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Spec Dinosauria: Dinoceratopsia

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INTRODUCTION

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Dinoceratopsia skulls: Ramskull, Durocephalus boothi (top left), Dinoceratops,Dinoceratops horridus (top right), Stormrider Tuskhorn, Jugaloceratops robustus (bottom left) and the Everglades Tuskhorn, ​Parajugaloceratops americensis (bottom right).

South America is a continent of many oddities, from the enigmatic mergaraptors to the giant pseudosauropods, the pachamacs, but the dinoceratopsians have proven to be some of the Neotropics' most frustrating and fascinating creatures.

HISTORY

The ancestors of the dinoceratopsians, primitive cenoceratopsians similar to the dawnhorns, crossed from Asia to North America some time during the early Neogene (or possibly as early as the Oligocene), and in the late Miocene and Pliocene, they diversified into a host of huge and bizarre forms. These creatures, however, soon faced the fate of most of their earlier cousins, the ceratopsids, as North America cooled and the open deciduous forests ceratopsians prefer were replaced with inhospitable grasslands. Hadrosaurs and therizinosaurs spread to take advantage of the new Ice Age habitats, but North American ceratopsians were forced to migrate southward. In some places, the dinoceratopsids held on, and it now seems that a single species has survived in southern Florida, with rumors persisting of similar creatures in the swamps of Louisiana.

Dinoceratopsia escaped oblivion, however, as some populations migrated past the dubious havens of Louisiana and Florida. As early as the Pliocene, populations of dinoceratopsians migrated across the Panama Isthmus and established themselves in South America. There were at least two distinct migrations, the early dinoceratopsids (today represented by a single species) and more advanced jugaloceratopsids (including the everglades tuskhorn). The enigmatic 'durocephalids' may represent another migration (possibly earlier than the jugaloceratopsids), or may have evolved in South America.

BIOLOGY

All dinoceratopsians are united in the possession of extraordinarily long jugal processes, which, in most species, are further extended by horn. Although originally for display, some species now use these jugal tusks as digging or rooting tools. No dinoceratopsian has true nasal or brow horns, although some sport a variety of bosses and scaly crests. Most have small scutes set in the skin which in the "durocephalids" have developed into quills.

DINOCERATOPSIDAE

Dinoceratops (Dinoceratops horridus)

Dinceratops

Dinoceratops, Dinoceratops horridus (Central & Southern South America)

Surprisingly, it appears that not every single dinoceratopsid has tusks as in the case of Dinoceratops. The sole extant member of its family, the dinoceratops is the most primitive living dinoceratopsian. At least eleven fossil taxa from this family have been described from North and South America, most small-to-medium-sized browsers.

In lieu of true horns, the dinoceratopsids sport(ed) bizarre arrays of bumpy protuberances on their heads and frills which are used (in the living species at least) in head-butting contents between rivals. Dinoceratops horridus (the species name is most likely a nod to the most famous ceratopsian of all time, Triceratops horridus) is known from central and southern South America. This bizarre animal is common in the bush and thorny steppe of eastern Brazil but also ranges into open woodland and savanna. The dinoceratops is a specialized low-browser that tackles very coarse, spiny vegetation.

JUGALOCERATOPSIDAE (Tuskhorns)

These large and flamboyant ceratopsians might be considered to be the spiritual descendants of the great chasmosaurines of the Cretaceous and Eocene. Upon closer inspection, however, one finds that the jugalceratopsids' great horns sprout not from the brow, but from enlarged jugals, or cheek bones. These horns are used by some species to dig for roots and tubers, but are primarily for sexual display, with the males developing great, curved structures rather like elephant tusks. Jugaloceratopsids are the only American ceratopsians with epoccipital bones, and they often have prominent spikes decorating the edge of the frill. Strangely, they have also developed a straightened tail/sacral region akin to their distant brachioceratopsian cousins. There are five known species of tuskhorn, all medium-to-large browsers, filling niches similar the elephants and black rhinos of HE Africa. Two species, the mountain horn in the extreme south, and possibly the everglades tuskhorn in the extreme north, have explored smaller-sized lifestyles, but all jugaloceratopsids are savanna or forest-margin browsers. The reopening of such habitats in North America at the close of the Ice Age may indicate an opportunity for ceratopsian recolonization of North America, and it remains to be seen if the new browsing therizinosaurs and hadrosaurs can hold their own again these lumbering titans.

