Bird biodiversity in heavy metal songs

Henrique M. Soares1, João V. Tomotani2, Barbara M. Tomotani3 & Rodrigo B. Salvador3

1 Massachusetts Institute of Technology. Cambridge, MA, U.S.A.

2 Escola Politécnica, Universidade de São Paulo. São Paulo, SP, Brazil.

3 Museum of New Zealand Te Papa Tongarewa. Wellington, New Zealand.

Emails: hemagso( at) gmail (dot) com; t.jvitor (at) gmail (dot) com; (at) gmail (dot) com; salvador.rodrigo.b (at) gmail (dot) com

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Birds have fascinated humankind since forever. Their ability to fly, besides being a constant reminder of our own limitations, was a clear starting point to link birds to deities and the divine realm (Bailleul-LeSuer, 2012). Inevitably, these animals became very pervasive in all human cultures, myths and folklore (Armstrong, 1970). In fact, they are so pervasive that they have found their way to perhaps the most unlikely cultural niche: Heavy Metal.

With some exceptions, such as raptors (Accipitriformes) and ravens/crows[1] (Fig. 1), birds are not typically seen as badass enough to feature on heavy metal album covers and songs, even though sometimes they already have the right makeup for it (Fig. 2).

Figure 1. Examples of album covers with birds: Devil’s Ground, by Primal Fear (Nuclear Blast, 2004), and the fantastic Winter Wake, by Elvenking (AFM, 2006). Source: Caratulas (2019;
Figure 2 Pied falconet, Microhierax melanoleucos, a species distributed from China to southeastern Asia; photo by Owen Chiang (2007;, used with permission. Gene Simmons, bassist and co-lead singer of KISS, with his Demon make up; source: Wikimedia Commons (Alberto Cabello, 2010).

As we highlighted above, the birds’ power of flight is their main feature, but they have another power up their feathery sleeves. And this feat is one that people tend to consider one of the most human endeavors of all: music. Most birds are deemed melodious creatures, like the slate-colored solitaire (Myadestes unicolor) from Central America and the celebrated nightingale (Luscinia megarhynchos), although some might seem almost tone-deaf[2] (Fig. 3).

Figure 3. The Crested Ibis, from Kemono Friends (Mine Yoshizaki, 2015), is made fun of in the series because of her awful singing. The character was based on the Japanese crested ibis, Nipponia nippon, a species once widespread through eastern Asia, but now severely endangered (BirdLife International, 2017). Sources: Japari Library (2018); Wikimedia Commons (Olyngo, 2017).

Birds (class Aves) can be largely divided in two groups: the order Passeriformes (with circa 6,000 known species) and “the rest” (several orders, totaling around 5,000 species). Members of the order Passeriformes are commonly called “passerines” or “perching birds” and include most of the species that typically comes to mind when we think of birds: sparrows, robins, starlings, blackbirds and crows. Inside Passeriformes, there is a suborder called Passeri[3], the “songbirds”, a group with roughly 5,000 species of animals. The vocal organ (called syrinx) of songbirds is modified in comparison to that of other birds and can produce complex sounds (Raikow & Bledsoe, 2000). Typically, these sounds result in bird song, but crows have their own way of communicating.

With all these bird species, some are bound to appear in heavy metal songs, right? We mean, besides eagles and ravens, of course. So, we decided to analyze the lyrics of thousands of metal songs in order to find ‘em birds (Fig. 4).

Figure 4. Skarmory, one of the few examples of a literal metal bird; more specifically, a Steel/Flying type. Source: Bulbapedia (2019b; The Pokémon Company, 1998–2019).

Here, we show how many songs talk about birds and which specific birds they mention. We also investigate how each bird groups is represented in the genre and in each subgenre. We will also talk a little bit about the biology of some of these animals to make you, our dear headbanging reader, more acquainted with this fantastic slice of Earth’s biodiversity.


Data collection

All lyrics used in this project were collected from Metal Kingdom (, a web compendium on metal music of diverse genres. To collect this data, we built a custom web crawler that navigated all music pages on the website. This collection yielded us three main datasets:

  • Bands: CSV file listing all bands found on the website.
  • Genre: CSV file mapping bands to their respective metal genre.
  • Lyrics: CSV file which contains the actual lyrics, as well a reference to the artist.

On 07/August/2018, we collected a total of 145,716 songs from 6,359 bands, spanning 368 different metal (sub)genres.

Data pre-processing

When we started going through the data we obviously ran into some problems. (If you’re not finding any problems in your data, you’re not looking hard enough!) In this section, we present some of the hurdles we had to overcome when working with this dataset.


A quick look into the data showed us a problem for our study: not all lyrics were in English. For example, below are the verses of “Ohne Dich” by German band Rammstein (2004):

Und der Wald er steht so schwarz und leer,

Weh mir oh weh,

Und die Vögel singen nicht mehr.

We may have some additional language skills to identify ‘die Vögel’, but we certainly won’t know every language in the dataset. Because of this, we decided to restrict our study only to songs in English. However, this posed another problem: we have no structured data about the language of each song, and this information would need to be inferred from the lyrics themselves.

Fortunately, this was also a problem for Google when deciding in which language you’re searching in during your queries, and they were kind enough to opensource their implementation[4]. They used a Naïve Bayes approach, which achieved 99.77% accuracy when classifying news articles in over 49 languages (Nakatani, 2010). Using this approach, we managed to label almost all lyrics by language, identifying 43 different ones in the corpus. The distribution of the languages can be seen in Table 1.

Table 1. Frequency count of languages for lyrics. Languages are represented by their ISO 639-1 codes.[5]

This method, however, is not without its own problems. We were curious, for instance, as to why there were so many lyrics in Romanian (ro). A more in-depth investigation revealed that instrumental songs would have only the text “(instrumental)” listed as their lyrics –the algorithm struggles when classifying such short words. However, since this problem affected only songs without lyrics (that is, songs that won’t mention any birds at all) we opted to just remove them from the dataset.


Another problem we identified was homonyms: words that sound and are written the same, but have different meanings depending on the context. Consider, for example, the following excerpts:

Song: White Synthetic Noise Lyrics

Band: … And Oceans

Song: Hourglass

Band: A Perfect Circle

Sorrow sings of everything but survival doesn’t seem to ring
Isolate, contain your pain to outlast the taste of misery
I believe the curse will swallow it’s[6] teeth
Show the stars and I can clear the air and love the end
Red flag red, all the sentinels are damned
The Tokyo kitty, swallow, rose, and canary
Tick tick tick, do you recognize the sounds as the grains count down
Trickle down right in front of you?

The word ‘swallow’ has clearly different meanings in these songs. In the former, it is a verb, that is, the act of causing or allowing something to pass down the throat. In the latter, however, we have a reference to a Hirundinidae bird that may or may not be able to carry a coconut.

To address this problem, we must distinguish between the different uses of homonyms. One way of doing this is classifying each word in a text by its Part of Speech. A part of speech is a category in which a word falls given its syntactic function in a sentence. In the first example above, ‘swallow’ is classified as a verb, while in the second example it is classified as a noun. Since we are interested in identifying mentions of birds in lyrics, knowing that a word function as a noun in the sentence can help us reduce the homonym problem. (Unless, of course, they are nouns for both their meanings. In this case, this approach won’t help much.)

The process of classifying words like this is known as Part-of-Speech tagging, or POS tagging in short. POS tagging can be seen as a supervised learning problem, as we can train a classifier to identify these tags given a pre-labeled dataset of token sequences and tags. For this project, we opted to use a pre-trained model available in NLTK. This default English POS-tagger consists of a Greedy Averaged Perceptron implemented by Honnibal (2013).

Let’s see how this works for our examples. POS tagging on the first one yields the following result:

Word I believe the curse will swallow it ‘s teeth .

The tags are represented by abbreviations from the Penn Treebank Tagset[7]. In this case, we can see that ‘swallow’ was assigned the POS tag ‘VB’ (Verb, Base Form) and as such, should not be counted as a bird. Let’s see how this works out with our second example:

Word The Tokyo kitty , swallow , rose , and canary .
Tag DT NNP NN , NN , VBD , CC JJ .

Here, ‘swallow’ was assigned the POS tag ‘NN’ (Noun, singular or mass) and as such, should be counted as a bird. However, this example also shows that this method is not perfect, as ‘canary’ received a ‘JJ’ tag (Adjective). However, since the alternative would be to manually annotate POS tags for the whole corpus, we decided to proceed with this alternative.


With both language and homonyms out of the way (well, sort of), we can finally tackle our last problem: plurals. Consider the following two examples:

Song: For the birds

Band: 8 Foot Sativa

Song: Scavenger

Band: A Static Lullaby

To close my eyes
Reduce you to black
Nothing more than an insignificant shadow among the vultures
I will walk away
Scavenger, where does the vulture sleep?
And when you speak to him
Will you bring him to me, bring him to me
Scavenger, bring forth the jackals teeth

We can see that both songs mention the bird ‘vulture’: the first one uses the plural form while the second uses the singular. We wanted to count both references as the same bird, so how could we achieve that?

One solution would be to increment our list of “bird terms” to include all plurals of bird name, as well as a mapping to a root form of the word. This, however, would be a lot of work. This looks like a common problem when doing natural language processing, so we searched for what we could do to address it.

Lemmatization is the process of removing inflectional forms, finding the root word, that is, the lemma, so that they can be analyzed as a single group. It is widely used when running searches for terms in documents as a way to correctly match-related terms. Fortunately, there are various lemmatizers implementations for different languages. For this problem, we will use the WordNet lemmatizer available in the NLTK library.

Lemmatizer usually requires the POS tag of the word, but fortunately, we got that covered. Running the WordNet Lemmatizer in our first example yields the following: “Nothing more than an insignificant shadow among the vulture.”

You might be thinking: “Wait. That much work just to take out an ‘s’ from the end of the word?”. However, remember that grammatical number can be way more complex than that (e.g., goose and geese), and using a proper lemmatizer takes all that complexity into account.

Data aggregation

OK. We detected the language of our metal songs and filtered only those in English. We tagged the part-of-speech of all our words, and we even lemmatized them to ensure consistency. What is then left to do?

