On the Importance of Vultures

Torgos - of no relation to Manos. Taken from here.

Our anthropocentric stigma against scavengers is totally underserved and in fact, carrion consumption is a valuable ecological "service". The word "scavenger" is used fast and loose in popular parlance but the label should be restricted to animals which depend heavily on carrion; just about every vertebrate which can consume meat (including many "herbivores") won't hesitate to snack on a corpse here and there - even humans. The three independent lineages of vultures have specialized for locating and feeding on carrion and utilize the resource to the degree that they can be known as "obligate scavengers" - although it should be noted that it is not their sole food source.

Just to get the word out, nothing said in this article applies to the so-called "Palm-nut vulture" Gypohierax angolensis which is specialized for eating palm nuts (!) and feeds on fish (!!), live prey, and then carrion to a lesser extent (Mundy et al. 1992). Gypohierax is closely related to the gypaetine vultures (both fairly aberrant)... but also Polyboroides and Eutriorchis (Griffiths et al. 2007, Lerner and Mindell 2005). Oh, and the whole "New World"/"Old World" schism is a false dichotomy as these vultures didn't pay attention to those biogeographical rules earlier in their evolution. Anyways, back to the post:

Carrion is an ephemeral and unpredictable resource so it is no surprise that the vertebrates which depend on it the most can fly. Vultures all have large wingspans and locomote by soaring flight (Ruxton and Houston 2004); their stomach acid has a very low pH (1) and is apparently capable of resisting/detoxifying bacteria (Sekercioglu 2006); bald heads and necks don't correlate well with messy feeding habits (contra Mundy et al. 1992) but function along with postural changes as a thermoregulatory mechanism vital to these birds which may deal with rapidly-changing temperatures ranging from <0>70 °C (due to altitude) (Ward et al. 2008). Hertel (1995) outlined the morphological traits shared by these lineages: the long, narrow, shallow, and highly curved maxilla is designed for hooking or slicing large chunks of meat (comparable in function to a meathook); the deep ramus is an adaptation for dorsoventral forces correlated with rapid consumption; there is a large angle between the foramen magnum and basicranium reflecting the strait line of pulling force of the head and neck (avivores, in comparison, have an angle approaching 90 degrees); the narrow ramus and shallow mandibular symphysis indicate a lack of resistance to struggling prey; the occipital distance is greater and orbits are smaller (scavengers are less dependant on eyesight, apparently).

First: Accipiter cooperi - modified from here. This species is a functional avivore and contrasts strongly in form and function with the scavenger lineages. Hertel (1995) compared them to staplers or churchkey can openers function-wise.

Second: Neophron percnopterus - modified from here. A member of the gypaetine vulture lineage(s?). Skull indices of this species and one of its extinct North American relatives (Neophrontops americanus) are well into the "scavenger" ecomorph range despite the extant species taking a broad range of food in addition to carrion (Hertel 1995, Mundy et al. 1992).

Third: Gyps tenuirostris - modified from here. An aegypiine vulture - of all the 13 species in this lineage the 8 Gyps are the most specialized for scavenging (Mundy et al. 1992).

Fourth: Coragyps atratus - modified from here. A member of the cathartid lineage; they're distant relatives of the other vulture lineages but it isn't clear to what degree.

Although functionally similar, there are distinct lineages of gypaetine, aegypiine, and cathartid vultures. The birds which can be called gypaetine vultures are abarrent scavengers; Gypaetus barbatus feeds mostly on bone marrow (it appears to retain vulture-like skull indices despite this); Neophron percnopterus keeps a low profile at large mammal carcasses, is an important small animal scavenger/predator, feeds on eggs, and also consumes fecal matter (preferring carnivore and... human) (Mundy et al 1992). The gypaetine vultures are more basal in the order Falconiformes/Accipitriformes and appear to be allied to the pernine kites; the more familiar aegypiine vultures are more derived and have been recovered in a position somewhere near some of the serpent eagles (long story - see Griffiths et al. 2007 and Lerner and Mindell 2005). Cathartids are, well, certainly not storks and are either basal member of Falconiformes/Accipitriformes (also a long story) or a distinct (ordinal-level?) clade located nearby in a huge mess (see Livezey and Zusi (2007) & Hackett et al. (2008) for the former placement - Morgan-Richards et al. (2008) (and similar mtDNA studies it cites) for the latter).

I think we have been sufficiently introduced to vultures.

So just why is scavenging important? It isn't just some biological curiosity - most animals die from causes unrelated to predation and most of their biomass is consumed by vertebrates (and not microbes and invertebrates) (Devault et al. 2003). Turkey vultures (Cathartes aura) were observed to scavenge every experimentally placed carcass (which wasn't badly decomposed) in a forested environment within three days and vultures on the Serengeti have been observed to consume most of the large, conspicuous carcasses (Devault et al. 2003 - citing Houston 1979, 1986, 1988). So forget the image of vultures cleaning up after lions on the savannah - they consume staggering amounts of biomass from carcasses the size of mice to elephants in temperate and tropical environments worldwide (except Australia...).

