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SPEC'S PLIOCENE EPOCH (c.5,000,000 - 1,700,000 b.p.)
The geography of the Pliocene Specworld looked quite similar to the present-day map. As North and South Ameirca finally met, the isthmus of Panama rose from the sea, separating the tropical Atlantic from the Pacific and ending South America's long isolation. The Mediterranean was fully formed, but was barred from the Indian Ocean by the Sinai peninsula,
which joined Africa and Eurasia. A permanent polar icecap had started to form at the Arctic, shifting the warm Gulf Stream as cool currents flowed down the Labradore coast. Temperatures on land and in the sea continued to cool.
Many kinds of marine invertebrates vanished, unable to adapt to the changing temperatures, but
were quickly replaced by more modern forms. The productive cool waters at the poles soon played host to a crowd of newly evolved animals taking advantage of their expanded habitat. Swimming birds radiated further and grew increasingly large. Enormous filter-feeding cephalopods harvested the clouds of krill. In warmer waters, new species of lizard-whales
terrorised the oceans.
On land, the vegetation was shifting in response to these cooler, drier conditions. While trees still dominated the
uplands, in the mid-continental belts, they were giving way to open grasslands. Low-lying areas once covered in green forests and woodlands were now transformed into endless seas of golden grass.
The rise of the grasslands lead to the loss of many ancient browsing herbivores. The armoured ankylosaurs, already
uncommon since the Oligocene, declined to a handful of species in America and Australia. The last of the eurolophs
were gone, while only a single genus of high-browsing sauropod remained in Africa.
As some groups faded with the vanishing forests others rose to meet the evolutionary challenge. Throughout Africa and Asia,
vast of herds of hoofed ungulapedes were on the march, these weird duckbills soon radiated into an incredible variety of forms. Cooler northern latitudes witnessed herbivorous niches becoming increasingly dominated by two of the most unlikely of candidates - the therizinosaurian theropods and the paraselenodont mammals. In North America, the neohadrosaur duckbills
continued their monopoly of the large herbivore guilds. Also making their presence felt were the frill-necked ceratopsians.
These dinosaurs had been absent from North America since the end of the Oligocene and their recent arrival from Asia
heralded the return of giant horned herds to the continent.
Biogeographically, the most important event of the Pliocene was the linking of the two Americas.
Much of the unique South American megafauna vanished in the face of North American immigrants.
The northern dinosaurs had dealt with climatic change and faunal interchange with Asia throughout the
Cenozoic, thus were full of competitive vigour. Their southern counterparts, on the other hand, have
lived on a more stable, isolated world for millions of years and in most cases fare poorly against the invaders.
Soon, duckbills and ceratopsians had displaced many unique South American ornithopod families, while
tyrannosaurs and hesperonychids had replaced the abelisaurs and endemic notoraptors. Of the large
southern herbivores, only the giant pseudosauropods held their own. However, the migrations
were not one-way, as neotropical viriosaurs and marsupials flourished in the north.
The only major landmasses still completely isolated were Antarctica and Australia. The former was now virtually
lifeless, but the latter boasted a staggering display of weird endemics. The thick forests that once covered most
of the island continent were now restricted to the margins, giving way to open woodlands and savannah. One
lineage of herbivores, the euclasaurs, had undergone an explosive evolutionary radiation akin to that of the Old
World ungulapedes. Hunting these odd herbivores were their predatory rhynchoraptor cousins.
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