Well, we need to count our birds! For this project, we decided to use a static list of bird names commonly used in cultural works. The list can be seen in Table 2.

Table 2. Common bird names used in this work, arranged alphabetically.

We only counted the term in our dataset if the POS tag of it corresponded to a noun. This reduced the likelihood of homonyms such as ‘swallow’ bird and ‘swallow’ verb, but unfortunately will do nothing for homonyms such as ‘tyrant’ flycatcher (Tyrannidae) and ‘tyrant’ Cersei Lannister. The count was done in two different ways:

  • Occurrence counts: This method counts the number of times a word appears, counting multiple repetitions in the same song as distinct occurrences. For example, when counting the word “bird” in the classic song “Surfin’ Bird”, by The Trashmen, this counting method would yield 82 occurrences.
  • Song counts: This method counts the number of songs in which a word appear, counting multiple repetitions in the same song as a single occurrence. Keeping with our previous example, “Surfin’ Bird” would only wield 1 as the count of the word “bird”.

To validate our methods, let’s take a look at the top 5 most metal birds:


Occurrence count

Song count

bird 2874 2222
eagle 1738 1036
tyrant 1737 1221
raven 1603 1205
vulture 1230 990

That corresponded with our expectations, even though we probably are suffering from a homonym problem with all those tyrants showing up. The tyrant flycatchers are not actually that metal (Fig. 5).

Figure 5. Too cute for metal? Left: a tyrant flycatcher, known as western kingbird (Tyrannus verticalis), lives in North and Central America; source: Wikimedia Commons (MdF, 2010). Right: the grey-hooded Attila (Attila rufus), from southern Brazil, is actually named after a tyrant; source: Wikimedia Commons (D. Sanches, 2010).

We also grouped our bird count by each metal genre. In this way, we will be able to run an analysis on how different birds relate to different types of metal. Given that we had 368 different metal subgenres, we had to summarize this if we wanted to run any meaningful statistical analyses. We summarized them using the definitions from Wikipedia into “just” 37 categories, listed in Table 3.

Table 3. List of metal genres used in our analyses. Note that: (1) occasionally, a rock genre popped up in the database; (2) the category ‘Various’ include weird singletons we just could not classify elsewhere, such as “A Capella”.



The word ‘bird’ appears in 2,222 songs, as we’ve seen above. It seems quite a lot, but on a closer look, it’s not quite: that number represents only about 1.5% of all the songs in the database. We honestly didn’t know what to expect when we started this project, so it is hard to decide if that’s a lot of birds or too few of them. We are more inclined to the latter, given that birds are such prominent symbols in most worldwide cultures.

But more specific mentions of popular bird names also appear in several songs. Some likely refer to a single species, like ‘nightingale’ (Luscinia megarhynchos) and ‘blackbird’ (Turdus merula). Most common names, however, refer to a whole group of species, like ‘eagle’ and ‘penguin’, and not to a particular species in each group. Finally, some common names, like ‘dove’ and ‘swan’, while being representatives of larger groups, in this context probably refer to the most common European forms, the rock dove (Columba livia) and the mute swan (Cygnus olor).

We present below the number of times each type of bird is mentioned in a metal song and we do this in two ways. Table 4 shows the total count (the “occurrence count” from the example above), which includes all the times a particular word pops up in the lyrics. As explained above, this includes repetitions within the same song, such as in chorus sections. For instance, ‘eagle’ appears several times in Helloween’s “Eagle Fly Free” (1988). Table 5 shows the counts ignoring all the repetitions (the “song count” from the example above). This way, ‘eagle’ is counted only once in Helloween’s song.

Table 4. Total count of common bird names in heavy metal songs.


Table 5. Count of common bird names in heavy metal songs, avoiding repetitions within the same song (e.g., chorus sections).

We think the second type of counting (Table 5) is a better representation of bird abundance in metal songs, so we will only refer to this one in our discussion below[8]. However, if should be noted that eagles are the most used bird according to Table 4, but they come in second in Table 5, having switched places with ravens. Even though we knew from simple life experience that these two were the most metal birds, we expected eagles to get the crown in both types of count.

Popular birds

So now we can say with certainty that the most metal bird is the raven (Fig. 6). The word can refer to several species worldwide, but it is logical to assume that people usually think of the common raven (Corvus corax; Fig. 9) when using the word. This species is distributed throughout the Northern Hemisphere and is one of the largest passerines alive. Ravens are omnivorous animals, extremely opportunistic and versatile, and their intelligence is well-known to biologists.

Figure 6. While we were writing this article, the Gen VIII Steel/Flying Pokémon Corviknight was aptly announced. Gen VIII’s Galar region is based in England, birthplace of heavy metal (Allsop, 2011). So thank you, Game Freak Inc.! Source: Bulbapedia (2019a; The Pokémon Company, 1998–2019).

Ravens are undoubtedly one of the most common birds in folklore and pop culture but are generally regarded as birds of ill-omen and related to “evil stuff”. Thus, they are well-represented in Black and Death Metal, with respectively, 328 and 152 occurrences.  However, they are sometimes associated with nicer things, like the ravens from the Tower of London (Kennedy, 2004) and Nordic mythology. The relationship with the latter is very clear given the 114 times this bird appears in Pagan Metal songs.

In second place, we have the eagle, a staple of Power Metal and original Heavy Metal (Fig. 1), with 197 and 193 counts, respectively. Eagles are very likely the most prominent bird symbol of all in Western culture (Armstrong, 1970): Zeus, the Roman Empire, European heraldry (especially Germany and Austria), and of course, ‘Murica. As the “king of birds”, the eagle is almost always a symbol of power or leadership. The ‘eagle’, however, will not be the same bird species for every headbanger: American bands and fans will always think of their national symbol, the bald eagle (Haliaeetus leucocephalus), while others will possibly think of the golden eagle (Aquila chrysaetos) or other more regional species. Eagles are part of the Accipitridae, family together with hawks, kites and Old world vultures (see below); however, the name ‘eagle’ is given to several large species that are not actually too closely related to each other (e.g., booted eagles, snake eagles, sea eagles, harpy eagles; Lerner & Mindell, 2005).

The third most used bird is the vulture. This term does not refer to any specific vulture species, but most likely to a sort of over-generalized stereotypical representation of a vulture in popular imagination. Vultures suffer from a bad press, being often mindlessly associated with corpses, death and decay due to their scavenging diet. Unsurprisingly, it is a prevalent bird in Death and Black Metal songs, with 228 and 143 counts respectively. Trash Metal also has a good number of counts (117), but given this genre’s more political lyrics, ‘vulture’ is here often related to bad people or practices.

The popular name vulture actually refers to 23 species worldwide, distributed in two distinct yet closely related biological groups (Buechley & Sekercioglu, 2016): the Old World vultures (Fig. 7) and the New World vultures (Fig. 8). Old World vultures belong to the family Accipitridae, the same as eagles and hawks, while the New World ones (which include condors) comprise the family Cathartidae. The scavenging habits of vultures evolved independently in these two lineages and in both cases has led to some common adaptations to this way of life: large bodies and wings, powerful beaks and featherless heads (Buechley & Sekercioglu, 2016).

Figure 7. Examples of Old World vultures. Top: Egyptian vulture (Neophron percnopterus). Bottom: griffon vulture (Gyps fulvus). Source: Wikimedia Commons (D. Ash, 2013 and S. Krause, 2011, respectively).
Figure 8. Examples of New World vultures. Left: turkey vulture (Cathartes aura) and Andean condor (Vultur gryphus). Source: Wikimedia Commons (respectively S. Blanc, 2007, and E. del Prado, 2007).

The fourth bird on our list are the crows. Again, ‘crow’ can refer to any out of 30-something species. The typical European black crow is called carrion crow (Corvus corone; Fig. 10); the hooded crow (Corvus cornix) is also very common in the continent, but it is not entirely black and so possibly unsuitable for metal songs. North American headbangers will be typically more familiar with the American crow (Corvus brachyrhynchos).

Note that all these species belong to the genus Corvus and, in fact, so does the raven (see above). People get confused about these birds all the time and often use the words ‘raven’ and ‘crow’ interchangeably. While neither word has any true biological meaning (that’s what scientific names are for, after all!), we will give you some pointers as how to differentiate the common raven from those crows. Also, after reading this, try checking all those raven and crow illustrations on heavy metal albums – you’ll be surprised how many of them are just plain wrong.

There are several differences to keep an eye out for when trying to identify crows and ravens (BTO, 2013). First off, ravens are huge, with a wingspan similar to a buzzard’s and an even larger body. If you’re uncertain about the identity of the bird you’re seeing, it’s probably a crow. When you finally encounter a raven, you’ll immediately know it. But there are other features that might help you out if the animals are seen far off, flying or just through photos.

Crows have a rounded head, with the plumage arranged neatly on the body; their beak is deeply curved and stout (Fig. 10). Ravens have very long and heavy beaks, ruffled throat feathers, a barrel-like chest and a long neck, which together gives them a heavy-headed impression (Fig. 9). In flight, crows beat their wings more heavily and their fan-shaped tail is clearly seen (Fig. 10). Ravens, however, tend to soar more; the feathers on their wing tips looks more like a raptor’s when flying and they have a long and wedge-shaped tail (Fig. 9). Finally, crows have a far-carrying “caw” vocalization, while the ravens’ calls are a deep and hoarse croak.

Figure 9. Common raven. Source: top: Wikimedia Commons (F. Veronesi, 2016); bottom: iNaturalist (A. Viduetsky, 2019).
Figure 10. Carrion crow. Source: top: Wikimedia Commons (‘Loz’ L.B. Tettenborn, 2007); bottom: iNaturalist (E. Bosquet, 2019).

Unexpected birds

There are some unexpected results. For starters, we imagined hawks and falcons would rank higher on the list, as well the nightingale, which is typically associated with song and poetry. We also have lots of mentions to ducks, geese and chicken, but a good portion of them refer to expressions (e.g., sitting ducks) or, metaphorically, to people.

However, there were some actual surprises. From the list of bird “species” we initially came up with (Table 2), we had included some oddballs just to be thorough and have all avian orders represented. To our surprise, however, our search came up with some occurrences for them, like penguins, ostriches, macaws and toucans.

