Fossil of the day #6

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Today’s fossils are from the trip to Colorado:OLYMPUS DIGITAL CAMERA OLYMPUS DIGITAL CAMERA

Neither of these pterosaur trackways (the left from Utah Field House of Natural History, Vernal, and the right one from Dinosaur Journey, Fruita) were identified, and I suppose it is largely impossible to do so anyway. What is typically done is to describe what is known as an “ichnospecies” name (see e.g., Lee et al., 2010).

An ichnospecies is simply a name for a track fossil that hasn’t been associated with a specific track-maker. The trackways in the photos, for instance, appear to be quite distinct, and assuming that this is not a case of one being made by a juvenile and one by an adult (which may very well be the case), it would be useful to be able to refer to these as two different things, made by two different species of pterosaur. If we find more footprints of the same type as in the left photo, but from Ohio instead of Utah, we’d be able to say that the same species (or something very similar) probably occurred across a larger range than just Utah, and we’d be able to refer to this by a specific name. Many of the earliest fossils we have are all ichnofossils, as the animals had no hard parts that could be preserved.

I don’t know how ichnospecies-names are treated taxonomically, though. Do they have priority over traditional names is they are ever somehow positively connected to a specific species of track-maker?

References:

Lee, Y.-N., Azuma, Y., Lee, H.-J., Shibata, M., Lü, J. (2010). The first pterosaur trackways from Japan. Cretaceous Research, 31: 263–273.

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