The Hero Shrew!

I think that I've had my fair share of cryptozoology and anecdotal evidence. Things don't have to be gigantic or monstrous or poorly supported to be interesting. Being incredibly unusual helps though. I remember reading Walker's Mammals of the World a while back and coming across a strange account of a species of shrew able to withstand a man standing on it with no ill effects. An accompanying picture showed an absolutely bizarre spinal column with "armor" mostly on the thoracic vertebrae. With the magical power (to me) of access to journals both home and abroad, I've been able to track down the supremely named Hero shrew, Scutisorex somereni Thomas 1910.

Despite being so strange, the unique spinal morphology wasn't recognized until 7 years after the shrew was described and little information was learned for the next 80 years (Cullinane et al., 1998). There seems to be a long history of interesting things being found in Museums, of all places. Scutisorex was hypothesized to be related to the genus Sylvisorex judging by dental characteristics, although molecular evidence suggested that it diverged from Sylvisorex cf. konganensis and S. ollula in the mid-late Miocene (Querouil et al., 2001). The paper notes that the morphology of shrews is difficult to interpret clade-wise, so a polyphyletic genus is not a surprise - the possibility that the hero shrew is not even a distinct genus is shocking. The spinal column is remarked upon as being the most modified among vertebrates (Cullinane & Aleper, 1998); that evolving within a genus would be astounding. More molecular studies will probably clarify the position of the hero shrew, but regardless it seems that the unique spine evolved very suddenly. Something definitely punctuated the equilibrium here.

So what exactly is so unique about the hero shrew's anatomy anyways? Wikipedia's image demonstrates that this armored shrew is completely unremarkable looking externally and looks roughly similar to anything else that is small, mammalian and scampers around. The spinal column is a different matter entirely. The vertebrae count is the mammalian norm for the cervical (7), thoracic (14), and sacral (5) regions, although the lumbar region has 11 vertebrae, as opposed to the normal 5 (Churchfield et al., 2007). I'd be curious what sort of mutation led to this not-quite-doubling of vertebrae. In the mid to end thoracic and lumbar regions the vertebrae have been fundamentally modified: the lateral part of the vertebral arch have been modified into interlocking bony plates (Churchfield et al., 2007). Cullinane et alii's noted that a wide range of mammals (rodents, "insectivores", a didelphid and a gray "fox") studied had spines taking up 1.08% the body mass on average (all within one standard dev.), while this shrew's spine took up 3.97%, seven standard deviations above the mean. The ribs and skull are also more robust than is expected, although the appendicular skeleton is not. While fossorial mammals typically deal with loads by developing the appendicular skeleton; anecdotal and structural evidence indicates that this hero shrew can withstand enormous pressure, reported at 1000 times the mass of the shrew. In an accompanying paper, Cullinane & Aleper discuss the spinal musculature, something which has of course also been undescribed beforehand and hindered mechanical analysis. The most radical change was that the transverse spinalis group has been reduced, apparently due to the tubercles on the spine resisting torsion and shear, which the muscle group does in other mammals. Some of the other spinal muscles were also highly modified and the authors suggested that they could be considered new groups. Cullinane and another author (Bertram) later studied the intervertebral joints of the species and noted that the spine represents the only known bone-on-bone articulation in mammals and is capable of withstanding 4-5 times more torsion than a normal mammalian spine. While the specifics of the mechanics involved in these tests is out of my league, it is clear that this is one remarkable animal.

Taken from Cullinane & Bertram, 2000, Fig. 1. The genetic testing revealed Crocidura to be a fairly close relative, and shows the normal shrew, and to some degree mammalian, condition.

Why this species has such a modified spine is a mystery. The species is only present in the Eastern Democratic Republic of Congo and neighboring Rwanda, Burundi and Uganda where it is not common (and rather elusive) (Churchill et al., 2007). Churchill et alii's study attempted to determine the spinal modifications by determining its diet and thus determining its habitat. This large shrew species was found to be opportunistic but focused on earthworms, a rare trait for an African shrew but common in large temperate species. With its unspecialized limbs and diet, it was determined to be a partially subterranean (not fossorial) feeder, like many other shrews. The only possible specialization for this way of life was an unusually long digestive tract (possibly to digest worms), although the spine/rib modifications were not explainable.

Cullinane & Bertram wondered that if there were no known behavioral or ecological correlation to this structure, which there don't seem to be, then "perhaps complex morphologies can evolve without selection driving their adaptive trajectory." This is a rather astounding idea, what if the cause of the bizarre spine morphology is nothing more than a few simple mutations? Does it give any benefits to this species? Since it is noted as being uncommon, perhaps it doesn't...or perhaps it is recent enough that benefits are not entirely apparent. Maybe if given enough time this could evolve into a distinct group of mammals - Cullinane et al. 1998 conjecture that "this species may represent a breakthrough in the morphology of the tightly constrained structure that is the mammalian spine". That is an awfully exciting idea, a future radiation of mammals started by the Hero Shrew! Or not, it could always be an evolutionary dead end, a bizarre evolutionary "experiment" of sorts. If this truly did evolve within a genus, or at least very closely related to species, then it may represent an absolutely fascinating case study in punctuated equilibrium.

I can tell that something is up with me that I'm more far excited by this shrew than the notion of a super-gigantic-snake-mimicking-Amazon-archeocetes or whatever. What have I become...

References:

Churchill, S. 2007. Feeding ecology of the armored shrew, from the north-eastern Democratic Republic of Congo. Journal of Zoology 273, 40–45. Available: Here

Cullinane, Dennis M. et al. 1998. The functional and biomechanical modifications of the spine of Scutisorex somereni, the hero shrew: skeletal scaling relationships. J. Zool., Lond. 244, 447 -452. Available: Here

Cullinane, D. M. & Aleper, D. 1998. The functional and biomechanical modifications of the spine of Scutisorex somereni, the hero shrew: spinal musculature. J. Zool., Lond. 244, 453-458. Available: Here

Cullinane, Dennis M. & Bertram, John E. A. 2000. The mechanical behaviour of a novel mammalian intervertebral joint. J. Anat. 197, pp. 627-634. Available: Here

Querouil, Sophie et al. 2001. Phylogeny and Evolution of African Shrews (Mammalia: Soricidae) Inferred from 16s rRNA Sequences. Molecular Phylogenetics and Evolution. Vol. 20, No. 2, pp. 185–195. Available: Here

This is what Conway Morris actually believes.

The history of Supersnakes and historical Python sp. range.

One of the major catalysts for my previous post was discovering that a supersnake hypothesis of sorts had actually made it into an academic journal. Unlike reports of outsized boids in the 20-30 foot (6-9 m) range, supersnakes are far outside the recorded or projected maximums. It has been hypothesized that supersnakes are a new subspecies or species, possibly a Pleistocene relict or even a non-snake. Distinctive characteristics suggesting a new species outside of size are rare, and it should be noted that large snakes are prone to wild exaggeration. Murphy & Henderson mention that large snakes already have mechanical problems, so a theoretical supersnake would have to overcome pumping blood to extremities and blood pooling in the tail. Rectilinear locomotion will presumably become impractical at some size, so a supersnake may also have to be entirely aquatic. Unless one presumes that Gigantophis* has had unrecorded examples of very outsized specimens, there is nothing to indicate a snake or snake relative has gotten much larger than 10 meters. So for numerous reasons I find it extremely improbable that one of the largest living or recently living animals is an undiscovered species of extremely big snake.