It is unfortunate that the loss of Gyps vultures in South Asia due to diclofenac poisoning has demonstrated just how important they were in the ecosystem. The near-extinction of the vultures caused an explosion in the feral dog and rat population and the potential for disease could impact domestic animals and humans (Pain et al. 2003, Prakash et al. 2005). Interestingly, while the importance of facultative scavengers cannot be overstated, these scavengers (such as crows, gulls, starlings) lack the ability to deal with pathogens present in vultures and are more prone to spreading them (Blanco et al. 2006).

Although it appears that vultures are important ecosystem players, facultative scavengers seem to get the job done without them in boreal areas, Australia, and some islands. Perhaps areas with relatively low terrestrial production simply can't support the needs of obligate scavengers and the more generalized species wholly exclude them. The fossil record before the K/T event does not appear to show a community of vulture analogues as none of the pterosaurs and basal birds (that I'm aware of!) show the characteristic skull indices outlined by Hertel (1995) - so presumably a wide variety of facultative scavengers can cover for vultures even in areas with high production. Whatever was going on, in a good portion of our world today vultures are vital parts of the ecosystem and their worldwide decline could be disastrous for a number of as-yet unseen reasons.

Obligate scavengers will even eat facultative scavengers.

Photo taken from here.

References:

Blanco et al. 2006. Faecal bacteria associated with different diets of wintering red kites: influence of livestock carcass dumps in microflora alteration and pathogen acquisition. J. Appl. Ecol. 43, 990–999.

DeVault, Travis L. et al. 2003. Scavenging by vertebrates: behavioral, ecological, and evolutionary perspectives on an important energy transfer pathway in terrestrial ecosystems. Oikos 102, 225-234

Hertel, Fritz. 1995. Ecomorphological Indicators of Feeding Behavior in Recent and Fossil Raptors. The Auk 112, 890-903.

Griffiths, Carole S. et al. 2007. Phylogeny, diversity, and classification of the Accipitridae based on DNA sequences of the RAG-1 exon. J. Avon. Biol. 38, 587-602

Hackett, Shannon J. et al. 2008. A Phylogenomic study of Birds Reveals Their Evolutionary History. Science 320, 1763-1768.

Lerner, H. R. L. and Mindell, D. P. 2005. Phylogeny of eagles, Old World vultures, and other Accipitridae based on nuclear and mitochondrial DNA. Mol. Phyl. Evol. 37, 327-346

Livezy, Bradley C. and Zusi, Richard L. 2007. Higher-order phylogeny of modern birds (Theropoda, Aves: Neornithes) based on comparative anatomy. II. Analysis and discussion. Zool. J. Linn. Soc. 149, 1-95

Morgan-Richards, Mary et al. 2008. Bird evolution: testing the Metaves clade with six new mitochondrial genomes. BMC Evolutionary Biology 8

Mundy, Peter et al. 1992. The Vulture of Africa. Academic Press

Pain, D. et al. 2003. Causes and effects of temporospatial declines of Gyps vultures. Asia. Cons. Biol. 17, 661–671.

Prakash, V. et al. 2005. Catastrophic collapse of Indian white-backed Gyps bengalensis and long-billed Gyps indicus vulture populations. Biol. Cons. 109, 381–390.

Ruxton, Graeme D. and Houston, David C. 2004. Obligate vertebrate scavengers must be large soaring fliers. Journal of Theoretical Biology 228, 431-436

Sekercioglu, Cagan H. 2006. Increasing awareness of avian ecological functions. TRENDS in Ecology and Evolution 21, 464-471

Ward, Jennifer et al. 2008. Why do vultures have bald heads? The role of postural adjustment and bare skin areas in thermoregulation. Journal of Thermal Biology 33, 168-173.

Whelan, Christopher J. et al. 2008. Ecosystem services provided by birds. Annals of the New York Academy of Sciences 1134, 25-60

Captain Hanna's Mystery Fish

In the spirit of this recent post, I'll attempt to critically re-analyze an alleged "sea serpent' carcass reported from New Harbor, Bristol, Maine. I believe that a plausible candidate has been overlooked by prior analyses, but of course I'll have to critically examine the possibilities lest I fall victim to Phylogenetic Roulette!


As detailed in the Bulletin of the U.S. Fish Commission, at some point in August 1880 one Captain S. W. Hanna caught a dead "young sea-serpent", badly tearing up his net in the process. Hanna thought he would have lost a considerable amount of money (~ $480 in 2008 dollars) by towing it to shore and let the carcass be. Fortunately he did make a sketch of the 24-25 foot (~7.5 m) fish later in the next month:


What immediately strikes me about the illustration is the placement of the dorsal fin directly behind the head and the subsequent superficial resemblance to elongated members of the actinopterygian order Lampriformes such as Lophotidae, Radiicephalidae, and Regalecidae. Of all these species, only Regalecus glesne can reach 7.6 meters; citations give a maximum of an incredible 11 meters and there is strong documentation of them at least reaching 9 meters. I'd highly recommend clicking on the last hyperlink - wow.

