by Steve White
Far more common, and a regular sight for any hunter is Saurornitholestes, a lowland diurnal predator 4ft long; it preys mainly on small animals, including mammals, birds, juveniles and hatchlings, but is also a regular scavenger.
Troodonts have a similar diet but are largely nocturnal. With their big eyes and binocular vision, they are very adept at hunting mammals, but in the wet season, they bolster their diet with hatchling Hadrosaurs and Ceratopsians. They hatch their own chicks close to nesting colonies and use the cover of darkness to sneak in and steal eggs and babies. There are two species, Troodon and Saurornithoides, both around 8ft long; however, the former favours lowland, forested habitats while the latter is mainly found in the high plains.
CAENAGNATHIDS
These bizarre yet beautiful small dinosaurs are amongst the most colourful of the Park’s inhabitants. A little over 4ft at the hip, they are long-legged, their hind claws straight, and about 5–7ft long. Their arms appear more wing-like, supporting long feathers, and fold snuggling against the body, while their tails are short, more like a pygostyle, and support a cluster of long feathers. However, their most striking feature, physiologically, is their head. They sport curved toothless beaks above which is a cassowary-like crest. Males are not only larger but also sport larger crests; they are much more brightly coloured, the females, not required to engage in gaudy courtship displays, being far duller but also suitably camouflaged in their forest habitat. The males will also engage in fairly heated combat during the breeding season, and are quite capable of inflicting serious wounds on one another with powerful kicks from their taloned feet. However, when faced with predators, Caenagnathids favour speed where possible as a means of defence.
Primarily herbivores, these dinosaurs use their strange jaws to pluck fruit and nuts, but in the dry season, when these food sources are not as freely available, they will also happily become omnivores, taking insects, shellfish, small vertebrates and even eggs and hatchlings of birds and dinosaurs. There are two species of Caenagnathids in the Park: Chirostenotes, the larger of the two at about 7ft long, and Caenagnathus, which is only about 5ft long. The former is more widely distributed, found up in the riverine forests of the high plains as well as the lowlands. The latter is restricted mainly to the deep forests and marshes of the deltas.
HADROSAURS
Hadrosaurs, the famous duckbills, are the most numerous animals in Dinosaur Park. There are a number of species, divided between the high plains and Magmatic Arc foothills, and the lowlands. The former types are migratory, while the lowland types have more localized populations. They are also fewer in number, the upland species forming herds that can be staggering in numbers, tens of thousands, sometimes even more.
Hadrosaurs have a fairly generalized form; their long forearms appear ‘mittened’, with all the fingers except the thumb covered in a glove of skin, and they are not much shorter than the hind limbs. As such, they are habitually quadrupedal, although prefer to run on their hind legs. Their tails are long and quite deep; their necks are short and curved, and thickset like a horse or bison. This is a convergent feature of herbivores that are low-browsers or grazers.
Hadrosaurs also share the same style of dentition, with hundreds of teeth compressed into powerful grinding batteries at the back of the jaws; these can grind up the toughest plant matter. Duckbills have no front teeth; instead they have the duck-shaped beak that gives them their common name; the edge of the beak is rough keratin and used to pluck and pull up vegetation.
The head is the one area where Hadrosaurs differ. They can be split into two types: crested and un-crested. The former include the upland Hypacrosaurus intermedius and lowland Lambeosaurus; the un-crested by Maiasaura in the uplands and Prosaurolophus and Gryposaurus incurvimanus from the lowland forests.
