Sophie's premaxilla

[Anthony]

Sophie is our 41 foot long Tylosaurus proriger that was recovered from the Taylor Group, near Waco, TX in 2004/5. We had recovered most of the skull after it was exposed and left to rot by another institution. Over the last few years, most of the missing parts have been recovered in the spoils pile, including a fragment of the right quadrate and finally, the premaxilla has surfaced.

Initial condition:


New premax! Note the gouges and abcesses on the snout.

[Mike]

Anthony,
Congrats... It's always nice to find the missing pieces.

That's a pretty awesome specimen... Those bite marks had to come from other mosasaurs.. nothing else in the ocean at that time was large enough to grab hold of a 40 foot mosasaur's snout and leave that kind of damage.

I'm still amazed at how much the frontal has grown posteriorly over the top of the parietal... That sort of overlap has to have something to do with strengthening the skull.  The bite force that a mosasaur that size could generate must have been enormous.

Mike

[JJ]

Great photos, Anthony.  Thanks for the sneak peek.

John

[Mike]

Here's what happens to a big mosasaur when it swims into a rock with it's rostrum...



The damage to the premaxilla was healing at the time of death, but notice the fracture to the suture between the premaxilla and the right maxilla.... and the first tooth in the right maxilla being crushed back against the second tooth.... Ouch!  That had to hurt!



But wait, there's more.... look at the upward bow in the internaral bar. ... this guy really smashed the front of his skull...



It's quite likely that the damage prevented it from eating well enough to stay alive....

(4 ft skull of Tylosaurus proriger from Logan County, Kansas - in the Hobetsu City Museum, Hokkaido, Japan)

Regards,

Mike

[Anthony]

The Platecarpus that I'm working on right now is missing a chunk of the tip of the "rostrum". I think it is postmortem though. With all of the foramen in the tips of the jaws for nerves, I would imagine that premaxillary damage would hurt a bit.

Question about the Japanese housed specimen: looking at the lack of both paleotopography and large rocks in Logan County, what did it break it's face on?

[Mike]

Anthony,
I agree that any damage to the front of a mosasaur skull would be painful... maybe that's why they were so nasty toward one another.... lots of mosasaur one-on-one damage out there.

I collected a partial skull of a very large Tylosaurus kansasensis years ago that had the tips of three Cretoxyrhina mantelli teeth embedded.... one each in the lateral sides of both dentarys.. and one on the dorsal surface of the premaxilla.  The skull had weathered out and was much worse for wear, so I wasn't too curious about what caused some damage to the end of the premaxilla.... years later I finally realized that the tip of the rostrum had been bitten off... probably by the same shark that left teeth embedded elsewhere.... There is also a large bite mark going across the premaxilla, roughly on the same track as the tooth/teeth that severed the bone.



Here's a top/down view:



There is no evidence of healing around any of the bite marks... Most likely the sharks were scavenging the long dead carcass of a big ol' Tylosaurus...

"Question about the Japanese housed specimen: looking at the lack of both paleotopography and large rocks in Logan County, what did it break it's face on?"

GOOD question........It probably wasn't any thing within several hundred miles of where it hit the sea bottom...  The map below shows some possibilities...
"X" marks the spot where the mosasaur was collected.... 1) The most likely (nearest) hard rocks are in the Arbuckle and Washita mountains of southeastern Oklahoma and southwestern Arkansas... they would have been exposed on the eastern edge of the seaway. 2) There is a source of "red quartzite" in northwest Iowa that Williston mentions as a possible area where plesiosaurs went to get stones they used as gastroliths (he also mentions the Black Hills, but I don't think they were exposed during the Late Cretaceous); 3) A large amount of granite is quarried in southeastern South Dakota... it was exposed at sometime during the Cretaceous because they find sharks teeth and reptile bones in the seams between the granite boulders in the quarry... deposited in the Carlile Shale; (4).... There is some sub-surface indications that there was a chain of volcanoes running from west to east between the Western Interior Sea and the Gulf of Mexico during the Late Cretaceous. Apparently they were eroded away fairly quickly and there's nothing left on the surface.



That all being said, the whole Western Interior Sea sat on limestones, sandstones and shales that had been deposited as sea floor over the previous 300 or so million years. We have no idea whether some of those formations may have been exposed during the Late Cretaceous... They certainly would be hard enough to have caused the observed damage...

Regards,
Mike