Ray-finned fishes have a variety of interesting and complex jaw structures.

Here is the skeleton of an anglerfish

anglerfish skeleton

Here is the skull of another actinopterygian

fish skull

I am designing a large (roughly sturgeon-sized) deep-sea predatory fish. What jaw structure would be best suited for creating large suction forces to draw its prey into its mouth from a distance of several feet?

  • $\begingroup$ This looks more like a biology question to me than a worldbuilding question, have you considered posting it on the biology stackexchange? $\endgroup$
    – D.J. Klomp
    May 23, 2020 at 21:04
  • $\begingroup$ The most efficient jaw structure for a giant deep sea superpredator. $\endgroup$ May 23, 2020 at 21:15
  • 1
    $\begingroup$ I think it would help if you include that part in the question with the details you have in mind. Roughly how large is it, what is its favorite prey, is it meant for our oceans and how do you define effiency, those kind of story details. $\endgroup$
    – D.J. Klomp
    May 23, 2020 at 21:19
  • $\begingroup$ Fine, editing now. $\endgroup$ May 23, 2020 at 21:25
  • $\begingroup$ i dont quite get the question but what about catfish species type? i remember they have strong suction especially the monster one, i dont know the name but i believe its from amazon species that have the strongest suction power, beside i dont know the anatomy though, and i dont know are they stronger compare to other fish or it fit enough with your question. $\endgroup$
    – Li Jun
    May 24, 2020 at 8:40

3 Answers 3


It depends on how they live.


Actinopterygii (/ˌæktɪˌnɒptəˈrɪdʒiaɪ/), or the ray-finned fishes, constitute a class or subclass of the bony fishes.[1]

Numerically, actinopterygians are the dominant class of vertebrates, comprising nearly 99% of the over 30,000 species of fish.[2] They are ubiquitous throughout freshwater and marine environments from the deep sea to the highest mountain streams. Extant species can range in size from Paedocypris, at 8 mm (0.3 in), to the massive ocean sunfish, at 2,300 kg (5,070 lb), and the long-bodied oarfish, at 11 m (36 ft).

I think the angler fish catches prey like its cousin the bass - a sudden gulp. Teeth are to prevent prey from escaping. A bluefin tuna has a jaw like a tiger and teeth to match - for chasing down and catching active prey. Ocean sunfish suck up jellyfish.

In a group as successful, ancient and diverse as these ocean-conquering fish you will have a huge range of lifestyles and adaptations. Which tool is the most efficient, a screwdriver or a pop rivet gun or a claw hammer? Efficiency only makes sense in the context of a given task.

  • $\begingroup$ Like an anglerfish or a bass, instantly sucking unsuspecting prey into its mouth. $\endgroup$ May 23, 2020 at 19:37

16 letters, 2 words: Dunkleosteus jaws.

Dunkleosteus terrelli is a species of large predatory placoderms which occupied the niche of Apex predator in the Devonian seas. This was allowed both to their large size and, more importantly, due to its powerful Jaws. The peculiarity of said Jaws is that they allowed for dunkleosteus to have both a powerful bite and a large opening, with its Jaws being able to open up 45 degrees in 60 milliseconds. This allowed for it to create a strong enough vacuum to pull its prey inside its mouth, letting its scissor-like Jaws finish it. Your predator could likely have a very similar design, as the fact that it only went extinct after the devonian extinction event wiped it out, so it was clearly very successful.

  • $\begingroup$ How can I get a similar jaw design to evolve in an actinopterygian fish? $\endgroup$ May 23, 2020 at 21:49
  • $\begingroup$ @Praearcturus you'll need to adapt the skull to have similar opening mechanics, likely adding some sort of plated or bony "ring" right behind the skull much like the Dunkle plate, in order to allow for an imitation of the structural and muscular arrangement that enabled its jaw power (also watch the teeth, they'll need dentition similarly good at cutting unless they can force the entire prey onto the mouth, then the teeth just need to help keep it inside. $\endgroup$ May 23, 2020 at 22:37

The kind they already have

Actinopterygian evolution can be described as one long progression from the ancestral fixed-jaw condition seen in the oldest fishes (and retained in sharks, sarcopterygians, bichir) to the highly protrusible jaws seen in extant Perciformes. By turning the premaxilla into a mobile, protrusible element, fish are able to create a greater suction force which makes them more easily able to suck in prey in an aquatic environment. It's less useful for larger prey, but in those cases like barracudas and pike these fishes have re-evolved a fixed-jaw useful for snagging larger prey. Or they just get an even bigger head to such down even bigger food like catfishes and grouper do. So a large, deep-sea predatory fish would have a protrusible premaxilla similar to almost every other large, predatory teleost. It wouldn't be anything unique.


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