Hypacrosaurus’ crest is semi-circular in shape, while Lambeosaurus’ is similar but shaped more like a hatchet blade, with a spike-like process protruding from its rear. This serves as an attachment for a ribbon-like crest that runs down its back and tail, a feature also seen in Hypacrosaurus. The crests in both animals are hollow and filled with curved tubes that feed into the nostrils. These tubes serve not just to increase the surface area of the nasal cavity, giving these duckbills a very acute sense of smell, but also act as resonating tubes. As a result, the calls of these animals are very loud; the noise generated by several thousand Hypacrosaurs is quite deafening and can have a disorientating effect on predators, serving as a passive defence. However, this species is lacking in sexual dimorphism beyond a slight variation in size, the female being larger; this generic body type is a feature seen in many animals that travel in large numbers, including dinosaurs. However, Lambeosaurus is somewhat different, the males being larger and with far more pronounced crests (the males are also much more brightly coloured, unlike in Hypacrosaurus where the colours in both sexes are more or less uniform). In the dense forest, strident calls help attract mates and once the female is in sight, the bright colours seal the deal. And while both can be alluring to females, they also serve as deterrents to rival males.
These same strategies are seen in the non-crested Hadrosaurs. The monomorphic Maiasaura live in massive herds on the high plains; these are the largest aggregations of dinosaurs in the Park, gathering in herds tens of thousands strong. Following the breeding season, the young and adults alike fatten up on the fern prairies and upland meadows before migrating to the northern regions in time for the growing season. They then head south, the herds dissipating during the dry season before once more convening just prior to the arrival of the rains in time for courting to begin once more.
Prosaurolophus and Gryposaurus inhabit the low forests, marshes, swamps and coastal regions; they live in small herds that are mainly localized to the lowlands, although some populations will travel to the high plains during the wet season to graze the lush new growth. Both species are dimorphic in size and colour, while the males sport large and brightly coloured bladders on their arched nasal crest akin to those seen in elephant seals. These are used to generate loud roars in the same way Lambeosaurus uses its crest, and for similar reasons.
The result of all these devices is that the mating season in Dinosaur Park is an amazingly colourful and noisy affair!
As with the Ceratopsians, the large number of species present is only possible because of a division of ecological niches. In the high plains and foothills, Maiasaura is essentially a grazer, using its broad beak to crop ferns and ground-covering plants; Hypacrosaurus is a low-browser, feeding on cycads, tree ferns and the understorey vegetation of the upland riverine forests.
In the lowlands, Gryposaurus fulfils the role of low-grazer, while Prosaurolophus, one of the largest of the Hadrosaurs with males reaching as much 30ft in length, is an opportunist that is quite capable of felling small trees as well as browsing low shrubs and ground-covering plants. Lambeosaurus, meanwhile, is a capable mid-range browser but, when rising onto its hind legs, it can also browse as high as any dinosaur in the Park.
While showing diversity in feeding stratagems, when it comes to breeding, Hadrosaurs follow more or less the same pattern, the real difference coming down to the matter of numbers. All species nest colonially, but upland types have nesting areas that are vast, as would be expected from the more open terrain. Lowland species move from dense forest to woodland and meadows, or even coastal beaches, to nest; however, their colonies are somewhat smaller – in the tens. The upland colonies, however, number in the hundreds, the thousands or even the tens of thousands. They can cover dozens of square miles, filled with nests approximately one Hadrosaur body length apart – a strategy adopted by all species. The nests are bowl-shaped and lined with vegetation. Around 20 eggs are laid at the start of the wet season and the young are attended by both parents. The hatchlings themselves stay in the nest for some time; they are initially sluggish, directing all their energy into growing as quickly as possible. To this end, they are fed by the parents, one of them daily joining herds which
head out from the colony to graze and/or browse the surrounding vegetation; the other parent stays behind to protect the young from predators and the weather. These duties are usually rotated on a daily basis.
The need to feed the hatchlings’ high-tempo growth s mean that the adults strip the vegetation surrounding the colony very quickly; they then find themselves locked in a race between keeping up with the young’s growing demands for food with the need to travel further and further away from the nest, where they risk attack from the ring of predators that tends to surround the colony; they also have to contend with growing exhaustion, which in turn makes them weaker and more vulnerable to predation. Accordingly, as the nesting season progresses, losses amongst the adults rise, the result of which is that infant mortality rises as single parents struggle to provide enough food for the young while also being forced to leave them unguarded. Many hatchlings fall to the huge number of opportunist predators who gather in very large numbers around the colonies. Those nests at the edge of the site are especially vulnerable; as such, there is often very serious fighting and theft amongst the adult Hadrosaurs at the start of the laying season; a duckbill will destroy the unguarded eggs of a better-positioned neighbour, who will then abandon the nest, leaving it free for the taking. Those left on the outside must, by day, contend with raptors, pterosaurs, Protoceratopsids and varanid lizards, some of which would dwarf the modern Komodo dragon. By night Troodonts and mammals stalk in to steal eggs, hatchlings and young. Disease is also a potential menace, especially those of the giant upland sites. And, of course, there is the ever present threat of Tyrannosaurs, who have their own nestlings to feed.
