New paper on Irritator

[Faelrin]

Detailed breakdown of the skull, etc. Paper here:

https://palaeo-electronica.org/content/2023/3821-the-osteology-of-irritator

[Flaffy]

That's so cool. I wonder if anyone will be brave enough to tackle an articulated Irritator with this "pelican mandible" included!

I wouldn't mind a static figure displaying this feature either of course, one instance where I'd prefer a gaping maw on a theropod. Apparently this anatomical quirk wouldn't be unlikely in other derived spinosaurids either? So would be cool to see it on spinosaur figures going forward.

[Dynomikegojira]

So Irritator is Shin Godzilla now. Man these spinosaurids are amazingly bizarre.

[Flaffy]

So Irritator is Shin Godzilla now. Man these spinosaurids are amazingly bizarre.

Kinda but not quite. I don't believe the dentaries would've had snake-like abilities of detatching from each other.

[laticauda]

Imagine a toy where the mouth actually expands like that when opened. 

[Saarlooswolfhound]

That is so intriguing! Another "weirdo" for the spinosaurid family tree!

[stargatedalek]

More like pelican bill than snake jaws, still very cool.

[Dynomikegojira]

So Irritator is Shin Godzilla now. Man these spinosaurids are amazingly bizarre.

Kinda but not quite. I don't believe the dentaries would've had snake-like abilities of detatching from each other.

Ah cool none the less.

[Carnoking]

It's always something new with these dudes.

[DinoFan2010]

I like adding frog-like throat pouches to my spinosaurid drawings, but now I gotta start drawing them with pelican throats!

[Blade-of-the-Moon]

Imagine a toy where the mouth actually expands like that when opened. 

Someone email Mattel..Deluxe Action Irritator!

[Shane]

So, a lot of the paleo-art people have made in the wake of this show the lower jaw in a sort of Blade 2 or Shin Godzilla situation...but what would it actually look like?

Pelicans can widen their lower jaws but it still "connects" at the tip. Would it look like that? Or more "egg eating snake"?

I'm intrigued by this but I feel like most of the depictions are going in a more sci-fi direction.

[Flaffy]

So, a lot of the paleo-art people have made in the wake of this show the lower jaw in a sort of Blade 2 or Shin Godzilla situation...but what would it actually look like?

Pelicans can widen their lower jaws but it still "connects" at the tip. Would it look like that? Or more "egg eating snake"?

I'm intrigued by this but I feel like most of the depictions are going in a more sci-fi direction.

Excerpt from the paper discusses this:

""As the mandibular symphyses of spinosaurids are unfused and show the typical, rather unspecialized morphology of most theropods (Stromer, 1915; Charig and Milner, 1997), indicating that the jaws were held together anteriorly by soft tissues (Holliday and Nesbitt, 2013), a certain lateral expansion of the jaws with lateral stretching of the connective tissue situated in the symphyses might have been possible (see Charig and Milner, 1997; Sereno et al., 1998; Holliday and Nesbitt, 2013; Hendrickx et al., 2016).""

Minor degree of lateral flexibility is not out of the question, but definitely not to the extent of snakes or Shin-godzilla.

[Shane]

Excerpt from the paper discusses this:

""As the mandibular symphyses of spinosaurids are unfused and show the typical, rather unspecialized morphology of most theropods (Stromer, 1915; Charig and Milner, 1997), indicating that the jaws were held together anteriorly by soft tissues (Holliday and Nesbitt, 2013), a certain lateral expansion of the jaws with lateral stretching of the connective tissue situated in the symphyses might have been possible (see Charig and Milner, 1997; Sereno et al., 1998; Holliday and Nesbitt, 2013; Hendrickx et al., 2016).""

Minor degree of lateral flexibility is not out of the question, but definitely not to the extent of snakes or Shin-godzilla.

Thanks, that helps put it in perspective. So, would this kind of flexibility suggest a throat pouch or something similar, based on contemporary comparisons? Or is that too speculative? I'd love to see paleo-art that focuses on that aspect rather than some Predator-esque mandibles.

