Bizarre Sexual Dimorphism



"Jen: Wings? I don't have wings! Kira: Of course not. You're a boy."

- The Dark Crystal

As explained elsewhere, we primates have certain visual cues we rely on to tell a woman from a man; men are generally taller and more muscular. Women are shorter, more curvaceous and have breasts. This is because we are Sexually Dimorphic animals.

This is also the case in several other animal species, particularly those who also rely mostly on vision, and communicate largely with visual displays. The most common kind of dimorphism is when males and females of the same species sport different colors and markings.

Then there are a few species (relatively speaking) in which males and females look wildly different. One sex may even have an entire physical feature that the other lacks (other than, you know, the obvious one) -- if the other sex doesn't sport his/her own trademark physical feature. In a very few species, males and females may be different enough to look like completely different animals.

And science fiction writers, when inventing aliens, love to run with this.

There are several alien or fantastical creatures in which the sexes are wildly different. This tends to run towards the extreme end of the Earth scale and beyond: they could be greatly unequal in strength or intelligence; one sex could even be reduced to an inert breeding machine (like the real-life scale insect) or parasite (which actually does happen on earth with deep-sea dwelling angler fish)!

Tends to go hand-in-hand with Bizarre Alien Biology. See also Cute Monster Girl, One-Gender Race, Humanoid Female Animal, Mister Seahorse, The Ugly Guy's Hot Daughter and Bee People. For a (relatively speaking) more subtle sex difference, see Tertiary Sexual Characteristics.

Taken to the logical extreme, this leads to Improbable Species Compatibility.

Do also take note that this trope, in spite of its name, is not limited to species with binary sex systems.

Anime and Manga

 * We reiterate: See Cute Monster Girl.
 * This also appears to be the case for the plants in Trigun, with the girls in bulbs with the big strange eyes and all, and the only two guys walking around looking like blond men. But later manga material shows that Vash and Knives really are just mutants (probably throwbacks; the odds that the people who engineered the plants didn't use human DNA are vanishingly small), because some female independents come from space; the twins are just even weirder.

Comic Books

 * The Zamarons and The Guardians of the Universe. The Zamarons are the female member of the race, and they look like human women. The Guardians look like blue midget old men with white hair. They used to be identical, but the two races separated and continued to evolve (without reproducing....) into their present form. The Zamarons were later retconned to have always been blue skinned, black eyed, hairless and almost noseless (think tall, blue, female Roswell Greys). And they are still almost three times the size of the Guardians, so the trope still applies since the two are either the same species or offshoots of the same species, Depending on the Writer.
 * Even more confusingly, there are also female Guardians who look like Guardians. They originally came to be when Kyle Rayner (possessing at the time the godlike powers of Ion) recreated the Guardians years after Hal Jordan (at the time possessed by evil entity Paralax) wiped them all out. Of course in the current series all this is ignored and the guardians are shown in flashbacks to have been always both sexes. Don't ask where that means the Zamorans came from. Aren't retcons a wonderful thing?
 * In Phil Foglio's XXXenophile, Martian females are all gorgeous, buxom, four-armed women, and the males are tiny, squat, furry, mostly shapeless (and, incidentally, non-sapient) hexapods with disproportionately large sex organs.
 * This is then given an extra twist at the end of the story. After making "First Contact" with a human explorer, a giant battlesuit bursts into the room- and the Martians assume that the giant robot must be a human female.
 * Huldra (female trolls), in the story A Beautiful Tale, were scary-powerful Cute Monster Girls with cute little shark teeth and long tufted prehensile tails. We never actually see a male troll... but a human character who has infers that humans must not look dimorphic at all to trolls. (She's wrong; the huldra is fully aware that she's female and still wants to marry her. With all that that implies.)
 * The Badoon, a Marvel Comics alien race, have scaly reptilian males and fur-covered females. The females are also stronger and tougher, but less violent and cunning than the males, and the sexes don't interact except during their once-in-a-lifetime mating frenzy. The females also have Non-Mammal Mammaries, despite laying eggs, though it's possible that they do suckle their young.
 * Rom Spaceknight's enemies the Dire Wraiths come in two flavors: the technology-using males, who look like ugly, fanged, gangly-limbed Pillsbury Doughboys; and the sorcery-using females, who are pure Starfish Aliens.
 * In the pre-Crisis version of the Vega system, one world's male inhabitants look very much like humans. The females look like giants snails. To quote the gamebook, "This seems to work for them."
 * In Legion of Super-Heroes, male Dryads look like large masculine-seeming humanoids made of stone. In some continuities, female Dryads look like large masculine-seeming humanoids made of crystal. (In others they look like the male dryads with narrower waists and Non-Mammal Mammaries.)
 * Male Warlocks from Nemesis the Warlock walks on a pair of goat-esque hooves, while female have centaur-like bodies.
 * This concept seems to have been parodied in She-Hulk's series with the Thaloomians, the interdimensional race that the Living Eraser is a member of. Males are short, chubby, and toad like, while females all look like She-Hulk. The ruler of these aliens wanted to marry Jenn, claiming she resembled the perfection of his species. Jenn herself claimed it was like "one of those cheesy pulp-style science-fiction worlds where all the women are fabulous babes and the men look like something I'd scrape off the bottom of my shoe!" Of course, it's doubtful even the typical kidnap victims would be any less angry towards her abductor...

