Neodryosaurs are small ornithopods in Asia, Australia, Pacific Islands and Madagascar, relatively common with more than 60 species cataloged. A collection of basal herbivorous iguanodontians, Neodryosauria includes small running bipeds, robust ceratopsian-like quadrupeds and gracile arboreal forms. At present there is some argument regarding the monophyly of this group as it currently classified. However, we shall present the clade as a single entity here, in accordance with the majority of current opinions.


While many neodryosaurs share a strong outward resemblance to the viriosaurs, they are clearly not close relatives of these small antarctornithopods. Interestingly, anatomical and biochemical evidence alludes to a kinship with the another group of American ornithopods, the enormous pachamacs. Some would even go as far as to include the Pseudosauropoda within Neodryosauria but the two groups are kept separate here.

Neodryosaurs share a number of striking similarities to the Jurassic-Cretaceous family Dryosauridae, particularly with regards to their dentition and the articulation between the maxilla and premaxilla, a feature that allows the skull to rotate slightly relative to the muzzle while chewing. Except for Malagasy forms, a large palpebral bone over the orbit gives neodryosaurs a stern, "eagle-eyed" look.

The neodryosaurs' close relationship with the ancient dryosaurids is not a clean-cut issue, however. These modern ornithopods lack the dryosaurs' "open-topped nose", with the maxilla completely separating the narial openings. Digit 5 has been lost, resulting in a four-fingered manus, a feature shared with pseudosauropods. Most neodryosaurs possess a fairly large quadratojual, a plesiomorphic character that suggests that they are more basal to the Dryosauridae.


Neodryosaur fossil remains go back at least as far as the Oligocene of Australia and the Eocene of South America (where they are now extinct). Throughout the Paleogene, neodryosaurs on both continents produced a variety of large and spectacular forms, none of which survive today. In general, the clade seems to have fared poorly when faced with the reduction of forest habitats that occurred during the Miocene. Possible neodryosaur fragments have also turned up in Africa, but these herbivores seem to have been very rare in this region, disappearing sometime before the start of the Miocene.

This spread of fossil suggests the neodryosaurs as a clade existed during the Late Cretaceous and enjoyed a wide Gondwanan distribution. Dryosaur-like remains in Patagonia, New Zealand and islands near Antarctica would seem to support this theory. A well preserved Patagonian ornithopod from the Santonian, Gasparinisaura cincosaltensis, is widely regarded as being close to the ancestry of this group.

Today, their are four families of Neodryosauria:

  • Neodryosauridae
  • Dendrosauridae
  • Psittacosuidae
  • Ansersauridae


The 28 species of this anatomically conservative family live in Borneo, Java, Sumatra, Australia, New Guinea and New Caledonia. Externally, these small bipedal browsers would not have looked out of place in the Jurassic. Prior to the rise of the euclasaurs in the Late Miocene, various forms of neodryosaurids and their kin were the dominant ornithopods in Australia. Today, the neodryosaurids are all small species, generally restricted to forest and woodland habitats.

The living neodryosaurids have picked up the rather unfortunate common name of "Hypsie". During the initial surveys of the Specworld, small bipedal ornithopods were described as "hypsilophodonts" or "Hypsilophodon-like forms" owing to their similarity to that Mesozoic family of basal ornithopods. Eventually, this name was shortened to "Hypsie", a moniker that has remained attached to the neodryosaurids even though they are in no way closely related of the extinct Hypsilophodontidae. Australians have a habit of committing these naming blunders.

Harlequin Hypsie (Montanodromeus kosiuskoensis)


The Harlequin Hypsie is a common sight in the Blue Mountains, being one of the most southern living types of hypsies. It's favored environments are the hanging marshlands, where it feeds on a variety of tubers, mollusks and fungi; it is also the most grass coping of all hypsies, breaking the tall reeds and picking the edible inner leaf-rolls, though it still prefers to feed on leaves, such as those of aquatic plants. In winter months it hibernates, gathering in large coves and borrows to share warmth.

