Eocetus, "Eocetus", and Friends

Update (January 28, 2014): "Eocetus" wardii is now Basilotritus wardii. More on my new post, The Third King.


I was shocked that Uhen (2010) remarked that Basilosaurus drazindai and Basiloterus hussaini "probably represent protocetids... akin to Eocetus". This would place the whales outside Pelagiceti and imply that the now-questionable basilosaurids were potentially capable of walking on land, despite being enormous. Unfortunately, other mentions of this revised placement give no further details (Uhen 2008, Uhen et al. 2011) and Uhen (2010) further states the placement is "difficult to determine with certainty" due to scarce materials. I suspect the hypothesis will not be officially discussed until further material is found and/or described... which won't stop me from wildly speculating.

Lumbar vertebrae in right lateral view. From left to right: "Eocetus" wardii (from Uhen 1999), Basiloterus hussaini, and Basilosaurus drazindai - note that the latter-most may be an anterior caudal (from Gingerich et al. 1997). For comparison: Basilosaurus isis vertebrae.

In the description of Basilosaurus drazindai, Gingerich et al. (1997) note a number of "primitive retentions" which resemble the morphology of "generalized archaeocetes": long neural spine and arch; broad, almost-horizontally placed, anterior-projecting metapophyses which project beyond the anterior edge of the vertebral centrum; and paired, posterolateral processes of the neural arch. Aside from the last trait (which I can't confirm without a dorsal view), all of these traits are present in "Eocetus" (Uhen 1999). Additionally, "Eocetus" has elongated transverse processes, unlike the condition of Basilosaurus (Uhen 1999); however, B. drazindai has processes with a 15.5 cm long base (they broke off) relative to the 30 cm centrum (Gingerich et al. 1997), and so probably had a similar, albeit slightly less extreme, condition. The only criterion for placing B. drazindai in the genus Basilosaurus was the size and shape of the centrum (Gingerich et al. 1997), and while they are uncannily similar in shape, everything else seems to be pointing towards a relationship with "Eocetus".

Lumbar vertebrae in anterior view. Ditto order.

As for awkward middle-child Basiloterus, it appears to have a centrum which is slightly more elongated than that of "Eocetus", however the neural arch and maybe the neural spine appear to be narrower. The metapophyses are upwardly-angled (Gingerich et al. 1997), less broad, less anterior-projecting, but still appear to extend past the centrum. The posterolateral processes are absent (Gingerich et al. 1997). The base of the transverse process is 9.3 cm long relative to a 19.5-20 cm centra (Gingerich et al. 1997), proportionally similar to Basilosaurus drazindai. The placement of Basiloterus is thus not clear, and perhaps it was a basilosaurid or an even more derived protocetid.

Maiacetus inuus, a basal "protocetid" (Uhen 2011). From Wikipedia Commons.

Protocetidae is a blatantly paraphyletic "family" of extinct cetaceans from Eocene coastal marine deposits with hip and femur morphology indicating amphibious capabilities (most of the time) and no evidence of flukes (Uhen 2010). Uhen (1999) appears to think that "Eocetus" wardii had weight-bearing hips, however Uhen (2010) refers to them as "moderately reduced" and regarded the species as possibly non-amphibious. This is perhaps not surprising since Eocetus, "Eocetus", and an unnamed Pisco Formation species are the sister group of Pelagiceti (Uhen et al. 2011). This could make them closer relatives of Dorudon than Maiacetus, and raises the question of how many typical protocetid traits they actually exhibited. Perhaps they were entirely aquatic tail-based swimmers which just happened to have fairly large vestigial legs.

Dorudon atrox. From Wikipedia Commons.

The scare quotes around "Eocetus" hint at a taxonomic misadventure. "E." wardii was assigned to its genus by Uhen (1999) based on comparisons of its skull and vertebrae to Eocetus schweinfurthi; the problem is, the holotype of E. schweinfurthi is an isolated skull and it is not possible to determine whether the vertebrae referred to it actually represent the species (Geisler et al. 2005). There is overlapping skull material (Uhen 1999), but Geisler et al. (2005) apparently regarded it as too incomplete to warrant unambiguous placement in the genus. Somehow, "Eocetus" and Eocetus formed a clade in phylogenetic analyses (Geisler et al. 2005, Uhen et al. 2011), making it probable that future discoveries will confirm their close relationship.

"Eocetus" wardii is clearly related to unnamed Pisco Formation material which exhibits the same distinctive traits (moderate centrum elongation, elongated neural arches and spines and transverse processes, strange pock-marked texture) with the only difference being that the unnamed material is 35% smaller (Uhen et al. 2011). The Egyptian vertebrae dubiously assigned to Eocetus schweinfurthi (figured in Uhen 1999) also seem quite similar (including the pock-marks), and if it is also a member of this clade, it would indicate a sizable trans-oceanic range. This in turn could be taken as evidence of the whales being largely pelagic... of course this is quite speculative.

There of course remains much to be known about these cetaceans, and perhaps future discoveries will be enlightening as to how similar they were to the pelagic cetaceans, as well as the origins of Pelagiceti. I really hope it turns out that a Basilosaurus-sized animal could walk on land.


