For instructions on how to view the PDF, please see
How to Use This Orca Bone Atlas

For instructions on how to view the PDF, please see
How to Use This Orca Bone Atlas

The Orca Project: Orca Bone Atlas


HOPE was a transient orca who beached herself in Washington state in 2002. The image below was made by assembling digital scans of her individual bones. Run your cursor along the skeleton and notice that different sections change color. Click on the section you’re interested in. Then you can examine any bone in detail by clicking on its number.

Whole Skeleton with Labels Chevrons and Pelvis Ribs and Sternum Flipper Head Spine Cervical Vertebrae Thoracic Vertebrae Lumbar Vertebrae Caudal Vertebrae

The skeleton supports and protects organs and soft tissue of the animal. It also determines the animal's size, shape and movement.
Whale with Labels


Orca Spin with Labels

Thoracic Vertebrae Cervical Vertebrae Lumbar Vertebrae Caudal Vertebrae

The spine is made up of 67 vertebrae that support large muscles allowing the orca to move. Discs between the vertebrae control the flexibility and type of motion possible in different sections of the spine. The vertebrae also protect the nerves and blood vessels running the length of the orca’s body, from head to tip of tail. Holes in the vertebrae form a channel through which these vessels run.







Orca Head

Click on a specific bone from the list below to view the actual scanned rendering of that bone.

1. Skull
2. Bulla
3. Right Cochlea
4. Basihyoid
5. Right Stylohyoid
6. Left Mandible
7. Right Mandible


Orca Head Melon The orca skull, like ours, holds the brain and main organs for seeing, hearing, smelling, and tasting. Orca eyes are on each side of the head, just above the corner of the mouth. The eyes aren't especially large since orcas use sound more than vision while hunting and navigating underwater. Orca ears are just small openings directly behind the eyes. Unlike our ears, they have no exterior flap of skin. Notice the bump on the "forehead" of this photograph of an orca.  

That bump is a fatty organ called the melon. The orca can change the shape of its melon to focus and direct the echolocation clicks it uses to hunt food and identify objects underwater. Since the melon has no bones, it doesn't appear in the scanned image of the boney skull.  

Lower Jaw

Orca Teeth

The orca's lower jaw is made up of two large bones called mandibles. Each is filled with special sound-transmitting fat that allows underwater sound to be carried to the ear bones in the skull. HOPE's upper and lower jaws together hold a total of 46 teeth – 22 upper and 24 lower. These cone-shaped teeth interlock like a zipper when the orca closes its mouth. The teeth can pierce the skin of a marine mammal being attacked and also enable the orca to tear off pieces of meat. The tongue then pushes the food into the back of the mouth, where it's simply swallowed. Orcas don't chew their food at all.

Hyoid Bones

The hyoid bones are attachment points for the orca's large muscular tongue. They also support the muscles that move food into the back of the mouth and control swallowing.

Cervical Vertebrae

Cervical Vertebrae

These 7 "neck" vertebrae determine how much the orca can move its head independent of its body. Surprisingly, giraffes, mice, humans and orcas all have the same number of cervical vertebrae – just 7 – but they vary in size and ability to move. HOPE's 7 cervical vertebrae are fused into two groups – one group has 3 fused vertebrae and the other has 4 fused vertebrae. Like all other orcas, HOPE had almost no motion in her neck at all.

Click on a specific bone from the list below to view the actual scanned rendering of that bone.

8. Cervical Vertebra 1-3
9. Cervical Vertebra 4-7

Thoracic Vertebrae

Thoracic Vertebrae

Orca Twisting These 11 "chest" vertebrae are the bones to which the ribs are attached.
Their prominent vertical parts support large muscles that allow the orca to twist and flex.

Click on a specific bone from the list below to view the actual scanned rendering of that bone.

10. Thoracic Vertebra 1
11. Thoracic Vertebra 2
12. Thoracic Vertebra 3
13. Thoracic Vertebra 4
14. Thoracic Vertebra 5
15. Thoracic Vertebra 6
16. Thoracic Vertebra 7
17. Thoracic Vertebra 8
18. Thoracic Vertebra 9
19. Thoracic Vertebra 10
20. Thoracic Vertebra 11

Lumbar Vertebrae

Lumbar Vertebrae

These 11 "lower back" vertebrae mainly control the orca's up and down swimming movements. This section can't twist at all.

Click on a specific bone from the list below to view the actual scanned rendering of that bone.

21. Lumbar Vertebra 1
22. Lumbar Vertebra 2
23. Lumbar Vertebra 3
24. Lumbar Vertebra 4
25. Lumbar Vertebra 5
26. Lumbar Vertebra 6
27. Lumbar Vertebra 7
28. Lumbar Vertebra 8
29. Lumbar Vertebra 9
30. Lumbar Vertebra 10
31. Lumbar Vertebra 11

Caudal Vertebrae

Caudal Vertebrae

Orca Fluke 24 bones form the tail section of the orca's spine, running from the pelvis to the notch in the tail.

