Interview with Abby Howard, author and artist of the Earth Before Us series

Following on from last months' review of Luis Rey's Extreme Dinosaurs Part 2, this month we're spotlighting another palaeoart-heavy book - or rather, books - by comic author and illustrator Abby Howard: the Earth Before Us series. This trilogy of educational graphic novels has been published over the last three years, beginning with the Mesozoic-focused Dinosaur Empire! in 2017, then the Palaeozoic Ocean Renegades! in 2018, and finally the Cenozoic Mammal Takeover! earlier this year. It's no exaggeration to say that I can't think of enough nice things to say about these books: they are genuinely some of the best child-focused palaeo outreach I've ever seen. I've actually had to buy two copies of all three, as my first set - which was meant as a present for my nephew - didn't quite avoid assimilation into my library. If being moved to steal from children is not a recommendation for Earth Before Us as a Christmas gift, I don't know what is. 

What they're calling "the best trilogy since the original Star Wars films": Abby Howards' Earth Before Us series. Available now from Amulet Books (1st, 2nd and 3rd books) as well as good online book retailers.

To celebrate the completion of the Earth Before Us series a few months ago, I invited Abby for an interview here at the blog, and she has very kindly agreed and furnished me with images to show off the books. Abby's background saw her skirting close to academia with studies into evolutionary biology, but she took a left turn into the world of writing and illustrating comics. Abby has created the ongoing webcomic Junior Scientist Power Hour and The Last Halloween (as well as many more projects - see her online portfolio) and these are well worth your time (I'm still partway through The Last Halloween and mean to finish it soon). But before I hand the reigns of the blog over to her, I want to briefly outline why the Earth Before Us books are so terrific, and why they're a must-buy for any young palaeo fans in your life.

Each of the Earth Before Us books is an affordable (RRP £10.99/$15.99), well-produced hardback with a solid, durable feel, of about 130 pages long*. They feature the time-travelling adventures of two characters, school pupil Ronnie and her palaeontologist friend and mentor, Miss Lernin. Initially inspired to visit the Mesozoic to help pass a class exam on dinosaurs, Miss Lernin and Ronnie then travel to the Palaeozoic after visiting an aquarium (Ronnie is surprised at the antiquity of many invertebrate lineages) and the Cenozoic when Ronnie wants to see how ancient humans dealt with cold. These human plots are really narrative bookends and, instead, the pacing and story developments stem from the evolution of life throughout the Phanerozoic. Journeying rapidly through time and space, our characters visit different organisms and locations so that the books never become boring or repetitive, swapping intimate moments with small critters to double-page spreads packed with gigantic animals. There are no clunky narrative devices to move Miss Lernin and Ronnie around, either. Save for starting their journeys in time by climbing into various bins (of course), they otherwise instantaneously travel to wherever they need or want to be, and without fear of the consequences. It's a smart narrative device that reminds me of the 'Ship of the Imagination' used in the TV series Cosmos, focusing attention on what our protagonists have to say, and the worlds they encounter, rather than tying them to a tedious travelling mechanism. They periodically return to the Learning Centre, a tranquil location equipped with a whiteboard that's periodically visited to explain a major concept of biology or palaeontology, but otherwise Miss Lernin and Ronnie move through time and space with pace and fluidity.

*I learned when finishing this article that paperbacks are now also available, RRP. £6.99/$9.00 

This speed is not to say that Earth Before Us skimps on detail, however - far from it. These books are dense, with heaps of information and depictions of extinct organisms, landscapes and climatic conditions. In the wrong hands, this could be overwhelming, or a barrel full of outdated data and misinformation. Neither fear is realised. Abby is terrific at distilling complex geological, evolutionary and anatomical information to words which are understandable to young people and lay audiences, all without dumbing down or patronising her readers. The interpretations she presents are accurate to modern science, and she takes time to explain why some ideas are superior to others or where gaps lie in our knowledge. The scientific concept is a major success of the books, and teachers, parents, exhibition designers and other authors looking for effective ways to teach natural history should pay close attention to her craft. Topics such as cladistics, extinction events, speciation, natural selection and so on have rarely seemed so graspable, and I can only see these books as a window into a wider world of learning for readers young and old.

Double page spread of Late Cretaceous South America from Dinosaur Empire! - note the swimming birds and fluffy baby Carnotaurus. I really like the sense of scale in these images: the human characters obviously help a lot in this regard, but the use of light and space does a lot of heavy lifting too. © Abby Howard.

As demonstrated by the accompanying images (kindly provided by Abby - many lack their speech bubbles so we can see the art more completely), the artwork in Earth Before Us is superb. Abby's illustrations are wonderfully clear, detailed, and characterful. On more than one occasion I found myself chuckling over the wordless reactions or expressions of the protagonists (see, for example, Miss Lernin's reaction to Ronnie riding a Tyrannosaurus, below). The fossil species are also well-executed, being thoroughly modern (lips and fibres abound on dinosaurs, animals are given generous amounts of soft-tissues etc.) and anatomically accurate enough to be recognisable to their fossil skeletons. The presence of human characters on every page gives a great sense of scale to the animals and, by using both in the animal's expressions and their interactions with Miss Lernin and Ronnie, Abby imbues heaps of character into her extinct subjects. It's clear that Abby sees extinct species as being animals, not monsters, adding another welcome contrast to so much child-focused palaeo content.

There's lots to like about the general tone of the Life Before Us series as well. They celebrate education and learning, and present knowledge and science as tools to solve problems. The arcs of each book involve Ronnie gaining greater knowledge and understanding of not just the past, but natural history and learning in general. Subjects that were once of no interest to her become fascinating, and in one book she's shown imparting her knowledge to others. The books are also not afraid of tackling difficult topics, such as climate change and our current biodiversity crisis. These are addressed in a frank, but also hopeful fashion, which is appropriate for younger audiences. I hope, as the books suggest, that these sections inspire children to ask more of adults as goes taking responsibility for these disasters.

Special attention must also be drawn to the main characters. Palaeontological outreach has a strong bias towards casting white men in prominent roles, and especially white men in wide-brimmed hats and field gear. As explained by Elsa Panciroli in an excellent 2017 article, this stereotyping of palaeontologists goes to the core of our profession. Like many sciences, palaeontology struggles with gender and ethnic diversity, and our lack of varied faces in outreach probably doesn't help this. It's very welcome, therefore, that the Earth Before Us books exclusively features two female protagonists, one of whom is black, and without a cowboy hat or rock hammer in sight. Miss Lernin even wears a dress throughout the second book, showing that you can have extensive knowledge about the history of life without wearing Gore-tex. Also noteworthy is that the books do not question the qualifications or intentions of its main characters either: there's no "but you're a lady?!?" revelation that Miss Lernin is the series' palaeontologist or whatever. The characters are simply allowed to be who they are without second-guessing. It seems strange to feel that this is such a big deal in 2019, but, times being what they are, I am very pleased to see Earth Before Us giving a much-needed injection of cultural, gender and ethnic diversity into mainstream palaeo media.

So, in sum, these are great books. The science and artwork are superb, they're both smart and funny, and they manage to make important points directly (climate change, extinctions) and subtly (gender and ethnic diversity). I can't recommend them highly enough, and even if your kids are a little too young to read them on their own, I think they'd be fantastic to read with them. But that's enough about what I think: let's see what Abby has to say about her work. All artwork shown here stems from Abby herself, and is reproduced with her permission.

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MW. The Earth Before Us books are packed with personality and charm, and were clearly written by someone with a major passion for natural history. How much of your own interests do they reflect? Do you share Miss Lernin's enthusiasm for just about everything that walks, crawls or flies, or did you initially have interests in a few fossil groups, and branched out for this project?

AH: Thank you! I did start each book with favourites in mind, but as I spent more time thinking about and researching the creatures in the series, I came to love almost all of them. The script is basically word for word the way I fawn over wildlife. I'm insufferable at museums and zoos.

It seems that if someone spends enough time researching a plant or animal, it's easy to become enamoured with it, which is fortunate for folks like me who may have started a book series about ancient beasts while not being particularly passionate about things like ancient echinoderms. As it turns out, they were really weird and interesting and fun to draw! I was also not so keen on temnospondyls for some reason, despite now feeling like they have great horror potential. We don't take their modern relatives very seriously, since they're pretty cute and small, but I feel as if amphibians are some of the coldest, least discerning modern predators that'll swallow almost anything that moves near their mouths. It's cute when it's my axolotl trying to swallow my relatively gigantic human fingers, but if it were a 20-foot-long river monster trying to swallow my entire human body... anyway, as a horror fan, once I gave temnospondyls the time of day, they easily became a new favourite.

