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 Baby Cadborosaur No More. Part 6b: Reptilian Reproduction

Here's that quote again, from LeBlond and Bousfield (1995), page 82:

The thinness and elongation of the body, the poikilothermy (or cold-bloodedness) which it seems to imply, and the great difference in size between the young and the adult are strong points in favour of a reptilian nature. 

The previous article argued that a "cold-blooded" 'Cadborosaurus' is actually strongly at odds with known 'reptilian' physiology; similarly, the birth of extremely small live young would in fact be highly unusual for a marine reptile.

Backing up, this is the evidence LeBlond and Bousfield (1995) present for comparatively tiny precocial young (page 80):

A very small individual, probably a baby, was caught (by W. Hagelund) and another one, perhaps, was seen at the shore (by P. Harsh); both in relatively warm water. If these very small individuals are correctly associated with the larger ones, their size and where they were found might provide more clues about Caddy's nature.

Woodley et al. (2011) is of course all about why the Hagelund specimen should not be used as evidence, but makes no mention of the Harsh case. Is this... a major flaw in our paper? Absolutely not. The Harsh sightings are vague to the degree that they can be graciously described as unanalyzable. Phyllis Harsh reportedly found a "baby dinosaur" 2 feet (0.61 meters) long on a beach (which was ultimately returned to the water) and (!) a "small dinosaur skeleton" beneath a Bald Eagle nest, both on Johns Island. The sheer lack of detail is remarkable† and the description "dinosaur" can refer to just about anything‡. I find it interesting that LeBlond and Bousfield drew conclusions from this valueless anecdote, despite apparently having some reservations about it.

† For comparison, Hagelund's account had 24 traits, of which only a few were worthless. 
‡ Dinosauria proper has a diverse assortment of body plans, many other creatures are often incorrectly labeled as dinosaurs (ichthyosaurs, plesiosaurs, mosasaurs, Dimetrodon...), and some extant animals (snapping turtles, alligator gars, bichirs, sturgeon...) are often compared to "dinosaurs". 


LeBlond and Bousfield (1995) hypothesized that 'Cadborosaurus' "probably" gives live birth, reasoning that it doesn't have suitable limb morphology for digging nests and inhabits areas which are too cold for incubating eggs. Strangely, they also speculate that it has some reproductive tie to land, although whether it is to lay eggs or give live birth they don't specify. It is worth mentioning that there are only two reports of 'Cadborosaurus' on land and they are very very weird; in 1936 the Stephenson family reported a "90 foot-long, three-foot-thick animal wriggling over the reef into a lagoon" which was "yellow and bluish in colour" and in 1991 Terry Osland reported something "bigger than a killer whale" which was "hard to describe" and yet described as having the "smooth skin of a dogfish" which was of a "grey, silvery color" and had "no hair", a "tail rounded like a lizard tail" with "like little feet on the back of the tail" [sic] and no long neck.


There is another major problem in connecting the Hagelund specimen to 'Cadborosaurus', aside from the utter lack of resemblance - marine reptiles give birth to proportionally large young.

Determining exactly how large the Hagelund specimen is compared to a 'Cadborosaurus' is challenging due to the latter probably not being a valid concept. LeBlond and Bousfield claim a size range of 5-15 meters (which is not supported by the actual sightings), so let's go with a nice round 10 meters. This makes the 40 cm long Hagelund specimen only 4% of the adult length and somewhere in the neighborhood of 5 orders of magnitude less massive, say, around 0.0064%.

Out of the five or so extant clades of marine reptiles†, only the "true" sea snakes (Hydrophiini) give live birth; however as this is by far the most speciose marine clade with ~60 representatives (Sanders et al. 2010) it could be argued that most extant marine reptiles are live-bearers. Anyways, sea snakes tend to have small clutches and large offspring; averaging data from 10 species in Lemen and Voris (1981) gives a mean reproductive effort per embryo of 6.8 (stdev = 2.5, min = 2.1, max = 10.9), reproductive effort being what percentage of the mother's mass the embryo is. While relative lengths were not recorded, assuming similar proportions, this could 'translate' into newborns averaging 41% of the maternal length (min = 27%, max = 48%). It's amazing that more than one of these can fit into the parent snake. The reproductive effort per clutch averaged 32 across the sampled species (stdev = 5, min = 23.6, max = 38.9) and appeared to be fairly stable compared to embryo size.

† The others being seaturtles (Chelonioidea), the marine iguana (Amblyrhynchus cristatus), sea kraits (Laticauda spp.), and saltwater crocodiles (Crocodylus porosus)... the lattermost makes me wonder if other reptiles deserve this status, certainly the softshell turtle Trionyx should be considered. As for how sea snakes, sea kraits, and other elapids are related (Wikipedia's article is highly untrustworthy), Catalogue of Organisms has an excellent summary.


