On display this weekend: LACM’s monster alligator
October 6, 2011
Vanessa Graff and I spent yesterday working in the herpetology and ornithology collections at the Natural History Museum of Los Angeles County (LACM). The herpetology collections manager, Neftali Comacho, pointed us to this skull of Alligator mississippiensis. It’s not world’s biggest gator–about which more in a second–but it’s the biggest I’ve seen in person. Normally it lives in a big rubbermaid tub in the collections area, but this Sunday it will be out on display for Reptile and Amphibian Appreciation Day (RAAD) at the LACM. RAAD will include guest talks, tours of the collections, and live animal demonstrations. If you’re in SoCal and you’re into herps–or have kids, grandkids, nephews or nieces that are into herps–it will be well worth checking out. While you’re there, don’t neglect the newly renovated Age of Dinosaurs and Age of Mammals halls, which are frankly phenomenal: spacious, well-lit, loads of actual material on display, skeletons you can walk all the way around, informative but unobtrusive signage, tasteful integration with existing architecture…I could go on. Better if you just go and see for yourself.
About that gator. First the bad news. It came to the LACM from another collection, and has no data–no locality, no date collected, nothing. The skull is also missing all of its teeth, the left retroarticular process, the back end of the braincase and the occipital condyle. I think the latter losses were probably caused by a foramen of Winchester.*
Now, the awesome news. The length from the snout tip to the end of the articulars was 680mm and from the snout to the end of the quadrates was 590mm. Irritatingly I did not get a dorsal head length, which is the gold standard for comparative croc skull measurements, because I only reread Darren’s giant croc skull post after I got home last night. Going from the photos, I think the dorsal head length was right around 50 cm (beware, the yardstick in the photos is marked off in inches).
Darren’s post led me to this one, which has some very useful measurements (yay!) of giant croc skulls. The table at the end of that post lists alligator skulls with dorsal head lengths of 58, 60, and 64 cm, so the big LACM gator is nowhere near being the world’s largest. In fact, the 64 cm skull would be a quarter again as large, which is a truly horrifying thought. Still, it’s a big damn skull from a big damn gator.
You might get the impression that here in the Wedel lab we are shamelessly obsessed with giant saurians. And that is in fact true. But we also look at tiny ones, too. Here I’m playing with the skull of a little Tomistoma, the false gharial. Tomistoma is notable because another individual of the genus produced the longest skull of any known extant crocodilian–a whopping 84 cm dorsal head length (photos of this monster are in both of the giant croc skull posts linked above).
The moral of the story? If the sign says don’t go swimming, don’t go swimming. Go to RAAD instead, and see the giant alligator skull, and a ton of other cool stuff besides. And if you’re into gator skulls or just like geeking out on awesome anatomy, check out the 3D Alligator Skull site, a joint project of the Holliday lab and Witmer lab. Have fun!
* bullet hole
Sauropod Vertebra Picture of the Week 
October 6, 2011 at 11:44 pm
Pfft. A reminder, should anyone need it, that extinct crocs were way more awesome than any of the lame-ors we have these days: the reconstructed skull of Sarchosuchus in the Paris museum: http://www.flickr.com/photos/tyrrellmuseum/4526139919/
‘swhat I’m talkin’ about.
October 7, 2011 at 8:25 pm
So, is there a measurement (better said, an estimate) of the dorsal skull length (back of occiput to tip of snout)? It would be interesting to compare to the Maximum size estimated by Woodward & White (1995).
Woodward, A. R. and H. J. White.1995. Maximum Size of the Alligator (Alligator mississippiensis). Journal of Herpetology 29(4):507–513.
October 7, 2011 at 10:50 pm
So, is there a measurement (better said, an estimate) of the dorsal skull length (back of occiput to tip of snout)?
Yes, as stated in the post, I estimate the dorsal skull length for the big LACM gator at 50 cm.
It would be interesting to compare to the Maximum size estimated by Woodward & White (1995).
Already done! The data from Woodward et al. (1995) are included in the second linked post (this one) and quoted in my post above. The three largest skulls had dorsal skull lengths of 58, 60, and 64 cm. Hence my comment that the biggest of those was a full quarter again as long as the LACM skull. Really, it’s all in the post.