Films -- Live-Action

 * The Devaronians of Star Wars (See picture [[media:200px-Devaronians.jpg|here]]). The males look like devils. Hairless, with pointed teeth and large triangular horns. Also kind of small. The females are tall, hornless, covered in thick fur, and look like humanoid lemurs.
 * Some artists, especially the great Jan Duursema, draw female Devaronians that look a little like the lemurs shown above, and more like hornless versions of the males (or red skinned humans with black spots), as seen here.
 * Female Devaronians vary a lot, from the fairly hairless Sian Jeisel to Aven'sai'Ulrahk. Darth Maladi looks like she was fairly hairy at one point (the picture does not show it clearly, but she sports impressive side burns) but the fact she sports Sith Tattoos indicate she might have undergone some epilation.
 * Another Star Wars Expanded Universe example are the Cathar. Men look very much like saber-tooth lions who happen to be bipedal and have opposable thumbs. Women tend towards the Catgirl end of the scale.
 * Though, rather humorously, female Cathar looked just as animalistic as the males until they decided Catgirl Juhani in Knights of the Old Republic was a Cathar. Perhaps explainable due to the two being subspecies of one race.
 * Not to mention the Twi-leks, where the men range from "mildly ugly" to "monstrous" while the women are almost all attractive.
 * Maybe a case of Beauty Equals Goodness, seeing as nearly every male twi'lek seen is a corrupt evil bastard, while all females are good people or at least innocent slaves.
 * Probably the case, as looking at some "good" male Twi'leks, like Shado Vao, shows them to be good looking.
 * Unless of course it's Darth Talon, because Evil Is Sexy. Only for females, though. Which brings us full circle back to the dimorphism trope.
 * The novelization of Star Trek IV the Voyage Home would have you believe that this is a male Deltan. No other source corroborates this, and it can be assumed to be an error.
 * The "male Deltan" is later established as an Efrosian, the only other seen member of the species being the Federation President in the Star Trek VI, due to reuse of makeup.
 * In the Star Trek: Titan novels, the Efrosians come from "Efros Delta", so you could call them Deltans, but they aren't those Deltans.
 * In the goofy Mom and Dad Save The World, the nonhuman natives of Spengo have males with dog-heads and females with fish-heads.
 * Evil Alien Conquerors; the male aliens look just like human males, but the females look... just plain weird.
 * In the movie version of Land of the Lost, Shaka, a Pakuni, is a hairy ape-like creature. The "hideously ugly" females of his species look like human women.
 * In Zone Troopers, a group of American soldiers in WWII discover crashed aliens in Axis territory. The males are tall, pretty, blue-skinned Aryans. The females, as it's later discovered, . Needless to say, the soldiers had a bit of a shock with that revelation.

Literature

 * Weird exception: With all the Starfish Aliens in Wayne D. Barlowe's Expedition, it's interesting to note that this trope is hardly used at all. Indeed, it's often hard to tell if the terms "male" and "female" even apply; many species are functionally hermaphroditic, and mating impregnates both individuals. The closest thing would be the female Sacback, who lives her adult life buried underground as her male counterpart roams around finding food for her. Other creatures make up for it by having bizarre life-cycles (a giant ocean-going beast starts out as a tiny flyer, for example).
 * The Termagant Trogs in The Edge Chronicles. The dominant females are, as indicated by the name, massive hulking bald Amazons. Their husbands are skinny, shrimpy and rather pallid creatures usually kept locked up.
 * As if that wasn't weird enough...when the females come of age, they undergo an induced Metamorphosis from sweet, ethereal little redheaded girls into the aforementioned bald (and bad-tempered) Amazons.
 * In David Gerrold's The War Against the Chtorr series, the bunnydogs/bunnymen and libbits were eventually discovered to be the male and female of the same species.
 * Myth Adventures by Robert Asprin includes a dimension called Trollia, where the men are Trolls (enormous, warty, frightening creatures right out of a fairy tale) and the women are Trollops (gorgeous and human-looking except for green-tinged skin and hair).
 * The Soft Ones in Isaac Asimov's The Gods Themselves have three sexes: Rational/left, Emotional/mid and Parental/right, which reproduce by fusing their bodies together and "melting".
 * It's more like the Soft Ones are the.
 * William Tenn's Venus and the Seven Sexes (1949) features a seven sexed species that passes gametes in a chain: sex 'D' receives from sex 'C' and transmits to sex 'E'. The sex of the offspring is determined by the sex of the parent which receives/completes the fully fertilized gamete. One sex is tasked with coordinating the family.
 * Theodore Sturgeon's "The World Well Lost" centers on a pair of fugitive "loverbirds" from the planet Dirbanu, which has shunned contact with Earth. The loverbirds are initially assumed to be a male and female, but they manage to explain, via some illustrations, that male and female Dirbanu are vastly different in appearance. In fact, the main reason why the Dirbanu dislike humans is due to homophobia, because they perceive all human relationships as being homosexual.
 * The Cygnans in the novel The Jupiter Theft had human-sized females and insect-like parasitic males that were permanently attached to the females.
 * Ringworld: The Kzinti are catlike people, and while the males are of humanlike intelligence, the females are not. The Puppeteers, who are already fairly strange looking, have three "sexes", one of which is non-sentient, technically a different species, and serves as a host for a the embryo created by the two others.
 * However, ancient Kzinti females were entirely sentient—their current state is the result of intentional breeding for unintelligent women, with the help of genetic engineering technology. That's what happens when you uplift a bronze age species.
 * Strangely enough, Kzinti (in Man-Kzin Wars) consider the human sexes to be separate alien species, based on behavioral differences. A human female (Manrrett) is considered to have apparently faster reflexes, higher pain tolerance, and greater intellectual insight, than a human male (Man).
 * Don't forget Grogs. The adult females are large furry cones with a mouth, which cannot move from the rock they attach themselves to. Young females are something like alien bulldogs, and young males are akin to chihuahua, neither of which are sentient. Adults telepathically control the young into breeding, and use the same telepathy to force prey animals to leap into their mouths, since giant immobile cones aren't good at hunting.
 * In Flatland, men are polygons (whose number of sides and symmetry indicates their social class) and all women are single lines—hysterical, dangerously sharp, and not too bright. (The blatant sexism and classism is a satire of the attitudes that people actually had when it was written, as explained in a foreword added by Abbot when people missed this.) Other details of their physiology, including how they reproduce, are never explained.
 * In Flatterland, a 2001 sequel by Ian Stewart, it is implied that the females utilize the males in detaching a segment after sometimes folding the segment into a new shape with roughly the same number of sides as the male. The females are also confirmed to be multi-sided beings that are rotated into a third dimension, which just brings up even more questions, including already-answered questions, the answers to which were suddenly made invalid.
 * The Khepri in Perdido Street Station and all of China Mieville's other Bas-Lag novels are an insect-like race with small non-sentient males and females that resemble red-skinned human women with a similar type of insect forming their heads.
 * In the sequel, The Scar, there is a race of mosquito people, the Anophellii, whose women are vampiric winged creatures that have fang-like protuberances that extend from their mouths to penetrate their victims. The extremely passive males have mouths that are described as being like anuses. Yeah ...
 * The dominant race of the Empire of Azad in Iain M. Banks' The Culture has three sexes: One is male, the 'apex' has ovaries and "a kind of reversible vagina", and the female has a womb. The only non-sexual difference between the sexes is the eugenically bred-in lowered intelligence for non-apices. Sexism here sees females as breeders and domestics, males as workhorses and disposable soldiers.
 * In Larry Niven's Draco Tavern stories, all the Chirpsithra were female. There are males, but the Chirpsithra won't talk about them.
 * In one of the stories, the Chirp males are revealed.
 * Jack Chalker's Well World, in all its glory. Too many examples to list.
 * The Piggies and Buggers in Speaker for the Dead. Especially the piggies. The buggers are about as sexually dimorphic as real bugs. Both species call humans weird for having sexes so similar that both can perform the same societal function.
 * The piggies' life cycle and reproduction is strange enough that it really deserves to be explained in full detail (though put in spoilers). [[spoiler:Both sexes start out small and grublike, but the dimorphism starts quickly. The males develop into the pig-like form that the humans in the story first assume were the only form, but will develop into enormous trees upon death and retain their sentience upon being ritually vivisected.
 * The females, on the other hand, almost all stay small and grublike, and after a certain time are carried by the pig-like males to the trees, and are impregnated by said trees via pollen. Then, when the young they're carrying are ready to be born, they eat their way out of their mother. In addition, the occasional female will develop into a pig-like form like the males to serve as a matriarch, and eventually also be vivisected to become a "mothertree", which holds all the young and nourishes them with its sap.]] "Bizarre sexual dimophism" doesn't even begin to cover it.


