This post is the second of my "Invertebrates in Paleomedia" series, where I look at major depictions of extinct invertebrates and discuss their accuracy, since they're often overlooked in other reviews.
You can read the first entry on the Walking With… series here -https://invertposting.blogspot.com/2024/04/the-invertebrates-of-walking-with.html
I highly recommend that you do, as today's documentary, Life On Our Planet, makes many of the same mistakes as Walking With Monsters (which is approaching 20 years old).
I’m only gonna cover the prehistoric segments, which means starting off with the second episode. Chapter 2 - The First Frontier covers the Hadean up until the late Devonian, featuring a handful of "major" marine invertebrates. There's Anomalocaris, Endoceras, and trilobites, but nothing too crazy nor distinct unfortunately.
The first (macro)invertebrates we see are modern, but "primitive" (a label I disagree with), used to show what early marine life may have been like 575 million years ago. There's sea pens, crinoids, anemones, corals, bivalves, sea cucumbers, and nudibranchs - a bit egregious for Ediacaran proxies. The Ediacaran would’ve been home to simple, mostly flat benthic animals grazing on microbial and algal mats.
Even though the modern stand-ins are not anatomically similar, their generally sessile nature and inability to escape predation gets the general gist across as to what would've been occurring in the oceans around that time, which may have resulted in the nektonic animals characteristic of the Cambrian.
The episode jumps ahead in time to 530 million years ago to show some of the earliest members of these communities - jellyfish. As far as I can tell, fossils for all four major groups considered jellyfish (Cubozoa, Scyphozoa, Staurozoa, and Hydrozoa) all first appear in latest Ediacaran or early Cambrian, so this time is a decent generalization, albeit probably not the best, and the extant stand-ins are reasonable (although, for once, I'd love to see an actual extinct jellyfish in a documentary).
Jumping forward once more to 508 million years ago, this segment seems to take place in the Burgess Shale, but does not make use of the wide variety of fauna unfortunately. Instead, just like Walking With Monsters, it's only good ol' Anomalocaris and trilobites. The companion book at least mentions the normal weirdos like Hallucigenia and Opabinia. It also mentions Fuxianhuia, a fossil arthropod which preserves the earliest known cardiovascular system (Ma et al. 2014).
The trilobite featured is Olenoides serratus, and it's a genuinely good depiction. The anatomy is sound, featuring both the front and rear antennae, and the behavior is well done - rolled up specimens of other trilobites are well known from the fossil record, while the mass spawning pulls from horseshoe crabs (likely due to the anatomical similarity of their claspers, Losso and Ortega-Hernández, 2022).
Meanwhile, the Anomalocaris is just as bad, if not worse, than Walking With Monsters' but does not have the excuse of time. The anatomy is wonky, as shown below.
Note - I'm unsure of where this image originally came from
And as I said in the WWM article, Anomalocaris would not be capable of processing hard prey - unable to manipulate it with its front appendages, nor eat it with its mouth cone. Research suggesting such has been around since 2012. Some have tried to defend this scene by suggesting the Anomalocaris was desperate, or that it was simply going after something it wouldn't be able to take on (this does happen a lot in nature), but this is a fictional documentary - they did not need to show Anomalocaris going after a trilobite, they chose to, which is inherently inaccurate. The Burgess Shale preserves a multitude of interesting soft-bodied animals that could've filled the role of "early arthropod that gets eaten"; Isoxys, for example.
By the way, the Burgess Shale Anomalocaris was not the "world's first superpredator" as is often touted, radiodonts from China and Australia are nearly ten million years older.
The episode jumps to 468 million years ago to depict the larger predators of that era, specifically Endoceras (which is a bit jarring, some may wonder where these cephalopods came from). There's a rich sponge and coral reef, using modern fauna which is fair, but there's an unfortunate lack of crinoids.
The trilobite featured here appears to be Paraceraurus, an interesting spiny one. As usual, it serves no other purpose than to get attacked by a large predator - this time Endoceras. Oddly enough, the trilobite makes chittering noises and has red blood; I'm unaware of any study suggesting trilobite blood color, but extant insects, crustaceans, and horseshoe crabs tend to have clear/blue blood due to composition and how they process minerals, I don't see why trilobites would be any different. I’m also unaware of any close relatives or ecological analogues that make noises, especially not rodent-like squeals.
Life On Our Planet calls the Endoceras "Cameroceras" again, years after the taxonomy of giant specimens was sorted out (Klug et al. 2015). The narration also states that Endoceras is 8 meters long, when it would've really been 6 (something the companion book gets correct).
