LATE CRETACEOUS

HELL CREEK FORMATION.

 

The Hell Creek formation of Montana and the Dakotas represents the only well studied terminal Late Cretaceous fauna. It contains a varied group of theropods, ornithipods, pachycephalosaurs, ankylosaurs and ceratopsids. The flowering plants dominate the flora; conifers are locally common with ferns and their allies primarily in a herbaceous role.  The last of the dinosaurs are found here.  Also the most famous dinosaurs Tyrannosaurus and Triceratops are from here.  It has been the popular vision of dinosaurs and how they lived.  The number of species compared to early periods appears to decline.  This could be a sign of environmental stress conversely it could also be a sign that the regression of the inland seas allowed for a larger more uniform territory favoring less speciation.  No fossil site of the same age have been found so we have no idea if the is representative of dinosaur populations elsewhere.  At the end of the period a massive meteor or comet stuck the Yucatan.  No undisbuted dinosaurs have been found after that event.  It marks the end of the age of the dinosaurs.

mouse over diorama pics for figure information.

From Right to left Kaiydo Tyrannosaurus, Toyway Ankylosaurus, Kaiyodo Triceratops, Schleich Edmontosaurus, Toyway Leaellynasaura, Tamiya Hypsilophodon, Two different Tamiya Triceratops.

Recent discoveries have given us more information about Tyrannosaurus ( Tyrant Lizard), Albertosaurus and Daspletosaurus have become rare but Tyrannosaurus seems to have been relatively common..  They even may have formed family groups with a mated pair and offspring of various ages.

From Right to left Kaiydo Tyrannosaurus, Toyway Ankylosaurus, Kaiyodo Triceratops, Schleich Edmontosaurus, Toyway Leaellynasaura, Tamiya Hypsilophodon, Two different Tamiya Triceratops.

Flowering plants were the most diverse plants of the day, although ferns and conifers may still have been more common in terms of numbers. 

The UKRD Edmontosaurus and Ankylosaurus above are based on dated reconstructions. The popular but invalid 1950's species Trachodon has largely been subsumed by Edmontosaurus. Trachodon was based on very finds of teeth some of which were from Triceratops. The Bullyland Tyrannosaurus one of the first bipedal Tyrannosaurus figures. ?There is a Play Visions Euoplocephalus. The Invicta painted Tyrannosaurus and a Wild Safari Pachycephalosaurus are farther to the right.

The terminal Late Cretaceous fauna seems to have a lower diversity of dinosaur species than the preceding period. The total number of species is lower and the ecosystems seem to be dominated by just one or two of the remaining species. Edmontosaurus and Triceratops are the most common dinosaurs; others are uncommon or rare.  Edmontosaurus is very similar looking and closely related to Anatotitan, Anatosaurus in North America as well as Shantungosaurus in China.  Ankylosaurs are common in the Scollard formation of Alberta that overlaps in time with the Hell Creek formation. Its close relative Ankylosaurus in the fossil record succeeds Euoplocephalus. While earlier pachycephalosaurs were small to medium size animals, Pachycephalosaurus was the giant of the family at 15 feet long. Known mostly from skulls, it has been speculated these washed down from the dry interior of the continent.

Carnegie Safari Tyrannosaurs Battat Pachycephalosaurus Oriental Trading Company Ornithomimus

 

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