At least one jugaloceratopsid species appears to be extending its range into southern Central America and it may only be a matter of time before great horned herds once again thunder across North America.

Mountain Horn (Cryopelta montanus)

Mountain Horn

Mountain tuskhorn, Cryopelta montanus (Western and southern South America)

Mountain horns (Cryopelta montanus) are the southernmost-dwelling tuskhorns, making their homes atop the many plateaus of the southern Andes in what would be Chile and Patagonia. To insulate itself from the intense cold of these regions the mountain horn has evolved thick pads of fat that cover its legs and sides. These fat supplies are not only for warmth, but serve also as nourishment for the mountain horn as it ventures treks across the icy mountains from one plateau to another.

A pig-like rooter, mountain horns, use their jugal tusks to excavate tubers and grass roots from under shallow soil or snow-fall. They are often associated with upclaws, Neotropical therizinosaurs that eat the larger shrubs and herbaceous plants of the mountain slopes.

K'z'k Tuskhorn (Jugaloceratops kizke)

Stormrider

K'z'k tuskhorn, Jugaloceratops kizke (South America)

Second largest of South America's dinosaurs at up to 6 to 7 meters, and fully as massive as the more lanky pachamacs, the k'z'k tuskhorn (Jugaloceratops kizke) is a truly fearsome animal. Though a plant-eater, k'z'ks are ferociously territorial, and their bellicose temperament extremely poor eyesight makes them liable to charge at any moving object in their vicinity. Biologists on foot, in a jeep, and even (in one case) low-flying aircraft have been pursued and trampled by enranged k'z'ks. All told, the k'z'k tuskhorn is responsible for more human injury and death in Spec's South America than all of that continent's predatory species combined.

The k'z'ks' territorial nature, however, is not due to simple blood-lust or bad temper (although many would argue that these factors do play a significant role in k'z'k behavior). K'z'ks are specialist-browsers, feeding upon a specific selection of grasses and shrubs that grow only in in stream-fed groves or forest margins. These plants grow in relative abundance on the pampas, but due to the k'z'ks' large size and weight, the herbivores cannot help but trample their fodder, even as they eat. From the point of view of the pampas plants, therefore, k'z'k tuskhorns are less mere herbivores than a force of nature, with a destructive power comparable to hurricanes or landslides. Many of the pampas plants sport protective poisons or thorns to deter k'z'k attentions (the dominant tree of the pampas, a relative of the locust, sports thorns around its trunk that are half a meter long), the giant herbivores chew through vegetation incredibly quickly. Even a large grove cannot last more than a week under the onslaught of a k'z'k. The k'z'ks' nature therefore forces them to be nomadic and reclusive, as any collection of the giant herbivores would completely destroy their food supply.

More noticeable than their bad tempers or rapacious eating-habits (at least from a distance) are a k'z'k's magnificent 'tusks'. Both sexes sport long, curving jugal horns, the largest of any dinoceratopsian (males often a grow tusks of over half a meter in length). Female k'z'ks use their slightly smaller horns for uprooting small trees and clearing paths through brush, but the males' tusks are more decorative in nature. In the mating season, male k'z'ks will butt their tusks against each other and push, demonstrating to watching females their strength and general health. The tusks are sharp, and may be used by either sex against attackers, but in mating battles between males, each k'z'k is careful to avoid injuring either himself or his opponent. During most of the year, k'z'ks will kill any large animal that gets near them, but a k'z'k in love is a gentle beast.

Stormrider Tuskhorn (Jugaloceratops robustus)

The stormrider tuskhorn (Jugaloceratops robustus) is a slightly smaller cousin of the k'z'k tuskhorn. Like their cousins, the dinoceratops, stormriders are low browsers of the forest margin, but these immense animals (which grow up to 6-7 meters long and weigh up to a metric ton) have been known to uproot entire trees and always wreak destruction upon the habitats they visit, though they are not nearly as destructive as the k'z'k.

