The Morrison Titan - Part 1

Argentinosaurus is commonly considered to be the largest dinosaur.

If not it, some giant Cretaceous gigapod such as Puertasaurus is given the crown. Nowadays, it seems that whether the question of what is the largest known dinosaur is brought up, most people would answer with something within Titanosauria and from the Cretaceous period. In 2014, the bones of an unnamed gigantic titanosaur, with a femur requiring three forklift pallets to hold, has been unearthed and a skeletal mount of it, restored with speculative portions, has been placed on display.

 But do the Cretaceous titanosaurs really hold the crown?

Likely not so.

A few brachiosaurs such as Breviparopus and Ultrasauripus possibly rival or exceed the sizes of supergiant titanosaurs like Argentinosaurus or Puertasaurus.

Even the good old Brachiosaurus altithorax could probably reach Argentinosaurus-esque sizes, as a large specimen (~2.42-meter humerus) in the BYU collections (Paul, 1988) suggests. This B. altithorax specimen probably massed over 70 tonnes, vindicating Walking With Dinosaurs' Brachiosaurus mass figure.

The giant Oklahoma Apatosaurus ajax specimens, which probably massed between ~50-60 tonnes or so, aren't even fully grown, they lack cervical rib fusion, which corresponds to roughly ~80% of fully-grown adult dimensions in Diplodocus and Giraffatitan. It's probable that Apatosaurus ajax adults reached the 100-tonne mark, surpassing Argentinosaurus and possibly rivaling Puertasaurus in size.

But how about something larger than even them? It turns out that such creatures probably existed. Three are known, but one is known only from a footprint (~1.5-meter wide footprint in Plagne, France). That'll be a story for another time. Another is known from an incomplete sacrum ("Brachiosaurus" nougaredi from North Africa), which will also be a story for another time.

One day, in 1878, during the Bone Wars, Edward Drinker Cope discovered the bones of a sauropod dinosaur in the Morrison Formation. He named the animal Amphicoelias, meaning "double hollow", "amphi" meaning "both sides" and "coelias" from "koilos", meaning "hollow". The binomial name was Amphicoelias altus, meaning "high double hollow", "altus" meaning "high" or "elevated".

It was far from complete. Here's what Cope found of it, along with additional elements assigned later on such as a shoulder girdle and an ulna:

More recently, analysis of the scapula material revealed a camarasaurian nature, while the ulna, being referred to A. altus largely based on disagreement with Camarasaurus and the other sauropods in Cope's collection, is probably a candidate for exclusion.

From Tschopp and Mateus, 2015:

"The holotype of Amphicoelias altus originally included a tooth, two dorsal vertebrae, a pubis, and a femur (Cope, 1877a). A scapula, coracoid, and an ulna were later provisionally referred to the specimen (Osborn & Mook, 1921). However, the strongly expanded distal end of the scapula, and the relatively deep notch anterior to the glenoid on the coracoid actually resemble more Camarasaurus than any diplodocid (McIntosh, 1990b; E Tschopp, pers. obs., 2011). The same accounts for the single tooth stored at AMNH (Osborn & Mook, 1921). The tooth has already been excluded from scores of A. altus in recent phylogenetic analyses (Whitlock, 2011a; Mannion et al., 2012), which is followed here. Mannion et al. (2012) furthermore excluded the referred forelimb elements. Given that personal observations confirmed the rather camarasaurid than diplodocid morphology of the scapula and coracoid, but not particularly the ulna, two different preliminary phylogenetic analyses were performed with a reduced (excluding the tooth, the scapula and the coracoid, but including the ulna) and the extended holotype Amphicoelias altus OTU (including all referred elements other than the tooth). Because both analyses yielded the same position for the specimens, the reduced holotype was preferred in the final analysis. The risk of adding dubious information from potentially wrongly referred material was thus circumvented. More detailed analysis is needed in order to refine these assignments."

 Removing the referred shoulder girdle and ulna, this is what's left from the holotype, the original specimen that Cope found of it:

Not that much. But it's enough to give us a bit of an idea about the animal's size and proportions.

Now, this doesn't seem like an animal anywhere near Argentinosaurus size, let alone larger. But here's the thing - it's not alone. It had a cousin that was much, much larger.

Later in 1878, Cope, back in the Morrison, found a huge bone. A fragmentary neural arch from a posterior dorsal, around 1.5 meters tall. A single bone fragment, from a bone that isn't really very big by itself compared to the rest of the body, as tall as a person. Whatever animal bore this bone must have been truly immense in life.

This gigantic bone was assigned by Cope to a new species, Amphicoelias fragillimus, meaning "fragile double hollow".

Had this fossil survived to the present, Giraffatitan would have never taken fame as the "largest known dinosaur" for decades, and Tyrannosaurus would have never been called "the king of the dinosaurs". Argentinosaurus would not have had the fame for it's size that it has now, and the Chubut monster titanosaur wouldn't have looked so impressive. But this was not to be.

The bone was in very bad condition and was crumbling. It's condition deteriorated to the point that it was soon discarded, possibly by Cope himself. The fragility that gave it it's name, was the cause of it's destruction.