Rimusa (Neolimusaurus camelus)

Few hypsies have adapted to more open environments, and one of them is the Rimusa. With a long neck and small arms and tiny hands, these orange and white animal is mostly a browser like it's cousins, being poorly able to deal with grass, which is left for the hypsies' main competitors, tingamarroids. Bushes and small trees are common in the outback, however, and it is on these that the Rimusa primarily feeds, having a prefference for acacias, picking the leaves with it's beaked snout. It plays a large role in seed dispersal in the outback, feeding on any fruit availiable. It gathers in large flocks, being one of the few hypsies to be quite visible and easy to find.

Quat (Sauroaepyornis novocaledonica)

How hypsies got into New Caledonia is unknown, though they're quite recent arrivals. Out of the 28 species of neodryosaurs, 6 species occur in the various forests of the islands, and they might represent two or even three colonisation events, occuring across the Pliocene and Pleistocene. One of them is currently represent by the Quat, the oddest of these hypsies. Currently the sole survivor of New Caledonia's oldest hypsie invasion, the Quat is a heavy hypsie, with a fat, rotund body and robust legs, with the lower leg longer than the metatarsals, being poorly suited for running. Among New Caledonia's largest land animals, and defenitely the tallest with it's long neck, it lives all over the island's ecosystems, browsing on either the p-Araucaria dominated highlands or the rainforest vegetation of the coastal areas. The female produces a clutch of three eggs every two years, and sexual maturity is only reached seven years after birth.

DENDROSAURIDAE (Dendrosaurs, brumtumblers, prefects, and puusa mölies)

This group is of primarily Melanesian distribution, of which only 6 species are found in northern Australia (twice as many species may be found on Borneo). Dendrosaurs have unique, crenulated pads on their feet (superficially similar to a remora's suction-disc) allowing them to tightly grasp onto vertical surfaces. Most have a large thumb-spike rather similar to that of their ancient giant cousin, Iguanodon. This spur can be used for defense or for puncturing and scraping large fruits.

Goldstriped Dendrosaur (Dendrosauroides longmani)

While technically the type genus, Dendrosaurus is both basal - it might have diverged from it's relatives as early as the Palaeocene - and morphologically derived within the clade, a group of fairly large, long-legged tree-climbers with long snouts and torsos. Dendrosaurus are most common on Australia, where they compose most of the living dendrosaur diversity, although some species live on Papua, and their diet consists primarily of leaves and fruit, occupying a similar ecological niche to the mainland indonesian languors and carpos. 

The Goldstriped Dendrosaur (Dendrosauroides longmani) is an attractive inhabitant of lowland rainforests in the Cape York Peninsula. Large dendrosaurs, goldstripes eat a variety of fruits, nuts, tender leaves, and flowers. More cathemeral than most dendrosaurs, it often forages during the day, being one of the most easily sighted of all australian dendrosaurs. Foraging in day time, of course, has it's risks, as it is frequently attacked by avisaurs. Few other arboreal predators dare attack a goldstripe, thanks to the lizard's powerful jaws, delivering bone crushing bites.

Goldstripes are serially monogamous. Both genders displaying bright golden stripes on an otherwise dark brown skin, they form pairs during the breeding season that dismantle after it is over, is is unusual as neither parent takes part in raising the young. After the eggs are laid, usually on a deep tree crevice, they're on their own. Juveniles do accompany random adults, however, feeding on their droppings to acquire the necessary intestinal flora. After an year of this, they give up a mostly insectivorous and nectarivorous diet for more dedicated herbivory.

Caped Brumtumbler (Trichosaurus australis)

Brumtumblers (Trichosaurus sp.) are the only ornithischian dinosaurs known to subsist on a diet of nectar. Brumtumblers scramble along the branches of myrtle trees (generally Eucalyptus sp.), nibbling on the flowers and running their specialized, bristle-tipped tongues over the stamens, collecting pollen. Unlike the birds and bats, which transport pollen, brumtumblers add the protein-rich snack to their diet of sugary nectar, making the creatures less of a symbiote to the trees than a pest.

The caped brumtumbler (Trichosaurus australis) is a common tree-climber of the northeastern forests of Australia. With a length never exceeding half a meter, this brumtumbler is much smaller than the average dendrosaur, but this creature is not an eater of leaves and fruit; in its lifestyle, extreme small size is a necessity.