DUROCEPHALIDAE (Tuskfrills, till-cheeks, and ramskulls)

INTRODUCTION

Ceratopsians (today represented only by cenoceratopsians) are one of the more cryptic herbivore groups of Spec. Rather like the perrisodactyls of Home-Earth, Spec’s cenoceratopsians belong to an ancient and widespread group that has now been reduced to a few scattered remnant populations. Some cenoceratopsian species are well-known and significant members of their ecosystems, but others have so far eluded proper description. The so-called ramskulls or "durocephalids" of Spec’s Amazon are the most infamous examples of this gap in our knowledge.

INFORMATION BASED ON EXPEDITIONS TO THE AMAZON AND PALEONTOLOGICAL EVIDENCE FROM FLORIDA

Durocephalids represent at least two species of cryptic dinoceratopsians that dwell in the depths of the Amazon jungle: the tuskfrill, the till-cheek, the well-known species, the ramskull (Durocephalus boothi), the extinct species Projugaloceratops problematicus and the recently discovered Everglades Tuskhorn (Parajugaloceratops americensis). Very little is known of these creatures, with only a single decent specimen in a museum collection. The remainder of what we known of these creatures is gleaned from half-chewed skins and eyewitness reports. It doesn't help the fact that even more expeditions back to Spec have revealed the existence of several unknown durocephalids, several as far north as Central America.

Tusk-Frill (Genus name unknown)

Tusk frill

"Tuskfrill" (Amazon)

The tusk-frill therefore cannot be reliably assigned to a classification more exact than "somewhere in Dinoceratopsia" although the name "Durocephalidae" is often used informally. The first durocephalid sighting took place during the preliminary South American forays of Brian Choo. He writes this brief passage concerning the beast in his journal:

"An exciting, newly discovered ceratopsian that lives along waterways in dense tropical forest. It is particularly common on the shores of the Pantanal where it uses its remarkable tusk-like frill extensions to root for aquatic plants. Although currently placed in the Dinoceratopsia, a new family may need to be erected to accommodate this as yet undescribed species. An indicator of what may still be left to discover in the poorly sampled Amazon jungle!" -Brian Choo

Although the picture and description of the “tusk frill” were widely circulated, the species was largely ignored in the literature, listed as a poorly understood member of the South American cenocerotopsian group Dinoceratopsia, and then forgotten. The tusk-frill would probably have faded out of the public consciousness entirely if it were not for the discovery of a very similar creature soon after.

Till-Cheek (Genus name unknown)

The Brett & Booth South America expedition returned with new till-cheek-like material in the form of a single water-damaged skin and parts of a skull collected from the nest of a jagular. The skull fragments consisted of parts of a hooked, parrot-like beak, a curved jugal horn (a characteristic of some dinoceratopsid species), and the low-slung frill split down the middle. The skin was damaged badly be water, rot, and the jagular, but it indicates an animal perhaps two meters long, with short limbs and a large belly. Most intriguing are a number spines, formed of elongated scutes, which were found attached to the skin near the tail and base of the neck. Close examination of the skin revealed holes where more of these spines had once grown, indicating a porcupine-like coat of quills that extended across the till-cheek's back.

Till-cheeck

Reconstruction of "till-cheek", the animal recovered on the Booth Expedition (Amazon)

Booth published a reconstruction based upon the skin and skull fragments, showing the armor of quills and the jugal horns, which earned this species its unofficial nick-name.

Of course, connections were immediately drawn between the till-cheek and the tusk-frill. Both creatures possessed the medial division of the frill, and the tusks Choo interpreted as extensions of the frill could have very well been the pronounced jugal processes of the till-cheek. These jugal extensions are also very similar to those of the jugaloceratopsians, drawing some intriguing connections between the tiny till-cheek and the massive stormrider. However, since neither the till-cheek nor the tusk-frill is based upon a reliable type specimen, both must be considered Dinoceratopsia incertae sedis. The only tusk-frill-like species known from any decent material at all was discovered only recently by noted Old-World specbiologist Matti Aumala. Subsequent to the initial discoveries by Choo and Booth, Aumala fielded another expedition to the Amazon, searching for better specimens. He succeeded in capturing a single male subadult of a species, which he illustrated and briefly described.