The song Ostrich, by American band Gloomy Grim (2000), focuses on the fallacious idea that ostriches (Struthio camelus) bury their head in the sand to hide. They do not. What they are doing is inspecting and caring for their eggs; they dig shallow nests and from a distance, it might look like an ostrich has its head buried in the sand (American Ostrich Association, 2019). In fact, ostriches have no need to hide; besides being the largest living dinosaur and having a mean kick, they are the fastest animals on two legs (Donegan, 2002; Stewart, 2006).

All mentions of penguins come from a single Swedish Black metal band called Satan’s Penguins. Several of their songs stick to the theme, such as “Antarctic Winterstorm”, “Behind Mountains of Ice”, and “Night of the Penguins”. Despite being thought of as birds from the icy wastes of our planet, most penguin species live in sub-Antarctic or temperate areas (Davis & Renner, 2003). Actually, the Galapagos penguin (Spheniscus mendiculus) is endemic to the Galapagos Islands, very close to the equator.

Battle of the genres

One curious thing to see was how each genre has its own favorite bird (Table 6). However, when we looked more closely at these results, they are entirely expected. Eagles are the stars in genres such as Heavy, melodic, Power and Speed Metal, while ravens dominate the Gothic, Folk and Pagan genres. The preference of owls in Electronic, however, is a mystery to us.

Table 6. List of metal genres and the most cited bird “species” in their songs.

We could also check which genre is the most biodiverse, that is, which genre cites the largest number of bird “species” in its songs (Table 7). The undisputed crown goes to Death metal, with 46 species; after it, we have Power, Black and Heavy Metal all clustered together with 41, 40 and 39 species, respectively. However, this might just be an artifact of the sheer number of Death Metal songs: this genre has twice more songs in the database (a total of circa 46,000 songs) than the second genre (Black Metal, with circa 23,000). So the change of a bird popping up in a Death Metal song is just higher because of this. (Also, several species are mentioned just once and birds are not mentioned that much in their songs; see also Table 8.) The other three genres we mentioned are better balanced: Black Metal has 23,000 songs total, as shown above, while Power Metal has circa 17,000 and Heavy Metal 22,000.

Table 7. List of metal genres and the total number of bird “species” featured in their songs.

The least ornithological genre is Grunge, but one could rightfully argue that “grunge’s not metal” or “who cares about grunge anyway?” So the least ornithological true genres are Dark Metal and Christian Metal (Table 7).

However, if you take into account the proportion of songs that mention birds (Table 8), Pagan Metal is the true bird-loving (or should we say raven-loving?) genre. Around 13.5% of Pagan Metal songs mention some sort of bird. The second place goes to Folk Metal/Rock, with 11.2% of songs mentioning birds. The least bird-friendly genres are Alternative Metal (1.7%) and Glam (1.9%).

Table 8. List of metal genres and the percentage of songs that mention birds.


And what about the songs that have the most birds? Well, we have two worth mentioning, one from a big name in metal and the other from, well, a rather obscure band. First is “The Crow, the Owl and the Dove” by Finnish symphonic metal band Nightwish, from the album Imaginaerum (Nuclear Blast, 2011), later also released as a single (Fig. 11). As expected from the title, there is a good avian diversity in this song: besides the three titular birds, there is also mention of the swan. The second song is “Proverbs of Hell Plates 7-10” by Norwegian black metal and avant-garde metal band Ulver[9], from the album Themes from William Blake’s the Marriage of Heaven and Hell (Jester Records, 1998). This song mentions the peacock, eagle, crow and owl.

Figure 11. Album cover of The Crow, the Owl and the Dove by Nightwish (Nuclear Blast, 2012). Source: Wikimedia Commons.


We have certainly been surprised by some of our findings: from ravens overtaking eagles to the odd penguin and ostrich popping up in some lyrics. As we’ve argued, birds are very diverse group of animals, and several species are deep-seated symbols in cultures worldwide. So maybe it’s about time heavy metal left the tropes of ravens, eagles and vultures on the bench for a while and let other avian stars shine (Fig. 12).

Figure 12. Washimi, the secretarybird from Aggretsuko (2018) seems to enjoy some good old death metal in the karaoke scenes in Netflix’s animated series. Yes, secretarybird is an actual thing: the species is called Sagittarius serpentarius and it is a terrestrial bird of prey (Accipitriformes) that inhabits the savannah and open grasslands of sub-Saharan Africa.



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About the authors

Henrique Soares is an engineer and machine learning enthusiast, not particularly knowledgeable in either birds or metal. When he is not working on unconventional applications of machine learning, Henrique spends his time wondering how could there be people that don’t know about the bird, because everyone knows that the bird is a word! A-well-a-bird, bird, b-bird’s a word, a-well-a…

João Tomotani is a mechanical engineer currently working with Supply Chain. Though he is more of a power/melodic metal enthusiast, he agreed to focus on birds instead of dragons in this research.

Dr. Barbara Tomotani is a biologist and the only one in this group whose work actually focuses on birds. She is not a big heavy metal fan and does not work with heavy metal birds, preferring the tiny flycatchers. But she has certainly liked the new metal bird Corviknight.

Dr. Rodrigo Salvador is a zoologist who lately has found himself working with a lot of bird-related stuff. One of the first songs he remembers ever hearing as a child was Walk of Life, by Dire Straits – his sister’s “fault” and an influence that eventually led him down the road to metal. He’ll quickly tell you his favorite bands are Queen and Avantasia, but he’s hard pressed to decide his favorite bird.

[1] We’ll solve the raven vs crow problem later.

[2] If we’re being completely honest, some lead singers out there also seem to be somewhat tone deaf, especially in some of the more peculiar subgenres of heavy metal.

[3] The name Oscines was also used for this group and can still be found in the literature.

[4] You can find it here:

[5] Check the Library of Congress for the codes:

[6] This is not a typo on our part. The lyrics are like this in our source.

[7] You can find it here:

[8] We excluded ‘tyrants’ from the analysis due to the homonym problem presented above. Likewise, we excluded ‘roller’, which is typically used in the term ‘rock n’ roller’ rather than referring to the members of family Coraciidae.

[9] We confess none of us had the slightest idea Ulver even existed.

Check other articles from this volume


Pokémollusca: the mollusk-inspired Pokémon

Rodrigo B. Salvador¹ & Daniel C. Cavallari²

¹ Museum of New Zealand Te Papa Tongarewa, New Zealand.

² Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Brazil.

Emails: salvador.rodrigo.b (at) gmail (dot) com, dccavallari (at) gmail (dot) com

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The phylum Mollusca appeared during the Cambrian Period, over 500 million years ago, alongside most other animal groups (including the Chordata, the group we belong to). There are even some older fossils that could be mollusks, although their identity is still hotly debated among scientists.

Mollusks are a very biodiverse group. We do not yet know the precise number of species, since many are still unknown and being described every year. However, estimates go from 70,000 to 200,000 (Rosenberg, 2014). And that’s just for the living species. As such, mollusks have long been considered the second most diverse group of animals – the first place belongs to arthropods.

Mollusks can be found in almost all sorts of habitats: land, freshwater and marine, including the deep sea and hot vents. The only thing they can’t do is fly.

They are also a very unique group in terms of body shapes (morphology), including extremely disparate forms: snails, slugs, clams, mussels, squids, octopuses, nautiluses, chitons, tusk shells, and the odd worm-like aplacophorans. And there were other forms yet, which are now extinct: ammonoids, belemnites and rudists. Mollusks go from tiny snails less than a millimeter long to giant squids, almost 20 meters long and the largest known invertebrates.

The main groups of mollusks, however, are just three: Gastropoda, or gastropods, which include snails and slugs; Cephalopoda, or cephalopods, which include squids and octopuses; and Bivalvia, or bivalves, which include mussels and clams.

Curious creatures that they are, mollusks make nice “monsters” and are constantly being featured in video games (Cavallari, 2015; Salvador & Cunha, 2016; Salvador, 2017). One very famous game that features mollusks is Pokémon, a franchise that started with two games released by Nintendo for the Game Boy in 1996. More than 20 years later, the series is still strong, currently on the so-called seventh generation of core games, but counting with several other video games, an animated series, films, a card game, and tons of merchandise. Also, there’s an eight generation of games on the horizon.

Most monsters in Pokémon are based on real animals (see, for instance, Tomotani, 2014; Mendes et al., 2017; Kittel, 2018), so the goal of this article is to present those based on mollusks. Some of them were just broadly based on a larger group of mollusks, such as ‘octopuses’, while others seem to have been inspired by particular species. Thus, we indicate the real species or group that served as inspiration for the monsters and explain a little bit about their biology. Whenever possible, we outline specific features of the real animals that were transported to the games (such as types, moves, abilities, etc.).


We analyze each mollusk Pokémon below; they are listed in the same order as in the National Pokédex (this number is given with a “#” on each entry). All the illustrations of the Pokémon reproduced here are the official art by Ken Sugimori and were extracted from Bulbapedia ( Likewise, all information on the Pokémon (size, weight, and description of abilities and moves) were taken from their entries in Bulbapedia, considering only the game’s current generation (Gen VII).

The systematic classification of the mollusks used here follows Bouchet et al. (2010, 2017) and WoRMS (World Register of Marine Species). Images of real mollusks were extracted from Wikimedia Commons, except where otherwise noted; credits are given in each figure’s caption.


(#090; Type: Water)

Class: Bivalvia (bivalves)

Order: Pectinida (scallops and oysters)

Family: Pectinidae (scallops)

With its googly eyes and what seems to be a hanging tongue, Shellder looks somewhat scared or mesmerized (or perhaps both). This small shell-bearing fellow is surely designed after a bivalve mollusk. And, curiously enough, the large eyes are actually not out of character: even though most bivalves have no eyes, the Pectinida, a.k.a. the scallops and their allies, are an amazing exception. These animals are found in all of the planet’s oceans and the family Pectinidae is in fact one of the largest marine bivalve families, including over 300 living species belonging to 60 genera (Waller, 2006). They do have incredible eyes with a very intricate structure that allows them to measure amounts and intensity of light coming from different directions (Morton, 2008). As far as we know, scallops can discriminate light from dark, spot surrounding algae, and perceive moving objects or obstacles (and react accordingly). Judging by its real-world counterparts, Shellder shouldn’t necessarily have a hard time aiming its “Clamp” or “Razor Shell” attacks, hiding from someone else’s attacks, or swimming away from menacing foes. And yes, scallops also have awesome swimming abilities, which are also not common among bivalves in general. Most bivalves are very good swimmers during their early days as planktonic larvae (known as veligers), but become sessile when adults, spending their lives burrowed in the sand or attached to a rock or other hard surface.

