Were Spinosaurus Teeth Really That Common?

[Stocksdale]

The information on the new Spinosaurus finds and the new display have been released today. Kind of a cross between a dragon and dimetrodon

Here's New York Times article

http://www.nytimes.com/2014/09/12/science/a-nomads-find-helps-solve-the-mystery-of-the-spinosaurus.html?_r=1

Here's the paper

http://www.sciencemag.org/content/early/2014/09/10/science.1258750

Exhibition page

http://events.nationalgeographic.com/events/exhibits/2014/09/12/spinosaurus-lost-giant-cretaceous/

Edited September 11, 2014 by Stocksdale

[Fallingfossils]

I am very much looking forward to that new exhibit (and seeing the museum since I haven't been there before).

I saw about it here:

http://www.sciencedaily.com/releases/2014/09/140911142714.htm

[Troodon]

My vote is that it looks like a DRAGON

[Auspex]

To me, this interpretation of the enigmatic creature makes more sense than prior reconstructions; there just aren't many analogs for a bi-pedal aquatic predator.

[Troodon]

I kind of liked Stromers reconstruction but will go with todays interpretation it does look cool. This reconstruction was based on using fragments from a new sub-adult skeleton, Stromers bones, isolated bones from the Kem Kem, surrogate bones from other spinosasurids like Baryonyx and Irritator, and inferred bones from adjacent bones. Hopefully one day an articulated specimen will be found to put this to bed.

[Stocksdale]

Here's an image of the new reconstruction. The red ones are the combination of the original material found by Stromer with the new material. So it appears that they now have hind leg material where they didn't previously.

[Troodon]

The more I think about this new reconstruction the more I'm scratching my head and of course swimming upstream against some pretty bright paleontologists and popular opinion. This will be the first quadrupedal theropod dinosaur on the record, which is unique. The interpretation appears to make sense in an acquatic environment but it falls apart when on land. Its hands have long thin claws which are not suitable for walking. It would have to be a knuckle walker to get around making it very vulnerable to larger prey.

The reconstruction also does not compare well to other more complete spinosaurids found like Baryonyx and they must have lived in similar environments, why is it different? The reconstruction was based on better information but was it complete enough to draw these conclusions? Here is the detail on what it was based on:

Red : Sub-adult bones size adjusted (was it done correctly?)

Orange: Stromer's bones

Yellow: Isolated bones found in the Ken Kem

Green: Surrogate bones modeled from other spinosaurids like Baryonyx

Blue: Inferred bones modeled from adjacent bones ( Lots of blue in the hip area)

We need to find a complete animal to put this to rest and I welome new ideas to move this discussion forward. I will be very interested to hear what peers have to say.

Edited September 13, 2014 by Troodon

[Stocksdale]

Good points, Troodon. I think we are a long ways away from the final word on Spinosaurus.

With this new reconstruction, I wonder if the scientists might be thinking that they would knuckle-walk on land but I'm not clear from the scientific paper. Here's one excerpt from the paper.

The locomotor adaptations outlined above, however, mark a pro- found departure in form and function from early spinosaurids. Prominent among these are the reduced pelvic girdle, short hind limb, short femur, and long, low, flat-bottomed pedal unguals, all of which can be verified in the second partial skeleton described by Stromer as “Spinosaurus B” (2, 8). We note here that Spinosaurus must have been an obligate quadruped on land, the first among theropod dinosaurs, given the usual horizontal sacroiliac joint and the anterior location of the estimated center of body mass (8). Baryonyx was interpreted as a facultative quadruped based on its long skull and neck and robust humerus (27), but this was not confirmed by discovery of more complete hind limb remains of the related Suchomimus (13).

It would some sense. Other animals like apes have adopted knuckle-walking. I assume the ancestors of apes were bipedal in a similar way to the ancestors of Spinosaurus being bipedal but evolving toward quadrupedalism.

Edited September 13, 2014 by Stocksdale

[Axelorox]

The new finds do indeed demonstrate an interesting morphology for this species. However, the color-coded skeletal illustration that's getting passed around in every article on this may be problematic - as Scott Hartman points out there seems to have been a scaling error made, possibly resulting in overly small hind limbs. Scott has a nice adjusted picture (using only the measurements published in the new paper) that shows slightly longer legs.

[Troodon]

I've always been impressed with with the huge fine claws on the Spino hands and large carpals but never imagined that they could be used for walking. I read Hartmans blog and his points are valid. I do not know how much peer review the paper has received but I'm sure everyone will chime in. A more complete specimen needs to be found its that simple.

Edited September 13, 2014 by Troodon

[Harry Pristis]

Today's Sciencexpress paper suggests that the dinosaur was even more aquatic.]

The core of the new study, led by University of Chicago paleontologist Nizar Ibrahim, is a partial skeleton of Spinosaurus found in the 97 million year old rock of Morocco. The importance of the new specimen is in revealing parts of Spinosaurus never seen before. The skeleton includes parts of the skull and some vertebrae, but the real keys to the new Spinosaurus are the hips and hindlimbs.

The turn-of-the-century Spinosaurus popularized in Jurassic Park III and numerous pieces of paleoart stood tall over Cretaceous floodplains. But the hips and legs described by Ibrahim and coauthors look quite small and relatively weak. The femur - or upper leg bone - is short, yet has a robust flange of bone for a major leg-tail muscle retractor. And the foot bones of Spinosaurus are flat, with broad toe claws. This was not a dinosaur suited to running down prey. Spinosaurus, as envisioned in the new research, would have propelled itself through the water with strokes of its feet and sinuous flicks of its tail. ---Brian Switek, Phenomena

[Troodon]

Harry you are correct and those are the red color coded bones in the skeleton from my post #32. They were from a sub-adult specimen and resized to fit the reconstruction. There are questions by some like Scott Hartman on how accurate that was done and he gives examples especially with the hip. I have no problem with hindlimbs that makes sense but my problem is the forelimbs. Just have a difficult time envisioning any walking or now knuckling as a theropod unless it was completely aquatic.

