“ Some marine animals that spend all their lives fishing out at sea must occasionally visit the coast for a very particular purpose. In the waters off the drowned continent of Zealandia, a long journey is coming to an end. These are Tuarangisaurs, a type of huge marine reptile nearly 30 feet long. ”
Tuarangisaurus (Ancient Lizard) is a genus of elasmosaurid plesiosaur that lived in the Tahora Formation, part of what is now Napier, New Zealand, approximately 72 - 68 million years ago, during the Maastrichtian stage of the Late Cretaceous Period.
Tuarangisaurus is known from several remains found in varied stages of growth, namely, the skull, mandible, and nine of the front-most neck vertebrae of adults, as well as some post-cranial remains from juveniles, which could already be around three meters (10 feet) long once born.[3] Fully-grown Tuarangisaurus can reach around 8 - 9 meters (26 - 30 feet) in length and one metric ton (1.1 short tons) in body mass,[1][2][3] and can be distinguished from other elasmosaurids by its ectopterygoid (front part of the upper jaw bone), which has a long, backward-pointing projection, with a large boss of bone underneath.
Senses[]
Elasmosaurids possess large eyes that are directed relatively upward, as well as a strong sense of smell. It is mostly believed that hearing is not important for elasmosaurids, hence, they appeared to have completely lost their stapes (also known as stirrups, inner ear bones that help conduct sound towards an organism's cochlea), instead relying on organs sensitive to electrical signals (like the Ampullae of Lorenzini present in certain types of fish) or changes in pressure (like the integumentary sensory organs of crocodiles), as indicated by possible evidence of electroreceptors and mechanoreceptors in other types of plesiosaurs like polycotylids and pliosaurs.[5][6] Surprisingly, however, a study in 2017 confirmed that Tuarangisaurus had stapes, indicating that elasmosaurs retained this inner ear bone after all,[7] though it remains unclear how well its auditory sense is, which can help determine the degree of importance of hearing in the elasmosaur's life.
“ This is the reason for the female's apparent distress; she's pregnant. And now, after a one-and-a-half year pregnancy, a baby. Over ten feet long, nearly half the length of its mother, one of the biggest babies of all time. It needs to get to the surface to take its very first breath. ”
On Prehistoric Planet, Tuarangisaurus is depicted with mundane, striated pale skin meant to blend in with their ocean environment. Several appear in the third segment of Coasts, embarking on a gastrolith-collection trip to a coastal waterfall, while the sixth segment of Coasts showcases their fierce, protective side, with a young individual (and eventually, its entire pod) defending a pregnant female from the assault of the mosasaur Kaikaifilu, allowing the female to give birth safely. Pods of Tuarangisaurus also appear in the fourth segment of Oceans, where they are hunted by a Mosasaurus whenever they venture outside their atoll sanctuaries in the heart of the Pacific Ocean. Snippets of Tuarangisaurus from these episodes are used in the Uncovered segment "What Else Lived Alongside The Dinosaurs?"
The portions of the Tahora Formation that remained above sea level during the Late Cretaceous Period
Named by Dr. Joan Wiffen and William Mosley in 1986 after the Māori term for "ancient", Tuarangisaurus is one of the known creatures that inhabited the Tahora Formation in Napier, New Zealand. Around 83 - 79 million years ago, the lost continent of Zealandia broke off from the rest of Gondwanaland, gradually sinking as it drifted further south. During the time of Tuarangisaurus, more parts of this sunken world would have remained above sea level, serving as a sanctuary for some indeterminate dinosaurs and pterosaurs, while the surrounding seas were filled with mosasaurs like Moanasaurus, plesiosaurs like Tuarangisaurus, ammonites, cephalopods, crustaceans, fish, gastropods, and several other forms of life. In the modern day, only 6% of Zealandia's highest regions (among them, New Zealand and New Caledonia) are left unclaimed by the sea, though there remains enough rich fossil sites to reveal the life that used to thrive within and around New Zealand, like one particular portion of the Tahora Formation, the aptly-named Maungataniwha Sandstone Member, which means "mountain of monsters" in the Māori language.
“ This bay has something that few others can provide. Pebbles that are particular smooth, hard, and rounded. They've been worn by the action of river water, but they're hard to find. Here, however, in the pool at the bottom of a waterfall, there are plenty of them. And the Tuarangisaurs can take their pick. ”
As is believed to be the case for most plesiosaurs (like the South American Elasmosaur shown in the sixth segment of Freshwater), Tuarangisaurus may have at least partially dwelled in freshwater environments. By the coastal areas of Zealandia, where a waterfall plummets into the sea, several Tuarangisaurus gather to collect ideal gastroliths, stones smoothened by rivers.