But there are some beasts that never wound up winning me over, namely trilobites. Don't get me wrong, I'd still cry tears of joy if I saw one in real life, but they're not exactly in my top ten. Or top fifty.

It turns out that lots of extinct animals are surprisingly happy to be petted: here's the proof. Ronnie's responses to certain animals are not always as gushing as Miss Lernin's, but several species - and not always those you'd expect - score very high cute points. I expect Mesozoic crocodyliforms to be every kid's favourite fossil animals after reading these books. Excerpt from Ocean Renegades, © Abby Howard.

You have a background in comics and writing, as well as a huge passion for horror films - where does prehistory fit into this? How often have extinct animals featured in your projects, illustrated or otherwise?

I think these things feed into each other more than one would expect, especially when it comes to worldbuilding and creature design. Knowing how the world came to be is, in my opinion, the best way to know how to build a new one, and that goes for building creatures and monsters, as well. Even if you're creating something humanoid! I'm constantly using my database of weird critters that exist or have existed to make my designs more interesting. Grounding your design in reality, while it may seem counter-intuitive when trying to create something otherworldly, has proven to be really effective for me.

Well, that and looking up gross corpses. Those are my two types of monsters: critters and corpses.
As for examples of how prehistory has bled into my other work, I'm currently working on a book of short horror comics set to be published next year, and one of the stories features a nessie-esque lake monster that's a mashup of an alligator, a marine iguana, and of course, a plesiosaur. The recent research on the body shape of plesiosaurs has, I think, finally made them look more like believable living creatures, and I leaned heavily on their new meaty shape for the silhouette of the monster in the story.

A busy scene from Ocean Renegades. Despite Abby's horror leanings, this is about as 'monsterised' as the Earth Before Us restorations get, which is terrific. We get the sense that these animals are dangerous carnivores, but not that they are ravenous killing machines. © Abby Howard.

Child-orientated palaeo education often seems less concerned with learning and knowledge than simply using dinosaurs as kid-friendly entertainment. The Earth Before Us series, in contrast, is smart and educational while also being entertaining and approachable. Indeed, the content and clarity of your books makes them great for anyone to read, not just kids. Can you tell us what inspired you to write them, and how you see them in the context of other child-focused palaeo outreach?

Honestly, this may be a little petty, but I was unsatisfied with a lot of the dinosaur books I was seeing. Even beyond the books that are outright inaccurate, I hadn't seen any that went far enough in their explanations to satisfy what I thought could be done with the genre. I wanted something that showed these creatures in their natural habitat, surrounded by diverse animal life and at least one human for scale. That last part was important to me-- I felt it would contextualize the size of ancient beasts in a way that simply throwing out lengths and weights can never do. You can tell me the height of a T. rex til the cows come home, but unless I see a human standing next to it, it won't stick with me. Though I'd be lying if I said I didn't also love drawing myself next to all my favourite extinct creatures.

I had also seen a lot of books that tackled the "what if the information in the book is obsolete in the next few years" issue by simply not embracing any current research at all, and just giving nods to the by now widely-accepted fact that certain dinosaurs had feathers (while still drawing them as skeletal monsters with huge teeth and claws and maybe a couple feathers sticking out of their heads). That was so frustrating, especially since it could be turned into a useful teaching moment about scientific theories and perhaps lead to fewer adults becoming horrifically incensed when palaeontologists dare add anything to dinosaur models. So I wanted to make a book that was as up-to-date as I could, and didn't worry about whether it'd all be obsolete in a few years. And it sort of is-- my T. rex is far too fluffy! The naked skin samples were found the year after the first book was published. But I don't beat myself up about it, because it's better to take risks than to perpetuate ever-more-outdated perceptions.

A double-page spread of the glorious late Eocene from Mammal Takeover. The unobtrusive labelling adds a layer of additional information to every page, and gives the opportunity to learn about species not being directly discussed by the main characters. © Abby Howard.

I'm curious how you approached the Palaeozoic-focused Ocean Renegades and Cenozoic-focused Mammal Takeover, given that they lack audience-pleasing (and thus bookselling) non-avian dinosaurs. How did the general lack of A-list fossil species in the Palaeozoic and Cenozoic affect the creation of these books? Were you ever tempted to tell your story in one volume to get around this issue, or did you always envisage a comic trilogy?

I was surprised at how easy they were to sell to the publisher, and I'm so glad they decided to take a chance with the series. I'd originally planned to do one book (just about the Mesozoic), but they offered me three so I felt it would be a good idea to go ahead and cover everything that's ever lived, if I could. And since the first book was pitched as a deep dive into the Mesozoic, specifically focusing on creatures that don't usually get the spotlight, writing follow-up books about even more obscure creatures was an easy sell! I feel incredibly fortunate to have had very understanding editors who didn't push back when I wanted two-page spreads about early annelids and echinoderms, bless their hearts.

I also think in some ways the fact that I highlighted so many different animals was itself marketable. Kids love illustrations with a lot going on and lists of facts, and my books definitely have those things. I wrote these books for the encyclopedia-reading kid I used to be, and as it turns out, there are a lot of kids who are looking for books like these.

Your depictions of fossil animals are very modern: there is fluff and fuzz on your dinosaurs, most animals are lipped, and all they sport generous amounts of soft-tissue. At the same time, the reconstructions are necessarily stylised to some extent, to fit the comic world you've created. Can you take us through how you created your fossil animals? Where did you find the compromise between your own style and following fossil data?

The compromise was mostly made for me based on the limitations of my own style! The way the creatures are drawn was often was as good as I could get them with my current skillset and the looming deadlines. I would start with the best material I could find for the particular critter-- for this, I thank both you and Scott Hartman (of skeletal drawing) for the paleoart resources you provide. I also thank all the people who take pictures of fossils in museums that are too far away for me to visit and put them online, though I wish more of them would include a photo of a plaque saying what animal it actually is. And like any paleo-artist, from there I used slightly similar modern animals for soft tissue anatomy reference, which helps the drawing look more like something that could be alive. From there, the stylization was up to how well I could translate the reference material into shapes that didn't look awful, haha.

I think the hardest part was fitting so many animals on each page. That wound up setting limitations as well, since I had to make sure the animals weren't blocking each other too much but were also interacting in an engaging way.

The plump plesiosaurians of Dinosaur Empire! These animals are not stylised to look this way: there is good fossil evidence that Mesozoic marine reptiles were covered in thick, fatty tissues, just like living secondarily aquatic tetrapods. It's good to see these discoveries being reflected in modern books. © Abby Howard.

The lack of fighting and violence in these books is a breath of fresh air. Even Tyrannosaurus, which by unspoken Laws of Palaeo Media should be shouting and stomping its way around the Late Cretaceous, is depicted more like a lazy cat. While the images and text don't downplay the fact that many extinct animals were probably dangerous, and we see several predatory acts, you demonstrate prehistory with nuance: fossil animals can also be cute, majestic, nurturing and amusing, as well as aggressive. Was this a deliberate response to all the aggressive behaviours featured in palaeo-themed books aimed at children?

Absolutely! I feel like the emphasis on violence in paleoart is super boring, especially in the way it makes people feel like ancient beasts are movie monsters rather than actual animals, and that if they aren't scary they're dumb and lame. I'm a big proponent for paleo media that depicts ancient beasts as normal animals with a normal level of aggression, and can't help but roll my eyes when a narrative focuses on The Hunt or culminates in a big fight between toothy, scaly monsters.

Though I do like when nontraditional predatory behaviour is depicted-- when I was young I saw a documentary that featured spinosaurus hunting for fish and LOVED it because it wasn't just some big monster fight. It felt so much more like an animal just trying to live. This goes for scavenging, as well. I always found the "debate" about whether large predators like T. rex were active hunters or scavengers to be so pointless. As if any self-respecting predator would pass up a perfectly good rotting carcass. That's a free meal!

But my personal favourite media is always the stuff that emphasizes the quiet moments-- a creature wandering through a rainy forest with the bellows of a far-off beast in the background, napping in the shade on a hot day, chasing bugs, taking care of its babies. I go nuts for that stuff. My kingdom for a documentary with no narration that follows a dinosaur through its daily life.

The Dinosaur Empire! take on Tyrannosaurus. This mighty beast is roused from its slumber having sensed human prey, rises to its feet, opens its mouth and... yawns. Note the crushed ferns where it's been lying down: this Tyrannosaurus evidently enjoys a good snooze. © Abby Howard.

