Trivia / When Dinosaurs Roamed America

• Actor Allusion: During the segment on the Apatosaurus the narrator chimes in "This is Dino of The Flintstones." This is a reference to the narrator John Goodman since he played Fred Flintstone in the movie adaptation.
• Creator Provincialism:
  • It's an American documentary about American dinosaurs, self-explanatory. To be fair, America does have an amazingly rich fossil record that covers most of the Mesozoic from the dawn of the age of the dinosaurs up to the K-Pg extinction.
  • A likely reason why Dilophosaurus and "Syntarsus", who are known from the Arizonan Kayenta Formation, are shown rubbing shoulders with Anchisaurus (who is known from Connecticut and Massachusetts) rather than the unambiguously sympatric Sarahsaurus. Until 2011, Kayenta's Sarahsaurus was considered a species of Massospondylus, and the latter genus was first recorded in South Africa, while Anchisaurus originated in America.
• Falsely Advertised Accuracy: The Zuni raptors were based on two partial specimens of what was thought to be a new species of dromaeosaurid found alongside Zuniceratops and Nothronychus in the Moreno Hill Formation, but while When Dinosaurs Roamed America was in production, it was realized that these fossils represented a more basal type of coelurosaur (later identified as the tyrannosaur Suskityrannus in 2019). As a compromise, the producers added an unnamed small coelurosaur into the segment, while the dromaeosaurs became entirely speculative creations. Granted, dromaeosaurs are known to have inhabited North America all throughout the Cretaceous, so it's plausible that they lived in Turonian New Mexico, but no direct evidence of their presence has been found yet.
• First Appearance: When Dinosaurs Roamed America has the distinct honor of featuring the very first screen appearance of feathered non-avian dinosaurs (Nothronychus, Ornithomimus, and the Zuni raptors and coelurosaur), as well as the first screen appearance of a therizinosaur (Nothronychus), beating the Therizinosaurus from Chased by Dinosaurs by a year.
• Follow the Leader: To Walking with Dinosaurs.
  • Though they definitely tried to avoid this when selecting the cast, as they revisit three of the same biomes as WWD. The Late Triassic segment once more has Coelophysis as the focal character, but instead of the dicynodont Placerias and rauisuchid Postosuchus, we have the aetosaur Desmatosuchus and phytosaur Rutiodon as the large, non-dinosaurian herbivore and carnivore respectively. Similarly, the Late Jurassic segment features Apatosaurus and Camarasaurus in place of their respective relatives Diplodocus and Brachiosaurus, and gives plenty of focus to Dryosaurus and Ceratosaurus. ^note  Apatosaurus and Dryosaurus were included in the WWD special The Ballad of Big Al, which aired a year before When Dinosaurs Roamed America, while the latter was in production.
• Ripped from the Headlines: The Zuni Basin segment was definitely this for 2001, due to the then-recent description of Zuniceratops and Nothronychus (with the latter being named the same year the series aired), as well as the overall exciting find of the Moreno Hill Formation, which yielded several basal predecessors of iconic Late Cretaceous dinosaurs from North America, such as ceratopsians, hadrosaurs, and tyrannosaurs (with the “Zuni raptor” turning out to be a basal tyrannosaur, Suskityrannus).
• Science Marches On:
  • It's likely a meteor strike was not the primary cause of the Permian or Triassic extinction (both are believed to have been due to mass volcanism events).
  • Coelophysis probably did not exist 220 MYA, its fossils are only conclusively known from layers of rock less than 210 MY old (although the coelophysid Camposaurus, once considered a Coelophysis species, are that old).
  • The Coelophysis is briefly seen being warded off by a traversodontid cynodont. This cynodont is likely based on teeth from the Chinle Formation at the time considered to belong to a tranversodontid of relatively large size. However, these teeth, named Kraterokheirodon in 2005, have since been reevaluated and now thought to be too undiagnostic to classify beyond "amniote". A definite cynodont has since been found from the formation, named Kataigidodon, but it was only about mouse-sized.
  • Coelophysids and dromaeosaurids are now thought to have been nocturnal hunters. That said, many extant nocturnal hunters, such as felines and foxes also hunt during the daytime if need be.
  • Subsequent dating of the Kayenta Formation, where Dilophosaurus and "Syntarsus" hail from, suggests that it's younger than traditionally thought, representing the upper Pliensbachian (circa 185 mya) rather than the Hettangian-Sinemurian (200-195 mya), meaning these theropods would have never met Anchiosaurus, though they did coexist with the similar Sarahsaurus (who also comes from Kayenta).
  • "Syntarsus" and Dilophosaurus are described as ceratosaurs. Subsequent classifications determined that coelophysids and dilophosaurs fall outside this group, and represent more basal theropod lineages.
  • The phylogenetic status of the coelophysid Syntarsus kayentakatae is notoriously convoluted. The name was subsequently deemed invalid, because it had already been used as a junior synonym of the beetle genus Cerchanotus, and later workers included it within Megapnosaurus and even Coelophysis itself, which would mean the latter taxon survived the Triassic-Jurassic extinction. A 2021 paper then concluded that it was part of neither and might indeed represent a wholly different genus, who would also need a new name.
