Chapter 1: Jaw Classes & Bite Arcs; Hinge & Slide Tells

Created by Sarah Choi (prompt writer using ChatGPT)

Jaw Classes & Bite Arcs — Hinge & Slide Tells

Heads, Jaws & Feeding Systems for Creature Concept Artists

Teeth and fangs get a lot of attention in creature design, but what really sells a bite is everything around them:

  • How the jaw hinges.
  • What arc the bite closes in.
  • Whether the jaw clamps, slices, crushes, pinches, or sucks.

These mechanics are what we’ll call jaw classes and bite arcs. They tell you how a creature eats, fights, vocalizes—and how its head needs to be built and animated.

For game‑ready creatures, this matters hugely:

  • On the concepting side, jaw classes define character, threat, and feeding niche long before surface detail.
  • On the production side, jaw hinges and slide motions inform rigs, deformation, VFX, and sound design.

In this article, we’ll look at four broad mouthpart types through the lens of jaw mechanics:

  • Jaws (vertebrate‑style)
  • Beaks
  • Mandibles (arthropod‑style)
  • Proboscises (tubular, sucking or piercing)

We’ll focus on their bite arcs, hinge types, and sliding motions, with practical notes on how to depict and hand off these systems clearly.

1. Thinking in Jaw Classes & Bite Arcs

Instead of starting with “sharp teeth = predator,” start with:

What kind of motion does this mouth make when it feeds or attacks?

Jaw class is about mechanical motion pattern:

  • Does it open like a door?
  • Clamp like pliers?
  • Slice like scissors?
  • Grind like a mill?
  • Pinch sideways like crab claws?
  • Extend outward like a straw or spear?

Bite arc is the path the biting surfaces travel:

  • Vertical clamp.
  • Diagonal slash.
  • Horizontal scissor.
  • Rotating grind.
  • In‑out stab or suction.

Hinge & slide tells are the visual clues that signal this motion:

  • Joint placement.
  • Bone or plate overlaps.
  • Skin folds and wrinkles.
  • Wear patterns and chip marks.

Designing these consciously helps your creatures feel physically plausible and makes them easier to animate.

2. Vertebrate‑Style Jaws: Clamp, Slice, Crush

Most players intuitively understand vertebrate jaws because of familiar animals and humanoids.

2.1 Basic Hinge Logic

A classic vertebrate jaw:

  • Has a fixed upper (attached to skull).
  • Has a movable lower that rotates at a hinge joint.

The hinge sits near the back of the mouth:

  • In mammals, near the jaw joint under the zygomatic arch.
  • In reptiles, often further back with extended jaw bones.

Visually, you can show the hinge by:

  • A clear pivot point behind the eye.
  • Overlapping plates or muscles that compress when closed and stretch when open.

For production:

  • This maps cleanly to a simple rotation joint in the rig.
  • Extra slide or stretch can be added with blendshapes.

2.2 Clamp Jaws (Bite & Hold)

Clamp jaws are about grip strength:

  • Thick lower jaw.
  • Deep, robust skull.
  • Teeth often conical or interlocking.

Bite arc:

  • Mostly vertical, strong closing force.

Visual tells:

  • Short snout with thick musculature (e.g., bulldog, big cats).
  • Heavy jaw muscles bulging at the back of the skull.
  • Limited gape (doesn’t open extremely wide, but closes powerfully).

Use for:

  • Predators that seize and hold prey.
  • Guard or tank creatures that latch onto targets.

Production:

  • Simple jaw rotation; lots of opportunity for muscle flex in textures and normal maps.

2.3 Slice Jaws (Shear & Cut)

Slice jaws act like scissors or shears:

  • Sharp, blade‑like teeth or beak edges.
  • Longer snout or jaw surfaces that slide past each other.

Bite arc:

  • Still rotational, but the contact point travels forward/back along the tooth row.

Visual tells:

  • Long, narrow muzzle.
  • Teeth line up like opposing blades, sometimes with serrations.
  • Jaw joint slightly offset for a subtle sliding or scissoring effect.

Use for:

  • Creatures that strip flesh, shear plants, or cut armor.
  • Agile attackers that rely on slicing hits rather than crush.

Production:

  • Rig can still be a basic rotation, but concept art may suggest slight lateral slide at full closure.
  • You can support this with corrective shapes that shift teeth alignment at full bite.