*Not in the snake crown group, although it was a constrictor. Mosasaurs, which aren't are a sister group to snakes, were the largest squamates at 15 meters long.

Stothers 2004 did not discuss the mechanical or ecological implications of supersnakes, but instead suggests that a population of large pythons existed in Northern Africa and Southwestern Asia - where they do not live today. Another focal point of this paper is that historical evidence of giant snakes (aside from mythology and interpreted animal remains) has had a huge effect on serpent lore. Since this affects the history of the sea serpent and perhaps the giant anaconda reports, this should be of interest to cryptozoology. The author rhetorically asks if we are "dealing with zoology or cryptozoology", although to me it clearly falls into the latter category (as we shall see). Peer reviewed articles on cryptozoology, in journals I can find, are exceedingly rare, so I find the very existence of this article interesting. Oh yes, and it mentions the cetacean centipede.

Ancient literature on giant serpents is apparently quite sparse until the Bagrada river incident of 256 B.C. where Regulus and his troops met a monstrous serpent. After it ate several men, it was fired at with javelins and darts which had no effect. Eventually its spine was crushed with a rock fired from a ballista and it was overcome with spears. When it died, according to one author, its corpse polluted the landscape for a considerable time. The 120 foot skin was then brought to Rome, allegedly measured under the instruction of the Senate, and was viewed as "an object of wonder to all". The description of the "feet of the ribs" (which don't actually move) made it clear this was a boid using rectilinear locomotion, although aside from that observation I do not find most of this story trustworthy. The story was apparently used to foreshadow the defeat and capture of the general in the following year by some, making it something of a legend. The detail of it repelling darts (or arrows) and javelins also seems rather unrealistic. I agree with Stothers that we can probably discount that this was an outright fabrication or that the animal actually was numerous crocodiles, the anatomical details hint at a real snake being involved somewhere. The author suggested that the length in feet may have been confused for rib "feet" somewhere along the line. The world's largest snake skeleton (22 feet, 26 originally) appears to have far in excess of this number, so I find this possibility very unlikely. The final option, the one Stothers plumps for, is that snakes two millennia ago actually could reach 120 feet in length. He probably should have discussed exactly how big a "foot" back then was anyways, and that snake skins can be stretched to 140% the original length while carefully avoiding stretching (Murphy & Henderson 1997 p.25). After reading through the reports, I've become cynical enough to suggest at least a preserved skull (and preferably the rest of the skeleton) to demonstrate snake size.

Size is not the only issue involved, the presence of a large snake (Python sp. ?) near the Mediterranean is remarkable enough as it is. Supposedly Ptolemy II Philadelphus had a 45 foot "Ethiopian" snake, although he may have actually had 21 and 19.5 foot snakes. Stothers suggests that the lengths may have been combined (and further exaggerated), and if this actually was a trend it could have huge implications for the other stories. This and other stories from Africa and Arabia support the notion of large indigenous pythons.

India is known to have giant snakes (Python molurus), but Stothers discussed stories from this region regardless. During Alexander the Great's conquests in the sub-continent, a king supposedly possessed two snakes well over 100 feet, although since only the "head" was seen, Stothers thinks this may have been something of a joke. Alexander himself supposedly displayed a 75 foot long snake, but Stothers suggests that this and other large reports may have been something of a "circus-show hyperbole". In one incident a report of the maximum size of Indian snakes was exaggerated from 24 feet to...500 feet! This might even be worse that giant squid claims. While there's nothing to suggest a range or size extension, these stories of "ox-swallowing and elephant-toppling" snakes undoubtedly had an effect on the image of giant "serpents".

Apparently this fifth century B.C. Greek gem was meant to show a connection between snake observations and serpent legend - I don't see how.The crest and structures behind the "neck" suggest and oarfish to some degree (and its pelvic fins). I assumed the archetype for a maned serpent originated much later and further up north...

As the above picture indicates, Stothers moves from "terrestrial" serpents to sea serpents. He says that ancient reports of sea monsters rarely resembled modern ones (the above one excluded apparently) and had a variety of causes. "Large snakes" or the impression of them, can theoretically be caused by some sort of weather phenomenon, large fish and whales. While not relevant to our theoretical population, this still effects the image of supersnakes. I must comment upon Stothers insistence that fish continue to grow until they die - even if a fish continued to add weight at a steady rate (which I really doubt) the cube law would make the fish grow less and less per amount of weight added. His reference to "some prehistoric sharks" reaching 100 feet in length (!) is either an incredibly outdated reference to C. megalodon or related to Richard Ellis' suggestion that Parahelicoprion grew that large (A notion I have never heard discussed or mentioned elsewhere). Despite the subject, Zoology isn't really too focused upon in this paper. The author's affiliation with NASA and very little information online about him puzzles me even further...

Oh yes, the Scolopendra aka cetacean centipede aka many-finned makes an appearance. Two rarely mentioned references are mentioned: the rib of a thousand-footed specimen from Italy was mentioned by Theodoridas and another mutilated 48-foot specimen mentioned by Antipater. Stothers mentions speculations that it (Aelian's original mention) may have been a 120 foot whale with suckfish attached to a belly or ripples appearing as if many fins are at work. The giant squid was mentioned as a (dubious) candidate, demonstrating its inevitability while discussing sea monsters. Despite the author's claim, one group of extinct fish did have numerous fins, although it is undoubtedly a coincidence. Exactly why this bizarre creature was mentioned is not very clear. It is later suggested to be "possibly related" to African serpents, despite not really being described as serpentine. The only possible connection I could think of is that the numerous ribs of snakes could be confused for actual appendages in a rotting carcass. The insistence that it doesn't fit in with any of Heuvelmans' categories is strange (since it was partially defined with the original sighting).

Looking over everything, I'd say this paper definitely falls under the category of cryptozoology. The discussion of snakes and snake-like creatures and their place in the development of snake lore is interesting, but I think it could have been covered in a separate paper. Tales of giant Indian snakes and cetacean centipedes and their implications lead away from what is truly interesting, a unique Python sp. population. The snakes could be relatives or members of the Indian P. molurus or sub-Saharan P. sebae (hence sp.), and it is not clear if their ranges were larger or they were actually brought over by humans. It is possible that a unique species was involved as well, and I'm surprised Gigantophis wasn't brought up (since it lived in Egypt - in the Eocene). Heuvelmans made mention of giant snakes from North Africa, which wasn't brought up either, but it appears there is more evidence to support the existence of this population. So here we go, a potential new species that allegedly reaches large sizes, a supersnake of sorts I suppose. Stothers suggests that ancient pythons may have reached larger sizes and that while there is not proof of snakes over 45 feet long, "it is hard to deny categorically that they actually existed." It is hard to deny, but also impossible to prove. As demonstrated numerous times, the size of large snakes is prone to exaggerations or outright lies. If even estimates from a few years ago can be dubious, I sincerely doubt the accuracy of reports several thousands of years old. It is possible for species in the past to have had more common large specimens, although there is no physical evidence for snakes far exceeding the maximum known sizes today. Historical evidence can have its uses in Zoology, but I think that describing new, possibly very large species is beyond what it is capable of. It does give us a clue where to look for large python bones, and all somebody has to do is dig up a few bones.