I want to talk to you about the protagonists of Earth Before Us, Ronnie and Miss Lernin. Palaeo media still largely depicts palaeontologists as rugged, Indiana Jones-esque men, and young dinosaur fans tend to be boys. You've turned this on its head by featuring a young black girl and a female palaeontologist who - holy cow - doesn't even wear field gear! How do you see Ronnie and Miss Lernin in context of wider conversations about stereotyping scientists, and the growing call for more diverse voices in science and education?

I'm very glad I was able to contribute my little piece to help change the public perception of who is interested in and pursues this sort of work. I want kids to take for granted that yes, of course women and people of colour can be palaeontologists. I want it to be a given, and I hope seeing characters like mine can help.

I was fortunate enough to be part of a natural history program that was led by both men and women, and the undergrads I took classes with were majority women. However, it's still the case that many femme folks don't feel comfortable pursuing higher degrees in their field after graduating. I'm sure a large part of this is the competition in these fields-- most people in general won't pursue a higher degree. But there's definitely a discomfort when you're applying for positions and the people you'd be working with clearly think less of you and think you aren't as capable. A friend of mine applied for field research positions after she graduated, and one of the interviewers wound up telling her that she wouldn't be able to "spend a lot of time in the mornings doing her hair and makeup". As if her merely being a woman meant she did those things, took a lot of time each day even while camping in the desert to do those things, and that it would be a great detriment to her career to want to do those things. The fact that this was something the interviewer felt needed to be brought up just because she was a woman speaks volumes about how he perceives women, and how he clearly doesn't think they could be prepared for field work, despite the fact that my friend had field experience. I know I wouldn't want to work with that person. And if every person you encounter is like that, of course you might decide not to pursue that career.

I will say, however, that I left the program not because I felt uncomfortable being a girl in STEM, but because I was a terrible student, haha. I make a much better cartoonist.

Mammal Takeover devotes several pages to discussing human-led environmental crises, a circumstance paralleling a book I've just finished on the history of life. To me, humanity's major and lasting environmental impacts feel like an essential part of the story of life on Earth, and omitting them feels somehow complicit and accepting of our deepening environmental crisis. Did you have similar thoughts working on Earth Before Us? And how do you sell issues like conservation, the politics of climate change etc. to young audiences?


Those were very difficult and depressing pages to work on, but definitely necessary. Not only because it's a subject that needs to be discussed at every opportunity, but because it's a huge part of the world we're living in today. I couldn't just leave it at "and then all the modern animals evolved and we all lived happily ever after" when the presence of humans is causing the sixth mass extinction.

One of the gutsiest parts of the series is the closing segment of Mammal Takeover, where Ronnie asks Miss Lernin about the sixth great mass extinction and the role humans are playing in it. As demonstrated by this page, the tone struck here is frank, but also hopeful and empowering. © Abby Howard.

Writing about climate change for kids was no small task, and I hope I did a better job than the media I grew up with. I've always had a disdain for the way climate change is discussed with kids-- there always seems to be an emphasis put on personal accountability, which for me mostly led to anxiety and hopelessness. I would stress about leaving the water running or driving places instead of walking, meanwhile corporations I have zero control over are out there tearing down forests and ripping holes in the ozone layer. I didn't really want to put in any of those "here's how you can help" tips to avoid doing that same thing to the next generation, but when the time came to write that section, I didn't want to just say "oh yeah, rich people are just wrecking the earth and there isn't really anything you can do except beg your parents to vote for people who say they'll do something about it, which is also not a guarantee that something will be done about it". So I did wind up putting in some little tips, because otherwise it would have been a pretty dismal chapter. Plus, I do think there's no harm in doing these seemingly small things to help out in whatever way you can. You don't have to be perfect, but as I said in the book, if those folks are gonna keep ruining the environment no matter what you do, you might as well go ahead and plant that tree or get those LED lightbulbs or go vegan. Because if so many people wind up doing these things that being a little environmentally-conscious becomes the norm, that's still a net positive!

Do you have any future plans for the Earth Before Us series? I can see this readily lending itself to museum exhibitions, TV shows and toys. Will we at least get more books with these characters? "Miss Lernin and Ronnie...IN SPAAACE"?

Alas, these are the only three books I had planned! I don't know anything about any other subjects. Especially space, which I don't think I'd ever be able to make anything but horror comics about. Space is scary! No one should be up in it!

A TV show would be an interesting idea, though, and extremely fun to write. I may have to keep that in mind...

Finally, where are the best places to keep up with your work online, and how can we support you creating more art, comics and books?

The best place is probably my twitter, where I'm most active: @abbyhoward. I also have a website where I post links to my webcomics and various books: https://abbyhowardart.myportfolio.com/. You can support me on Patreon to help me keep making comics forever: https://www.patreon.com/abbyhoward. And I also have an online store! https://topatoco.com/collections/abby-howard

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Thanks to Abby for giving her time to answer my questions, I hope you found her insights into this awesome series as enjoyable to read as I did. There's still time to grab Dinosaur Empire!, Ocean Renegades! and Mammal Takeover! as Christmas gifts: steer your browsers towards those links (or the book store of your choice) and grab them before it's too late!

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Book review: Luis V. Rey's Extreme Dinosaurs Part 2: The Projects

Cover art for Luis Rey's 2019 book Extreme Dinosaurs Part 2: The Projects, featuring the latest incarnation of Luis' Deinonychus. Notice the presence of lips. Image borrowed from the Luis V. Rey Updates Blog. 

Unbelievably, the sun is already setting on 2019 and the holiday season is fast approaching. In keeping with the season, over the next two posts, I want to draw attention to two palaeoart-heavy products that I think are worthy of a place under your Christmas tree. 

First up is a book by renowned Spanish-Mexican palaeoartist Luis V. Rey: Extreme Dinosaurs Part 2: The Projects. I bought Luis’ book earlier this year at TetZooCon and felt it worthy of writing up, not the least because, as a self-published volume, any and all advertising and promotion is helpful. Extreme Dinosaurs 2 is available in both hardback and paperback editions (my review is based on the paperback) from Amazon and eBay for £25 and £20, respectively, which I think is a very fair price for these well-produced, high-quality books. These are not print-on-demand self-published books that roll the dice with aspects like printing and trimming: they’re pre-printed and Luis-approved products that you’re buying directly from the Rey household. 

Cover of the first Extreme Dinosaurs, borrowed from Amazon.com, featuring the earliest version of Luis' Deinonychus. Such extensive feathering was pretty radical for Deinonychus in 2000, and there's an even more 'extreme' version inside.  

Extreme Dinosaurs 2 is billed as a sequel to Luis’ 2000 book Extreme Dinosaurs, though they are quite different in format and organisation. Extreme Dinosaurs is a fairly conventional popular dinosaur book at heart, overviewing dinosaurs from around the world in several themed sections. Fulfilling the promise of ‘extreme’ dinosaurs is Luis’ compositionally and anatomically radical dinosaur art which, in a palaeoart era dominated by Sibbicks, Pauls and Halletts, was unlike anything seen before. Luis’ enthusiasm for the then newly discovered Chinese feathered dinosaur fossils gave his work an additional revolutionary edge. Today, Extreme Dinosaurs is available only through second-hand markets but it is worth tracking down for the classic Luis Rey art it contains, as well as to own a time capsule from a major transitional period in dinosaur palaeoart.

Extreme Dinosaurs 2, in contrast, has a slightly narrower focus. It documents four major palaeoart projects and exhibitions executed by Luis in the last decade and feels like a more specialised volume as a result. While the opening section of the book, devoted to the evolution of feathers and skin, serves as a general overview of dinosaur palaeobiology and appearance (featuring art from Luis’ Dinosaur rEvolution exhibition), the rest of the book is more eclectic, with sections on Archaeopteryx and maniraptorans (from the exhibition: Feathers Fly; The Art of Archaeopteryx), dinosaur parenting behaviour (Hatching The Past), and Mexican dinosaurs (Dinosaurios Hechos En Mexico). It holds together as a book and contains many 'firsts' as goes restorations of newly discovered Mexican taxa but, as a collection of personal projects, it doesn’t work as well as the first as an introduction to contemporary dinosaur palaeontology. This isn't a problem of course, but it's worth noting - if thinking about this as a gift, say - that readers who aren't already fairly nerdy about dinosaur palaeontology might struggle with some of the content. As with Extreme Dinosaurs, I suspect its main appeal will be the vast quantity of Rey artworks it contains. At over 130 pages it’s more than twice the size of its forebear, and the number of illustrations is extraordinarily high. It really is a bonanza of Reyian dinosaurs, where animals lurch at you or at each other with every page turn. Luis’ artistic flourishes make this a tour through the Mesozoic like no other - a Reyozoic, if you will - and if you’re a Luis fan, it’s a must-have for this reason alone. 