 * There's also the . The xenobiologists spend half the book puzzled over evidence of genetic exchange (which implies the species don't reproduce by parthenogenesis like some earth species do), yet without any apparent presence of males.
 * This is all a relatively recent development from an evolutionary standpoint, caused by.
 * The Tralfamadorians from Kurt Vonnegut's Slaughterhouse-Five claim that humans have seven sexes, cases of Unreliable Narrator notwithstanding—likely because they can see through time as well as space. Some of the "sexes" they recognize are "male homosexuals", "women over sixty-five" and "baby".
 * In David Brin's Uplift Storm trilogy, male urs are much smaller than females, and generally less intelligent (though sentient; a male urs is a secondary character in the series). Females have pouches to carry their mate around.
 * In Dennis L. McKiernan's Mithgar series, dragons are the male of a species. What are the females? Of all things, krakens!
 * Dwarves are interesting. Only the males are seen by outsiders. Anyone that visits a Dwarvenholt that is considered friendly might catch a glimpse of a veiled, graceful figure that swiftly departs, said to be a "Chakkia" (the dwarves call themselves Chak). One character caught a glimpse of a Chakkia without the veils: she was beautiful. Another character, able to see the "true form" or light of living things, stated that he did not believe the Chakkia to be dwarves at all, their light was too different.
 * In another book, a seer also commented (to herself) that they were clearly not the same species as the male dwarves, then recognised them as... something else that she wouldn't tell us about, wondered if their state was some sort of divinely ordered punishment, and then claimed it was none of her business and turned away. If he keeps writing enough books he MAY explain all this.
 * Bob Shaw's "Warren Peace" has the Squelchers, an alien race with no less then six different sexes, each one with its own unique appearance, and with a reproductive cycle where each sex fertilizes the others in turn. The forms look so different that, to the vast majority of the universe, the species only consists of the fourth sex, which resembles an orange haired saggy sasquatch (kind of like a blown up balloon that's developed a slow leak) with multiple eyes in a ring around its head (usually covered by its fur), oversized feet that let it wade on water, and two giant red nipple-like gamete sacs positioned one above the other on its torso. The fifth sex, the only other one mentioned, is described as being indistinguishible from a tree, except for the presence of a pair of two dual-pronged ovipositors (they look almost identical to staples) sprouting from its trunk.
 * Inverted in Terry Pratchett's Discworld, where male and female dwarfs look pretty much identical. Both males and females have beards and dress identically in lots of layers of thick clothes and chainmail. In fact dressing noticeably "feminine" is considered outrageously shocking. A large part of Dwarven courtship involves tactfully finding out what sex the other dwarf is...
 * Later novels have Dwarf society slightly imitating humans, with female dwarfs adopting Tertiary Sexual Characteristics for style and comfort. A discrete ribbon in the beard, steel-heeled boots, chain mail that doesn't chafe...
 * Played straight with the pictsies, tiny Bee People whose female breeders ("keldas") start out the same size as males, but grow twice as tall and spherically-fat after a lifetime of birthing hundreds of offspring. A kelda's rule over her clan is absolute, as she's mother to most and wiser than any.
 * Which isn't saying much as male Pictsies are impulsive and slow to think, even for a Proud Warrior Race. They'd probably all be dead without a kelda to keep them in line.
 * Similar to Discworld, The Lord of the Rings inverts the trope with the dwarf race, with it being stated that female dwarves are often mistaken for men due to being similar to the males in voice and appearance. As every male dwarf we encounter in the book has a prominent beard, some readers have interpreted this as meaning that the female dwarves even have beards.
 * In the films this became a rather comedic scene where Gimli humorously explains this phenomenon to a human woman. The human woman (Eowyn) then turns around and looks at Aragorn to see if Gimli is pulling her leg, and he mouths, "It's the beards," and gestures at his chin.
 * Confirmed in The Silmarillion, which says "For the Naugrim have beards from the beginning of their lives, male and female alike."
 * Bruce Coville's My Teacher Is an Alien series mentions one species that requires "seven genders [sic] to produce an egg, and three more to hatch it".
 * Averted with Kreeblim, a female alien who looks very different to the previously introduced male one, Broxholm. The human narrator initially assumes this trope is in play, but it turns out that they are of completely different species.
 * Chanur Saga: The stsho have "bizarre sexual trimorphism"; their sexes are called "gtst", "gtste", and "gtsto". If emotionally disturbed, they will undergo "phasing" and change sex as well as personality.
 * In addition to "gtsta" ("Holiness"), the sexless form that some (all?) elderly stsho eventually take.
 * In The True Meaning of Smekday by Adam Rex, the heroine meets one of the Boov who are invading Earth and assumes he's a boy. When she thinks about this, she realizes that he could be a girl, or even that his species might not have boys and girls. When she asks, he tells her she's right, he is a boy...and then he proceeds to explain that his species has seven genders and "boy" is only one of them. They translate in English to: girl, boy, boygirl, girlboy, boyboygirl, and boyboyboyboy.
 * In Frank Herbert's Dune series,.
 * In The Dirdir by Jack Vance, the titular Dirdir race has a complex sexuality. A male will be born with one of twelve different sex organs, females one of fourteen. Each type matches one or more of the others. Mating is complicated by the great secrecy surrounding sex: no-one wants to be "outed" as a particular sex since there are a host of restrictive sexual stereotypes waiting to be applied.
 * In the Star Trek novels by Diane Duane, there is one race, the Sulamid that is described as a bundle of bright purple tentacles about six to seven feet high, topped off with a sheaf of pink-stalked and tentacled eyes with triangular pupils and a purplish, "bloodshot" look. According to Dr. McCoy, they have twelve sexes, and all of them claim to be male, especially the ones that bear the children. The Enterprise has at least two of them among the crew, Mr. Athende in Maintenance and Lt. Meshav, from Data Management.
 * And in the Star Trek Expanded Universe, Andorians have four sexes, based on a throwaway line in Star Trek: The Next Generation about Andorian marriages involving four people.
 * In Everworld, the Hetwan males are humanoid, while the females are described as transparent bags of organs with wings. How they reproduce: Hetwan males tear the females apart and eat them, and new Hetwan form at the males' waist.
 * In Edgar Rice Burroughs's Tarzan series, the people of the lost city of Opar consist of a tribe of stunted, hairy, almost apelike men ruled over by a beautiful, entirely human-looking woman. It's implied that the inhabitants degenerated by mating with great apes, but somehow the degeneration didn't affect females the way it did males.
 * In Man After Man, one species of post-Homo sapiens hominid developed the ability to hibernate. As males slept for most of the year, whereas females remained awake to nurse their young except in the depths of winter, the sedentary males wound up having a lifespan several times as long as that of the nomadic females.
 * Dougal Dixon's work has a lot of this, like the Matriarch Tinamou, Bardelot and the Common Pine Chuck from After Man: A Zoology of The Future and the Dingum in the New Dinosaurs
 * John Varley's Gaea Trilogy features a dimorphic intelligent species in which the gas-inflated males are living blimps and the deep-diving females are organic submarines. They begin life as sexless, snakelike animals, then choose which adult sex to metamorphose into when their consciousness and race-memory emerges. Mating takes place at the ocean's surface, aside from which the two sexes never interact.
 * In Sergey Lukyanenko's Spectrum, the main character meets several members of a race of Reptilians (according to the book cover, they look like Narns). Later, his Love Interest explains that the non-sentient animals they travel with are actually their females, as she saw one of the aliens mating with one of the animals. That or something else. The cause for this appears to be an ancient cataclysm that affected all known races, causing many of the bizarre biological and psychological features of the aliens.
 * In The Steerswoman series, female demons are tall, spray acid from under their arms, and can make sculptures (out of a wax-like substance that their bodies produce). Male demons are much shorter and cannot make these sculptures.
 * Retief: In Retief and the Pan-Galactic Pageant of Pulchritude, an alien comments to Retief on the 'remarkable sexual dimorphism' of Terrans, after Retief slips a ringer into the titular beauty pageant: . The alien is apparently used to sexual dimorphorphisms extreme enough to make this plausible, and doesn't notice the difference between human males and females, except to suggest that the human with the large protrusions on his (actually 'her') upper thorax might want to see a doctor about it.

