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Wednesday, February 18, 2015

New Paper: Evolution of multicuspid teeth in a Triassic fish from Utah

the holotype of Hemicalypterus, USNM V 23425, composite image of the part and counterpart.

Just yesterday, my newest paper was published online in the journal The Science of Nature: Naturwissenschaften about a rather unusual fish from the Upper Triassic Chinle Formation of southeastern Utah. The fish, Hemicalypterus weiri, was a deep-bodied, disc-shaped fish, with enameled ganoid scales covering the anterior portion of its flank, and a scaleless posterior half, which presumably aided in flexibility while swimming. Although Hemicalypterus was first described in the 1960s (Schaeffer, 1967), recent collecting trips recovered many new specimens of Hemicalypterus, and I decided to reinvestigate this enigmatic fish as part of my dissertation research.

While cleaning specimens of Hemicalypterus at the University of Kansas Vertebrate Paleontology prep lab, I noticed rather unusual teeth on the lower jaw that I had exposed from the rock matrix. These teeth look like a mouthful of little forks, and there were at least six individual teeth on the lower jaw. As I prepared other specimens, I found that these teeth were also on the premaxillae. Each tooth has a long cylindrical base and a flattened, spatulate edge with four delicate, individual cusps. I hadn't seen anything like this before in other fossil fishes, and so I started searching the literature and talking to other ichthyologists.

The multidenticulate teeth on the premaxilla of one of the specimens

Well, as it turns out, this tooth morphology has evolved multiple times in several independent lineages of teleost fishes, and quite often fishes with similar dentition scrape algae off of a hard substrate. These teeth indeed act like little forks (or "sporks" might be more appropriate) for these herbivorous/omnivorous fishes. Examples of extant fishes with similar teeth include freshwater forms such as the algae-scraping cichlids and characiforms, as well as many marine forms that are key in controlling algae growth in coral reef environments, such as acanthurids (surgeonfishes, tangs) and siganids (rabbitfishes). Of course, these modern-day fishes also feed on other things (e.g., phytoplankton), but algae is often the primary staple, and these fishes use this specialized dentition for a specific feeding behavior.

The same teeth as above, but under fluorescent lighting

So while it is impossible to prove definitively what a species of fish that lived over 200 million years ago fed upon (without gut contents being preserved....or a time machine), it is still safe to infer that Hemicalypterus occupied an ecological niche space similar to algae-scraping cichlids or other modern-day herbivorous fishes and may have scraped algae off of a hard substrate, based on this unusual tooth morphology and its similarity to modern forms. 

The multidenticulate teeth of a modern-day algae-scraping cichlid, Labeotropheus

This discovery also extends evidence of herbivory in fishes clear back to the Early Mesozoic, whereas prior to this discovery it was assumed that herbivory evolved in the Middle Cenozoic in marine teleost fishes. Frankly, there was no evidence to say otherwise, as most Mesozoic fishes have general caniniform or styliform (peg-like) teeth, or they have heavy crushing or pavement-like teeth consistent with crushing hard-shelled organisms. The teeth of Hemicalypterus are very delicate, and wouldn't really do well with durophagy. This is the first potential evidence of herbivory in the Mesozoic, and in a non-teleost, ray-finned fish.

Original Source: Gibson, S.Z. 2015. Evidence of a specialized feeding niche in a Late Triassic ray-finned fish: evolution of multidenticulate teeth and benthic scraping in †Hemicalypterus. The Science of Nature — Naturwissenschaften 102:10. 

Also cited: Schaeffer, B. 1967. Late Triassic fishes from the western United States. Bulletin of the American Museum of Natural History 135: 289–342.