A lot of Rey artwork features predation, but it's not all animals leaping from the page towards your face. Here, the giant Mexican hadrosaur Magnapaulia is pursued by albertosaurines. I particularly like the purple and yellow hues in this scene, and the size of the Magnapaulia is conveyed well. The inclusion of many obscure, rarely illustrated Mexican species is definitely a plus point for Extreme Dinosaurs 2. Image from Luis' blog, © Luis V. Rey.

This is not just an art book, however. To the contrary, there's a surprising amount of text and it's clear that Luis did not want this to just be a book of pretty pictures. Rather, we obtain a detailed insight into the science behind his artwork, as well as the themes his images are constructed around. Luis' passion for pushing dinosaur restorations is obvious, and I found his text both enjoyable and interesting to read. This is not only because of the insight it gives into the creation of his distinctive art, but also because Luis played a major role in shaping the modern look of dinosaurs, and experienced a lot of pushback from the 'birds are not dinosaurs' crowd and folks who felt his artwork was too outrageous. This gives his commentary a depth, historic perspective and unique voice unavailable to younger palaeoartists. Moreover, while Luis has a genuine reason to feel vindicated by some of his 'extreme' takes on dinosaurs being confirmed by fossil data, there's not a whiff of aggression, arrogance or ego to his commentary. He is open about the difficulties of restoring certain animals and admits that new discoveries will require him to revise and update his work in future, as he has already done for many images in this book. I feel this is a sensible attitude to have in the palaeoart game.

One of the aspects I admire most about Luis' artwork is his consideration of integument. Although guided by phylogenetic bracketing, he plays with skin variation within clades and across individual animals, creating unique - but not implausible - takes on species such as Deinonychus and Nothronychus. From Luis' blog, © Luis V. Rey.

Of course, most people will be buying Extreme Dinosaurs 2 for the art. To paraphrase Alan Partridge, Luis' style has evolved since the first book, but not revolved: his use of media has changed, his hues are slightly more grounded, but his images are still classically Reyian with fantastic colours and dynamic compositions. I think that time has been kind to Luis' portfolio, thanks to palaeoart culture normalising towards ideas he was applying years ago. I recall first encountering Luis’ artwork in the early 2000s and, having mostly grown up on a palaeoart diet of John Sibbick, it would have been easy to dismiss his renditions as a madman’s view of prehistory. Indeed, if it weren’t for the fact that I first saw his work at the University of Portsmouth - and thus in a wholly scientific and educational context - I might have done so. But though unusual, Luis' work was always produced within the confines of available data. His reconstructions were different because he was pushing ideas and information further, as well as exploring the uncertainties and unknowables of fossil animal form. This philosophy was far ahead of its time in the 1990s and early 2000s and, juxtaposed with his unusual animal arrangements, behaviours and compositions, we have to view Luis as an early practitioner of what we’d eventually label the All Yesterdays movement. While time has altered what we consider anatomically ‘extreme’ in palaeoart (many reconstructions in the first Extreme Dinosaurs would be considered par for the course today), this reflects our changing attitudes and fossil data shifting the bar in Luis' direction. 

Luis remains entirely unafraid of creating extreme takes on fossil animal behaviour and form, and that takes... whatever this Allosaurus used to have where those spikes are now. This image is based on a real Allosaurus specimen with a pathological pubic boot, as outlined at Luis' blog. Image © Luis V. Rey.

While it’s difficult for Extreme Dinosaurs 2 to recreate the anatomical wow factor of the original book, the boldness of Luis’ work remains as strong as ever. Luis’ palaeoart has a reputation for polarising opinion but, whether you’re a fan or not, it’s hard to argue that his art is not thought-provoking, ambitious, and an important reminder to never get too comfortable with convention. Indeed, there’s a fearless quality to Luis’ work. It confidently challenges expectation about what ancient animals looked like, while never advertently straying from the confines of fossil data. Look beyond the saturated colours and elaborately fuzzy animals and you'll notice that Luis is often highly attentive to details of specimens and palaeoecological scenarios, creating whole scenes around pathological specimens and overhauling older works to bring them up to date with modern science. Several such examples are seen in Extreme Dinosaurs 2, such as new art showing Triceratops being decapitated by Tyrannosaurus (as suggested by fossil data) and older paintings being updated to better match current interpretations of feather distribution or soft-tissue arrangements. The addition of lips to most of the dinosaurs in Extreme Dinosaurs 2 feels like a major departure from older Luis works, the lipless jaws of his foreshortened animals being, in retrospect, an obvious characteristic of many of his paintings.

I like the fact that Luis works within, but is not a slave to, phylogenetic bracketing, and his work implies that the appearance of fossil species may have varied significantly within clades. His large dromaeosaurs, for example, aren’t just larger versions of the ‘ground eagles’ indicated by small-bodied fossil specimens, but instead have ostrich-like naked legs and shaggy, messy feathers which could reflect flightless habits. He is unafraid of applying large tufts, long fibres and fleshy skin to his restorations in ways which can seem odd, but only because Bornean bearded pigs, porcupines and turkeys are not our go-to reference taxa for most dinosaurs. Luis’ lack of concern for making animals look peculiar or downright daft is a rare asset, and one of the things I admire most about his palaeoart.  

Many aspects of Luis' work - from his posing to his muscular, athletic animals - remind me of Bob Bakker's palaeoart - it's unsurprising that Rey-Bakker collaborations have been plentiful over the years. Here, Tarbosaurus runs down Gallimimus. Image from Luis' blog, © Luis V. Rey.

Luis lists Bakker and Paul among his greatest palaeoartistic influences in Extreme Dinosaurs 2, but I feel the Paulian link is largely philosophical: the demand that our reconstructions adhere to fossil data. Artistically, Luis’ art is more Bakkerian, recalling the energetic, contorted posing and tight framing of Bakker’s work from the 70s and 80s (e.g. images in The Dinosaur Heresies (1984), and Dinosaurs Past and Present (1987)). Bakker's palaeoart is, in itself, very striking, but Luis takes these compositions even further, adding amazing colours, clashing textures and extremes of perspective to Bakker’s foundation. The result is among the most audacious portfolio of palaeoart ever produced, and it makes mechanisms sometimes employed to make palaeoart seem shocking or arresting - such as extremes of gore or melodrama - seem clichéd, tame and pedestrian. Although other illustrators have copied Luis' once signature style of hyper-foreshortened dinosaurs, these imitators lack the flair and boldness of true Reyian foreshortening. Any artist can give you a faceful of gaping theropod, but only Luis will combine this with inflated air sacs, saturated colour schemes and some sort of crazy-complex integument. Luis fans will be happy to know that Extreme Dinosaurs 2 delivers plenty of what you're expecting from a Rey portfolio, despite the use of photo manipulation (see below) adding real-world textures and colours to his arrangements.

Extreme Dinosaurs 2 showcases Luis’ work from the last decade or so, which means it more or less exclusively features digital photo composites over traditional paintings. Many of the featured artworks are murals, and we are treated to glimpses of early sketches showing how these came together. Luis’ use of photo composition has not been universally welcomed, with some preferring his older work executed in traditional media. This might be a deciding factor for some potential customers of this book but… read on a little further before you make up your mind. I’m going to be honest and confess that I’ve not always been a fan of Luis’ digital works, but that Extreme Dinosaurs 2 has given me cause to change that view. For one, the images simply look better in this well-produced book than they do as low-res online versions, being both appreciably sharper and more detailed. I don't think they're always successful but, hey, show me anyone who can flawlessly execute 130 pages of photo-real images. In many cases, the lighting and texturing of the animals is genuinely very good, giving a great sense of three dimensions to a medium which often looks flat.

Double page spread from Extreme Dinosaurs Part 2, showing a mural with battling Tarbosaurus and Talarurus. The arrangement of this photo composite is classic Luis Rey, despite the challenges of this medium. Image borrowed from Luis' blog, © Luis V. Rey.

Secondly, in terms of ambition, Luis’ photo composites are leading the field. It’s not terribly difficult to photoshop a lizard snout onto a bird head to make a dromaeosaur, but that just wouldn’t be a Luis Rey artwork. He continues to make thoroughly distorting and extreme Reyian creations with a medium that typically inspires artistic conservatism. Extreme Dinosaurs 2 features snorting Deinocheirus with bright red inflating facial sacs, a towering Tarbosaurus kicking out of the canvas, and maniraptorans flinging themselves, ninja-style, through the air. While some artists are grounded by photo manipulation, Luis is creating some of his most adventurous and startling compositions in the same medium.

