an unofficial scientific guide to “fresh water”
The third episode of prehistoric planet takes viewers away from the hot sands and into freshwater environments.
The opening scene of “Freshwater” focuses on a trio of Velociraptor as they ambush a pterosaur, which may be a tribute to Earthstunning pictures of snow leopards. It also seems to refer to a fossil find in which a pterosaur bone was discovered in the stomach contents of a Velociraptor fossil, although the article states that it was probably a salvage case, due to the size of the pterosaur.
prehistoric planet then returns to North America, and to T. rex. This scene aims to erase some misconceptions about the world’s most infamous dinosaur. The first is that Tyrannosaurus was a scavenger, like this male T. rex is shown to have killed (offscreen, for the kids) a Triceratops. The hunter-versus-scavenger pairing is largely a human design – few terrestrial carnivores will pass up a free meal, and even animals characterized as scavengers, such as the spotted hyena, will do quite a bit of hunting.
Additionally, a study by Thomas Holtz showed that tyrannosaur-dominated Late Cretaceous ecosystems in Asia and North America lacked many of the medium-sized carnivores that were found in earlier ecosystems (so there was no no other carnivore species to recover). The implication is that young tyrannosaurs would have occupied the ecological niches normally occupied by mid-sized carnivores.
The second misconception is that the woman Tyrannosaurus were larger than the males. That might have been true, but it’s nearly impossible to determine the sex of an extinct dinosaur, and even harder to get a data set substantial enough to determine whether females were generally larger, or whether it’s is simply that larger female individuals fossilized. That being said, there is a way to try to determine if a dinosaur was female – by examining the marrow cavity of the bone.
In birds, the medullary cavity fills with calcium in preparation for egg laying. This only happens when the bird is pregnant, but if you find a fossil with the marrow cavity filled in, it could mean you have a female that was pregnant. Such an examination was carried out on a Tyrannosaurus specimen, which found fossilized tissue that appeared consistent with marrow bone, suggesting the specimen was female, but more work needs to be done before anything like a sex-height correlation can be determined.
When it comes to mating behavior, a 2017 study showed that one parent of Tyrannosaurus, Daspletosaurushad scales along its face that showed a strong correlation with the facial sensory organs of crocodilians, so a pair of tyrannosaurus rex is quite reasonable.
prehistoric planet then returns to Central Asia, but this time to a flooded delta and the truly incredible Deinocheirus mirificus. Originating from the Nemegt formation in Mongolia, Deinocheirus was described in 1970 by Halszka Osmólska et al of a pair of massive arms, eight feet long from shoulder to finger. From these arms it was determined to be a theropod, but the exact nature of the animal was unknown. And it remained that way for more than 40 years.
But in 2012 it was announced that much of the original specimen had been found, and in 2014 the description of the animal was published. The result is the bizarre animal depicted in prehistoric planeta giant ornithomimid (like Gallimimus) with an oddly proportioned skull and elongated spinal vertebrae that may have supported a fat hump. Although we don’t know for sure if the huge Deinocheirus was covered in feathers as depicted in the show, two of its tail vertebrae were fused together in a way resembling the pygostyles of relatives like therizinosaurus. Pygostyles in birds help support feathered tail fans, suggesting that Deinocheirus also had a fan of feathers along its tail.
The final stage of this episode of prehistoric planet takes viewers to southern Africa and one of the show’s most speculative portrayals to date. The scene begins with the giant azhdarchid Quetzalcoatlus arriving. Quetzalcoatlus is not known from remains in Africa; in fact, the only conclusive fossils of Quetzalcoatlus come from the United States, but azhdarchids have long been considered quite efficient flyers and therefore able to travel long distances through thermal soaring.
One of the beauties of science is that it continues to evolve and new analyzes keep coming in, and published just this year was a study by Yusuke Goto et al who questioned the burgeoning abilities of the azhdarchids as Quetzalcoatlus, and concluded that they were probably short-range thieves. This lack of efficiency does not necessarily mean that they could not cover greater distances, however, and given the diversity of azhdarchids, it is possible that southern Africa also had its own local pterosaurs. For those who wish to read more scientific literature on Quetzalcoatlusthe Journal of Vertebrate Paleontology released a massive special edition on them last year, and it’s all open access.
The next animal viewers are featured to also help determine where we are in Southern Africa – Masiakasaurus knopfleri is known from the Maevarano Formation in Madagascar. The representation of Masiakasaurus also features a piece of speculation, in that it is depicted with fine, delicate feathers between its scales. This is interesting because Masiakasaurus is only distantly related to coelurosaurs (the group that includes tyrannosaurs, dromaeosaurus, ornithomimids, alvarezsaurs, therizinosaurs, oviraptorosaurs, troodontids, and birds, all of which have direct evidence of feathers).
Masiakasaurus is actually a noasaurid, a type of ceratosaur, and therefore a member of a more basal theropod lineage. Outside of coelurosaurs, it is unclear how widespread feathers were among dinosaurs. animals like Psittacosaurus and Kulindadromeus both had integument that could have been feathers, which would make feathers an ancestral trait for all dinosaurs.
Additionally, an April 2022 study of the fluffy pycnofibers that covered pterosaurs showed that these structures could also be feathers, which would neatly push back the origin of the structure. before dinosaurs. This doesn’t mean that all dinosaurs had feathers, but it does mean that we could see them in species that we would otherwise assume had none.
prehistoric planetis poor Masiakasaurus newborn is attacked by the giant frog Beelzebufo ampinga, which was found in the Maevarano formation with Masiakasaurus. It is important to remember that these are small animals — Beelzebufo was big for a frog, but it wasn’t a monster. Recent estimates having its length from snout to vent at 245 mm (or just over 9.5 inches).
The final scene of “Freshwater” depicts a group of elasmosaurs swimming in brackish water near the shore. No elasmosaur fossils have yet been found in Madagascar but, as mentioned in the episode 1 breakdown, elasmosaurs as a group had a worldwide distribution, so they would almost certainly have prowled the seas off Madagascar. ‘Isle. And while elasmosaurs are best known from marine sediments, animals like Fluvionectes have been found in non-marine environments, so it is also possible to see some of these reptiles in rivers.
Robert Reed will break down the interesting science notes in each episode of prehistoric planetso come back every day this week!
AIPT Science is co-presented by AIPT and the New York City Skeptics.
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