References:

Geisler, J. H., Sanders, A. E., and Luo, Z-X. (2005). A New Protocetid Whale (Cetacea: Archaeoceti) from the Late Middle Eocene of South Carolina. American Museum Novitates 3480, 1-65. Available.

Gingerich, P. D., Arif, M., Bhatti, M. A., Anwar, M., & Sanders, W. J. (1997). Basilosaurus drazindai and Basiloterus hussaini, new Archaeoceti (Mammalia, Cetacea) from the middle Eocene Drazinda Formation, with a revised interpretation of ages of whale-bearing strata in the Kirthar Group of the Sulaiman Range, Punjab (Pakistan). Contributions from the Museum of Paleontology, University of Michigan 30 (2), 55-81. Available.

Uhen, M. D., Pyenson, N. D., Devries, T. J., Urbina, M., and Renne, P. R. (2011). New middle Eocene whales from the Pisco Basin of Peru. Journal of Paleontology 85(5), 955-969. doi: http://dx.doi.org/10.1666/10-162.1

Uhen, M. D. (2010). The Origin(s) of Whales. Annual Review of Earth and Planetary Sciences 38, 189–221. Available.

Uhen, M. D. (2008). Basilosaurids. In: Perrin, W. F., Würsig, B., and Thewissen, J. G. M. (eds.) Encyclopedia of Marine Mammals, Second Edition. Elsevier: Burlington, Massachusetts. Available.

Uhen, M. D. (1999). New Species of Protocetid Archaeocete Whale, Eocetus wardii (Mammalia: Cetacea) from the Middle Eocene of North Carolina. Journal of Paleontology 73(3), 512-528.

Weems, R. E., Edwards, L. E., Osborne, J. E., and Alford, A. A. (2011). An occurrence of the protocetid whale "Eocetus" wardii in the Middle Eocene formation of Virginia. Journal of Paleontology 85(2), 271-278. Available.

The Giant Turtle Therizinosaurus

Therizinosaurus, you look... unwell. Reconstruction by K. K. Fierova, from Maleyev (1954).

I am quite fond of old, weird reconstructions, and the initial classification of Therizinosaurus cheloniformis as a "turtle-like reptile"¹ resulted in the magnificent specimen above. So how could the veritable Jabberwocky we're all familiar with be misinterpreted to such a colossal degree?

¹ This odd phrasing is mirrored in the scientific name ("saurus" = lizard, "cheloniformis" = turtle-like). Malayev (1954) linked Therizinosaurus with members of Protostegidae and thus (probably) didn't intend to suggest another clade of reptiles which converged on turtles. Bizarrely, Rozhdestvensky (1974) claimed Malayev/Maleev classified Therizinosaurus as a "turtle-like pangolin"! Rozhdestvensky (1977) does not reiterate that statement, and further notes that another worker (Sukhanov) classified Therizinosaurus as a turtle; I unfortunately cannot find that source ("The subclass Testudinata" in Osnovy Paleontologii).

Therizinosaurus in its non-turtle form. From Wikipedia Commons.

Malayev (1954) described Therizinosaurus from scrappy remains: a metacarpal fragment, 3 manual unguals, and rib fragments (Zanno 2010). One of the ribs was an estimated 1.5 meters long when complete and was used to calculate a maximum body width of 3.25 meters (10'8") and body length of 4.5 m (14'9") (Malayev 1954); this is of course quite a bit larger than even the largest known Stupendemys geographicus. The rib was noted to lack costal elements, which is curious since turtle skeletons generally look like this:

 

Common Snapping Turtle (Chelydra serpentina) skeleton. Note the plastron is missing. From Wikipedia Commons.

Surprisingly, this is not necessarily a critical flaw, as (all?) turtles have distinct ribs during development before the carapace is fully formed (Wyneken 2001, fig. 90; Sánchez-Villagra 2009, figs. 3, 4). Malayev (1954) did not mention this nor the obvious possibility of a multi-ton hatchling. Instead, the "form of the ribs" was compared to Archelon and Protostega:

Archelon skeleton. From Wikipedia Commons.

The similarity is very general and Malayev (1954) does not list any specific shared characteristics. Due to the lack of costal elements, Malayev (1954) speculated that Therizinosaurus was in a distinct clade and in life had "barely developed or almost completely absent bony armor". It is incredibly strange that the Leatherback Seaturtle (Dermochelys coriacea) was not mentioned, as it entirely lacks costal elements and instead has thousands of dermal ossicles (Cebra-Thomas et al. 2005). The skeleton (sans ossicles) looks like an attempt by turtles to become "normal" tetrapods again.. until you notice the pectoral girdle within the ribcage:

From Wikipedia Commons

The rib material used to describe Therizinosaurus cheloniformis is apparently not from a therizinosaur at all, but a sauropodomorph (Zanno 2010 citing Rozhdestvensky 1970). Isn't it a major problem that the holotype is a chimera? Whatever the case, Therizinosaurus cheloniformis has been re-described a few more times and other rib material has been referred to the species (Zanno 2010). However, all of the diagnostic traits (and most of the material) are from the forelimbs (Zanno 2010).

From Wikipedia Commons.

