Seven vertebrate classes: heart chambers, scales, air bladder and the exceptions I keep forgetting
Rahul DubeyDropper Sample
12 Oct 2026 · 1 min read
Third attempt. I read Animal Kingdom again this morning at 5 am with my chai, and the chapter that was always "easy" is the one where I quietly lose marks. Animal Kingdom questions are mostly exceptions, and I know the rules but not the exceptions.
I want to build one table for the vertebrate classes: Cyclostomata, Chondrichthyes, Osteichthyes, Amphibia, Reptilia, Aves, Mammalia. For each: skin covering, respiration, heart, body temperature, fertilisation, and an example.
I have these half-done:
- Fishes: two-chambered heart (one auricle + one ventricle), cold-blooded.
- Amphibia: three-chambered heart.
- Aves and Mammalia: four-chambered, warm-blooded.
- Reptiles: I wrote 3-chambered, but I have a feeling there's one exception.
What I do not have: which fish has an air bladder and which does not (and what happens to the one without), who has operculum, who is oviparous or viviparous, and the Cyclostomata details. Also "cartilaginous vs bony" examples. If someone has these in a tidy format that would help me a lot, I'm too tired to build it from scratch.
7 answers & replies
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[+][–]Ishita GoyalDropperSample· 8d ago
Table time:
Class Skin Respiration Heart Temp Example Cyclostomata no scales gill slits (6-15 pairs) - cold Petromyzon, Myxine Chondrichthyes placoid scales gills, no operculum 2 cold Scoliodon, Pristis Osteichthyes cycloid/ctenoid scales gills with operculum 2 cold Labeo, Catla, Hippocampus Amphibia moist, no scales gills, lungs, skin 3 cold Rana, Bufo, Salamandra Reptilia dry, scales/scutes lungs 3 (4 in crocodile) cold Calotes, Naja, Crocodylus Aves feathers lungs + air sacs 4 warm Corvus, Columba Mammalia hair lungs 4 warm Rattus, Elephas [+][–]Rahul DubeyDropperSample· 7d agoAuthor
brilliant, Ishita. One last fix I want to note: Ichthyophis is amphibian, not a snake, even though it's limbless. Saving this table, thanks all. going to sleep a bit before the 5 am reading again
[+][–]Siddharth RaoDropperSample· 8d ago
Fish details: Chondrichthyes have no air bladder, so they must keep swimming constantly to avoid sinking. Mouth is ventral, notochord persists, gill slits are separate (5 to 7 pairs, no operculum). Many are viviparous, fertilisation is internal. Osteichthyes have an air bladder that regulates buoyancy, 4 pairs of gills covered by an operculum, mostly oviparous with external fertilisation and direct development. So cartilaginous = shark/ray (Scoliodon, Pristis), bony = Rohu (Labeo), seahorse (Hippocampus) and flying fish (Exocoetus).
Cyclostomata: jawless, with a circular sucking mouth, 6 to 15 pairs of gill slits, no scales and no paired fins, and a cartilaginous skeleton. They are ectoparasites on fishes. They go to fresh water to spawn, die after spawning, and the larvae return to the ocean.
[+][–]Pooja Iyer12thSample· 8d ago
Reptiles: dry cornified skin with scales or scutes, lungs for breathing, and a three-chambered heart, all of them. Also snakes and lizards shed their scales as skin cast, and the ear is represented by a tympanum. Reptiles lay eggs with tough covering, and there is no larval stage, they have direct development.
[+][–]Siddharth RaoDropperSample· 7d ago
Pooja, "all of them" is the trap. Reptiles have a three-chambered heart usually, but the crocodile has four chambers. That's the exception NEET likes: "reptiles three-chambered, crocodile four".
[+][–]Kavya NaikDropperSample· 7d ago
For Aves: forelimbs modified into wings, beak, skin is dry with no glands except the oil gland at the base of the tail, long bones are hollow with air cavities (pneumatic bones), crop and gizzard in the digestive tract, lungs with air sacs. Mammals: mammary glands (the defining feature, hence the name), hair, external ears (pinnae), different types of teeth, mostly viviparous. Some are exceptions: Ornithorhynchus (platypus) lays eggs, so it is an exception to "mammals are viviparous", and Macropus (kangaroo) gives birth to a very immature young that develops in a pouch.
[+][–]Mehak AroraDropperSample· 7d ago
Amphibia details so you don't need to search: alimentary canal, urinary and reproductive tracts open into a common chamber called the cloaca, which opens to the exterior. Fertilisation is external, they are oviparous, and development is direct or indirect (tadpole in frogs). Eyes have eyelids, and the ear is represented by a tympanum. Examples: Rana, Bufo (toad), Hyla (tree frog), Salamandra and Ichthyophis (limbless amphibian).