However, late in the season, starvation becomes the true grim reaper; as many parents succumb to the various forces arrayed against them, the fast-growing young go hungry and starve quickly; a single parent will abandon its brood if it instinctively knows it cannot provide for the young, preferring to risk waiting to try next season than fight a losing cause. Others, too sick or too exhausted, stay and die with their young.
A nest colony late in the season can be an amazing and melancholic sight – but is the perfect place to stalk Tyrannosaurs…
ANKYLOSAURS
Both families of Ankylosaurs are represented in Dinosaur Park: the Ankylosaurid Euoplocephalus and the Nodosaurid Edmontonia (although the species is unclear) and Panoplosaurus. These are amongst the most spectacular of the Park’s residents.
Euoplocephalus is a wonderfully strange looking beast. At around 18ft long, it weighs over 2 tons, much of that weight taken up with its incredible array of armour. Its broad head features triangular spikes at the back corners of the skull and on the cheeks; larger spikes run down the neck and are largest across the shoulders. Lines of scutes run down its wide-bodied abdomen which is covered in layered plates of armour made from pebble-like scales. The scutes enlarge into spikes once more at the base of the tail.
The base of the tail itself is fairly inflexible but the rest is quite elastic; this is to help it wield the huge club it sports at the tip. This impressive weapon is made up of over several bosses of bone, one particularly large one on either side of the tip and several smaller ones in between. While the armour is largely defensive, the club is very much offensive, the musculature of the tail enabling the Ankylosaurid to whip or lash the club with a flick of the base. Tyrannosaur shins beware…
Impressive as the armour is, Euoplocephalus also uses bold colours that serve as a warning to its potential predators (mainly the Park’s Tyrannosaurs, particularly Daspletosaurus). Clearly, prevention is better than cure, Euoplocephalus adopting the strategy of many apparently dangerous animals, be they bombardier beetles or sea snakes, that they are not to be trifled with. It is also a relatively mild-mannered dinosaur unless riled but then it can afford to be. It is not built for lightning battles; its short legs are quite capable of a slow gallop, but this is rarely put to use. Its body meanwhile has a broad girth to accommodate its sizeable gut, which acts as a fermentation vat for breaking down plant matter. Its teeth are small and, in combination with its broad toothless beak, are used simply to pull vegetation into the mouth. Diet is restricted to soft plants, which in turn limits the dinosaur’s habitat; it is generally found in forests, marshes and swamps, where it grazes on water plants and ground-covering growth. As such, Euoplocephalus is comfortable in water, its broad gut making for an excellent flotation device. It will even swim out to cypress domes and mangrove islands to graze in coastal regions.
The nostrils of Euoplocephalus are unusual, the nostrils themselves broad while the nasal passage is convoluted inside the animal’s large skull. Its eyes are small, relatively speaking, and its sight poor, so these nasal passages give the Ankylosaurid an enhanced sense of smell. However, they also double as resonators that help produce deep low-frequency calls that Euoplocephalus uses to communicate. These sounds travel far in the enclosed forest environments it frequents and even through water. A mainly solitary animal, the only times these calls are put to good use is during the mating season when males establish territories and invite females into them. They will also attract rival males and if push quite literally comes to shove, intra-species battles involve shouldering and hitting the opponent with the tail club, especially around the head. This may explain why the upper eyelids of Euoplocephalus are armoured!