Wood (1982) mentions that circa 1885, a 25 foot/7.6 m oarfish weighing 600 lbs/272 kg was caught by fishermen off Pemaquid Point, Maine. There is no such town as "Pemaquid Point" in Maine - but that landmark is a portion of New Harbor which itself is a village within Bristol. It is very frustrating that Wood (1982) does not provide a direct citation for this account - the "circa 1885" certainly needs to be explained as does the possibility that people other than Hanna may have examined the carcass. The "circa 1885" implies that this is not an interpretation of the case as outlined by Hanna (1883) and the fact that it wasn't mentioned by Hanna could imply that there was a coincidental, second case involved. Such a coincidence seems rather improbable and it could be possible that Hanna was unaware of either the case or the synonymy with his own case.

To make matters even more confusing, Kendall (1914) states Chlamydoselachus anguineus or frilled sharks have occured in New Harbor and Pemaquid [sic] Maine, citing Hanna (1883) and Goode and Beane (1896)! It seems exceedingly odd that they didn't realize the locale synonymy. Anyways, Goode and Beane (1896) state that Hanna's description "might correspond very closely" (?) with a frilled shark and sea serpent stories; despite including an extensive discussion of frilled shark morphology there is absolutely no discussion for their reasoning. While the authors use confusing tenses ("At this time it was suggested") they only cite Hanna (1883) and appear to be the originators of the strongly suggested and poorly supported identification.

Heuvelmans does not cite Goode and Beane (1896), Kendall (1914), or any accounts other than Hanna (1883) yet also suggests that the Captain Hanna/New Harbor/Pemaquid "sea serpent" is either a frilled shark or a relative of some sort. This has proven to be the most popular identification and it has been echoed by Bright (1968) and by Shuker (cited by Roesch 1997). The popularity of this identification is baffling - Roesch (1997) points out that Hanna's description is hardly diagnostic of a shark and the only argument put forth by Heuvelmans and Shuker for the shark identification are the apparent multiple "gill slits". Roesch (1997) considers the possibility of artistic license, but Hanna (1883) (which he didn't appear to have access to) specifically states that the "three strokes" on the "neck" are "corresponding with those of the shark". Of course there are no known sharks with only three gill slits; none have less than five and frilled sharks have six - and they're distinctive enough to inspire the common name. Roesch (1997) suggests that Hanna could have been mistaken about operculum morphology; members of the lampriform family Lophotidae have operculums which can create the impression of three "gill slits" and I'd suggest that this could be an interpretation for the family Regalecidae as well.

Roesch (1997) puts forth several lines of evidence which convincingly suggest that the Hanna (1883) account describes a bony fish and not a shark; given the lack of availability for his paper (and anything published in The Cryptozoological Review) his points are worth summarizing here. The illustration and account clearly refer to pectoral fins with readily visible rays ("not stiff pointed fins like the shark... more like the side-fins of the cod or sun-fish") - a diagnostic trait for a member of Actinopterygii. The pectoral fin placement at the side of the body and not sloping down is also more characteristic of a ray-finned fish than a shark. The comparison of the dorsal fin to that of the cod also supports the notion that lepidotrichia are present and an anguilliform-like caudal region is also drawn with fin rays. Roesch notes that no sharks have such an area of continuous fins "like those of an eel" and this should be readily observed even on something like the frilled shark.

Roesch (1997) concludes that the Hanna fish is more likely a bony fish than a shark and concludes that it "quite likely represents a new species". I'm not so convinced and it seems odd to me that he didn't mention the only bony fish which appears to reach or exceed the reported size with some frequency. Could the Hanna fish have been Regalecus glesne? There are a number of statements in Hanna (1883) which make this identification problematic: the body was described as round or nearly so (and 8-10" thick) instead of laterally flattened, none of the dramatic color was observed (it was slate gray dorsally to gray and white ventrally), the pelvic fins were not observed, an anguilliform anal fin was observed (oarfish lack anal fins), and "fine, briery teeth" were located at the "extreme end" of the head (oarfish lack teeth). On the plus size the mouth was described as small and like that of a sucker (which is an OK comparison to an oarfish) and the reference to very fine skin is consistent with the scaleless oarfish. It should be noted that since this fish was viewed when still in the water and possibly partially submerged (with the head most elevated?), some of the morphology and coloration was simply not observed - note this live specimen and the difficulty of observing the dorsal fin and the apparent dull coloration. Alternately and/or additionally some of the misinterpretations/misidentifications could be due to post-mortem damage to the specimen - possibly inflicted by the nets used to capture it. The teeth are still rather problematic, although I'll have to check to see if the oarfish has gill rakers which can potentially be confused for teeth - this could be why they were described as "briery". The presence of an anal fin would have to be the results of assumption on the part of Captain Hanna - it could have been an optical illusion of some sort.


The notion of an oarfish-sized species remaining undescribed is not totally outside the realm of possibility, although the Hanna carcass does not demonstrate this convincingly. The reference to an identically-sized oarfish from the same location and roughly the same time is incredibly suspicious, as is the roughly similar morphology reported. Although the oarfish has become something of a cliche for "sea serpent" candidates, I think the evidence does lean towards such an identification regardless of some of the weird morphology described by Hanna. Further investigation into the case described by Wood could theoretically prove this hypothesis.