Strong muscles along the caudal vertebrae and the chevrons beneath them control the movement of the 6-foot wide tail, used in swimming, diving and surfacing.

Click on a specific bone from the list below to view the actual scanned rendering of that bone.

32. Caudal Vertebra 1
33. Caudal Vertebra 2
34. Caudal Vertebra 3
35. Caudal Vertebra 4
36. Caudal Vertebra 5
37. Caudal Vertebra 6
38. Caudal Vertebra 7
39. Caudal Vertebra 8
40. Caudal Vertebra 9
41. Caudal Vertebra 10
42. Caudal Vertebra 11
43. Caudal Vertebra 12
44. Caudal Vertebra 13
45. Caudal Vertebra 14
46. Caudal Vertebra 15
47. Caudal Vertebra 16
48. Caudal Vertebra 17
49. Caudal Vertebra 18
50. Caudal Vertebra 19
51. Caudal Vertebra 20
52. Caudal Vertebra 21
53. Caudal Vertebra 22
54. Caudal Vertebra 23
55. Caudal Vertebra 24

Chevrons and Pelvis

Chevrons and Pelvis


These small bones lie under the caudal (tail) vertebrae; look at the Whole Skeleton to see their placement. They serve as extra attachment surfaces for the large muscles that allow the orca to move its powerful 6-foot wide tail up and down while swimming. Most land animals don't have or need chevrons to move their tails – but a few, such as beavers and kangaroos, do have them.


The orca had 2 pelvic bones but only the bones on the right side of the orca's body were scanned. Therefore only the right pelvic bone is shown in the scanned image. The pelvis of mammals like humans, dogs and horses serves as a point of attachment for the legs and spine. HOPE's tiny remnant of a pelvis reminds us that she - and all other marine mammals - evolved from mammals that once had hind legs and walked on land.

Click on a specific bone from the list below to view the actual scanned rendering of that bone.

Chevrons 1, 2 and 3 each had two separate parts which were joined when placed in the mounted skeleton.  The rest of the chevrons were each one solid piece of bone.

56. Chevron 1a
57. Chevron 1b
58. Chevron 2a
59. Chevron 2b
60. Chevron 3a
61. Chevron 3b
62. Chevron 4
63. Chevron 5
64. Chevron 6
65. Chevron 7
66. Chevron 8
67. Chevron 9
68. Chevron 10
69. Chevron 11
70. Chevron 12
71. Chevron 13
72. Chevron 14
73. Chevron 15
74. Pelvis

Ribs and Sternum



Note: Numbers in this section refer only to the scanned right side of the skeleton. To get the correct number of ribs for the entire skeleton, multiply them by two.

Orca ribs are grouped into two sections. Closest to the head are 7 sets of two-part ribs. Each set has a long thoracic rib attached to a shorter sternal rib, which then attaches to the sternum. The flexible attachments between these ribs allow the animal to flex its rib cage as it breathes and dives. The second section consists of 4 ribs, each of which is attached to the thoracic vertebrae by strips of connective tissue. The other end of these ribs is encased in muscle tissue in a living animal but on the skeleton, these ribs appear to hang freely. They're often called "floating ribs".


Like the human breastbone, HOPE's sternum, together with the sternal ribs, form a bony "cage" that help protects the heart, lungs and major blood vessels from injury.

Click on a specific bone from the list below to view the actual scanned rendering of that bone.

75. Sternum
76. Right Sternal Rib 1
77. Right Sternal Rib 2
78. Right Sternal Rib 3
79. Right Sternal Rib 4
80. Right Sternal Rib 5
81. Right Sternal Rib 6
82. Right Sternal Rib 7
83. Right Rib 1
84. Right Rib 2
85. Right Rib 3
86. Right Rib 4
87. Right Rib 5
88. Right Rib 6
89. Right Rib 7
90. Right Rib 8
91. Right Rib 9
92. Right Rib 10
93. Right Rib 11

Right Flipper


Click on a specific bone from the list below to view the actual scanned rendering of that bone.

95. Scapula
96. Humerus
97. Radius
98. Ulna
99. Radiale Carpal
100. Middle Carpal
101. Ulnare Carpal
102. Metacarpal bone I
103. Digit I/Phalanx 1
104. Metacarpal bone II
105. Digit II/Phalanx 1
106. Digit II/Phalanx 2
107. Digit II/Phalanx 3
108. Digit II/Phalanx 4
109. Digit II/Phalanx 5
110. Digit II/Phalanx 6
111. Metacarpal bone III
112. Digit III/Phalanx 1
113. Digit III/Phalanx 2
114. Digit III/Phalanx 3
115. Metacarpal bone IV
116. Digit IV/Phalanx 1
117. Digit IV/Phalanx 2
118. Metacarpal bone V
119. Digit V/Phalanx 1


The flat paddle-shaped flippers are used to stabilize and steer the orca's body as it swims through water. The flipper consists mainly of cartilage, with only a few muscle attachments at the scapula (similar to a shoulder blade in humans). As a result, flippers don't add power to the orca's movement nor can they be used to grab prey.

