"No vestige of a beginning, no prospect of an end..."

Nothing like a punk band quoting James Hutton. Did I mention their lead singer is a professor of evolutionary biology?

Suchomimus (Baryonyx?) tenerensis manual ungual I description attempt.

So, having read that describing a bone is one of the best ways to learn its features well, this is something I wrote up last night. Obviously it's a cast, but it's a very well done cast, so most of the features I describe should be in the real bone.

I'll note that because my access to the kind of literature I need to make any kind of comparative basis is currently limited (at least until the Fall), I've only focused on the features of the claw itself, and not how they relate to other theropod dinosaur groups.

With that said, I'd appreciate any comments/tips you may have!

*****

The element, a robust left manual ungual I missing the distal tip (which is fractured at a point transversely distal from the ventral margin of the articular facet and flexor tubercle), measures 190 mm in a line perpendicular to the articular facet and 305 mm across its convex, recurved dorsal margin. Its ventral portion, with the exception of the flexor tubercle (which is convex and robust in form), is flattened across its length. Distinctive rugosities cover the ungual's surface, though they are most apparent on the posterior regions. Possibly due to erosion, these pits are shallower on the medial side of the bone than on the lateral one.

A deep groove extends from the dorsomedial margin of the flexor tubercle, terminating just posterior to the missing distal tip. At its inception, this groove is placed in the lower 1/3 of the dorso-ventral complex, a form maintained for 3/4 of the claw’s curvature. However, this placement rapidly migrates dorsally at the 3/4 point until it reaches the top 1/3 of the bone. The groove reaches its maximum width halfway through the claw’s total length. A similar groove can be found on the lateral side of the claw. However, this groove is much deeper, a feature that may also be in part due to erosion of the medial surface. The lateral groove differs substantially from the medial one in that it thins radically to a ‘crack-like’ form 3/4 of the way through the medial groove’s duration.

The flexor tubercle is large and robust, being subequal in width to the dorsal margin of the articular facet. Its form, whose posterior margin is placed anterior to the articular facet, is subtriangular in both posterior and ventral views. A deep, median ridge divides the articular facet, which is oval-shaped in posterior view. The ventral portion of this ridge is especially bulky, being twice as thick as the maximum width reached by the midline. The articular surface for the condyles of the penultimate phalanx is deeper on the medial side than its lateral counterpart. Given the overall proportions of the ungual and its articular surfaces, the phalanx to which it was connected in life was likely equally robust.

The problem with interpreting trackways--redux.

I want you to imagine for a moment that you are a wildlife photographer observing a waterhole in the Serengeti. The waterhole is positioned roughly 50 feet from the open plains. Much of the pool is surrounded by a thick belt of vegetation, with the exception of a 15 foot stretch of soft muddy shoreline. Given that this is the only water source in several miles, you tentatively assume that it would be a good place to capture photos of the various creatures native to the area.

As your luck would have it, after only a few minutes of waiting, a zebra approaches and, being wary of predators, approaches the hole for a drink. The zebra drinks its fill, and almost as quickly as he came, is gone. A moment later, another zebra approaches from the same direction, spends a short time drinking (from a spot 5 feet adjacent from the first zebra), and also departs the way he came (after all, it's easier to walk across the sandy beach than transverse through the thickets).

Then finally, just before you call the day to a successful close, a final zebra arrives for the much needed water, drinks what it needs, and walks away.

Looking at the tracks left behind by the animals, you begin to wonder: what would somebody who had only seen the traces they left while walking to and from the pool have thought? After all, these were animals that were roughly the same size, walking at roughly the same speed, spaced roughly equally from each other (4-5 feet between trackways), and all with similar goals/geographic restrictions. You know that they were three lone ungulates. You saw them yourself! But somebody, were they to visit this hole themselves would not have this information. It would be a reasonable conclusion that they walked in together.

Now, in this same thought experiment, transport yourself several millions of years into the future. The plains have long since gone, and the pool long dried. An observer (human or otherwise), while hiking through the now uplifted sediments derived from this pool sees these tracks. Unlike the previous viewer from the past, this person doesn't have access to the past geographic constraints. He doesn't know of the thick vegetation that proved to be such a limitation to the zebras. All he sees are three sets of tracks, each equally spaced, and formed by the same variety of foot, all walking in the same direction, turning in the same direction, and leaving.

He has several conclusions that he can make: either a. the track makers were walking in formation of a group of three, or b. there was a single track maker followed by two track makers (or vice versa). or c. there were three individual track makers, each of which either independently arrived at the waterhole at the same time and left at different times or arrived at different times and left at roughly the same time.

The point is: how can he possibly decide between these? Each scenario, though very different in life, would leave an identical trace. He may decide that they traveled as a group, or he may decide that they were individual creatures on their own schedules. The most he can accurately say is that it is possible that the track makers traveled as a group.

Of course, many more track makers over a much larger distance traveling for a much longer length of time would make the possibility of a group derived trackway more likely. But, like Schrödinger's cat, we won't be able to know without the possibility of doubt until we observe

the event. Problem is, we don't have that option.

First lecture was a success!

And only two people walked out when I used the word 'evolution.' Go me!

Ever just wish there was a biologist out there to listen?

Well, as luck would have it, there is!

As a child, I was always hyper enthusiastic about asking questions regarding the natural world; some were answerable by the non-experts at hand, but many sadly were not. Dave Hone from Dave Hone's Archosaur Musings and others have put together an online resource to do just this. They've got a mix of categories in which questions can be placed, each of which have been flowing with questions and answers in the last several days.

So, if the inquisitive muse moves you, go out there and Ask a Biologist!

The problem with interpreting trackways...

Modified from Myers & Fiorillo 2009.

Wow.