An in depth look at the Spinosauridae

did this with the abelisaurs; I plan on doing this with every predator family.

The Spinosaurs were a specialized group of theropods in the superfamily, the Megalosauroidae. They evolved from these creatures in the mid jurassic, and haunted the waters edge until their inevitable extinction. But, what were they? how did they behave? what was the largest? All questions i plan to answer with this topic.

The first spinosaurs burst onto the scene in the mid jurassic. Although known from a single tooth, Ostafrikasaurus crassiserratus was undoubtely a Spinosaur. Ostafrikasaurus is based on a thick and serrated tooth which is about 2.0 inches in length. Buffetaut (2008) suggested that this tooth represents a new genus of Spinosaur, and that it differs from other teeth previously referred to Ceratosaurus stechowi. Though only known from one tooth, Estimates put this animal at around 25 feet and 1-2 tons; the single tooth makes estimations rather difficult.

Into the Late Jurassic/ Early Cretaceous. The Spinosaurs started taking on a more recognizable form, with the likes of Baryonyx Walkeri, Suchomimus Tenerensis, and Cristatusaurus Lapparenti. Each was of gigantic stature, measuring 3o+ feet and weighing in at around 2-4 tons.

Baryonyx Is one of the most iconic spinosaurs, sporting the 9 inch thum claw.

The use was clear; to spear fish from the lazy rivers of its domain. However, fossil evidence in the stomach of a Baryonyx indicates that these animals didn't just rely on fish. The remains of an iguanodon were found associated with this species. Whether it was scavenged or a kill on the part of the Spinosaur, is indeterminate.

The Species Irritator has been associated with pterosaur remains, which it undoubtedly had killled; and had been killed in the process of swallowing its helpless victim.

The larger species - such as suchomimus and cristatusaurus - could tackle small to medium sized dinosaurs, but there has not been any fossil documentation of this.

Now, onto the giants..

We all know him from the JP3 film, the biggest, baddest, most famous spinosaur to walk this earth:

Spinosaurus Eagyptiacus

This early Cretaceous titan measured 16 meters and tipped the scales at 8-10 tons.

It lived in a Carcharodontosaurid ruled Africa, batteling for food resources.

Such an impressively large creature should have recieved word wide notoriety, right?

Well, it has. For all the wrong reasons.

The Documentary Monsters Resurrected did just that; resurrect a monster. One capable of lifting 30, 2 ton abelisaur clean into the air, shredding the face of a Sarchosuchus, and taking out a large Carcharodontosaurus with a single swipe of the claw.

All things that would be out of its range, Territorial wise and strength wise.

Let's examine the real animal, shall we?

For starters, These are the remains that we have:

 No arm or leg bones, no ribs. See the issue?

But, Paleontologists have crafted a picture of this animal, based on  Suchomimus and Baryonyx. To them, Spinosaurus is a giant 18 meter, multi ton  animal.

I myself have issues with this.

First, scaling off an 11 meter Suchomimus gives you a staggering weight of 16.7 tons. That kind of weight - even distributed over an impressive length - is too much for a bipedal creature. The strain would be enormous.

However, Proponents for the 17+ meter animal, and the shortened animal, still hold fast to their believes.

In 2005, Del Sasso made ​​his debut in the world by declaring an estimate of 18m for our Theropod African favorite: Spinosaurus aegyptiacus. From there began a long debate on the size. While there are people that "inflate" the spiny lizard to 19-20 meters, there are others that the shorter, as Andrea Cau, at 13-14 meters. Each of the two schools of thought has evidence to support it: the skull.

Thinking of those who stretch the Spinosaurus:
"The rostrum found by Del Sasso had to belong to a skull 1.95 meters long, and then, as the Spinosauridae had a skull shortened relative to the body, could eaasily get 19-20 meters.

However, Del Sasso has been criticized as his estimate  is the ONLY ESTIMATE for a Spinosaurus exceeding 16 meters. And, as Dave Hone has pointed out on his brilliant blog Archosaur Musings, length is very much about tail length which can vary enormously without affecting the actual size or mass of the animal at all.

Therefore, weight estimates should be used to give us a better understanding of the total mass of the animal, while size can fluctuate enormously based on reconstructions of the tail. "Seismosaurus", or more properly Diplodocus hallorum, is a great example of this: it was reported to be 40 meters long originally because a tail vertebra was mistakenly thought to be very far behind the animal's back when it was actually quite close to the hind legs. 

Andrea Cau - Who has put Spino around 14 meters and around 7.5 tons - has his critics as well. Some scientists point out his use of the Tetanurae in his weight studies, instead of using related Spinosaurs.

18 metres is extreme hypotetical reconstruction, based on an already "tentative reconstruction" of the skull. Other, more accurate reconstruction never reach such lenghts, stopping at 14.4 meters. Cau shot back at his critics, stating   "I'm not interested at all on the actual body size of Spinosaurus, since that value is currently unknown (no moderately complete skeletons are available), so, any extrapolation is pure speculation and as robust as its skin color". He just wanted to point out that you just never get a 18 (but even 17, 16, 15...) metres animal scaling from Baryonyx. Since we have to compare the bones preserved for both taxon, he tries to compare the vertebrae. Comparing rim-to-rim lenght for the vertebrae - 154 mm in Spinosaurus vs 110 mm for Baryonyx - he gets an animal 1,4 times bigger than Baryonyx. So, 12,6 metres long if the 9 metres estimate for Baryonyx is correct. If Baryonyx was actually 10, 5 metres long, well, we still have a Spinosaurus shorter than 15 metres (a 14,7 metres one, very similar to Hartman's). You are free to think that 18 metres estimate shouldn't be called a "myth", but is clear that a misure which can be twice the linear lenght of Baryonyx is completely baseless.

There's s train of thought saying the holotype Spinosaurus is a Sub adult. Proponents of this point to this as 'evidence' as Spinosaurus getting past 17 meters in length. To me, this is point less speculation.

There is another giant, lurking in the depths of south american soil for millions of years:

 Oxalaia quilombensis

A giant rivaling even perhaps Spinosaurus in size. Unfortunately, it has yet to undergo Scientific scrutiny. It is an exciting animal indeed, and who knows? perhaps there are even bigger Spinosaurs waiting to be uncovered.

So, there you have it. Kind of a two in one post, hope you enjoyed!