fish

Wednesday, October 15, 2014

Behind the Research: Identifying a New Species of Fossil Fish

A fundamental part of being a scientist is publishing your research. Scientists ask questions, formulate hypotheses, rigorously test these hypotheses, and publish their research and their results. Other people can then read these results and build off of these studies, either to question or refute the findings, or to use the findings to ask other questions. It is how science grows and evolves. 

What almost all scientific publications lack, however, is the flair, the backstory, and general behind-the-scenes action that is part of everyday research. Scientific publications are whittled down to the most concentrated version, filled with the jargon of the discipline, and stripped of any extraneous behind-the-scenes anecdotes. So while any given scientific paper can be exciting to a scientist who wants to learn more about the organism or the methods addressed, they can be a bit unfriendly to a general reader.

So for fun, I have decided to tell some behind-the-scenes stories of the research I do, in the context of my published papers. Hopefully I give you a sense of what it is really like to be a paleontologist, and the work that is involved. 

I’ll begin with my two solo-authored papers that I published in 2013. The papers can be found here and here, and if you cannot access those journals, please contact me at szgibson@ku.edu and I will send you a PDF.

These two papers establish a new genus and two new species of fishes within a group called semionotiforms. Semionotiforms are an extinct group of fishes, but are closely related to living gar, and like gar, their bodies were covered with thick enamel scales (ganoid scales). Semionotiforms are found in geologic deposits worldwide, and range in age from Middle Triassic (~237 million years ago) to Early Cretaceous (~145 million years ago). A lot of variety occurs in semionotiforms in the shape of the body, the characteristics of the skull, the teeth, etc., and part of my research is to figure out what makes these particular fishes different from other species that have been described in the literature by other scientists. So you could say that my hypothesis for these studies is that these fishes represent new species, and I am testing that hypothesis by comparing the anatomy and morphology of these fishes to other semionotiform fishes to see if my hypothesis is correct or incorrect.

 

Some of the fossil specimens I work on are from museum collections, such as the American Museum of Natural History (AMNH) and the Smithsonian and were collected in the 1950s and 1960s, yet remained in these collections unstudied and undescribed for decades. I began working on these fishes in 2006, when I worked at the St. George Dinosaur Discovery Site (SGDS) as an undergraduate student intern and later as the prep lab and collections manager. The crew of staff and volunteers from SGDS had just gone out to a site in southeastern Utah and collected hundreds of fossils (outlined in Milner et al., 2006), but most of these fishes were not identified. So as I started cleaning the fossils (fossil prep—to be discussed in a later blog!), I started looking for characteristics that defined them as either new or belonging to a described species of semionotiform fish. While I worked on the new specimens, I looked at older literature, in particular a (1967) paper by an AMNH paleontologist Bobb Schaeffer, who mentioned collecting many semionotiforms from the same area but didn't describe them or give them names. So, in 2008, I went to the collections of the AMNH to look at those old specimens collected decades before and reexamined them, seeing which of them could be the same species as the new specimens the SGDS crew had just collected. I identified at least two different species, though there are likely more than that.

 

Now, identifying a new species is more than just a “Eureka!” moment. A scientist cannot know what is new unless he/she knows what already exists, and so scientists have to be very familiar with other scientists’ work in the field. An inordinate amount of any scientist’s time is spent reading books and papers, and I spent months pouring over scientific literature, some as old as 1820, to find the characteristics of other semionotiforms. As I looked at each bone on the fossil fishes from the AMNH and those newly collected from SGDS, I compared it to the same bones in other semionotiform fishes, and I had to look for similarities and differences. Eventually, I found a suite of anatomical and morphological characters that distinguished these fishes from all other semionotiform fishes, and I had enough to publish two papers on two distinct species. In these papers, I had to give an exhaustively detailed description of every single bone, and I mean EVERY bone (these fishes have hundreds of bones, dozens in their skull alone!) that I could see on the specimens, because other scientists, when trying to identify new species of their own, may turn to my work for comparison, and so my papers have to be provide as much anatomical detail as possible!

