This one is espescially for fossildude. How can you tell the difference in the skull material?
Background: I worked on the "bunker" T. proriger specemin back in the late 90s at KU, and I have ready access to the restored skull (about 20 feet from my workstation). I also have a disarticulated nerarly complete skull of a mystery mosasaur. Both skulls are nearly identical in size, about 6 feet in length. Big suckers.

Looking at the teeth, our Tylosaurus has 13 max, 13 dentary, and 10 pterygoid.

The mystery one, "Sophie", has 13 max, 13 dentary, and 11 pterygoid.

Sophie's quadrate is nearly identical to M. maximus as figured by Russell 1967, except for the articulation with the lower jaw, which is more robust in our specemin.

Frontals are very similar to M. maximus, though ours overlap the parietals, and have a hole for the pineal eye through both bones.

Here are a few photos that I haven't already posted.

Also who has some good references? I've primarily been using Dale Russell's 1967 Peabody pub. Kinda curious if anyone has anything else written in the past 40 years. Also, can someone PM me Takehito Ikejiri (Ike)'s email address? I lost it when my friend's email server crashed.

From these new pictures, the specimen looks a lot more tylosaur-like. The flattened, or low coronoids (Mosasaurus has a coronoid that has a high angle to it) Check out this Mosasaurus sp. skull at Oceans of Kansas:

http://www.oceansofkansas.com/Mosasaurs2/mor06-01.jpg

and the shape of the frontal (the pineal opening in M. maximus is far forward on the parietal emargination but not shared with the frontal). I'm starting to think that you have a Hainosaurus similar to the one I'm working on. That makes sense stratigraphically as well since Tylosaurus was extinct by mid-Campanian and M. maximus (hoffmani) didn't come on until the latest Campanian. I'll have to check some of the specimens around the collections and get back to you.

It's too bad that you don't have the premaxilla. The rostrum, if present, would be a dead give away.

My curator and I are having a wager on this. I chose Mosasaurus, so I'm really pushing for that. Unfortunately, the critter was washing out into a creek nose first so the premax is long gone. We're going to be showing the finished skull at Tucson this year, so the reconstruction should be done by the end of the year. We're currently molding the original bones, and then will be tweaking the casts.

I'm now leaning towards something close to Mosasaurus maximus. Perhaps a new species. Bakker pointed out that there are a few differences in the teeth between this critter and most mosasaurs, I'll take a photo on Monday.

Here's a pic of the left quadrate that I took recently. Mike Everhart (oceans of kansas) is getting a cast to help witht he ID, as well as another leading scientist.

Prefrontals look tylosaur like, as the postorbitals articulate into a socket in them, as opposed to the overlapping Mosasaurus condition. Dentaries have a bit of a "lip" forward of the first tooth, not sure if this indicates any rostrum or not, as it is variable in Platecarpus.

I'm about 80% done with the casting of the original parts, just finished the splenials and articulars/prearticulars this week. All that's left are the dentaries, maxillae, and braincase. Then the reassembly fun starts. The finished skull will be on display at Tucson in a few months.

New in National Geographic this month:
http://seabed.nationalgeographic.com/ngm/w...ek=2&priority=1


"Among the last great marine reptiles, Tylosaurus, shadowed by an offspring, drives away a shark, Cretoxyrhina mantelli, in North America's Western Interior Seaway. Part of a group of carnivores called mosasaurs, whose fossils are found on every continent, Tylosaurus measured roughly 45 feet (14 meters) long. Gut contents from one beast suggest that it scavenged sharks and perhaps even attacked them. However, recent finds of Cretoxyrhina teeth embedded in mosasaur vertebrae indicate that the reptilian predator also became prey—or at least suffered its share of scrapes. Sharks proved themselves true survivors, outlasting the extinction of all the marine reptiles, except sea turtles, 65 million years ago, when volcanic eruptions, climate change, and a meteorite impact ended the reign of the reptiles."

That NG article kinda ticked me off. Too much CG wgiz-bang, and of course, mosasaurs are an afterthought.

Update on my ID the critter quest. General consensus seems to be a tylosaur-ish kinda thingy. Checked some vert counts, we have all 7 cervicals, 21 or 22 dorsals, 3 or 4 pygals and 34 caudals. Haven't made the girdle/limb counts yet.

Finally done with casting the real bones, now we're on to assembling all of the parts into subassemblies for resto and recasting. I'll post more pics when we get closer to a finished product. I just really wish we had the premaxilla.

