This page is for providing the core facts about the Nido family straight from the official source. However, this is not to be regarded as an encyclopedia page that documents everything each game writes.
Due to "Nido Indifference" in flavor text (ex. see Nidoran Male), I have summed it up from the 1st generation games to the 5th rather than posting repetitive entries. In spite of that, I've included factual anatomy info that the Pokedex (or any other website) excludes. This comes in handy mostly for artists (or the biologists among us).
Click a Nido above to view their stats and information.
Name: Nidoran♀/ニドラン♀
Pokedex # (National Dex): 029
Type: Poison
Species: Poison Pin
Gender: Female (100%)
Height: 1'04'' (0.4 m)
Weight: 15.4 lbs (7.0 kg)
Abilities: Poison Point/Rivalry
Flavor Text: Even tempered, she'll avoid confrontation. Caution should be used, however, due to the highly toxic thorns covering her body. For self defense, she will attack using her small but potent horn.
Anatomical features
Horn: Yes
Predominant tooth type: Overbite with incisors
Ear protrusions: 2
Spots: Yes
Spine count: 2
Foreleg claws: 2
Hindleg claws: 2
Tail: No*
Misc: The only Nido with whiskers
Footnote: Officially, Nidoran has been seen with a tail in her Pokemon Pinball artwork, but she also has 3 ear protrusions. Possibly mixed up with Nidorina. The tail could also have come from using older Sugimori art as a reference.
Further info: Nidoran Female
Name: Nidoran♂/ニドラン♂
Pokedex # (National Dex): 032
Type: Poison
Species: Poison Pin
Gender: Male (100%)
Height: 1'08'' (0.5 m)
Weight: 19.8 lbs (9.0 kg)
Abilities: Poison Point/Rivalry
Flavor Text: His sensitive large ears can pivot in any direction, allowing him to hear any oncoming threats from any angle. When angry, the toxic spines extend, and he will ram adversaries with his horn to inject them with poison. The larger the horn, the more toxic the Nidoran.
Anatomical features
Horn: Yes
Predominant tooth type: Overbite with incisors
Ear protrusions: 6
Spots: Yes
Spine count: 10, 3 spines on 2 outer columns surrounding 4 larger ones in between
Foreleg claws: 2
Hindleg claws: 2
Tail: No
Misc: Inner ear is not divided. A trait shared only with Nidorino
Further info: Nidoran Male
Name: Nidorina/ニドリーナ
Pokedex # (National Dex): 030
Type: Poison
Species: Poison Pin
Gender: Female (100%)
Height: 2'07'' (0.8 m)
Weight: 44.1 lbs (20.0 kg)
Abilities: Poison Point/Rivalry
Flavor Text: Nidorina has a tender, social disposition, retracting the poisonous thorns on her body around family and friends. She will also tend to her kits, if any. However, she becomes nervous if alone, and will resort to biting, scratching and ultrasonic sound if antagonized.
Anatomical features
Horn: No*
Predominant tooth type: Fangs
Ear protrusions: 3
Spots: Yes
Spine count: 4
Foreleg claws: 3
Hindleg claws: 3
Tail: Yes
Misc: She is the only female heavier than her male counterpart, the only non final Nido to have a tail, and can switch from quadrupedal movement to bipedal with ease.
Footnote: Official artwork varies, sometimes she's completely without horn, others she has a small lump as if she bumped her head, possibly the start of horn growth.
Further info: Nidorina
Name: Nidorino/ニドリーノ
Pokedex # (National Dex): 033
Type: Poison
Species: Poison Pin
Gender: Male (100%)
Height: 2'11'' (0.9 m)
Weight: 43.0 lbs (19.5 kg)
Abilities: Poison Point/Rivalry
Flavor Text: Nidorino has an irate disposition, and will attack with little provocation. Like the male Nidoran, he has sensitive ears to pick up on intruders. When attacking, he'll raise the spines on his back and then charge forward. The horn is strong enough to pierce diamond, and will ooze poison upon impact.
Anatomical features
Horn: Yes
Predominant tooth type: Fangs
Ear protrusions: 2 points, 5 altogether counting non tapered bumps
Spots: Yes
Spine count: 5
Foreleg claws: 3
Hindleg claws: 2
Tail: No
Misc: Inner ear is not divided. A trait shared only with Nidoran male
Further info: Nidorino
Name: Nidoqueen/ニドクイン
Pokedex # (National Dex): 031
Type: Poison/Ground
Species: Drill
Gender: Female (100%)
Height: 4'03'' (1.3 m)
Weight: 132.3 lbs (60.0 kg)
Abilities: Poison Point/Rivalry
Flavor Text: Nidoqueen is completely covered with needle like scales, which rise when in danger. She shows no signs of backing down if attcked, and uses her bulk to her advantage both offesively and defensively. The lives of her offspring are of highest value, and will put her own life on the line for them.
Anatomical features
Horn: Yes, 2 if not counting the one on top of her head as a spine
Predominant tooth type: Fangs, visible in early art
Ear protrusions: 1 point, 2 if counting a slight lump where the ear bends
Spots: No
Spine count: 4, 5 if counting the one on top of her head as a spine
Foreleg claws: 3
Hindleg claws: 2
Tail: Yes
Misc: She has a primate-like torso. Visually, the front of her body appears as a sort of faux bathing suit.
Further info: Nidoqueen
Name: Nidoking/ニドキング
Pokedex # (National Dex): 034
Type: Poison/Ground
Species: Drill
Gender: Male (100%)
Height: 4'07'' (1.4 m)
Weight: 136.7 lbs (62.0 kg)
Abilities: Poison Point/Rivalry
Flavor Text: Nidoking specializes in melee combat, using his thick arms, legs, and tail. The tail alone is powerful enough to break bones, snap telephone poles and topple transmission towers. His rock-hard hide protects him like armor. If Nidoking goes on a rampage, there's no chance of stopping him.
Anatomical features
Horn: Yes
Predominant tooth type: Fangs with slight underbite
Ear protrusions: 2-3 (varies)
Spots: No
Spine count: 6
Foreleg claws: 3
Hindleg claws: 1
Tail: Yes
Misc: Has a primate-like torso/body despite having dinosaur like characteristics. Because of this and many other conflicting physical features, it's less taxing to identify Nidoking as little more than a "monster".
Further info: Nidoking