A pod of Tuarangisaurus in the shallow waters of an atoll
“ ... the very heart of the Pacific Ocean. These enormous atolls and the lagoons at their center provide the only shelter for thousands of miles. In this rare place, Tuarangisaurus, a kind of elasmosaur, finds safety. But outside these shallows is a different story. Each day, the elasmosaurs must venture into deeper water. Canyons in the atoll walls lead from the atolls to fresh feeding grounds. This deep water attracts not just the hungry elasmosaurs, but the predators that hunt them. The biggest in the ocean. Fifty foot-long Mosasaurus. ”
Atolls, volcanic islands that collapsed and left behind a ring-shaped coral barrier reef, are quite prominent formations known in tropical areas (for only tropical conditions can grow and sustain the organisms that make up an atoll). The remains of ancient atolls help indicate the conditions of a region, and the presence of such formations in the Pacific and other such areas date all the way back to the Mesozoic,[8][9] showing that, even then, most of the world's oceans and seas provided a warm, tropical paradise that can sustain the various, warm-blooded marine reptiles that ruled the oceans during the time of the dinosaurs. The fourth segment of Oceans depicts a pod of Tuarangisaurus relying on atolls for protection. In the relatively shallow, enclosed lagoons of these formations, the elasmosaurs are able to stay out of the reach of massive, deep-sea predators, mostly mosasaurs like Taniwhasaurus, Moanasaurus, Kaikaifilu, and Mosasaurus itself. However, to hunt for prey, they must venture outside their safe zones, thus ensuring that they are not completely isolated and are still part of the natural food web to serve the role of both predator and prey.
Hunting Tactics and Feeding Preferences[]
“ Back in the shallow waters of Zealandia, large groups of Tuarangisaurs have come together. They propel themselves with all four fins, and travel almost effortlessly to find the fish shoals that gather here in summer. ”
Like most plesiosaurs, Tuarangisaurus was primarily piscivorous, using its needle-like teeth to grip fish as well as other types of suitable prey like cephalopods. Though plesiosaur necks are rigid and thus incapable of flexibly whipping around to snap up prey from any direction, it is believed that plesiosaurs evolved their long necks so that their heads could ambush and grab fish right before their prey can be alerted by the sight and pressure exerted by their massive bodies.
“ They then do something rather remarkable. They swallow them. They need the stones to act both as ballast and as gizzard stones, "gastroliths" which will remain in their stomachs to grind up their unchewed food. For a youngster, learning to swallow pebbles for the first time isn't easy. It takes a little practice. ”
As indicated by the presence of 30 gastroliths within a juvenile specimen,[4]Tuarangisaurus relied on the use of stones swallowed and stored in their gizzard organs, both to act as ballast and to grind the food in their stomachs.
Parental Habits[]
“ This female is accompanied by her calf, about six months old. At most, she'll have only one youngster every two years or so. It's a huge investment, and one that makes the bond between mother and young very important. ”
Based on fossil evidence, plesiosaurs are known to be viviparous, giving live birth to a single large calf around a third of the mother's size.[10] It is therefore believed that plesiosaurs relied on the K-selection strategy much like whales, elephants, and humans, usually giving birth to as little as one offspring at a time (in the case of Tuarangisaurus, pregnancy can last for one year and a half),[3] a large, slow-growing baby that they provide with great parental care, increasing the chances of the juvenile reaching adulthood. This is in sharp contrast to most reptiles (including most dinosaurs and pterosaurs, as depicted on Prehistoric Planet), which usually rely on the r-selection strategy, spawning many quick-growing offspring which they provide with little to no parental care (with the idea being that, even though many will inevitably die due to various factors from predation to environmental conditions, many more will survive to adulthood and continue the cycle).
“ For the calf, trying to distract the mosasaur is a dangerous game. But it's buying time. The mother and calf are not entirely alone. These individuals may be related, and it's in all their interests to drive Kaikaifilu away. ”
The great parental care provided by plesiosaurs is mostly seen in the third and sixth segments of Coasts, which feature Tuarangisaurus giving birth to large calves and continuing to rear them even when they're two years of age. This defensive streak, in turn, can be seen even in the younger, less-mature individuals, as demonstrated by a two year-old calf risking its life to distract a Kaikaifilu going after its pregnant mother, buying enough time for the entire pod of Tuarangisaurus to assault and finally drive off the mosasaur.
Social Behavior[]
Beyond the K-selection strategy they rely on to raise their young, not much is known about the social lifestyle of Tuarangisaurus, so most of such behaviors depicted on Prehistoric Planet are filled in by speculation within reason. There is yet to be confirmation if plesiosaurs lived in pods, and, assuming they were intelligent and complex enough to have done so, whether these groups were only limited to families, or consisted of several members that were not necessarily related. Prehistoric Planet appears to have gone with the former idea, giving its members even more reason to defend one another. Even then, these pods do not appear to be permanent, and, for most of the time, mothers only stick with their calves and no one else.
“ Tuarangisaurs come here from across the South Pacific. Males also gather here to display to females. But for now, courtship is not the female's first priority. ”
The third segment of the Coasts also depicts male Tuarangisaurus poking their rigid necks vertically above the water, raising their heads as high as they can to prove themselves better than rival males and to impress females, taking advantage of the fact that many of them have come to collect gastroliths from an ideal source implied to have been visited for several generations. This neck-raising mating display is taken from "All Yesterdays", a book written by Dr. Darren Naish, the lead consultant of Prehistoric Planet. As is expected of most caring parents amongst animals, females would prioritize their offspring, as shown when one mother first introduced her calf to the concept of swallowing gastroliths, before leaving the youngster for a while to mate with a suitable male, giving the calf a moment to learn the necessary skills while also giving herself an opportunity to bear young yet again.
Gallery[]
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