Spotted Brumtumbler (Trichosaurus oncis)

The spotted brumtumbler (Trichosaurus oncis) is a rare and secretive rainforest denizen of southern Papua. Spotted brumtumblers are similar to their Australian cousins in appearance, but are rather larger, and have been known to eat fruit as well as nectar. With a length never exceeding half a metre, brumtumblers are much smaller than the average dendrosaur, and with good reason: these ornithopods are mostly nectarivorous. Brumtumblers scramble along the branches of myrtacean trees (generally p-Eucalyptus), nibbling on the flowers and running their specialized, bristle-tipped tongues over the stamens, collecting pollen. Unlike the birds and bats, which transport pollen, brumtumblers add the protein-rich snack to their diet of sugary nectar, making the creatures less of a symbiote to the trees than a pest. 

Greater Prefect (Commensasaurus adamsi)

The third genus of Dendrosauridae, Commensasaurus is strange, even by the standards of this strange family. Stoutly-built, short-limbed climbers with flexible hip joints, commensasaurs probably evolved fairly recently in Australia and spread north during the Ice-Age, when their small size and high rate of reproduction allowed the commensasaurs to raft from the Australian Realm and establish themselves in Asia.

Home to a dazzling array of organisms from both Africa and northern Eurasia, the lush jungles of Southeast Asia are home to one creature that is descended from neither. The only Australian land animal to live in Asia, the greater prefect (Commensasaurus adamsi) is an oddity in many ways.

The largest of the three prefect species, the greater prefect lives in commensals of around half a dozen females and infants and a single adult male. Like Dendrosauroides, prefects eat mostly leaves, but they lack their cousins' graceful limbs and climbing abilities. Indeed, a prefect's arms and legs, though very powerful, are rather stumpy, and their broad feet and hands, though excellent in clinging to vertical surfaces, are not nimble enough to allow these neodryosaurs to compete with tree-climbing mammals in the search for succulent leaves. A perfect needs none of these adaptations, however, as this animal relies on others for locomotion.


Prefects are nomadic, assemblies nesting in tall trees during the night, and then scrambling onto low branches early in the morning to await their transportation. Soon, a small herd of balundaur, enormous cenoceratopsians and the largest herbivores in the Southeast Asian jungle, will pass under the tree and the prefects will leap onto their backs. From their station aboard the mighty ceratopsian, the prefects are given a free ride to the lushest growth in the forest, where they may disembark and climb into the trees to feed, or reach out their long necks and snag leaves directly from the back of the balundaur. In this way, prefects may travel vast distances in days, relying upon the balundaur's eternal drive for browsing to reach food faster than any other tree climbers.

As beneficial as the balundaur-prefect relationship is for the small climbers, their giant hosts receive only the dubious benefit of a predator-warning system in exchange for carrying around a significant extra weight. Seven 10-kilogram prefects combine to make a bulk that can slow the tread of even balundaur, but the colossal ceratopsians are powerless to stop the prefects as they scramble around their hosts' backs, out of the reach of their horned beaks. In any case, the inconvenience to any single balundaur is not so great, as prefects rarely all rest on the same host at a time, a commensal being spread across all the balundaurs in the herd (three to five individuals). Only during territorial displays to other commensals will prefects gather onto a single host, and then only for a brief time. In the end, the prefects seem to have little impact upon the lives of their giant hosts, and indeed, most balundaurs simply ignore their hitchhikers.

Papuan Puusa Möly (Pussa pussa)

Probably the closest living relative of the commensasaurs among the dendrosaurids is the enigmatic puusa möly. Like it's two northern cousins, the Papuan puusa möly (Pussa pussa) is stocky, with short limbs and a flexible hip joint. However, this herbivore's face is short and deep, like that of a brumtumbler, and its hands, unlike any other dendrosaurid, possess only three functional digits, the thumb claw having been reduced to a stub.


The only member of its genus, the puusa möly is endemic to the island of Papua, where it is the most common dendrosaur species. Males are slightly smaller than females and can be recognized by their black hands and bold facial markings. Young are raised in hollow trees by their mothers, with little help from their fathers.

Puusa mölies subsist mostly on a diet of leaves, and are not particularly selective about which leaves they eat. A puusa möly's crop is enlarged and filled with gravel and symbiotic bacteria, which help break down even the most unpalatable vegetable products. Unfortunately, this digestive action results in the production of quantities of methane gas, which the little dendrosaurids void by belching. Puusa mölies have some control over this reaction, and often use their belches to communicate their presence to others of their kind, generally in very early morning.