Live-Action TV

 * The Pak'ma'ra from Babylon 5 were like this... supposedly. At least, there were rumors that the reason you never see a female Pak'ma'ra is that they're non-sentient and attached to the males. What's more disturbing is that this is still not confirmed despite male Pak'ma'ra doing Human pornography.
 * In the episode with the Pak'ma'ra pornography, the doctor specifically states that a species like the Pak'ma'ra is sexually incompatible with humans. From a comment made by Gideon moments later, it can be inferred that this Pak'ma'ra underwent surgery or is wearing a prosthetic to get the right equipment.
 * The future aquatic apes (Mer) from Primeval.
 * This trope is played with in the first season of Farscape, where a Yenen named Staanz (played by a male actor) turns out to be an attractive female of the species.
 * In the Buffy the Vampire Slayer episode "Beer Bad", a group of male frat boys - and Buffy - drink cursed beer that causes them to "de-evolve" physically, mentally, and psychologically into Neanderthals. The males undergo a drastic physical change, becoming brutish and bestial with crooked teeth, heavy brow ridges, and plenty of extra hair, their intelligence only barely better than an animals'. Buffy, however, still looks mostly human and attractive, a Nubile Savage type, and can still talk, albeit in Hulk Speak. Possibly justified in that Xander took her home earlier than the others and they thus drank far more of it.

Oral Tradition

 * According to some traditions, the male equivalent of a mermaid is a "merrow." Merrows are hideous but friendly to humans, as long as said humans don't try to steal their wives. Of course, mermaids are hot, so humans try to steal their wives a lot, actually, thus incurring the merrows' wrath.

Puppet Shows
"Jen: Wings? I don't have wings! Kira: Of course not. You're a boy."
 * In the Dark Crystal film, the two Gelflings look quite similar, but possess a significant hidden difference, leading to this interesting exchange:


 * Planet Koozbane from The Muppet Show showed a "mating ritual" of the Koozbanian creatures and they looked nothing alike.

Tabletop Games

 * The Skaven of Warhammer Fantasy Battle fantasy take this to extreme of the females being non-sentient and even more rat-like than the males--"breeders", as they are called, basically look like Ogre-sized or larger female non-anthropomorphic rats, made even bigger by the fact they are swollen so huge with litters that they can't walk.
 * The current Codex seems to show that there are normal size sentient females.
 * Likewise, in a non-canon third-party Dungeons & Dragons sourcebook, The Slayer's Guide to Troglodytes from Mongoose Publishing, the titular lizard-people are made up of sentient humanoid males and non-sentient females that look like huge bloated lizards.
 * In Castle Falkenstein there are no female Dwarfs. Dwarfs always mate with Fairy women-if the child's male, it'll be a Dwarf like dad, otherwise, it'll be whatever sort of Fairy mom is. (There are male Fairies.) See Gender Equals Breed.
 * The Dungeons & Dragons second edition Monster Manual implies that the Always Male satyrs and the Always Female nymphs are male and female of the same species.
 * Let's talk about sphinxes shall we? There are technically four sexes: Androsphinxes (male human head) Gynopshinxes (female human head) Criosphinxes (ram's head) and hieracosphinxes (hawk's head) of respectively Lawful Good, True Neutral, Chaotic Neutral and Chaotic Evil alignment. Gynosphinxes are female, the others are Always Male. A gynosphinx mating with a hieraco- or criosphinx always produces hieraco- or criosphinxes as offspring, while if mating with an androsphinx they produce twins, one of which is a gynosphinx and the other an androsphinx. This means that, for obvious reasons, gynosphinxes don't like mating with crio- or hieracosphinxes much, which means that the other two reproduce pretty much entirely through rape. Androsphinxes on the other hand don't like mating at all much, and it is noted that gynosphinxes will pay adventurers handsomely for the location of an androsphinx. In other words, Dungeons & Dragons monsters are screwed up.
 * And very likely going extinct, if gynosphinxes aren't having enough daughters to replace themselves each generation.
 * There are also medusae—complete with snake hair and petrifying gaze—and maedars—which look more-or-less like bald human men—which are the male and female of the same species. Since 4th Edition this dichotomy in dimorphism has lessened; while male medusas are still bald (and have a gaze that poisons anyone that it falls upon rather than a petrifying gaze) they are quite obviously recognizable as members of the same species as the females.
 * Pathfinder has the lashunta, a humanoid extra-terrestrial species with males and females so vastly different that it affects their racial ability score modifiers: their males are short, stocky and covered with hair and have a +2 bonus to Strength and a -2 penalty to Wisdom, their females are tall, thin and graceful and have a +2 bonus to Charisma and a -2 penalty to Constitution, both sexes have a +2 racial bonus to Intelligence.
 * The Talislanta game does this with not one, but two species:
 * In the first example, the stooped, wrinkled females are Gnorls and the gangly, monkey-like males are Weirdlings. The former live in elaborate cavern homes, while the latter live in simple burrows; they inhabit different regions, but come together every 50 years or so to mate. Both sexes were named separately by outsiders, who'd thought they were different races at the time, and no Gnorl or Weirdling will admit what (if anything) they call their mutual species.
 * In the second example, female Batreans are Green Skinned Space Babes, complete with hyper-seductive pheromones, while their male counterparts are grotesque, hulking ogre-ish creatures. The females are intelligent and live in Polynesian-style villages, while the moronic males shamble around in the jungle, looking for edible things to hit.
 * In one of the many Star Trek role-playing games, Orions are presented as having green-skinned females and gold-skinned males. No canon source bears this out. On the live-action shows, no males are seen until Enterprise and they're all green. Many of the Expanded Universe sources present Orions as having a range of skin colors, but pretty much universally present males and females as having the same range of colors, which generally doesn't include gold.