And yet again, another conclusion that we need more information to really make a conclusion.



References:

Stothers, Richard B. 2004. Ancient Scientific Basis of the "Great Serpent" from Historical Evidence. Isis. 95: 220-238. Available: Here

Murphy, John C. & Henderson, Robert W. Tales of Giant Snakes. Krieger Publishing Company; Malabar, Florida; 1997.

Giant snakes and Supersnakes of the Amazon

Here is a photograph that has actually been discussed seriously by at least one author and on the Internet of course:

A Brazilian postcard c. 1932. Note the coincidentally Gray-like profile in the background; why this hasn't sparked outlandish theorizing yet is beyond me.

Information about this alleged supersnake is rather variable, never a good sign. Heuvelmans reports it to be 30m long and 60 cm wide with a weight of 2 tons. When it was getting killed under machine-gun fire, it reared up 9 meters to crush bushes and small trees. Murphy & Henderson gives a much more detailed report of a 32 m by 1.25 m 3 ton snake with "horrid huge eyes". Both connect it to the photo. Then there is this drawing I found on Cryptomundo (no indication of source) which gives the wrong date and re-imagines this photograph to look a lot more convincing. It should be obvious to everybody why the photo didn't turn out like the drawing; should being the key word. Tim Dinsdale (whom I suspect is behind the drawing) believed that the large eyes, mouth and "thickness at the sixth convolution" indicated this to be an unknown species. Murphy and Henderson, who literally wrote the book on giant snakes, suggest it was just decomposed. Oh, and although 2-3 tons sounds like a lot, a 100 foot anaconda would weight somewhere between 10-25 tons.

Welcome to the world of giant snakes and supersnakes! Giant snakes are very large specimens of known species, while supersnakes are proposed unknown species or subspecies that have obtained extremely large sizes. Like sea serpent reports, it has been suggested that some of the supersnake legends have some rather non-snake-like characteristics, further muddling things. This covers both Zoological and cryptozoological ground, although with anecdotal evidence and mysteriously vanishing physical evidence it is more in league with the latter. Despite little evidence supporting the existence of outsized snakes, an African supersnake hypothesis of sorts has been published in a peer reviewed journal fairly recently. I'll discuss this later, but let's get back to giant anacondas.

The green anaconda (Eunectes murinus) is apparently the most massive species of snake and is frequently associated with Amazonian waterways. Murphy and Henderson consider it a giant snake (i.e. known to exceed 20 feet/6 meters), but exactly how big it gets has been a matter of dispute. Pritchard's Rule anticipates a record-sized snake is 1.5 to 2.5 times as long as the minimum adult female length (10.5 ft/3.2 m), so 8 m/26 feet is the presumed maximum for green anacondas. It should be taken into consideration that the maximum sized snake should be nearly 16 times as heavy as the minimally sized one, making for a rather impressive range. Pritchard comments that anacondas are not a rare species and thousands have been measured, and surprisingly even 20 foot specimens are considered rare. Presumably the average is somewhere around 15 feet/4.5 m; I wish publications listed averages and maximal sizes separately - before writing this I was under the impression that 20+ feet was normal. As hinted at by the first report, there have been many reports of anacondas over 9m/30 feet, and some several times even that length. So were there ever really snakes that big?

Estimating the lengths of snakes is often difficult and prone to extreme exaggeration. When one Ralph Blomberg heard about a 12 meter snake skin from an Ecuadorian military commander he was rather disappointed to find out that it actually measured 6 meters. Writer Hyatt Verrill recounted an incident where numerous people estimated the length of a coiled anaconda at 20-60 feet long - it turned out to be a monstrous 19'6" (and 360 pounds/163 kg!). Savage-Landor recounted an incident where he estimated a snake to be 100 feet long judging by girth, although it turned out to be 18'5" after it was shot and measured. It had of course swallowed an entire deer and the author speculated that immensely wide trails had a similar cause. Then there is the case of Fragrant Flower, a python that allegedly measured nearly 15 meters in an Indonesian zoo which actually turned out to be 6.5-7 meters long. So effectively eyewitness accounts of giant snakes, even at very close proximity, cannot be trusted.

Teddy Roosevelt's famous offer of 5,000 dollars for a snake exceeding 30 feet has been collected, and it is doubtful that such a specimen will ever turn up. Murphy and Henderson speculate that anacondas in the rain forest may get 7-8+ meters (23-26 feet) in length due to their need to overpower large prey, although I doubt the species can now get much larger than that. There are lots of stories about animals in the not-too-distant past attaining very large sizes (2.4 m otters, super-gigantic basking sharks, et cetera), so, unless these are all exaggerations, perhaps the green anaconda and large pythons* reached somewhat larger sizes into historical times. But 40-50+ footers, well, they're probably too outsized to be any living species.

* The Burmese (Python molurus), Reticulated (P. reticulata), and African Python (P. sebae) are of comparable if not greater length than the green anaconda, which weights more though. Their stories aren't as frequently exaggerated, nor does the same "supersnake" type story occur.

The largest fossil snake is the 9.3-10.7 meter (30-35 foot) Egyptian Gigantophis garstini, so the usual prehistoric survivor paradigm in cryptozoology doesn't really apply here. This size range, at least the lower end, appears to be reachable by outsized pythons. If this is an average length for Gigantophis though, this implies that outsized freaks of this species could have been veritable supersnakes. There's no evidence of this of course. As far as we know, the green anaconda is the most massive snake we have good evidence of, well, sometimes.

It appears that very large anacondas, both real and not, may have gotten mixed up to some degree with reports of the Sucuriji Gigante. One Father Heinz both saw and collected stories of this cryptid, which he had once mistaken for a steamship. It is allegedly incredibly fast (10-15 times as fast as a boat), was very aggressive, had phosphorescent eyes (or eye in one case), had huge teeth in its lower jaw, and pushed around vegetation mats rather than move around it. The fact that it had its mouth open at all is noted as being unusual by Murphy and Henderson. They suggest that none of these characteristics are snake-like, but don't further suggest what it could be. Heuvelmans explicitly suggests that primitive whales may be behind reports, and some of Heinz's reports do resemble sea serpent reports. Murphy and Henderson follow with an account of an alleged 56 foot anaconda that also had phosphorescent eyes (and was allegedly killed). And if you recall from the very beginning of this post, the "giant" anaconda allegedly had glowing eyes again. I don't think that there's much to support the idea of non-snakes getting intertwined into things, it just seems like people added more "horrific" characteristics to an already gigantic and potentially frightening animal. There still is a remote possibility that the Sucuriji Gigante could have been from a fourth anaconda species or a subspecies of E. murinus. But like most things cryptozoological, there's very little evidence and a lot of speculation.