I've got to concentrate on little fish for the time being, but I hope to write more extensive posts about oarfish and frilled sharks at some point in the near future.



References:

Bright, Michel. 1989. There are Giants in the Sea. Robson, London.

Hanna, S. W. 1883. Description of an Eel-like Creature Taken in a Net at New Harbor, Maine, in 1880. Bull. U.S. Fish. Commn. 3, 407.

Heuvelmans, Bernard. 1968. In the Wake of the Sea-Serpents. Hill and Wang, New York.

Goode, George Brown and Bean, Tarleton H. 1895. Oceanic Ichthyology, a treatise on the deep-sea and pelagic fishes of the world. Available (Caution ~50 mb!)

Kendall, William Converse. 1914. Proceedings of the Portland Society of Natural History III, 1-198. Available

Roesch, Ben S. 1997. A Review of Alleged Sea Serpent Carcasses Worldwide (Part One --- 1648-1880) The Cryptozoological Review 2, 6-27

Wood, Gerald.1982. The Guinness Book of Animal Facts and Feats. Guinness Superlatives, Middlesex.

Change has come to The Lord Geekington

As you may have noticed, the banner has undergone something of an art evolution. Since I drew the old banner last year I've taken an art class and wow, what a difference it has made! I would love to take more, but now that I have a hypothetical B.S. Biology degree this may prove difficult. We'll see how it evolves next year.

So who's on it?

Discussed here, this is a damaged cat skull (note the missing upper right canine) which I dug up in the woods near my house. The odd characters (sagittal crest, closed postorbital bars) may be related to large size; while I can't rule out an exotic hybrid, this is probably within the range of variation for house cats. I certainly won't let myself fall prey to phylogenetic roulette!


The last thoracic vertebrae and first two dorsal vertebrae from Basilosaurus cetoides, an Eocene stem-cetacean. As I discussed here, the vertebral count from a smaller relative suggests that B. cetoides was even larger and more ridiculously elongated than previously imagined. I'd love to see how these big, extreme vertebrae worked.


Mesoplodon densirostris - I've written quite a lot of posts about beaked whales so a representative is obligatory.

The start of my lazy bird silhouette series, this is a generalized frigatebird (Fregata sp.). They're incredible fliers and I would love to see them in real life.

Turkey vultures (Cathartes aura) are ubiquitous but amazing animals none the less. I saw one getting mobbed the other day and they're capable of some incredibly spry moves for animals that spend most of their time soaring. I've written about cathartids numerous times.

The cirroctopod Opisthoteuthis is the closest an organism has come to resembling a plush animal. They're frequently mentioned in my numerous cephalopod posts. I can't talk about the fish, just some poeciliid of no consequence.


No, it isn't an exogorth, this is an amphibian known as a caecilian. They're the most poorly known major tetrapod clade and their relation to other lissamphibians still seems up for debate. The structure located between the rudimentary eye and the nostril is a sensory tentacle. I have yet to seriously discuss them.


Softshell turtles (Trionychidae) are highly derived cryptodires which traded in a bulky carapace for their titular comparably strong and flexible shell. I've mentioned them here.

Wow, no references. I'll have to make up for that...

Phylogenetic Roulette for Identifying Cryptids

First off, Matt Wedel/Dr. Vector is to blame credit for coining the titular terminology in the comments of this Tet Zoo post. I feel obliged to remind everyone to Measure Your Damn Dinosaur (MYDD) and read Sauropod Vertebra Picture of the Week (SV-POW!).

It is difficult to have an opinion about cryptozoology which isn't alienating. Just acknowledging the topic is probably viewed as unintellectual and naive in the eyes of most zoologists and critically examining cryptids seems overly-intellectual and cynical in the eyes of many crypto-enthusiasts. As Darren Naish has demonstrated, macrofauna is still being discovered regularly and new species can be discovered by methods which basically amount to cryptozoology. The problem is that cryptozoologists/crypto-enthusiasts either seem unaware of these discoveries or apathetic of them and focus almost entirely on "mega monsters" which cannot (or no longer) be viewed as serious candidates for discovery. Cryptozoology doesn't just have to be another pseudoscience chasing myths and I think shifting focus to recently discovered and probable megafauna would be a real service to science.

Okay, so while this probably isn't going to happen there is still one aspect of cryptozoology which can be easily fixed - basic education about parsimony. Since there are no type specimens and evidence is often unclear, proposals of cryptid identity run the gamut from ill-supported to non sequitur. Here's a little case study:

Long story short, the Daedalus reported an unknown marine animal between St. Helena and the Cape of Good Hope on October 4, 1848; the "enormous serpent" showed an estimated 60 feet (18.3 m) of length above the surface, the diameter was estimated at 15-16 inches (~0.4 m) behind the head, the head and "shoulders" were held 4 feet (1.2 m) out of the water, a "mane" or "fin" was present on the back, it was estimated to be moving at 12 to 15 miles per hour (19-24 km/h) despite demonstrating no undulations in any plane (Heuvelmans 1968). Although the above illustration was purportedly accurate, the scale of the "serpent" is clearly quite off and it was apparently 200 yards (~180 m) away at its closest.