Does anyone have any photos of disarticulated vomers and palatines? I think we have them in a drawer, but I'l like to be sure before we sculpt them in case I have to mold something else.

Top of the skull is almost done! A little smaller than we first though, total length about 5 feet now. Lil baby.







Nearly ready to remold the assemblies. Lower jaws and ptery/vomer/plaatine assemblies should be done next week. Hopefully then I can get back to prep.

Tomorrow is the big day. We finished up the molding and casting for the first two casts today. Tomorrow we assemble and paint. Lower jaws are 5'2" long. Massive. Photos to come shortly.

I think what you have there is the tylosaur descendant Hainosaurus. My main reason for thinking so is that the pineal opening is shared between the frontal and parietal. In Tylosaurus the opening is contained entirely within the parietal.
Another feature to look for is the maxillary-premaxillary contact. In Hainosaurus the contact rises straight up from the tooth row then curves back posteriorly. In Tylosaurus the contact curves back posteriorly directly from the tooth row. I know that you don't have the premax but you still may be able to tell if the anterior part of the maxilla is present.
In any case, this is not a Mosasaurus because of a number of features. First, the flattened coronoids. Mosasaurus has a large large posterior process while tylosaurs are much lower. Second the suprastapedial process on the quadrate is too long and deflects medially. The medial deflection is another character of Hainosaurus. Ther are several other features but your specimen is missing a few parts
Many researchers don't believe that Hainosaurus is present in North America, however, I have inside knowledge that there are at least two species from the Pierre Shale. In any case, it's a great specimen you have there. Do you have any knowledge about the original's ultimate destination?

No idea as to where the original is going yet, however we're trying very hard to place it with an institution where it can be published on.

I'm convinced that if it is Tylosaurus (though Taylor group is a little high for that) that it is a new, different species than T. proriger. There are just too many differences all thru the skeleton. Heck, dorsals 1 and 2 have ventral swellings like the cervicals on most mosasaurs. The forelimbs are much larger than the hindlimbs. The humerus is so robust, it looks like a duckbill metatarsal. The radius is insanely huge as well. The hind limb is comparable to the KUVP "Bunker" T. proriger.

The maxillae are complete on the anterior part, and what you see in the photos are what is there, I did no restoration to them at that part. We did some straightening of the prosquamosals and postorbitals to get them to fit better, though the skull does still have a tweak to it.

Currently we've finished molding the skull, limbs, pelvis, shoulder girdles, all 7 cervicals and hypohyals, as well as all of the mostly complete cervical and dorsal ribs. We're done with the restoration of the dorsals (18 present, 5 will be duplicated in the mount) and once we get our order backlog in check, I'm off to the pygals. The tail is in very poor shape, though we recovered about 35 caudals. very few chevrons were recovered, and they all seem to be fairly poor as well.

This animal seems to be very old and very sick when it died. You really need to take a look at all of the pathological growth on the braincase. It has abcesses on the maxilla as well, perhaps a little snout wrestling going on. It is no doubt an exceptional specemin.

If you'd like more photos, just tell me what you want to see! Espescialy if you think it may be diagnostic. I'd love to finally figure out what this critter is.

I'll check out our Hainosaurus stuff here at SDSMT to see if it compares well with what you've already put on the Paleoboard. I'll try to get permission to post some photos of the different elements like the parietal, quadrate and premaxilla/maxilla contact. Getting permission might be difficult since the two of them haven't been officially published yet (only abstracts and talks).
Hainosaurus is very tylosaur-like in many features since it is descended from them, but quite different in other aspects like those you mentioned. It also lived from the Campanian through the Maastrichtian so stratigraphically yours checks out fine.

I think the only SDSM stuff Ive seen is what Mike Everhart has posted on the Oceans of Kansas website.

The main sticking point I see is that contrary to Russell 1967, our humerus is way larger than our femur. That's exactly opposite of what he described. I'd like to figure this out befre we make a skeleton with 25 fewer dorsals/pygals than it should have.

Excellent point. I'll try to find out a little more about our specimen's post-crania before I get back to you. :)

Right on. I'll get some photos tomorrow at work. The topic on this post has already been marked "image heavy" so a few more couldn't hurt. :P

Photos for your enjoyment:

From L to R, Tylosaurus napaeolicus, the mystery critter, and Tylosaurus kansasensis


Forelimb of the critter, note highly pathological radius (as per Everhart)


Proximal end of radius, and my fuzzy hand.