Live birth appears to have been very common in extinct marine reptiles, although as can be imagined, data on this subject is quite scarce. It was recently confirmed that plesiosaurs gave live birth, with Polycotylus latippinis estimated to have a fetus 35% of the maternal length at full term (O'Keefe and Chiappe 2011). The mosasauroid Carsosaurus marchesetti was discovered with four embryos which (according to Figure 2) were around 30 cm long relative to a 2 meter adult (Caldwell and Lee 2001), making the young around 15% of the maternal length. Caldwell and Lee (2001) were uncertain how close to term the embryos were as they were placed posteriorly in the mother, but showed some signs of displacement. Then there is the famous fossil of the ichthyosaur Stenopterygius quadriscissus showing a juvenile half-emerged from its mother, which seems to be around a quarter of the parental length.


Thus, LeBlond and Bousfield's argument that tiny precocial young indicate a 'reptilian' identity is completely at odds with live birth in marine reptiles. There was a discussion of this in Woodley et al. (2011) but it was eventually deemed tangential as the Hagelund specimen was already reclassified and the dead horse was already beaten into a liquid.



References:

Caldwell, M. W., and Lee, M. S. Y. (2001). Live birth in Cretaceous marine lizards (mosasauroids). Proc. R. Soc. Lond. B. 268, 2397-2401. Available.

LeBlond, P. H. & Bousfield, E. L. (1995). Cadborosaurus, Survivor from the Deep. Victoria, British Columbia: Horsdal & Schubart.

Lemen, C. A. and Voris, H. K. A. (1981) Comparison of Reproductive Strategies among Marine Snakes. Animal Ecology 50, 89-101. Available.

O’Keefe, F. R. & Chiappe, L.M. (2011). Viviparity and K-selected life history in a Mesozoic marine reptile. Science 333, 870-873. DOI: 10.1126/science.1205689

Sanders, K. L., Mumpuni, Lee, M. S. Y. (2010). Uncoupling ecological innovation and speciation in sea snakes (Elapidae, Hydrophiinae, Hydrophiini). Journal of Evolutionary Biology 23(12) DOI: 10.1111/j.1420-9101.2010.02131.x

Woodley, M. A., Naish, D. & McCormick, C. A. (2011). A Baby Sea-Serpent No More: Reinterpreting Hagelund's Juvenile "Cadborosaur" Report. Journal of Scientific Exploration 25(3), 495-512.



Previous entries:

A Baby Cadborosaur No More. Part 1: Introduction

A Baby Cadborosaur No More. Part 2a: Hagelund's Account

A Baby Cadborosaur No More. Part 2b: Hagelund's Account - annotated

A Baby Cadborosaur No More. Part 3: Dealing With Traits

A Baby Cadborosaur No More. Part 4: What is 'Cadborosaurus'?
A Baby Cadborosaur No More. Part 5: Hagelund's Specimen And The Cadborosaurus
A Baby Cadborosaur No More. Part 6a: Cold Water on the 'Reptilian Hypothesis'

Tet Zoo Coverage: 
A baby sea-serpent no more: reinterpreting Hagelund’s juvenile Cadborosaurus

A Baby Cadborosaur No More. Part 6a: Cold Water on the 'Reptilian Hypothesis'

LeBlond and Bousfield (1995) made remarkable conclusions about the affinities of 'Cadborosaurus' (page 82):

The thinness and elongation of the body, the poikilothermy (or cold-bloodedness) which it seems to imply, and the great difference in size between the young and the adult are strong points in favour of a reptilian nature. 

I will cover why the second half of the sentence is incredibly wrong in a following post. This was originally going to be a footnote, but quickly got out of hand.

The authors hypothesized that since 'Cadborosaurus' is "long and narrow in shape" it has too much surface area to maintain a high body temperature and is thus an ectotherm†. I do not find this reasoning convincing. The slimmest cetacean is the Northern Right Whale Dolphin (Lissodelphis borealis) which has a fineness ratio (maximum length/maximum thickness) of up to 10.9 (Fish 1993 - citing Leatherwood and Walker 1979) and yet it occurs in the north Pacific up to the Aleutians (Baird and Stacey 1990). Leopard seals are also quite slender and occur in Antarctica. Both of these ectotherms are compared to snakes by some observers (L. borealis is sometimes even called the "snake porpoise") despite being elongated and not truly anguilliform, which makes me wonder how literally the "snake-like" description of 'Cadborosaurus' should be taken. LeBlond and Bousfield based their image of 'Cadborosaurus' on the ultra-svelte (fineness ratio of over 30) Naden Harbour carcass, which is probably the spinal column (and attached bits) from a known species.

