Today sees the release of the first episode of Prehistoric Planet, the new documentary series on AppleTV+. Narrated by David Attenborough, produced by Jon Favreau, and scored by Hans Zimmer, Prehistoric Planet covers the lives of animals from the late Cretaceous Period in a stunningly beautiful way that should spark the curiosity and imaginations of all who view it. This guide hopes to present some additional information and background for the science behind the depictions (so don’t read this until after you’ve watched it).
After the series introduction, “Coasts” begins in earnest along the shores of the ancient Western Interior Seaway which, at its peak, stretched from the Gulf of Mexico to the Arctic Sea, dividing North America into two landmasses — Laramidia in the west, and Appalachia in the east. However, by the Maastrichtian Age of the Cretaceous, the Seaway had receded from its northernmost reaches, though it still split the continent as far north as the Dakotas.
Interestingly, this opening scene with Tyrannosaurus rex takes place on the southern end of the sea. While T. rex is often associated with the Hell Creek and Lance formations of the United States and Canada, fossils of the animal have been found as far south as New Mexico, and teeth possibly belonging to T. rex or a close relative have been found in Mexico.
While we don’t have direct evidence of T. rex itself swimming, we do have fossil evidence of other theropods swimming, and a study on buoyancy based on estimated mass distribution showed that T. rex definitely should have been able to keep its head above water. So yes, T. rex was very likely a competent swimmer (Jurassic Park fans should be reminded of a scene from the first novel).
Also shown in the opening are unnamed 2,000-lb. turtles and a 15-ton mosasaur. Such large sea turtles did exist, the most famous being Archelon. While Archelon itself had gone extinct a few million years prior to T. rex evolving, the protostegid group to which it belonged lasted until the end of the Cretaceous Period, so this mystery turtle definitely isn’t out of place. As for the mosasaur, that group of giant lizards was incredibly successful during the Cretaceous, with multiple members having been found across the globe. Though the mosasaur isn’t identified by genus, two candidates would be Tylosaurus and Prognathodon, as both navigated the Western Interior Seaway.
The lack of specificity could be taken as a negative; I can imagine 5-year-old me getting frustrated not knowing the exact name of every creature that appears on-screen. But the vagueness here actually struck me as refreshing. As much as we know about dinosaurs and their environments, the names of genera and species can be disputed (something I’ll discuss in greater detail in the breakdown of an upcoming episode), and stating “mosasaur” rather than “Tylosaurus” may ultimately prevent the documentary from dating itself, if fossils are later determined not to be Tylosaurus but some other animal.
That vagueness has another advantage. When the episode transitions to the pterosaur scene, it simply identifies the location as “Northern Africa.” Paleontologists and enthusiasts will easily peg this as taking place in the Ouled Abdoun Basin of Morocco, but by removing the national association of these locations, Prehistoric Planet better illustrates nature’s lack of political borders and reminds us that just because we’ve found fossils of an animal in one location, that doesn’t necessarily preclude them from appearing somewhere else.
This exciting scene highlights four pterosaurs which have all been described relatively recently. Pterosaur bones are extremely light, making their fossils exceedingly rare. So it was a surprise in 2018 when paleontologists Nicholas Longrich, David M. Martill, and Brian Andres described four of them from Morocco. Three of the pterosaurs from that paper make prominent appearances here: Tethydraco regalis is the first introduced, Alcione elainus is represented by the hatchlings desperately trying to reach the forests, and Barbaridactylus grandis are the ornately adorned ones that attack the hatchlings upon launch.
The remains of each of these pterosaurs are incredibly fragmentary, so we have no direct evidence of those spectacular crests on the Barbaridactylus. But we do have enough evidence to know that Barbaridactylus belonged to a group of pterosaurs called nyctosaurids, which gets its name from the North American genus Nyctosaurus. A specimen of that genus did have a tuning-fork-like crest very similar in size and shape to that shown here on Barbaridactylus, so it’s not out of the realm of possibility that Barbaridactylus did have something similar.
The fourth pterosaur shown, the stork-from-hell Phosphatodraco mauritanicus, was described in 2003 by Xabier Pereda-Suberbiola et al. It’s an azhdarchid, a group of pterosaurs that gave the world the largest flying creatures ever. They became successful in the Cretaceous Period, so you might want to get used to them — you’ll be seeing more representatives in later episodes.