I won't pretend that I can make a conclusion on this matter yet. Animals obtaining notably larger sizes into quite recent times is a frequently mentioned tend, although one I have difficulty finding documentation of. There's also the idea of a Pleistocene relict subspecies/species, although if there ever was a larger species of anaconda, I don't see it continuing to survive without the megafauna it presumably preyed upon. Is it even plausible to have a larger anaconda? Presumably it would be a specialist tapir/manatee/boto/large caiman predator. And then there's the ability of people to exaggerate the length of snakes up to five-fold. The Sucuriji Gigante is even more mysterious than oversized anacondas, although hardly a notable cryptid in its own right. It could just be based off of incredibly exaggerated anacondas. I suppose all we can do is wait and see if some monstrous sub-fossil vertebrae show up, or not.

I've barely scratched the surface on giant snake and supersnake reports from the Amazon. I'd recommend my references, particularly Murphy & Henderson, for more information on these sorts of reports. While these aren't exactly the most plausible of reports, they still are rather entertaining.

And yes, there was that one peer-reviewed article on African supersnakes I have yet to cover...

References:

Heuvelmans, Bernard. On the Track of Unknown Animals. John Wiley & Sons Limited, third English edition, 1995.

Murphy, John C. & Henderson, Robert W. Tales of Giant Snakes. Krieger Publishing Company; Malabar, Florida; 1997.

References:

Heuvelmans, Bernard. On the Track of Unknown Animals. John Wiley & Sons Limited, third English edition, 1995.

Murphy, John C. & Henderson, Robert W. Tales of Giant Snakes. Krieger Publishing Company; Malabar, Florida; 1997.

Addendum:

Señor McCormick's siesta is interrupted by an expertly (and painstakingly) rendered Sucuriji Gigante.

An Original Concept

How on earth has it been almost a month since I've last posted?

With the semester coming to a screeching halt, I suppose I just got a little too caught up in work. I haven't had time to finish any lengthy posts, all I have are quite a few extremely rough drafts. Oh yeah, and numerous papers on the death penalty, ugh.


Anyways, to use a concept you're unlikely to see anywhere else on the internet; I've decided to revolve this post around a mysterious picture:

Amyda cartilaginea. Taken from this page by Indraneil Das and Ghazally Ismail. I hope me using this is okay...

I've shown this photograph to several people, and they've had no idea what this animal is. The consensus is that it is some sort of fish (perhaps eel)-like creature, although that is far from the mark. It is....

A softshelled turtle of the family Trionychidae. To see what the whole creature looks like, go to this gallery here. Instead of writing out a full post on this group, Darren has already written an article. Yay, less work for me. As for articles directly pertaining to this species, I was unable to find any, unfortunately. However, the book Turtles of the World by Franck Bonin, Bernard Devaux and Alain Dupre (2006 edition) was able to fill me in. I was actually inspired by the head of Dogania subplana (which is even more fish-like) in the book, although I was unable to find a good image online.

This is a large species, with a carapace reaching 80 cm (~30 inches). Bonin et al list a record of a 202 kg (~450 lb) captured in Thailand in 1987, though this sounds very similar to a female Chitra captured in 1986. Even if this isn't as big as a Hoan Kiem turtle, it is still very big for a freshwater turtle, probably getting somewhere in the 30-40 kg (60-80 lb) mark.

The long snout of this and other species are due to a habit of burying themselves under sediment with only their nostrils sticking out. Softshell turtles are capable of pharygeal and cutaneous respiration, and at least some species can obtain all their oxygen from the water using these methods, see here. The "soft" shells are actually as resistant to damage as those of other turtles and they effectively allow the turtles to have a lighter shell more able to be bent by muscles (to close on the head and limbs), be more streamlined, decreased mineral needs, improved camouflage, and allow cutaneous breathing (Alibardi & Toni 2006 and Scheyer et al. 2007). So long for no literature.

Back to Amyda, it is a nocturnal, predatory species that feeds on fish, frogs, shrimp, and water insects. Although The Crocodiles and Turtles of Borneo lists it as being common, Bonin et al note it as being heavily caught for meat and medicines. For more details on the anatomy, see the previously noted link.

I'll stop right there for now. If I can find a species with more literature and an eccentric appearance, perhaps I'll write on it too sometime in the near future...


References:

Alibardi, Lorenzo and Toni, Mattia. 2006. Skin structure and cornification proteins in the soft-shelled turtle Trionyx spiniferus. Zoology vol. 109 is. 3 182-195. Available: Here

Bonin, Franck et al. 2006. Turtles of the World. The John Hopkins University Press, Baltimore.

Kitimasak, Wachira et al. 2005. Distribution and Population Status of the Narrow-Headed Softshell Turtle Chitra spp. in Thailand. The Natural History Journal of Chulalongkorn University vol. 5(1): 31-42. Available: Here

Scheyer, Torsten M. et al. 2007. A plywood structure in the shell of fossil and living soft-shelled turtles (Trionychidae) and its evolutionary implications. Organisms Diversity & Evolution vol 7 (2), 136-144. Available: Here

Unexpected Bipedalism

Hopefully this will still work for future readers:

Most people seem quite unaware that pangolins even exist. Apparently, only three specimens are held in captivity legally as of 2005 - so it's really no small mystery why. Despite some bizarre notions that they are dinosaur-like reptiles, these are mammals and are closely related to carnivorans (dogs, cats, seals, etc.) forming the clade Ferae (Beck et al, 2006). These are united with Perissodactyla, Cetartiodactyla, Chiroptera, and Eulipotyphla (some "insectivores") to form the oddly diverse group Laurasiatheria. If you are familiar with Family/Order names of mammals, then this figure from Bininda-Emonds et al 2007 should be of interest:

You may want to click this...

You'll notice that other mammalian groups with tubular snouts that eat ants (Aardvarks - Afrotheria; Anteaters - Xenarthra) are not related but all belong to different super-orders. There was an enigmatic European Eocene species called Eurotamandua which is classified as an anteater on the German wikipedia and a pangolin on the English wikipedia but is currently in an unresolved position. It could be a sister group to sloths and anteaters, a stem Xenarthran (it doesn't posses the titular vertebral structure) or a pholidotan (pangolin) (Hunter & Janis 2006). Despite all the convergences, pangolins/pholidotans have sharp scales made out of agglutinated hairs covering everything but the bottom of the head and body, and the inside of the limbs (Heath, 1992). One of these days I'll probably talk more about the strange morphology of these mammals, but it is locomotion that I am focusing on here.

Pangolins normally roll up as an anti-predator defense (only exposing the sharp scales) but they are also known to curl up and roll down hills to elude predators (Tenaza, 1975). Since the only large predators on the island where that was observed were humans and pythons, perhaps this is an aberrant behavior. Didn't Stephen Jay Gould write an essay wondering why no animals moved around like balls?