After a perfunctory courtship and delicate mating, pairs go their separate ways. Females nest alone in dense undergrowth and the young, hatched bearing light armour, are abandoned soon after birth. The young are omnivorous and will often stay together in small herds of young from the same clutch. After an initial growth spurt that sees their armour develop quickly, they then go their separate ways.
Nodosaurids are just as impressive and equally well‑adorned with armour, spikes and colours as their Ankylosaurid cousins, but lack a tail club. They more than make up for this in the huge cuirass of pebbled armour that covers its wide back, edged in large scutes, and the array of massive forward-pointing shoulder spikes they sport. That said, they are in general more lightly armoured and have longer limbs, and both types have more narrow snouts; the jaws end in a keratin beak but the teeth are small like those of Ankylosaurids. However, Nodosaurids are more fussy low-browsers, not the broad-shovelling soft-plant grazer that Euoplocephalus is. Nodosaurs tend to favour shrubs, ferns, fruit and seeds; to accommodate their diet, they are more active, Edmontonia being the most widely distributed and most common of all the Park’s Ankylosaurs. It tends to spend most of the dry season in the lowlands, browsing in around more permanent watercourses, swamps and marshes, but in the wet season, they migrate out in the open woodlands and high plains, to graze the fern prairies and riverine forests. Edmontonia is also the most social of the Ankylosaurs, sometimes travelling in loose aggregations of a few animals in more open environments; this is presumably for mutual protection.
Panoplosaurus is the rarer of the two Nodosaurids, restricted largely to the lowland open woods and the deep forests (not so much the swamps and marshes) where it is a solitary low-browser.
The rains bring the Nodosaur mating season, which follows a similar pattern to that of Euoplocephalus. However, intra-species fights are a little different, requiring that the males lock their shoulder spines and engage in shoving matches. A different strategy is employed when warding off predators. Nodosaurs crouch low and turn to keep the shoulder spikes pointed at the aggressor. The only way a Tyrannosaur can really kill an Ankylosaur is to flip it on its back but their broad abdomens, low centres of gravity and sheer weight, combined with tail clubs and spikes, make this a difficult task and it tends to be only a desperately hungry or curious juvenile who would risk attacking these impressive animals.
LEPTOCERATOPSIDS
There are several small-horned dinosaurs in the reserve and these should be avoided where possible. Fulfilling the ecological niche of pigs such as forest hogs, peccaries or warthogs (depending on the environment), they are aggressive and resilient, certainly not to be
trifled with. It’s also wise never to leave food around if you are in a known Leptoceratopsid habitat as this is just asking for trouble. They are considered herbivorous, using their parrot beaks, deep, well-muscled jaws and shearing-blade teeth to crop even the toughest plants; they will also use the beaks to slice off tree bark and wrestle down saplings.
However, plant matter is not all they will eat; they are habitual omnivores. They will eat the eggs and hatchlings of other dinosaurs, and will scavenge, their shearing teeth batteries quite capable of breaking down bone.
One of the most common of these Ceratopsids is Prenoceratops. About 4ft long and about 40lbs in weight, it lives in small troops in the forested lowlands and open woodland. In the wet season it largely restricts their diet to fruit, nuts and shoots except during the nesting season of larger dinosaurs, when it will regularly raid colonies to steal eggs and newborns, but also scavenge dead and dying young. In the dry season, it supplements its diet with carrion on a more regular basis and will even drive smaller predators from their kills.
Unlike their larger relatives, Prenoceratops nest in single pairs, usually in the deeper forests. Both parents attend the nest until the young are old enough to leave it when they are abandoned. The juveniles stay together, usually forming new troops.
There are other larger types that inhabit the open woods and high plains; these are solitary animals that are much rarer and seem taxonomically close to Montanoceratops. Around 8ft in length, they avoid the open plains and meadows during the dry season, spending most of their time in open woodlands and riverine forests; however, when the rains arrive and the new growth provides better cover, they will move out into more exposed environs. They are predominantly low-browsers, but are also aggressive scavengers and have been known to actively prey on small and juvenile dinosaurs, including young Tyrannosaurs.