Top: Scallops on the seabed (CSIRO, 2001). Bottom: Close-up of the blue eyes (M. Krummins, 2014).

As for the shell itself, Shellder seems to belong to the family Pectinidae because of its overall shape. Even so, Shellder’s tongue, in particular, is a very interesting topic. It looks very similar to a bivalve’s foot, a bulky, muscular structure that allows it to burrow itself into the sand, among other things. However, though the foot is very conspicuous in most bivalve lineages, it is reduced in pectinids (Shumway & Parsons, 2011). At the same time, though they are never protruded, some of the animal’s organs such as the gonads are often visible from the outside in real world bivalves, and they can resemble a tongue hanging between open lips. We do, however, prefer to think of Shellder’s tongue as a foot for obvious reasons. Pectinids usually don’t grow up to the huge proportions of 0.3 m and 4 kg informed by the Pokédex, but other real-world clams can become even larger (see Cloyster below).


(#091; Type: Water / Ice)


Class: Bivalvia (bivalves)

Order: Pectinida (scallops and oysters)

Family: Spondylidae (thorny oysters)

Genus: Spondylus Linnaeus, 1758

A rather fierce-looking version of its pre-evolved state, Cloyster sports a larger, thicker and rougher shell, complete with spikes/thorns, which are typical features of the bivalve family Spondylidae. Commonly known as thorny or spiky oysters (they are not part of the so-called “true oysters”, which belong to the family Ostreidae), spondylids are close relatives of the common scallops (Matsumoto & Hayami, 2000). Among many other striking morphological characters, such as their many eyes spread along the animal’s mantle, pectinids and spondylids share an overall similar shell outline but the latter are usually bulkier and spikier.

As for being bulkier, Cloyster is many times larger and heavier than Shellder, spanning up to 1.5 m wide and weighing over 130 kg, a size unattainable for any real-world spondylid, but still not entirely fictional: some bivalves in the family Tridacnidae (a.k.a. giant clams) can weight over 200 kg (Knop, 1996). Nevertheless, even though spondylids certainly do not grow to such humongous proportions, the increased size and the prominent, more numerous spikes make up for a more menacing and stronger version of the childly-looking Shellder, with a malicious look as a bonus.

Top: Spondylus regius Linnaeus, 1758 (D. Descouens, 2009). Bottom: Spondylus sp. (F. Ducarme, 2018).

The attacks are all very similar to Shellder’s, with the addition of a “Spike Cannon” move (yet another reference to the thorny Spondylus shells). Likewise, if Shellder is based on pectinids and Cloyster on spondylids, the “close” relationship between the two Pokémon thus elegantly (though hardly intentionally) reflects their real-world kinship.

Of course, spondylids are not the only spiky bivalves out there. The Japanese spiky oyster, Saccostraea kegaki Torigo & Inaba, 1981 (family Ostreidae), for example, also has a spiky shell that seems quite uninviting to the touch. But spikes aside, it lacks some other traits observable in Cloyster that indicates it was probably inspired by real-world spondylids, e.g., the bulkier shell. Besides, true oysters have very variable shape, not very similar to Cloyster’s symmetrical, scallop-like profile. Its shell also includes wing-like or ear-like projections located at the rear (called auricles), which also appear in some spondylid species (Shumway & Parsons, 2011).


(#138; Type: Rock / Water)

Class: Cephalopoda (squid, octopuses and nautiluses)

Subclass: Ammonoidea (ammonoids)

Omanyte and its evolved form, Omastar (see below), are based on a generalized ammonoid. Ammonoids[1] are cephalopod mollusks who once crowded the seas, with an astounding diversity of species. Unfortunately, they went extinct together with non-avian dinosaurs during the great extinction event in the end of the Cretaceous period. True to its roots, Omanyte is not found alive in the game: it is found as a fossil (called “Helix Fossil”) on a rocky matrix. The player must then “resurrect” it in a very Jurassic Park manner. As all fossils in the Pokémon franchise, Omanyte and Omastar are Rock-type. On a side note, the Helix Fossil recently spun its own mythology on Twitch Plays Pokémon, where it acted as a sort of oracle to the players (for the whole story, see Salvador, 2014).

Despite being very similar to a real ammonoid fossil, Omanyte bears a huge flaw in its design. The soft body is positioned in an inverted manner in relation to the shell. That is, Omanyte’s body is positioned like the body of a snail (a gastropod), rather than like the body of a cephalopod (Salvador, 2014). Omanyte is depicted with 10 arms, but the real numbers an ammonoid would actually have is unknown because other living cephalopods have a variable number (Monks & Palmer, 2002): nautiluses have 50 to 90 arms, squids and cuttlefish have 10 (two of which are called tentacles) and octopuses have 8.

Top: Asteroceras sp. (Daderot, 2012). Bottom: Reconstruction of Asteroceras sp. (N. Tamura, 2009).

Omanyte can have the ability called “Shell Armor” (see above), which makes sense, and can learn the move “Withdraw”. Although no living ammonoid exists, they were thought to be able to withdraw into their shells for protection like their present-day “cousins”, the nautiluses (Monks & Palmer, 2002). It can also learn the move “Shell Smash”, which does not make sense: why would a mollusk break its only means of protection?


(#139; Type: Rock / Water)

Class: Cephalopoda (squids, octopuses and nautiluses)

Subclass: Ammonoidea (ammonoids)

Omastar is very similar in design to Omanyte (even retaining the gastropod-like position of the body), with a few important differences. (1) Beak: Omastar has a tetrapartite beak. Living cephalopods have a parrot-like beak made up of two interlocking jaws, and ammonoids thus probably also had a beak (Engeser, 1996; Monks & Palmer, 2002). We say “probably”, because features of the soft body hardly ever are preserved in the fossil record. In any case, a beak made up of four parts such as Omastar’s is a bit of an overkill.

(2) Spikes: Omastar’s shell is lined with spikes. It can learn the move “Spike Cannon”, which means it supposedly can shoot them as projectiles. Needless to say, ammonoids species that were ornamented with spikes (for instance, Apoderoceras spp. and Euhoplites spp.) would not be able to do that. Even so, the function of shell spikes in ammonoids is thought to be defensive, to discourage potential predators of taking a bite (Ward, 1981; Monks & Palmer, 2002).

(3) Size: while Omanyte measures 0.4 m and weighs 7.5 kg, Omastar reaches 100 cm and 35 kg. Of course, every player worth their salt knows that these Pokédex entries are just plain crazy, but it can serve here to illustrate how awesome ammonoids were. A 1 m high Omastar might seem too large to be possible, but one ammonoid species could reach up to 2 m in shell diameter (estimated 2.5 m or even 3.5 m if the largest known fossil was complete; Teichert & Kummel, 1960). This species is called Parapuzosia seppenradensis (Landois, 1895) and is known from the Cretaceous Period of Germany. Its shell is estimated to have weighed circa 750 kg in life and this value would increase to 1,400 kg with the animal’s soft body (Teichert & Kummel, 1960).

Euhoplites armatus Spath, 1928 (courtesy J.-S. David;

Curiously, Bulbapedia states that the shell of Omastar was too heavy to move and this led to the species extinction (they died out from starvation). This type of view about extinction, which supposes that the animals were somehow inept and unable to survive, is completely outdated – not to say completely ridiculous. The same story was told long ago about the extinction of the “slumbering dinosaurs”, but this is now known to be false. Extinction can have many causes, including environmental changes, competition with other species, predation, calamitous events, and, of course, irresponsible humans.


(#218; Type: Fire)

Class: Gastropoda (snails and slugs)

Superorder: Eupulmonata (pulmonate snails and slugs)

Order: Stylommatophora (terrestrial snails and slugs)

Slugma was clearly based on slugs, but not on any particular species: rather, its design is broadly generalized. The superorder Eupulmonata (earlier known as order Pulmonata) within the gastropods contain the highest diversity of terrestrial forms (over 20,000 species of land snails and slugs; Rosenberg, 2014). The “slug” body shape is a modification of the typical snail body in which the members of the lineage go through shell reduction, shell internalization (it becomes a small piece within the animal’s body) and sometimes the complete loss of the shell (Barker, 2001). This process, called “limacization” (or “transformation-into-a-slug”), happened separately several times within Eupulmonata, in many distinct families (Veronicellidae, Rathouisiidae, Arionidae, Limacidae, etc.). Is it though that losing its shell increases the mobility of the animal and capacity to explore and hide in smaller spaces (Cameron, 2016). However, the absence of the shell means that the animal is more vulnerable to predators and to the worst enemy of terrestrial gastropods: evaporation.

Terrestrial gastropods have soft moist bodies and are constantly losing water to the environment by evaporation. A very large portion of these animals’ evolutionary history is related to mechanisms and strategies to decrease or avoid losing precious water (Barker, 2001). Also, slugs cannot be too large, because of water loss and the lack of a skeletal structure to sustain the body. Of course, the 0.7 m tall Slugma is basically a Dungeons & Dragons fire elemental, so water loss is not even in question.

Top: Arion rufus (Linnaeus, 1758) (H. Hillewaert, 2008). Bottom: Limax cf. dacampi Menegazzi, 1854 (Hectonichus, 2005).

Slugs are worm-like creatures that craw horizontally, but Slugma has a somewhat upright posture, with its head permanently reared up. Although slugs can sometimes strike such a pose (when trying to climb something, for instance), they do not spend their whole time nor do they move around like this.