Thursday, February 12, 2015

Herpetology Attends Sexy Science Event at the Museum

The KU Herpetology Division was in attendance at last night's Sexy Science event held at the Natural History Museum.  The event, which was very well attended, invited attendees to explore the suggestive side of natural history and hosted representatives from Herpetology as well as Entomology and Ornithology. Matt Buehler, Andressa Bezerra, Manuella Folly, Jackson Leibach and myself were there with a display of reptile and amphibian specimens which typify some of the fascinating reproductive biology in these organisms. For example did you know that some species of lizards are able to clone themselves? That's right. And you might be surprised that they can be found here in our own backyard. The New Mexico whiptail of the American Southwest is one well studied example. The entire species is composed of females which reproduce by cloning themselves. What makes them even more interesting is that the entire species is the result of a hybridization between two closely related species, the little striped whiptail and the western whiptail. This cloning phenomenon may actually occur more frequently that we thought. Species that typically reproduce through sex such as the copperheads, which are quite common around Lawrence, Kansas, have shown they have the ability to clone themselves as well.  Why they do so is still a mystery. A mystery that if solved may tell us something about the evolution of sex in animals.  

Matt Buehler talking about reproduction in frogs

Matt Buehler talking to some visitors about reproduction in frogs.

 

Jackson Leibach pointing out some snake hemipenes

Jackson Leibach pointing out the hemipenes of a reticulated python

Saturday, November 29, 2014

Field Safety


Before you can leave for the field, the US Antarctic Program (USAP) makes sure you are ready and competent in the science of safety. In order to get ready, G-496 sat through a half-day class on safety, taught by one of the resident guides Suz. She is a great teacher who has been down here for years. She covers things like how to stay warm, preventing frostbite and hypothermia, basic knot skills, and how to set up and use a camping stove. She also talks a little about helicopter safety. 


Then the next day, as a group we went out in a haglund (see below) with Suz and our mountaineer Dave Buchanan for a full intense day of practical field safety. Photo by Ignacio Escapa


First we learned glacier travel which includes how to walk on ice and snow and how to use crampons and ice axes . Photo by Ignacio Escapa 

Then we learned how to set up the tents we would be using in the field, as a team. This included anchoring the tent into the snow using a “dead man’s” anchor. After we got the tents set up, everyone who had been to Antarctica recently left for the warm of McMurdo and four of us (Charlies, Ignacio, Carla, and myself) stayed behind. 


Next we learned how to build an ice-wall to protect the camp from incoming wind. Photo by Ignacio Escapa


We set up the kitchen, and made dinner. Suz left us to stay in the warmth of the instructors hunt while we fell asleep out on the Ross shelf in our tents.  

The next morning we woke up to wind, which made everything more difficult. We had to, as a group, take down camp, pack everything away and be ready for Suz to pick us up. However, because of the wind and it getting colder that night, the haglund wouldn’t start. So we had to carry out everything on a sled to the road, were we could be picked up by a shuttle and return to the warmth of buildings, McMurdo and the rest of our group.  -Lauren Michel

Wednesday, December 3, 2014

Hiking around McMurdo

We have been delayed getting out to the field for a week now because of weather. When the clouds are
low or air pressure is bad, helicopters can’t take off, which is what has happened this week. A big part
of getting ready for the field in Antarctica is hurry up and wait. We landed and were thrown into
classes, field safety, getting food and sleep kits, and gear organized. We had to retrofit the rock boxes
so they wouldn’t fall apart. You have to get all of this done in the few days before you are trying to
leave for field work. If you are delayed, there is a lot of sitting around reading papers and trying not to
get to antsy for the field. One of the nice things about McMurdo is the great hiking you can do to keep
you busy and see the area a bit. This is what we have been doing this week.

Adjacent to McMurdo is the hut Robert Falcon Scott built in 1902 for his 1901-1904 polar expedition.
It’s just a short hike to visit the hut.

Anne-Laure and Ignacio (Nacho) on our walk out to Scott’s Discovery Hut.  Photo by Lauren Michel.

Scott’s Discovery Hut in the forground with McMurdo in the background. Photo by Lauren Michel.


