Figure 1: Bluegill (Lepomis macrochirus), also known as the bane of my undergraduate existence, a common sight in lakes of the eastern USA. (Public Domain)

I study living fishes. So what am I doing at UMMP?

     I’m a research fellow in UMMP, even though my career as a biologist thus far has focused exclusively on living animals—specifically fishes. Some of them may even be in a pond in your backyard (Figure 1). Honestly, before I came to U-M, I’d virtually never even seen a fossil outside of a museum exhibit, let alone had one sitting on my desk (Figure 2). So why on earth do I find myself here, amid the rocks-nee-critters and discussions of long-gone environments? I suppose that’s a long story, but here’s the abridged edition:

Figure 2: In the interest of full disclosure, the fossil in the top panel is not on my desk. But we have ones just like it. The fossil is of Belonostomus muensteri, an extinct fish from the Jurassic that is NOT closely related to modern needlefishes, such as the specimen Xenentodon canciloides, (UMMZ 192955) shown in a radiograph in the bottom panel. (top: user ghedoghedo on wikimedia commons, under a CC-BY-SA 4.0 license; bottom: K. Feilich)

     My interests center on the evolution of biomechanical systems, specifically how fishes and other critters interact with their physical environment. This kind of work lies intersection of biology, physics, and engineering. For the past few years, I’ve been looking at how body shape affects a fish’s ability to swim through the water. This might seem trivial. After all, fishes are found swimming on or around all seven continents—how hard could swimming possibly be? Common though it may be, water is actually a pretty tricky material to move through. For example, here’s a quick quiz. Which of the following is true about water:
A) Water is over 50 times more resistant to flow (viscous) than air.
B) Water is almost 800 times denser than air.
C) Water holds about 30 times less dissolved oxygen than air per unit volume.
     Did you choose answer A and/or B and/or C? Congrats! They’re all true. These features impose serious constraints on the shapes fishes can be to move effectively through the water. And despite this physics-induced difficulty, fishes come in many, many different shapes and sizes. Which raises the question I’m working on: why do fishes in any given environment have a particular set of body shapes?

Figure 3: If your ancestor was a slender fish, you'll probably be a slender fish. If your ancestor was a deep-bodied fish, you'll probably be deep bodied.

But what does any of this have to do with paleontology?” you ask, wondering about the digression.

     Well, on the surface, none of it appears to do with paleontology at all. But if you think about it, physics is not the only driver of fish body shapes in any modern environment. Some – maybe even most—of body shape is due to the evolutionary heritage of a species. This is the consequence of ancestry: if an ancestral species has a particular body shape, odds are its descendants will have that shape too (Figure 3). Evolutionary heritage over the long term—this is the stuff of paleontology.

     In addition to short term species adaptation to the modern environments, the shape of a modern fish may reflect adaptation of its ancestors to their ancestral environment. For example, kettle lakes in Michigan today formed from glacial deposits from about 10,000 years ago. That means any species in these lakes has only been adapting to that specific environment for a maximum of 10,000 years—ancestrally, they may have come from a river system. 10,000 years sounds like a long time, but that’s an evolutionary drop in the bucket—especially when other fish communities may have been evolving in place for much, much longer. This too, is paleontology.

            When it comes right down to it, there’s almost no way to study large-scale evolutionary patterns in a trait as complicated as body shape without thinking about paleontology. So here I am, a so-called “neontologist”, in a paleontology museum, doing my absolute best to understand how modern fishes have evolved in response to their current environments, while accounting for the many and varied historical processes that affect that self-same evolution. Wish me luck!

(More on Kara's work visit here: