One of the groups of dinosaurs that has made itself at home in North America are the therizinosaurs.  In the distant past (some 100 million years ago) these strange maniraptors made a brief foray into North America, but later went extinct on the continent.  There have been two subsequent invasions of this group, one during the Miocene, when the ansestors of the seculasaurs came to North America, and one in the Pleistocene, when the ceronychids (moora and panha) conlonized America's Northern reaches via the Bering Strait.

SECULASAURIDAE
    Seculasaurids evolved from primative Eurasian therizinosaurs soon after the clade had migrated to North America in the Miocene and have become quite successful in the New World.  While fossils indicate that seculasaurines did migrate to Eurasia (along with other herbivores, such as the hadrosaurs), during the Pleistocene, the American species apparently could not compete with the Eurasian forms.  In any case, seculasaurs are endemic to the new world.

    Seculasaurids (commonly called "Liandaolong") are generally quite small (no more than 3 meters long), and have radiated into a number of varieties specializing in specific plants and levels of foliage.  Liandaolong, with their long, flexible necks and long legs, look almost like ornithomimes, but their ancestry is given away by their enlarged bellies and hyperextendable hallux claws (an adaptation found only in Seculasauridae).  Liandaolong are most specious in the northern prairies of North America, and their diversity tapers off quickly south of the 55th parallel (where competition from the viriosaurs becomes fierce).  Even in South America, however, liandaolong can be found on high mountains, where their insulating plumage gives them an advantage over ornithopods.

(Text by Daniel Bensen)

SAMPLE TAXA:

Golden-maned liandaolong

Northwestern liandaolong

Sierra-Navada tirg

 

CERONYCHIDAE
    During the Pliestocene, both ceronychids (hornclaws) and glaciotitanids (robust therizinosaurs) migrated to North America.  As the tundras shrank, however, the robust therizinosaurs declined and eventually went extinct on this continent.  In the glaciotitanids' absence, the ceronychids have become the dominant herbivores of America's northern reaches and closely reseble their relatives in Eurasia.

SAMPLE TAXA:

American Woolly Therizinosaur

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