As you may have noticed from the video, the large pangolin Smutsia temminckii is, in fact, a facultative biped. While most sources just mention that fact, the video is useful in showing that the tail is held somewhat strait out (not dragging on the ground) and the arms are tucked in - other bipedal mammals are saltatory (kangaroo, sifaka lemur, jerboa, kangaroo rat, springhare) or have a vertical posture (humans, gibbons - sifakas again) so this posture seems to be unique as far as I know. Walking quadrupedally, the large pangolin Smutsia temminckii puts weight on the knuckles of its forefeet and curls its claws inwards like anteaters (Heath 1992). That position normally is associated with clawed animals (chalicotheres, sloths) - so is the bipedal posture an alternate strategy in not wearing down claws, or is there another factor involved? S. temminckii has hips more suited for load bearing than other species (Heath 1992), and bipedalism appears to be a unique behavior for the species. I have not seen any references to bipedalism in S. gigantea, a similarly sized relative also living in Africa. Many other pangolins are arboreal, and I am not certain if any other large species engage in bipedal locomotion. Although not specifying a species, Filler 2007 noted that the LTP (Lumbar Transverse Process) of pangolins have the same homology as the hominiforms, uniquely among mammals. The implications of this have not been discussed to my knowledge. So why am I asking so many questions? As far as I know, the benefits and mechanics of such a posture have yet to be thoroughly analyzed. I know, I'm disappointed too.

Just in case the other video ceases working at some point, here is a backup pangolin video:





I won't just stop with pangolins. Chris Taylor wrote on bipedal postures in a relative of the camel recently, and my next group is somewhere more along those (herbivorous) lines. They were presumed to be relatives of pangolins earlier, but of course are actually quite distant. I'm talking, of course, about Megatheriid ground sloths. Darren didn't mention sloth bipedalism in his ten strange sloth facts post - which worried me immensely - but it does seem to be pretty widespread in the literature. Phew.

Megatheriid sloths having a bipedal posture when feeding shouldn't come as a shock in the context of mammalian diversity, others such as pandas and chalicotheres probably engaged in a similar posture. Also, just about every reconstruction I see of Megatherium puts it reaching up to a tree with its claws in a bipedal sort of posture. However, tracks indicating both bipedal and quadrupedal posture have been found (Casinos 1996) so there's something interesting happening here. The paper goes on to study the limbs and vertebral column of Megatherium sp. (different species were hard to discern) and the forces put on them in hypothetical quadrupedal and bipedal postures. Results for strength indicators were inconclusive as the hindlimb bones were stronger mechanically but the forelimb bones seemed more efficient in a quadrupedal posture. A study of the backbone movements fit well with bipedal mammals, although the bending was noted as being too high. The femur is pretty bizarrely shaped (it is four times wider in the transverse plane than the sagittal one) - this goes against mammalian and Xenarthran tenancies. This does appear to enhance dealing with stress and since such a drastic change in one bone makes little sense in a quadrupedal animal, Casinos concludes that this was a bipedally adapted animal.

Chris Taylor's post showed that an animal can be adapted towards standing bipedally, so its not like this sloth was an exclusive biped. The possibility of claw prints being somehow erased in the bipedal tracks was not raised, but presumably since there were examples of both tracks types they could be easily distinguished. Maybe this sloth was adapted towards standing bipedally while feeding on trees and switched between quadrupedal and bipedal locomotion like...the pangolins in the videos. Even having a living example doesn't always help since apparently we're not sure what advantage this switching would give.

I tried and tried to find a Youtube video of a bipedal sloth but failed. Also, I realized that the title should have specified "in Mammals", but it sounds snazzier this way.


-Cameron


References:

Beck, Robin MD et al. 2006. A higher-level MRP supertree of placental mammals. BMC Evolutionary Biology (6) 93. Available

Bininda-Emonds, Olaf et al. 2007. The delayed rise of present-day mammals. Nature 446, 507-512. Available

Casinos, Adria. 1996. Bipedalism and quadrupedalism in Megatherium: an attempt at biomechanical reconstruction. Lethaia 29 (1), 87-96. Available

Filler, Aaron G. 2007. Homeotic Evolution in the Mammalia: Diversification of Therian Axial Seriation and the Morphological Basis of Human Origins. PLoS ONE. Available (Open Access)

Heath, Martha E. 1992. Manis temminckii. Mammalian Species 415, 1-5. Available

Hunter, John P and Janis, Christine M. 2006. Spiny Norman in the Garden of Eden? Dispersal and early biogeography of Placentalia. J Mammal Evol 13, 89-123. Available

Tenaza, Richard R. 1975. Pangolins Rolling Away from Predation Risks. Journal of Mammalogy p. 257. Available



I can't access the article, but this abstract mentions how large and derived Glyptodonts possibly engaged in "strenuous locomotor activities" bipedally! Darren mentioned this first, of course.

One Year of The Lord Geekington

61 published posts.

That's what I'm measuring my year by. At a rate of a post a week I feel somewhat accomplished. Cutting and pasting things into Word revealed that I have written something like 87,000 words and filled out around 300 pages so far. By either count, this is roughly the length of an average novel. Granted somebody like H. P. Lovecraft could pump out a letter of a similar length in about a week, but given the subjects covered I feel that I've accomplished something. At least one monstrous post took over a dozen hours to illustrate and write, for instance. I feel that I'm being self-congratulatory here, this feels bizarre.



Reflections Upon the Lord Geekington


So how did this all begin anyways?


I remember as a little kid how I'd always ramble on about every science fact I knew to who ever had the tolerance to listen to me. This blog seems to be a direct continuation of that, now that everybody has the capacity to write about everything to everybody else. As you may recall, the first few months of this blog were rather uneven and, well, geeky. I talked about video games, weird paintings, art, forteana, my own personal speculative evolution, and even a bizarre type of, um, -craft. In retrospect, it really doesn't feel all the worthwhile writing to me. Sure art is nice, but there are much finer websites out there covering it. I had reached the realization that with 100 million other bloggers out there (big numbers scare me) I might want to write something more worthwhile. What is worthwhile to me isn't worthwhile to everybody of course, but at least I feel writing about overlooked natural science is a lot more fulfilling. I hope that it is at least an occasionally interesting read to some people occasionally, I'd hate for this just to be some self-centered exercise, or, er, more so. But hey, I don't get paid for this so at least I feel a little altruistic!

From about February on I had shifted more towards science blogging, writing about cephalopods and cryptid amphibians and other things Darren Naish hadn't posted on yet (or ever). Being dangerously under-qualified compared to Dr. Naish, I didn't my blog to just just wind up a Fooling Grandma* (or worse yet, a Deceiving Great-Grandma) of his creation. I think now that there is information, probably far more than enough, to go around for everybody. Since starting to blog Darren has moved to Scienceblogs and some other very fine Zoology/Paleontology based blogs have arisen such as, ooh, say Laelaps and the Catalogue of Organisms. These blogs and others have given me an unprecedented opportunity to learn about science in a way that I would never have been able to do in the past. What a golden age of information we live in.

*Coined by Russell Shepherd, date unknown. Signifies a product made in imitation of an actual franchise (Action Rangers --> Power Rangers). Most kids and adults realize the difference, so apparently these products were making profits solely by fooled grandmas. Deceiving Great-Grandma. Older people also have great difficulty reading white on black and this footnote is likely nigh-unreadable.