[Flaffy]

Excerpt from the paper discusses this:

""As the mandibular symphyses of spinosaurids are unfused and show the typical, rather unspecialized morphology of most theropods (Stromer, 1915; Charig and Milner, 1997), indicating that the jaws were held together anteriorly by soft tissues (Holliday and Nesbitt, 2013), a certain lateral expansion of the jaws with lateral stretching of the connective tissue situated in the symphyses might have been possible (see Charig and Milner, 1997; Sereno et al., 1998; Holliday and Nesbitt, 2013; Hendrickx et al., 2016).""

Minor degree of lateral flexibility is not out of the question, but definitely not to the extent of snakes or Shin-godzilla.

Thanks, that helps put it in perspective. So, would this kind of flexibility suggest a throat pouch or something similar, based on contemporary comparisons? Or is that too speculative? I'd love to see paleo-art that focuses on that aspect rather than some Predator-esque mandibles.

Another excerpt discusses the implications of this jaw mechanism:

"However, this setting would need considerable muscle effort of the abductors, including the m. depressor mandibulae (see above). This is because the lateral expansion of the lower jaw would create additional tension on the bone and the adductor muscles, including the m. pterygoideus ventralis (inserting on the ventral surface of the prominent lateral surangular shelf) of the internal adductor musculature. Reaching the point of maximal tension, the relaxation of the abductor muscles would reinforce the contraction speed of the adductor muscles, further supporting the hypothesis of a very rapid jaw closure. In summary, the skull morphology of Irritator indicates fast, rather than strong biting, supporting previous studies on skull strength and bite force in non-avian theropods (Henderson 2002; Therrien et al., 2005; Rayfield 2011)."

So it seems like the primary purpose would've been to reinforce bite strength and speed. Just from skimming I don't see the paper particularly discussing anything relating to a specialised pouch of sorts. So in that regard it would be speculative. I personally don't find it unlikely, as with most anatomical features, they can have primary and secondary functions. The secondary function for this increased mandibular flexibility may very well have been to accomodate prey swallowing.

[Shane]

Another excerpt discusses the implications of this jaw mechanism:

"However, this setting would need considerable muscle effort of the abductors, including the m. depressor mandibulae (see above). This is because the lateral expansion of the lower jaw would create additional tension on the bone and the adductor muscles, including the m. pterygoideus ventralis (inserting on the ventral surface of the prominent lateral surangular shelf) of the internal adductor musculature. Reaching the point of maximal tension, the relaxation of the abductor muscles would reinforce the contraction speed of the adductor muscles, further supporting the hypothesis of a very rapid jaw closure. In summary, the skull morphology of Irritator indicates fast, rather than strong biting, supporting previous studies on skull strength and bite force in non-avian theropods (Henderson 2002; Therrien et al., 2005; Rayfield 2011)."

So it seems like the primary purpose would've been to reinforce bite strength and speed. Just from skimming I don't see the paper particularly discussing anything relating to a specialised pouch of sorts. So in that regard it would be speculative. I personally don't find it unlikely, as with most anatomical features, they can have primary and secondary functions. The secondary function for this increased mandibular flexibility may very well have been to accomodate prey swallowing.

Awesome, thanks for doing the digging. These papers tend to make my brain glaze over with academic language, so I find it hard to parse out the details.

[Blade-of-the-Moon]

Is this similar to the cranial kinesis found in some ( maybe all? ) Abelisaurs?

[spinosaurus1]

Is this similar to the cranial kinesis found in some ( maybe all? ) Abelisaurs?

sorta. both abelisaurs and carnosaurs have impressive levels of skull kinesis. with irritator, it looks to be fundamentally tied to how far it opens its jaws. In contrast, it would only be very noticeable with abelisaurs when they're swallowing a large prey item whole. the mandibular kinesis in irritator would have been more like that of a pelican

[spinosaurus1]

[Blade-of-the-Moon]

very interesting.  Thank you!