So what was made of this surprisingly high profile case? Sir Richard Owen treated the questionable illustration like a photograph and concluded that the head shape and reference to a mane indicated a mammal and proposed that it was a Southern Elephant Seal (Miroungna leonina)*. Cryptozoologists often take reported sizes far too seriously and it would not be surprising for even experienced mariners to inflate an unfamiliar 5-6 m pinniped into a ~18 m monster taking the wake and lack of scale into account. Owen's case runs into trouble since male elephant seals are typically on rookeries at that time of the year, they lack any remotely mane-like structure**, their profile should be instantly recognizable***, they most certainly do not have a stiff body as Owen claims, the reported locomotion sounds very unlikely for a phocid, and the captain of the Daedalus reaffirmed that the head he saw was flat****. Since there aren't many other large animals in the area which can swim with their heads above water, Owen was right to consider elephant seals as a candidate for the Daedalus sighting; however the lack of other candidates considered, his adamant support despite numerous confounding factors, and the fact that he apparently recently saw a juvenile in captivity leads me to think that this was a mild case of Phylogenetic Roulette.

* Despite the fact that he proposes Phoca proboscidea, Phoca leonina, and "Anson's sea lion" as candidates, these all appear to be synonyms for M. leonina (King and Bryden 1992). His letter can be read here, page 280 or so.

**If the animal was in poor condition, its protruding spine could theoretically form a "crest" of sorts. Owen implied that his hypothetical elephant seal was in poor condition because he erroneously thought they couldn't spend more than a day at sea - they can stay at sea for months.
*** This could be hand-waved if the hypothetical seal was immature. The reported overbite could possibly be taken as evidence for a developing proboscis.

**** Heuvelmans gives the illustrations more credibility and concludes that the animal may have been an unknown species of plesiosaur-like pinniped. Despite claiming the opposite, Heuvelmans could be a painfully biased pigeonholer.

While Owen had at least some reasoning for selecting an elephant seal as a candidate, Heuvelmans mentions a severe case of Phylogenetic Roulette: one anonymous correspondent suggested the eel-like fishes (or highly derived true eels) Saccopharynx flagellum or "Ophiognathus" ampullaceus (now Saccopharynx ampullaceus) as candidates. Heuvelmans summarizes this very well:

[the] suggestion... might seem very learned to the common reader until he discovers that these impressive Latin names refer to two closely related abyssal fish, eel-like in shape, but with vast mouths capable of swallowing four times their own weight, and never, so far as we know, exceeding 6 feet in length. The suggestions must have come from an amateur impressed by the strangeness of these fish rather than an experienced zoologist, for they could never be mistaken for the Daedalus sea-serpent.

This lands squarely on the non sequitur side of the spectrum. Of all the lineages of elongated or serpentine oceanic organisms, what could possibly set gulper eels apart from the hundreds of other candidates? It boggles the mind how fish with morphology so completely at odds with what was reported could even be selected as candidates, yet this happens all the time in cryptozoology.

Daedalus cryptid - giant squid! A cryptid in Lake Champlain - derived Tanystropheus! A carcass from the stomach of a sperm whale - extant Sauropterygian! Raccoon carcass - sea turtle without a shell (sic)! Who knows how many thousands of half-baked identifications have been proposed on cryptozoology forums - is there some wheel of big, bizarre animals that these people spin whenever a report or ambiguous carcass crops up? Making an identification from the general shape of a reported cryptid is far from scientific - you need specific morphological characters like those kindly put up on the Palaeos page to establish an objective case. Phylogenetic Roulette probably stems in part from our brains being hardwired to see patterns and answers with limited data; while this can be useful in real life things can be much more ambiguous, there are few easy answers. I'd hold up Paxton et al. (2005) as an objective and ideal analysis of a purported cryptid report, hopefully more like it will follow.


There is no way to stop quackery and most dumb suggestions, but if done properly I'd say cryptozoology does show some promise.

References:

Heuvelmans, Bernard. 1968. In the Wake of the Sea-Serpents. Hill and Wang, New York.

King, J. K. and Bryden, M. M. 1992. Mirounga leonina. Mammalian Species 391, 1-8

Paxton, C. G. M. et al. 2005. Cetaceans, sex and sea serpents: an analysis of the Egede accounts of a “most dreadful monster” seen off the coast of Greenland in 1734. Archives of natural history 32, 1-9

Attempted Pangolin Identification

Finishing up my undergrad education is proving to be more time intensive than I was expecting, partially thanks to tiny fish and giant boots. Rather than posting nothing for the next three weeks, I figured I'll try my hand at (i.e. rip off) a Naish-esque "picture of the day"-type post.