(#219; Type: Fire / Rock)

Class: Gastropoda (snails and slugs)

Superorder: Eupulmonata (pulmonate snails and slugs)

Order: Stylommatophora (terrestrial snails and slugs)

The evolved form of the slug Pokémon Slugma is Magcargo, a snail. As explained above, biological evolution has always worked the other way around, with slug species arising within snail lineages. In any event, it is evident that “evolution” in Pokémon has absolutely nothing to do with biological reality – and we hope we do not need to explain here that it is impossible for an animal to transform into another after it has gained enough XP. That’d be cool, though.

Like Slugma, Magcargo has a generalized design but this time around, based on a snail. In fact, its name is a combination of the words magma and escargot (French for snail). Curiously, Magcargo has a planispiral shell, meaning that its shell is coiled on a single plane, resulting in a flat appearance. Planispiral shells are very rare in land snails, presumably because carrying a shell shaped like this on land is rather clumsy. However, planispiral shells are very common in freshwater snails, where the water helps to sustain it; there is a whole family with planispiral shells, aptly named Planorbidae (from the Superorder Hygrophila, the sister-group of Eupulmonata). Typically, the shells of land snails are more globose or more elongated. In any event, land snails carry their shell a little tilted to the side, not upright as Magcargo.

Top: Planorbarius corneus (Linnaeus, 1758) (C. Ableiter, 2007); Mid: Cepaea nemoralis (Linnaeus, 1758) (D.G.E. Robertson, 2008); Bottom: Drymaues papyraceus (Mawe, 1823) (courtesy of L. Charles).

Magcargo is huge for a snail, measuring 0.8 m in height and weighing 55 kg. As explained above for Slugma, this size would pose problems regarding water loss, but a more pressing issue is body weight: a snail cannot sustain such a heavy body on land, nor hold up and carry around a rock-like shell. The largest land snail species is the fossil Pebasiconcha immanis Wesselingh & Gittenberger, 1999 (from the Miocene of Colombia and Peru), but its shell is “lightweight” in comparison to Magcargo, reaching up to “meager” 26 cm in length (Wesselingh & Gittenberger, 1999).

Bulbapedia states that Magcargo could be based on the Cherufe, a volcano-dwelling creature from Argentinean and Chilean folklore. However, this is extremely unlikely for two reasons: (1) Cherufe is typically a gigantic humanoid monster, albeit with some dragon-like features such as a predilection for meals including young girls (Lurker, 1987; Rose, 2001), with no mention of molluscan features. (2) More to the point, the people responsible for Pokémon only rarely look outside of Japan (or Japanese zoos) for influences; for instance, even Generation VI, which is supposedly based on France, has a very Japanese fauna (Tomotani, 2014).


(#224; Type: Water)

Class: Cephalopoda (squids, octopuses and nautiluses)

Subclass: Coleoidea (octopuses, squids, and cuttlefish)

Order: Octopoda (octopuses)

Octillery has a generalized cartoon-octopus look and, thus, not much can be said about its morphology. However, there is one feature that is clearly mistaken (as in numerous other cases in Japanese games and anime/manga): the structure that is depicted as Octillery’s mouth is actually the funnel. To breathe, cephalopods bring water into a chamber inside their body called the “mantle cavity”, where the gills are located. Then, the water is expelled through the funnel; this can be done quietly or in a more powerful gush of water, enabling the animals to move by jet propulsion. The mouth of a cephalopod is located where all the arms meet, facing “downwards” and hidden from view, and the funnel is located laterally (not in front, like in Octillery).

While most octopuses are not very large, Octillery can reach a respectable size: 0.9 m high, weighing 28 kg, according to its Pokédex entry. The largest octopus alive is the giant Pacific octopus, Enteroctopus dofleini (Wülker, 1910). Large adults can reach 6 m in radial “arm span” and weigh about 50 kg, but some records increase the span to somewhere between 9 and 10 m (High, 1976; Hartis, 2011).

Enteroctopus dofleini (Wülker, 1910) (Bachrach44, 2008).

One of Octillery’s in-game abilities is called “Suction Cups”; its description says: “This Pokémon uses suction cups to stay in one spot to negate all moves and items that force switching out.” This is a very pertinent ability, as the arms of octopuses (and squids and cuttlefish) are covered with suction cups (also called “suckers”) on their inner surface. These suction cups are used in locomotion and to manipulate objects and prey. The cups are astonishingly strong, and the animals can control each of them independently.

Octillery’s signature move is called “Octazooka”, the description of which says: “The user attacks by spraying ink at the target’s face or eyes. This may also lower the target’s accuracy.” This is likewise a very pertinent move, as cephalopods are famous for their ability to squirt dark ink. These animals have an organ called “ink sac” and can expel the ink lodged inside it – through the funnel – as a dark smoke-screen-like cloud. When cephalopods are attacked, this strategy confuses the predator and allows them to escape (Sato et al., 2016). Moreover, recent studies suggest that ink clouds may also be used to confuse prey, allowing a sneak attack bonus (Sato et al., 2016).

As a last note, Octillery is the evolution of Remoraid, which is a remora, a type of fish (Mendes et al., 2017). Again, we know that “evolution” in Pokémon bears no resemblance to biological reality, but this might be taking the craziness a tad bit too far.[2]


(#366; Type: Water)

Class: Bivalvia (bivalves)

Order: Heterodonta

Family: Tridacnidae (giant clams)

Genus: Tridacna Bruguière, 1797

Species: Tridacna gigas (Linnaeus, 1758) + fish egg of an unknown species

Appearances can often be deceiving in the Pokémon world. Though Clamperl may look like and is certainly named after a mollusk, the pinkish “pearl” inside its shell is actually a fish egg – or rather, roe. Roes are egg masses of fish and certain marine animals, such as urchins, shrimp, and even scallops. Even though some mollusks produce eggs, both of Clamperl’s evolved forms, Huntail and Gorebyss, are actually fish-like Pokémon (Mendes et al., 2017), which clarifies its true nature . This pink egg rests on what seems to be a soft, bluish pillow with stubby projections. It is as if a random giant clam is offering its body as protection for the fish egg – and so, Clamperl is actually composed of two different organisms in association – or symbiosis, if you may. In fact, this is not unheard of in the Pokémon franchise, and some cases also involve mollusk-inspired Pokémon (we’re looking at you, Slowbro and Slowking).

Nevertheless, its shell seems to be based on real-world giant clams, a.k.a. bivalves in the family Tridacnidae and genus Tridacna. Its overall size and weight (0.4 m and 52 kg) are also not out of this world: as we mentioned before, species such as Tridacna gigas (Linnaeus, 1758) are huge and can measure as much as 137 cm and weight 230 kg (Knop, 1996). Clamperl’s abilities and attacks also refer to and reinforce the relevance of its shell: Shell Armor, Shell Smash, and, of course, the signature attack Clamp.

Tridacna gigas (Linnaeus, 1758) (Liné1, 2008).

Curiously, getting a leg or arm clamped by a giant clam is actually the stuff of legend: giant clams were called “killer clams” and “man-eating clams” in the past due to having allegedly drowned divers that got stuck between their valves (each individual piece of a bivalve shell is a valve). This rumor probably originated in Wilburn Dowell Cobb’s romanticized article on the discovery of the “Pearl of Allah” (or Pearl of Lao Tzu) published on the Natural History magazine in 1939. One of the largest pearls ever found, with 24 cm in length and weighing ca. 6.4 kg, it was retrieved from a giant clam that, according to Cobb’s (1939) dramatic description, ended up “slaying a native diver trapped when its great jaws snapped shut”. And by jaws, he probably meant the valves. Cobb went as far as calling the clam a “deep sea murderer”.

Both things are strictly wrong: giant clams are not a deep-sea species, nor murderers of any kind: they have a symbiotic relationship with algae, which use sunlight (not present in the deep sea) to synthesize their food supply. Influenced by such dramatic descriptions, even scientific and technical manuals once claimed that clams had caused deaths, and even gave instructions on how to release yourself if you were stuck. Nowadays, we know this reputation is rather underserved: not a single human death by giant clam has ever been reported (scientifically, that is). Moreover, the adductor muscles in giant clams, which are responsible for closing their shells, move rather slowly (Fredericks, 2014). Hence real-world clams are, in fact, quite gentle giants.


(#422: Type: Water)

Class: Gastropoda (snails and slugs)

Order: Nudibranchia (sea slugs)

Family: Chromodorididae

Genus: Chromodoris Alder & Hancock, 1855 and Hypselodoris Stimpson, 1855

Nudibranchia is a peculiar group within the Opisthobranchia, a.k.a. the sea slugs. Well-known because of their vivid colors and extravagant forms, nudibranchs (or nudis, if you wish) are among the most beautiful and popular sea creatures out there. They live pretty much everywhere, inhabiting the seas worldwide from arctic to temperate and tropical regions (but unlike Shellos, definitely not on land). Shellos’s design seems to be clearly based on nudis – it has a long and somewhat flat, colorful body, with flappy lateral expansions, and the head appendages are very similar to rhinophores, which are characteristic sensory structures of nudibranchs. The color patterns are very similar to nudibranchs belonging to the family Chromodorididae found in Japan such as Chromodoris lochi Rudman, 1982, Hypselodoris festiva (A. Adams, 1861), and Hypselodoris apolegma (Yonow, 2001). Moreover, Shellos’s proportions (0.3 m and 6.4 kg) are actually not exaggerated: nudibranch species such as Hexabranchus sanguineus (Ruppell & Leuckart, 1828) can grow as long as 52 cm (Double, 1992).

Top: Chromodoris lochi Rudman, 1982 (A.R. Jenner, 2009). Bottom: Hypselodoris apolegma (Yonow, 2001) (C. Ordelheide 2011).

Remarkably, Shellos was one of the first attempts of the franchise at introducing the concept of regional variants back in Pokémon Diamond and Pearl (Gen IV) in 2006–2007. This would become a central theme in Pokémon Sun and Moon (Gen VII), ten years later. Nevertheless, back then, Shellos presented two forms corresponding to two distinct regions: the blue form inhabits the East Sea, and its pink “cousin” lives in the West Sea. This is clearly a nod to the phenomenon of geographic (a.k.a. allopatric) speciation: it happens when populations of the same species become isolated due to geographical barriers, forming two or more new populations that evolve independently in different forms.