Malayev (1954) interpreted the metacarpal and phalanges to be "powerful swimming organs" and suggested the huge claws were used for "cutting aquatic vegetation or for another functions, constrained by movement and acquiring food". The longest phalanyx was 60-65 cm long, not including the keratin covering (Malayev 1954), which suggests that the claws were ridiculously huge in life, even for a turtle-like reptile with a 4.5 meter body. I have observed turtles using their claws to climb and tear apart food (maybe what Malayev had in mind...), but clearly claws this disproportionate were doing something special. Something like this:

I like to think that Therizinosaurus, despite not being turtle-shaped anymore, waved its giant claws seductively in the faces of prospective mates.

References:

Cebra-Thomas, J., Tan, F., Sistla, S., Estes, E., Bender, G., Kim, C., Riccio, P., and Gilbert S. F. (2005). How the Turtle Forms its Shell: A Paracrine Hypothesis of Carapace Formation. Journal of Experimental Zoology 304B, 558-569. Available.

Maleyev, E. A. (1954). A new turtle-like reptile from Mongolia. Priroda 3, 106-108. Available.

Rozhdestvensky, A. K. (1977). The study of Dinosaurs in Asia. Journal of the Palaeontological Society of India 20, 102-119. Available.

Rozhdestvensky, A. K. (1974). History of the dinosaur fauna of Asia and other continents and questions concerning paleogeography. Transactions of the Joint Soviet–Mongolia Paleontological Expedition 1, 107–131. Available.

Rozhdestvensky, A. K. (1970). On the gigantic claws of mysterious Mesozoic reptiles. Palaeontological Journal 1, 131-141.

Sánchez-Villagra, M. R., Müller, H., Sheil, C. A., Scheyer, T. M., Nagashima, H., and Kuratani, S. (2009).  Skeletal Development in the Chinese Soft-Shelled Turtle Pelodiscus sinensis (Testudines: Trionychidae). Journal of Morphology 270, 1381-1399. Available.

Wyneken, J. (2001). The Anatomy of Sea Turtles. U.S. Dept Commerce NOAA Tech Mem NMFS SEFSC-470. Available.

Zanno, L. E. (2010). A taxonomic and phylogenetic re-evaluation of Therizinosauria (Dinosauria: Maniraptora). Journal of Systematic Palaeontology 8(4), 503-543. Draft Available.

A Giant Snapper At Last!

A common cliché in fringe anecdotes is that when eyewitnesses see something beyond belief, the camera has the lens cap on/no film/failed to work/been misplaced. Logically this should be taken as a strike against veracity... but I began to wonder otherwise when it happened to me. 

Of course, I've documented a big snapping turtle before, but my subsequent failures were astounding. I saw the turtles on multiple occasions this year (alluded to here), sometimes up close (touching, in fact) and once in triplicate. On all of these occasions I didn't bring my camera because I was commuting via bike, or the turtles fled before I could get their photographs. After a couple dozen failures, I gave up. Impulsively I decided on 8 November 2011 to take a trip searching for any reptiles or amphibians still active in the abnormally warm weather (about 70° F, 21° C) and saw this (plus a frog):

Blobturtle! I saw the turtle fairly clearly, but evidently my camera didn't. Rather than leave and be disappointed for a few months and then fail to see the turtles ever again, I realized I had no other option but to go in after it. Not only was the water very cold (it had snowed earlier in the year), it was murky and muddy and possibly had other snapping turtles I couldn't see. Gradually and with little subtlety, I made my way over to the turtle which had of course noticed me, but did not attempt to escape.

Remembering previous encounters and advice on pick-pocketing from Fagin, I approached the turtle from the rear, knowing it would eventually rotate around to defend itself. I also kept in mind how to fight the Cyberdemon from Doom - it's not just the shooting, it's the circle-strafing. With the cold water being slightly less of a hindrance for me, I managed to avoid something getting amputated. 

Getting closer, I confirmed my suspicions that, yes, this turtle is really really big.

The closest thing I could get to a measurement.

Eventually the turtle kicked up large amounts of silt and released gas (from... somewhere) and became impossible to see. I "ran" off, knowing that my luck in succeeding with this ill-conceived shenanigan was running out.

I know I'm never going to get an accurate length or weight measurement from this turtle... not without one or both of us getting hurt. Even if this specimen was a record (and there's no guarantee), it would not be worth risking the life of an old reptile to revise the SCLmax of 49.4 cm for Chelydra serpentina. From now on I'm leaving these turtles alone, my curiosity is satiated, and bothering them further will have no benefits. I'll have to live with the wonder that despite inhabiting a polluted body of water and having human hunt them and compete for their resources, things like this still exist.

Picture of the Indiscriminate Interval #000005a - The Bulldog-Turtle

No time for a proper write-up, so here's a mysterious teaser. Can anyone identify the mystery skull?

Of the Monstrous Pictures of Whales

"But it may be fancied, that from the naked skeleton of the stranded whale, accurate hints may be derived touching his true form. Not at all. For it is one of the more curious things about this Leviathan, that his skeleton gives very little idea of his general shape"

- Herman Melville. Moby-Dick; or, The Whale. Chapter 55.

Suspiciously similar to a photo taken by Markus Bühler.