I've had my eye on this preserved pangolin for a couple years now and last week an open lab finally gave me the opportunity to photograph this pholidotan. I didn't realize how much the lighting sucked in the room, but it was sufficient for the purposes of this post. Although occasionally confused for reptiles and formerly allied with xenarthrans (armadillos, anteaters, sloths), molecular evidence strongly supports a Pholidota + Carnivora clade (= Ferae) within Pegasoferae (bats, horses, dogs cats) which is in turn within Laurasiatheria (cows, whales, shrews, hedgehogs) (Nishihara et al. 2006, also citing Madsen et al. 2001, Murphy et al. 2001, Waddell et al. 2001, Amrine-Madsen et al. 2003). Kjer and Honeycutt (2007) used mitochondrial DNA to come up with a different topology featuring Pholidota in the middle of Laurasiatheria, but note that they did not correct for potentially inflated Bayesian posterior probabilities. Fossil evidence suggests that pangolins are a member of the order "Cimolesta" (probably an unnatural group) along with Pantodonta, Taeniodonta, et cetera (Boyer and Georgi 2007). It's a good question as to how all of this fits together, although since I once tried (and failed) to write about it, I'll leave it as is...


There are eight extant species of pangolin which most sources unfortunately lump into the genus Manis. Gaudin and Wible (1999) proposed that the Asian pangolins could be placed in Manis, the arboreal African species in Phataginus, and the terrestrial African species in Smutsia; this was based off of endotympanics and the authors suggested more characters and more extensive analysis before any taxonomic pronouncements were to be made. Botha and Gaudin (2007) note that such a study has not yet been done, but to make classifications easier in this post I'm just going to pretend that the proposed subgenera are actual genera. As David Marjanović will tell you at the Tet Zoo comments, there isn't an established definition for what a "genus" entails, so I figured I'd just call them something useful from a systematic standpoint. That and attempt to be cutting edge.




So anyways, what species is this pangolin? The tail appears to be as long or slightly shorter than the body, thus Phataginus tricuspis and Uromanis tetradactyla can be ruled out immediately. Although this looks like a heavily built animal, the 8.5 by 11 inch paper indicates a head and body length of 13-14 inches (33-36 cm), considerably smaller than Smutsia temminckii (females are 45-47 cm, males 49-55 cm) and the even larger S. gigantea (Heath 1992). Additionally the scales seem too small proportionally to be from a Smutsia and as far as I can tell that genus lacks hairs in between the scales. It's worth mentioning that the scales of pangolin are fused hairs, which makes it all the more remarkable that they can take up 1/4 to 1/3 of the body weight (Heath 1992).




The review of Paramanis culionensis and P. javanica morphology by Gaubert and Antunes (2005) notes that diagnostic characters for these species are 19-21 total scale rows and 15-18 scale rows (respectively); I counted at least 21 for the mount. Even though the authors illustrate the scales from the head and scapular region of the Paramanis species in dorsal view, it is quite clear that they do not resemble the scale shape from the mount at all.



So this just leaves the species which are definitely in the genus Manis, the Indian pangolin M. crassicaudata and the Chinese pangolin M. pentadactyla. I'm going to say that the robust body, thick tail, and scale shape are all suggestive of M. crassicaudata - although I can't be completely certain that this is within the morphological variation of M. pentadactyla. If there is anybody out there familiar with the morphology of these species, please, clue me in!



Alright, back to work.



References:

Botha, Jennifer and Gaudin, Timothy. 2007. An early Pliocene pangolin (Mammalia; Pholidota) from Langebaanweg, South Africa. Journal of Vertebrate Paleontology 27, 484–491

Boyer, Doug M. and Georgi, Justin A. 2 007. Cranial Morphology of a Pantolestid Eutherian Mammal from the Eocene Bridger Formation, Wyoming, USA: Implications for Relationships and Habitat. J Mammal Evol 14, 239–280

Gaubert, Phillipe and Antunes, Agostinho. 2005. Assessing the taxonomic status of the Palawan pangolin Manis culionensis (Pholidota) using discrete morphological characters. Journal of Mammalogy 86, 1068-1074.

Gaudin, Timothy J. and Wible, John R. 1999. The Entotympanic of Pangolins and the Phylogeny of the Pholidota (Mammalia). Journal of Mammalian Evolution 6, 39-65

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

Kjer, Karl M. and Honeycutt, Rodney L. 2007. Site specific rates of mitochondrial genomes and the phylogeny of eutheria. BMC Evolutionary Biology 7

Nishihara, Hidenori et al. 2006. Pegasoferae, an unexpected mammalian clade revealed by tracking ancient retroposon insertions. PNAS 103, 9929-9934

The Ecomorphology of Arctodus

The enormous crown-group bear Arctodus simus is no stranger to this blog, I last covered it a couple years ago, but thanks to a new publication I feel obliged to give it another go. Other motivations include my guilt about letting that prior post get so bloated with topics and my annoyance with the portrayal of this animal in the media… so here we are!

