Spongiform Bone On Stegosaurus And Its Purpose?

[ynot]

Hey Y'all,

I heard a theory that the plates on a stegosaurus are used for heat collection / dissipation.

It seams to make an animal very vulnerable to have such a weak thing exposed to that extent.

When I look at the examples of spongiform bone in extant animals that type of bone is always underlying a keratin growth ( fingernails, beaks, claws....).

Could it be possible that dinosaurs with a spongiform bone actually had a keratin growth on that area of their bodies? Could critters like triceratops, boneheads and stegosaurus have had a keratin shield growing over parts of their bodies to make them less vulnerable to attack?

Does anybody have any ideas on this?

Tony

[Auspex]

From a biological standpoint, protection from predation is not at the top of the list with regards to physical adaptation. There is much more to being and remaining alive as a species. I have strong doubts that sheathing 'vulnerable' parts with keratin would be worth the metabolic cost. Every adaptation must do several things well and nothing detrimental for it to persist.

[ynot]

There are some birds and lizards that have a bright coloration to their keratin, which is used in mating. Also Big horn sheep use it as a battering ram. Perhaps the term of "protection" was the wrong thing to say.

I still think it is odd for an animal to have such a weak exposed area of spongiform bone on their body.

[starman]

Stegosaur plates could've evolved just to make the creature look more formidable (same might've been true of the Spinosaurus sail). Pachycephalosaurs probably just fled or hid and didn't need body protection. Triceratops faced its enemies and didn't require much protection other than its bony frill. Stegosaurus had some osteoderms besides its plates, and these helped protect it albeit not as well as ankylosaur armor.

[ynot]

My thought is that to have an exposed area of the body that is made of unprotected blood filled bone would make the animal very vulnerable to attack, unless there were some sort of a cover on this area.

Tony

[Troodon]

Stegosaurs lived an awfully long time so their adaptation worked. Their primary method of defense was their tail spikes. The use of the plates will continue to be pure speculation until we see one walking around.

Attached picture of one from my collection from the Morrison fm of Wyoming .Almost 24" wide.

[starman]

Stegosaurs lasted a long time but had to evolve drastically and still weren't as successful as other groups. They appear absent from most parts of the world by about mid EK. As studies have shown, the thagomizer was the primary means of defense. I doubt the plates evolved for thermoregulation; none of their contemporaries needed anything like that. Carpenter believed they just made the beast look more formidable, which makes sense.

[Auspex]

It is pretty hard to grasp their purpose, since there are no analogous structures extant today, or even in the fossil record.

(Love the Gary Larson 'Far Side' reference!)

[starman]

It is pretty hard to grasp their purpose, since there are no analogous structures extant today, or even in the fossil record.

In fact at least one sauropod, Amargasaurus, had spikes on its cervicals and anterior dorsals. It is reminiscent of stegosaurs such as Dacentrurus.

Edited July 29, 2015 by starman

[ynot]

Which brings us back to the vulnerability of an exposed spongiform bone without a keraton cover?

Tony

[starman]

Other structures like horns and claws are thought to have had a keratin cover or sheath so certain osteoderms may have too.