Prehistoric Planet then moves to the drowned continent of Zealandia. Unlike Lemuria, Mu, Atlantis, and the weird hollow Earth ideas that were popular in our past, Zealandia is actually a real thing: a continent that became almost completely submerged earlier in the Cretaceous. Today, two prominent parts of Zealandia that remain above water are New Zealand and New Caledonia.
The creatures we see here are Tuarangisaurus keyesi, a type of elasmosaur discovered in New Zealand. Elasmosaurs themselves are a type of plesiosaur, most readily picked out by their extremely long necks. Elasmosaurs were an extremely successful group, with members known from every content. The Tuarangisaurus are shown eating pebbles to aid with their aquatic lifestyle and to help with digestion, creating gastroliths (stomach stones). This is actually something relatively new to our understanding of Elasmosaurs, as José Patricio Gorman et al described the first record of gastroliths in elasmosaurs in 2013.
Prehistoric Planet then takes viewers to southern Europe, “where the Atlantic meets the great Tethys Sea.” The Tethys Sea or Tethys Ocean existed between Europe, Africa, and the area now occupied by the Indian Ocean. The animal we meet here is called “Hoffman’s Mosasaur,” which is a more colloquial way of identifying Mosasaurus hoffmanni. This is THE mosasaur, the original one described, which lends the entire group its name.
The discovery of the Mosasaurus skulls in the Netherlands in the late 1700s saw the animal first misidentified as a whale, while Johann Leonard Hoffman felt it was a crocodile. The genus would not officially be named until 1822, when William Daniel Conybeare described the fossil. But even then, no specific epithet was ascribed until Gideon Mantell named it hoffmanni, after Hoffman, in 1829.
Attenborough’s narration correctly identifies mosasaurs as lizards, though there’s ongoing debate as to whether or not they’re more closely related to snakes (which, as a reminder, are lizards in the phylogenetic sense) or monitor lizards. Because both snakes and monitor lizards have forked tongues, we can use phylogenetic bracketing to infer that mosasaurs likely did as well.
Phylogenetic bracketing is a scientific process through which we can make inferences based on organisms’ relationships to each other. If we have three animals, A, B, and C, and we know they share a common ancestor, with A being basal to B and C (basal meaning closer to the root of the tree), if A and C share a trait, we can infer that B likely did as well, unless there’s direct evidence to the contrary (and yes, we have lots of evidence of mosasaurs attacking and even consuming other mosasaurs).
Along with Mosasaurus, this scene also depicts pycnodont fish, an order of fishes that survived the mass extinction at the end of the Cretaceous, but disappeared during the Eocene Period. Even though fish are an important part of our ecosystems, fossil fish rarely receive any media attention unless the fish itself is particularly dramatic, so seeing a reconstruction and identification of an extinct order of fish that aren’t physiologically flashy is one of the cooler moments of this episode.
Prehistoric Planet then returns to North America, though this time on the Atlantic coast. Viewers are treated to a beautiful display of bioluminescence in a school of scaphitid ammonites. Ammonites were an extremely successful group of molluscs, first showing up in the Devonian Period and lasting into the Paleogene, just after the extinction event at the end of the Cretaceous. Because of their anatomy, we largely only have the fossilized shells of these ancient creatures.
However, in 2021, newly described, exceptionally preserved material offered the first good look at their soft tissues. While we don’t have any direct evidence of bioluminescence in ammonites, every extant type of cephalopod boasts at least one example that’s evolved it, as have other molluscs including gastropods. So using phylogenetic bracketing, we can infer that some ammonites would have had this ability as well.
Finally, the debut episode of Prehistoric Planet ends in dramatic fashion, as the Tuarangisaurus fend off an attack from the mosasaur Kaikaifilu hervei, first described in 2016 by Rodrigo Otero et al based on fossils discovered in Antarctica. Just as with the pterosaurs earlier in the episode, one of the highlights of “Coasts“ is the decision to focus not just on famous creatures, but to highlight new discoveries, too.
Robert Reed will be breaking down the cool scientific notes in each episode of Prehistoric Planet. Check out what he spotted in episode 2, “Deserts”!
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