2.4 Crush Jaws (Bone‑Crackers)

Crush jaws focus on pressure, not slicing:

  • Broad, flat molars or crushing plates.
  • Short, massive jaws.

Bite arc:

  • Mostly vertical, with a deep, closing clamp.

Visual tells:

  • Wide skull across the cheeks.
  • Short snout, big jaw hinge.
  • Teeth that are thick, blunt, often chipped from heavy use.

Use for:

  • Shell‑cracking predators.
  • Herbivores that grind tough vegetation.
  • Tanky behemoths that can bite through metal.

Production:

  • Jaw rotation is again simple, but you can exaggerate jaw closing speed and stop for a sense of mass.

2.5 Hinge & Slide Extras: Unhinging & Gape

You can push vertebrate jaws into more fantastic territory by modifying the hinge:

  • Multi‑segment jaws that partially unhinge for wider gape.
  • Secondary hinges at the front snout for splitting jaws.

Visual tells:

  • Additional seams, cartilage ridges, and overlapping scales at the jaw corners.
  • Skin folds that can stretch massively.

Production warning:

  • Every extra hinge is another joint and set of deformations.
  • Reserve complex unhinging jaws for bosses and key creatures, and clearly diagram the motion in your callouts.

3. Beaks: Pinch, Crush, Scissor

Beaks are rigid mouthparts where the “teeth” are integrated into a hard keratin or bone shell.

3.1 Hinge‑Dominated Beaks

Beaks still hinge, like jaws:

  • Upper fixed, lower moving in many birds.
  • In some species, the upper beak can flex or hinge independently.

Bite arc:

  • Rotational, like classic jaws.

Visual tells:

  • Clear “hinge” region at the corner of the mouth.
  • Overlapping plates where upper and lower beak meet.

Design options:

  • Hooked beaks for tearing (raptor birds, predatory creatures).
  • Straight shearing beaks for cropping plants.
  • Crushing beaks (parrot, turtle) for nuts, shells, armor.

3.2 Scissor Beaks

Scissor‑like beaks are designed for slicing rather than clamping:

  • Thin, blade‑like edges.
  • Slight curvature so tips meet first, then rest of the edge.

Bite arc:

  • Rotational, with cutting surface traveling along the length of the beak.

Visual tells:

  • Very thin profile in side or front view.
  • Sometimes a visible overbite or underbite to create shear.

Use in design:

  • Surgical, precise predators (airborne hunters, assassin creatures).
  • Elegant, aristocratic creature designs—sharp, refined head silhouettes.

Production:

  • Jaw rig stays simple; slicing is sold through animation timing and sound design.

3.3 Multi‑Segment Beaks & Sheaths

Fantasy beaks can split or flex:

  • Sectioned beaks that open in multiple petals.
  • Sheaths overlaying a more flexible inner mouth.

Visual tells:

  • Visible seams along beak length.
  • Overlapping scales or plate segments.

Be cautious:

  • Every new seam implies motion; if it doesn’t actually move, it may feel confusing.
  • Clearly mark which segments are functional joints vs decorative plating.

Production:

  • Multi‑segment beaks require sophisticated rigs; mark priority segments and expected actions (full flower‑open vs simple clamp).

4. Mandibles: Pinch, Shear, Grind

Mandibles are jaw‑like appendages, common in arthropods and many alien designs.

Unlike vertebrate jaws, mandibles often:

  • Operate side‑to‑side, not up and down.
  • Come in pairs that meet in the middle.

4.1 Horizontal Pinch Mandibles

These operate like pliers:

  • Two opposing arms swing inward.

Bite arc:

  • Horizontal rotation.

Visual tells:

  • Clear lateral hinges at the base of each mandible, anchored to a central head capsule.
  • Mandibles sweep in toward a midline.

Use for:

  • Grabbing, holding, dragging prey.
  • Input to a secondary mouth deeper inside.

Production:

  • Requires side‑to‑side joint rotation, but relatively simple.

4.2 Shearing Mandibles

Shearing mandibles mimic scissors:

  • One mandible slides slightly past the other.

Bite arc:

  • Combination of rotation and slight linear slide.

Visual tells:

  • Overlapping edges with small notches or saw‑like serrations.
  • Joints that are slightly offset vertically.

