V drugem delu dvojne oddaje o dinozavrih razložimo, kako so dinozavri izgledali in kako so se obnašali, ne pozabimo niti na vprašanja poslušalcev.
Metamorfoza je podkast o novicah, zanimivostih in bizarnostih iz biologije organizmov. Ob sproščenem pogovoru jih z ekipo predstavi dr. Matjaž Gregorič.
V drugem delu dvojne oddaje o dinozavrih govorimo o obarvanosti, oglašanju in splošnem obnašanju ter koliko o tem sploh vemo. Presenetljivo malo vemo tudi o razmnoževanju. Prav tako razložimo njihovo toplokrvnost in operjenost, za konec pa odgovorimo še na preostala vprašanja poslušalcev.
The identity of parts of, or isolated bones from, skeletons of long dead animals is always a serious problem. Factors such as individual variation, ontogenetic maturity and sexual dimorphism are complicating factors, and if we do not have samples of animals, so that we know in more detail what these variations are, then we are on shaky ground (metaphorically speaking). So, we need to be cautious about identifying and naming rare fossils.
We need to understand the nature of the geological beds (how the bones came to be where they were found) and what taphonomic factors might have been involved before burial.
All these different factors have to be considered carefully and, in truth, we can never be entirely sure of ‘identity’ unless we have a reasonable sample of comparable material from a number of individuals collected in the same area from the same stratigraphic horizon.
There are undoubted problems created by these confounding factors. I know, for example, that one very early dinosaur-like animal is actually most likely composed of the remains of at least two, quite distinct, animals that have been assembled as if they belonged to a single animal. The recent description of Teleocrater is an example of an animal whose skeleton has been constructed from different collections of bones collected at different times – in this instance we hope that enough is known about these specimens that we can be reasonably sure that they all belonged to the same sort of creature.
This is a problem that palaeontologists are constantly concerned about when they are describing new species, and it cannot really be solved in all instances – unless lots more material can be found that allows us to know in more detail the range of variation that is found in that particular type of animal (and we don’t always have that sort of information).
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It takes careful examination of which skeletal elements are found at the same site/locality and careful comparisons with closely related species. For example, we think that all of the bones of Teleocrater go together because they were all found at the same site, are about the correct size for one individual, and all have the same preservation (color and quality). We can then see if there are any repeats in the skeleton (e.g., two right upper leg bones that are exactly the same) and that can help us understand how many individuals we have at the site. We can then use closely related species to help us ‘fill-in’ the whole of the skeleton that we did not find. Figuring out if you have younger or older individuals is another challenge and for this, we look directly at the morphology or shape of the specimens that we know go to one species. Most of the time, only size is different between differently aged individuals but we make sure that the morphology is almost exactly the same.
There are plenty of mistakes assigning bones to the same species, but this is where new specimens of more complete skeleton really help us. Making and fixing mistakes is the essence of science!
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