Details, details

In discussions of palaeontology with non-experts one theme that often seems to emerge is the lack of appreciation of details. This is especially common with the often tedious discussions with the ‘want-to-be’ experts or those at the less sane end of the spectrum of internet commentators. I don’t mean this in a disparaging manner – it’s an observation, not a criticism, and those who really do wish to learn or understand and generally quick to realise and adapt their approach accordingly, but that real appreciation for detail is often lacking.

Details are though, critical. As seen to a degree with my posts on ontogeny and convergence, it’s easy to take a feature at face value and not examine the details and thus misinterpret it. Without looking at the details of the proboscis itself or the rest of the animal, it’s easy to make the mistake of assuming that say anteaters and aardvarks are close relatives, or that all animals with large claws must be digging or burrowing etc.

Teeth are perhaps an especially good example, though already we are delving somewhat to a detailed level when we might have two whole animals to compare. Most theropod teeth look quite similar being generally curved at the front, quite straight at the back, laterally compressed and with some degree of serrations on the carinae (a primer on teeth is here for those who missed it). You can see that they look pretty similar and that it might be reasonable to assume that they are from closely related animals doing similar things in similar ways. To a degree that’s true of course (they are, after all, theropod teeth from carnivorous members of the group), but it belies the truth of the matter. A much look closer and a myriad of details become apparent that have taxonomic and systematic importance and morpho-functional implications too. There is variation, and thus important detail, to be had here. Similar as these might look, and simple though it would be to pass them off as not worthy of further attention or irrelevant, this would be quite wrong.

Briefly then:

Tooth denticles can vary in shape, distribution up and down the tooth and between the two carinae, and vary in size along the tooth
The grooves that lie between the denticles can also vary in terms of their depth and length too.
The carinae that support the denticles can vary in size and shape too and sometimes twist around the tooth (as seen in tyrannosaur premaxiallry teeth, but not the others).
Teeth can vary in their curvature, cross-sectional shape, and degree of lateral compression (or which side is compressed)
Some teeth have wrinkles on the surface of the enamel and others don’t, though the shape and size of these wrinkles varies too. You get ornamented teeth too with big vertical ridges that may or may not be present on one or both faces of the too
Finally the shape and size of the root can vary and there can be a restriction at the base of the crown too in some teeth.

All of this is true when comparing teeth directly to one another that are directly linked (like say the 1st premaxillary tooth, or the 3rd dentary tooth). There is still more variation there though.  The number and position of the teeth in the jaws varies, and the teeth are often different in the upper and lower jaws, and the teeth can vary along the tooth row itself (theropod premaxillary teeth are often more robust than maxillary teeth, and anteiro teeth bigger than posterior ones for example).

Details then, matter. It’s not enough to look quickly at gross shapes and patterns and pronounce judgement, there are details there, often of bewildering complexity and number and they are important. To gloss over them, or not realise they are there, is to potentially lead to pitfalls of misunderstanding and incorrect deductions. They might be obvious and they might not even be discussed (I would write a monstrous piece on why birds are not pterosaurs without even beginning to chip away at the anatomical differences of the wrists and ankles for example) but they are there and we need to be aware of them.

@Dave_Hone on Twitter

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