There are two types of fish that can be quite difficult to tell apart. Firstly cartilaginous fish have skeletons composed of cartilage. Secondly, bony fish have, yes you guessed it, bone skeletons! Their biological classifications are Chondrichthyes and Osteichthyes respectively.
Chondrichthyes and Osteichthyes
There are more than 20,000 fish species in the world of the phylum Chordata and superclass Pisces. The reason for this is that more than half of the chordates are generally fishes. From this category, fishes are classified as either Osteichthyes or Chondrichthyes (bony fish or cartilaginous fish). As a result, we’re going to go through a comparison between bony and cartilaginous fish.
Telling them apart
Learning the differences between them can be difficult if you don’t know what to look for. Once you know what to look for, you’ll do it with ease.
Sometimes referred to as Teleostomi. Considered the largest class in Phylum Chordata. Widely recognized due to the characteristics:
- An endoskeleton entirely made of bone (Hence bony fish).
- Possess an anterior tip mouth opening.
- Either freshwater or marine.
- An exoskeleton made of cycloids (thin bony plates). Aligned based on whether the outer edges are spiny or smooth
- They have an operculum on either side of their gills
- They possess an air bladder that also performs hydrostatic functions
- Their tail fin is homocercal. Their fin appears symmetrical. However, their backbone passes through the upper half.
- They fertilize their eggs externally.
Some of the fish in this category include flying fish, globefish, sea horses, and eels.
Sometimes referred to as Elasmobranchii. They’re primarily marine fishes. They generally possess the following characteristics:
- An endoskeleton primarily composed of cartilage (Hence cartilaginous fish).
- An exoskeleton made of placoid (very small denticles coated with lots of sharp enamel)
- A ventral buccal cavity.
- Fins are heterocercal (non-symmetrical. Usually, the top is longer).
- 5 overly exposed gills (They do not have an operculum).
- Their mode of fertilization is through internal mechanisms.
Some of the common fish in this group include dogfish, skates, electric rays, and sharks. If you understand these differences, you’ll find it’s much easier to tell them apart!