It has come to my surprise that not only do people read what I write, but two fellows (Darren and Chris Taylor (Cat. of Org.)) have given me the "thinking blogger" award, much to my astonishment. If I had heard about such a thing at the outset of blogging, the thought of receiving it would never have crossed my mind. Instead of making me feel pretentious (!!??!) it makes me live in fear of betraying this title. And I don't believe I've ever formally thanked Chris yet, well, thanks! As for awarding others...I don't think I carry any sort of authority, so I'll trust other better bloggers to make their decisions.

Here I am writing this post, just to give you all a glimpse of the magic in progress. I'm sitting on the floor, not even in my own room, and hammering away. Oh yes, I cut my hair rarely, usually shaving my head on Maine Day. This is why I don't talk about or show my personal life.

Random Highlights

As if the structure of this post wasn't convoluted enough...


Disappointments.

Judging by my comments, I have had some uninteresting posts here. I've got to hand it to my sister for commenting enough to basically be a co-blogger of sorts. No zero comments for me! My "scientific" racism, dang! I though that was a pretty good topic. Maybe my "Proto-Europoid" mug scared everybody off. My post on pseudopapers was also just, blah, not needed. There are others, but a cursory glance should give them away.

I'm often rather self-critical, so that coupled with feedback (or lack thereof) will hopefully drive me to improving this blog. I have the drive to improve things, although recently the motivation to do much is more difficult to come by (severe money related troubles, yeesh).


Successes - or at least better posts.

Despite my oft-critical perspective, I'm surprised by how popular some posts were. Anything dealing with large animals (here and here) were surprisingly popular. They were a topical overload and kinda jumpy, but hey, they were pretty fun. As for my favorite posts, I'd say that they were the Omnivore vs. Hypercarnivore post, the choristodere post, and the Meganthropus post - the one that launched me into using peer-reviewed articles. The super-long and semi-technical posts were my favorites, but unfortunately they have to be rare due to the time involved. Sigh...

And now for highlights in picture form:

Choristoderes!

Me and some rather large catfish.

My interpretation of three bigfoot "types" according to Hall/Coleman/Huyghe.

Some very large squids. Hmm, no 108 footers as far as I can tell...

A fictional temnospondyl from a quasi-abandoned project.

That ever-strange cetacean centipede.

The amazing blanket octopus. Taken by Marcello Conticelli off Ponza, Italy.

The obscure Barra carcass, one very strangely decomposed whale.

And I course, I give my thanks to everybody that I have failed to mention in this post. And if you find this slightly interesting, please visit the links to the right.


Let's hope I can write another one of these

-Cameron

Swimming Opossums

Let's start off with a mystery:

In a 1999 field report by Angel Moran Forés (readable: here) he claimed to have found and photographed a strange aquatic animal in Macas, Ecuador. He said it had white fur with brownish spots, was 35-40 cm long with no tail, had webbed fore and hind-feet, no pouch, and a proboscis. The specimen was never sold, so all we have to go on is a photograph and that description:

"Mystery Animal" photograph by Angel Morant Forés.

And now to make things interesting, here is a photograph of a Water Opossum or Yapok:

Taken from Wikipedia

While living yapoks seem to have much darker fur (see here) for some reason either preservation makes the fur lighter or there is a light colored morph. Either way, both specimens have the same striking bodily coloration pattern (down to the barely visible dorsal stripe), which Forés did not mention. The size would be a little large, unless the legs were counted; but the main problem is with the weird anatomical features. Yapoks do have pouches (rear-opening, so maybe it was missed?) and tails and also lack webbed fore-feet and a proboscis. I for one can't see a proboscis in that picture, but I'll take the author's word for it. While new species are being discovered at a fairly impressive rate in this region of the world, I think this is more likely a poor case of taxidermy than anything. Of course with many things of a cryptozoological nature, this one doesn't appear to be wholly resolvable any time soon.

Aquatic adaptations in marsupials appear to be quite unusual. There don't seem to be any species of mammals that can't swim to some degree (except giraffes), but marsupials seem conspicuously unable to adapt to a semi-or fully aquatic niche. Apparently the logistics of keeping the young alive in a pouch while diving kept the marsupials from adapting in that direction. That is, except the yapok (Chironectes minimus) is the only species of marsupial to be adapted towards this lifestyle (Fish, 1993). I'll get into its tricks later.

Even less widely known than the yapok is the thick-tailed opossum (Lutreolina crassicaudata), also said to be quite competent in the water. It is the most carnivorous of all didelphids and is frequently compared to a mustelid ("mink-opossum") in appearance (Santori et al, 2005). The scientific name "Lutreolina" hints at an otter-like and thus semi-aquatic lifestyle as well. So is this an overlooked semi-aquatic marsupial?

The "lutrine opossum". Taken from this page. According to Walker's Mammals of the World this image (flipped) was taken from the New York Zoological Park through Joseph Davis.

A 2005 paper by Santori et al on the locomotion of the thick tailed opossum reveals that yes, there are some people who have considered this species semi-aquatic in the past. Didelphids as a group are apparently good swimmers, so the authors of the paper compared terrestrial species and the yapok to this species by using videotape. The climbing, jumping, and running capabilities of this species was also compared to the other opossums. L. crassicaudata actually does have some adaptations towards an aquatic lifestyle (buoyancy control, posture), and a unique gait separate from terrestrial opossums and the yapok, but curiously is not faster in the water than terrestrial opossums. It also lacks other adaptations such as webbed feet and the use of only the hind limbs (though some other semi-aquatic animals also use all their limbs). So while possessing some aquatic adaptations, the thick-tailed opossum is not even considered semi-aquatic. Apparently there isn't a term to reflect this semi-semi-aquatic condition. Perhaps a mustelid-like body plan has the side-effect of being able to travel in water slightly more efficiently than most terrestrial mammals.


So now on to (or rather, back to) the real McCormick, the yapok. Unlike lots of other didelphids, the yapok actually does have a pouch and a very unusual one at that. The pouch opens to the rear and has a powerful sphincter muscle able to keep water out, but maybe not necessarily airtight (somehow...) (Marshall, 1978). The young in the pouch are able to suspend breathing for a few minutes and tolerate low oxygen levels. Very oddly, there are some claims that opossums of the genus Didelphis (the Virginia opossum and kin) can also swim with young in the pouch, although how they were able to manage that has not been explained (Marshall, '78). The colossal Voss & Jansa 2003 phylogenetic study closely links the yapok and thick-tailed opossum with the genus Didelphis (plus Philander and Metachirus), so maybe a semi-aquatic or semi-semi-aquatic ancestor existed. Or maybe not. Regardless, the same authority with the unexpected fact concluded that maintaining the young in the pouch limits how far the marsupials can adapt to a semi-aquatic lifestyle. The fact that opossums managed it but Australian marsupials haven't (as far as I know) is remarkable enough as it is.

