There is a world somewhere between reality and fiction. Although ignored by many, it is very real and so are those living in it. This forum is about the natural world. Here, wild animals will be heard and respected. The forum offers a glimpse into an unknown world as well as a room with a view on the present and the future. Anyone able to speak on behalf of those living in the emerald forest and the deep blue sea is invited to join.
(01-28-2021, 09:46 PM)DinoFan83 Wrote: (Assuming the assignment of the pneumatic vertebrae is correct, which obviously must be taken with caution until more complete specimens are found) I think that if the newly proposed lifestyle for the animal is correct, the pneumatic vertebrae would not be much of a hindrance. Their usage could fall in line with the previous suggestions in the thread for helping the animal stay afloat while it gets from place to place, and they wouldn't be a hindrance at all for a heron-like lifestyle.
It should be noted, however, that the lightly pneumatic neck the animal would have if those vertebrae belonged to it would have virtually no effect on the mass (in fact, it could be argued that the neck airsacs and the excluded gastroliths from Larramendi et al. (2020) cancel each other out). This is because, as stated before in the thread, animals like Aerosteon which were far more pneumatic would have already had very high densities, so there is no reason to assume such negligible airsacs would bring down the mass any significant amount.
IMPORTANT SIDENOTE: As per personal communication with SpinoInWonderland, his 186 centimeter MSNM v4047 skull reconstruction is outdated, and this is because he strongly suspects that he put it together using restored material instead of actual fossils.
This almost certainly means that Ibrahim et al. may have used restored material to estimate the skull length of the neotype given its similarity to that old skull reconstruction without knowing that they did. Palaeontologists are not immune to error and that may well have had occured here.
While I do think it's still more likely for the size difference between the 2 specimens to be 52.5% instead of 32.5% as I can only replicate the former with both restored the same, because the only way right now to restore the material with the same criteria is using those restored skulls, I think the safest bet would be limiting ourselves to specimens that can be estimated directly from overlap.
The only probable adult specimen we have that can be reliably estimated with overlap is NHMUK R-16421, which would be 10,830 kilograms based on the new density and SpinoInWonderland's size disparity between it and the holotype, plus the new density estimates.
TL;DR: While a 13.7+ tonne MSNM v4047 does appear to be the most likely option based on apples to apples comparison to FSAC-KK 11888, it cannot be confirmed due to simultaneous lack of overlap and lack of good material to fill that lack of overlap. Due to this, I would say it's best to refrain from giving it any estimates until 100% real complete skulls are described, instead using NHMUK R-16421 (which still fits very well in Ibrahim's 10-12 tonne estimate).
I feel a caveat with the pneumaticity is that it is not uniform. A pneumatic neck won't help the animal stay much afloat of the rest of the body is dense (which seems to be the case here). At best, the animal will have a floaty head/neck which can reduce the cost of elevating its head above water to breath but the body would still be a sinking rock.
Looking at these cross-sections, Spinosaurus matches most closely with those that spend a significant time submerged. The hippo for instance is not a fast moving dolphin (however, it can actually be deceptively fast) but spends a significant time in the water.
*This image is copyright of its original author
Dr. Ibrahim also made a great point to counter the most recent paper in this article, where he states:
"Nobody suggested Spinosaurus was a dolphin-like, lightning-speed predator … You have to look at the prey animals in Spinosaurus's river system, which include enormous coelacanths and other slow-moving aquatic animals... T. rex was not a fast runner, but it was fast enough to pursue a Triceratops or Ankylosaurus, and that's all that matters, folks.”
And from Dr. Pierce:
"To me, the combination of anatomical features indicates strong aquatic adaptations, a semiaquatic animal able to swim in water,” Harvard paleobiologist Stephanie Pierce, a senior author of the 2020 Spinosaurus study, writes in an email. “I don't think it was a pursuit predator as they very narrowly define it in the paper, but an animal that could presumably swim and lunge burst after its prey, catching it in the water column. They are getting swept up in definition."
Modern animals can help us figure out what extinct animals did. However, extinct animal do not have to exactly fall in line with what we see today and could certainly have developed their own unique adaptations.
