Isisaurus (Indian Statistical Institute (ISI) Lizard) is a genus of titanosaurian sauropod dinosaur that lived in the Lameta Formation, India, as well as the Pab Formation, Balochistan, west Pakistan, 70 - 66 million years ago, during the Maastrichtian stage of the Late Cretaceous Period.
Isisaurus is a medium-sized sauropod, 18 meters (60 feet) long, and weighing 15 metric tons (17 short tons),[1] with a humerus length of 1.5 meters (5 feet).[2] It is known from well-preserved postcranial materials, better remains compared to other titanosaurs at the time of its description. It is said to have a robust, compact skull, made to feed from several types of tree leaves, evidence supported by coprolites (fossilized dung) believed to belong to Isisaurus containing at least four types of parasitic fungi known to infect tree leaves.[3]
As is the case for Rajasaurus, an abelisaur that lived alongside this titanosaur, Prehistoric Planet depicts Isisaurus with red skin covered in black splotches, a color scheme that, in tandem with its rugged appearance, helps it blend in with the rocky volcanic environment it is found in. Its mouth and horizontal stripes on the underside of its black neck are colored grayish-white, and it also has a row of spines running from the back of its head to the tail, much like Austroposeidon. These features and color scheme give Isisaurus an overall iguana-esque appearance, fitting given how the practice of the Isisauruses climbing up to the summits of volcanoes to bury their eggs in the warm soil is very much like what land iguanas of the Galapagos Islands do today.[4]
The juveniles, aside from having larger eyes, smaller back spines, and overall different proportions from the adults as expected, also have a protrusion poking from the center of their upper lip. This projection, known as an "egg tooth", is a temporary tool that birds, reptiles, and monotremes grow as hatchlings to help them break out of their eggs, with this tooth eventually falling off or getting reabsorbed by the bill or mouth as they grow older.
An Isisaurus hatchling sneaks past a Rajasaurus
Isisaurus was featured twice in Badlands. The episode's first segment is about the dangerous journey of the females through the fields of The Deccan to lay their eggs in the warm soil of a caldera, and the fifth, final segment of the episode shows the eggs hatching months later, with the newborn sauropods rushing back through The Deccan to rejoin their mothers' herds in the forests, encountering dangers from boiling mud pits to opportunistic Rajasauruses along the way. The Uncovered segment "Were Dinosaurs Good Parents?" discusses the several strategies dinosaurs had to protect or raise their eggs and young, with direct evidence of dinosaur eggs in The Deccan being brought up to show that dinosaurs have been relying on the geothermal heat of volcanic regions to incubate their eggs much like some animals do today. Isisaurus, along with the other sauropods that appeared in the first two seasons of Prehistoric Planet (except for the Nemegt Forest Titanosaur), is also featured on the Uncovered segment "How Did Dinosaurs Get So Big?"
“ This is the largest expansive lava to flood the Earth for 100 million years. The Deccan in Central India, a hellish place, and certainly not where you'd expect to find dinosaurs. And yet, giants risk their lives traveling here. Isisaurs, and all are females. Lava has been flowing in The Deccan for so long, that in places, it is a mile thick. ”
Isisaurus lived 70 - 66 million years ago in the Lameta Formation in the Gujarat State of India as well as the Pab Formation in Balochistan, west Pakistan. The Lameta Formation is associated with the Deccan Traps, one of the largest volcanic features on Earth.
A trench in the Deccan Traps, where small creatures can hide in to escape from predators
“ In badlands, conditions can change with astonishing speed. Rising summer temperatures fuel electric storms hundreds of miles wide. Here in the Deccan, these seasonal storms cause a shift in the wind direction. And around the caldera where the Isisaur females laid their eggs months ago, the poisonous gases have blown away, providing a critical window of opportunity. ”
The Lameta Formation is interpreted as a semi-arid landscape, though later, more recent studies suggest that it is more of a tropical humid region with rivers, lakes,[5][6] and, as shown on Prehistoric Planet, forests past the jagged terrain of the central Indian badlands. The intense volcanic activity of the Deccan Traps by that time, combined with the tropical climate of the area, subjected Late Cretaceous central India to rainfall of around 1,760 - 1,860 millimeters (69.3 - 73.3 inches) per year, higher than the annual precipitation of modern-day India during a monsoon, around 1,200 millimeters (47.2 inches).[7] These conditions would have maintained a tropical or subtropical biome, an idea supported by four leaf-infecting parasitic fungi found within coprolites attributed to Isisaurus.[3]
Paleofauna[]
Rajasaurus, one of the predators of the Lameta Formation, pursues a juvenile Isisaurus
The Lameta Formation is known as the nesting grounds of titanosaurs like Isisaurus, Jainosaurus, and the dubious Titanosaurus, with evidence showing that the animals used the geothermally-heated volcanic sand of the region to incubate their eggs.[8][PhP 1] These sauropods serve as prey for abelisaurs like Rajasaurus, Indosaurus, Indosuchus, the potentially-dubious Lametasaurus, and Rahiolisaurus gujaratensis. Other animals in the region include noasaurids like Laevisuchus and the dubious Compsosuchus, possible ornithischians (including one mistaken for a late-surviving stegosaur), snakes like Madtsoia and its relative Sanajeh, and the side-necked turtle Jainemys.