† LeBlond and Bousfield actually state 'poikilothermic', but this is not the correct usage; 'ectothermic' refers to relying primarily on the environment for body temperature and 'poikilothermic' refers to the ability to withstand a wide range of body temperatures. The authors also erroneously used 'homeothermic' for 'endothermic'; 'endothermic' refers to relying primarily on internal sources for body temperature and 'homeothermic' refers to organisms which keep a stable body temperature, either internally or through the environment.

LeBlond and Bousfield claim that 'Cadborosaurus' normally inhabits 5-12 °C waters with inferred ventures into colder waters (from the Naden Harbour carcass being ingested by a Sperm Whale) and to warmer waters for reproduction... more on that later. Remarkably, there is an elongated marine reptile which can tolerate these temperatures. The Pelagic Sea Snake Pelamis platura barely straggles into California due to the 18 °C isotherm, but can tolerate 16-18 °C (stops eating), 7-8.5 °C (stops swimming), 6-6.5 °C (falls into torpor), and even exposure to temperatures of 5 °C for an hour (Graham et al. 1971). Graham et al. (1971) telling describe this snake as "weak swimming", which makes me wonder, isn't an ectothermic 'Cadborosaurus' with a "very high swimming speed" contradictory?

Pelamis platura, apparently the most cold-tolerant marine reptile which isn't a turtle. From Wikipedia Commons.

The Leatherback Seaturtle (Dermochelys coriacea) is presently viewed as an uncommon seasonal resident of British Columbia (McAlpine et al. 2004) and is suggested to be occupying marginal habitat as far north as Alaska (Hodge and Wing 2000). Leatherbacks are physiologically remarkable, as they are capable of diving into waters as cold as 0.4 °C (James et al. 2006) and retain heat through a thick layer of blubber (unique among reptiles) along with their large size (Wallace and Jones 2008, Davenport et al. 2009). Leatherbacks are not the only turtles known from high latitudes; Green Seaturtles (Chelonia mydas) have been reported from British Columbia (McAlpine et al. 2004) and Alaska, and there are records of Loggerhead (Caretta caretta) and Olive Ridley Seaturtles (Lepidochelys olivacea) in Alaska as well (Hodge and Wing 2000). Hodge and Wing (2000) suggest that the non-Leatherbacks in Alaska are straying out of their tolerable range, although McAlpine et al. (2007) warn that interest in Canadian seaturtles is recent and that their status off British Columbia needs assessment.

Dermochelys coriacea from Wikipedia Commons.

Since the only British Columbian marine reptiles are about as un-'Cadborosaurus'-like as is possible, I think that speaks volumes about the probability of the 'ectothermic' hypothesis.


Previous entries:

A Baby Cadborosaur No More. Part 1: Introduction

A Baby Cadborosaur No More. Part 2a: Hagelund's Account

A Baby Cadborosaur No More. Part 2b: Hagelund's Account - annotated

A Baby Cadborosaur No More. Part 3: Dealing With Traits

A Baby Cadborosaur No More. Part 4: What is 'Cadborosaurus'?
A Baby Cadborosaur No More. Part 5: Hagelund's Specimen And The Cadborosaurus


Tet Zoo Coverage: 
A baby sea-serpent no more: reinterpreting Hagelund’s juvenile Cadborosaurus


References: 

Baird, R. W. and Stacey, P. J. (1990). Status of the Northern Right Whale Dolphin (Lissodelphis borealis), in Canada. The Canadian Field-Naturalist 105, 243-250. Available.

Davenport, J., Fraher, J., Fitzgerald, E., McLaughlin, P., Doyle, T., Harman, L., and Cuffe, T. (2009). Fat head: an analysis of head and neck insulation in the leatherback turtle (Dermochelys coriacea). J Exp Biol 212, 2753-2759. doi: 10.1242/​jeb.026500.

Fish, F. E. (1993). Influence of Hydrodynamic Design and Propulsive Mode on Mammalian Swimming Energetics. Australian Journal of Zoology 42, 79-101. Available.

Graham, J. B., Rubinoff, I., and Hecht, M. K. (1971). Temperature Physiology of the Sea Snake Pelamis platurus: An Index of Its Colonization Potential in the Atlantic Ocean. PNAS 68(6), 1360-1363. Available.

Hodge, R. P., and B. L. Wing. (2000). Occurrences of marine turtles in Alaska waters 1960-1998. Herpetological Review 31,: 148-151. Available.

James, M. C., Davenport, J., and Hays, G. C. (2006). Expanded thermal niche for a diving vertebrate: A leatherback turtle diving into near-freezing water. Journal of Experimental Marine Biology and Ecology 335, 221–226. Available.

