous encounters. She cannot stay here, but she is too tired to move, and simply lays. By now, she knows that the killers won’t return for a while, and for the past year or so she has met them with less frequency. A small plover walks nearby, searching for small invertebrates, cautiously avoiding getting too close to the gharial’s jaws.

Several hours pass, and the male’s carcass is clean. The female heads back to water, the afternoon Sun hot and unforgiving. As she crosses the shallows, a familiar figure appears in the distance: a boat. Franticly, the crocodillian gains speed, using the tail to propell herself forward, towards the deeper waters. In her haste, the rays and nurse shark scatter about, panicked as well. The boat’s crew seem to have noticed where she is heading, as the wood-made structure moves towards the deeper water in a semi-parallel direction to hers. But her instinct endures, heading towards the deeper waters regardless. This stubborness is how she’s survived for this long, avoiding to be strapped in the shallows where her enemies have the upper hand, but it is a risky gamble.

Just as the water deepens enough for proper swimming instead of crawling in the sand, a spear hits her tail. It doesn’t stick, but the blade makes a small cut, drawing blood and adding to her collection of wounds. The boat is still far away, not matching her speed, but more lances are thrown, hitting her back, tail and flanks. One of them stays lodged where her tail meets her right leg, and slows her down. As the boat approaches, she dives, and as the wooden shaft hits the bottom the weapon is released from her flesh, creating a deep wound that cuts through her caudal muscles. Nonetheless, she manages to swim away, and with a few bursts of speed she is out of reach for the boat, in open waters.

The boat ceases pursuing her, and once they leave, she surfaces, taking the moment to rest. Once more, she stops lazily as she floats, though more exhausted than before. Blood leaves her body, but it’s now the first time she’s been wounded like this, and it would eventually stop.

The scenario truly repeats itself as earlier that day, as dugongs once again forage in the plains beneath her, as so sea turtles. Time seems cyclical in the Pacific tropics, especially in an isolated environment such as this. The routine lays itself once again, but soon the clock will be left without one of it’s cogs.

A shadow looms in the distance, only this time underwater. The tiger shark has returned, and it senses the Murua Gharial again. Only this time, she heads to deeper waters, and she bleeds, triggering the shark’s hunger. And this time, the target is much larger and more succulent than a dead albatross.

Before she is able to comprehend her predicament, a pair of jaws strikes at her right flank, cutting through muscle, gastralia and bowels. She franticly tries to swim away, to no avail, as the water is clouded as her torso is emptied out. She manages to swim away even as her guts are completely removed, but the shock, diaphragm rupture and sheer bleeding quickly tire her out, and she can’t find the strength to move. With a last, desperate breath, she inhales before the shark begins eating through her thorax, and her bulk sinks.

A few minutes pass, and the deed is done. From now forth, only the occasional crocodile shall find itself in the sea, merely passing through and never staying. Nearly all of her bulk is consumed, by the shark and other marine carnivores, leaving only her skull to sink, as a final insult.

One Comment leave one →
  1. December 17, 2015 12:34 pm

    Beautiful story. I could make many of these. We want more hypothetical stories of last members of theri species going extinct. Preferably with tuataras, synapsids, small defenseless mammals, etc. The animals must have a very small brain and not be able to comprehend fully what is happening, they will be lost, find themselves in conditions they cannot cope, eaten by humans or otherwise get in situations they cannot escape and then die.
    ps. You could make the story even more disturbing by leaving the disembodied head alive for much time in the sea floor. Reptiles have a lower metabolisms, and it is known that diving species like aquatic turtles have a surprising ability to withstand anaerobiosis.

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