|I was thinking....... Let me rephrase my original question for the group.........
Are there any sort of scars on the ribs of tyrannosaurs...... in a row..... rib to rib.... where one would expect to see unicates? It would be silly to think that only the bone that is found is the true representatives of an animal in life. Since unicates ossify as separate elements in birds, and some birds that do have them do not even have them fused to the ribs,..... What I was asking is if there were any sign of cartilagenous unicates running in rows of scars on the ribs in a cranio-caudal manner. Given what we tend to think the airsac system was like in these animals..... and I'd like to know what exactly it is that we think....... would animals that size even need unicates to aid in the ventilation of these airsacs?
As for the sternal bit..... Right off the bat, many parts of the sternum is not bone. Only part of it is bone. This is almost always true. My understanding is that it is a well established phenomenon that the sterna in theropods ossify late in development, and if they do not have sterna, preserved for example, this only means that they were in a cartilaginous state. What is also known is that the sternal ribs of many different species simply do not ossify.... Ever. This is true for many dinosaurs, humans, and most other mammals. Only with old age might there be the beginnings of ossification.
When it particularly comes to theropods, I bet the articulation between the coracoids and sternum was cartilage. Just look at the sternum in some theropods. Look at the way some restorations try to articulate them. The limbs simply do not line up right unless you fill in the gaps with cartilage..... Upfront bewteen the coracoids, at the anterior margine of the sternum, the back of the sternum, and where the gastralia is. Such things are good indications that the sternums were longer than what was actually preserved. Yet, some still try to make them fit without doing this. I have never understood that.
A good question would be how much is usually missing from the fossilized pectoral girdles found from theropods due to parts being cartilage. Not bone not being fossilized..... but missing areas due to cartilage. This was the argument I was trying to get across. Another question would be is there variation between groups and species in this regard. Do you think Archaeopteryx had a sternum?..... and I'm not talking just the bavarica, and/or sternal ribs. Hey, Mr. Paul adds them. And really, going back to unicates, Archaeopteryx most likely had them..... they just were not bone.
I just do not like going by luck alone..... I don't go by what happens to be fossilized. For the sake of argument...... So, we have what?..... One tyrannosaur with sternal ribs?..... And this is in doubt?..... What if we never found one single tyrannosaur with sternal ribs?.... All the ones we found never, ever showed them... See what I mean? It's the same with the iguanodons. That central ossification was not just floating in space. It was in cartilage.