Difference Between Deltadromeus & Carcharodontosaurus Teeth

[AJ Plai]

I have been seeing Delta teeth floating around the net lately and was wondering how you teeth experts can tell the difference or unique features that separate one from another since most of them to my eyes, they look almost the same.

With Delta teeth of size smaller than 1.5" I can kinda see it tend to be flat and blade-like like Dromaeosaur's teeth and you probably may be more likely to get them confused with Raptor's teeth more so than Carch teeth which from my observation, the smaller teeth seem to look bulkier and a little stout in shape.

However when it comes to Delta teeth of 2" and bigger I see very little difference from a Carch tooth of similar size so how do you tell the difference? And correct me if I am wrong, but it seems like a Delta teeth of 2" and above seem to be a rarity from my experience but in reality are Delta teeth more costly than a Carch tooth of comparable size and quality? Since it seems to be a rarer specimen I would assume the answer should be yes, but I can't be sure.

[Auspex]

With the paucity of clearly associated remains, I do not know how anybody can state with any confidence which teeth go with what critter, or even what the actual faunal list is for that area. It seems like only dealers are completely free from doubt...

[Boesse]

I posted about this a while ago. People confidently identifying isolated teeth as Deltadromeus is embarassing and laughable, because Deltadromeus is not known from a skull or any teeth! That's not to say that teeth and skull parts have not ever been discovered - sure, there are possibly some that have been found, but it is impossible to tie them in with the name Deltadromeus because the type specimen is known mostly from postcrania.

Another thing to think about: the majority of theropod teeth are nowhere near as diagnostic or easy to identify as amateurs and fossil dealers purport them to be. Those of us who are doing the science itself constantly argue over what sort of identifications can and have been made, and the whole area of identifying isolated theropod teeth - just like I've talked about with trying to identify fossil dolphin teeth - is pretty murky.

So while some will point out that it's a bit problematic to identify isolated theropod teeth, I will step forward and point out that anyone attempting to use Deltadromeus for teeth at this point is already wrong on the principle that we do not have the paleontologic evidence to make such an identification; we simply do not know, and at this stage, cannot know until a fossil of Deltadromeus with a skull is found in concert with the diagnostic postcrania linking it in to the holotype.

[Ridgehiker]

Excellent wisdom in the above postings.

A theropod had a mouthful of teeth...in different positions...different stages of tooth growth....different maturity of animals.

I've found a couple of thousand and when asked to identify a theropod tooth my answer is 'I don't know'. At best one can say that certain theropods have been found in a particular formation at a particular level. However, one never knows if it is a finite group. A tooth is multiple more common a find than a tooth associated with any diagnostic skull material. A raptor tooth found in a jaw section is extremely rare.

Auspex, so true. I see raptor, hadrosaur, etc. teeth for sale identified down to the species. Unfortunately the only verifiable and most useful info is not available....specifically where it was found. Everything else is speculative and may change over the years with more study but the specific location doesn't.

[Regg Cato]

I posted about this a while ago. People confidently identifying isolated teeth as Deltadromeus is embarassing and laughable, because Deltadromeus is not known from a skull or any teeth! That's not to say that teeth and skull parts have not ever been discovered - sure, there are possibly some that have been found, but it is impossible to tie them in with the name Deltadromeus because the type specimen is known mostly from postcrania.

Another thing to think about: the majority of theropod teeth are nowhere near as diagnostic or easy to identify as amateurs and fossil dealers purport them to be. Those of us who are doing the science itself constantly argue over what sort of identifications can and have been made, and the whole area of identifying isolated theropod teeth - just like I've talked about with trying to identify fossil dolphin teeth - is pretty murky.

So while some will point out that it's a bit problematic to identify isolated theropod teeth, I will step forward and point out that anyone attempting to use Deltadromeus for teeth at this point is already wrong on the principle that we do not have the paleontologic evidence to make such an identification; we simply do not know, and at this stage, cannot know until a fossil of Deltadromeus with a skull is found in concert with the diagnostic postcrania linking it in to the holotype.

Excellent wisdom in the above postings.

A theropod had a mouthful of teeth...in different positions...different stages of tooth growth....different maturity of animals.

I've found a couple of thousand and when asked to identify a theropod tooth my answer is 'I don't know'. At best one can say that certain theropods have been found in a particular formation at a particular level. However, one never knows if it is a finite group. A tooth is multiple more common a find than a tooth associated with any diagnostic skull material. A raptor tooth found in a jaw section is extremely rare.

Auspex, so true. I see raptor, hadrosaur, etc. teeth for sale identified down to the species. Unfortunately the only verifiable and most useful info is not available....specifically where it was found. Everything else is speculative and may change over the years with more study but the specific location doesn't.

+1

Go back a number of years and you'll find a plethora of taxa all based on teeth (about a dozen species of "Megalosaurus", plus nice taxa like Dysganus, Diplotomodon, Priconodon, Leipsanosaurus, Phyllodon, Cionodon, Diclonius, etc.), all of which are considered non-diagnostic at present. As mentioned, teeth are simply not sufficiently distinct in the vast majority of taxa to be useful in identification at the genus or species level. However, from a commercial standpoint, assigning a specific genus or species to a tooth makes it much more marketable. After all, most people would rather have a Deltadromeus agilis tooth than a tooth from an indeterminate theropod.

