Stuff you can find and easily identify is
Dolphin & Porpoise Teeth
For every 100 or so shark teeth, you'll find a "porpoise" tooth. As you can see in the picture below, they vary greatly in size and shape. The largest tooth in the picture measures 30mm. The shortest 12mm. I am still bewildered by the variety of these teeth. It's almost like each of them is unique in size or shape. Maybe there are even a few crocodile teeth in there?Though most people call these "porpoise" teeth, the teeth of modern porpoises are very different from those of dolphins. Porpoise teeth are spade like, and all the teeth from Brownie's Beach are more or less conical, though not as simple as those of modern dolphins. This confused me for quite some time, until I realized that 20 million years ago, dolphins and porpoises as we know them today still had to evolve. We are looking at the remains of their (common) ancestors and of now extinct branches.
sampling of "porpoise" teeth, ranging from 12-30mm in length
I believe the bone fragment in the picture below is a split piece of the jaw or "mandible" of a dolphin. The picture is on the same scale as that of the teeth above, so the thicker teeth could fit...
split fragment of dolphin jaw
Squalodon Molar
Two views of a Squalodon molar. Actual height 32mm. Root tips, the apex and coarse serrations have worn off. Remaining clay fills the space between the two roots. The wrinkles on the surface of the crown are so characteristic that you can identify even relatively small fragments of squalodon teeth by them. |
The Squalodon (no "t") is an extinct species of toothed whale. Until I found the posterior tooth or molar shown here, I'd never heard about them, and I had to ask another collector on the beach what it was:
Squalodons were the last of the primitive whales characterized by having different types of teeth. Modern toothed whales and dolphins are homodont, that is all teeth have the same shape. Squalodon was heterodont.
The Geology
Museum of the University of Wisconsin-Madison has a nice picture of
a cast of a Squalodon skull online.
Seal Molar
Seal material is much rarer than porpoise or whale. The
(distributions of) pores
in seal bones are slightly different from those in porpoise
and whale bones, and after a lot
of experience you may be able to tell fragments apart, but I'm
not there yet. I do have one complete seal tail vertebra, and
the crown of a small (10mm wide) seal molar (see figure).
Ear bones
Cetaceans' earbones come in pairs, the periotic, and the tympanic. We humans have three: hammer (malleus), anvil (incus) and stirrup (stapes). But I have no clue how these relate to each other. Unlike nearly all other bones, earbones are solid, and do not show the characteristic sponge pattern. We've thrown away many fragments mistaking them for pieces of flint or other stones. But once you find one that is reasonably intact, it will be immediately clear what it is. Both have a unique shape. The tympanic is often described as a cauliflower ear, though often the cauliflower part has worn off, and all that is left is a rather smooth elongated stone. The periotic includes a peculiar ball-shape, with several holes and spiral patterns.Below are three examples of periotics. All the pictures are on the same scale(!), and the sizes are given in the captions. The larger one is probably a whale's, the other dolphin or porpoise.
two views of damaged whale(?) periotic. The white circles are the remains of modern barnacles I had to peel off. Max. dim. 55mm
left: perfectly preserved porpoise periotic (35mm). right: slightly worn and much smaller periotic (20mm) |
Three slightly worn tympanics. I don't know whether
these belong to the right or the left ear.
There are no pores in the bone, and the
more worn specimens look like elongated flint pebbles.
(scale in cm/mm)
Vertebrae
Half an axis, missing a process. The bulge on the (invisible)
far side fits in the atlas. This side attached to the 3rd cervical.
Dimensions: height: 90mm, width 70mm, depth 35mm.
|
From the head down, vertebra are called cervical (neck), thoracic (ribs) lumbar (abdomen), and caudal (tail). The first two cervical vertebra are the atlas and the axis. In humans, these allow the head to shake and nod. The cervical vertebra are very compressed (short) and sometimes fused together. Dolphins push themselves through the water with their tails, which may explain why they developed these short and stiff necks. Thoracic, lumbar and the first caudal vertebrae are very similar, with dorsal spines and other processes.
Along the backbone, the various processes vary in size and position,
which allows us to tell their approximate position. You can tell a
perfectly preserved thoracic from a lumbar by the presence of the
articulations where the ribs connect to the vertebra. The last caudal
vertebrae have no processes (figure). But since processes wear and
break off easily, all you often find is a hard to classify centrum.
Two cervicals. Recognizable by their flatness ( not visible in picture), and the location of the processes.
Left: width: 36mm, height: 26mm, depth: 7mm.
Right: width: 55mm, height: 35mm, depth: 24mm.
A nearly complete vertebra. Note the recent breaks in the processes. Though detached, both epiphyses were found with the vertebra. Max. width: 16.5cm, length 6.5cm.
 Above: a badly worn caudal (tail) vertebra. (length 7.5cm) |
  Two views of a detached epiphysis (40×45mm). The crinkled side is where it was attached to the vertebra. In older animals the epiphyses are fused to the vertebra. |
Ribs
Nearly all the round or flattened and elongated pieces of bone you
will find are fragments of dolphin or seal ribs. The problem is that
you really can't tell what they are without a well preserved end. And
the ends are just the weakest part of many bones, so it is rare to
find a bone with an intact joint or articulating face. But, for every
few hundred meaningless chunks of bone, you will find one that you can
classify. The example shown here looks to me like the end of the
second rib of a seal. On the right, you can see the two faces were it
articulated with a dorsal vertebra.
Flippers
Like the human arm, dolphins and seals have one upper flipper bone (the humerus), and two lower flipper bones (the ulna and radius). The pictures below show examples of each of these, though they definitely do not belong to the same animal, and probably not even to the same species! Their sizes also don't match.
Two views of a worn humerus. In the left picture you can still see part of the ball-joint that articulated with the shoulder blade (scapula). On the far right you can see the two facets of the joint, where it articulated with both the radius and the ulna. (length 59mm)
A badly damaged ulna. The left side articulated
with the humerus, but it is missing a large extension towards the
bottom left. (length 62mm)
Bottom: same radius seen end-on. (length 58mm)
Left: two views of the proximal end of a radius.
Note the deep parallel gouches on both sides. It looks like this flipper spent
a few seconds between the jaws of pretty large shark!