One curious thing about Shellos (and its evolution Gastrodon, see below) is the fact that it can learn some pretty nasty poison abilities, even though it is not a Poison-type Pokémon. In the real world, some nudibranchs store toxins and other unpleasant or harmful substances/structures they get from other organisms they feed on such as algae, anemones, and coral. They effectively use these substances as a defense mechanism. Sometimes, their striking colors, which may be especially vivid in the parts of the body where the harmful substances are stored, serve as a warning for visually oriented predators: a phenomenon known as aposematism (Aguado & Marin, 2007). As pretty as Shellos may look, its bright colors could signal danger.


(#423; Type: Water / Ground)

Class: Gastropoda (snails and slugs)

Order: Nudibranchia (sea slugs)

Family: Chromodorididae

Genus: Chromodoris Alder & Hancock, 1855 and Hypselodoris Stimpson, 1855 (and maybe Aplysia Linnaeus, 1767)

Much like its pre-evolution Shellos, Gastrodon’s design is largely based on nudibranchs or other related marine slugs. Our considerations about Shellos also apply to Gastrodon, with a few exceptions. Gastrodon is quite larger than Shellos, measuring as long as 90 cm and weighing up to 30 kg. This is way too large for real-world nudibranchs, but not entirely disproportionate: a species of sea hare, Aplysia vaccaria Winkler, 1955 can measure up to 99 cm long and attain a total weight of 14 kg (Behrens, 1992).

Top: Chromodoris willani Rudman, 1982 (J. Tanaka, 2006). Bottom: Aplysia californica (Cooper, 1863)(C. King, 2011).

In fact, Bulbapedia claims the East Sea variant of Gastrodon was designed after sea hares. Nevertheless, sea hares are not nudibranchs but belong to a group called Anaspidea, one of the many lineages within the Heterobranchia, a natural group of gastropods that also includes Nudibranchia. You could think of them as distantly related “cousins”. In any event, the design of East Sea Gastrodon is only remotely alike sea hares and much more closely resembles chromodoridid nudibranchs, being very similar to the species Chromodoris willani Rudman, 1982, from the Western Pacific.


(#489; Type: Water)

Class: Gastropoda (snails and slugs)

Order: Pteropoda (sea butterflies)

Suborder: Gymnosomata (sea angels)

Family: Clionidae

Genus: Clione Pallas, 1774

Species: Clione limacina (Phipps, 1774)

The so-called sea angels are actually free swimming (pelagic) sea slugs scientist collectively call Gymnosomata (from the Greek, meaning “naked body”, a direct reference to their shell-less bodies). They belong to a group called Pteropoda, the sea butterflies, which means “wing-foot”. Pteropods use their wing-like flaps, known as parapodia, to swim about searching for prey. Yes, prey: they are voracious predators of planktonic invertebrates, including other pteropods (Hermans & Satterlie, 1992). While most pteropods have shells, the lineage of the Gymnosomata lost it during its evolution.

Elegant and somehow intimidating (if you’re just small enough), sea angels in the genus Clione, especially Clione limacina found in Hokkaido, are quite popular in Japan (Hutcheon, 2010). The in-game region Sinnoh is reportedly based on Hokkaido, which makes Clione limacina the obvious inspiration for Phione. Even their names are almost the same.

Clione limacina (Phipps, 1774) (NOAA, 2005).

It is no surprise that Phione, the single mythical[3] molluscan Pokémon alongside Manaphy, was based on sea angels, whose name is already kind of mythical. Measuring 40 cm long (weight ~4 kg) according to the Pokédex, it is a little too large for a sea angel: they never grow past a few centimeters. However, even though it is somewhat stylized, Phione’s (as much as Manaphy’s) appearance is that of a sea angel with the signature wing-like parapodia, a well-marked head, and tail-like body. We can see some attention to detail has been paid, as the red gem on Phione’s “chest” resembles the large, reddish-orange digestive gland seen in sea angels, which is roughly located at the same place in the real-world slug bodies (although internally, of course).


(#490; Type: Water)

Class: Gastropoda (snails and slugs)

Order: Pteropoda (sea butterflies)

Suborder: Gymnosomata (sea angels)

Family: Clionidae

Genus: Clione Pallas, 1774

Species: Clione limacina (Phipps, 1774)

Manaphy is very similar in appearance to Phione and should also have been inspired by Clione limacina. So pretty much everything that was said about Phione also applies to Manaphy.

One thing tough, is the “Tail Glow” move: “The user stares at flashing lights to focus its mind, drastically raising its Sp. Atk stat.” This move is a possible nod to the phenomenon of bioluminescence, which consists on the production and emission of light by living organisms. Although widespread among marine invertebrates, like jellyfish, bioluminescence is known from very few nudibranchs: just the genus Plocamopherus Rüppell & Leuckart, 1831 and the species Phylliroe bucephalum Peron & Lesueur, 1810 (Herring, 1987; Lalli & Gilmer 1989; Haddock et al., 2010). Bioluminescence has never been documented in Clione.


(#616; Type: Bug)

Class: Cephalopoda (squid, octopuses and nautiluses)

Order: Nautilida (nautiluses)

Family: Nautilidae

Genus: Nautilus Linnaeus, 1758 or Allonautilus Ward & Saunders, 1997

With a very characteristic spiral shell-like armor, Shelmet is at least partly based on cephalopods, more specifically those in the family Nautilidae, like the living genera Nautilus and Allonautilus. As tragic as it may sound, the three living nautilus species are the only survivors of a once thriving group (Dunstan et al., 2011). The fossil record shows us that nautiluses were much more diverse and a multitude of genera existed a few hundred million years ago. This diversity suffered its ups and downs, with a strong decline in the Miocene (roughly 23 to 5 million years ago) and Pliocene (5 to 2.5 million years ago), and most lineages did not survive to this day.

Nautilus sp. (J. Baecker, 2007).

Nevertheless, Shelmet is very akin to living nautiluses, starting with the shell: it is tubular and coiled in a single horizontal plane (planispiral), and bears a triangular knight’s helmet visor that is very similar to the hood nautilids have (also called aptychus). The position of the body in relation to the shell is correct in Shelmet, contrary to Omanyte/Omastar seen above (nautiloids and ammonoids are closely related, sharing a basic body plan).

The angry cartoonish eyes with vertical pupils also appear to have been inspired by real-world nautilid eyes. The vertical pupils are, in fact, holes: nautiluses have pinhole eyes which lack the solid lens that squid and octopuses (as well as humans) have. Shellmet’s funny looking puckered-up mouth is also reminiscent of the real animal’s funnel (hyponome), even though the real-world structure is used for propulsion, and not for kissing. On the other hand, Shelmet lacks the numerous small, smooth tentacles (called cirri) that are very striking in the real-world nautilids – our guess is that they would probably make the design messy or simply too hard to draw/animate.

At 0.4 m length and 7.7 kg, Shelmet is also way larger than any living nautilid species, which reach up to 0.25 m in width at most (Pisor, 2008). Extinct species of the family Endoceratidae (of uncoiled nautiloids) though, might have reached more than 3 m in shell length (Flower, 1955; Teichert & Kummel, 1960; Teichert, 1964; Frey, 1995).

Naturally, Shelmet has the ability “Shell Armor” and this is rather literal for this Pokémon: its shell was clearly inspired by the armors of medieval knights, as can be seen by its visor and its evolution. Shelmet’s evolution is very complicated in-game: when traded with Karrablast, Shelmet evolves into Escavalier, which looks like a bug wearing Shelmet’s shell and “visor” (or perhaps a hermit crab?). Meanwhile, Karrablast evolves into Accelgor, which looks like an insect pupa with a slightly coiled (shell-like) head. This mix-up of insectoid features explains why Shelmet is a Bug type. In any case, any mollusk resemblance is (sadly) lost in the evolutions, so we won’t consider them here.


(#686; Type: Dark /Psychic)

Class: Cephalopoda (squid, octopuses and nautiluses)

Subclass: Coleoidea (octopuses, squids, and cuttlefish)

Order: Teuthida (squids) or Sepiida (cuttlefish)

Inkay seems to be a very stylized teuthid or sepiid cephalopod: respectively a squid or a cuttlefish. We do believe it is more of a squid than a cuttlefish, however: Inkay has a very characteristic squid-like figure, with a triangular body (mantle), a somewhat discernible head, arms and stylized tentacles. Moreover, the tentacles of real-world cuttlefish, are “hidden” inside the 8 arms, which is not the case of Inkay – like real-world squids, the tentacles are showing, though their lateral position is odd (they are centralized in real-world squids).

The size informed by the Pokédex is well within the real-world range at 0.4 m length and weighing up to 3.5 kg. Squids can go from millimeters to several meters long: the giant squid, Architeuthis dux Steenstrup, 1857, can reach 18 m (Clarke, 1966; Roeleveld & Lipinski, 1991; Salvador & Tomotani, 2014), while the colossal squid, Mesonychoteuthis hamiltoni Robson, 1925, can weigh whopping 500 kg (Salvador, 2019).

The designers deserve some praise for actually making the mouth look like a beak for this Pokémon, like in real-world cephalopods. Unfortunately, they put it on the wrong place. Real-world cephalopods have their mouth (and beak) sheltered in the middle of the arms and tentacles.

Top: Loligo vulgaris Lamarck, 1798 (H. Hillewaert, 2005). Bottom: Sepia officinalis Linnaeus, 1758 (J. Carvalho, 2006).

Inkay’s abilities and moves were also clearly inspired by cephalopod biology. The “Suction Cups” ability is a nod to cephalopod suckers (see Octillery above), which are normally arranged in rows along their arms and at the tip of their tentacles (for differences between arms and tentacles, see Salvador & Cunha, 2016). Though the move “Constrict” may seem logical at first sight, it is actually erroneous: contrary to popular myth, cephalopods cannot constrict something with their tentacles as if they were snakes (Roper & Boss, 1982). The move “Peck” is a reference to a cephalopod beak, although they cannot peck their prey like birds would. Rather, they use the beak to tear small chunks of their prey.