Ramskull (Durocephalus boothi)

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Ramskull, Durocephalus boothi (Central South America---Amazon)

The heavily-built ramskull is the best known "till-cheek" dinoceratopsian from the rainforests of Amazon. This tapir-sized animal has strong jaws and robust jugal horns suited for digging, coupled with a massive skull with growths not unlike those of the Cretaceous Pachyrhinosaurus. These horny pads may be used in butting contests between males. The frill is split in the middle and the edges of the frill curve inwards, serving as attachment points for the powerful jaw muscles. Stiff quill-like spines cover much of the back and tail, perhaps serving as protection from predators. The nasal openings are curiously small, atypical of (well known) dinoceratopsians. These animals come equipped with strong jaws and jugal horns suitable for digging, coupled with a thick bony skull that is used for butting contests between males or for defending itself from predators.

Durocephalus boothi is the only formally described "durocephalid", the type specimen having been stuffed and in good condition and from observations of wild specimens. However, the ramskull is obviously different from the description and sketch of the tusk-frill. The tusk-frill is based upon nothing at all, and the till-cheek is not much better, so while the ramskull and till-cheek are probably distinct, it is impossible to say anything definitive about the tusk-frill. Out of all the members of the durocephalid family, coming as no surprise to anyone, the ramskull is the only member of its kind to have its behaviors observed by various members of the South American explorations. Subsequent to the ramskull’s discovery, several other expeditions were mounted into the South American interior, but none of these excursions managed to gain new information. A fossil recently recovered from Florida’s Pliocene deposits may shed some light on the ramskull and its kin, but the fossil is still awaiting detailed examination.

Projugalceratops problematicus

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Projugalceratops problematicus (Pliocene) (Florida)

The 2.5 million year-old Projugalceratops problematicus was originally described by Drhoz, but the Australian specbiologist did little other than sketch the cranium and propose possible dinoceratopsian affinities based upon the enlarged jugal processes. Recent evidence proved that this is actaully the first of the jugaloceratopsians known from the fossil records. At first glance, a Projugaloceratops seems very much like the ramskull, but the overall shape of the skull is suggestive of a much more primitive group. The skull (which is the only part of the skeleton illustrated) bears a striking resemblance to Cretaceous North American genus Leptoceratops gracilis, and seems rather unlike any South American ceratopsian. Further studies are necessary to determine the exact affinities of this fossil, and for that matter the living species it resembles.

As of now only, some speculate this is the jugalceratopsine fossil yet found, possibly the first of the tuskhorn family. However, this issue is still under debate given the only known fossil is a mostly complete skull, several ribs and vertebrae. To further complicate matters, this North American fossil bears a very strong resemblance to the poorly-understood Frill-tusker of the Amazon.  Perhaps the frill-tusker and Projugalceratops form a group ancestral to all other jugalceratopsines, but more specimens must be studied to determine whether the species' similarities are phylogenic or merely convergent.

THE CONFIRMED VALIDITY OF THE EVERGLADES TUSKHORN

A recent expedition to Florida, fielded by cenoceratopsid expert Brian Choo and noted specdinosaurologist Matti Aumala, attempted to find the cryptic ceratopsian and solve once and for all which theories about the tuskhorn were correct - if the animal truly existed at all. Though the expedition failed in obtaining an intact specimen, they found the remains of a dead subadult individual, consisting of a skull with remains of the skin still attached, incomplete ribcage and scapula, pelvis and part of the tail as well as the upper portion of the left femur apparently bitten in half by a predator. Based on the remains and excisting photographic evidence, the length of the dead animal was estimated to have been close to 1,5 meters. It is still unknown how large the tuskhorn may be when fully grown, but based on some reports it may reach the length of three meters.