The Discovery Hut is located right on the Ross Sea and there are usually seals nearby so there are some
good opportunities for some wildlife viewings. Photo by Lauren Michel.


Also right next to Scott’s hut is the start to the ridgeline hike. Photo by Lauren Michel. 


Another outdoor adventure is going to the observation tube, which is out in the middle of the Ross Sea.
You can crawl down and see jellyfish and ocean wildlife. Here's Erik heading into the observation tube.  Photo by Lauren Michel.


McMurdo Station and the New Zealand, Scott Base are situated on a volcanic island in the middle of the Ross Sea. The two stations are close together, separated by a road with a hill, so you can walk along the road to Scott Base if you want.  The hike to Scott Base with Observation Hill in the background. Photo by Lauren Michel.


Nacho and me with Scott Base in the background. Photo by Anne-Laure Decombeix.


When we got to Scott Base we were greeted with the Ross Sea ice coming up on Ross Island. It was one of the most beautiful things I’ve ever seen. Photo by Lauren Michel


On your way to Scott Base is the last of the hikes I’ve done, it’s called Observation Hill, or Ob Hill for short. This hill overlooks all of McMurdo and has a gigantic cross on top, that was erected in 1913 to commemorate Robert Falcon Scott’s party who died trying to reach the South Pole. The view from the top of Ob Hill looking down into McMurdo. Photo by Lauren Michel


Here I am next to the cross at the top of Ob Hill with the Ross Sea and Black Island in the background. Photo by Anne-Laure Decombeix

Tuesday, December 2, 2014

Discoveries in Curio Bay

Curio Bay
Before we even set off for Antarctica, 4 of us (Erik Gulbranson, Rudy Serbet, Ignacio Escapa and myself) made a reconnaissance trip to Curio Bay, New Zealand. Curio Bay is close to the southernmost part of the south island of New Zealand and is famous for the preservation of a 180 million year old fossil forest. Because what we are studying in Antarctica is roughly time equivalent, and Antarctica and New Zealand were close together in the southern part of Pangaea during this time, we thought it would be interestingto go study the forest of Curio Bay. Then we can compare what we are seeing in Curio Bay to what we are seeing in Antarctica.

What we found was quite interesting and a great start to the field season. Many papers have described forests at Curio Bay as being in situ with some of the logs may having been transported on a river. What we realized was that the forest of Curio Bay is actually 2 or 3 separate forests, with tree stumps now preserved in silica (or chert). Imagine a tree being dunked in epoxy and solidifying: this is the type of preservation process, except in stead of epoxy it is silica (quartz) that provides the cementing agent. 

Lauren taking notes.All of the knobs sticking up are fossilized tree stump casts. This area is a preserved area by the New Zealand government, which is similar to Petrified Forest National Park in the US; you can’t take any of the tree stumps casts, but you can study them! Erik is interested in what fossil trees record and can tell us about past climate changes. One of the ways he does this is through very carefully studying the tree rings that are now preserved in silica. He can take careful measurements of the widths of the tree rings using calipers and high-resolution digital images to a number of things: (1) cross date the trees to figure out which of the trees were growing together at the same time, (2) create a long (100 years or more) timeline of wood growth year-by-year for these trees that are ~180 million years old, and (3) interpret the variation in ring width over that long timescale (100 years or more) to interpret paleoclimate. Rudy and Ignacio (Nacho) are paleobotanists and are experts in plants of this time period and the evolution of plants over geologic time; they are also excellent field geologists/paleontologists. Lauren’s specialty is the study of fossil soils (paleosols) throughout geologic time.

Since Curio Bay is tidally influenced, time was an issue. We divided up the tasks with Rudy doing reconnaissance to find the best preserved stumps. Nacho would take careful photographs that Erik can study later, Erik would measure the rings he could get to with his calipers and I would take notes. We ended the day with the best discovery of all, a rare yellow-eyed penguin. A great end to the start of our field season! - Lauren Michel and Erik Gulbranson