Saturday, May 28, 2011

Dorudon Was Not A Monster

The external shape of cetaceans is very much defined by blubber and other soft tissues†. In a previous article, I argued that if a cetacean were to be naïvely reconstructed by what the skeleton (or rotten carcass) 'suggests', it could end up looking more like a reptilian horror than, say, a fat, charismatic monodontid we all know and love. It's below the monstrous footnote.

† But don't just take my word for it - the Woods Hole Oceanographic Institution has excellent CT scans showing the interplay between skeleton and external shape. Aside from the caudal peduncle and (occasionally) the tip of the snout, toothed whales are cocooned in blubber. The heads of the False Killer Whale and Narwhal provide sufficiently extreme examples. Contrarily, the Minke Whale has a skull which roughly correlates with the external shape... in a dorsal view; shrink-wrapping the skull at a different angle shows that soft tissue still plays a considerable role in determining overall shape. Dorudon probably looked a great deal more like toothed than baleen whales, however more basal 'baleen' whales (stem-Mysticeti) lacking the hyper-derived skull are potentially very informative. Thanks to Markus Bühler for the link.

This intentionally incompetent Beluga bears an unexpected similarity to some reconstructions of Dorudon... notwithstanding the blowhole and fur, of course. This is partially due to the offending illustrations depicting Dorudon atrox with almost no blubber, which makes as much sense as reconstructing a fossil bird without feathers. The other factor is that skeletally, Dorudon is broadly similar to modern toothed whales, despite being basal to the toothed/baleen whale split:

Delphinapterus leucas skeleton from Wikipedia Commons.
Dorudon atrox2, taken and modified from Wikipedia Commons. Note that the arm is held at an angle and was not, in fact, really really short.
White-sided dolphin, taken and modified from Wikipedia Commons.

Above Dorudon is a Beluga, which is similar in size and also has non-fused neck vertebrae (Uhen 2004). What I find particularly striking is the similar depth of the ribcages and the comparatively short spinous processes of Dorudon. Beaked whales also have non-fused neck vertebrae and Ziphius in particular has been compared in size to Dorudon (Uhen 2004) - judging by this photo of Ziphius, the species also has a deep ribcage and relatively enormous spinous processes†. Below Dorudon is a Lagenorhynchus dolphin (either L. acutus or L. obliquidens) which has numerous highly derived characteristics (Buchholtz and Schur 2004), and thus makes for strong contrast. The ribcage seems relatively streamlined and shallower and the spinous processes of the vertebrae are extremely developed. There's still a broad similarity between Dorudon and that highly derived taxon, which makes portrayals of Dorudon as some anguilliform quasi-reptilian horror appear increasingly bizarre.

† Aside from which, the lumbar/anterior caudal region gives off a strong Basilosaurus vibe due to the elongated vertebral bodies and lack of interlocking processes. Hmm.

So why have I been talking so much about Dorudon atrox as opposed to D. serratus, Chrysocetus, Ancalecetus, or some other 'dorudontine'? Dorudon atrox is the best-known 'archaeocete', and at present "[r]elationships among the Dorudontinae are not well-defined, either by morphology or stratigraphy... [i]n addition, the relationships among the Dorudontinae cannot be determined until the taxa within the Dorudontinae are clearly delimited" (Uhen 2004). Additionally, it's become apparent that I've been citing Uhen (2004) quite a bit so far, and that source just so happens to be a massive, book-length treatise on D. atrox which is freely available. The publication is outstanding... aside from the frontispiece, which was credited as being made in cooperation with the author, but seems to contradict several points made within the publication and looks more like a zombie than a fairly close relative of extant cetaceans.

I think I can do Dorudon a bit more justice... next post.

Well, I've actually already done it for the banner - but the explanation will be in the following post! Which won't be in a month, I swear.


Buchholtz, E. A., and Schur, S. A. (2004). Vertebral osteology in Delphinidae (Cetacea). Zoological Journal of the Linnean Society 140, 383–401. Available.

Uhen, M. D. (2004). Form, Function, and Anatomy of Dorudon atrox (Mammalia, Cetacea): An Archaeocete from the Middle to Late Eocene of Egypt. University of Michigan Papers on Paleontology 34, 1-222. Available.

Tuesday, May 3, 2011

Picture of the Indiscriminate Interval #000003 - Invasion of the Sliders

Whilst I'm in the midst of designing the most flamboyant Cooter (turtle) ever and trying to not horrendously reconstruct cetaceans, I've decided to resurrect this nearly-forgotten gimmick to stymie the ol' blog from gathering too much dust. How has it gotten to one-post-a-month? I feel like I'm always in the process of writing something up.

