Re-analysis of Spinosaurus Aegyptiacus

Something i had to do for my Paleoecology class, as these new remains have caused quite a bit of a stir in the Paleontological community.

Spinosaurus Aegyptiacus (Spine Lizard from Egypt)

This nice little image i'm about to show you,you all have seen at some point. 

The infamous remains bombed by allied forces in WW2, these were some of the firs - aside from dubious remains found in morroco - that we had of Spinosaurus.

It consisted of a few back vertebrate, tall neural spines, and a lower jaw fragment. The jaw had one or two teeth still in the socket, and had sensory pits at the end of it. This is a feature we see in modern crocodilians, an adaptation to detecting fish in murky water.

The jaw bone resembled that of Baryonyx Walkeri in basic morphology, and that of Suchomimus(Baryonyx?) Tenerensis too, bared a resemblance. These two species - though they may be one in the same - shared features with S. Aegyptiacus, and were the basis for size estimates since the early 1900's.

Basing off of Suchomimus Tenerensis yielded a monster. The math payed out to ~ 60 feet in length, and body mass ratios coughed up a staggering 15+ tons for S. Aegyptiacus. The reason for basing off of these two spinosaurs is 

1.) they werethe only relatively complete Spinosaurs to even get a somewhat accurate size off of, and

2.) Basing off of relatives is a key component in guestimating an extinct animal's size. We use thi methology with Paleocene animals, reptiles, birds, etc. using extant mmals and reptiles.

Below is a skeletal with the hypothetical reconstruction of S. Aegyptiacus, based on B. Walkeri and S. Tenerensis, along with Irritator Challengeri( mainly skull components)

So, the use of B. Walkeri and S. Tenerensis was absolute in theory, but new fossil remains have showed us S. Aegyptiacus was a much different animal then previously thought.

New remains, which include a partial skeleton of a subadult(FSAC-KK11888), show us S. aegyptiacus was a predatory theropod more suited for an aquatic lifestyle.

Below is one of the first papers describing this subadult, along with other elements of the skeleton.

https://onedrive.live.com/view.aspx?resid=4A81EF54B8849A4!24165&ithint=file%2cpdf&app=WordPdf&authkey=!APQ3JTj2pUHFBp8

The back legs are built very densely,and are proportionally shorter then those of other land based theropods( e.g. Tyrannosaurus, Acrocanthosaurus) an adaptation we see in modern day penguins as a way of keeping buoyant in water while hunting. It has been proposed webbing was in between the toes, though this is hypothetical at best as webbing doesn't fossilize generally. 

The forelimbs are very long, and though not as built with dense bone as the legs, were significantly heavier then those of other Theropods. S. Aegyptiacus has some of the longest arms of the theropods, with the exceptions of Therizinosaurus cheloniformis and Deinocheirus mirificus. 

Weight displacement in S. Aegptiacus is located closer to the toso rather then over the legs as in other bipedal Dinosaurs, which suggests a locomotion that includes Quadrupedalism. It's a virtual certainty S. Aegyptiacus wasn't fully quadrupedal, as the arm bones are too thin to support the weight of the animal. A facultative knuckle-walker would make sense;Obligate quadrupedalism seems very extreme. Hartman’s post on his website(found below) makes me think that a more posterior center of mass is conceivable. 

This is a feature not seen as appropriate for the other well known Spinosaurids, S. Tenerensis has rather normal sized hindlimbs and B. Walkeri seems to be similar. Giant  South American species (O. Quilombensis) are thought to reach the size of S. Aegyptiacus, and perhaps shared similar features, though they are far too incomplete to say.

New sketal designs have show us old reconstructions are incorrect; The hindlimbs and pelvic region were all scaled around 27% too small. Below is a reconstruction Scott Hartman has done rather recently, and the paper explaining in further detail why previous recontructions are incorrect is to be located beneath said image.

http://www.skeletaldrawing.com/home/theres-something-fishy-about-spinosaurus9112014

In conclusion, S. Aegyptiacus, along with the other Spinosaurs, were adapted to the rivers and estuaries of their time, where they occupied a niche that no animals - outside pterosaurs and crocodilians - had taken advantage of. This 'hole' allowed this particular tree of theropods to grow to massive sizes, and as a sresult, become more and more adaptive feeders as the millenia wore on.

Size estimations for the new remains paint a very different picture then what was though in the early 2000's. A more moderate size of ~52 feet TBL, and 6-7 tons in mass are more appropriate for S. aegyptiacus. Other giant Species, such as O. quilombensis, may have a similar size re-analysis, but fossil remains are too scant to tell at this time.