Video Games

 * The Grekim from the RTS Achron have three genders (octo, pharo, and sepi). Octos crawl along the ground with six limbs out to the side like an insect or crab, with the remaining 2 held out front like arms. Sepis float slightly above the ground with their tentacles dangling beneath them. Pharos walk around with six limbs directly beneath them, and the other two out front. The changes in body types get even weirder with the 'higher' classes. Did we mention that they are all cyborgs and they use Time Travel as their weapon of choice? Starfish Aliens indeed.
 * In Pokémon, there are a number of species that are gender exclusive (Jynx, for example, is only female). But some of these Pokémon are considered the opposite sex of the same species. The Nidoran pairs come to mind, familiar to most people, but Tauros found his female counterpart in Miltank, and later generations continued the trend. This might be Gender Equals Breed, though.
 * It's debated whether or not Miltank and Tauros are opposite genders of the same species—unlike Volbeat/Illumise and the Nidoran family, Miltank eggs can never hatch into Tauros.
 * Burmy, based on a bagworm, evolves into a Mothim if male or a Wormadam if female. Their appearances are VERY different, as Mothim is a moth and Wormadam is still a pupa.(Like real bagworms.) Wormadam actually has three appearances, but that's unrelated. Other examples: In the anime, a Latias produced a Latios egg like the Volbeat/Illumise thing. Some species also have sexual trimorphism: Only male Kirlia can evolve into Gallade, but both genders can evolve into Gardevoir. Only female Snorunt can evolve into Froslass, but both can evolve into Glalie. Combee can be both genders, but only females evolve into Vespiquen, males do not evolve.(Like bees.) Also Rufflet/Braviary and Vullaby/Mandibuzz are considered counterparts, but they don't produce each others' eggs much like Tauros/Miltank.
 * Also some species have ACTUAL sexual dimorphism, as in visual differences in the same species based on gender. Most of them are tiny differences(such as female Rattata having shorter whiskers) but a few species are very different. Hippopotas/Hippowdon are quite different in color. Male Unfezant are much "flashier" than females.(Because they're birds.) Male Frillish are blue, females are pink...and when they evolve the male gets a huge Pringles mustache while the female gets a fluffy collar.
 * In Darkstalkers, Succubi are gorgeous women and nymphettes. 60% of Incubi, on the other hand, are gigantic mutant insectoid dragons.
 * Similar to Darkstakers above, the Shin Megami Tensei games have both Succubi and Incubi as recrutable demons. Succubi (and the related Lilim) resemble attractive women in skimpy clothes with wings; Incubi are small, hideous imps with a large growth (even longer than their bodies!) coming from their crotch.
 * The Draenei. The males are huge and bulky, with large, ridged tails, forehead plates, and catfish whiskers. Their kinswomen are lithe and willowy (they're almost the same height as the boys, but would appear to weigh perhaps half as much, if that) with short, thin tails and prominent horns. They also have catfish-like tendrils, but theirs sprout from behind the ears instead of on the face.
 * Also trolls, in the same universe. This is especially true of forest and ice trolls, but even the (playable) jungle trolls are glaringly dimorphic. Females have tiny tusks, pointy little noses, and can be Cute Monster Girls (although not all of them are); males have huge tusks, beak-like noses, and would be at least a foot taller if it weren't for a permanent slouch.
 * There's an idle animation where they pop their back, briefly reaching full height. It's... startling, to say the least. The only reason they don't stay standing tall is they would otherwise not fit into doors. A Darkspear troll male (what you can play as) is tallest thing you can be, standing straight up it's still about a half-foot taller than a Tauren male.
 * Holy Light... his head scrapes the top of the screen!
 * The Naga as well, which is often pointed out by Richard A. Knaak and other Warcraft authors. The females are lithe and still very elven from the waist up, despite their four arms and serpentine tails, but the males are decidedly draconic from the waist up, while still only having two arms. It is also implied that the brains of the males have degenerated quite a bit, which explains why only the females are ever spellcasters.
 * Orcs are not quite as extreme as the Draenei, but they do feature very large, burly males with hunched posture alongside females that more or less look like muscular green-skinned human women.
 * Tauren males are much more muscular than the females, though not unbelievably taller. The males hunch over so much that their heads appear to be growing from their chests; the females look a little more humanoid. The difference isn't quite as bad when you take into account the fact that they're basically a species of anthropomorphic bovines, but it's still a pretty big difference.
 * Night elf males are at least seven feet tall, with wide shoulders, tiny waists, and lanky, muscular limbs. The females are much more realistically propotioned.
 * Ironically, in Night Elf society the females are the warriors, not the males. Despite the fact that the males are seven-foot tall brickhouses.
 * Averted with the Gnomes and Goblins, where the dimorphism is comparably normal. The male and female gnomes stand at the same height and have almost the same proportions. Goblins have the same posture, noses, ears, size and proportions; the only major diference is that the women have lighter and smoother skin.
 * It should be noted, a lot of the dimorphism in playable races comes mostly from the playerbase complaining, Trolls, Tauren, and Blood elves were extremely close to one another in body shape in their early alpha models, granted, female trolls were terrifying, Tauren women were...meh. and Blood elves were actually very good looking (The males became dimorphic because players were complaining about them being too skinny... nevermind the fact of all the human-like player races, they had the most normal body shape). We didn't know if this would have applied to female worgen, as at the time they weren't even playable in alpha, and the player responses were already negative.
