Ostra-blog 4 - Colymbosathon ecplecticos

Last week, somewhere near the top of my mental list of candidate species for ostra-blogs was Colymbosathon ecplecticos. A couple years ago, this species burst on to the ostracod scene, causing a global media event. Ostracodologists are not used to seeing their favorite animals in the headlines, so Colymbosathon caused quite a sensation. On Friday, Eric at The Other 95% generated a post, Who's Got the Oldest?, with Colymbosathon playing the prominent role. Eric described some of the species' vitals. Yes, it's the oldest fossil with identifiable male parts. Yes, its species name means "amazing swimmer with a large penis". Eric's post prompted me to make Colymbosathon the star of this, ostra-blog #4.

Colymbosathon first exposed itself to me at a scientific conference. I was immediately drawn to its rather prominent.... eyes. We were in Seattle in November of 2003, about a month before the Science paper was to be published, and cause the aforementioned media blitz. So it came as a complete surprise to me when the first picture of this 425 year-old fossil flashed on the screen. I remember a seeing on the screen a photo similar to Figure 1 below.



Figure 1. Colymbosathon ecplecticos, a 425 million year old fossil ostracod. Image copyright Science Magazine.


I study ostracod eyes, and I've dissected many of them. My attention went directly to the compound eyes. One is marked "le" in the figure above for "lateral eye". That's the left eye, the right eye is higher on this figure, just below the "H" in the figure.

This fossil was preserved about 425 million years ago in three dimensions inside a volcanic nodule. The scientists break open such nodules in search of interesting fossils. When they find one, they make an image of the fossil at the point it broke, and then grind away a tiny bit of rock (10 microns or so, if memory serves) and take another picture. Doing this procedure over and over again gives them a stack of images, which they can put together computationally to yield full 3-dimensional reconstructions of the fossils. For ostracods and other small animals, this is completely amazing. For most ostracod fossils, only their carapace is preserved, it's made of calcium carbonate. On a few fairly rare occasions the "soft parts" of ostracods are also preserved. (Soft parts refers to the non-carapace parts, even though they are not all that soft, having a chitinous exoskeleton). But even when soft parts are preserved, there were no cases where the full 3-dimensional structure was visible. With digital reconstructions, movies can be made, and specific parts of the animal can be highlighted or removed in order to view other structures.

Figure 2 - Computer generated image of Colymbosathon (side view). Different parts of the animal are colorized differently to make them easier to see. Faint parallel lines are visible, which is where the original was ground, 10 microns at a time, to yield an image stack of the 3-dimensionally preserved fossil. Image copyright Science Magazine.


It was obvious right away that this was something very special. It clearly impacted my own work on ostracod eye evolution. This marked the oldest ostracod compound eye in the fossil record, pushing back the date some 200 million years. In 2002, I published a molecular phylogeny of ostracods that shows that ostracods with lateral compound eyes are nested phylogenetically within multiple groups that lack lateral eyes. One possible interpretation of this is that lateral eyes evolved within Ostracoda (of course eyes don't evolve from nothing, so if this idea is true, many of the genes used in all animal eyes should still be present in the ostracod lateral eyes). Colymbosathon doesn't itself change these conclusions because it is a member of the same group (myodocopids) that today have lateral eyes. Nevertheless, the Colymbosathon fossil pushes back the origin of ostracod compound eyes quite a bit.

Of course not many other people cared about the eyes. They had other things on their mind. In particular, many journalists really rose to the occasion, devising many very entertaining headlines. Some of my favorites are below, and I've taken the liberty to put them into a few categories.

1. The "size matters" category

l

• Scientists Discover Ancient Gargantuan Penis
• Sea creature impressive in its maleness
• Well-endowed sea creature is nearly half a billion years old
• He's 425 million years old and clearly virile
• Male fossil makes a big impression

2. The "age before beauty" category

• Ancient penis brings fame to lowly fossil
• Oldest male fossil bares all
• World's oldest genitals found in Scotland

3. Wonderful alliteration category

• Phallic fossil found

4. And last but not least, the winkle category, a clipping of which hangs in the lab

• Fossilised shrimp has the oldest winkle in the world