Third, after immersing myself in page after page of modern Reyian colours and composition, I started to suspect that Luis is not, as is mostly the case with photo-composited palaeoart, going for strict photo-realism. Luis has, after all, a background in surrealist and abstract art, and you can see the influence of these genres even in his traditional work. There is something pseudo-surreal and semi-abstract about some of Luis’ busy, highly active scenes of arching bodies, extremes of body size and perspective, and colliding colours and texture. Combining landscape photographs, original paintings, bits of toys and models, cropped and recoloured animal skin, cloned elements and texturing effects into classic Reyian scenarios is a terrifically bonkers way to reconstruct extinct creatures, and seems almost reflective of how we mentally conceptualise these animals from different references: a little of this living animal, some of that painting, a pose from that museum mount... and so on. This collaging effect sometimes avoids looking real, but Luis' images never fail to look alive. I have a lot of respect for Luis for pushing photo composition in his own way and think some of the results are genuinely striking. The images can still read as straight reconstructions of extinct subjects (and I think this is how most people are appreciating and judging them), but there’s an artistic quality to them which we should also admire, especially as the palaeoart community calls for more interesting styles and experimentation among its practitioners.

Scenes such as this Therizinosaurus rookery/life cycle image are so packed with action, colours, textures and characters that, for me, they transcend conventional natural history art and dip their toes into a surreal, larger than life version of prehistory. Luis has made a name for himself creating scenes like these, and his distinctive style is, I think, a terrific addition to the more conventional palaeoart that folks like myself produce. Image from Luis' blog, © Luis V. Rey.

While I generally have good things to say about Extreme Dinosaurs 2, it's only right that, in interests of providing a fair review, I mention a few things I'm less keen on. Most of these are editing and formatting errors that do little harm to the book, but were sometimes jarring to encounter. There are a few passages that would have benefitted from tighter copyediting (both for typos and phrasing), and fonts can also sometimes change from page to page, or even line to line, in a manner I'm pretty sure was unintentional. More significantly, a small number double-page spreads include important images (either whole illustrations or parts thereof) in the seam, making them all but unseeable unless you're the sort of monster who snaps the spines of their books. These issues are more tantamount to an occasional lack of polish than book-crippling problems, but picky readers might find them distracting or frustrating.

But... whatever. Extreme Dinosaurs Part 2: The Projects is an enjoyable book and a firm reminder of Luis' importance to palaeoart. It works as a fun and interesting read or simply as a vessel to own Luis' most recent illustrations, and the production quality and amount of content represent excellent value for money. In being almost 140 pages of entirely unfiltered, undistilled Reyian palaeoart this is definitely a book for Luis fans and palaeoart collectors, although there's no compromising here to convert anyone with a strong dislike of Luis' style. But, as one of palaeoart's most iconoclastic practitioners, I'm pretty sure Luis wouldn't have it any other way.

(One final word on Extreme Dinosaurs 2: if you've already got a copy, and have enjoyed it, please help Luis out by spreading the word on social media or leaving a review at the web store you used to buy it. I know from experience that word of mouth is critical to the success of self-published books and, if we want to see Extreme Dinosaurs Part 3: This Time It's Extremely Personal, we need to help this book reach its audience.)

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Megafuzz under the microscope: how credible are restorations of giant fluffy extinct animals?

Images of giant prehistoric animals covered in thick, fluffy coats are par for the course in modern palaeoart, including lots of my own (image above shows Therizinosaurus, from 2015). But... hey: just how warm are these multi-tonne animals under all that fuzz?

Rendering giant prehistoric animals with extensive hairy coats or thick feathery coverings is a convention now so well established within palaeoart that few of us give it a second thought. While this practise is well-grounded in fact for some cold-adapted Pleistocene megamammals, such as woolly mammoths and woolly rhinoceros, our treatment of other giant species - giant sloths and giant coelurosaurs - has a greater basis in tradition and expectation than fossil data. We have, after all, mostly lacked detailed insights into the skin of these giant extinct animals, and have thus relied on scraps of soft-tissues and phylogenetic bracketing to inform our art.

My artistic history firmly places me on the megafuzz bandwagon. Earlier this year I painted a shaggy Megatherium and since 2013 I've painted woolly Pachyrhinosaurus, several extensively feathered tyrannosaurs and a Therizinosaurus with more feather coverage than most modern birds (above). But I was recently given pause to question these reconstructions when Dennis Hansen, one of my excellent patrons, asked about the possibility that giant sloths, such as Megatherium, were largely or wholly devoid of hair because of issues with thermal energetics. At that size, wouldn't giant sloths be far too warm? This idea has been promoted by some sloth researchers (Fariña 2002, Fariña et al. 2013) but it's rare to see it expressed in palaeoart. Megasloths are, near-universally, restored with the same shaggy fuzz first given to them by Benjamin Waterhouse Hawkins in 1854 and it now seems shocking and wrong to see one without that characteristic pelt. Should you want to draw one, you have to fight your hand - Evil Dead II style - to force those strange, hairless contours onto the canvas.

When pondering this query I came to realise how little I really know about thermoregulation in large animals in general. By this, I don't mean the generalities of surface area:volume relationships, or different mechanisms of homeothermy: I'm talking about the preferred temperature ranges and ideal climatic conditions of large living endotherms. At what temperatures do species of a given size and shape start to feel hot or cold? How does that vary across clades, body shapes, and sizes? How sensitive are they to changes in ambient temperature? What difference does a coat of fur or feathers make to the thermal tolerance of a giant animal? This seems like a major hole in my knowledge as a palaeoartist, and I don't think I'm alone in not having a firm grounding in this topic. I gather from online conversations that most of us are shooting from the hip when putting fur, fluff and fat onto our reconstructions, applying what seems 'right' given the phylogenetic position and palaeoenvironment of our subject species, but without specific reference to models of thermal energetics, the temperature tolerances of analogous animals, or any other form of quantified data.

Tyrannosaurus rex: megafuzz edition, from 2016. This was pre-Bell et al. (2017), obviously. They were different times.

So, for the last few weeks, I've been dipping into technical papers on this subject whenever I've had a spare few moments. I've found this a very useful exercise and encourage other palaeoartists to do the same. There's heaps of literature on the thermal energetics of endotherms and many enlightening, sometimes surprising results to ponder. While this exercise does not address the many unknowns of extinct animal physiology that are essential to understanding their strategies for thermoregulation or heat dissipation (e.g. metabolic rate, activity level, conductivity of skin etc.) it makes for an excellent palaeoart 'calibrating activity' or reality check. After all, if we don't know, in a measured and quantified sense, how size influences the thermal tolerances and integument of living animals, how can we be expected to make credible reconstructions of their fossil relatives?

Into the Thermal Neutral Zone

There are several different concepts we can use to investigate thermal energetics. One of the most enlightening and useful mechanisms is thermal neutrality. Endothermic organisms are thermally neutral when their environment is warm enough that their Basal Metabolic Rate (BMR) is sufficient to maintain their core temperature without additional energetic investment or water loss. This can be given as a single value, which represents the thermal neutral temperature for a specific configuration (e.g. a certain pose and hair or feather arrangement etc.) or it might be given as a range - a Thermal Neutral Zone (TNZ). We define the TNZ as the temperatures at which very minor adjustments to an animal's posture or integument control core temperature rather than changes to BME. While the TNZ does not exactly equate to an animal's thermal 'comfort zone' (Kingma et al. 2014) this is also not the worst layman's summary of the term: if an animal has to invest more than minimal energy to maintain a steady core temperature (e.g. exposing a heat-radiating body part, or altering insulation depth by raising/lowering hair or feathers), it's outside the TNZ.

Principles of the Thermal Neutral Zone. This graph is based on an excellent diagram included in this lecture, but I've been unable to find the original source.

The TNZ is bounded by two thresholds, Lower and Upper Critical Temperatures (LCT and UCT, respectively - see diagram, above). These are the ambient temperatures at which an animal has to take action (e.g. invest energy above BMR) to keep itself at a desired core temperature. Below the LCT, animals use energy to keep warm (e.g. by shivering or exercising), while exceeding UCT instigates cooling responses, such as seeking water, sweating or panting. Some species are well adapted for survival outside of their TNZ, or are capable of tolerating huge temperature fluctuations without changes to BME. Others are specialised to live in a narrow ambient temperature band and react inefficiently when subjected to cooler or warmer conditions.

What's neat about the principle of thermal neutrality is that it allows us to explore the effects of body size, metabolism, insulation and temperature in a quantified manner. Thermal neutrality is applied widely to all manner of biological studies: just a few applications include animal husbandry, understanding animal responses to climate change, and the evolution of organismal physiology. For our purposes, it's helpful that well-established scaling trends have been recognised from studies of endotherm thermal neutrality. They're based on pretty fundamental physical factors such as animal mass, ambient temperatures, animal core temperature, and skin conductivity, so we can be pretty confident that they should apply to fossil endotherms too.

Generally speaking, the smaller the animal, the closer their thermal neutral temperature is to core temperature. Small animals have narrow TNZs, higher LCTs, and - owing to their lessened thermal inertia - sharper increases in metabolic rate when ambient temperature takes them away from thermoneutrality. These facts describe the well-known phenomena of small animals generally being more concerned with staying warm than keeping cool. The inverse is true for large animals, which have broader TNZs, lower LCTs, and lower metabolic costs to warm themselves below LCT: in other words, they're less sensitive to cool temperatures.

Whatever size an animal is, excessive heat is more dangerous than excessive cold. Endotherms can tolerate ambient temperatures much lower than their LCT before reaching dangerous levels, but their tolerance to temperatures above UCT is much lower: just a fraction of their potential LTC response range. While a cold animal can generate a lot of additional heat from exercise and increased metabolic rates, hot animals have to rely on raw physical processes - conduction, radiation, evaporation and convection - to cool down. We can only enhance these processes so much and, as most endotherms run within 3-6°C of critically high core temperatures, we have a low margin for error when exposed to very high temperatures. An organism's thermal neutrality is not fixed, and can be altered by anything which affects heat production and loss (e.g. wetting the skin, humidity, air movement), so we have to consider a range of environmental factors, not just temperature, when discussing this concept.

My very conventional take on Megatherium, a four-tonne sloth restored almost exclusively as extensively hairy since the mid-1800s. I feel safe and cozy with this image, and the idea of hairless megasloths is downright weird to me. Good job I've not tried to draw one or anything.

Values of thermal neutrality have been reported for numerous animals, including humans. A lot these stem from research into livestock welfare, wherein farmers and breeders need to know what temperatures their animals are comfortable in (for an extensive summary, see the 1981 findings of the National Research Council). Thus, the TNZs of horses, cows, sheep, chickens and so on are well documented and easy to find outside of technical literature. A complication to these figures is that they often lack details such as animal weight, breed, and environmental specifics, so they are - at best - a rough introduction to livestock TNZs. Nevertheless, these are useful species to discuss because they're so familiar to us, and I've attempted to summarise representative values from several sources here.

Unsurprisingly, smaller animals like chickens (c. 2 kg) feel the cold relatively easily and have a relatively high and narrow TNZ of c. 18-23°C. A freshly hatched chick has an LCT of 34°C. Larger birds, like emus (on average, 30 -40 kg), have a lower LCT of 10°C (Maloney 2008). Dairy cattle (450-800 kg) are less sensitive to temperature changes, with a TNZ of 5-25°C, though some dairy cows are reported as having LCTs of -15°C. This range seems to apply to certain beef cattle breeds as well, though not all: some (presumably smaller and leaner?) have LCTs of c. 10°C. Horses have a TNZ of 5–25°C (Morgan 1998), although they can reportedly tolerate freezing temperatures comfortably with unshorn hair. Cattle with full, dry winter coats can also tolerate freezing temperatures, down to -7°C. Animal condition and food intake are important variables: well-fed animals with access to food have lower LCTs than those that are fasting. For cattle, the difference between fasting and full-feed equates to a 19°C difference in LCT, from -1°C in full-feed to 18°C in fasting (National Research Council, 1981).

Naked humans are thermally neutral around 27°C, making us - perhaps counterintuitively - most comparable to the smaller species mentioned above. This relatively high temperature reflects both our long-term hominid reliance on clothing as well as our ancestral climate. Habitat and climates influence the temperature tolerances of endothermic animals in terms of both short-term acclimatisation and longer-term adaptation (Scholander et al. 1950; Scholander 1955). Arctic animals have amazingly broad TNZs of many tens of degrees. Resting arctic foxes, for example, show little change in BME whether they are in 30°C or below -30°C. They achieve this by mixing high-performing insulation around their bodies with thinner insulation on their extremities so that, by simply changing posture, they create an 11-fold difference in heat retention or loss. Tropical animals - which includes human ancestors - have relatively narrow zones of thermal neutrality and begin to feel cold when exposed to temperatures of even 25°C. They also respond more energetically to changes in temperature, raising their metabolic rates far quicker, relative to temperature change, than their polar equivalents. The bodies of tropical species can be seen as specialised for continuous high temperatures, while those of colder climates are adapted to deal with extreme fluctuations in daily conditions.

The impact of integument and body shape on TNZ

Data are also available regarding the impact of insulating tissues - fur, fat, feathers etc. - on animal heat loss. One very familiar source on this topic are sheep in their fleeced and shorn state. The National Research Council (1981) reports that a sheep with a 10 cm thick fleece has a LCT of -120°C(!), but this lowers to -15°C when the fleece is trimmed to 7 mm. That's a remarkable change in temperature tolerance, and shows the enormous impact that integument thickness has on animal energetics. In a wet, windy setting, that LCT of our 7 mm fleece sheep raises even more, to 13°C.

We can also explore the scaling effects of adding insulation using digital models. Calculating TNZ at various animal sizes and body shapes, and both with and without a standardised insulation, shows that insulating layers have increasing impacts on TNZ at large size (Porter and Kearney 2009). The addition of insulation only lowers the LCT of very small animals (e.g. rodent, microbat or songbird sized) a few degrees, but LCT drops exponentially quicker in larger animals. Applying the same grade of insulation to a one tonne animal lowers LCT by about 65°C, from ~25°C in a naked-skinned animal to below -40°C in a fuzzy one. Again, I have to remark on how big that shift is: this is the sort of difference that could adapt a species to a whole new biome.

The impact of insulation, body shape and wind speed on LCT values in endotherms. Note how LCT generally falls with increased body size, but how the introduction of insulation compounds this effect dramatically. From Porter and Kearney (2009).

Porter and Kearney (2009) also show that changes in body shape - which could reflect either different anatomical bauplans or changes in posture - have an impact on LCT values too. Unsurprisingly, longer and thinner animals have higher LCTs than more compact animals, but the impact of increasing surface area becomes less pronounced at large size, and any impact they have is vastly overshadowed by the addition of insulation. This is an important point for those of us thinking that the body shapes of extinct animals might allow for fibres and fluff at larger sizes than we'd predict from living animals. Yes, body shape has an influence, but perhaps not as much as we intuitively expect, and with less and less impact as animals scale to gigantic proportions.

Thermal neutrality in giant animals

One frustration of current literature on thermal neutrality is a lack of specific data on our largest living species, such as rhinos and elephants. Though some literature discusses the TNZs of these species, I was unable to find their LCT and UCT values. Nevertheless, a wealth of studies have been performed into the thermoregulation of elephants that give hints about where their TNZ might lie. This research has been catalysed by both simple scientific curiosity as well as concern for zoo elephants in climates far removed from their naturally hot ranges in Asia and Africa. Elephants provide some of our best insights into the thermoregulatory challenges facing large extinct land animals, but these data come with important caveats. As discussed in my post on indricotheres, elephants have thermoregulatory issues beyond simply being huge: they are unusually compact, live in climates which are routinely warmer than their core temperature, and they cannot sweat or pant (Myhrvold et al. 2012). They still provide useful insights into the issues of maintaining a steady internal temperature at multi-tonne masses, but they are probably not biologically 'typical' giant animals.

Elephants are noted for tolerating a wide range of temperatures in their natural habitats, from sweltering daytime heat of over 40°C to overnight cools of freezing or sub-freezing temperatures. Their size and thermal inertia permits them to endure freezing nights without issue and, in discussions about the controversial subject of keeping zoo elephants in cooler climates, their handlers often suggest they are happy in snowy and icy conditions, at least for short periods, provided they can keep active. It seems one of the biggest problems elephants face in freezing temperatures is frostbite on their ears and trunks, not the cold itself. This probably indicates a very low LCT (close to or below freezing) for elephants, which is what we'd expect from the scaling trends outlined above. Estimates of thermal neutrality in multi-tonne fossil species (see below) point to similar values.

Desert elephants, such as these Namibian bush elephants, are specialised populations adapted to life in extreme heat and aridity. They have several anatomical adaptations to desert life - some specifically influencing their thermal energetics (smaller bodies, longer legs) - and avoid extensive exercise during the day, especially in warmer seasons, to avoid risk of hyperthermia. Their nomadic lifestyle is mostly achieved by long walks at night, not during the day. Image by Ron Knight, from Wikimedia, CC-BY-2.0.

