|
Spinosaurus News ~
|
The numerous spinosaurus's looks, even during these last ten years that never stops... From now it becomes the first 100% aquatic dinosaur !
Are the indeterminate Spinosaurid vertebrae now S. aegypticus after Smyth et al. (2020)? I ask the thoracic vertebra in that was not pneumatized.
(12-17-2020, 06:30 PM)DinoFan83 Wrote: Here is a size comparison between the 2 most famous specimens of Spinosaurus and Carcharodontosaurus. Also, I am sure this is in here somewhere and I've missed it, but those are the largest estimates for Spinosaurus I've seen. What are the sources/derivations? 
@tigerluver
It is based on the discrepancy between the new skull reconstruction in Ibrahim et al. 2020 for the neotype (122 cm) and SpinoInWonderland's estimate for MSNM v4047 (186 cm). Given that FSAC-KK 11888 and MSNM v4047 do not overlap, this is based on general similarities between the full skull reconstructions, and it looks to me as though both have been restored using criteria that was very similar if not the same. Comparing both of them, it seems to me that the size difference between the 2 specimens is very likely 52.5% instead of 32.5%, and this is further supported by the fact that they are about the same shape; MSNM v4047 does not look any more elongate which would be misleading to go off of were it the case. As for the thoracic vertebra, I believe that yes, it's parsimonious for it to be S. aegyptiacus in light of Smyth et al. (12-18-2020, 12:50 AM)DinoFan83 Wrote: @tigerluver Could you please direct me to the page with the estimation described. I can't seem to find it in SpinoInWonderland's page
That's actually an independent estimation on my part - although it should still stand, SpinoInWonderland had made that skull restoration well before the neotype was found, and the similarities between his restoration and Ibrahim's new skeletal lead me to the conclusion that the size difference could have been greater than what Ibrahim suggested. In his current skeletal he uses Ibrahim's estimate for the size discrepancy, but this is because as far as I am aware he simply has not tried to look for a different best fit between the 2 specimens recently.
What are the foundations these many skull restorations? I note there are just fragments and the neotype skull is extremely fragmentary. I forget the name of the study, but I recall there was some reconstruction based on sister taxa. Have we had any more specific basis since?
I know that at least one of them (SpinoInWonderland's original restoration) is 100% Spinosaurus material; he superimposed it on the privately owned skull of which there is a picture on Wikimedia Commons. Given its similarity to what SpinoInWonderland managed to achieve, Ibrahim's reconstruction likely uses a complete and privately owned skull as well.
(12-18-2020, 03:02 AM)DinoFan83 Wrote: I know that at least one of them (SpinoInWonderland's original restoration) is 100% Spinosaurus material; he superimposed it on the privately owned skull of which there is a picture on Wikimedia Commons. Given its similarity to what SpinoInWonderland managed to achieve, Ibrahim's reconstruction likely uses a complete and privately owned skull as well. Thank you! I have seen that but am not comfortable trusting the specimen. So many skulls in private collection are overly restored if not fake. Has there ever been a report authenticating that specimen? Looks almost too good to be truly complete since excavation. Quote:So many skulls in private collection are overly restored if not fake. Has there ever been a report authenticating that specimen? Looks almost too good to be truly complete since excavation. Unfortunately, I don't think there has been a report on that skull yet. However, if thefossilforum's take on the criteria of this is anything to go by, I think it is most likely unrestored given that we can actually see the individual skull bones unlike the very uniform framework of skulls we know are composites. IMO, the similarity of the skull in the new model from Ibrahim and colleagues supports this as well as it's very unlikely that they would be using a reconstructed skull put together from who knows what over the actual material (for example, an unpublished but well preserved skull that they themselves found).
New paper on Spinosaurus that proposes a heron-like approach over an aquatic pursuit predator.:
The ecology of Spinosaurus
^That's a very interesting find, tigerluver. If what Hone and Holtz propose is correct, it's possible that the tail was used to get the animal from fishing spot to fishing spot instead of for actually hunting the fish themselves. Such a purpose would also be consistent with the relatively poor propulsion of the tail compared to animals like newts that the paper reviewed, since a spinosaurid does not need newt-level swimming to get from fishing spot to fishing spot.
I'm curious what Ibrahim would think of the paper, but now we have more than 1 plausible lifestyle for this animal.
An interesting new paper on a possible second Spinosaurid from Kemkem:
New mid-cervical vertebral morphotype of Spinosauridae from the Kem Kem Group of Morocco
I tried to allocate the vertebrae that can hint at pneumatization in Spinosaurus as this seems to be a big part in which lifestyle this species utilized. Please correct or add to following:
FSAC-KK-18122: In Lakin and Longrich (2018). Posterior cervical vertebra (C9). "Deep pneumatic openings at the base, most notably on the posterior surface." Attributed to S. brevicollis in the original paper. FSAC-KK-7280: In Lakin and Longrich (2018). Cervical vertebra (C5 or C6). "Each of the lateral surfaces carries a large central pneumatic foramen." Attributed to S. aegyptiacus in the original paper. FSAC-KK-18121: In Lakin and Longrich (2018). Partial anterior thoracic vertebra. "There is no central pneumatic foramen, nor is the parapophysis present on the centrum." Attributed to an indeterminate Spinosaurid in the original paper. FSAC-KK 11888: In Ibrahim et al. (2020). For the caudal vertebrae, "Although the centra are hollow (as seen through several broken surfaces), there is no evidence of foramina to suggest that the caudal vertebral series was pneumatised." Attributed to S. aegyptiacus in the original paper. The holotype: In Rauhut (2003), it is noted that "the dorsal vertebrae of the type of Spinosaurus aegyptiacus lack the strong pneumatisation and additional laminae seen in both Baryonyx and Suchomimus."
(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). (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. 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. |
| Users browsing this thread: |
| 4 Guest(s) |