LeBlond, P. H. & Bousfield, E. L. (1995). Cadborosaurus, Survivor from the Deep. Victoria, British Columbia: Horsdal & Schubart.

McAlpine, D. F., James, M. C., Lien, J., Orchard, S. A. Status and Conservation of Marine Turtles in Canadian Waters. Herpetological Conservation 2, 85–112. Available.

McAlpine, D. F., Orchard, S. A., Sendall, K. A., and Palm, R. (2004). Status of marine turtles in British Columbia waters: a reassessment. Canadian Field-Naturalist 118(1), 72-76. Available.

Wallace, B. P., and Jones, T. J. (2008). What makes marine turtles go: A review of metabolic rates and their consequences. Journal of Experimental Marine Biology and Ecology 356, 8–24. Available.

Woodley, M. A., Naish, D. & McCormick, C. A. (2011). A Baby Sea-Serpent No More: Reinterpreting Hagelund's Juvenile "Cadborosaur" Report. Journal of Scientific Exploration 25(3), 495-512.


Secondary Reference:

Leatherwood, S., and Walker, W. A. (1979). The northern right whale dolphin Lissodelphis borealis Pede in the eastern North Pacific. In: Behavior of Marine Animal volume 3 (Eds H. E. Winn and
B. L. Olla.) pp. 85-141. (Plenum Press: New York.)

Groomed By A Vulture

Taken and modified from Wikipedia Commons.

American Black Vultures (Coragyps atratus) are remarkable opportunists. With meathook-like beaks adapted for hooking and slicing, they have the functional morphology of obligate scavengers (Hertel 1995)†, but they'll also take eggs, plant material, garbage, and live prey (Kauffman 2001). Groups have been observed preying on skunks and opossums (McIlhenny 1939) and even juvenile sheep and cattle (Humphrey et al. 2004). The frequency of livestock depredation isn't clear‡, as Avery and Cummings (2004) note that many supposed depredation events are inferred from vultures feeding on already-dead animals; vultures will aggressively pursue afterbirth (Humphrey et al. 2004), which raises the possibility that some 'attacks' are misinterpreted. I'm not attempting to acquit Black Vultures here, but their interaction with livestock clearly requires more study.

† Hertel (1995) doesn't show where C. atratus fits among the scavenger guild, but its extinct relative C. occidentalis tends to be towards the far end of variability. 
‡ This doesn't stop some thousands of Black Vultures from being shot every year - along with hundreds of Turkey Vultures (Cathartes aura) which are not part of this problem (Lebbin et al. 2010). How are these daggers working by the way? I've heard the asterisks were hard to see. I'm also a bit worried when one paragraph will inevitably require three footnotes.

Based on Fig. 1 from Sazima and Sazima (2010).

Similar to the reported events involving livestock, ARKive has video of Black Vultures eating Capybara afterbirth and attacking juveniles, but the relationship between the species is not simple antagonism. Sazima (2007) reviewed video evidence from São Paulo which showed vultures pecking at resting Capybaras, visibly removing ticks and probable organic debris, and the giant rodents changing their posture to allow for a more thorough cleaning. The vultures were also observed to peck at sores (Sazima 2007), but it doesn't seem clear if this was a beneficial removal of necrotic tissue (as the author seemed to imply), or the vultures testing what they could get away with. As for how the association between Black Vultures and Capybaras was formed, Sazima (2007) suggested that the vultures would be familiarized with Capybaras from pecking at the sores and ectoparasites of dead or dying individuals, trying their luck with resting and healthy individuals, being denied when their behavior becomes harmful, learning to seek out resting Capybaras as a food source, Capybaras having advantageous health as a result of grooming, Capybaras adopting soliciting postures, and then cultural transmission in Capybara populations. Sazima and Sazima (2010) mentioned an interesting incident where a vulture picking off organic particles and ticks from a resting Capybara and later flew to a site 100 meters away to feed on a roadkill Capybara, supporting the proposed link between feeding on carrion and grooming (it would have been perfect if the order was reversed...).

Sazima (2010) recorded a remarkable incident involving Black Vultures in São Paulo preening an Irish Setter, the only known instance of cleaner birds interacting with a terrestrial carnivore. Sazima (2010) suggested that the Black Vulture-Dog association could roughly parallel the Capybara situation - the vultures locate the dog resting, spot organic debris in the dog's fur (possibly from rolling on carcasses), approach the dog and begin to feed on organic debris in its hair, and have the dog tolerate their activity until it felt disturbed or was hurt. The dog receptive towards grooming was also recorded to playfully interact with a group of vultures (Sazima 2010), making me wonder if the dog felt preening was play as well. It is unknown if this interaction is localized and/or rare, or if it has been overlooked due to its unpredictable nature and/or lack of attention (Sazima 2010).