Marshall '78 has some other weird facts about the yapok worth mentioning. Despite being semi-aquatic, the species is still able to climb and uses its tail in a prehensile manner (the thick-tailed opossum can't, interestingly) and it is also capable of collecting nesting materials. These animals are also largely carnivorous and they are believed to use their un-webbed forepaws in the same manner as a raccoon. Despite apparently being considered nocturnal, the circadian rhythms of this animal are not apparent and it can be active day or night. The females somehow manage to have four to five teats...didelphids seem to have a tenancy towards an odd number of teats for some reason.

And there is a whole paper on just how weird the genitalia of the males are (Nogueiraet al. 2004). The males posses a rudimentary pouch which it protects its scrotum in only while moving quickly or moving in water. Unlike other didelphids, they also lack a cloaca. Weird, weird stuff.



It looks like another wretchedly busy week, so who knows when and what I'll write about.

-Cameron

References:

Fish, Frank E. 1993. Comparison of Swimming Kinematics between Terrestrial and Semiaquatic Opossums. Journal of Mammalogy 74 (2), 275-284. Available: Here

Marshall, Larry G. 1978. Chironectes minimus. Mammalian Species. 109, 1-6. Available: Here

Nogueira, Jose Carlos et al. 2004. Morphology of the male genital system of Chironectes minimus and comparison to other didelphid marsupials. Journal of Mammalogy 85 (5), 834-841. Available: Here

Santori, Ricardo Tadeu et al. 2005. Locomotion in Aquatic, Terrestrial, and Arboreal habitat of thick-tailed-opossum, Lutreolina crassicaudata (Desmarest, 1804). Journal of Mammalogy 86 (5), 902-908. Available: Here

Voss, Robert S. and Jansa, Sharon A. 2003. Phylogenetic studies on Didelphid Marsupials II. Nonmolecular data and new IRBP sequences: Separate and combined analyses of didelphine relationships with a denser taxon sampling. Bulletin of the American Museum of Natural History. 276, 1-82. Available: Here

Marsupial "Primates"

Dear Constant Readers,

Living in the United States creates the impression that the Virginia Opossum (Didelphis virginiana) is some sort of interloper from marsupial-infested Australia. Opossums are members of the family Didelphidae and order Didelphimorphia which include at least 60 species (numbers vary between sources). Didelphids are currently restricted to South and North America but in the past ranged to Africa, Asia, Europe, and Antarctica - the latter implying that they might have made it to Australia (there is no fossil proof of this to my knowledge). Phylogenetically they are placed at the very base of the marsupial supertree according to Cardillo et al 2004; most closely related are the 6-7 species of New World "shrew opossums" of the family Caenolestidae (Order: Paucituberculata). It goes without saying that the "possums" (Suborder Phalangeriformes) of Australasia are not directly related. Interestingly there is a third order of marsupials (Microbiotheria) from the New World that is grouped within the Australasian marsupials - a rather amazing phylogenetic situation. So with scores of species and 3 of 7 orders, the New World isn't a very place for marsupials after all.

Rather than continue with an overview of the order, I am going to focus on one group in particular, the woolly opossums. The subfamily Caluromyinae (Glironia, Caluromysiops, Caluromys) is shown as being basal in the didelphid family tree; typically it would be called "primitive" but this is misleading. Remarkably, as the title suggests, this group show convergences upon the primates. As noted by this journal which I unfortunately cannot access, the genus Caluromys shows features such as a large brain and eyes, small litters and slow development, and agile locomotion. Rather unexpected from a relative of the fairly humble Virginia opossum! Science has progressed from the days of large brained animals being more "advanced" or "better" than ones that are not - there are reasons for animals not all "aspiring" to be anthropomorphic. With that out of the way, the question is, why do these marsupials resemble primates?

The woolly opossum Caluromys derbianus. Photo taken from this page and credit is due to Maya Nature by Thor Johnson. Note the resemblance to a prosimian such as, say, a mouse lemur.

Lemelin et al 2003 note that didelphids prefer a wide variety of habitats and the genus Caluromys spends most of its time in the canopy on thin branches. The hands and feet of this genus have longer toes and the hind limbs show a much more prominent big toe. The study in the paper demonstrated that while most mammals use a lateral sequence for walking (Right hand, RF, LH, LF) most primates use a diagonal sequence (RH, LF, LH, RF) while in arboreal settings. The paper supports the theory that an arboreal habitat in early primates shaped the gait and specializations such as the hindfeet by showing that woolly opossums display the same traits.

Aside from the resemblance to what an early primate may have looked like, members of the family Caluromyidae are interesting in their own right. Oh wait, did I say family? Sources disagree if all modern opossums are all members of the same family or not; the diversity of opossums (extinct or otherwise) in one family does seem rather high but I haven't heard anything definitive. I'll just vaguely refer to them as caluromyids or woolly opossums to sidestep this issue. Walker's Mammals of the World sets the genus apart from other didelphids by noting characters such as partially derived ankle features, the retention of a cloaca, an ossified bony palate, and inner ear structure. Interestingly, this group of opossums are distinguished for having retained a pouch whereas the 50+ species of the (Paraphyletic? Polyphyletic?) marmosid group lack one. A marsupial without a pouch, hmm.

Glironia venusta, the "bushy-tailed opossum". Illustration taken from here. I'm not sure what language that is in... (Edit: Apparently Maltese)

Anyways, generally placed with the caluromyids (Cardillo et al 2004) or sometimes in its own family (Nowak, 1999) is the species Glironia venusta. It is similar to a genus of the aforementioned pouchless opossums (Marmosa) and is believed to be largely arboreal. There was a report mentioned in Walker's of this species leaping from vine to vine and apparently hunting insects - behavior not known with any other opossum species. Interesting though this species sounds, there have only been 9 specimens documented so information is a tad scarce.

Caluromysiops irrupta is another rare genus of caluromyid, apparently quite closely related to Caluromys. The species inhabits humid forests and is believed to arboreal and nocturnal; it feeds on nectar and probably has a comparable omnivorous diet to Caluromys. The familiar Virginia Opossum rarely exceeds a 3 year lifespan (record of 5) but this species, rarely kept in captivity, has a current record of 7 years and 10 months. But again, information on this species is lacking.

Caluromys laniger. Taken from this page (in Italian). One of the few pictures no explicitly copyrighted and it demonstrates arboreal movement to boot!

The genus Caluromys is of course the best known of the group, there are well over a dozen journal articles that I casually found on this genus alone. The species has been kept in labs and there are articles on hormone levels and nitrogen requirements for this genus, for instance. A pretty definitive article can probably be written on this genus but that is of course outside of the scope of this post, I only have so much time here. I will still try and concentrate on the big picture here though. This genus also drinks nectar from flowers and is believed to be a pollinator (Gribel, 1988) however it is known to eat other plant and animal material (Bucher and Hoffmann 1980). Caluromys species also has a long lifespan (6 years 4 months is the record) a small litter size (2-4 average) for an opossum and a near-exclusive arboreal habitat (Nowak, 1999). Could those also be viewed as convergences with the primates? C. philander and C. lanatus are fairly common and listed as near threatened by the IUCN Red List while C. derbianus is a vulnerable species. Glironia and Caluromysiops are listed as vulnerable as well (I'm surprised Glironia isn't data deficient).


