Mosasaur Jaws Explained – Composite vs. Natural

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Natural (left) vs Composite (right)
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Natural (left) vs Composite (right)

Mosasaur Jaws Explained - Composite vs. Natural: Introduction

As someone with 20 years experience, A collector of fossils, crystals and meteorites. A fossil dealer and someone who has helped identify Dinosaur and other reptile material for private museums, collectors and my local county museum, I see a lot of people misguided on ebay and will be writing guides to help better educate everybody before expensive purchases.
Please don’t take my guide as a negative criticism of rival sellers, there are many reputable and respected dealers on ebay, a few of whom I would highly recommend to customers who are looking for something I can’t source. However there are many who deceive  buyers, maybe not even knowingly, but by their own inexperience and lack of knowledge of what they’re selling. I have personally received material over the years that a wholesaler or direct contact on the dig site has misidentified or simply overlooked recent classifications, an inexperienced seller won’t know any different.
Anyway, now onto the fossils. This guide will be touching on the ever popular Mosasaur jaws (sure to become even more popular with their inclusion in Jurassic World!). Hopefully my guide helps parents and collectors alike.

Composite example with a loose tooth for comparison
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Composite example with a loose tooth for comparison

Composite Jaws

What are they? Composite jaws are by far the most popular of all Mosasaur jaws on ebay, they’re EVERYWHERE. They’re reasonable inexpensive also, usually priced £20-£30 depending on the size and how many teeth are present. However MANY sellers advertise them as natural… This is incorrect. Many of these sellers just don’t know any different, others don’t tell you and leave it to your level of expertise and some downright lie to you.
A composite jaw is a compressed pile of a sandy matrix, usually bonded with some form of glue and are usually in an oval shape. This is NOT the natural, as-found matrix the teeth were found in. It is for display purposes, not purposely done for deception. They are not “fake”, it is simply a way to present a pretty package.
The jaw bone is 99% of the time NOT Mosasaur jaw bone. Infact it’s not the bone the teeth were attached to AT ALL. It’s a composite of various crushed fossil fragments that have no value, perhaps a tiny bit of Mosasaur bone among it, that is then shaped into a jaw, again for display purposes.
The teeth ARE real, these are sized accordingly and added in semi realistic positions to complete the look of the piece. If you look closely, you can see the filler between the tooth and composite jaw bone.
How can I tell though? – It’s incredibly easy, I have included pictures from my own stock of natural and a composite jaws. The tell-tale signs are:
1. The jaw doesn’t look like a jaw. Mosasaurs are very Dinosaur/Crocodile like, their jaws are not two thin rectangular sticks. They’re rounded over the top and bottom, and would extend to both sides of the piece. Look at the Natural vs. Composite picture I attached.
2. The price tag. If it’s under £50 it is NOT natural, simple as that. Natural jaws cost £100+ and that’s just a fragment.
3. They’re oval, sandy slabs. Seriously, they all look the same.

I own one, can I test it? It’s very very easy to test, pick it up and scratch a part of the sandy matrix. Does it come away very easily, very lose and sandy? It’s composite. Still not convinced? Soaking in water will cause the composite matrix to completely fall apart, leaving you with loose teeth. But in all honestly, you should be able to tell by just looking at it.

Natural section (mean both sides, like slicing a section out of a log, natural jaws are like that but with the snout)
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Natural section (mean both sides, like slicing a section out of a log, natural jaws are like that but with the snout)

Natural Jaws

What are they?They are as they say, a fragment of a natural part of Mosasaur jaw, usually with some original teeth, in the matrix it was original dug from. The piece is as it was found and nothing has been added to it.

Occasionally you do find some slightly enhanced pieces. I have seen a beautiful natural Globidens jaw. The matrix and jaw bone were original but the only original tooth was damaged, so a few additional loose ones were added. Again an inexperienced seller may see “natural jaw” advertised at their wholesaler and not realise this. Most reputable sellers who are able to stock these high end fossils will however hopefully advertise this, as I personally would.
How can I tell though?Again these are generally very easy to spot.
1. Their price tag is HIGHLY unlikely to be under £100, unless its a tiny fragment (sub 3 inches of only one part and one side of the jaw)
2. Natural jaws are not two thin sticks with a few random teeth. Picture a log, now if you take a saw and take the ends of, what is left? A smaller log right? It remains complete all the way around the log. The same applies to natural jaws, they're just missing the main skull part (brain casing, eye sockets etc) but you'd be getting top, bottom, right and left sides of the jaw. Sure sometimes its just the left side of the bottom jaw, but generally you'll get a complete "log" section.
3. Look at it. It’s 6-7 inches of section right? It’s also not an entire skull, so this Mosasaur was clearly fairly large. Surely it would require a sturdy jaw? The amount of bone is going to dwarf the size of the teeth for this reason. Think you could eat a steak with 2 inch teeth and a jaw that’s stick thin?
4. The matrix will be tightly packed and not anywhere near as sandy. Its been compressed naturally over millions and millions of years.
5. Finally if you’re really unsure, but are willing to part with serious money, you should stick to reputable sellers who run actual businesses.


So are composites a waste of money?NO! Not at all, in fact as long as you’re buying from someone who is honest that it is a composite and you’re not paying a fortune, then go right ahead. They make for very attractive display pieces and the teeth are genuine Mosasaur fossils. They’re also fantastic for children. Believe me you do NOT want to pay £300 for a genuine, natural double jaw fragment and then one of them drops it.
Remember these are NOT “fakes” designed for deception. They’re just often sold by many dishonest non-business sellers due to their relatively cheap cost and high display appeal. They are also sold for what they are, displayable composite pieces, by many top businesses like myself.
Hopefully my guide has helped you in your purchase decision, educated you on the subject and made collecting a little bit easier.
Any questions? Need help regarding a purchase of a Mosasaur Jaw, or just need purchase advice? Just drop me a message via ebay and I’ll do my best to help you. Please keep an eye out for future guides and give my ebay store Dino Deals UK a look, maybe even favourite it to stay up to date on my products.
Written by
D. Bartlett of Dino Deals UK

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