A caldera in the Deccan Traps, its toxic gas emissions blown by the monsoon winds
“ They can pick a safe route through cooled, hardened lava. But there are other dangers here. In addition to the steam, a deadly mixture of carbon dioxide and hydrogen sulfide spews from volcanic vents. In the cool, pre-dawn air, these heavy gases sink to create a barely-visible suffocating blanket. Just a few lungfuls can kill. But Isisaurs have one crucial advantage. Their long necks can keep their heads above this blanket of poisonous fumes. But ahead is a place where this will be hard to do... ”
Isisaurus and its contemporaries were among the last non-avian dinosaurs on Earth prior to the Cretaceous-Paleogene Extinction Event, a catastrophe that wiped out three-quarters of life on Earth. However, at least one study theorizes that all Indian dinosaurs may have actually been killed off by a massive eruption in the Deccan Traps 350,000 years before the arrival of the asteroid that wiped out the non-avian dinosaurs.[9]
Nesting Preferences and Parental Habits[]
“ Every spring, females leave the safety of their forest home to make a perilous journey into these badlands. ”
The Isisaurus females are shown to be dedicated to making a journey through the treacherous region of The Deccan every spring, braving the dangers and the struggles up steep slopes to higher ground just to lay eggs in the nesting site made ideal by geothermal heating that would keep their eggs warm. The newly-born hatchlings also make this same journey, though given how there is almost nothing for them to eat (except their mothers' dung and the small amount of plants that grow from them) in the desolate volcanic wasteland, where the traps and predators can easily kill hundreds of them in an instant, they do not have much of a choice.
“ There are many, many layers of lava. Then, in between the lava flows, we find dinosaur eggs. Dinosaurs were coming to this location even when it was highly active volcanically, using it as a nesting site for literally centuries. ”
― Dr. Darren Naish, Lead Scientific Consultant
Based on evidence of nesting sites found in different parts of the world,[10] titanosaurs in general seem to be good parents, laying their eggs in warm soil that provides desirable incubation. Lands kept warm by geothermal heating seem to be preferred, and such volcanic areas can also provide secondary benefits, like forming a hostile environment that wards off predators.
“ Each mother digs a seven-foot trench in the warm sand, to hold over 20 melon-sized eggs. The eggs are safe in the caldera for now, but this is just the beginning of their story. In a few months, hundreds of tiny babies will hatch to face this desolate world. If any are to survive, they'll need a perfectly-timed change in conditions. ”
Even so, Isisaurus is depicted as being an r-strategist. Species that follow the r-selection strategy spawn many offspring, and thus do not provide extensive parental care, since most of the juveniles are not expected to reach adulthood, with many dying while many more survive to bring forth the next generation. Once a female has laid her eggs, her young are no longer her concern. Once these babies hatch, they are left to survive the dangers of the world independently, with the only other help given to them coming in the form of unintentional aid, rations such as food, healthy bacteria, and guiding pheromones in the excrement left by their mothers.
Feeding Preferences and Coprophagy[]
“ There's nothing to eat, except their mothers' dung. Surprisingly, it's very nutritious and important to the hatchlings in other ways too. It introduces healthy bacteria into their guts, and it also contains pheromones that, like smells, will enable them to find their mothers' herd. It will lead them to the safety of the forest. ”
Similar to some modern-day animals, Isisauruses (at least, the juveniles) are shown to be coprophagous, dung-eating. Many creatures, from rodents, rabbits, and pigs, to gorillas, hippos, and elephants, would consume their excrement for various reasons, be it to break down seeds or other undigested food matter for a second time and gain all the possible nutrition from them, to gain the vitamins produced by gut bacteria, or to help their own digestive systems. When such animals are born, their stomach is devoid of the gut bacteria necessary to obtain any nutrition from plants, so it is best for them to get such bacteria from the feces of adults as early as possible.
