Dinosaur Hunter

by Steve White

  Between the monsoons, the dry seasons can be harsh and incredibly hot, although many rivers and lakes remain well watered enough to run throughout the year.

  GEOGRAPHY AND ENVIRONMENT

  The high carbon dioxide, humidity and temperatures, as well as regular rainfall, mean that the Chinle is well vegetated; a floodplain fans out northwards from an epeiric body of water running north from the ocean. This floodplain forms a floodplain of numerous large rivers and lakes that fans out for thousands of square miles towards the Mogollon Highlands to the south and the Protorockies to the east.

  The FOB is located in the well-forested southern foothills of the Mogollons while the reserve is away from the Chinle’s interior heartlands and to the south of the range in rich coastal swamps and deltas. Like the interior, these deltas are well watered by numerous rivers, bayous and lakes. Gallery forests of large conifers, Araucarioxylons, overlook the rivers, braided streams, ponds and marshes; these trees can be massive, some measuring 200ft high. These thick forests of tightly packed, towering conifer trunks are dark and dank (especially in the wet season) and support few large animals.

  The Araucarioxylons thin out away from the watercourses and are replaced by woodlands of smaller cycads and ginkgoes surrounded by beds of hardy ferns. During the wet season, larger herbivores will brave these fern prairies to feed on the new growth, followed, naturally, by their predators.

  The rivers are lined with dense stands of huge horsetails that form the understoreys of the conifer forests. These horsetails can measure up to 100ft high and, in places, can be impenetrable. The ground covering is made up of various cycads, lycopods and club mosses, and ferns and mosses that can form coverings over the lower trunks of larger trees not unlike modern creepers and ivy.

  The banks of the rivers can also be lined with thick mussel beds that can make the going underfoot difficult.

  LICENSED TARGETS

  You are licensed to hunt the following species in the Chinle:

  POSTOSUCHUS

  The Chinle’s apex predator, Postosuchus.

  Length: 12–13ft

  Weight: 500–600lbs

  This heavily armoured carnivore is not a dinosaur, although it does have the appearance of how the likes of T-rex were envisaged in the early 20th century. Postosuchus belongs to a group of reptiles called Rauisuchidae, part of a group called the Pseudosuchia or ‘false crocodiles’ that does actually include modern crocodilians.

  Undoubtedly the apex predator of the Chinle, its massive skull sports jaws are lined with long, serrated teeth adding to its dinosaurian appearance. The larger, less numerous teeth in the upper jaw are recurved to hook into prey. The lower jaw contains smaller but more numerous teeth, which act like the prongs of a fork, pinning the flesh of its prey while the large upper teeth slash and tear into it.

  Postosuchus is equipped with large eyes and nostrils that provide excellent eyesight and sense of smell; it also has a Jacobson’s organ (more properly known as the vomeronasal organ or VNO); this allows the predator to ‘taste’ the air for particles of scent trapped in the humid air. In the dense forests and undergrowth of the Chinle, this gives the Postosuchus a great advantage while hunting.

  Postosuchus is a facultative biped (like many herbivorous dinosaurs); it can move in both bipedal and quadrupedal gaits. The heavily built predator usually walks on all fours, although, with the forelimbs half the size of the hind ones, it is slow and cumbersome. However, when required to move somewhat faster, such as attacking prey, it often lifts itself on to its hind legs, using its considerable weight and mass to build up speed and inertia, the massive head counterbalanced by the long tail.

  This is its primary form of attack. Postosuchus is an ambush predator. Its primary habitat is the thick gallery forests (where they are open enough to allow it to travel) and dense riverside understoreys. From concealed positions it will charge its prey, launching forward, propelled by its powerful hind legs to deliver a savage bite. As much of its prey is large, even larger than itself, this bite is not intended to kill. Blood loss and shock are often left to do that in smaller prey animals, but in larger ones Postosuchus uses microscopic allies to finish off the prey. It will trail its victim, sometimes for many days until infection takes its toll. It is the primary function of the VNO to track such infected prey; the VNO may also be used to sniff out the state of the infection.

