Maximum Lifting Capacities of Carcharodontosaurus

[Chaos Soahc]

Hello, 

I want to get some insight on Donald Henderson's prey lifting potential of carcharodontosaurus paper. I did find the study to be very intriguing I have two major criticisms.

1) This paper doesn't account for the rest of the body such as the caudal and leg musculature helping to lift much bigger loads. Many animals have other muscular groups helping to achieve certain tasks.

2) I think it underestimates the musculature in the neck, while this is outside my level of knowledge, I found that other fellow paleontologists have similar ideas, and with studies such as the Snively & Russel 2007 paper, it leads me to have this particular criticism,

While I really think the 

Are my criticism's somewhat valid, and does anyone have and reasonable estimates on how much large theropods, like say a T. Rex or a Carcharodontosaurus in this case can lift?

Snively, Eric & Russell, Anthony. (2007). Craniocervical feeding dynamics of Tyrannosaurus rex. Paleobiology. 33. 610-638. 10.1666/06059.1. 

Henderson, Donald M., and Robert Nicholls. "Balance and Strength—Estimating the Maximum Prey‐Lifting Potential of the Large Predatory Dinosaur Carcharodontosaurus saharicus." The Anatomical Record 298.8 (2015): 1367-1375.

[Eric Snively]

Henderson and Nicholls's results are pretty good within the simplified assumptions they used: scaling Allosaurus muscles to the cross-section expected in Carcharodontosaurus basd on the specimens' difference in linear size. They calculated static moment (force x lever arm lenghs) for head dorsiflexion, so the paper did not assess total lifting capability with postcervical muscles. As the the original post intuits we can add 35-40% to the muscle forces in the paper*** (see below), but the inital results will hold up well for the lifting function Nicholls's painting depicts.

As for the specific critiques:

1. Engaging other muscles for lifting prey: Theropods do (and could!) use other axial and limb muscles to augment the neck muscles, although head dorsiflexion and mainaining closed jaws would still be limiting factors. Some raptorial birds (kestrels, bald eagles, perigrine falcons) keep their heads dipped downwards rather than dorsiflexed as they pull to lift prey or tear flesh, while rearing up with their hind limbs. As they pull back their necks lengthen (probably with eccentric contraction of neck muscles)  but stay short enough to tear flesh.  Carcharodontosaurus could certainly rear up by engaging caudofemoral and hamstring muscles on both sides for hip extension. As long as they maintained balance.

2. Muscle anatomy and function. Again the authors made reasonable force and moment calculations, and errors probably balance out. Carcharodontosaurs had relatively smaller neck muscle insertions than Allosaurus, but probably a bigger moment arm for m. complexus than shown in the paper.  My fault rather than the authors', since most of the muscle inserted higher on the parietals than lower on the squamosals as my papers indicate. Takanobu Tsuihiji's work and mine show we have to look carefully at individial taxa for that muscle's likely insertions. 

To bring critiques 1 and 2 together, carcharodontosaurs had really efficient and effective neck ligaments and osteological bracing, so were probably good at hanging onto things without tyrannosaur-style big neck muscles. Taurovenator, Meraxes, Acrocanthosaurus had tall cervical neural spines and extra articulations, and Carcharodontosaurus might have had the same morphology. 

***A super-boring illustration that the results are reasonable (TL;DR the authors used an ok value for muscle specific tension): We can reconstruct ranges of plausible anatomical cross-sectional area for muscle force generation in extinct animals, but we really need physiological cross-sectional area (PCSA) which includes fiber length and pennation angle.  To calculate force we multiply PCSA by a force/area muscle produces, called a specific tension (which in turn relies muscle fiber physiology). Allosaurus neck muscles have lots of origins leading to single insertions. I proposed a specific tension for an anatomical cross-section normalized to PSCA: 55 N/cm^2 based on the average potential lengh of muscle fibers from origins to insertion, and actual isometirc specific tensions of 30-32 N/cm^2..Turns out that 55 N/cm^2 of anatomical cross-section is similar to that of human quadriceps muscle.