Triassic Marine Reptile Skull

[Crazyhen]

This skull is from the Triassic Formation of Yunnan Province, China.  Any idea what kind of marine reptile is that?

 

 

[Crazyhen]

The lighter is the scale, that is, the skull measures about 10cm in length.

[pachy-pleuro-whatnot-odon]

Looks like an ichthyosaur, probably mixosaur, seen from below, no?

 

[Crazyhen]

Does it look like the mandibles are broken ?  Because it looks it has a pretty short mandibles for the ichthyosaurus found in the formation.

[pachy-pleuro-whatnot-odon]

7 hours ago, Crazyhen said:

Does it look like the mandibles are broken ?  Because it looks it has a pretty short mandibles for the ichthyosaurus found in the formation.

Yes, the rostrum is incomplete (in fact, only the very base of the mandibles remain). This is, in fact, not an uncommon occurrence in other deposits, as ichthyosaurs seem to have been frequently caught at the snout (I.e. rostrum bit of), or have landed on the sea-floor with a nose-dive, causing their rostrum to break off (though this, on some  occasions, has also led to exquisitely preserved skulls, even the rostrum bored itself into soft sediment, leading to better preservation).

[-Andy-]

Rotated and sharpened the image for you. I would cautiously say it's ichthyosaur. Is that particular quarry known for producing ichthyosaur fossils?

[Crazyhen]

6 minutes ago, -Andy- said:

Rotated and sharpened the image for you. I would cautiously say it's ichthyosaur. Is that particular quarry known for producing ichthyosaur fossils?

Yes, it’s from Fuyuan of Yunnan Province, in which many fish and ichthyosaurs are found.

[-Andy-]

2 minutes ago, Crazyhen said:

Yes, it’s from Fuyuan of Yunnan Province, in which many fish and ichthyosaurs are found.

 

I am trying to figure out if the eye socket is the huge circle on top or the small oval to the bottom-right of it. We can't rule out saurichthys

[pachy-pleuro-whatnot-odon]

51 minutes ago, -Andy- said:

We can't rule out saurichthys

 

As there's a mixosaur coracoid and clearly ichthyosaurian humerus right next to the skull, I'd say the case is quite clear. Besides, Saurichthys jaws look quite different, the skull being much more dorso-ventrally compressed...

 

Taken from Jiang, Schmitz, Hao and Sun, 2006. A new mixosaurid ichthyosaur from the Middle Triassic of China

 

 

Saurichthys sp. cranium taken from FossilMuseum.net

[Welsh Wizard]

I think the large opening is one of the muscle pitS on the top of the skull rather than the eye socket. Hard to tell tho’.

 

Nick

[pachy-pleuro-whatnot-odon]

1 hour ago, -Andy- said:

I am trying to figure out if the eye socket is the huge circle on top or the small oval to the bottom-right of it.

As to the circle at the bottom, I think this is where the maxilla has been displaced or worn away (hard to be sure), seeing as it's around the spot where the nasal should be. This bone is only very loosely attached to the jugal, lachrymal and premaxilla, so can easily get damaged or displaced. And the skull had obviously been crushed...

 

Drawing by Aubrey Roberts

 

 

 

As you can see from below image of a juvenile Stenopterygius sp. ichthyosaur, the orbit is quite large and the bones around it very frail.