  Postosuchus’ primary prey includes Placerias and Aetosaurs, even other, smaller Rauisuchids and Poposaurs; but in its role as apex predator, almost no animal is immune to attack except the larger Phytosaurs. Postosuchus is also a keen scavenger, stealing kills from any predator unable to withstand its bullying.

  Female individuals are generally larger than the males but the only real sign of dimorphism between the genders is the heavier armour of the males, probably as a result of sexual selection; the more numerous scutes and plates provide protection for males fighting for females and territory, while looking more impressive to prospective suitors.

  Postosuchus is territorial. Male and female territories often overlap but the only time the animals socialize is during the mating season; otherwise, they are just as likely to fight with and scavenge from one another. Favoured territories include watercourses that remain wet throughout the year.

  Breeding season for Postosuchus is at the start of the wet season, coinciding with the breeding season of many Chinle inhabitants; the start of the rains triggers mating. The pregnant females then begin fasting and make nests in deep forest. They stay with the eggs until they hatch, during which time they become particularly aggressive. A male Postosuchus will happily cannibalize eggs and young, and females will drive them out of their territory at any opportunity.

  On hatching, the female continues to fast and protect the young long enough for them to disburse into the forest; from then on, her parental duties are over.

  REDONDASAURUS

  The huge phytosaur, Redondasaurus, ambushes the metopsaur amphibian, Koskinonodon – itself a pretty mean predator. All this action startles a freshwater xenacanthid shark.

  Length: 25ft

  Weight: 2,200lbs

  Without a doubt, the largest animal in the Chinle, Redondasaurus could easily be mistaken for a modern crocodile at a distance and in appearance, lifestyle and behaviour is not all that different to its modern counterpart. Its general body plan is very similar, even down to the same semi-sprawling gait; it is only in the head where significant changes make themselves apparent; the primary difference is that the nostrils are further back on the elongated jaws and set in a raised dome just ahead of the eyes (rather than in the tip of the snout as in crocodilians).

  This feature is present in all members of the group that Redondasaurus belongs to: the Phytosaurs. This non-dinosaurian order forms the most common large family of vertebrates in the Chinle with numerous species adapted to several predatory ecological roles (ironically Phytosaurs were thought to be herbivorous when they were first discovered in the late 19th century and their name means ‘plant lizard’). Redondasaurus is first and foremost a predator, as reflected in its teeth. Following a heterodont pattern that reflects, in evolutionary terms, its position as perhaps the most advanced member of the group, there is more than one tooth type; those at the tip of the long snout (which forms 80 per cent of the head length) are very long and interlock to form a perfect bear trap to capture prey. Behind the tip, the teeth are still long and conical-shaped; those at the rear half of the jaw are shorter but stouter, and better suited for crushing bone.

  With a metabolism and body shape so like those of modern crocodiles and alligators, it is hardly surprising that the lifestyle and behaviour of Redondasaurus are very similar. It can regularly be seen basking beside Chinle watercourses, sunning itself or cooling off in the shallows, often with its jaws agape. It often gathers in larger numbers although these gatherings can be defined by age and sex, the largest conglomerations being those of young adults, again, like modern crocodilians. Such indolent b
ehaviour and its apparently sluggish nature belie its abilities as an extremely effective ambush predator.

  Its principal hunting strategy is to attack from the water; floating close to unsuspecting animals drinking or feeding by the water’s edge, or charging from a well-chosen ambush site (always beware of deadfalls or dense riverside foliage). However, Redondasaurus adults can kill and eat just about anything living in the Chinle; from the largest Placerias and Aetosaurs to other predators, including smaller Phytosaurs. They hunt in the water, taking Metoposaurs, coelacanths, lungfish and freshwater sharks; but are not afraid to leave the water to scavenge or even attack slow or injured animals. Like modern crocodilians, they can put on a fair turn of speed with their semi-sprawling gait. However, unlike them, Redondasaurus does not leave its prey to decompose before eating; the heterodont tooth pattern enables it to break down carcasses quickly and efficiently.