What would be made of cetaceans if they were known only from fossil bones? The reconstruction above shows how a mildly unusual Sperm Whale (Physeter macrocephalus) may appear in this hypothetical alternate reality. The unfortunate cetacean is subjected to almost unadulterated 'shrink-wrapping', with the exception of the 'forehead' region. This area of the skull has a strongly concave surface which would look highly implausible on an aquatic creature. What the angle of the reconstruction fails to show is that the concavity is part of a basin-like depression which covers most of the Sperm Whale's cranium; coupled with crests for the attachment of the maxillonasalis muscle, it should be clear that vast amounts of soft tissue were present. The soft tissue is so considerable in mass that Clarke (1978) referred to the head of a Sperm Whale as "largely snout and the crest of the skull necessary to support it". 

A huge nose can be inferred from a Sperm Whale skeleton, yet Melville's assertion is still likely correct. A sloping, prow-like snout would probably be viewed as most likely due to the shape of the skull and hydrodynamic concerns. It seems unlikely, if not impossible, for internal structures such as the spermaceti organ, junk, museau de singe, and distal sac to be inferred; the first two have a major influence on external appearance, as demonstrated by Carrier et al. (2002). Who knows what functional morphology would be hypothesized without knowledge of the complex inner anatomy of the snout, but with knowledge of the strong asymmetry, lack of functional teeth, and a big lump of tissue that must be doing something other than fill out a basin-shaped skull. 

Thanks to cryptozoology, hypothetical alternate realities are not needed for cetacean remains to be grossly misinterpreted. I really couldn't ask for a better springboard for showing off the ludicrous contrast between the skeleton and life appearance in cetaceans.

Above is an extremely literal reconstruction of the 'hairy' Russian 'plesiosaur' carcass. The position of the nostrils is unambiguously cetaceous, but surely the head is too crocodilian and the body too serpentine for this to be a known species? Nah, the skeletal morphology is unambiguously identical to that of a Beluga whale (Delphinapterus leucas). Who knew that beneath all that blubber and muscle, Belugas were reptilian monsters?

Delphinapterus leucas skeleton from Wikipedia Commons.

Beluga, from Flickr user Travis S.

What I find particularly striking is how much of this cetacean's mass lies outside of the ribcage, and that the ribcage appears to have very little 'influence' on the overall shape of the animal.

Delphinapterus leucas head 3 - taken and modified from Wikipedia Commons.

It seems that a few suggestions of the underlying skull can be seen on the live Beluga's head, but it still seems amazing that the two have anything to do with one another.

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In 1996, a 'dragon' skeleton was pulled out of the ocean in Langkawi, Malaysia. The only available photo is unfortunately tiny, but the shape of the skull as well as the shape and number of the teeth make an Orca (Orcinus orca) identity probable. That, and it was identified as such.

Based on this.

The situation is essentially the same as that of the Beluga, but with a scarier and vaguely crocodilian head. I think that this shows that, underneath that adorable layer of blubber and high-contrast markings, Orcas are capable of serious macropredation.

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The Ataka carcass - Worst 'Mystery' Ever.

Something like 6-7 years back in Rhode Island, a local news station ran a brief blurb on a carcass similar in condition to the Ataka specimen being unceremoniously disposed of. It was identified as a Humpback Whale (Megaptera novaeangliae) and nobody appeared to have given it a second thought. The Ataka carcass itself is similarly a complete non-mystery - it was unambiguously identified as a Bryde's Whale shortly after washing up. Even Heuvelmans' great tome, In the Wake of the Sea-Serpents, summarily lists it as such. It is then utterly baffling that some cryptozoology sites insist that this is still a valid mystery. Apparently, some people sincerely believe that this is roaming the oceans:

A thin membrane was added between the tusks so it would have some semblance of functional morphology. Baleen whales probably have the most 'alien' looking mammalian skulls around, so it is quite difficult imagining what a blind reconstruction would look like. I'll admit I just wanted to draw something which looked like a bird skull with pincers coming out of it.

This article is a runaway introduction to a somewhat more rigorous topic - giving extinct whales proper amounts of soft tissue. Yes, shrink-wrapped cetacean reconstructions have been done in all sincerity despite, as this post hopefully demonstrated, that making no sense whatsoever.

References:

Carrier, D. R., Deban, S. M., and Otterstrom, J. (2002). The face that sank the Essex: potential function of the spermaceti organ in aggression. The Journal of Experimental Biology 205, 1755-1763. Available.

Clarke, M. R. (1978). Structure and Proportions of the Spermaceti Organ in the Sperm Whale. Journal of the Marine Biological Association of the United Kingdom 58, 1-17. Available.

Arctotherium angustidens: Biggest Bear Ever?

I have a bit of an obsession with animal size superlatives, and megabears* are among my favorites - that's right, I have interests beyond testudines. Anyways, in this blog's even more poorly-written past, I discussed purported giant hypercarnivores wherein I argued that the One-Ton(ne)-Hyperpredatory-Arctodus meme is unsubstantiated Godzillafication which somehow managed to infect even some peer-reviewed literature. Brian Switek wrote an article at the old Laelaps covering newer research which further demolished the mythology of the Giant Short-Faced Bear: it didn't have a short face (it did have a deep snout), or particularly long legs (somewhat of an optical illusion caused by a short back), and was probably a generalist omnivore like extant bears (presumably with some differences in niche, of course). Just as it seemed that speculations about One-Ton(ne)-Hyperpredatory-Bears would be a thing of the past, this happened:

* Definition pending.