The bones in an orca flipper are similar to those in a human arm and hand but function very differently. All of the bones in a flipper work as one unit. Imagine how you would use your arm if your "elbow" was locked and your "wrist" couldn't twist or rotate.

Unlike humans, orcas have no collar bone and so their scapula (shoulder blade) is held in place only by ligaments and muscles. At the lower end, the scapula is attached to the humerus (upper arm bone in humans and other land mammals). This in turn connects to two bones, (radius and ulna) which correspond to the lower arm bones in humans. HOPE had only 3 wrist bones (carpals) but other orcas may have more or fewer carpals. These bones are vestigial (no longer needed) remnants of their evolutionary past.

Attached to the carpals are 5 digits, corresponding to our five fingers. Bend and flex the fingers of your own hand and notice how many sections (phalanges) each finger has. Humans and most other land animals have 2 sections in the thumb and 3 sections in each digit (finger). But in whales, the numbers of phalanges can vary from individual to individual and from species to species. Sometimes there may be 10 or more phalanges in a single digit.

How to Use This Atlas

Want to see any part of the orca's skeleton close up?
Rotate and move a bone?
Change its color and lighting?
Get the actual dimensions of any bone?

  1. You will need Adobe® Reader® 9 or later before you can open the PDF file you just downloaded. It's easy to install the software. Click on the link to download and install Adobe Reader and follow the instructions given.
  2. Roll your cursor over the Whole Skeleton. Notice that different sections change color as you do so.
  3. Choose a section you're interested in and click on it.
  4. Select the bone you'd like to see and click on its number.
  5. A small box will appear on the screen with the name of the section, the name of the bone you selected and a scanned image of that bone. To get a large 3D rendering that you can investigate and manipulate with your mouse, click (right-click for PC, control-click for Mac) where indicated. A PDF of that image will appear in your Download folder or directly on your Desktop.
  6. Now you're ready to open the PDF and explore:
    1. Click anywhere on the image to activate it.
    2. The 3D Toolbar appears on a pulldown menu on the left.

      Adobe Reader 3D Toolbar

    3. Use the toolbar to:
      1. Spin icon Rotate
      2. Zoom icon Zoom
      3. Measure icon Measure any part of the bone
      4. Render icon Change its rendering style
      5. Background icon Change the background
      6. Lighting icon Change the lighting

If you want to compare this orca's bones with those of other marine or land mammals, visit the website of the Virtual Zooarchaeology of the Arctic Project.

About the Orca Bone Scans

HOPE stranded

The orca bone scans that form this Orca Bone Atlas were produced by the Idaho Virtualization Laboratory at the Idaho Museum of Natural History, as part of VZAP – the Virtual Zooarchaeology of the Arctic Project, funded by the National Science Foundation

During January 2011, Robert Schlader and Nicholas Clement, research associates from the Idaho group, came to the Port Townsend Marine Science Center to produce the very first digital images of an orca skeleton ever made. With the help of volunteers, they produced thousands of images that were later compiled on a computer using complex software. To learn more about details of the scanning process, visit

In describing the significance of the Orca Bone Atlas, Herbert Maschner, Director of the Idaho Museum of Natural History, said:

"You are collaborating in what we call the 'democratization of science'
– bringing knowledge to anyone who wants it."

The Orca Bone Atlas allows people all over the world to see and study orca bones via the Internet. Students, teachers, researchers and beach walkers can use this tool and the related VZAP website to identify and compare bones of many mammal, bird and fish species. The 3-D bone images can be moved, enlarged or reduced, rotated and even measured – almost as if the bones were held in the viewer's hands.

Photos by Center for Whale Research.

The Story Of HOPE

HOPE stranded On January 2, 2002, residents living on the cliff above Dungeness Spit on the Olympic Peninsula reported an orca whale, apparently dead, stranded on a low lying sandbar in a marshy area just south of the Spit.

Another orca, a male, was nearby in shallow water, alive and staying close to the dead female, thought to be its mother. Scientists and volunteers tried to escort the male orca out to deeper water, but as dark came on he remained inside the Spit, swimming sluggishly.

By the next day, scientists had identified both killer whales by the shape of the saddle patches below their dorsal fins. They were CA 189 (the female) and CA 188 (the young male), both transient orcas originally identified off the coast of California. The male was eventually safely escorted to deeper water, where he swam away. The female’s body was removed, necropsied and buried in a nearby field to let the natural decay process do most of the cleaning of the bones. Several years later, The Port Townsend Marine Science Center obtained permission from NOAA to complete the cleaning of the bones, assemble and display the skeleton of the female for use in its education and conservation programs. After hearing this orca's story, children in the Center's classes and summer camps named her HOPE.

Analysis of HOPE's remains revealed that she had the highest concentrations of DDT and PCBs ever found in an orca. Her story has led to extensive research of contaminants in marine waters and their effects on wildlife. To get complete details of HOPE's significance, her burial, bone cleaning, articulation and display, visit

Return To PTMSC Orca Project