  The back and flanks of all Phytosaurs sport rows of armoured scutes and long dermal plates but this is especially true of Redondasaurus. However, with adults having no natural enemies to speak of, the armour is more for protection against the bites of its own kind. Many bear battle scars, usually as the result of squabbles over meals, as well as mating and territorial disputes. Some of these wounds can be very serious; the loss of a limb, broken jaws, blinded eyes.

  COELOPHYSIS

  The little dinosaur, Coelophysis, hotly pursues breakfast – a Sphenosuchian crocodile – through a Chinle stream.

  Length: 10ft

  Weight: 50lbs

  The only truly iconic dinosaur of the Chinle, Coelophysis is a small opportunist predator with the basic body plan of most small dinosaur predators: the slim, athletic build with long tail, body and legs, relatively long neck and smaller forearms equipped with grasping hand. The hand actually dates Coelophysis; it still poses a rudimentary fourth finger, a primitive condition lost in most later Theropods who had three or even two fingers (Abelisaurs being the exception, as they too retained the fourth finger as a primitive feature).

  The head of Coelophysis is slender, lightly built and narrow, the jaws carrying a large number of small teeth. It lacks a powerful bite, which narrows its choice of prey; it hunts mainly smaller animals such as insects, running Sphenosuchian crocodiles and the young and eggs of larger species. It will also fish for juvenile Phytosaurs and Metoposaurs, as well as fish and aquatic invertebrates, using its hands to pick over rocks and branches to scrabble for the likes of freshwater crayfish.

  Sexually dimorphic, Coelophysis represents a body pattern that can be seen in many later Theropods. There are two forms; the female ‘robust’ and the male ‘gracile’, although the bland colouration of the females makes them quickly distinguishable from the more brightly coloured males, especially during the mating season. Both sexes have a covering of simple protofeathers not dissimilar to the down of a modern flightless bird. The down is constructed from the shaft that much later in Theropod evolution would support fully evolved feathers.

  Generally, and especially during the dry season, Coelophysis is solitary and spends much of its time in deep forest close to water. However, the arrival of the wet season triggers the breeding season; pairs mate and nest in the gallery forests, both sexes feeding the precocial young who are soon ready to leave the nest. Once they are able to fend for themselves, the adults abandon them and the young scatter.

  The breeding season also sees a more unusual behaviour pattern emerge in Coelophysis. The young adults that are too young to breed gather together in large flocks that are often joined by fully mature adults. This seems to relate to a compulsion to migrate out of the more heavily forested areas and onto the fertile fern prairies. The newly watered fern prairie attracts a large number of animals including many young ones that provide a steady food source for non-breeding Coelophysis. The reason they form such flocks seems to relate to safety in numbers; so many smaller predators may deter or confuse larger ones as the dinosaurs travel out into open country. Once they have arrived on the prairies, the flocks quickly disband and the Coelophysis sweep the ferns for the rich plethora of prey before returning to the safety of the forest after a few days.

  These flocks are vulnerable less to large predators than to natural disaster. Flash floods and forest fires have occasionally been known to wipe out hundreds of young Coelophysis in a single event.

  The lightweight build of Coelophysis means that an elephant load will virtually obliterate your prey. We recommend a small, low-velocity round or flechette.

  OTHER FAUNA

  These sections are far from complete field guides; they are simply to give a broad outline of the kinds of animal you can expect to encounter in the various reserves.

  PHYTOSAURS

  The largest of the formation’s herbivores and one of the last of the dicynodont, Placerias.