 * More or less averted with the Blood Elves. Both male and female have long, beautiful hair, similar postures, facial features/proportions, etc. The main difference is that the males are significantly more muscular and sometimes have facial hair (never more than a small goatee, though) and females have a mild form of Hartman Hips and a "thinner" face.
 * And now we have Worgen: the men are big, bestial wolf-men; women look like characters out of a furry webcomic.
 * Every species in Sword of the Stars, except the Humans and the Liir (who are hermaphroditic), have some kind of this or another. The Hivers are Bee People so this is to be expected (not to mention that workers and warriors are sexless to begin with); Zuul females are approximately three times the size of the males and animalistic while the males are weedy psionic masterminds with a specialty in Mind Rape; Tarka males that become fertile (which only about one in a thousand do, and which can only be accomplished by eating unfertilized Tarka eggs) approximately double in size; and Morrigi females are basically dragons while the males are more akin to birds.
 * This also receives a kind of reverse-lampshading in the fluff, where it's noted that due to the death of sexism in Human society and the lack of dimorphism between men and women, most other races actually have a hard time telling the difference.
 * Comes into play in Grandia when you meet Milda who doesn't look any different from any of the other long-eared beastfolk of the game. Then you get your first glimpse of the males of her tribe when you meet her husband Darling (that's actually his name!), who is...a large, robed, bipedal cow.
 * Those huge, blind, nigh-invulnerable Berserkers in Gears of War? That's a female Locust Drone. The male drones could pass for humans in poor lighting conditions. It's also stated that Berserkers are tied down during sex so they don't beat the Drones to pulp during the Act. Oddly though, the Hive Queen is decidedly more of a Gorgeous Gorgon.
 * On the MUD Dark & Shattered Lands, there's the Leonine race, which may just take the cake. The males are Wemics, basically centaurs with lions instead of horses. The females are Felars, pretty much just catgirls, which can have fur on as much as ninety or as little as ten percent of their bodies. Yes, the males are quadrupedal and the females are bipedal. Cue a huge number of off-color jokes...
 * The female Covenent Elites from Halo, as seen in the Halo Legends animation anthology do not resemble their male counterparts much. Although they have the same coloring, they look considerably more humanoid.
 * Male Sadida from Dofus and Wakfu have long green hair all over their face, whereas the women appear more normal. Much more blatant with male Sram from Dofus, who look like skeletons, while the females look completely normal.
 * Subverted in the Monkey Island series with the mermaids and mermen. Mermaids are fairly exotic and beautiful as a sailor might expect, but there's a problem—telling them apart from the mermen can be quite difficult for outsiders. All merfolk look pretty much the same and there's no external dimorphism between sexes, so if a Human man mistakes a Merman for a Mermaid, you can expect a squicky situation.
 * Orcs in the Russian MMO Allods Online are dimorphic enough to give WoW's draenei and trolls a run for their money. The males are hulking, hunched brutes with huge tusks; the females are athletic-looking gray-skinned women with Cute Little Fangs.
 * Lineage 2 has male dwarves looking like old bearded men, albeit quite short—they are dwarves after all, while females are quintessential loli girls. Unfortunate Implications galore.
 * Though less extreme than some other examples, the insectoid Kephera of Lusternia straddle this trope. The males are about four to five feet tall, dexterous, hardy, and generally warriors; the females are six to seven feet tall, considerably more intelligent and charismatic, and much slower/bulkier due to their thoraxes. Their society is matriarchal, with one Queen having many mates.
 * The Rap Men and Rap Women in Rhythm Tengoku count.
 * Averted in Mass Effect, we do see one female Krogan but she looks exactly like a male Krogan (though she is wearing full armor). The Quarians (as far as we can tell) are just as sexually dimorphic as humans, and if we have seen any female Turians, Salarians, or Vorcha they didn't look that different from the males.
 * Although, Quarian males have more elongated helmets than the females.
 * In Breath of Fire, males of the Blacksmith Clan are hulking minotaurlike oxmen. Females look like human women with horns.
 * In the MMORPG Dream of Mirror Online, the females of the Shura race are basically foxgirls, while the males are massive walls of muscle with short, thick, hairless tails, and one small horn in the center of their foreheads.
 * Averted in Guild Wars 2 with the Asura, a race of goblin-like creatures; and the Charr, a race of fierce felines whose females could so easily have been turned into cat girls but, thankfully, weren't. The artist who designed the Charr delivered an ultimatum to her bosses: she would give the women boobs, but only if she was allowed to give them six. They went with none. The best way to tell the sex of a Charr is to look at how fluffy its tail is.
 * Also subverted with the Sylvari: as a race of Plant People who are incapable of reproducing, one wouldn't expect them to look exactly like human males and females, right down to what's under their strategically-placed fig leaf... but the Sylvari are created by a sentient tree, who deliberately copied the human form because she met a lot of humans during her own childhood. Further, their gender is completely physical: Sylvari are all pansexuals with no gender identity.
 * Played straight with the Norn, however. Males are hulking brutes with shoulders that would put WoW to shame, while females are simply tall humans.
 * In the flavor text of Ascendancy, it is mentioned that the Ofra have seventeen (17) sexes.
 * In League of Legends Yordle female look like tiny, pointy-eared, blue-skinned women with white hair- quite squat and with rather wide faces (depending on the artist) but basically humanoid. Yordle males on the other hand vary from looking like short gnome-like fellows with massive facial hair (but not blue skin) to resembling bipedal hamsters- either way they look nothing like the females. Compare Tristana with Teemo. This largely stems from them originally being 2 seperate races (Yordles and Meglings) who were retconned into 1.