Tyler Greenfield gives some criticisms here - https://twitter.com/TylerGreenfieId/status/1694054668576637057, noting that the anatomy of this model is even worse than the one in Chased By Sea Monsters, which was 20 years old by the time Life On Our Planet released.
With that said, the behavior of Endoceras is beautifully presented, and this scene is easily one of my favorites in all of paleomedia - the looming presence of these cephalopods reminds me a lot of the Triffids. The algae on the shell is a very nice touch, by the way.
The episode then jumps forward to the Ordovician extinction, using footage of brinicles to show the effects of an ice age on the ocean. The survivors of this extinction had to retreat to deep water, something shown by a modern nautilus, a close relative of Endoceras.
The narration further perpetuates the "living fossil" stereotype, generalizing the evolution of nautiloids and suggesting that the extant nautili evolved in the Ordovician when this is far from the case - modern nautilus evolved in the Eocene and many Paleozoic nautiloids looked nothing like these modern relatives.
The idea of a "living fossil" is inaccurate at best or harmful at worst; when poorly explained it undermines evolution as a whole (many "living fossils" are used as evidence for creation), and can also lead to many misconceptions, such as "crocodiles haven't changed since the time of the dinosaurs" or the idea that living coelacanths make it plausible for mosasaurs, megalodon, or non-avian dinosaurs to still be alive. It's not an egregious error, but certainly an unfortunate one.
After some time with extant cephalopods, the series jumps back in time to the late Devonian, 374 million years ago (skipping over the entire Silurian). It's here where the invertebrate focus ends essentially, but there is still an invertebrate in this segment - the ammonoid Gonioclymenia.
The model has ten arms which is the basal condition for cephalopods, while later ammonites have eight arms and two long tentacles - the number shown is conservative but reasonable. These ammonoids also appear to have a distinct, large operculum which should not be present. Ammonoids were not closely related to the nautilus; ammonoids are part of Neocephalopoda, a group which excludes nautiloids entirely.
That concludes Chapter 2. This episode was serviceable, albeit not great - it did not bring much of anything new or up to date to the screen, but does give a reasonable explanation of what occurred in the early Paleozoic.
Chapter 3 - Invaders of the Land attempts to focus on the first terrestrial animals, but manages to skip over at least 60 million years of terrestrial evolution. This is somewhat amended in the companion book, which briefly discusses Pneumodesmus, an early myriapdos and one of the first terrestrial animals.
Pneumodesmus has a full tracheal system, including spiracles (holes that allow oxygen to enter the trachea) which could only function on land. There are apparently older trace fossils from the Ordovician of myriapod-like animals, but no body fossils (Wilson and Anderson, 2004).
The companion book also mentions the Rhynie Chert, a remarkable early Devonian site that preserves a multitude of beautiful invertebrate and plant/fungi specimens, including the famous giant Prototaxites. The companion book also makes note of the trigonotarbids, referencing Palaeocharinus known from several species found at the Chert. The book specifically notes that these arachnids lacked venom (Dunlop, 1994) and silk, the earliest evidence of which comes from the Uraraneid Attercopus (Sheldon, Sear, & Sutton, 2008).
The Chert also preserves herbivorous mites and springtails, as well as other predatory invertebrates, fully preserving one of the earliest terrestrial ecologies. The fact that LOOP skipped over this is incredibly unfortunate, but it does seem that Surviving Earth will feature this ecosystem, so I’ll likely talk about it more very soon.
The episode’s first invertebrates are from the Carboniferous, 345 million years ago. There’s a burrowing cockroach (Macropanesthia), likely acting as a stand-in for the omnipresent “roachoids”, a paraphyletic group of roach-like early insects, and a scorpion (which were quite prominent during the Paleozoic) which is used to give a sense of scale for the giant Arthropleura.
This episode (and the companion book) continues to perpetuate the idea that oxygen was the primary factor that resulted in arthropods getting bigger, when this simply is not true. Although higher oxygen levels may have acted as a cushion, making the jump to giant size just a bit easier, the lack of competition was the main, if not sole factor behind this, as shown by the Silurian Brontoscorpio, and the Permian Arthropleura/griffinflies (which were the largest of their genus/groups).
https://www.pnas.org/doi/full/10.1073/pnas.1204026109
https://chooser.crossref.org/?doi=10.1144%2Fjgs2021-115
https://revistas.ucm.es/index.php/JIGE/article/view/JIGE0808120115A/32759
This Arthropleura model is beautiful! It does not have giant centipede-like fangs, eyes on the collum (the plate before the head on millipedes; popular reconstructions of Arthropleura treat this as the head proper and place eyes/antennae on it), and seemingly triangular telson (tail segment) - incredibly up to date and accurate, the model looks just like this reconstruction from Pillola and Zoboli, 2021.