Everglades Tuskhorn (Parajugaloceratops (Floridajugaloceratops) americensis)

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Everglade Tuskhorn, Parajugaloceratops americensis (Florida Everglades and Southeastern North America) 

The most recent "dinoceratopsian" find, again tantalizing but frustratingly inadequate for real anatomical description, is the 'cryptid ceratopsid' described in passing by Matti Aumala and Brian Choo.

Despite the public cynicism, there soon came new reports of dinoceratopsid-like animals from other parts of Southeastern NA. Some critics dismissed them as figments of imagination, but others began to more firmly believe in the existance of a North American ceratopsian, and several theories of its origin and true nature were formed. The find of a Pliocene ceratopsian Projugaloceratops problematicus, hailed as the ancestor of the "durocephalids" by some, from Florida lead to the hypothesis that the tuskhorn might be the very same animal, still alive in the innermost reaches of the Everglades.

The origins of the Everglades tuskhorn are still unclear. According to the first of the two competing theories the tuskhorn is a relict species that survived the ice ages in the southern parts of Florida, and after the glaciation has spread to larger parts of NA. The other theory assumes that the tuskhorn either survived or perhaps even evolved in Middle or South America, and has migrated to North America fairly recently. The second theory seems to have more evidence to support it, as sightings of tuskhorn-like animals have been made not only in Southeastern NA but as far south as the Yucatán peninsula. The supporters of the Middle American theory also like to refer to the primitive Projugalceratops as evidence that the tuskhorn's niche was already filled prior to the ice ages, and became free only after Projugalceratops had become extinct. It is however unclear how similiar niches these two poorly known ceratopsians occupy.

"We all know that dinoceratopsians are supposed to have gone extinct in the North America. It seems, however, that somebody forgot to tell that to one cryptic ceratopid, said to live in Florida and the surrounding areas of Southeastern North America known as the Everglades Tuskhorn now known as Parajugaloceratops americensis. So far, there is only one photograph to prove its existence, and many are still skeptical, claiming that the photograph in question was forged, or that the animal it portrays is from South or Central America instead. Whatever the case, the animal in the photograph is previously unknown to specbiologists. It is clearly a dinoceratopsian, looking somewhat like a crossbreed of a dinoceratops and stormrider, but unfortunately until we find out where this species lives and catch a specimen for study, it will have to remain yet another question mark in the dinoceratopid family tree."

"As mentioned earlier, some have hailed Parajugaloceratops americensis as a link between Dinoceratopsidae and Jugalceratopsidae, and further place it, along with the ramskull, into the family Durocephalidae. It is even possible that the Everglades Tuskhorn is related to (or the same as?) the skull Projugalceratops. Whatever the case, however, a single photograph cannot be the basis for classification, and the Everglades Tuskhorn is yet another question mark." -Matti Aumala

Aumala and Choo suggest erecting a new genus, Floridajugaloceratops, for the tuskhorn, but that was ultimately rejected for the name for the name of Parajugaloceratops americensis. It is however still uncertain if the tuskhorn is different enough from Jugaloceratops to warrant having its own genus.

CONCLUSIONS

In his recent monograph on Dinoceratopsia, Brian Choo classified these enigmatic ceratopsians based upon examinations of the till-cheek and ramskull specimens:

"Durocephalids" have well-developed jugal horns and a divided parietal which forms a medial split that extends at least halfway down the frill. The frill does not possess epoccipital bones but may sport enlarged scales on the edge. They also have a covering of thorny scutes, which in the tillcheek have evolved into porcupine-like quills. Contrary to some popular reconstructions, the sacral region is probably curved as in dinoceratopsids rather than straight as in jugaloceratopsids. -Brian Choo

This description is adequate and future species found can be labeled "durocephalid" with fair accuracy, but the relationships of and between these creatures remain murky. Are there, in fact, three species of durocephalid, or two, or only one? Do the durocephalids and jugalceratopsids share a common ancestor? Is Projugalceratops (or Parajugaloceratops) that ancestor, or from some other branch of the ceratopsian tree, entirely? Only time, study, and more specimens will tell.

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