Estimate Of Number Of Dinosaur Genera (Excluding Mesozoic Avialans)

[DD1991]

In their paper estimating the number of dinosaur diversity, Wang and Dodson (2006) estimated the generic diversity of non-avialan Mesozoic dinos at 1,844. At the current time of writing, there are 46 valid genera of Triassic dinosaurs, 265 valid genera of Jurassic dinosaurs, and 730 genera of Cretaceous dinosaurs for a grand total of 1041 valid dino genera. That leaves 800 genera left, unless Wang and Dodson overestimated the generic diversity of Late Cretaceous dinos by a few dozen. If we take into account recent research papers revalidating dinosaur genera that are usually tossed off as nomina dubia without comment in both editions of the Dinosauria (e.g. Sanpasaurus, Chuandongocoelurus, Eucamerotus, Aepisaurus, Neosodon), it seems as if the pace of naming new non-avian dinosaurs seems to be picking up a bit. Maybe we found nearly all the Late Triassic and Early Jurassic genera estimated by Wang and Dodson. Only time will tell if Wang and Dodson's estimate for Cretaceous dinosaur diversity is a little bit exaggerated. After all, we can say we found every single genus of dinosaur and completed an inventory of dinosaurs once every formation around the world is completely prospected for dino fossils.

Wang, S. C. & Dodson, P. 2006 Estimating the diversity of dinosaurs. Proc. Natl Acad. Sci. USA 103, 13 601–13 605. (doi:10.1073/pnas.0606028103)

[Ridgehiker]

'. After all, we can say we found every single genus of dinosaur and completed an inventory of dinosaurs once every formation around the world is completely prospected for dino fossils.'

Actually 'no' on so many levels.

99.99999999 of Dino's were never fossilized. Of those fossilized, formations they were preserved in could today be either eroded completely away or be a mile under the surface... these are the vast majority. Dino's lived just about everywhere...we don't find Dino fossils everywhere. One may live where there is one billion year old shield rocks on the surface....a billion years of new life never fossilized or, if it did, is long eroded.

The amount of evidence to study almost 200 million years of Dino's is like saying one would know all the movies ever made by going through a shoebox of DVDs in my garage. Not only that, but I would have a bias for certain types of movies just as there is a bias in conditions that lead to one type of vertebrate being preserved over another.

Fossilization for large organisms is very rare. There are hundreds of genera of mammals alive today. There are few conditions in which any would be fossilized....then minuscule chance of them being preserved for 100 million years and then exposed at the right time to be discovered before a surface formation is eroded.

Edited August 18, 2013 by Ridgehiker

[AgrilusHunter]

Northstar is spot on! Even if we somehow censused all available formations we would still have only a small sample of the true list of dinosaur genera. This trend holds true for most groups not just the dinosaurs, hence the hexapod gap.

[Auspex]

We will probably never know about the vast majority of Mesozoic land fauna; thin, spotty deposition of sediment is the norm in a terrestrial environment, and erosional uncomformities are prevelent (wherein much of what had been laid down is erased).

[siteseer]

That reminds me of something a friend once told me. He said that someone wrote a newspaper article in the early 1900's declaring that science had discovered just about everything in the universe.

It might be interesting to read the dinosaur article to find out how they ran the numbers - a question of paleoecology and biogeography.

In their paper estimating the number of dinosaur diversity, Wang and Dodson (2006) estimated the generic diversity of non-avialan Mesozoic dinos at 1,844. At the current time of writing, there are 46 valid genera of Triassic dinosaurs, 265 valid genera of Jurassic dinosaurs, and 730 genera of Cretaceous dinosaurs for a grand total of 1041 valid dino genera. That leaves 800 genera left, unless Wang and Dodson overestimated the generic diversity of Late Cretaceous dinos by a few dozen. If we take into account recent research papers revalidating dinosaur genera that are usually tossed off as nomina dubia without comment in both editions of the Dinosauria (e.g. Sanpasaurus, Chuandongocoelurus, Eucamerotus, Aepisaurus, Neosodon), it seems as if the pace of naming new non-avian dinosaurs seems to be picking up a bit. Maybe we found nearly all the Late Triassic and Early Jurassic genera estimated by Wang and Dodson. Only time will tell if Wang and Dodson's estimate for Cretaceous dinosaur diversity is a little bit exaggerated. After all, we can say we found every single genus of dinosaur and completed an inventory of dinosaurs once every formation around the world is completely prospected for dino fossils.

Wang, S. C. & Dodson, P. 2006 Estimating the diversity of dinosaurs. Proc. Natl Acad. Sci. USA 103, 13 601–13 605. (doi:10.1073/pnas.0606028103)

[Regg Cato]

And ultimately if we're talking about genera, then that's a whole other kettle of fish entirely, because, with the exception of some phylogenetic utility, the genus is a somewhat subjective rank that I would be in favor of abandoning entirely.

[Ridgehiker]

Regg...it's interesting you mention that as I worked with an old palaeontologist and he claimed the genus/species concept was misleading for past life....either get rid of genus or species.

Each 'in group' of researchers tend to use their own in-group criteria for genus/species. It is somewhat arbitrary and in paleontology rarely based on biology.

[jpc]

I agree that Northstar is spot on. And yes the whole concept of species and genus gets fuzzy in paleontology... heck, it is confusing in animals that we can actually see living right now. I would argue that the 1800 total is vastly underestimated, because of what Northstar has so nicely stated.

Another analogy might be to ask someone how many species of birds live in their area. Most folks might guess 20 or 30 (these folks represent the actual fossil record), unless of course they know something about birds in which case dependingon where you live is at least ten times that.