This bizarre family of Neodryosaurs contain only a single genus and two species that reside in Australia and New Caledonia.

Piggy-Beak (Psittacosus longi)

The Piggy-beak is a cryptic and rather comical-looking denizen of the rainforest floors of northeastern Australia. It feeds on a variety of fallen seeds and fruits, for which it roots around in the leaf-litter, cracking them open with its powerful beak. Surplus seeds are buried in small caches which germinate if abandoned, thus the animal is an important component in the reproduction of many species of rainforest trees.

Psittacosus was initially described as a ceratopsian. A subsequent anatomical study conclusively proved that the animal was not a marginocephalian but an aberrant ornithopod. Recent biochemical studies suggest that it is a highly derived neodryosaurian.


(fig. 8) A protective mother piggy-beak guards her offspring from a marauding anklebiter.

Rath (Psittacosus caledonica)

Slightly smaller than the piggy-beak, the rath is a common sight in the forests of New Caledonia.

ANSERSAURIDAE (Honkers and Madagascan hypies)

For such a large tropical landmass, the island of Madagascar has a remarkably impoverished dinosaurian fauna, with only about a dozen or so non-avian species. The only Malagasy ornithischians are the 6 species of basal iguanodontians of the endemic family Anserisauridae. These are small, bipedal herbivores that are as yet poorly known and tentatively placed within the Neodryosauria.

On the surface, the anserisaurids appear to be conservative and primitive ornithopods, but the family possesses a number of unique features. The orbits are surprisingly small with no trace of a palpebral bone which gives them a comical "beady-eyed" look rather than the "eagle-eyes" of other neodryosaurs. Expansion of the nasal cavity and the top of the snout creates a "roman-nosed" profile. Unlike some duckbills, which have a similar bump on the snout, the roof of the crest is formed entirely by the large premaxillary bones.

Crested Honker (Anserisaurus cristatus)


Precisely when the anserisaurids arrived in their current homeland is a mystery. It is tempting to assume that they are holdovers from the Cretaceous, when Madagascar first became an island after breaking from India, however there is the perplexing problem in that no Late Cretaceous ornithopod fossils are known from Madagascar (or India for that matter). Another possible scenario is that the ancestors of the anserisaurids colonized the island via Africa (where they subsequently became extinct) early in the Cenozoic Era.

At 3.7 meters in length, the crested honker (Anserisaurus cristatus) is the largest Malagasy ornithopod, as well as the most commonly sighted. They live in small, loose herds in the open woodlands and savannah of the western plains, keeping in touch with one another with loud, goose-like honking calls. Crested honkers are browsers, plucking leaves and fruit from thorny foliage with their narrow bills.

Adult males are easily distinguished by their head-crests, throat-wattles and more prominent stripes. During the breeding season, they stake out and defend small territories from which they strut and call to passing females.

Rummy-Nosed Hypsie (Nanorbis fasciata)


The rummy-nosed hypsie (Nanorbis fasciata) is a cryptic denizen of lowland rainforest of Madagascar and is rarely seen, but often heard. Very little is known about this meter-long herbivore, which has been observed burying small caches of fruits and nuts with kicks of its feet. This behavior, along with its unusually robust beak, suggests that the rummy-nose might be the Malagasy equivalent of the Australian piggy-beak.

Orang Bnarni

Click here to find out about this enigmatic species of neodryosaur.

-Brian Choo, Daniel Bensen, and Matti Aumala

               ,=Neodryosauridae=Montanodromeus kosiukoensis (Harlequin hypsie)
             | |                ,=Dendrosauroides longmani (Goldstriped dendrosaur)
             | `=Dendrosauridae=|
             |                  |                ,=T. australis (Caped brumtumbler) 
             |                  | ,=Trichosaurus=|
             |                  | |              `=T. oncis (Spotted brumtumbler)
             |                  `=|                  
             |                    | ,=Commensasaurus adamsi (Greater prefect)
             |                    `=|
             |                      `=Pussa pussa (Puusa möly)
           | |                            ,=P. longi (Piggy-beak)
           | `=Psittacosuidae=Psittacosus=|
           |                              `=P. caledonica (Rath)


           |               ,=Anserisaurus cristatus (Crested honker)
                           `=Nanorbis fasciata (Rummy-nosed hypsie)