October 8, 2011 at 12:21 am
That Sarcosuchus skull that Mike Taylor linked to in the first comment has an awful lot of teeth: I count over 30 on one side of the upper jaw. What’s the current thinking on this critter’s ecology? Macropredators (Tyrannosaurids, for example) tend to have a smaller number of very big teeth, don’t they? Could Sarcosuchus have been a sort of super-gharial, specialized in hunting big fish? (Aren’t there some sizeable lungfish known from about its time and place?)
October 8, 2011 at 3:39 am
Interesting. Here’s another thought: maybe young Sarcosuchus filled the gharial niche, and when they got to a certain size they just ate whatever the heck they wanted. A specialized fish-eating dentition probably gains versatility when it’s two meters long and has more than a ton of force behind it.
October 8, 2011 at 3:17 pm
Large crocs do the weirdest things to their skulls. I’d love to know what was going on in the narial region of this guy (are the nares being vaulted up, or has the surrounding skull been eroded down?). It’s too bad that most of our data for crocs comes from animals that are either barely born, or barely adults.
October 8, 2011 at 5:55 pm
Yeah, this guy definitely has an upthrust narial region, but like you say, hard to tell if it’s build up or the surrounding bone is eroded down. Sort of the same chicken-and-egg problem we have some laminae in sauropods and other saurischians–are the laminae additive structures, or just what’s left after pneumatic resorption of the bone on either side, or both? It’s often darn near impossible to tell. The great existential crisis for skeletal morphologists!
October 8, 2011 at 9:09 pm
Matt, a gharial like predator changing to a more generalist predator as it ages is what actually occurs in living Tomistoma.
Small to medium sized ones eat fish but large ones eat prey up to the size of monkeys.
And a 6m plus one could presumably eat pretty much anything it wanted.
So something similar in Sarcosuchus seems quite possible.
And given the time crocodilians take to grow up a lot of selective pressure on jaw shape could involve the shape of sub adults jaws, with a tendency to just thicken the jaws as they age.
October 8, 2011 at 9:48 pm
I seem to remember that the nares rise like this in old Crocodylus niloticus. Now if I only could remember where I read that.
October 9, 2011 at 5:36 am
Matt, a gharial like predator changing to a more generalist predator as it ages is what actually occurs in living Tomistoma.
Small to medium sized ones eat fish but large ones eat prey up to the size of monkeys.
And a 6m plus one could presumably eat pretty much anything it wanted.
Ha! Cool! Thanks for the info.
I wonder how many more examples there are of this phenomenon, where a seemingly specialized bit of anatomy (in this case, long slender jaws) turns out to be good for all kinds of things once it passes some threshold of size or power.
Or, on the flip side, of things not being that useful until they pass such a threshold. An ankylosaur tail club was presumably a lot more dangerous once it was the size of two basketballs and had a 15-foot handle from which it could be swung. As an anti-predator device, it ontogenetically passed from ‘laughable’ to ‘annoying’ to ‘career-ending’.
October 9, 2011 at 7:27 am
Matt, that depends on the size of the predator, too! If you weigh ten pounds, a baby ankylo could really ruin your day by hitting you in the nose.
October 9, 2011 at 2:56 pm
“Really, it’s all in the post”
Oh! it´s really all in the post. Shame on me! I guess I´ll have to sleep more before reading, because I´m often missing most of the stuff.
October 14, 2011 at 6:32 am
[…] What’s even cooler than a monster alligator? […]
October 14, 2011 at 9:55 am
This is all good stuff guys- I’m doing Nature Live on Sunday and I’m taking the holotype of Rhamphosuchus crassidens into the studio. I’ve also got a saltie skull measuring 51 cm dorsally, which apparently makes the total body length 420 cm or thereabouts, and a cute female gavial skull. Now if only I could use that lovely big alligator skull…
October 14, 2011 at 10:44 am
Hey, Lorna, that’s neat. What channel is Nature Live on? Can we find it on iPlayer?