Figure 2(1) from Soibelzon and Schubert (2011). The bear's height is ~ 3.3 meters (10' 10") and note how the legs are realistically flexed.

Arctotherium is composed of 5 South American species - of which A. angustidens is the earliest, largest, and apparently most predatory - and is the sister clade of Arctodus; the two are in turn part of the clade Tremarctinae which further includes Tremarctos (spectacled bear and kin) and Plionarctos (Soibelzon and Schubert 2011). The Arctotherium angustidens specimen of concern is not a new discovery, as it was found prior to 1935 during construction of a hospital in La Plata, Argentina (Soibelzon and Schubert 2011). It is presently composed of radii, ulnae, and humeri from both forelimbs; metacarpals, phalanges, and a scapula fragment were also recovered but unfortunately lost (Soibelzon and Schubert 2011). The dimensions of the bones* are incredible, the humerus has a length of 62 cm (2' 0.4") and the mid-shaft humerus width is 9 cm (3.5"); comparable maximum measurements of other giants bears are: Arctodus simus - 59.4 cm/6.4 cm; Ursus spelaeus - 44.8 cm/5.6 cm; and Ursus maritimus - 38.5 cm/4.65 cm (Soibelzon and Schubert 2011). For those who would prefer a more graphical comparison:

* The limbs had somewhat different measurements - the left was shorter and wider and the right vice versa. See below for why.

Humerus length in cm:

The number of specimens is in parenthesis. This does not include both limbs from the Arctotherium specimen in question, subsequently the average was re-calculated from Table 3.

Humerus mid-shaft width in cm:

Table 5 figures kept the specimens in question separate (unlike the prior example) so the range and average have been re-calculated. Even without the newly measured specimen, the average for Arctotherium was substantial (5.88 cm).

Using humerus greatest length, humerus mid shaft circumference, humerus greatest distance of distal epiphysis, and radius proximal epiphysis greatest diameter, the estimated weight for the giant Arctotherium angustidens specimen ranged from 983-2042 kg (2,167-4,502 lbs), with the value likely around the mean and median of 1588 and 1749 kg (3501-3856 lbs), respectively (Soibelzon and Schubert 2011). The other known specimens were given the same treatment (when possible), and a couple of them appeared to mass around a tonne (Soibelzon and Schubert 2011). This would seem to suggest that the giant Arctotherium angustidens specimen was not an outsized freak, and could represent a "normal" maximum size for the species. Before too many conclusions can be made, some more discussion of the specimen is in order.

Left humerus in caudal view. The scale bar is 10 cm (~ 4 inches) and the arrow points to a pathology.  Taken from Figure 3(1), Soibelzon and Schubert (2011). Compare with the humerus of Arctodus: here.

The most striking aspect of this specimen are the osteogenic changes to the deltoid crests of both humeri - more apparent in the left humerus pictured above, see arrow - and the distal third of the left radius shaft, which suggest a deep injury followed by infection and then new vascular growth over a long period of time (Soibelzon and Schubert 2011). Judging by the high degree of epiphyseal fusion, the specimen managed to become an old adult (Soibelzon and Schubert 2011). Humeral mid-shaft measurements gave on average larger estimated masses (Soibelzon and Schubert 2011 - Table 3), which makes me wonder if the measurements were artificially inflated by the injury and subsequent pathological growth. However, the limited data on Table 3 shows similar proportions with a somewhat smaller specimen:

	HMSC	HGL	HMSC/HGL
MLP 35-IX-26-5	26.5	61.5	43%
MLP 35-IX-26-6	26.2	62	42%
MACN 5132	22	54	41%
MLP 82-X-22-2	16	49.5	32%

Measurements in cm: HMSC = Humerus mid shaft circumference; HGL = Humerus greatest length. The first two rows are from the specimen in question.

Curiously, specimens of Arctotherium angustidens appear to differ considerably in limb proportions, for instance, two specimens have the same humeral circumference (22 cm) but the greatest diameter of the distal humeral epiphysis differs considerably (20.5 vs. 18 cm), one of which is larger than the giant specimen's maximum measurements (18.5 cm) (Soibelzon and Schubert 2011)... this is certainly confusing, and the value of compiling median and mean figures is readily apparent. While the mass of the giant Arctotherium angustidens cannot be precisely pinned down, the available evidence suggests it exceeded all other bears in size.

... or does it?