The move “Hypnosis” employs hypnotic suggestion to make the target fall into a deep sleep. This is a reference to real-world cuttlefish. Coleoid cephalopods can change their body color and color patterns using specialized skin cells called cromatophores. They can change color almost instantly and can produce patterns as if their skin were a TV screen.[4] The animals use this ability to camouflage[5] themselves (either to evade predators or to ambush prey), to communicate with their kin, or to scare off predators (Hanlon & Messenger, 1996; Hanlon, 2007; Mäthger et al., 2012). However, some scientists suggest a fourth kind of use for the color-changing ability: the patterns produced would mesmerize prey and make them easier to catch, which could be interpreted as a kind of hypnosis (Mauris, 1989; Mather & Mather, 2006; Thomas & MacDonald, 2016). This ability in real cephalopods, however, remain far from proven.


(#687; Type: Dark / Psychic)

Class: Cephalopoda (squid, octopuses and nautiluses)

Subclass: Coleoidea (octopuses, squids, and cuttlefish)

Order: Teuthida (squids)

More so than Inkay, Malamar’s design is clearly based on a squid, with an elongated body with triangular wing-like fins, and two long well-defined tentacles. The fierce, evil look is just a bonus. Oddly though, Malamar is basically upside down. Real-world squids do not swim in this position; they are usually horizontally or vertically oriented with the arms and tentacles pointing downward. However, some squids (e.g., family Cranchiidae) do remain on this upside-down position with the arms held upwards: this is known to scientists as the “cockatoo position.” This inversion in position is linked to the way Inkay evolves into Malamar: the player must hold the Nintendo 3DS system upside-down for Inkay to evolve.

In any case, everything else that was said about Inkay applies to Malamar, including the moves/abilities (which are identical), the beak-like mouth (and its odd placement), and the size range (1.5 m, 47 kg; respectable, but much smaller than some real-world squids).


(#704; Type: Dragon)

Class: Gastropoda (snails and slugs)

Order: Nudibranchia (sea slugs)

Family: Chromodorididae

Genus: Goniobranchus Pease, 1866

Goomy is yet another Pokémon probably designed after sea slugs[6] (most likely Nudibranchia), though it is neither a Water-type nor marine. Goomy’s “antennae” are very similar to structures of sea slugs called rhinophores, which are scent or taste receptors (chemosensory structures) situated on the dorsal surface of the animal’s head (Wertz et al., 2007; Cummins et al., 2009). The overall shape of its body is a very generic design of a sluggish creature, and the color pattern is somewhat reminiscent of species such as Goniobranchus kuniei (Pruvot-Fol, 1930) or Goniobranchus geminus (Rudman, 1987).

Interestingly, Goomy (and its evolved forms) are Dragon-type Pokémon. This is a possible reference to the so-called blue dragon sea slug, Glaucus atlanticus Forster, 1777, though the design is not even vaguely similar to it. Goomy’s size (0.3 m, 2.8 kg) is well within that of real-world sea slugs (see Gastrodon’s entry above).

Goniobranchus kuniei (Pruvot-Fol, 1930) (S. Childs, 2006).

Goomy’s abilities are clearly inspired by mollusk physiology. The “Gooey” ability lowers the attacker’s Speed stat upon contact, a nod to the mucus production that is typical of snails and slugs, but usually more conspicuous in terrestrial species (Cameron, 2016). Despite being based on sea slugs, Goomy is fully terrestrial and accordingly gooey. “Hydration” is an ability that heals status conditions when it’s raining. Conserving water in terrestrial environments is hard for moist-bodied creatures like snails and slugs and a good deal of their evolutionary history has to do with this (Barker, 2001). The relationship between snails/slugs and the rain is very clear, as they will be found out and about after a good rain.


(#705; Type: Dragon)

Class: Gastropoda (snails and slugs)

Superorder: Eupulmonata (pulmonate snails and slugs)

Order: Stylommatophora or Ellobiida

Contrary to Goomy, Sliggoo seems fully based on a terrestrial snail, though it retains some of the characteristics of sea slugs (e.g., the “rhinophores” on the dorsal surface of the head) and is thus, kind of a gestalt. These rhinophores, however, can now also be interpreted as the sensory tentacles of land snails. If that is the case, we can see that Sliggoo’s eyes are positioned on the base of the tentacles. Most eupulmonates have the eyes on top of the eyestalks (order Stylommatophora), with only a few (order Ellobiida) having eyes on the base of the stalks. However, no ellobiid is known to be semi-slug or slug-like, as Sliggoo is (see below). Once again, this Pokémon seems to be a mixture of forms.

Top: Eucobresia diaphana (Draparnaud, 1805) (J. Grego, 2004; Bottom: Omalonyx convexus (Heynemann, 1868) (courtesy of L. Charles).

Sliggoo has a spiral “hump” of sorts, which resembles a vestigial shell found in the so-called semi-slugs. These gastropods are, so to speak, halfway through the process of limacization.

The name seems to be derived from words such as slippery, slimy and goo, which is yet another reference to the mucus produced by mollusks in general. In any case, compared to real-world snails and slugs, its erect posture is wrong (see Slugma above). Likewise, its large size (0.8 m, 17.5 kg) is problematic (see Magcargo and Goomy above). Sadly, Sliggoo does not become a slug or a snail later on: it evolves into Goodra, which completely loses its resemblance to mollusks, looking more like a cartoonish dragon/dinosaur creature. It is still slimy, though.


There is one Pokémon that is not a mollusk, but which deserves a brief mention here: Dwebble (#557; Type Bug / Rock). This Pokémon is based on a hermit crab. This group of crustaceans, the superfamily Paguroidea, is typically marine, although there are some terrestrial forms (Dwebble itself is terrestrial). Hermit crabs are remarkable for using the empty shells of gastropods as protection: they choose their shell carefully, carry them around and change shells when they grow and/or when they find a better one.

Dwebble, however, does not use a gastropod shell; it uses a piece of rock. Curiously, some terrestrial hermit crabs use fossilized gastropod shells (Haas, 1950) and that is as close to a rock as one can get. Dwebble, though, does not have that many options: the only gastropod shell available to it would be that of a Magcargo, which is way too large. Other options would be the shells of the ammonoid-Pokémon Omanyte/Omastar, but they are fossils that need to be “resurrected”, which would make Dwebble’s life much more difficult. Although hermit crabs using ammonoid shells may sound strange, there is evidence that fossil hermit crabs from the early Cretaceous period (circa 130 million years ago) actually used them (Fraaije, 2003).

On a similar case, there is a report of a hermit crab, called Diogenes heteropsammicola Igawa & Kato, 2017, using a coral instead of a shell. This species lives in southern Japan (Igawa & Kato, 2017) and it actually looks rather similar to Dweeble. That, however, would be a large coincidence, as this species was only discovered after Gen V had been released.

Diogenes heteropsammicola (Igawa & Kato, 2017).

Awkwardly, Dweeble is called “Rock Inn Pokémon” and that’s likely because the official “Hermit Crab Pokémon” is Slowbro (#080; Type Water / Psychic), from Gen I.

The problem is, Slowbro is not a crab: its design is clearly based on a mammal. It does have a shell-like structure attached to its tail, though, which is (according to lore) a living Shellder. There are some further problems with this: first, that “Shellder” is still alive, so it would be a case of symbiosis, not of a crab using an empty shell. Secondly, the “Shellder” is now arranged spirally, like if he transformed from a bivalve into a gastropod. However, if one looks closely, the shell is not actually a spiral, but just a hollowed-out structure that looks like a chocolate cornet. In fact, the cornet-thing has a pair of angry eyes, so it is definitely neither a shell nor a mollusk. Thus, Slowbro is just a pile up of mistakes: a crab that’s a mammal carrying a mollusk that’s at best a sentient pastry.[7]

Cornet (Ayy753771, 2017; Cooking Mama Wiki).


There is one notable rea-life mollusk whose name was inspired by Pokémon – its popular name, at least. The “Pikachu slug” is a nudibranch from the Indian Ocean and Western Pacific that got the attention of the Japanese public on the Internet. It is a tiny yellow/orange-ish creature with black tips on its rhinophores and gills. It is virtually impossible not to think of Pikachu when looking at it. Even though its popularity is quite recent, the species was discovered and described in the late 19th century; its scientific name is Thecacera pacifica Bergh, 1883 (family Polyceridae).

Thecacera pacifica (Olakhalaf, 2017).


Most of the Pokémon designs are in line with real-world mollusks, although there are some cringeworthy mistakes, like Omanyte/Omastar’s body position, Octillery’s mouth/funnel controversy, and Inkay/Malamar’s beak position. The moves and abilities nicely reflect some mollusk features and, well, abilities, but there is also some crazy stuff added on the mix, like “Shell Smash” and “Spike Cannon”.

As we highlighted in the beginning of this article, there are between 70,000 and 200,000 species of mollusks (Rosenberg, 2014). In comparison, there are only circa 6,000 species of mammals (Burgin et al., 2018). Overall, there are 17 molluscan Pokémon among the current 809 monsters. This number clearly does not reflect true animal biodiversity, similar to other misrepresented invertebrates in the franchise, such as arthropods (Prado & Almeida, 2017; Kittel, 2018). Obviously, people prefer to see cats and doggos so there are plenty of Pokémon based on them, domestic or otherwise. Even so, there are some animal groups, mollusks or otherwise, that deserve better representation in Pokémon, such as velvet worms (Onychophora) and bristle worms (Polychaeta). They would make much more interesting monsters than yet another lion.


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Dr. Rodrigo Salvador is a zoologist and paleontologist who specializes in mollusks. Land snails are his favorites, but when it comes to Pokémon, he sticks with a sea slug instead: the West Sea Gastrodon. Even so, he walked 45 km with his Fire-type buddy Slugma in Pokémon Go (when it was still rare) so it could evolve.

Daniel Cavallari is a taxonomist and marine biologist who loves mollusks and their shells. He’s been collecting seashells and playing Pokémon games since he was a small boy. Though he prefers Pokémon of the older generations (I–III), he finds the newest mollusk-based Pokémon really amazing.

[1] In common parlance, they are knows as “ammonites”, but from a more strict scientific perspective, ammonites (order Ammonitida) is a smaller group inside the ammonoids (subclass Ammonoidea).