Zamuro quitándole parásitos a un Caricare encrestado from Flickr user barloventomagico.

Intraspecific allopreening has been widely observed in birds (including vultures), however interspecific allopreening is a rarity, and has mostly been observed in cowbirds (Palmeira 2008 - citing various). Palmeira (2008) observed Black Vulture/Southern Caracara (Caracara plancus) grooming/preening in Mato Grosso do Sul, Brazil; the Caracara solicited with a head-down display, and subsequently the birds began to simultaneously groom one another. Similar events have been reported from Minas Gerais, Brazil (Souto et al. 2009) and Texas (Ng and Jasperson 1984). The above photo appears to show similar behavior in Venezuela. It would then seem probable that this behavior occurs wherever Black Vultures co-exists with Caracara plancus and C. cheriway, which would be everything from Tierra del Fuego to the southern US.

So why does this behavior occur? Ng and Jasperson (1984) suggest a parallel with cowbirds, which also use a head-down display, in that it could allow Caracaras to join a Black Vulture flock for feeding and roosting. Souto et al. (2009) further suggest that mixed flocks could have the benefits of increased surveillance, the ability of Caracaras to vocalize alarm calls would benefit Black Vultures, and the ability of Black Vultures to locate carrion would benefit Caracaras. I'm curious as to why Caracaras demonstrate this apparent social association-building behavior with Black Vultures and not Turkey Vultures, as the latter has also been observed to intraspecifically allopreen (Souto et al. 2009 - citing Harrison 1965) and is apparently better at finding carcasses (probably by olfaction), even buried ones (Smith et al. 2002). It's worth noting that Sazima (2007) suggested that the long and slender bill of Black Vultures, capable of tearing flesh from small carcasses and catching live insects, makes them excellent pickers and thus potential cleaners. I suspect, for whatever reason, Black Vultures have a propensity towards grooming and aren't particularly fussy about their clientele.




As for why Black Vultures don't go around grooming everything - say (to tie up loose ends) livestock - maybe only a few population in Brazil have learned that preening large mammals results in food. Alternately, Black Vultures could be preening everything that doesn't put up much of a fuss, but such incidents have yet to be recorded in the proper literature.





References:


Avery, M. L. and Cummings, J. L. (2004). Livestock Depredations by Black Vultures and Golden Eagles. Sheep & Goat Research Journal 19, 58-63. Available.


Fisher, H. I. (1944). The Skulls of the Cathartid Vultures. The Condor 46(6), 272-296. Available.


Hertel, F. (1995). Ecomorphological indicators of feeding behavior in recent and fossil raptors. The Auk 112(4), 890-903. Available.


Humphrey, J. S., Tillman, E. A., and Avery, M. L. (2004). Vulture-Cattle Interactions at a Central Florida Ranch. Proceedings - Vertebrate Pest Conference 21, 122-125. Available.


Kauffman, K. (2001). Lives of North American Birds. Houghton Mifflin Harcourt.


Lebbin, D. J., Parr, M. J., Fenwick, G. H. (2010). The American Bird Conservancy Guide to Bird Conservation. University of Chicago Press.



McIlhenny, E. A. (1939). Feeding habits of black vultures. Auk 56, 472–474.


Ng, D., and Jasperson, B. D. (1984). Interspecific Allopreening Between Crested Caracara and Black Vulture. The Condor 86, 214-215. Available.


Palmeira, F. B. L. (2008). Allopreening behavior between Black Vulture (Coragyps atratus) and Southern Caracara (Caracara plancus) in the Brazilian Pantanal. Revista Brasileira de Ornitologia 16(2), 172-174. Available.


Sazima, I., and Sazima, C. (2010). Cleaner birds: an overview for the Neotropics. Biota Neotropica 10(4), 183-194. Available.


Sazima, I. (2010). Black Vultures (Coragyps atratus) pick organic debris from the hair of a domestic dog in southeastern Brazil. Revista Brasileira de Ornitologia 18(1), 45-48. Available.


Sazima, I. (2007). Unexpected cleaners: Black Vultures (Coragyps atratus) remove debris, ticks, and peck at sores of capybaras (Hydrochoerus hydrochaeris), with an overview of tick-removing birds in Brazil. Revista Brasileira de Ornitologia 15(3), 417-42. Available.


Smith, H. R., DeGraff, R. M., and Miller, R. S. (2002). Exhumation of Food by Turkey Vultures. Journal of Raptor Research 36(2), 144-145. Available.

