Spinosaurus aegyptiacus

[Acinonyx sp.]

Spinosaurus Aegyptiacus reconstruction by paleonerd (idea from Ibrahim 2020)

https://www.deviantart.com/paleonerd01/a...-841091211


[color=var(--D7)]Time to join the bandwagon, here’s my illustration of the new Spinosaurus that was recently published by Ibrahim et al. (2020). As I’m sure most of you are aware, the history of Spinosaurus is very long and complicated and I’ve already discussed it in a previous post. So I’ll just go over the recent discoveries, which are the most relevant.

In 2014 Ibrahim et al. described a new neotype skeleton of Spinosaurus, FSAC-KK 11888, which was discovered in the Kem Kem, Morocco. They proposed a semi-aquatic lifestyle for Spinosaurus based on the characteristics of its skeleton. Physical adaptations indicating a semi-aquatic lifestyle included, increased bone density compared to other theropods, flat-bottomed feet (possibly webbed) similar to shorebirds, reduced but powerful hind limbs (possibly used for paddling) similar to early cetaceans, eyes positioned towards the top of the head similar to crocodilians and a high concentration of neurovascular foramina on the snout, which could have housed pressure sensors also similar to crocodilians. The conical shape of the teeth and the elongated crocodile-like jaws also suggested Spinosaurus primarily predated on fish.

Ibrahim et al. (2014) also noted that, based off their flesh models, the centre of mass was positioned much further forward than in other theropods, more towards the ribcage rather than between the hips. This suggested that Spinosaurus was poorly adapted for bipedal locomotion and therefore must have relied on its forelimbs to support it’s weight while on land. This hypothesis was supported by the fact that the new specimen possessed highly reduced hind limbs compared to other theropods. However, Henderson (2018) refuted this by producing his own 3D models, which showed the centre of mass to be closer to the hips, suggesting Spinosaurus was still capable of bipedal locomotion. 

Henderson also challenged the semi-aquatic hypothesis by using his models to shows that because of its pneumatised skeleton and complex system of air sacs, Spinosaurus would have been unsinkable and would have more likely inhabited the shallow shorelines and was incapable of open water swimming. This was refuted by Ibrahim et al. (2020), who described the tail morphology of the neotype. The neural spines and chevron of the tail vertebrae were significantly elongated, which in life would have supported a fin or paddle like structure, much like the tails of crocodilians and newts. This strongly suggests the tail was used to propel the animal through the water, indicating a primarily aquatic lifestyle. Ibrahim et al. (2020) also confirmed that the entire neotype skeleton was from a single individual of the same ontogenetic stage and was not a chimera as some had suggested.

Note: This illustration is scaled to the size of the neotype specimen that was figured by Ibrahim et al. (2020) and mentioned in the supplementary data. This specimen was just a subadult and there are larger, more fragmentary specimens that most likely belonged to individuals in excess of 14 meters. [/color] Reply