Large and potentially fearsome animals are often subject to “Godzillafication” in popular culture and Arctodus simus is no exception. One of the more egregious offenders in recent memory is the oddly named show Jurassic Fight Club which claims that the bear is 11.5 feet tall (3.5 m), twice as big as extant bears at up to 2500 pounds (1134 kg), and capable of running at 45 miles per hour (72 km/h)! The “size charts” at that site are especially heinous and show a crudely rendered A. simus to have a shoulder height more typical for a proboscidean and its apparent nemesis Panthera atrox to be taller than most rhinoceroses. Illustrations by Mauricio Antón of both animals at a proper scale can be found here.

Size

There is no denying that Arctodus simus was an enormous animal, but claims that it weighed a metric tonne or more are baseless. Christiansen (1999) used limb bone dimensions to calculate that a large male A. simus would weigh between 700 to 800 kg (1540-1760 lbs) and speculated that on rare occasions males could have reached or exceeded one tonne. I think visual comparisons can be highly valuable when dealing with speculative body masses and a mockup of a large A. simus and large polar bears (here) suggest that the estimates made by Christiansen (1999) are indeed rather excessive. Sorkin (2006) questioned the use of limb bone dimension regressions against mass since A. simus has proportionally long and robust legs; estimates based on condylobasal skull length gave a maxima of 570 kg (~1250 lbs) for the species. Since A. simus has a rather short skull I can't help but wonder how accurate condylobasal skull length would be in predicting mass - it should be noted that A. simus also has a short body and this weight estimate does at least look more on the mark visually.

Emslie and Czaplewski (1985) suggested that A. simus, which they though had a maxima of 620-660 kg, may have been beyond the physical limitations of an active predator. I'm not a big fan of using maxima, but since the maximal weights of unambiguous hypercarnivorous predators have been calculated they are actually useful in this situation. Panthera atrox has been given a maxima of 420 kg (925 lbs) based on condylobasal skull length and Smilodon populator "almost certainly exceeded" 400 kg (880 lbs) based on limb bone analysis (Sorkin 2008 - data from Turner and Antón 1997, Christiansen and Harris 2005). Since A. simus did not seem to be greatly in excess of those cats, I don't think active hypercarnivory can be ruled out on that basis.

A Herbivorous Relative

Apomorphies such as a premasseteric fossa and a skull with a short, deep, and convex shape place Arctodus simus in the New World bear subfamily Tremarctinae, which includes the extant spectacled bear Tremarctos ornatus (Trajano and Ferrarezzi 1994). Arctodus and the exclusively South American Arctotherium are united as a clade of "short-faced bears" on the basis of wide molars and presumably other traits (a more foreshortened face?) (Trajano and Ferrarezzi 1994, Soibelzon et al. 2005). Arctodus simus shares its genus with the poorly known A. pristinus, which appears to be distinguished primarily by being smaller in size and appearing slightly earlier in the fossil record (Dalquest and Mooser 1980, Puckette 1976). The Great Bear Almanac claims that other apomorphies of A. pristinus include a "slightly shortened" face, large and high-crowned teeth, and very large canines.

Emslie and Czaplewski (1985) interpret the premasseteric fossa, typically found in large herbivores and small carnivores, as related to an enlarged zygomaticomandibularis muscle which allows for lateral grinding and jaw elevation. A seldom mentioned character is the enlarged radial sesamoid of tremarctine bears, which is apparently a plesiomorphic character shared with giant pandas (Salesa et al. 2006). Its use in Tremarctos ornatus isn't too clear, but it could be related to extensive food manipulation and/or a rather arboreal lifestyle for a bear (Salesa et al. 2006). Emslie and Czaplewski (1985) suggest that the elongated limbs of A. simus could be used to pull down vegetation and I think the retention of an enlarged radial sesamoid could tie in nicely with this hypothesis. Whatever its function, an enlarged radial sesamoid does not sound like a likely characteristic for an alleged cursory animal...

skeleton from Emslie and Czaplewski (1985). Note the less extreme limb proportions and the enlarged radial sesamoid bone.

Lots of Unlikely Characters for a Hypercarnivore

Some early Arctodus simus workers interpreted the bear as having an ecomorphology more similar to a felid than an ursid on the basis of a short and broad rostrum, large carnassial blades, long limbs, and a "possibly" more digitigrade stance (Christiansen 1999 - citing Kurten 1967 and Kurten & Anderson 1980). This hypothesis is the one that got stuck in the popular imagination (wonder why...) and still is despite the fact that Sorkin (2006) utterly demolished it. The sectorial carnassials, position of the mandibular condyle, and development of the angular process which were previously interpreted as evidence for hypercarnivory are all present in Tremarctos, a near-exclusive herbivore (Sorkin 2006). Buccal cusps on the upper molars of A. simus are shared with the largely herbivorous Kodiak bear (Ursus arctos middendorfi) (Sorkin 2006). Additionally, Sorkin (2006) noted that relatively short canines, small orbits directed somewhat laterally, reduced leverage of deltoid and pectoralis muscles (used to subdue prey), reduced development of the brachialis and brachioradialis muscles (used to grasp prey), reduced pronation of the forearm and the flexation of the wrist and digits (used to grasp prey), a short and bent olecranon process (reduction of ability to crouch), brown bear-like lumbar vertebrae with limited flexion in the sagittal plane (meaning slower acceleration and top speed) all indicate that A. simus was not an active predator.