Elephants may also spend a lot of time at or above their UCT, reflecting their struggles with heat dissipation. Monitoring elephant body temperatures during moderate exercise (walking) in a range of weather conditions (averaging 8 to 35°C) shows that their tissues accumulate heat 2.2 - 5.3 faster than it can be dissipated, depending on conditions (Rowe et al. 2013). This is in part because very large animals have a thick thermal boundary layer - a region of air adjacent to the skin which is warmed by heat radiating from their bodies. Larger animals effectively carry their own warm microclimate wherever they go, and face the challenge of trying to shed heat through it. This, combined with the heat produced by large-scale muscle activity, means exercise can be thermally stressful to elephants, especially in hot, windless conditions. Rowe et al. (2013) predict that four hours of continuous walking in very warm conditions would be fatal to an elephant, perhaps explaining why elephants living in their natural, warm habitats limit their daily exercise, routinely seek shade and water, and are often more active at night. Elephants spend much of their lives with internal temperatures close to the critical mammalian limit, even tolerating extended periods of near-lethal hyperthermia, to the extent that climate change may push wild elephants over the edge of their adaptive capacity to endure elevated temperatures. They are not entirely alone in this: other large mammals of very warm tropical settings - such as rhinoceros - also employ elephant-like behavioural adaptations when faced with high ambient temperatures. Rhinoceros have a more conventional mammalian capacity to deal with heat - they can pant and sweat - and yet they still seek shade and water during hot periods (Rowe et al. 2013). We have to view the thermal stresses faced by multi-tonne animals as defining physiological and behavioural factors in their lives, and as major selection pressures on their anatomy.

Thermal energetics in extinct giants

Having just learned a little about thermal neutrality in living species, can we make some broad predictions about the energetics of extinct giants? Many researchers have applied these principles to fossil animals and their findings are in line with the general points made above: there are strong indications that extinct giants - seemingly regardless of metabolic rate - had major issues with heat loss. It's quite reasonable to assume that this could have influenced aspects of their anatomy and appearance.

One such study is the article which catalysed this blog post: Richard Fariña's (2002) estimates of giant sloth thermoneutrality, with a strong focus on Megatherium*. Fariña (2002, later summarised by Fariña et al. 2013) calculated that a hairless 4-tonne sloth with a typical placental metabolism would be thermally neutral at -17°C. As a mid-latitude creature living in a semi-arid temperate climate (Bargo et al. 2001), this result paints Megatherium as having elephant-like issues with staying cool. The environments inhabited by Megatherium are similar to those of modern northern Patagonia, and thus rarely, if ever, dropped to -17°C, and we have to wonder if the shaggy pelt traditionally applied to Megatherium would be cooking an already very warm animal. Given the arid settings inhabited by this sloth, water loss through panting would soon become a major problem for a heat-stressed Megatherium. We must also consider that a similarly sized-sloth, Eremotherium, lived in tropical temperatures in what is now Florida: if it had a similar thermal neutrality to Megatherium (which it almost certainly did), Eremotherium must have been pretty hot and bothered most of the time, even if it largely or wholly lacked fur.

*It's worth stressing that, contrary to popular belief, we do not have any skin preserved from megasloths: all the skin specimens we have stem from smaller ground sloth species.

Here's your reminder that I'm posting this on Halloween 2019: behold the horror of a near hairless ground sloth. A century and a half of seeing giant sloths with long, shaggy hair makes images like this hard to swallow, but there's a legitimate scientific case to be made for megasloths looking like this. We need to be careful that we don't let tradition and expectation blind us to what might be a more tenable hypothesis of life appearance.

Modern sloths, of course, have an unusually slow metabolism, and it's appropriate to ask how much that might affect thermal neutrality of their giant cousins. Fariña (2002) calculated that halving the metabolism of a naked Megatherium leads to thermoneutrality at 10°C, a figure comparable to animals that inhabit temperate settings today without the need for long, shaggy fur. This being so, perhaps mass alone might have been enough to keep Megathium warm, even if it had an unprecedentedly low metabolic rate for a mammal.

Fariña (2002) also computed the thermoneutrality of a two tonne Mylodon darwinii in both naked and shaggy configurations. His estimates give thermal neutrality at -4°C without fur, and -28°C once a 4 cm thick hairy covering was applied. This matches expectations that fur makes a large difference to the thermal neutrality of large animals and also implies that, even without hair, Mylodon was pretty cold tolerant. Of course, fossil evidence shows that Mylodon was hairy, suggesting that we have a species adapted for dealing with extreme cold. This seems sensible given what we know of ground sloth distribution. Mylodon lived much further south than Megatherium, at the southern tip of South America, and also at high altitude. Unlike Megatherium, it would have routinely experienced sub-freezing temperatures and probably needed extra insulation to survive harsh winters. There's more work to do with Fariña's sloth calculations (both his 2002 and 2013 contributions to this topic are short and don't play with as many variables as I'd like) but these results are certainly thought-provoking as goes our considerations of the life appearance of sloths, and perhaps other giant extinct animals too.

Turning our attention now to extinct giant reptiles: I'm not aware of any studies that calculate thermal neutrality for large dinosaurs, but the sort of figures suggested for multi-tonne sloths are probably reasonable assumptions if we assume a mammal-like metabolic rate. Some vindication of this stems from studies suggesting that large dinosaurs had elephant-like issues with overheating. Rowe et al. (2013) questioned how long it would take a 3655 kg Edmontosaurus to overheat with continuous exercise and, even though their model assumed a sub-mammalian metabolic rate, just 3.5 (endothermic) or 4 (ectothermic) hours of walking in daytime temperatures typical to mid-latitude Late Cretaceous settings would elevate Edmontosaurus core temperatures to lethal levels. They suggested that, like large mammals, giant dinosaurs might have relied on panting, finding shade and water, resting during the warmest parts of the day, and nocturnal behaviour to avoid heat stress.

How quickly would it take for Edmontosaurus to overheat when subjected to low-grade exercise during the daytime? Not that long, despite it not being the largest dinosaur, nor the most insulated. What might this graph look like for a hypothetical larger, fluffier dinosaur living in the same habitat? Modified from Rowe et al. (2013).

This is some major food for thought given that the Edmontosaurus model of Rowe et al. (2013) lacks an insulating skin cover and is considerably smaller than some dinosaurs we routinely coat with thick layers of fluff. If 3-4 tonne scaly dinosaurs were already experiencing elephant-grade issues with heat build up during exercise, surely 6 tonne coelurosaurs living in the same climates would experience similar issues, even if only covered in scales? Everything we understand about the scaling of thermal energetics suggests that heat retention problems would get worse, not better, in larger animals, and it might be unrealistic to assume coelurosaurs twice the mass (or more) of Edmontosaurus were comfortable wandering around with a thick, insulating blanket of feathers.

Would body shape - such as having a dinosaurian-grade long necks and tails - have helped avoid the issues of heat retention? Seemingly not. Don Henderson’s (2013) models of sauropod thermoregulation found that skin area does not scale rapidly enough with increased body size, even with proportionally long necks and tails, to effectively cool their bodies. Sauropods are probably our best bet for dinosaurs using body shape to dump unwanted heat and, if even their skin area can't keep pace with internal heat production, other dinosaurs were unlikely to have managed either. This seems to match expectations from Porter and Kearney (2009) that elongate body shapes affect thermal neutrality, but that the effects of elevated body mass are difficult to circumvent.

Although some of the most extreme neck and tail proportions exist in the largest sauropods, such as Dreadnoughtus, these anatomies do not augment their surface area enough to counter the increase in bulk and heat production associated with gigantic body scaling. If sauropods - animals famously observed as being thin at one end, much much thicker in the middle and then thin again at the far end by A. Elk (1972) - couldn't rely on their necks and tails for this task, other dinosaurs likely couldn't either.

We needn't just rely on equations and computer models for evidence of high heat loads in large dinosaurs: we also have direct fossil evidence suggesting them. Brand new research by Ruger Porter and Lawrence Witmer (2019) has noted that large dinosaurs had enhanced vascularity in their skulls related to shedding heat. Like other reptiles, dinosaurs likely used panting and cooling sinuses in their heads to radiate heat, and they seem to have increasingly relied on these mechanisms at large size. Porter and Witmer's study shows a strong correlation between body size and development of these cranial cooling mechanisms in all three major dinosaur groups, suggesting that superior cooling anatomy was acquired independently in large-bodied dinosaurs regardless of the body shapes or integuments common to their clades.

