There's been a lot of chatter about Spinosaurus recently, thanks to the new revelations about its tail morphology, but I think Mark has put together the best overall argument for what the new papers tell us and what that means for reconstructions. Also, as ever, he's created an amazing illustration. In brief (and with the caveat of as the evidence currently suggests):
- Bipedalism looks likely to be the main form of locomotion, based both on tail weighting and position/size of neck and hindlimb musculature;
- How – or if – Spinosaurus swam is still unclear and the new tail doesn't necessarily help with objections based on buoyancy modelling, but these calculations should be redone. Basically, it's still really weird and unlike anything extant, so we can't really make definitive claims;
- The sail is basically confusing. Depending on what fossils you prioritise, it could be S-shaped or C-shaped or somewhere in between the two. This is muddied by the question of whether the new specimen is a distinct species from the holotype or not;
- Mark has revised his earlier misgivings around tail flexion, particularly as to whether it could be used in a sculling motion like newts or crocodilians do. It looks like the neural spines are thin enough to both withstand and forgive the level of flex required, so they wouldn't snap or overpower musculature. That said, there's still some debate here as the paper itself claims a minimal tail musculature, so perhaps it was more rigid than implied;
- Lips are still very viable and there is little evidence to suggest the jaws were much more specialised than other theropods.
In short, we don't know a lot, but we know a little more than we did. I still like the idea of Spinosaurus as a Cretaceous mega-heron though 😁