Web Comics

 * Lampshaded in Sluggy Freelance, in the Years of Yarncraft MMO arc.
 * At The Heart Of It All, written by the creator of Concession featured a cute female alien who was discussing another alien race with Immy, the protagonist: "Their females look much like us, but their males are giant room-sized beasts with twelve tentacles who only think with the most primal urges of eating and reproduction..." Cut to Immy zooming off in a rocket.
 * Thuxians from Buck Godot: Zap Gun for Hire exhibit a fairly mild form of this trope, assuming that the one male and one female seen in the comics are typical examples of their sex. Thuxians look vaquely like Xenomorphs in the Alien movies (they have a similarly shaped head, no visible eyes and somewhat similar tail). Al (male) is green, the back of his head is rounded and his face is shaped so that he looks to have a large nose (he doesn't seem to have nostrils, though). Tal (female) is blue and her head looks more like that of the Xenomorphs, extending further back and not having a nose like Al has.
 * Maybe Al's just ugly.
 * "The People" in Digger are a race of bipedal, sentient Spotted Hyenas. They most certainly share the real life sexual dimorphism of Spotted Hyenas, and their culture revolves around it: the girls are Large and In Charge, but have horrific infant mortality rates.
 * In particular, firstborn children are considered to "belong to the goddess"—like actual hyenas, the first pregnancy is almost always fatal to the child. A firstborn who survives is seen as an omen and a lucky charm, a blessed person who was given back by their deity.
 * The author, Ursula Vernon, based a huge amount of the work on the real-life characteristics of the anthropomorphized animals; while the mythology is taken from real world myths and legends. Definitely someone who did the research, and did it well.
 * It helps to know that Ursula was an anthropology major in college and a post-grad student of Weird Knowledge in real life.
 * For those who don´t feel like checking The Other Wiki, that means Blood Eye´s Exotic Equipment looks almost exactly like Ed´s, only slightly smaller.
 * Not even that: Females have a blunter, more square glans penis than males: any size-difference is negligible, with neither males or females being statistically significantly better endowed than the other, and with females equipment being fully-erectable just like the males, for use in dominance displays.
 * In the now-long-defunct webcomic Evilish, mermaids have fish tails while mermen have legs with fins. This makes the former jealous because only the latter can leave the sea to venture on land.
 * In The Mansion of E, male Motihauls have tentacle-like growths on their heads, while the females look more like furless cats.
 * In Draconia Chronicles while the Dragons and Tigers females that are most prominently featured are anthropomorphic, the males of their respective races are actual full feral formed Dragons and Tigers
 * In Gunnerkrigg Court one character is a barn-sized Giant Enemy Crab while her mate is the size of a large-ish lobster.
 * Schlock Mercenary has a few sophont species with unusual for Earth reproductive adaptations. Gzeaul male and female with clothes, without clothes. But then, there are marsupial humanoid Qlaviqloids with three sexes: male, female, and muftale; the only differences visible when they are clothed are in head shape and slightly different skin tone, either may or may not be related to sexual trimorphism.

Web Original

 * In Lore Sjoberg's Book of Ratings entry for "Hostess Products", it is suggested that the cake and frosting portions of a Hostess cupcake are an example of this.
 * This picture

Western Animation

 * Truly extreme Monster Buster Club example: Grampa Smith, in his true form, looks like a sort of blue-skinned fish-fly thing with four limbs. Cathy's true form, on the other hand, has six tentacle-like limbs, white skin with pink spots, three crests on her head, and a squirrel-like tail. This is assuming that Grampa Smith and Cathy belong to the same species; Cathy may well be adopted, seeing that we never hear anything about her birth parents. Or Grandpa Smith is just what happens when his species gets old.
 * Storm Hawks—Subverted in the case of the Wallop species. As Finn says "they all look like dudes from behind"
 * Behold Mr. Mxyzptlk and his girlfriend, Gsptlsnz. Note that they're both 5th-dimensional imps with godlike powers, so it's possible that they both just choose to look that way.
 * From Wakfu, all male Sadida have their entire head, including the face, covered by green hair—and this is true for the juveniles too. The females also have green hair, but their faces are devoid of pilosity.
 * A throwaway gag on South Park has a male Gelgamek, a stocky green individual marginally larger than a male human of similar age and social standing, mention that the Gelgamek vagina is three feet wide, and filled with razor-sharp teeth. One can only imagine what the rest of the Gelgamek female looks like.
 * The Boudacians (Princess Mandie's species) from The Fairly OddParents.
 * In Star Wars: The Clone Wars, Female Dathomirians, which are a hybrid between Zabrak and humans, have chalk-white skin and bald heads. Male Dathomirians, however, resemble their Zabrak forefathers (like Darth Maul) with red or gold skin and horns.
 * In Adventure Time, in the episode "Her Parents" the parents of Lady Rainicorn visit Jake, and we discover that the male Rainicorns are far shorter than the female ones. And they eat human flesh.
 * In Treasure Planet the dog-man alien scientist Doppler winds up a couple with the cat-woman captain Amelia. Fair enough, just one of those soft sci-fi things. However, their children turn up in the epilogue—a litter of kitten-girls and puppy-boys. This could, of course, be Gender Equals Breed, but this trope is also a possible explanation.
 * Zane and Zair from Redakai are a minor example. Despite being siblings (therefore most likely the same species), Zane has green skin, blue hair, and darkened eyelids—while his sister Zair has light red skin, dark red hair, catlike eyes, and a strangely familiar patch of bumps on her forehead.
 * In Heathcliff and The Catillac Cats, the male Funny Animal characters are of the Civilized Animal type. Riff-Raff's girlfriend Cleo, however, seems to be a step higher on the scale, looking more like the Petting Zoo People type.