Souto, H. N., Franchin, A. G., and Júnior, O. M. (2009). New Records of Allopreening Between Black Vultures (Coragyps atratus) (Ciconiiformes: Cathartididae) and Crested Caracara (Caracara plancus) (Falconiformes: Falconidae). Sociobiology 53(1), 125-129. Available.

An Interlude Of Poorly-Reconstructed Bears

There's too much on my plate right now to allow for a proper followup on the Bad-Ass Mega-Bear Arctotherium angustidens - now one of my most visited posts, wow! - so I figured to do some recycling in the interim. I have a lot of unfinished posts, one of which on deceptive soft tissue so happens to have a section on bears. So, I excised the opening paragraphs and expanded on the bear section a bit to serve as an introduction to the topic in general and tie in with a cryptic statement in the prior post. Don't worry, it gets to bears soon.

For all of the awesome, mind-blowing fossil reconstructions out there, some are incredibly lazy. Particularly noxious offenders include mimeographing inaccurate morphology from prior works (e.g. pronated theropod hands, elephantine sauropod hands), portraying extinct animals as identical to distant modern relatives (e.g. Teratorns-as-Condors, Kayentachelys-as-Snapping-Turtle, Prosalirus-as-Bullfrog...), and of course portraying live animals as shrink-wrapped skeletons:

*Cough*

SV-POW!'s kickass articles on sauropod life reconstructions (Part 1, Part 2) served as a major catalyst for my interest in this topic, particularly the second part which explains how portraying 'pods with freakish shrink-wrapped skull-heads has become common, if not expected in palaeo-art. I'd like to suggest that Shrink Wrapped Dinosaur Syndrome (SWDS) is but a facet of a larger phenomenon in which an animal's appearance as determined by skeletal structure, soft tissue, and external cover (hair, feathers) is improperly depicted and/or misunderstood*. Just look at that poor Dimetrodon up top (from Cleland 1916), yeesh. This phenomenon is not limited to fossils, as it can afflict carcasses still in the process of rotting or even live animals.

*Snazzy acronym pending

Since I'm not exactly a skilled re-constructionator, I figured I could put my not-skills to use and concentrate on reconstructing animals incompetently, in the hope of deconstructing some reconstruction myths. Or something.

...

Let's say a clever yet ignorant individual finds a decomposed corpse out in the woods, perhaps reduced to a skeleton with a few globs of flesh and hair still attached. It doesn't remind them of any animals they've ever seem, so they take a stab at reconstructing the presumed cryptid:

The person posts the reconstruction online, along with some blurry photographs of the remains taken at surreal angles typical of German Expressionism. Commenters suggest seemingly random and inexplicably specific taxa for the animal's identity, including the weird mustelid Ekorus, Bigfoot, the weird peccary Mylohyus, non-mammalian synapsid Titanophoneus, and a werewolf. Eventually, a near-consensus is reached suggesting that the carcass is of a late-surviving juvenile "short"-face bear Arctodus. Of course, the animal in question is actually this:

From Wikipedia Commons.

The contrast between the popular conception of bears being stumpy-legged fatties and their skeletons is truly remarkable. My "reconstruction" is cribbed from a skeleton figured in The Royal Natural History: Mammals (page 2) which unfortunately does not have a label, but appears to be an American Black Bear (Ursus americanus) as opposed to some fictional generalized bear. If the "reconstruction" looks familiar, that's because a mangy U. americanus was once confused for Bigfoot, and no, the legs of the creature are most certainly not "too long" to be from a bear. And since when is Bigfoot a quadruped?

Arctodus is typically portrayed as a bear on stilts, in sharp contrast to other species, but is truly not that different. It is almost always shown with rather short hair, which does occur in the Sun Bear, but is highly unlikely to occur out of the tropics; see serchio25's Deviant Art for an intriguing portrayal of Arctodus with more probable hair. It also doesn't help that when Arctodus is compared with other bears or people, it is shown at maximum size. It is now known that Arctodus simus has legs that are not elongated in comparison with other bears, and that the appearance of long legs is probably an optical illusion caused by a rather short back (Figueirido et al. 2010). Arctodus does seem to be rather gracile in build, at least in comparison with Arctotherium angustidens. Grrrraaaahhhh of Shaggy God (citing Nelson and Madsen 1983) informed me of the A. simus specimen UVP 015 with a femur 72.3 (28.5") in length, 6.4 cm (2.5") in mid-shaft width and (as estimated by Figueirido et al. 2010) a weight of 957 kg (2110 lbs); the largest Arctotherium angustidens (see the prior post) has a humerus length* of 62 cm (24.5"), a mid-shaft width of 9 cm (3.5"), and an amazing weight of 1588-1749 kg (3500-3855 lbs). It seems strange that two closely related and similarly sized bears would differ so much in build, especially when bears in general seem conservative in their body plan variation, as demonstrated below.