[2] Recently, some of the preliminary sprites for Gen II were found by dataminers (, showing that proto-Remoraid was a gun-shaped Pokémon and proto-Octillery was a tank-shaped Pokémon. We had a really hard time deciding which option makes less sense and ended up abandoning this question.

[3] The mythical status of Phione is highly debated within the community – yes, those are debates that actually happen – since official sources are ambiguous and contraditory (see Bulbapedia for more info). Manaphy, on the other hand (or should we say foot?), is indeed mythical.

[4] Shamefully, neither Inkay/Malamar nor Octillery have the ability “Color Change”. The only Pokémon with this ability is Kecleon, which is based on a chameleon. Just for the record, a chameleons’ ability to change color is laughable when compared to cephalopods.

[5] Even though octopuses are the masters of camouflage, Octillery does not learn the move “Camouflage”. Inkay, however, can learn it through the intricate (and rather annoying) process of Pokémon breeding.

[6] Bulbapedia indicates the fossil Wiwaxia Walcott, 1911 as a possible inspiration. However, there are very strong arguments against this: (1) These fossils are widely unknown. If Pokémon designers can’t even place the mouth of an octopus in the right place (see Octillery, Inkay and Malamar), they likely didn’t know about this animal. (2) Wiwaxiids might not actually be mollusks; their position in the tree of life is still hotly debated by scientists. All of Goomy’s abilities, Pokédex entries, moves, etc. point towards a mollusk. (3) The morphology is completely different: wiwaxiids were covered by hard plates and spines, like a medieval-looking tank. Likely no soft portion of their body was visible from the outside. Goomy is all soft and cute.

[7] If you think sentient desserts are to wacky, even for Pokémon, please refer to Vanillite, Vanillish, Vanilluxe, Swirlix, and Slurpuff.

Check other articles from this volume


You’re an oegopsid now: the phylogeny of squid kids from the future

Henry N. Thomas

University of California, Berkeley, CA, U.S.A.

Email: h.thomas (at) berkeley (dot) edu

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The main characters of Nintendo’s 2015 video game Splatoon and its 2017 sequel Splatoon 2 are Inklings, a species of sapient cephalopod with the ability to transform between a humanoid form and a more traditional coleoid form. Also present are the Octarians: octopus descendants that take the role of enemies. Since the release of the Octo Expansion for Splatoon 2, the Octoling, a subspecies of Octarian with similar appearance and abilities to Inklings, has become playable. Both Inklings and Octolings are hyper-evolved descendants of modern cephalopods, having evolved after sea level rise drives humanity to extinction 12,000 years in the future.

Figure 1. Comparison between the cephalopods of Splatoon and real cephalopods. Clockwise from top left: an Inkling in squid form; a female Inkling in humanoid form; a male Octoling in humanoid form; an Octoling in octopus form; Ommastrephes bartramii; Todarodes pacificus; Octopus vulgaris; Abralia veranyi; Thysanoteuthis rhombus. (Inklings’ and Octolings’ official renders are a courtesy of Nintendo; other images are public domain, retrieved from Wikimedia Commons.)

Exactly which cephalopods Inklings and Octolings descended from is unknown. In-game lore posits that Inklings are descended from squids and Octolings are descended from octopuses. A previous article covering the cephalopods of Splatoon has suggested links to Ommastrephidae or Thysanoteuthidae for Inklings (Salvador & Cunha, 2016). Here, I set out to resolve the relationships of these cephalopods with phylogenetic analysis.

Usually, scientists would use molecular data, i.e., DNA or protein sequences, to determine relationships among recent taxa. There have been numerous recent studies on the relationships of coleoid cephalopods based on molecular data (e.g., Sanchez et al., 2018). However, since video game characters have no DNA, this cannot be applied here. Thus, only morphological and behavioral data can be used. Luckily, there have been morphological phylogenies of cephalopods in the past to build off of.


To answer this question that nobody was really asking, I constructed a morphological dataset of cephalopods. This combines four previously-published morphological datasets (Young & Vechione, 1996; Voight, 1997; Lindgren et al., 2004; Sutton et al., 2016), as well as additional characters. I also added Inklings, Octolings, and nine extant squid genera to the dataset (Table 1): Dosidicus, Eucleoteuthis, Hyaloteuthis, Lampdioteuthis, Lycoteuthis, Mesonychoteuthis, Todarodes, Todaropsis, and Watasenia. “Palaeoctopus pelagicus” was removed because it isn’t a cephalopod at all, but fragments of a fossil coelacanth (Schultze et al., 2010).

Table 1: List of OTUs and sources of data. Extinct taxa are denoted by the symbol (†) before the species name. New data is marked in bold. Note that inklings and octolings are fictional taxa.

A few species in the same genera were lumped due to either having identical codings or in the name of having more complete Operational Taxonomic Units, or OTUs (several were coded in one dataset and not the others). Most Octarians have highly unorthodox morphology compared to Inklings or Octolings, and were excluded because how do you code a tentacle with a face? The resulting dataset has 283 characters and 139 OTUs.

I ran analyses in TNT (Goboloff & Catalano, 2016) using equal weighting methodology for 2000 replicates, producing 10 trees each. I ran one analysis with no constraints and one with a “molecular backbone” – forcing the analysis to fit a certain topology corresponding to what molecular phylogenies tell us. The framework of Sanchez et al. (2018) was used for the backbone analysis. This way, the trees can be built around how certain taxa are related, while the morphological data plots where those without molecular data would be. The outgroup taxon was Nautilus pompilius.


Surprisingly, contra in-game lore, Inklings and Octolings are consistently recovered as sister taxa. The two species are united by numerous features, mostly having to do with living on land and shooting ink everywhere. Feasibly, these could have evolved independently, but compared to other NPC species in the game, the similarities between these two are striking. If this is true, this may make their rivalry analogous to that which may have occurred between Neanderthals and anatomically modern humans in the Pleistocene (Finlayson & Carrión, 2007) in response to environmental change (changing sea levels and climate change, respectively). This may also explain why most Octarians are so different from Octolings – they may have actually descended from octopuses, and gone down a completely different evolutionary path towards sapience and land-living. It is canon that Octolings were brainwashed into serving the Octarian army, so this might imply that the Octarian-Octoling link is largely fabricated. Of course, that adds a layer of in-game cultural implications that is out of the scope of this paper.

In all analyses, both species ended up well inside Ommastrephidae, the flying squids. This fits with what we know of Inkling biology. As previously noted by Salvador & Cunha (2016), the leaping ability of Inklings in squid form (“super jump”), demonstrated in Splatoon, Splatoon 2, and Super Smash Bros. Ultimate, may be exapted from the tendency of flying squids to jump above the surface of water. Inklings are also bioluminescent, a trait shared with certain members of Ommastrephidae, including Ommastrephes itself. The unusual octopus-like form of the Octoling may be convergent evolution with Octopoda; Octolings display the same “super jump”, not known in any octopods, and similar awkward terrestrial locomotion in coleoid form (in contrast to the Octarians).

But aside from being a fun and way too time-consuming exercise in phylogenetics, what does this tell us? Our results echo the suggestions of Salvador & Cunha (2016) that the design of Inklings was likely heavily influenced by ommastrephid squids that live in Japanese waters, such as Todarodes pacificus and Ommastrephes bartramii. This shows that the designers of the Splatoon franchise likely deliberately modeled this game’s characters after specific cephalopod species (echoed in the fact that the Japanese names of several characters reference specific real-world species). Nintendo certainly knows their squids.

Figure 2. Strict consensus tree of the “spineless” analysis, with Pohlsepia removed a posteriori because it was unstable.
Figure 3. Strict consensus tree of the analysis with a molecular backbone constraint applied.


Finlayson, C. & Carrión, J.S. (2007) Rapid ecological turnover and its impact on Neanderthal and other human populations. Trends in Ecology & Evolution 22(4): 213–222.

Goloboff, P.A. & Catalano, S.A. (2016) TNT version 1.5, including a full implementation of phylogenetic morphometrics. Cladistics 32(3): 221–238.

Lindgren, A.R.; Giribet, G.; Nishiguchi, M.K. (2004) A combined approach to the phylogeny of Cephalopoda (Mollusca). Cladistics 20(5): 454–486.

Salvador, R.B. & Cunha, C.M. (2016) Squids, octopuses, and lots of ink. Journal of Geek Studies 3(1): 12–26.

Sanchez, G.; Setiamarga, D.H.E.; Tuanapaya, S.; Tongtherm, K.; Winkelmann, I.E.; Schmidbaur, H.; Umino, T.; Albertin, C.; Allcock, L.; Perales-Raya, C.; Gleadall, I.; Strugnell, J.M.; Simakov, O.; Nabhitabhata, J. (2018) Genus-level phylogeny of cephalopods using molecular markers: current status and problematic areas. PeerJ 6: e4331.

Schultze, H.P.; Fuchs, D.; Giersch, S.; Ifrim, C.; Stinnesbeck, W. (2010) Palaeoctopus pelagicus from the Turonian of Mexico reinterpreted as a coelacanth (Sarcopterygian) gular plate. Palaeontology 53(3): 689–694.

Sutton, M.; Preales-Raya, C.; Gilbert, I. (2015) A phylogeny of fossil and living neocoleoid cephalopods. Cladistics 32(3): 297–307.

Voight, J.R. (1997) Cladistic analysis of the octopods based on anatomical characters. Journal of Molluscan Studies 63(3): 311–325.

Young, R.E. & Vecchione, M. (1996) Analysis of morphology to determine primary sister-taxon relationships within coleoid cephalopods. American Malacological Bulletin 12(1/2): 91–112.


Because the author lives approximately 10,000 years before the evolution of either Inklings or Octolings, he was unable to access any for study. However, he was able to access relevant game models and amiibos in private collections for the collection of morphological data. He also adopted a Sanei Inkling boy plush during the preparation of this manuscript.


Props to Nintendo for making this awesome franchise in the first place, and to an anonymous friend/reviewer for trying to dissuade me from doing this silly project.


Henry Thomas is a biology student at the University of California, Berkeley. He mostly studies pterosaurs, but also dabbles in the phylogeny of other creatures, regardless of whether they exist or not.

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