The legendary giant of the Jurassic, was lost, and then forgotten by almost all but a few. Ok, this animal has gained a little popularity recently, but is still very obscure. The big reason for this recent gain in popularity is Carpenter's 2006 paper, which attempts to estimate size based on the smaller A. altus dorsal and Diplodocus.

He arrives at a total last dorsal height of ~2.7 meters, a total length of ~58 meters and a mass of ~122.4 tonnes, approximately ~30 or so tonnes more massive than the average blue whale, or probably 50-70 tonnes more than Argentinosaurus.

However, his reconstruction depicts the animal as an upscaled clone of Diplodocus. Amphicoelias' actual known proportions are significantly different from those of Diplodocus. I will compare their proportions bone-by-bone in the next post.

"The Morrison Titan" - coming soon

Will be back when I make the skeletal reconstructions.

For now, let's just say that it's huge. Possibly one of the largest dinosaurs that ever walked the Earth, and almost certainly beyond the leagues of that awesomebro giant called Argentinosaurus.

Coming soon

Samson's height pt2

In my previous post, I dealt with the myth of the mounted skeleton of the "Samson" Tyrannosaurus specimen being ~4.6 meters tall at the hips. The skeletal mount itself turned out to be only around ~3.7 meters tall at the top of the hips. But even then, it's ilium is reconstructed somewhat too deep, in contrast to what actual Tyrannosaurus ilia suggest.

While Samson does have a preserved fibula and fragments of it's tibia, their measurements weren't listed.

I tried my hand at reconstructing Samson's hindlimbs. Parts in light gray are preserved but not measured.

Unmeasured and missing limb portions were scaled using FMNH PR2081 as a guide. The ilium is based on that of AMNH 5027, and FMNH PR2081 was used as a guide to cross-scale it.

Here's the measurements:
Ilium length = ~144.33 centimeters
Femur length = ~129.5 centimeters
Tibia length =  ~112.9 centimeters
Fibula length =  ~102.3 centimeters
Total hip height = ~341.4 centimeters

It actually ends up at a normal Tyrannosaurus rex hip height. Not surprising, given that it's known bone measurements are really no larger than that of a normal large Tyrannosaurus rex specimen (and smaller than those of FMNH PR2081).

Here's how it compares to the mythical ~4.6-meter Samson:

Notice how the real Samson's bones obviously don't fit in a ~4.6-meter hip?

references/sources
Scott Hartman's Tyrannosaurus skeletals
Theropod Database
AMNH 5027 illustration

Samson's height

Tyrannosaurus is 4 meters tall, blah blah blah. That's what most random online sources tall you.

But that figure is total nonsense, a fantasy with no basis in reality. In reality, T. rex's hip height levels out at around ~3.5 meters, give or take, whether the T. rex be Stan to CM 9380 to Sue.

Tyrannosaurus rex skeletal reconstructions by Scott Hartman. I do not own anything from this.

But is Sue the tallest Tyrannosaurus? Some, well, sources (including Wikipedia) states that Samson is the tallest known T. rex at an alleged ~4.6 meters in hip height. This is a mounted skeleton of Samson, with a woman standing next to the skeleton for scale:

Samson's mounted skeleton, mostly speculative though

And here's Samson's known bones and measurements, from the Theropod Database:

"skull (1.4 m), mandibles (dentary 870 mm), twenty-two teeth, nine cervical vertebrae, two cervical ribs, seven dorsal vertebrae, ten dorsal ribs, seventeen caudal vertebrae, four chevrons, femora (1.295 m), tibial fragments, fibula, metatarsal II (610 mm), metatarsal III, metatarsal IV (635 mm), ten pedal phalanges"

Samson's mounted skeleton measured

 If Samson were to be ~4.6 meters tall at the hips, then the woman standing next to it would have to be around ~1.99 meters tall. Although not impossible, women, or for that matter, humans, of that height are rare, and they tend to have more elongated builds. Assuming that this woman is almost 2 meters tall isn't the most parsimonius option. Also, this would make Samson's femur around ~1.61 meters long, which is a whopping ~24.32% longer than the measurement from the Theropod Database.

Assuming an average height of ~1.65 meters for the woman, Samson would be around ~3.8 meters tall at the hips. It's much lower than the exaggerated ~4.6 meter figure, but it's still a bit too high, as this would make Samson's femur around ~1.33 meters long, longer than the actual femur measurement.

Taking the femur length of ~1.295 meters, this yields a total hip height of ~3.7 meters for Samson (while the woman would be around ~1.6 meters tall). This is quite tall for a Tyrannosaurus, but not so tall as to be implausible.

Taller than Sue? Maybe, if that ilium, which isn't actually known from Samson, was actually reconstructed accurately. Why is the front part of that ilium so much higher than the rear portion, with a steep transition closer to the rear portion? That's not the case with Tyrannosaurus ilia.

Tyrannosaurus rex specimen AMNH 5027. Notice the ilium shape.

Sue and Stan skeletal reconstructions by Scott Hartman. Notice their ilium shape.

We'll see more about Samson in the next post.