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Page 5 UPDATED 05/15/06

North America has large areas of exposed Late Jurassic rock.  The enormous four legged plant eaters called sauropods were the dominate animals of the period.   At least six kinds of sauropods are known to have lived in North America in the Late Jurassic  period.  These are Apatosaurus (Brontosaurus), Camarasaurus, Haplocanthosaurus, Diplodocus, Barosaurus and Brachiosaurus.  There are also several diplodicids known from incomplete skeletons..

Vinyl is recent as a material for dinosaurs.  Quality varies from reproductions by the Kaiyodo , Tsukuda and Horizon  companies to the many unattributed  and inexpensive bin  style figures from China.  Many vinyl figures are mismolded giving a starved or pinched look.  The joined parts are often mismatched and poorly joined with glued running everywhere.     The figure can be pulled apart the body stuffed with filler ( newspaper works well).  Vinyl is soft and lends itself to modification and can often be customized by enthusiasts.   This is accomplished by placing in hot water or using a hair dryer.  This make s the vinyl easy to trim and reshape.   The limbs can be repositioned when heated and wire can be added to hold the position when cooled.  This allows the often surprising good design of the figures to be visible.

Apatosaurus (Deceptive reptile) at 70 - 90 feet long, roamed the western part of North America from Montana to Baja California.  Not a common animal and perhaps more solitary than its more slender relatives.  Better know by its junior synonym  as Brontosaurus.

Track ways have produced some interesting speculation about the behavior of sauropods.  They seem to move in small groups indicating they were social to some extent.  You would expect large animals to have large ranges and migrate regularly.  The different size of the foot prints of some track ways have suggested that young animals traveled with the group perhaps even were protected by being in the center of the group.  Other track ways seem to suggest young animals traveled in groups on their own.  The reassessment of fossils previously identified as adolescent animals as adults of dwarf species may indicated herds of mix animals or herds of the dwarf groups.  They seem generally to like dry arid environments.  The plants were mostly conifers and their allies.  Typically these are plants that grow slowly, whose foliage contains chemicals that make them hard to digest and have a low food value.   The Diplodocus and its relatives had pencil like teeth that wouldn't have allowed the food to be chewed.  They may just have acted as rakes to help get to pants to their giant stomachs were the the food was fermented to break down the chemical defenses.  Large stones found associated with sauropod fossils have been identified as gastroliths.  They would have been swallowed  and then would have helped break down the plant material is the gut and maybe help mix it around.

Front is the green JASMAN diorama Apatosaurus while back in the Laramie Apatosaurus.  Next another Larmie with a yellow Toys R Us  bin figure from China which has the suggestion of the fleshy spines  along the back recently associated with some sauropod finds

Diplodocus was about 88 feet long but lighter, more common and more social than Apatosaurus.  Since sauropods continued growing Seismosaurus and Supersaurus  at 130 to 150 may have been old individual Diplodocus or its close relative Barosaurus. Seismosaurus ; found in Colorado is known from a few bones. It is estimated to have reached 116 feet long.

 

 

Seismosaurusfrom the Kabaya Collectors Club. The back drop is theAllDinos.com Giants of the Jurassic Play set.

Above are a pair of Laramie Diplodocus.  The middle scene contains a Kaiyodo Allosaurus and two bin stegosaur figures.  To the far right are two of the Diplodocus from the large bin figures JASMAN  distributes.

Camarasaurus was the most common sauropod and possibly one of the earliest to appear.  Smaller at about 30 - 60 feet than many others.  Remains of many young have been found.  From track evidence some sauropod young seem to have lived in groups separate from adults.  The young were probably the main prey for the the theropods Allosaurus and Ceratosaurus.  Adults would been dangerous prey.

Waiphoon figures from China are examples of the great designs that can be found in low cost vinyl figures.  The Allosaurus and Camarasaurus are Waiphoon figures.  The Ceratosaurus is from a Dollar Store set while the Stegosaurus in from a popular 4 inch series marketed by Boley and other companies.  Then a Kaiyodo Camarasaurus with a Stegosaurus and Allosaurus from a Waiphoon set.  Last three "adolescent" diplodocids.

Allosaurus (Different Lizard) 30 - 36 feet, perhaps larger if some bones assigned to other dinosaurs are actually Allosaurus.  There fossils assigned to Allosaurus fragilus are probably from two distinct species.

 

 

Allosaurus from TS Toys has a strong resemblance to the BBC's Walking with Dinosaurs Big AL.   Galaxy Wild Dinosaurs Stegosaurus stenops  from Safari.

Something about the Late Jurassic must have made being big a real advantage. Diplodocus (double beam) is often described as the longest dinosaur at around 80 feet.  It though to have been a relatively common dinosaur and social.   Pangaea still hadn't broken up so a combination of  a larger rang, arid environment and plants with low food value may have favored large size.  There may have been a relatively small number of adult animals migrating over very large ranges.  One idea is that the the diplodocids were boom feeders.  They their long necks would have allowed them to feed low over great areas without moving.  It has been suggested that their were parries of ferns covering the Jurassic.   While ferns may well have common in the well watered areas they don't typically do well in arid settings.  Cycads and cycadoids while present were not abundant enough to support larger animals.  The flora was different from today and larger areas that today are populated by grasses may have been barren in the Mesozoic.

 

Brachiosaurus (Arm Lizard) is distinct from the diplodocids by having a robust skull with strong teeth. It also had front legs that were longer than back the reverse of other sauropods.

Stegosaurus ungulatus is one of several less common stegosaurs found in North America in the Jurassic. The plates were smaller and there were 8 spikes.

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