Incredibly, one mass regression of Indarctos atticus exceeded 3 metric tonnes, although predictably it was found to be highly improbable (Finarelli and Flynn 2006) and, along with fellow Mio-Pliocene bear Agriotherium, they are not believed to have reached the same size as Arctodus simus or Arctotherium angustidens (Soibelzon and Schubert 2011). Polar bears (U. maritimus) can get extremely large*, with one specimen shot in Alaska in 1960 purportedly standing 3.39 m (11' 1.5") and weighing 1002 kg (2210 lbs); the whereabouts are apparently unknown and the skull was never submitted for measurement (Wood 1981). Assuming the record is genuine, I'm wondering if the height included unnaturally straitened legs or was in fact the length lying down and outstretched, which would certainly be easier to take. Considering the largest Arctotherium angustidens humeral length is about 160% as large as the largest polar bear measurement included in Soibelzon and Schubert (2011), it would take one freakish polar bear to get that tall, and it would probably weigh a lot more than a tonne. Polar bears reached their largest sizes in the late Pleistocene (Soibelzon and Schubert 2011) and Ursus maritimus "tyrannus" apparently had an ulna 44 cm in length (see Markus Bühler's Bestiarium, comment #5), which is of course smaller than that of the specimen in question's (57 cm), but still surprisingly large for a single specimen. Information on these giant polar bears is unfortunately quite hard to come by, but I think it's safe to assume it didn't exceed Arctotherium angustidens in size, at least regularly.

* DeMaster and Stirling (1981) give maximum figures of: mass 800 kg (1764 lbs), nose-tail length 2.5 m (8' 2"), and shoulder height 1.6 m (5'3").

Exactly how the average sizes of the giant bears compare is difficult to determine at the present time - particularly when gender isn't obvious. However, as weights of a tonne or more appear to have been reached by Arctotherium angustidens regularly, the average must have considerably exceeded that of other giant bears, which have only been demonstrated to exceed a tonne in one instance. The authors' assertion that Arctotherium angustidens was the biggest bear ever is well-supported, until something bigger turns up.

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This post has run long enough, I'll write a followup on the proposed ecology of Arctotherium angustidens shortly.


References:

DeMaster, D. P., and Stirling, I. (1981). Ursus maritimus. Mammalian Species 145, 1-7. Available.

Finarelli, J. A., and Flynn, J. J. (2006). Ancestral State Reconstruction of Body Size in the Caniformia (Carnivora, Mammalia): The Effects of Incorporating Data from the Fossil Record. Systematic Biology 55(2), 301-313. doi: 10.1080/10635150500541698. Available.

Soibelzon, L. H., and Schubert, B. W. (2011). The Largest Known Bear, Arctotherium angustidens, from the Early Pleistocene Pampean Region of Argentina: With a Discussion of Size and Diet Trends in Bears. Journal of Paleontology 85(1), 69-75. doi: 10.1666/10-037.1

Wood, G. L. (1981). The Guinness Book of Animal Records. Guinness Superlatives: Middlesex, Great Britain.

Cryptozoological Case File #0002 - The Elephant Seals Of Ecuador

The following reports admittedly stretch what can be considered cryptozoological. There is no doubt the animals in question are of a known species, but the identification is uncertain, the location in which they were observed was unusual, and no physical evidence was collected. I hope the authors don't take offence to my categorization, it is merely to demonstrate that investigating unusual reports is not some joke, and even without 'hard' evidence the investigation can be worthy of publication in a peer-reviewed journal.

My thanks to Markus Bühler for directing me to this story. All references from Alava and Carvajal (2005) until otherwise noted:


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In December 1998, communities along the Babahoyo River, (Ecuador) were alarmed to see an unusual animal in the water, which a local television station managed to tape. The animal appeared to be a pinniped, and with a large head, large eyes, and absence of external pinnae, the authors and a marine mammal specialist identified it as an elephant seal (Mirounga), probably an immature male 4 years of age. A subsequent 8 hour survey of the river failed to locate the animal.


In February 2002, an elephant seal was observed in an estuarine area in Guayaquil city, first near a power plant and then in a shrimp farm. The individual was lying on the bottom of the shrimp pond (partially submerged), and was estimated to be 3 meters long by workers. The authors observed the animal while in a narrow creek near the farm and took photographs for future identification, where they once again reasoned that it was an elephant seal.


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For those out there that didn't click on the maps, the first sighting occurred about 75 miles (120 km) upriver, while the second was about 50 miles (80 km) up but was over a mile (1.6 km) into a salt marsh.


How many animals were involved? The authors don't bring it up directly, but say "these two individuals" at one point. It would seem remarkable for two separate individuals to wind up in the same river system, although it is more parsimonious than assuming one individual survived the excursion and for some reason returned. As for the species...


Both events took place during the Southern Elephant Seal (Mirounga leonina) moulting season and La Niña events (Alava and Carvajal 2005), which was previously linked to the presence of Otaria flavescens in the region (Felix et al. 1994). Elephant seals are of course far from indolent beach blobs, and Alava and Carvajal (2005)'s review of the literature reveals both species can migrate thousands of kilometers, although the Southern species (M. leonina) appears to migrate more extensively and the Northern species (M. angustirostris) has not been observed to wander out of the North Pacific. Southern Elephant Seals have been observed off the coast of Sawqarah, Oman (Johnson 1990) and 46 (!) records are known from Brazilian coastal states, up to Pernambuco and the Fernando de Noronha archipelago (de Moura et al. 2010)), which demonstrates that the species can reach the equator. The authors cautiously suggest their records are the northernmost yet of juvenile southern elephant seals, but cannot reject the possibility of the southernmost record of the northern elephant seals (Alava and Carvajal 2005). It could be possible that both occurred, but in all likelihood the same species was drawn to the same region for some obscure reason.