  • Dilophosaurus was actually even more formidable than shown in the series. A 2020 paper reexamining all the known specimens revealed that the skull was stronger and had a more robust jaw with strong jaw muscles, meaning Dilophosaurus had a powerful bite. Also, the spike jutting from the back of crest isn't widely considered anymore; more likely the whole crest curve was much larger than traditionally restored.
  • Anchisaurus and other "prosauropods" were most likely obligate bipeds.
  • Ceratosaurus was by no far stretch the last ceratosaur; if anything, it was one of the earlier ones, and its lineage gave rise to the abelisaurs such as Majungasaurus and Carnotaurus. Ironically, it's shown getting killed by the much larger Allosaurus, as if to imply the latter's lineage would supplant the ceratosaurs, when in reality, the allosaurs ultimately died out during the Middle Cretaceous, while the abelisaurids made it all the way to the K-T extinction.) Though Ceratosaurus was indeed the last of its kind in North America specifically.
  • Stegosaurus is shown with four clawed toes on its front feet, but footprints attributed to stegosaurs showed they only had two clawed toes (and a third, clawless toe encased in flesh). The sauropods are also shown with four clawed toes on their front feet, but they had only one, a single spike-like claw.
  • The Apatosaurus is very clearly a pastiche of the Walking with Dinosaurs Diplodocus, including giving it a horizontal neck, but this is considered less likely these days, and it seems plausible diplodocids held its neck upwards in a neutral position instead of horizontal, and the ability to do so would have been widespread among sauropods.
  • One of the talking heads interviews states that Brontosaurus is now known as Apatosaurus, but in 2015 the decision was tentatively reversed and Brontosaurus was rendered valid again (although not every paleontologist agrees).
  • Sauropod eggs have been found in the Morrison formation, even of Camarasaurus, a sauropod featured in the show.
  • Sauropods are stated to rely on gastroliths to process vegetation in their gut, which was a widely held hypothesis of the time, but is now considered unlikely. More likely, the vast size and volume of their digestive system allowed for prolonged fermentation to more effectively extract nutritional value, and stones were sometimes just swallowed accidentally.
  • Being the earliest example of feathered dromaeosaurs to appear on screen, the Zuni raptors, naturally, haven’t aged very gracefully, being depicted as more or less typical 90s dromaeosaurs but covered in simple, down-like feathers and with scaly faces and arms. We now know that dromaeosaurs were essentially flightless Toothy Birds with feathered faces and sported bird-like branching feathers, complete with clawed wings and a tail-fan.
  • Dromaeosaurids are now thought to have used their claws for gripping and clinging rather than slashing.
  • The Zuni raptors and small coelurosaurs were based on the same fossil, first thought to be a dromaeosaur, later an indeterminate coelurosaur, until 2019, when it was named and described as an early tyrannosaur called Suskityrannus hazelae.
    • This was actually discovered midway through production, so the producers added the little coelurosaur at the last minute, despite not having much of a role in the segment.
  • While only 3 meters long, the two known specimens of Suskityrannus are juveniles, with one being only 3 years old based on the growth rings in its bone, so mature animals would have been larger (as shown in Planet Dinosaur), though how much larger remains speculative.
  • There is no evidence that female Tyrannosaurus were larger than males. The robust and gracile morphs within Tyrannosaurus rex that inspired this idea are now thought to represent geographic variation (potentially different subspecies) or possibly variation through time.
  • The juvenile T. rex are depicted very similar to adults, while more recent discoveries show they were much more lithe and slender than shown in the documentary (it is said in the documentary that the juveniles' legs were longer but the CGI showed little difference).
  • Although Ornithomimus was portrayed with feathers, it is now known they had much more than shown, possibly even having fully feathered wings like birds or dromaeosaurids.
  • Quetzalcoatlus is portrayed as a vulture-like scavenger that was "a fish out of water" (to quote the narrator) when it wasn't flying. It is now pretty certain that it was quite proficient at walking and would probably be able to gallop after live prey up to the size of humans. Also, it is correctly depicted with pycnofibres, but not enough (all pterosaurs probably had full coats of pycnofibres).
  • It has typical pterodactyloid proportions, a small body and proportionally very long wings, but in azhdarchoids, it was the opposite, as they had very short wings proportionally to their bodies. Quetzalcoatlus itself stood around 4 to 5 meters tall when on the ground (as tall as a giraffe), but its wingspan was only a little over double that length (10-11 meters). Hence it weighed more than 200 lb, as present estimates put it around two to three times that weight.
  • "Anatotitan" has since been deemed a synonym of Edmontosaurus. It should also have a squared-off keratinous beak in front of its duckbill-like snout (thereby hiding its duckbilled shape in life).
  • Hadrosaurs could not chew by moving their mouths from side to side, they actually moved their top jaw front to back.
  • The Cretaceous is thought to have ended 66 MYA, rather than 65 MY.
  • Grass had evolved by the end of the Late Cretaceous, although grasslands would not appear for another thirty million years.
• Working Title: Dinosaurs of North America.
• What Could Have Been: There was going to be a segment on the Campanian featuring Albertosaurus, but while it did make it into production long enough for a maquette to be made of it, it was scrapped, presumably due to being too similar to the Hell Creek segment.