[DD1991]

At the moment, no specimen of Deltadromeus has been described that includes craniodental remains. The only way to determine if the teeth sold under the label Deltadromeus are ceratosaurian is to compare them with the teeth of known Cretaceous ceratosaurs like Masiakasaurus and Carnotaurus. In their cladistic analysis of Limusaurus, Xu et. al. (2009) failed to recover Deltadromeus as a noasaurid, a possible sign that Deltadromeus may be more primitive than any abelisauroid.

[Boesse]

Excellent points above: especially that this highlights the fact that we should be encouraged to say "I do not know". And Regg Cato, you're right: fossil dealers identifying teeth as Deltadromeus is totally just a sales pitch. Bobby

[Carcharodontosaurus]

I'd say that it's pretty easy in some cases to narrow down a theropod tooth ID to the genus level at least. I'll list a few examples below.

1. A large theropod tooth, or a large fragment of a tooth coming from the Hell Creek Formation is usually easily identifiable as T. rex because T. rex is the only known large theropod from the formation, since dromaeosaur teeth are very small, and Nanotyrannus is thought by most scientists to be a juvenile rex.

2. A large, blade-like theropod tooth from the Kem Kem Beds in Morocco is likely to belong to Carcharodontosaurus, because Carcharodontosaurus is a common large theropod in that area, and Spinosaurus teeth look very different. Sauroniops is another possiblity, but I don't think fossils of that are nearly as common.

3. Also from the Kem Kem Beds, Spinosaurus teeth are usually identifiable because they look different from all other theropod teeth found there, and no other spinosaurids are known from the location.

4. A tyrannosaurid tooth from the Two Medicine Formation that is not thick in shape is likely to be an Albertosaurus tooth, since Gorgosaurus and Daspletosaurus, the other two tyrannosaurids from the same time, had thick, T. rex-like teeth, whereas albertosaur teeth are thinner.

On topic, as everyone else said, there is no known skull material from Deltadromeus. In fact, some studies find it to be close to the herbivorous ceratosaur Limusaurus, so it may have been a herbivore rather than a carnivore. Limusaurus had no teeth, so if the herbivore hypothesis is correct, then delta might not have had teeth at all.

Edited August 31, 2013 by Carcharodontosaurus

[Auspex]

There are folks for whom a 'high likelihood' is good enough identification for conversational purposes, and there are those who require compelling physical proof. Those of the latter group tend to take a dim view of the 'lax scientific standards' of the former group, because such 'common knowledge', repeated often enough, can become popular 'fact' (and those of the latter group tend to be folks who devote their lives to dispelling misconceptions).

<sigh> This has always been, and will ever be, a point of conflict between vocational and avocational science.

[Ridgehiker]

Fossil collecting is not like stamp collecting. There is no finite listing of Dino's, trilobites, ammonites, etc. No catalogue to reference. There are only published papers describing particular fauna. It's akin to thinking that Coke and Pepsi are the only two brands of soft drinks then assuming that a fragment of broken glass must be one or the other....not knowing that other brands exist.

Unstudied fossils are not rare. They are the majority. Research and museum drawers are jammed with them. I doubt if 1 in 10 specimens we collected for the GSC was ever seriouslylooked at after being curated and put away in the dungeons.

[Regg Cato]

Fossil collecting is not like stamp collecting. There is no finite listing of Dino's, trilobites, ammonites, etc. No catalogue to reference. There are only published papers describing particular fauna. It's akin to thinking that Coke and Pepsi are the only two brands of soft drinks then assuming that a fragment of broken glass must be one or the other....not knowing that other brands exist.

Unstudied fossils are not rare. They are the majority. Research and museum drawers are jammed with them. I doubt if 1 in 10 specimens we collected for the GSC was ever seriouslylooked at after being curated and put away in the dungeons.

Excellent point; we only know of a (relatively) few number of theropod species from the middle Cretaceous of Saharan Africa. It's pure speculation to assume that teeth of a certain morphotype from a particular stratigraphic context are Deltadromeus, because that's what its teeth "should" look like. As Carcharodontosaurus pointed out above, if Deltadromeus was edentulous like Limusaurus, then that renders this whole discussion moot lol.

There are undoubtedly entire species of dinosaurs who managed to avoid fossilization entirely, as well as species that we might only ever know about from fragmentary scraps of bone that cannot be identified (after all, every scrap of bone once belonged to a living animal that was some species or other). But at this point, there are no teeth that have definitively been identified as belonging to Deltadromeus (i.e. in a dentary/maxilla/premaxilla or closely associated with a skeleton that is unquestionably Deltadromeus), and until there are, no isolated teeth can be validly assigned to this genus.

[AJ Plai]

Many great points and very productive discussion with many useful info. Thx all for the input!

It seems it would be more suitable to view it more as a Moroccan/African ceratosaur. Though any teeth experts here can help clarify as to what are the key features of a ceratosaurian tooth that distinguish it from a carcharodontosaurid tooth?

Edited September 1, 2013 by AJ Plai