As far as other instances of elephant seals in cryptozoology, Roy Mackal once hypothesized that the White River monster was a very wayward elephant seal - wayward in that the sightings were in Arkansas! One blogger hypothesized that a monster seen in the Solimões River was a wayward northern elephant seal (thanks to geographical confusion), but it could be possible for southern elephant seals to enter South American rivers - it still doesn't explain the reported small eyes, snake-like neck, and incorrectly reported country for the river.




References:


Alava, J., and Carvajal, R. (2005). First records of elephant seals on the Guayaquil Gulf, Ecuador: On the occurrence of either a Mirounga leonina or M. angustirostris. The Latin American journal of aquatic mammals 4(2): 195-198. Available.


de Moura, J., di Dario, B. Lima, L., and Siciliano, S. (2010). Southern elephant seals (Mirounga leonina) along the Brazilian coast: review and additional records. Marine Biodiversity Records 3, doi: 10.1017/S1755267209991138






Secondary References (cited by Alava and Carvajal 2005):




Felix, F., Haase, B., Samaniego, J., and Oechsle, J. (1994). New evidence of the presence of the South American sea lion Otaria flavescens (Carnivora Pinnipedia) in Ecuadorian waters. Estudios Oceanológicos 13, 85-88.


Johnson, D. (1990) A southern elephant seal (Mirounga leonina) in the Northern Hemisphere (Sultanate of Oman). Marine Mammal Science 12: 242-243.

Stupendemys: Giant Amongst Mega-Turtles

In the first post of this accidental series, I raved about using Strait Carapace Length (SCL) to compare turtle sizes, made up the designation 'Mega-Turtle' for species regularly exceeding a 2 meter SCL, and to my horror discovered that proper descriptions of most Mega-Turtle specimens are either very hard to find or currently non-existent. At some point I'd love to cover the more obscure Mega-Turtle and near-Mega-Turtle species, but my taste of the topic thus far was of sheer frustration. This post will finally cover my intention of writing about Mega-Turtles in the first place: giving some attention to the largest species of them all, for once.

Oh, and here's the teaser graphic from last time with proper captions:

Left to Right: Archelon ischyros (black) with speculative 2.5 m SCL (4.5 m total length); A. ischyros (gray) with 1.93 m SCL - also representing speculative Protostega gigas of similar size (both 3.4 m total length);  Psephophorus sp. (black) with speculative 2.1 m SCL (model based on extant leatherback); average extant leatherback (Dermochelys coriacea) (gray) with 1.5 m SCL; Drazinderetes tethyensis with known 1.25 m bony shell (black) and speculative ~2 m soft shell (gray); Stupendemys geographicus specimens, discussed below.

The colorfully named Stupendemys geographicus is a pleurodire, or side-necked turtle, and hence a very distant relative of the other Mega-Turtles. Stupendemys was discovered in 1972 from "late Tertiary" deposits in Venezuela and first described in Wood (1976). The paratype specimen described by Wood (1976) had a fairly complete carapace (amongst other bits and pieces) with an SCL of 2.35 m and carapace width of 1.85 m - it is the gray shell in the above figure. Another author (Wood 1982) estimated the specimen had a total length of 3.65 m and weight of roughly 2 tonnes, presumably from scaling up extant relatives. The type specimen was more fragmentary and even larger, with an estimated SCL of 2.50 m and width of 1.90-1.95 m (Wood 1976). The Pierre Shale Archelon probably has an SCL comparable to the Stupendemys type specimen, although it is hard to say which is larger as Archelon has a very wide carapace and Wood (1982) suggests it was lightweight compared to Stupendemys geographicus due to reduced ossification. It is curious that popular sources claimed Archelon to be the 'largest turtle ever' in the first place - possible explanations include the discovery of Archelon in the English-speaking world and subsequent bias, the impressive completeness of the Yale and Vienna specimens, and only having the 4.5 m total length figure reproduced*. There is no longer any excuse to claim Archelon as the record-holder.

* Heuvelmans (1968) humorously stated the Yale specimen had a 12 foot carapace and 25 foot total length - despite a plate in the book clearly demonstrating otherwise! He then goes on to claim that "[t]here are some reasons for thinking that such giants might have survived" and listed some vague Father-of-all-the-Turtles type legends. Curiously, he tossed the type in the end due to vagueness.



In 1992, and the same locale as the type and first paratype, a Stupendemys geographicus was uncovered with a 3.3 m SCL and 2.18 m carapace width (Scheyer and Sanchez-Villagra 2007, Orenstein 2001) - this specimen is portrayed as the black shell on the increasingly distant figure. It is astounding that the largest known turtle shell is only from the late Miocene, or approximately 5-6 million years ago. Scaling up from the extrapolations in Wood (1982) gives a possible total length of 5.25 m and weight of around 6 tonnes - however the shell is proportionally narrow in this specimen, as the type and paratype predicted ~2.5 m and 2.6 m, respectively. It is unfortunate that I cannot find the original publication and any photographs within, but it is at least cited by several papers (i.e. it exists!). Scheyer and Sanchez-Villagra (2007) investigated fragmentary costals from the same individual and determined that the turtle had a normal mode of growth, unlike fast-growing Archelon and the extant leatherback, and took at the very least three decades to reach a 3.3 m carapace - possibly as long as 60 or 110 years! The authors also hinted at the possibility that Stupendemys geographicus had size variants due to sexual dimorphism, presumably with other specimens in mind (Scheyer and Sanchez-Villagra 2007).