At Brickyard Pond, Barrington, Rhode Island, I was in the process of stalking Snapping Turtles when I noticed what was unmistakably an invasive Red-Eared Slider (Trachemys scripta elegans) resting about a meter offshore in thick vegetation. Despite facing the shore, the head was retracted, and I was able to casually walk up to and capture the turtle before it started its futile escape dash. I was surprised to see that the little male (SCL ~ 12-13 cm) had its left arm amputated above the elbow.

Despite the horrendous-looking injury and the lackluster escape attempt, the turtle appeared to be in decent condition. Not having the capability to care for another Slider (see below), I returned the male back to its point of capture (roughly where the back end is pointing in the photo above), and was surprised that it made no attempt to flee, and did not even emerge from its shell for a few minutes. I had recently observed a large Snapping Turtle in the immediate vicinity, which makes me wonder if the Slider's presence so close to shore and apparent tenacity to hold its position had to do with the potential predator. Either that, or it was more damaged than what I had thought.

I cannot find any literature on the frequency of Trachemys scripta elegans losing limbs - let alone in an invasive context - however it has been occasionally documented in other species. As discussed in Sewer Turtles, some Phrynops geoffroanus individuals missing their forelimbs could survive and even feed themselves. Saumere (2001) observed a female Snapping Turtle in Quebec with both forelimbs amputated at the elbow nesting in two years out of three. For whatever reason, most literature on turtle limb loss concerns Wood Turtles (Glyptemys insculpta); one population from Quebec was observed to have amputation rates of 9.6% for a single limb and 3.2% for two limbs, which was comparable to rates reported in other populations (Walde et al. 2010). However, another Quebec population had 32.3% and 13% rates for single and double amputations, respectively, which may have been caused by either predator efficiency and/or density (Saumere and Bider 1998). The recapture rate for amputee Wood Turtles in a northern Michigan study was significantly lower for non-amputees, and while some were recaptured multiple times (Harding 1985), it would overall suggest that limb loss is a significant hazard to survival.

There's no way of telling just how the Slider lost its arm, although I'd say predation would be more likely that some run-in with a lawnmower or other equipment since the shell was unharmed. Any number of mammals could have been the culprits - as they have been for unfortunate Wood Turtles - although interactions with snapping turtles or even Blue Crabs (yes, they can live in freshwater) can't be ruled out either. I didn't really wan't to return the specimen, but I lack the capacity to care for such a turtle and have heard it is difficult to find anyone willing to accept Sliders of any sort. If anybody out there knows an exception, please let me know!


As for why I couldn't cram any more turtles into my life, I had already captured a female of possible breeding size (SCL = 19 cm) from the same pond. I had seen it around for a few months, although its shell did not have any readily-visible patterning and it was generally facing away from me, so I was not certain if it was a Red-Eared Slider or not. On one mid-November afternoon, I observed it rather unwisely basking in cool weather (45 F, 7.2 C) on a log ~2 m offshore while facing away from said shore. I'd be stupid not to sneak up on it, catch it, take it home, clean it off, and christen it as my new pet.

Kevin (named after actress Kevin Casey, of The Skydivers infamy) is still with me, although I'm honestly surprised. 165 days into my ownership, I noticed a piece of metal sticking out of the cloaca. Not knowing what to expect, I wound up pulling a sinker, line, and a partially-digested hook out of the turtle. Despite the potential to puncture internal organs from the hook and the line and the possibility of lead poisoning from the sinker, Kevin showed no signs of blood or really any indication that something that potentially-traumatic had just occurred. Still, it was probably lucky that it wasn't attempting to pass foreign object in the wild.

As for what damage a hook can do to a turtle, one snapping turtle which swallowed multiple hooks and a sinker was treated for lead poisoning and intestinal perforations (from the fishing line) (Borkowski 1997). There's not much information out there on non-marine turtles getting hooked, but I'd wager that a turtle surviving an internal hook with no obvious damage is one lucky punk.


Borkowski, R. (1997). Lead poisoning and intestinal perforations in a snapping turtle (Chelydra serpentina) due to fishing gear ingestion. Journal of Zoo and Wildlife Medicine 28(1), 109-113. Abstract.

Harding, J. H. (1985). Clemmys insculpta (Wood Turtle). Predation-mutilation. Herpetological Review 16, 30. Available.

Saumere, R. A. (2001). Limb Mutilations in Snapping Turtles, Chelydra serpentina. The Canadian Field-Naturalist 115, 182-184. Available.

Saumere, R. A., and Bider, J. R. (1998). Impact of Agricultural Development on a Population of Wood Turtles (Clemmys insculpta) in Southern Québec, Canada. Chelonian Conservation and Biology 3, 37-45. Available.

Walde, A. D., Bider, J. R., Daigle, C., Masse, D., Bourgeois, J-C., Jutras, J., and Titman, R. D. (2010). Ecological Aspects of a Wood Turtle, Glyptemys insculpta, Population at the Northern Limit of its Range in Québec. The Canadian Field-Naturalist 117, 377-388. Available.