[AJ Plai]

The possible fact that Spinosaurus lived an aquatic life for most of its life could perhaps explain why we find an abundance of their teeth which should be quite uncommon for an apex predator of that size? The aquatic environment has for the most part been a better environment for preservation of carcasses and fossilization process. It would also help to explain why their teeth are so often found with an abundance of croc teeth also. Plus, if Spinosaurus had found a unique environment niche where they don't have to compete directly against other large apex predators like the Carcharodontosaurus, then it could explain why their teeth were so common as well.

It has always been hard to imagine the prehistoric Kem Kem as paradise of gigantic predators living side-by-side while the fossils record there haven't really found their "prey" fossils in a large number enough to really support the sustainability of such ecosystem, but if Spinosaurus and Carcharodontosaurus lived in different environments. It starts to make more sense, I think. The new discovery will be very intriguing to follow what they will uncover next. An exciting time for dinosaur fans and Kem Kem collectors and fossil hunters for sure.

[Stocksdale]

I would think the aquatic environment would preserve more than just teeth. But they don't find bones just lots of teeth.

[Auspex]

I would think the aquatic environment would preserve more than just teeth. But they don't find bones just lots of teeth.

Coming out of phosphate mines, this does not surprise me too much.

It seems like most of the bone shards are being carved into "mosasaur" jaws; some of these may be (although unidentifiable) bits of Spinosaurs.

[Stocksdale]

Coming out of phosphate mines, this does not surprise me too much.

It seems like most of the bone shards are being carved into "mosasaur" jaws; some of these may be (although unidentifiable) bits of Spinosaurs.

Ahh. So it's a lot of smaller material of bones and teeth jumbled. And only the teeth are somewhat identifiable.

Amazing to think a fake composite 'mosasaur' might contain a real spinosaurus bone.

Edited September 15, 2014 by Stocksdale

[Harry Pristis]

Auspex posted Today, 10:57 AM

Auspex, on 15 Sept 2014 - 08:23 AM, said:

Coming out of phosphate mines, this does not surprise me too much.

It seems like most of the bone shards are being carved into "mosasaur" jaws; some of these may be (although unidentifiable) bits of Spinosaurs.

Ahh. So it's a lot of smaller material of bones and teeth jumbled. And only the teeth are somewhat identifiable.

Amazing to think a fake composite 'mosasaur' might contain a real spinosaurus bone.

Spinosaurs stalked the shores of Cretaceous lakes and rivers. Paleontologists have known this for decades. The remains of fish and juvenile dinosaur bones found in the gut of Baryonyx - the dinosaur responsible for highlighting spinosaurs as oddballs - showed that these dinosaurs probably used their conical teeth and huge claws to nab prey in and around waterways. And geochemical evidence from spinosaur teeth further supported the notion that these carnivores stuck close to freshwater habitats. ---Brian Switek, PHENOMENA

Phosphate mines are the bottom of a saltwater bay, aren't they?

[Stocksdale]

I'm pretty much a novice at this so I might be very confused.

But it appears the phosphate mines of Khouribga (where many mosasaurs are found) and the Kem Kem beds (where spinosaurus are found) are two different parts of Morocco.

I think the age of two formation might be different as well. However, I imagine they could still make bad composites with material from both locations.

Edited September 15, 2014 by Stocksdale

[Auspex]

I had thought that the avalanche of Spinosaurus teeth was coming from phosphate deposits; am I wrong in this?

[Stocksdale]

Like I said, I really don't know. So I'd be glad to hear an expert opinion on the two deposits.

From a rough search on ebay, it appears like very different teeth are coming from the two areas. Enchodus and Mosasour from the Khouribga. Spinosaurus from Kem Kem.

I wonder if there are phosphate mines at both locations?

Edited September 15, 2014 by Stocksdale

[Troodon]

Here are the Kem Kem exposures in Morocco best rendition I've seen. The Grey color.

Khouribga is further north west

[Troodon]

Most if not all the Kem Kem is desert and material is found in caves dug on the side the hills. The new Spino sub-adult bones came from an excavation cave. Very dangerious work and why very little material comes out. I have pictures but my computer is not at the ready.

Let me add that where they found the bones it was a layer of sandstone and mudstone.

Edited September 15, 2014 by Troodon

[Auspex]

It is clear that I was wrong in my assumption that these Kem-Kem beds were being mined for phosphate.

Is the geology well enough known to suggest the depositional environment there?

[Troodon]

Boy I'm the furthest from understranding the stratigraphy of the area. The paper on the new Spino bones indicates that most of the vertebrate remains come mainly from the sandstone layer of comglomerates and debris flow deposits. So it appears to be depositional. They suspected that some portion of the skeleton was originally present by what they found at the mouth of the cave, pretty cool.

[Troodon]

The attached thumbnails show the Kem Kem area where the new bones of the sub-adult Spino were found. The red arrow pinpoints the exact area. The cave is where the bones were excavated, see the rock hammer. I've see other pictures of the caves in the Kem Kem and this is typical of those images. Not a very hospitable place to collect.