The size of Siats Meekororum

This Carcharodontosaur is only the second ever unearthed in north america, right next to Acrocanthosaurusl, which ived about 10 million years before Siats, and Siats is in a different branch of the carcharodontosaur family, the Neovenatoridae. This is the first time a member of the Neovenatoridae has been found in North America.

But, how big was it exactly?

Here's a quote from the initial paper describing it:

"Holotype. FMNH (Field Museum of Natural History) PR 2716, partial postcranial skeleton of immature individual including portions of the axial column, pelvic girdle and hind limb(Fig.1).Immaturity of the holotype is evident from lack of neurocentral fusion across the axial series except in distal caudals. Select measurements are provided in Table 1.
Referred specimen. FMNH PR 3059, a mid-caudal neural arch and chevron, a pedal phalanx and several indeterminate bone fragments."

"Methods 
Size class estimation. We interpolated an estimate for the femoral length (FL) of Siats, a widely used proxy for body size in dinosaurs54–56, from regressions against diaphyseal measurements of the ï¬bula28. The ï¬bula exhibits a phylogenetic trend towards diaphyseal reduction across theropod evolution, which we accounted for by employing Phylogenetic Independent Contrasts57 to ï¬nd the regressions and their conï¬dence intervals. Phylogenetically corrected predictions of FL ranged from 1,166 to 1,410mm depending on which ï¬bular metric was employed. We conservatively employ the lower estimate and note that these data are extrapolated from an immature individual, further reducing potential inflation of our estimated FL for this taxon. An estimated FL of 1,166mm approximates the 1,190mm reported for the closely related Chilantaisaurus from China, and thus Siats is one of the largest megaraptorans recorded. Our size estimates also compare well with the 1,266mm observed in the stratigraphically older carcharodontosaurid Acrocanthosaurus from the Albian Cloverly and Trinity formations, and also the latest Jurassic allosauroid Saurophaganax, which has an 1,135mm long femur. Moreover, Siats was by far larger than the four or more other theropod taxa documented in the Mussentuchit32, and well above the one ton estimate employed by previous authors to deï¬ne apex predators15."

In short, they believed this thing was a juvenile mainly because subneural arches weren't completely fused. These are the only bones In this specimen to show this condition. I didn't read anything on a skull, but if they found unfused sutures...that would be a definitive sign of this Siats being a juvenile.

 being in the rough condition it was in(less then 40 percent) we cannot tell too much about this thing, but we can extrapolate its size using Femur Length(FL) as the paper did.

Just by the length of the femur, we can tell it's one of the largest north america has ever had stomp across it.

The paper does estimate its mass at 3.9 tonnes, there's no mention of total length, but assuming perfect isometry with Acrocanthosaurus it'll be ~10.8m long (~35ft), I'll check with Hartman's Neovenator, that should be a better comparison, but of course, not perfect since Siats is not that complete. 

 Comparing with Neovenator using the estimated femur length yields roughly 11.7m in length from tip to tip,

The 13th dorsal is 54% longer than that of the holotype of Neovenator, the 5th is 89% longer, removing the bones from the skeletal in the paper (is not that good) and trying to fit them in Neovenator, I got it at something like 55% bigger, it turned up again over 11m from the tip of its tail to the jaws.

The subneural arches are not fused, but that's about it. Seeing this, and after digging around some what, i've come to the conclusion that this animal wasn't a juvenile, but was instead a Subadult, just about to reach maturity. 

The individual they unearthed was around 11.5 meters long, and weighed in at around 4 tons. By my estimations( i'm not too familiar with Neovenatorid growth rates, so don't quote me on this) An adult Siats Meekerorum would measure 12.2 meters and weigh in at around 5.5-6 tons.