  As mentioned above, Phytosaurs are the most common vertebrates in the Chinle. They fall roughly into the three categories:

  Fish-eaters: These species are similar to the modern gharial, with long, flattened, extended jaws containing many small cylindrical teeth ideal for a piscivore. The nostrils are well forward of the eyes, which are positioned to look upward so that the animal rests on the bottom and ambushes its prey from below. These species of Phytosaur, best represented by Pseudopalatus, have noticeable sexual dimorphism; the males have a raised nasal crest running from the eyes down the snout. These species are not considered particularly dangerous, unless provoked.

  Generalists: These types, represented by Smilosuchus, have more robust snouts, with the nostrils in a raised crest (which also exhibits sexual dimorphism); the teeth are heterodont, including not just the cylindrical piscovorian type but also blade-like slicing teeth. They hunt a broader variety of prey, although this varies with age. The young are mainly fish-eaters but as they grow older their teeth adapt to hunting terrestrial prey and large aquatic types such as Metoposaurs. These types are considered dangerous and will attack without provocation.

  Predatory: Represented by Redondasaurus. May be considered very dangerous.

  CHINDESAURUS

  Smaller (8ft long and 30lbs) but considered more dangerous than Coelophysis, Chindesaurus belongs to the Herrerasaurs, a group of dinosaurs better known from South America. This predator is lightly built but for its head, which is blunter and rather more solidly constructed than the slender, narrow skull of Coelophysis. Its teeth are long, serrated blades and adapted for delivering slashing wounds. Its hands retain the primitive four-fingered condition of Coelophysis (although the two are not closely related), but sport more robust claws, used to injure, handle and control prey. Not as nimble as Coelophysis, Chindesaurus is an ambush predator that can take larger prey than its counterpart.

  PLACERIAS

  The most common and the largest herbivore in the Chinle, Placerias is one of the last of the dicynodonts, a group of Therapsids (mammal-like reptiles) common in the Early and Mid-Triassic. This hippo-sized animal can be up to 12ft long and grow to a ton in weight. Its stout, barrel-shaped body is supported by four thickset legs and sports a stubby (and slightly comical) tail. The neck is thick and supports the large head; the skull has a bony crest running down between the eyes; the mouth ends in a powerful beak, on either side of which is a large, downward-pointing tusk. These are generally for digging and rooting through soil, but can also be used in defence. Males sport particularly large pairs that are used in intra-species combat, which usually involves little more than brutal shoving contests. Placerias is a social animal in that it lives in large herds of as many as a hundred. They frequently gather in wallows, often staying close to these during drought conditions; in the wet season, the herds nest colonially for mutual protection of the eggs and young. The young stay with the herd until they are big enough to form bachelor herds of juveniles. The adults migrate out of the more densely forested and wooded areas to feed on the new growth on the fern prairies; they return to the forests at the onset of the dry season.

  AETOSAURS

/>   The members of this strange order of quadrupedal, herbivorous Archosaurs are a relatively common sight in the Chinle. With their armadillo-like plated armour and pig-like snouts, they are forest foragers snuffling through the leaf litter for soft plant matter and even insects.

  The largest and most heavily armoured of the Aetosaurs from this stage is Desmatosuchus. Large adults can be over 15ft long and 5ft tall at the hips. Unlike other contemporaneous Aetosaurs, they sport arrays of spikes culminating in a pair over the shoulder that can grow to 18in long. The spikes do prevent Desmatosuchus from foraging in thicker forest but the added protection means they can inhabit more open areas where large predators such as Postosuchus are more of a threat. They are generally solitary animals.

  The broadest of the Chinle Aetosaurs is Paratypothorax. It lacks the bigger spines of Desmatosuchus but is easily identified by the line of short but hooked and flattened spines that edge its plated armour. Paratypothorax prefers swamps and marches, laying in mud or water, its broad back giving the appearance of a ridged stepping stone!

  Stagonolepis grows to about 10ft in length and travels in small herds; it lacks the broad back armour of the two other types but this allows it to live in more thickly forested areas, where it travels in small herds of 5–20 animals. It also has better developed teeth than other Aetosaurs which, combined with the tough beak-like tip of its snout, allows it to crop tougher vegetation.