* Bear humeri seem to be slightly shorter than femurs. UVP 015 is still certainly the tallest bear ever.

And now, bears, bears, bears!

Arctodus simus from Figueirido et al. 2010. Note the outline, which includes hair.

Ursus americanus (Black bear) (?) modified from Wikipedia Commons. It seems to be somewhat shorter-bodied and leggier than Arctodus - is it a juvenile?

Ursus spelaeus ("cave bear") from Wikipedia Commons. Note the long body relative to A. simus and the similar leg length.

Helarctos malayanus (Sun bear) modified from Wikipedia Commons. Note the very short fur.

So yeah, Arctodus simus is certainly not long-legged or feline-like. Did the originators of the claim even bother to compare it with other bears?

References: 

Cleland, H. F. (1916). Geology Part II. Historical. American Book Company: New York, Cincinnati, Chicago. Available.

Figueirido, B. Perez-Claros, J. A., Torregrosa, V., Martin-Serra, A., Palmqvist, P. (2010). Demythologizing Arctodus simus, the 'short-faced' long-legged and predaceous bear that never was. Journal of Vertebrate Paleontology 30(1), 262 - 275. Available.

Lydekker, R. (1894). The Royal Natural History: Mammals. Frederick Wayne and Co: London. Available.

Nelson, M. E. and Madsen, J. H. (1983). A Giant Short-Faced Bear (Arctodus simus) from the Pleistocene of Northern Utah. Transactions of the Kansas Academy of Science 86(1), 1-9.

The Incredible Size Variation of the Marine Iguana

No marine iguana (Amblyrhynchus cristatus) article would be complete without Charles Darwin's famous defamations against the reptiles, calling them "hideous", "disgusting clumsy Lizards", "imps of darkness"*, "stupid", and so forth (see his Journal of Researches). Despite these harsh sentiments, Darwin did not disown the reptiles during his visit, but made lasting observations on their biology. The laterally flattened tail and webbed feet are adaptations for a semi-aquatic habitat, one specimen demonstrated that the iguanas could survive being submerged for at least an hour; the strong claws of equal length are "admirably adapted" for grasping on to rocks**; instead of consuming fish (as some suspected earlier), the enlarged intestines and stomach contents suggested a diet wholly composed of marine algae; Darwin also suspected that they lacked land predators*** by repeatedly throwing an individual into a pool, only for it to continuously return to land! In The Voyage of the Beagle he observed that the iguana population at Albemarle Island was significantly larger than those on other islands; this remarkable variation is occasionally mentioned in marine iguana publications, but its significance is rarely discussed - hence this post.

* For some reason, the quote is rendered "I call them 'imps of darkness'..." or "someone calls..." in different publications.
** Darwin observed this function on the coast, but he apparently did not consider its function in marine browsing. It also seems unusual that he did not observe specimens consuming algae exposed by a low tide.

*** Galapagos Hawks have been known to hunt iguanas in groups and can take adult females (on Santa Fe the iguanas have compensated by using mockingbirds as sentinels); Great Blue Herons are major predators of hatchlings (Romero and Wikelski 2009). However, some island populations of marine iguanas are virtually not subjected to predation (see below). These days feral cats and dogs are causing trouble since marine iguanas have no way of recognizing these terrestrial predators as a threat (Romero and Wikelski 2009). 

"Hideous?" I'd think "ruggedly handsome" would be a more apt description. Darwin described the iguanas as being "dirty black" (being dark aids in their thermoregulation), but as seen in this and other specimens, their coloration is actually highly variable. Also, what's with so many 19th century naturalists talking about reptiles in such disparaging terms?

Photo taken (and modified) from the Wikipedia Commons.

Before we get to the issue of size, some more background on the marine iguana is in order. Darwin considered the Galapagos land iguanas to be a second species within Amblyrhynchus; the land iguanas are now considered to be three species within Conolophus but molecular evidence has confirmed that they form the sister clade to the marine iguana (Gentile et al. 2009, Wiens and Hollingsworth 2000). Interestingly, the Galapagos iguanas appear to have diverged less than 10 million years ago, before the origin of the modern islands and implying that they inhabited other, now-submerged, islands in the vicinity (Rassmann et al. 1997). The (Amblyrhynchus + Conolophus) clade was formerly assumed to be related to chuckwallas (possibly due to long branch attraction and convergence), but now it is thought that they form a clade with spinytail iguanas - all of these clades occur around the central part of the Americas. (Wiens and Hollingsworth 2000). The MarineBio website has a fine summary of marine iguana biology - although their size figure could stand to use some revision.

