(fig. 1) Dinoceratospian skulls (top left to bottom right): Durocephalus boothi, Dinoceratops horridus, Jugaloceratops robustus and Parajugaloceratops americensis
South America is a continent of many oddities, from the enigmatic mergaraptors to the giant un-sauropods, the pachamacs, but the dinoceratopsians have proven to be some of the Neotropics' most frustrating---and fascinating---creatures.The ancestors of the dinoceratopsians, primitive cenoceratopsians similar to the dawnhorns, crossed from Asia to North America some time during the early Neogene (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 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 (see 'Everglades tuskhorn', below). All other North American dinoceratopsians, however, are long extinct.
Dinoceratopsia escaped oblivion, however, as some populations migrated past the dubious havens of Lousiana 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.
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 (Dinoceratopses)
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.
This bizarre animal is common in the bush and thorny steppe of eastern Brazil but also ranges into open woodland and savannah. The dinoceratops is a specialized low-browser that tackles very coarse, spiny vegetation.
(fig. 2) Dinoceratops, Dinoceratops horridus (Central and southern South America)
JUGALOCERATOPSIDAE (Tuskhorns)
These large and flamboyant ceratopsians might be considered to be the spiritual descendents of the great chasmosaurines of the Cretaceous and Paleogene. 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 RL's Africa. Two species, the mountain tuskhorn in the extreme south, and 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.
Mountain horns 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.
(fig. 3) Mountain tuskhorn, Cryopelta montanus (Western and southern South America)
Second largest of the South American dinosaurs, and fully as massive as the more lanky pachamacs, the k'z'k tuskhorn 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.
(fig. 4) K'z'k tuskhorn, Jugaloceratops kizke (South America)
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.
Ramskulls ("DUROCEPHALIDAE") [Dinoceratopsia incertae sedis]
Daniel Bensen, Brian Choo, and David Namen