We can also - perhaps more controversially - look at our current understanding of dinosaur skin as matching expectations of thermal energetics. And yes yes yes, our data here is less than perfect, taphonomic issues abound and we still have large gaps in our understanding of dinosaur skin. But it's nevertheless interesting that - as I write this in October 2019 - we're still finding indications of scales in virtually all dinosaurs above the 1.5 tonne mark ("the Yutyrannus threshold") regardless of whether that group is phylogenetically likely to sport fibres or not. We typically consider coelurosaurs in this context (e.g. Bell et al. 2017) but perhaps we should also consider ornithischians as evidence of this relationship too. At least some smaller ornithischians were covered in fuzz (e.g. Godefroit et al. 2014) but scales dominate in all sampled multi-tonne species. So yes, while our dataset of dinosaur skin configurations might just reflect a number of preservational and taphonomic factors, we have to be open to the possibility that we're actually seeing how dinosaurs adapted to large size. It's also worth stressing that, given estimates of thermal energetics in large extinct animals, an extensively fuzzy giant dinosaur would actually be pretty surprising.

We don't discuss it much, but the well-documented scaly hides of large ornithischians, such as Triceratops, might represent the same thermal responses postulated to explain the presence of scales in large theropods. We need a lot more data on the skin of smaller ornithischians to test this, but it's a hypothesis consistent with our understanding of heat retention in animal scaling.

A response to this last paragraph might be that certain Mesozoic settings were actually a lot colder than we generally assume, and that maybe even large dinosaurs needed extra insulation to stay warm. While this argument has some merit, we need to be careful not to overstate how cold these settings were, as well as consider some of the temperature values associated with thermoneutrality in very large species. It's true that the Mesozoic was not the global tropical hothouse we once assumed it was, but temperatures were still generally warmer than today. Many so-called 'cold' Mesozoic climates would be quite tolerable to modern temperate species. Maastrichtian Mongolia, for instance, which many artists are now populating with woolly Deinocheirus, shaggy Therizinosaurus and fuzzy Tarbosaurus, had mean annual temperatures between 5-10°C and a climate similar to Shijiazhuang, northeastern China (Owocki et al. 2019). This predicts average daily temperatures above 10°C for most of the year but only a month or so of average daily temperatures around freezing. It seems doubtful to me, given what's outlined above about the thermal energetics of 3-4 tonne animals, that six-tonne (or more) coelurosaurs would need thick, full body insulation to live in this climate. To the contrary, modern cattle or horses could have lived in these settings without discomfort. Similar statements can be made about Maastrichtian Alaska, which was cold in the winter, but lacked sustained freezing temperatures (Spicer and Herman 2010). If two-tonne animals are thermally neutral at c. -4°C (Fariña 2002), the 2-4 tonne hadrosaurs and ceratopsids of these habitats might have survived untroubled by the winter months without needing extra insulation.

Yet more art of extensively fuzzed large dinosaurs, which I once assumed would be sensible given the cold temperatures of Maastrichtian Alaska. Given everything outlined here, I'm now looking at these Pachyrhinosaurus from 2015 as being over-insulated for their chilly, but not deeply-cold habitat.

We thus have to be careful not to get carried away when we hear that palaeotemperatures of a given ancient setting have been revised down. A "cool" Mesozoic climate has yet to equate to modern-grade tundra or polar desert, and we needn't start restoring animals as looking suited to such habitats. It also pays to remember that most Mesozoic climates were warmer, sometimes significantly warmer, than these cooler examples. O'Connor and Dodson (1999) suggest that a modern elephant dropped into the climates of Late Cretaceous North America would experience the same issues, or worse, with overheating as they do today. This being the case, perhaps a lot of big dinosaurs spent much of their lives feeling pretty darn warm.

So... about those giant shaggy coelurosaurs and sloths...

Let's bring this long article into land by returning to our original question: how likely is it that giant fossil animals, such as giant sloths and giant coelurosaurs, were covered in extensive fuzz for the purpose of insulation? To me, our discussion of the thermal energetics, heat production and dissipation, and data from the fossil record suggest a few key takehomes:

1. Animals do not need to be gigantic nor super shaggy to be tolerant of cool temperatures. Species weighing several hundred kilogrammes, and with only moderate insulation, are thermally neutral at temperatures approaching freezing, and those that exceed a tonne or so have TNZs extending below 0°C. Simply being large is a very effective way to stay warm, regardless of body shape or phylogenetic affinity.
2. Near-naked multi-tonne animals struggle to shed body heat even in cool conditions because, when engaged in any activity, they generate more heat than they can easily lose. Hypothetical structures that would inhibit heat loss further - such as thick fur or feathers - seem maladaptive and unlikely for such species.
3. We seem to lack data on the thermal energetics of the very largest fossil land animals, but there's no reason to think they would have escaped the the challenges of heat dissipation outlined above. If anything, these issues would be more far more pronounced than that of the taxa discussed in this post, on account of their increased body mass.

These points considered, perhaps reconstructions of large animals that have jettisoned most or all of their fibrous integuments are viable interpretations of fossil giants, regardless of their ancestral integument. I stress "most or all" fibres because, of course, we also have data suggesting that sparse, short fibres can help negate thermal boundary issues (Myhrvold et al. 2012), and there's no reason to assume this wouldn't apply to giant sloths, indricotheres, coelurosaurs etc.

I'm certainly now looking at some of my own portfolio with new eyes. I find it hard to believe that my super-fluffy Therizinosaurus, Pachyrhinosaurus and even my traditionally hairy Megatherium aren't sweltering to death under all their fluff. Fariña's naked sloths might be weird and scary to us after centuries of depicting them with shaggy fur, but - so far as I can tell - his ideas fit our understanding of animal energetics and Megatherium habitat far better than the established model. It's worth remembering that a counter case for Megatherium requiring extensive hair has never been made, and that our standard reconstruction is, from the perspective of basic physics, actually far more outlandish than the seemingly radical Fariña model. It may seem shocking, but the case for a hairy Megatherium is less developed than the case for a hairless one.

Putting my artistic money where my mouth is, here's the giant, six-tonne ornithomimosaur Deinocheirus restored with just a sparse, localised set of filaments around the head, shoulders and tail tip. After researching this article, images like this read as more plausible to me than the general 'walking haystack' guise Deinocheirus has attained in palaeoart.

And yes, we might want to apply the same caution to giant coelurosaurs, even species we're used to clothing in extensive fuzz such as therizinosaurs and deinocheirids. Perhaps even the 'feather capes' we sometimes drape on giant tyrannosaurids are thermal overkill. Tyrannosaurus and similarly-sized tyrants are as large or bigger than living elephants, and it seems unlikely to me that animals of this size, mostly living in temperate or subtropical climates, needed even a small feather blanket to keep them warm. Our reconstructions of these animals which lean towards mammoth-like pelts seem especially untenable, given the impacts that even light feather coats would have had to species of their size. This does not rule out sparse fibres for heat loss or display of course, but a thick, shaggy pelt would surely be stifling - maybe even dangerously warm - given their body mass and the temperatures they experienced.

I'm aware that the argument I've presented here is a very broad brush, 'woods for trees' approach to this topic. I don't doubt that there are nuances and details to get into, and that there are many questions left to answer. For instance, what about the role of air sacs in dinosaurian cooling? What about climates which have high precipitation rates or strong winds? These are good points worthy of exploring, but - without wishing to add lots more detail to this already long article - I wonder if they're going to overturn the general arguments outlined here. With all indications being that giant animals are thermally neutral at very low temperatures, and that body mass seems to be the dominant effect on thermal neutrality, we're asking a lot of these additional factors to overturn the points made above. Note, for example, how Porter and Kearney's (2009, also above) assessment of wind speed on LCT follows the general trend of larger animals being less affected than smaller ones, and how it has very little impact on LCT for the largest animal in their study. We should assume even lesser impact in gigantic species.

I'm expecting a certain amount of harrumphing about this article from some quarters, especially from those who - like me - quite like seeing big, shaggy animals in palaeoart. They look cool, give off that 'new palaeo' vibe and provide us with lots of fun and exciting looks to explore. But, of course, palaeoart isn't really about what we like, it's about creating tenable, data-compliant takes on fossil species. So I'm going to end this article with a request: for those of us who want to continue restoring giant fossil animals with thick layers of hair and feathers, we need to demonstrate how the data presented here is wrong, and to the same calibre as the cited studies. What large modern animals deviate from well-established energetic scaling trends? What models of extinct animal physiology show that multi-tonne animals were immune to expected issues of thermal storage and heat dissipation? What are the flaws in papers arguing for low thermal neutrality in giant endotherms? Such a discussion would at least give us some actual data, and not just arm waving and intuition, to make predictions about how much fuzz extinct giant animals actually had. It's our job, after all, to ensure that the fluff in our palaeoart is kept on the bodies of our carefully researched restoration subjects, and isn't also a description of our approach to research.

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References

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