The vast shell of Stupendemys geographicus. From Wikipedia Commons, author Ghedoghedo.

Scheyer and Sanchez-Villagra (2007) noted that Stupendemys geographicus has a shell with a lightweight diploe construction - and retained stability - as a consequence of scaling effects, however it does not resemble the spongy bone typical of Archelon and other tetrapods with an open marine habitat. The flattened shell of S. geographicus is a strong indicator of an aquatic habitat, while the vast size suggests the turtle probably only left the water to lay eggs (Wood 1976). Wood (1976) was uncertain if S. geographicus was a marine or freshwater species, but it has been determined the formation it was recovered from was near-shore/low coastal savanna/freshwater river (Bocquentin and Melo 2006). Fossil associations seem to imply that S. geographicus was littoral (Bocquentin and Melo 2006), and Wood (1976) speculated that it may have had flippers. Bocquentin and Melo (2006) described another Stupendemys species, S. souzai, which was smaller in size, had a strange vertical collar-like structure suggesting poor swimming ability, and was found in continental areas where it may have inhabited swamps and small streams. Subsequent workers criticized the placement of the assorted solitary elements into S. souzai and argue that material may not even represent Stupendemys (Meylan et al. 2009). That's right, there were other large - but perhaps not giant - pleurodires from the Amazonian Miocene...

One of those other species is Caninemys tridentata, which is known only from a skull with a bulldog-like shape and canine-like projections (Meylan et al. 2009). This skull was assumed to be from a Stupendemys at first, but is only half the expected size (estimated SCL of 1.2-1.5 m) and probably represents a different taxa (Meylan et al. 2009). It is possible that the suggestion of Stupendemys being a predaceous species from Bocquentin and Melo (2006) was based off this skull, as I can't think of any other morphology that would be telling in this regard. Wood (1976) claimed that S. geographicus was "largely if not entirely herbivorous" because "all of the largest living turtles... are totally (or nearly totally) herbivorous" - I have no idea why someone would think this. The largest extant podocnemidid pleurodire, Podocnemis expansa - with an SCL up to 0.82 m (Wood 1976) - is herbivorous, although diet in the genus is rather variable (Teran et al. 1995). Until cranial remains which can be unambiguously assigned to Stupendemys are found, this area of its biology should best be left a blank.

Stupendemys geographicus with somebody else's skull. From Wikipedia Commons, author Ryan Somma.

Could Stupendemys actually have been a prey item? It appeared to overlap in time and range with the Mega-Caiman Purussaurus which had a 1.5 m head and ~12 m total length - and possible weight of ~10+ tonnes. This website has a photo of a "tortoise" shell (from Stupendemys or another pleurodire?) with a Purussaurus bite... which the turtle survived. It seems unlikely that a 3 m+ SCL Stupendemys would have been easy prey, and may have been effectively predator-free. This could suggest that extreme size and a carapace only reduced for mechanical purposes could have evolved at least partially in response to such a gargantuan predator.


It appears that a lot of Stupendemys biology remains a mystery, undoubtedly thanks in part to the lack of anything analogous in this Megafauna-deprived era. There are some vague references to other South American pleurodires of a size comparable to Stupendemys, such as some very large cervicals (Orenstein 2001) - but it would probably be best to wait and see how things get sorted out. The diversity of this not-to-distant time was truly staggering - there were 12 probably sympatric crocodile from the same locale as the Stupendemys holotype - so I can't imagine what other surprises the continent has in store. 

References:

Bocquentin, J. and Melo, J. (2006) Stupendemys souzai sp. nov. (Pleurodira, Podocnemididae) from the Miocene-Pliocene of the Solimões Formation, Brazil. Revista Brasileira de Paleontologia 9(2), 187-192. Available.


Heuvelmans, B. (1968). In the Wake of the Sea-Serpents. Hill and Wang: New York.


Meylan, P., et al. (2009). Caninemys, a New Side-Necked Turtle (Pelomedusoides: Podocnemididae) from the Miocene of Brazil. American Museum Novitates 3639.

Orenstein, R. (2001). Turtles, Tortoises & Terrapins: Survivors in Armor. Firefly Books: Buffalo, New York USA.

Scheyer, T. and Sanchez-Villagra, M. (2007). Carapace bone histology in the giant pleurodiran turtle Stupendemys geographicus: Phylogeny and function. Acta Palaeontol. Pol. 52(1), 137–154


Teran, F. et al. (1995). Food Habits of an Assemblage of Five Species of Turtles in the Rio Guapore, Rondonia, Brazil Augusto. Journal of Herpetology 29(4), 536-547. URL

Wood, G. (1982). The Guinness Book of Animal Facts and Feats. Guinness Superlatives Limited: Middlesex, England.

Wood, R. (1976). Stupendemys geographicus, the world's largest turtle. Brevoria 436, 1-31. Available.