A marine iguana goes for a swim - they locomote with their tails and hold their appendages flat against their body. Taken and modified from the Wikipedia Commons.

Wikipedia correctly mentions that the smallest iguanas are from Genovesa and the largest are from Fernandina and Isabela, although bizarrely the next paragraph simply states that males are 1.3 m long, females are 0.6 m in length, and the males weigh up to 1.5 kg (~3.3 lbs). Darwin's Journal of Researches mentions that specimens can reach 4 feet (1.2 m) in length and he gives a weight of 20 pounds (9 kg) for one large specimen. Romero and Wikelski (2009) comment that the Genovesa males are typically only 0.5 kg (~1 pound - about 0.9 kg/2 lbs max) in weight while the largest on Isabela can be over 10 kg. A photograph published by the authors (which I probably can't reproduce) shows an enormous 12 kg (26 pound) male with a very light coloration and huge amounts of tissue associated with the dorsal crest. I'm baffled as to how most popular sources have a maximum mass which is off by a factor of 8 - fortunately peer-reviewed sources do not make this mistake!


Size is a fundamental characteristic for organisms as it influences their morphology, physiology, behavior, and life history (Wikelski 2005). However, there are numerous and often interrelated factors which influence body size, so it is difficult to determine how the trait evolved - fortunately for me, Wikelski (2005) is a review paper on this subject for marine iguanas. The evolution of body size appears to have occurred rapidly in different marine iguana populations; Rassmann et al. (1997) determined through mitochondrial DNA that the iguanas on Fernandina and Genovesa form a "northern clade" (i.e., in the northern islands of the archipelago) despite their body sizes at the opposite end of the spectrum. Selective pressure through predation can be a very strong force, but since some marine iguana populations have virtually no predation and males are subjected to negligible predation on every island, this factor can effectively be ruled out (Wikelski 2005). Like the case for most organisms, there is a correlation between the size of the landmass and that of the organism (the larger Galapagos islands are also subjected to increased upwelling), however body size has historically increased on every island, apparently due to increasing temperatures (Wikelski 2005). While large males would seem to have a lot going for them - they have thermal inertia (useful for diving deeper than competitors), an increased ability to cling to rocks, and sexual preference from females (due to their ability to establish display areas) - during El Nino years the upwelling stops and while the iguanas can shrink (in body length, not just mass) to ameliorate the famine conditions, females have a 70-80% survival rate and large males have a survival rate of a mere 20-50% (Wikelski 2005).

Wikelski (2005) concluded that the most important influences on male marine iguana body size are sexual selection for larger size from females and natural selection. The natural selection is not limited to the famine conditions caused by the El Nino phenomenon, but also temperature variation and the amount of biomass. While large iguanas have more thermal inertia, they heat up more slowly which limits their ability to dive and digest; the amount of algae biomass does indeed appear to be influenced by the size of islands (Wikelski 2005). Wikelski (2005) theorized that the reason for large size, not just in iguanas but possibly many animals, is due to sexual selection which is of course countered by natural pressures mostly relating to the supply (and for some animals, physical size) of the food source. As for why sexual dimorphism occurs, this may be related to the resources females need to allocate towards reproducing - quantitative tests of this idea, however, have yet to be carried out (Wikelski 2005).

In the four years since Wikelski (2005), it does not appear that anyone has further elaborated upon the mechanisms controlling marine iguana body size. For those writing or revising articles on the species, please cease from implying that marine iguanas are homogeneous in size and at least mention the incredible variation!

A pretty good video from the BBC. As Wikelski (2005) speculates, when the iguanas first arrived on the Galapagos there would have been very limited food on land, forcing them to forage for intertidal algae. The North Seymour population supplements their diet with land plants, so presumably the land iguana species is derived from a marine population which specialized even further.

References:

Gentile, Gabriele, et al. (2009). An overlooked pink species of land iguana in the Galápagos. PNAS 106, 507-511. Available.

Rassmann, K., et al. (1997). The microevolution of the Galápagos marine iguana Amblyrhynchus cristatus assessed by nuclear and mitochondrial genetic analyses. Mol. Ecol. 6, 437–452.

Romero, L. Michael and Wikelski, Martin. Marine Iguanas, Life on the Edge. IN: Galápagos, Preserving Darwin's Legacy. Edited by Roy, Tui De. Firefly Books, 2009.

Wiens, John J., and Hollingsworth, Bradford D. 2000. War of the Iguanas: Conflicting Molecular and Morphological Phylogenies and Long-Branch Attraction in Iguanid Lizards. Syst. Biol. 49, 143–159. Available.

Wikelski, Martin. 2005. Evolution of body size in Galapagos marine iguanas. Proc. R. Soc. B. 272, 1985-1993. Available.