Next time….naming a new species!!

References

Gibson, S.Z. 2013a. A new hump-backed ginglymodian fish (Neopterygii, Semionotiformes) from the Upper Triassic Chinle Formation of southeastern Utah. Journal of Vertebrate Paleontology 33: 1037–1050. 

Gibson, S.Z. 2013b. Biodiversity and evolutionary history of †Lophionotus (Neopterygii: †Semionotiformes) from the western United States. Copeia 2013: 582–603.

Milner, A.R.C., Mickelson, D.L., Kirkland, J.I., and Harris, J.D. 2006. Reinvestigation of Late Triassic fish sites in the Chinle Group, San Juan County, Utah: new discoveries. In: A Century of Research at Petrified Forest National Park: Geology and Paleontology (Eds. Parker, W.G., Ash, S.R., and Irmis, R.B.). Museum of Northern Arizona Bulletin 62: 163–165.

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

Tuesday, August 10, 2010

Cleared and Stained

cleared and stined

Caiman latirostris — a crocodile

Some of our specimens, recently discussed in our post about specimens as snapshots in time, take on a unique role after entering the museum's collections. Certain reptiles, amphibians and fishes undergo a process called clearing and staining, which helps scientists look into the critters.

After being turned translucent by a digestive enzyme called Trypsin (found in the bellies of many vertebrates including us), dyes are added.  Bones and hard tissue are stained red with a chemical called Alizarin, and soft tissues are highlighted by adding Alcian blue. 

The contrasting colors help scientists study the morphology - the skeletal and skin structures - of an animal.  As an example, they prove especially useful for studying frog skulls, which undergo a peculiar dance of morphological change as frogs mature. 

Wednesday, June 2, 2010

On Cleaning an Ancient Fish

The word “fossil” often conjures images of Tyrannosaurus rex skulls, mammoth femurs, or other large bones. But those aren’t the only ones that survive through the millennia, and certainly aren’t the only ones that have importance.

KU Biodiversity Institute graduate students Sarah Spears and Kathryn Mickle study prehistoric fishes. Their fossils are so small that, in order to get them ready for study, Sarah and Kathryn have to use tiny tools to remove excess rock. Sometimes, even metal tools are too rough and inexact, so they switch over to porcupine quills — just sharp and flexible enough to clean tiny fish bones.

Wednesday, September 7, 2011

Waste Not, Want Not

fish

Like any good ichthyologist, I keep saltwater fish.  When I lost a Banggai cardinalfish recently, how did I deal with this tragedy? Not by flushing it or starting a pet cemetery, but by turning that loss into a gain for the Biodiversity Institute's Ichthyology collection. 

It is true that aquarium fish make less than ideal specimens.  It is impossible to get accurate, reliable information on the natural habitat, behavior, distribution, and population structure of such a specimen.  However, for large-scale genetic studies, a specimen without such data can still provide valuable insight into the evolutionary relationships among fish species.  Likewise, we can gain important morphological information to further inform our ideas on the evolution of structures like jaws and tails.

So how does a fish reach scientific immortality after passing on to the great aquarium in the sky?  First, and not surprisingly, it's important to get the fish into the freezer as soon as possible to keep it from decomposing (genetic material starts to break down quickly as the fish decomposes).  When we are ready to process the fish, we first take photos of it, since preservation often causes bright colors and patterns to fade. Then a small piece of muscle is taken from one side and added to our tissue collection--this leaves the other side of the fish intact for morphological studies.  We then inject the fish with formalin and store it in alcohol, or clear and stain it.

While at first blush this may seem perverse, my cardinalfish now lives on as frozen tissue and fluid specimens, where it will provide valuable genetic and morphological information for researchers and students.  I know I would much prefer that to being flushed.