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| - The thyreophorans, the armored dinosaurs, evolved in the Early Jurassic and soon grew to be the dominant low browsers of the middle Mesozoic evolving into (among other things) the famous stegosaurs in the Middle Jurassic. Stegosaurs went extinct soon after the end of the Jurassic, in the Early Creataceous (but with a possible Late Cretaceous record), but the more heavily armored thyreophorans, the ankylosaurs, survived, and by the end of the Cretaceous, existed in two major groups, the immense, tank-like, club-tailed ankylosaurids, and the somewhat smaller, less well armored nodosaurs. Both groups diversified throughout the Early and middle Cretaceous, with the ankylosaurs ranging across Eurasia and North America, while the nodosaurs spread across the globe. Nodosaur fossils have been foun
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| abstract
| - The thyreophorans, the armored dinosaurs, evolved in the Early Jurassic and soon grew to be the dominant low browsers of the middle Mesozoic evolving into (among other things) the famous stegosaurs in the Middle Jurassic. Stegosaurs went extinct soon after the end of the Jurassic, in the Early Creataceous (but with a possible Late Cretaceous record), but the more heavily armored thyreophorans, the ankylosaurs, survived, and by the end of the Cretaceous, existed in two major groups, the immense, tank-like, club-tailed ankylosaurids, and the somewhat smaller, less well armored nodosaurs. Both groups diversified throughout the Early and middle Cretaceous, with the ankylosaurs ranging across Eurasia and North America, while the nodosaurs spread across the globe. Nodosaur fossils have been found on almost every continent on Earth, a fact that no doubt saved them from the disaster wrought upon their kin. Fossils indicate that ankylosaurs in general were faring well all the way up to the Eocene (50 million years ago). However, the very latest Cretaceous deposits in North America fail to turn up any evidence of other herbivore group, while revealing abundant hadrosaurs, ceratopsians, and other ornithischians. Apparently, some disaster other than the Chicxulub bolide was responsible for the abrupt extinction of most if not all of the ankylosaurs and nodosaurs in the Northern Hemisphere, except for the nodopotamids. Though recent expeditions indicated that the vast majority of ankylosaurs seemed to die out during the final days of the Eocene epoch in North America, however with fossils of the nodopotamids dating back to the Oligocene and Miocene epoch, this issue is still under a lot of debate even to this very day. In Asia and South America, they seemed to cling to life, though barely. Over millions of years, all of the Asian ankylosaurs were wiped out in the Miocene epoch by the arrival on new herbivores, the nearly the same fate befell their South American cousins the Pliocene epoch with the invasion of various species from North America when both it and South America were linked up about 3.3 million years ago. The only difference is that less than a handful of ankylosaurs thrive in the America's, however, they have seen much more success in the Australasia region, most notably in Australia which seems to be their main bastion while the majority of their relatives marched into extinction. As far as Spec's preliminary paleontology has implied, whatever killed the ankylosaurs acted upon both our timelines, and the massive club-tailed beasts are just as extinct here as in our home timeline. However, the nodosaurs, with their global distribution, weathered the storm a little better. While nodosaurs in Asia and Europe went extinct with their ankylosaur cousins 70 million years ago, they maintained a toe-hold in the Americas. Early South America (and presumably Africa and Antarctica) had an abundance of armored plant-eaters, but while several nodosaur species have been recovered from South American Eocene strata, their numbers dwindle until, some time during Pliocene, they cease altogether. Paleontologists theorize that the spread of grasslands, combined with the South American asteroid impact, and the invasion of neohadrosaurs from the North combined to kill off most of the North American South American nodosaurs, except for the aquatic ones. Today, their vast majority niche has been partially filled by other South American natives, the panzertoitals, giant meiolaniid tortoises with armor plates and spiked tails very much like the nodosaurs' extinct cousins, the ankylosaurids, and the vanguards, armored ornithopods descended from Thescelosaurus. However, in Australia and Caribbean Islands (possibly even main land South America), they still thrive. In the world of Spec, only three groups of ankylosaurs thrive to this very day:
* Ausankylosauridae
* Antilleankylosauridae
* Nodopotamidae
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