Real Life

 * Fish:
 * In some species of anglerfish, after the male attaches himself to the female, his body degenerates until only his testes remain. He ceases to exist as an independent organism, and the female has sperm on tap for the rest of her life. No surprise why the angler fish won the titles of The Most Extreme in the episodes "Oddities" and "Appendages". There's a song about it. And a small comic on it, too.
 * Whalefish and bignoses are members of the same species of abyssal fish so wildly different from one another that for the longest time, scientists thought that they were entirely different One-Gender Race species. Not only that, but they have a juvenile stage which is completely distinct from both of them and was itself mistaken for a third species.
 * Birds:
 * A great many birds have brightly colored males and plain, often larger females. In fact, the word for a male hawk or falcon is "tiercel", which comes from the french word for "one third", because male raptors are a third smaller than females. This makes a certain evolutionary sense—the female has to carry eggs, so a larger body is needed. Males can get away with being smaller (and thus needing less food) because birds generally don't physically fight except in extreme circumstances—it's too easy to hurt a wing and be crippled. Similarly, males normally are bright and females drab so that a nesting female is hard to spot but a displaying male easy to find. (There is also a theory that some species, like peacocks, are essentially advertising their fitness as a mate by showing off a major handicap—a big tail says "Hey, I can walk around with this strapped to my butt and still avoid predators! I'm an awesome provider!").
 * Peafowl are good examples of extreme difference between the sexes, as are most Galliforms (Chickens, pheasants, turkeys, etc.)
 * For an inversion of the usual trend, see the Eclectus Parrot. Males are a well-camouflaged green, females are a gaudy red, blue, and purple (Eclectuses are one of the only parrots to practice polygamy, and the females bright colors make it easier for the male to find his ladies on their respective nests). They were actually classified as two different species until (it is rumored) someone caught them mating.
 * Another odd inversion: the Phalaropes. For some reason, this group of little Arctic shorebirds have reversed the usual avian gender roles. Females are brightly colored and fight over males, who are drabber and stay with the nest. They have been described elsewhere as "an entire Genus of Wholesome Crossdressers."
 * The huia, a strange bird native to New Zealand which was driven extinct by overhunting, had an entirely unique form of sexual dimorphism. The male and female had the same feather markings, but their beaks were shaped very differently. They had separate niches and ate in different ways: claims that they had to work as a team to eat are based on a misunderstanding.
 * For birds of prey size dimorphism is common: since females need to lay eggs and sit on them for a while, they are larger. Often it's much more pronounced, especially among the raptors who mainly eat other birds . The reason is that sufficient size disparity makes males and females more fit to hunt different species, and if they don't compete for food, they can share the territory without either depleting it or extending more than necessary. Smaller size is more of an advantage when chasing very fast and/or agile prey, while the larger female can catch and carry larger prey, and have plenty to feed her chicks.
 * Snakes are very rarely dimorphic, but some species of constrictors have a similar size discrepancy to birds of prey, for similar reasons.
 * Inversion: Female Spotted Hyenas have identical-looking genitals to males, with a "pseudopenis" and "pseudo-scrotum".
 * Very common among arthropods:
 * Spiders are infamous for examples of extreme dimorphism between the sexes. There is a tendency of the males to evolve into wanderers, spending their lives looking for more sedentary, web-bound females, resulting in them evolving to very different lifestyle requirements. For instance, in this picture of a Golden Silk Spider, the two spiders are the same species, with the larger being the female.
 * Male Salticids (jumping spiders) are often brightly colored and have very large "boxing glove" pedipalps in front, while females are brown or gray with small palps (P. audax, a common lab spider, is an exception to the color rule). Probably because Salticid females are very aggressive hunters, some species' males do elaborate (and hilarious) dances to increase the probability that females will recognize them as a mate rather than a snack.
 * In some species, the male will, after starting the process of sperm transfer (which is typically done with a pair of LEGS, spiders are weird), rotate their abdomen up toward the female's head and try to get her to EAT HIM. This is advantageous for the male, because it will provide her with valuable nutrition when she's finishing up the eggs he's fertilizing and putting them in their egg case. Given the longevity of these male spiders, and the travel time to the next female, he's extremely unlikely to ever encounter a second female anyway.
 * Scale insects are even more extreme than the spiders in terms of body-dimorphism. As juveniles, males and females look much alike, but when the females mature, they sink their mouths into a plant and become something that looks less like an animal than a wart. Mature males develop wings and fly around looking for females (for a few days, before they die).
 * Even more so than the scale insects, barnacles of the genus Sacculina are... unusual. Males are free-living, wandering animals that don't resemble typical barnacles at all. Females resemble neither barnacles nor the males. As adults, the females parasitize female crabs and look like a generic mass of cancerous tissue rather than a separate animal at all. The adult males also discard their crustacean exoskeleton and implant themselves into the females, becoming basically a packet of sperm. here's a site to read more about Sacculina...
 * Fig wasps. Males are tiny compared to females and wingless.
 * Bagworm moths. The females are wingless, eyeless, near-legless breeding machines. The male moth mates with the female while she is still in the cocoon, and in some species, particularly the asexually-reproducing ones, the young hatch out of the female Alien style.
 * Eusocial insects have sexual trimorphism, the reproducing females look different than the Worker females, which look different that the males.
 * Ants and termites specialize further, so there are reproducing males, reproducing females, workers, and soldiers. And sometimes weirder variants, like living "cisterns".
 * The adult females of some species of firefly are virtually indistinguishable from the larvae (i.e., grubs), while only the males are the elongated beetles we all know and love.
 * Siafu/Driver Ants. The females are not small for ant standards (being about an inch long). The male is about the size of a large sausage, hence the term "sausage fly" for him. The "sausage" part is a bloated abdomen that makes them look like very obese dragonflies. This abdomen? Contains sperm. It Gets Worse. When they breed the females release a pheromone that attracts the male, who usually have nothing to do with the females (for good reason!). The females chew off all his limbs. Then they rip open his belly and impregnate themselves with the contents while the male lies dying.
 * Inverted by various functional hermaphroditic species, in which "male" and "female" exist in the same individual at once. Played with by a few species that change sex according to age; which "sex" is young and which is old usually depends on which would be more advantaged by large size.
 * Primates:
 * Humans' sexual dimorphism isn't as great as that of our near relatives. Gorilla and orangutan males are enormous compared to the females, while male and female gibbons sport different colors of fur, plus an inflatable throat pouch for males of some species. It's even more extreme in the larger monkeys, such as baboons, mandrills, or proboscis monkeys.
 * Boobs! Er, to elaborate, human females are about the only creatures with naturally permanently swollen breasts, and they don't even need to become pregnant for them to get like that (pregnancy just swells them more). Other mammalian females have rather flat teats until they get pregnant. (Though some human women don't grow much in this area, either.)
 * Also, human male penises are gigantic compared to other primates (yes, even your Teeny Weenie is massive compared to a gorilla's), leading some to believe that before the advent of clothing they, like human breasts now, served as a sexual display in addition to their other functions.
 * The recently discovered fossil of an adult male Australopithecus afarensis revealed him to have been five to five-and-a-half feet tall. Compared to his female conspecific Lucy, at three-and-a-half feet, this is quite a substantial size difference between sexes, even if it's assumed he was tall and Lucy was short for their species.
 * Elephant seals, whose males are about 3-4 times bigger than the females, and have a proboscis-like snout (hence the name).
 * Male rotifers (a type of freshwater zooplankton) are barely a quarter the size of females, and are so single-mindedly dedicated to mating that they don't even have mouths. The males starve to death after only a day or two, whereas the females (which eat algae) last a week or more after hatching.
 * Like spiders, some species of octopus have much larger females. An extreme example is the argonaut, where the female is about 5 times larger than the male, and secretes a calcareous egg case that looks like a nautilus shell, using a pair of highly-modified tentacles.