These are perfect for:

  • Wood‑boring or armor‑cutting creatures.
  • Arthropod‑like miners or siege beasts.

Production:

  • Rigs may use rotation only and fake the slide with corrective shapes.

4.3 Grinding & Crushing Mandibles

Some mandibles close not just to pinch, but to grind:

  • Broad, tooth‑lined chewing surfaces.
  • Multiple smaller mandibles working in tandem.

Bite motion:

  • Repetitive, chittering grind or chew.

Visual tells:

  • Shorter, thicker mandibles.
  • Visible wear, chipping, and flattening of biting surfaces.

For concept artists:

  • These are great for creatures that eat tough, mineral or chitinous materials.

Production:

  • Animation can be a simple cycle of open/close with slight jitter to imply grinding.

4.4 Multi‑Layered Mandible Systems

You can stack mandibles in layers:

  • Outer armor mandibles for grabbing.
  • Inner smaller mandibles for processing.

Visual tells:

  • Nested arcs; smaller mandibles visible inside a larger gripping frame.

Be clear in your design packets:

  • What is primary for attacks.
  • What is secondary for feeding and close‑up detail.

This helps animators decide where to focus their effort.

5. Proboscises: Pierce, Suck, Sip

Proboscises are specialized mouthparts that extend outward as tubes, needles, or hoses.

They often:

  • Replace a traditional jaw.
  • Combine with small jaws or mandibles for support.

5.1 Piercing Proboscis

Designed to stab and extract:

  • Think mosquito, tick, parasitic alien.

Motion:

  • Primarily in‑out rather than open/close.

Visual tells:

  • Long, thin spear or bundle of stylets.
  • Stabilizing structures around the base (lips, sheath, or small mandibles).

Use for:

  • Blood feeders.
  • Energy vampires.
  • Creatures that tap into host or environment reservoirs.

Production:

  • Rigs driven by translation (extend/retract) plus subtle flex.
  • Often paired with VFX (fluid draw, glow pulses).

5.2 Siphoning Proboscis

Designed to sip liquids or semi‑liquids:

  • Coiled tongue, trunk‑like hoses.

Motion:

  • Coiling/uncoiling.
  • Curling, flexing, and slight thickening.

Visual tells:

  • Visible segmentation or ridges.
  • Sometimes a spiral or layered tube when at rest.

Great for:

  • Gentle herbivores.
  • Mystic or divine creatures feeding on ambient energy.

Production:

  • Requires bendy rigs (IK chains) and sometimes simulation.
  • Neutral rest pose should look stable and not overly tangled.

5.3 Hybrid Mouths: Proboscis + Jaws/Mandibles

Many designs benefit from combining:

  • An outer jaw or mandible set for grabbing.
  • An inner proboscis for feeding.

Visual tells:

  • Outer “gate” that opens to reveal inner spike/tube.

Design tip:

  • Make one system clearly primary for combat and the other for feeding/drama to avoid animation overload.

6. Hinge & Slide Tells: Selling Motion in a Still Image

Since concept art is static, you need to imply motion using structure and surface cues.

6.1 Structural Hints

Show where things can move by:

  • Drawing clear joint landmarks (ball‑like nodes, hinge bars, overlapping plates).
  • Indicating seams where shells or bones might separate.
  • Using distinct shapes for moving vs fixed parts.

Example:

  • Fixed upper jaw with smooth connection to skull.
  • Lower jaw with a clear notch where it fits under a cheekbone.

6.2 Soft Tissue Hints

Skin and soft tissue show motion range:

  • Wrinkle fans radiating from a joint show where skin compresses.
  • Stretch marks or taut surfaces over a moving bone suggest direction.

Use these around:

  • Jaw corners.
  • Mandible bases.
  • Proboscis roots.

6.3 Wear & Damage Tells

Teeth and biting edges become storytelling devices:

  • Chips and scratches indicate grinding or hard impacts.
  • Polished, worn edges show constant rubbing or scraping.
  • Uneven wear hints at asymmetrical bite arcs or misaligned jaws.

These details help art directors and animators understand how the creature really uses its mouth.

7. Concepting vs Production: What Each Side Needs

7.1 Concept‑Side Priorities

When you’re ideating:

  • Focus on jaw class first: clamp, slice, crush, pinch, grind, pierce, suck.
  • Then design a head silhouette that clearly supports that motion.
  • Use bite arcs to reinforce role:
    • Fast slicers for DPS.
    • Slow crushers for tanks.
    • Precise proboscises for status‑effect or parasitic enemies.