The behavior is beautifully done too, the Arthropleura bumping into the log directly pulls from one of the consultant's, Dr. Tom Fletcher (who also wrote the book) own millipedes he was in charge of - one of which would keep bumping into a pencil on his desk.
There's also an Arthropleura curled up into a ball, only coaxed out of this position by stridulation (rubbing parts of the shell together to "sing"), I can't understate how much I love this! Millipedes today don't have hearing organs, so instead rely on detecting vibrations - in extant giant pill-millipedes males attempting to mate stridulate when approaching females so as not to trigger the "rolling-in reflex", where a millipede instinctive curls into a ball at the first sign of danger (Wesener et al. 2011).
The mating posture pulls from extant millipedes mating, which is supported by the fossil record - trackways from Scotland preserve traces of a similar mating posture (Whyte, 2018).
https://www.youtube.com/watch?v=j__gK5fnRgY
This scene is above and away the best in the series, it's stunningly beautiful and very well done scientifically; one can only imagine how good the series would be if this level of effort was put in across the board.
The doc spends some time with extant peacock spiders, tiger beetles, and dragonflies, but does not return to Carboniferous inverts, unfortunately. In fact, there are no prehistoric invertebrates until Chapter 5 - In the Shadow of Giants. Briefly, the book mentions mortichnium (the traces of a dying animal), which I've posted about here.
The episode depicts two major points in invertebrate evolution during the Mesozoic - the Angiosperm Revolution and the evolution of eusocial insects. For those unfamiliar, the Angiosperm Revolution was a major change in the flora during the early Cretaceous, in which other plants were heavily displaced by angiosperms due to their efficiency. Other plants relied primarily on wind, water, or insect pollination, while angisoperms could be pollinated by vertebrates or invertebrates much more reliably. This resulted in a major boom in invertebrate diversity, resulting in many modern groups like butterflies and bees, a much more detailed breakdown of which can be read about in Benton, Wilf, & Sauquet, 2021.
LOOP uses the extant example of the giant water lily (Victoria amazonica), and Cyclocephala scarab beetles. This relationship appears to be an old one, as members of both families have existed since the Cretaceous (Woolley, 2016, Coiffard et al. 2013), and Nympaeaceae tend to be very specialized towards their pollinators.
The narration puts emphasis on the color of the flower and the odor it emits, two kinds of pollination syndromes, or traits that a plant has evolved specifically to attract their unique pollinator - the ability to attain this level of specialization is likely directly responsible for the boom in insect and plant diversity during the Cretaceous. Beetles and wasps were likely the first pollinators; bees and butterflies first appeared and diversified around the middle/late Cretaceous.
This rampant diversity led to many predatory taking advantage of these pollinators - mantes and spiders diversified heavily by the mid/late Cretaceous, so forms similar to the modern orchid mantis (Hymenopus coronatus) would likely be present. Interestingly, the documentary depicts a chameleon as an example of an invertebrate predator; chameleons did not evolve until the Cenozoic, but the albanerpetonids filled the same role, even having similar ballistic tongues (Daza et al. 2020). Spiders evolved the modern orb web, the one you think of when you think of spiders, around this time a summary of which can be found here.
This boom in diversity also resulted in the evolution of eusocial insects - the ants, termites, and bees, all of which first appear in the Cretaceous. The companion book specifically notes that termites were the first wood-eating, or saproxylophagous animals, however borings in wood may suggest that beetles were eating wood as early as the Permian (Feng et al. 2017), and members of Passalidae first appear at the same time as termites. Wood eating likely evolved from xylomycophagy (feeding on fungi) or detritivory, although the evolution of such is not fully understood (Beza-Beza et al. 2023)
This boom in Cretaceous diversity established many groups of insects and was one of the largest key events in insect evolution, seeing it depicted in such detail was great to see in this documentary especially since invertebrate evolution past the Paleozoic is often ignored entirely.
Unfortunately, that's the last bit of screentime invertebrates get in Life On Our Planet. A majority of the key points were touched on perfectly, and some depictions of the extinct invertebrates are arguably the best they've ever been, and certainly have earned their spot amongst my personal favorite sequences in any paleontology documentary.
I'll be covering Sea Monsters - A Prehistoric Adventure next, as well as posting on a speculative evolution project and some other recent invertebrate papers in the upcoming week, so keep an eye out for that.
Some papers can be read here - https://drive.google.com/drive/u/3/folders/11GVZcfH2T98r8YVd9xdCvMzuj-uFscpp