I knew I could write a post on terrestrial animals! It wasn't much of a challenge really, like most of my post it has been floating around in my head for a few months. Sigh. Things are about to get very busy again, so who knows what I'll post next. A speculative post on opossum-men? Nah.

-Cameron


References:

Bucher, John E. and Hoffmann, Robert S. 1980. Caluromys derbianus. Mammalian Species 140, 1-4. Available: Here

Cardillo, Marcel et al. 2004. A species-level phylogenetic supertree of marsupials. J. Zool., Lond. 246, 11-31. Available: Here

Gribel, Rogerio. 1988. Visits of Caluromys lanatus (Didelphidae) to Flowers of Pseudobombax tomentosum (Bombacaceae): A Probable Case of Pollination by Marsupials in Central Brazil. Biotropica 20, 344-347. Available: Here

Lemelin, Pierre et al. 2003. Footfall patterns and interlimb co-ordination in opossums (Family Didelphidae): evidence for the evolution of diagonal-sequence walking gaits in primates. J. Zool., Lond. 260, 423-429. Available: Here

Marshall, Larry G. 1978. Glironia venusta. Mammalian Species 107, 1-3. Available: Here

Nowak, Ronald M. 1999. Walker's Mammals of the World, 6th edition. Johns Hopkins University Press

The Many-Finned Brochoadmones

Dear Constant Readers,

There are a few fish out there with an unusual number of dorsal fins; bichirs and reedfish are basal Actinopterygians with a profusion of dorsal fins; some members of the family Scombridae (derived Actinopterygians) such as tuna and mackerel possess dorsal and anal "finlets". Nauen and Lauder 2001 note that during a stroke, finlets (with very similar morphology) showed a considerable difference in bending and appear to direct water flow and increase thrust. This abstract of a recent paper I couldn't access notes that finlets do not significantly reduce drag and enhance thrust in normal swimming. It is possible (the authors note) what difference they did cause either was meaningful over long periods of time or more useful at high speed. I haven't seen any discussion on what the mechanics of the many dorsal fins on a bichir are; since their lifestyle is pretty different from the super-performing scombrids I'm guessing they're not homologues. I've noticed that sturgeon have pre-dorsal scutes, but they may not play a role in swimming.

The butterfly kingfish (Gasterochisma melampus) showing dorsal and anal finlets. A public domain image from Fishbase by Robbie N. Cada.

A nice and old (therefore public domain) image of the bichir, Polypterurs bichir

These fish are, of course, not the focus of this particular blog post. They do illustrate that fish mechanics, particularly dealing with unconventional fin setups, are not as well understood as I anticipated. What then of a weird and obscure species from a weird and extinct group? Acanthodians, or "spiny sharks" are a radiation of jawed fishes distinct from the placoderms, chondrichthyans (sharks, skates/rays, chimeras), and bony fish. Acanthodians don't seem to have very much written on them at all; they're more closely related to bony fish than other groups (they're both Teleostomians), but their scales are more similar to those of chondrichthyans; and same species have ventral projections ("spines") appearing like multiple fins. All other fish have 2 paired fins, but some Acanthodians had many more (up to 6 spine pairs). While belonging to a unique group within Acanthodii, the recently re-described Brochoadmones sheds a lot of light on their bizarre anatomy.

Brochoadmones was a Devonian (430-435 mya) fish described all the way back in 1977. It had been demoted to a known Acanthodian family in '79 was put in its own sub-order in 1996 based on more evidence. As illustrated in Hanke & Wilson 2006, the reconstruction changed from a generalized fish with multiple finlets in 1977 to a humped salmon-like fish with shark-like gills. With two beautifully preserved fossils in the "Wonder Block" this fish is now almost completely know, and boy is it strange looking:

There was a photograph also used by Fish Feet, but at some point of time I'm going to make my own illustration based on the fossil. Note the shark-like gill slits and a pronounced pectoral fin. That last one is important...

The overall body shape of Brochoadmones is somewhat reminiscent of knifefish, the panther grouper, and a couple cichlids. These fish are stealthy ambush predators approach prey head-on facing downwards and capture them with a short lunge. Fish were visible inside some specimens, leaving no doubt that these were also piscivores. The authors speculate that if the pre-pelvic fins could move, then perhaps they aided subtly aided in stealth. Although not mentioned directly by the authors, I suppose it is implied that the multiple fins are analogues to the elongated anal fin of the knifefish and perhaps grouper. However, the authors note that other acanthodians were built for continuous swimming and some of them also have the pre-pelvic fins as well. Did pre-pelvic fins offer any advantage over the setup of modern fish groups? Over continuous fins in some instances? Why these fins were only present in this one group is apparently not clear and will likely remain so since the peculiar (non-analogous) multiple fins of scombrids and bichirs also have no clear function.

Brochoadmones had many features aside from the number of pelvic projections that made it unique and quite interesting. The projections themselves consist of six pairs of pre-pelvic spines and a web of skin with scales covering both sides. According to the authors, that feature has not been seen in any other vertebrate and look like expectations of what a fin evolving from a lateral fin-fold would look like. The largest spine is larger than that of the actual pelvic fin spine, although the attached fin of the latter is larger in area. Also noteworthy is that the pre-pelvic spines continue quite a ways closer to the head than the pectoral fin. There have been suggestions that both types of fins evolved from an ancestral lateral fin-fold, but the authors suggest that the radically different placement and development of the fins suggest different origins (both predating jaws). So there you have it, a peculiar and obscure fish that somehow has implications for the origins of limbs. The fusion of the anal and caudal fin (along with paddlefish development) suggest that the median fins actually do develop from an ancestral median dorsal/caudal/anal fin.

Other strange features hold implications for Acanthodian phylogenetics, but I'd say that is out of the focus of this current blog post. I want to be able to blog and still do homework, dangit. Recently it seems that I have been focusing quite a bit on aquatic creatures so I think next post it is time for me to branch out a little. Well, I really don't plan these out in advance, so I suppose the next thing that strikes my fancy will come up.


-Cameron

References:

Nauen, Jennifer C. & Lauder, George V. 2001. Three Dimensional Analysis of Finlet Kinematics in the Chub Mackerel (Scomber japonicus). Biol. Bull. 200, 9-19. Available: Here

Hanke, Gavin F. & Wilson, Mark V. H.. 2006. Anatomy of the early Devonian Acanthodian Brochoadmones milesi based on nearly complete body fossils, with comments on the evolution and development of paired fins. Journal of Vertebrate Paleontology 26 (3) 526-537. Available: Here




Tangent:


Should I even mention this thing? Brochoadmones also had pre-pelvic appendages extending anterior to the distinct pectoral fins as well as two dorsal fins and a somewhat humped profile. I'm not suggesting that there are giant whale-like acanthodians out there; but perhaps this bizarre Renaissance drawing was done with an Acanthodian in mind (like griffins from Protoceratops). The modern reports may have been influenced by this myth and illustration, but the sightings primarily seem to be of cetacean pods with a dash of polychaete thrown in.