Your job is to make the feeding system:

  • Immediately readable.
  • Emotionally aligned with the creature’s personality.

7.2 Production‑Side Priorities

When working closer to production:

  • Simplify jaw mechanics to what is riggable and animatable on schedule.
  • Clarify neutral mouth pose and attack extremes.
  • Provide orthos that show how parts separate and slide.

In your callouts, explicitly note:

  • “Lower jaw rotates here, upper fixed.”
  • “Mandibles rotate inward and slightly forward—see arrows.”
  • “Proboscis extends 2x head length; coiled under chin at rest.”

This kind of information prevents misunderstandings later in the pipeline.

8. Practical Design Workflow

Here’s a simple workflow for designing jaws and bite arcs that hold up.

Step 1 – Pick a Jaw Class & Role

Decide:

  • Is this mouth for grabbing, tearing, grinding, piercing, or siphoning?
  • What is the creature’s combat role and feeding niche?

Write it in the corner of your page.

Step 2 – Choose a Primary Mouthpart Type

Pick one primary type:

  • Vertebrate jaw
  • Beak
  • Mandibles
  • Proboscis

You can add secondary types later, but don’t start with everything at once.

Step 3 – Sketch the Bite Arc

Before drawing teeth:

  • Draw a simple diagram: fixed part + moving part.
  • Indicate the hinge and direction of motion with arrows.

Do this from the side and, if helpful, the top.

Step 4 – Wrap Anatomy Around the Mechanic

Now design the skull, plates, or soft tissues so they:

  • Protect joints.
  • Make room for full motion (no bones colliding).
  • Support the silhouette you want.

Think about where muscles or shell anchorage would need to be.

Step 5 – Add Teeth, Ridges & Details That Match the Motion

Teeth and edges should:

  • Point into the direction of bite force.
  • Interlock or overlap in a way that makes sense for the jaw class.

Avoid random, evenly spaced teeth that don’t match how the jaw actually moves.

Step 6 – Test Poses & Expressions

Sketch a few quick variants:

  • Neutral, low‑threat mouth.
  • Half‑open warning/snarl.
  • Full bite or feeding action.

Check that the jaw mechanics you designed still feel possible from all of them.

Step 7 – Annotate for Handoff

On a clean pass:

  • Label joints, moving parts, and expected extremes.
  • Note any non‑obvious slides or unhinging.

This turns your jaw design from “cool picture” into a usable blueprint.

9. Exercises for Creature Concept Artists

Exercise 1 – One Head, Four Mouths

Take a simple base head shape (e.g., generic lizard skull) and redesign the mouth into four variants:

  1. Clamp jaw.
  2. Slice jaw.
  3. Beak.
  4. Mandible set.

For each:

  • Draw the bite arc diagram.
  • Adjust skull and silhouette to support the mechanic.

Exercise 2 – Feeding Niche Drill

Pick four feeding niches:

  • Bone‑cracker.
  • Nectar sipper.
  • Shell‑driller.
  • Blood feeder.

Design mouthparts for each using different classes (jaw, beak, mandible, proboscis). Focus on hinge placement and slide motion.

Exercise 3 – Production Callout Sheet

Take one of your jaw designs and create a production‑oriented callout:

  • Side view with hinge arrows.
  • Front view showing alignment of biting surfaces.
  • Open and closed positions.
  • Notes for rigging and animation.

Practice being as clear and concise as possible.

10. Closing Thoughts

Jaw classes and bite arcs are core to how your creatures eat, kill, and communicate. When you treat them as mechanical systems—not just places to stick sharp teeth—you unlock:

  • More grounded, believable head designs.
  • Stronger alignment between concept art and animation.
  • Clearer storytelling about niche, role, and personality.

As a concepting‑side artist, use jaw mechanics to make your creatures more expressive and functionally distinct.

As a production‑side artist, use hinge and slide tells to deliver designs that rigs and animators can actually build.

Each time you draw a new head, ask:

  • What jaw class is this?
  • What path does the bite follow?
  • Where does it hinge, where does it slide—and how can I show that in the design?

If you can answer those questions, your jaws will do more than just look cool—they’ll feel like real, functional parts of a living creature ready to exist in a game world.