Matheus (1995) suggested that carbon and nitrogen isotope evidence indicated that A. simus was highly carnivorous, but functioned primarily as a scavenger adapted for long distance walking/predator intimidation. The only known vertebrate obligate scavengers are large soaring fliers and while a large terrestrial scavenger is not energetically infeasible per se, the hypothetical niche could only have evolved in an environment without vultures (Ruxton and Houston 2004). Furthermore, the isotope range overlaps with Pleistocene brown bears (Ursus arctos) and it does not appear that a hypercarnivore and omnivore with a diet including terrestrial mammals can be distinguished from isotopes (Sorkin 2006).

Warp Analysis

One of the aforementioned inspirations for this post was another recent re-evaluation of A. simus morphology by Figueirido et al. (2009), which I can't believe I'm just getting around to now. Modern faunivorous bears, the insectivorous sloth bear Melursus ursinus and the carnivorous polar bear Ursus maritimus, have long and flat skulls with frontalized orbits, downwards directed zygomatic arches, a slender jaw with small movement arms for the temporalis and masseter muscles and poorly developed upper and lower tooth rows (Figueirido et al. 2009). The vastly different prey of the two bears and their apparent convergences would seem to suggest that if A. simus were hypercarnivorous, it would at least display some of these characters. Herbivorous bears, the spectacled bear and the giant panda, have a short jaw with large movement arms for the temporalis and masseter, a horizontal ramus deep at the level at the level of the third molar and shallow below the canines, well-developed cheek teeth, small canines, well-developed zygomatic arches, and lateralized orbits (Figueirido et al. 2009). Even though those are the two most basal bear species, the fossil record appears to indicate that they developed these traits independently rather than retained them (Figueirido et al. 2009). Arctodus simus does not group with either of these ecomorphs, but falls in the middle with generalized omnivorous ursid species (Figueirido et al. 2009). Sorkin (2006) reached a similar conclusion and thought the bear could be compared with the striped and brown hyenas (Hyena hyena and Hyena brunnea) and may have had a diet consisting of large animal carrion, small animal prey, and plant material. Figueirido et al. (2009) suggest an even more thorough ecomorphological study including other carnivorans should be done with A. simus, but conclude that it was likely an omnivore capable of dealing with with seasons and climactic cycles. Of course, even animals with a highly plastic diet aren't immune to extinction.

So that's about all I want to say about Arctodus simus - I have no idea why this post took to write as long as it did. There is little doubt that some less-enlightened members of the media will continue to erroneously portray this animal as a hypercarnivorous terror, but hopefully the alternate (and more parsimonious) suggestions will gain some attention.

References:

Carbone, Chris et al. 2007. The Costs of Carnivory. PLoS Biology. Available

Christiansen, Per and Harris, John M. 2005. Body size of Smilodon (Mammalia: Felidae). Journal of Morphology 266, 369-384

Christiansen, Per. 1999. What size were Arctodus simus and Ursus spelaeus (Carnivora; Ursidae)? Ann. Zool. Fennici 36, 93-102. Available

Dalquest, Walter W. and Mooser, O. 1980. Arctodus pristinus Leidy in the Pleistocene of Aguascalientes, Mexico. Journal of Mammalogy 61, 724-725.

Emslie, Steven D. and Czaplewski, Nicholas J. 1985. A new record of the giant short-faced bear, Arctodus simus, from western north America with a reevaluation of its paleobiology. Natural history museum of Los Angeles county contributions in science 371, 1-12.

Figueirido, B. et al. 2009. Ecomorphological correlates of craniodental variation in bears and paleobiological implications for extinct taxa: an approach based on geometric morphometrics. Journal of Zoology 277, 70-80.

Matheus, Paul E. Diet and Co-Ecology of Pleistocene Short-Faced Bears and Brown Bears in Eastern Beringia. Quaternary Research 44, 447-453

Puckette, William L. 1976. Notes on the Occurrence of the short-face bear (Arctodus) in Oklahoma. Proc. Okla. Acad. Sci. 56, 67-68

Ruxton, Graeme D. and Houston, David C. 2004. Obligate vertebrate scavengers must be large soaring fliers. Journal of Theoretical Biology 228, 431-436

Salesa, M. J. et al. 2006. Anatomy of the “false thumb” of Tremarctos ornatus (Carnivora, Ursidae, Tremarctinae): phylogenetic and functional implications. Estudios Geológicos 62, 389-394

Soibelzon, Leopoldo, H. et al. 2005. The fossil record of South American short-faced bears (Ursidae, Tremarctinae). Journal of South American Earth Sciences 20, 105-113.

Sorkin, Boris. 2008. A biomechanical constraint on body mass in terrestrial mammalian
predators. Lethaia 41, 333–347

Sorkin, Boris. 2006. Ecomorphology of the giant short-faced bears Agriotherium and Arctodus. Historical Biology 18, 1-20

Trajano, E. and Ferrarezzi, H. 1994. A fossil bear from Northeastern Brazil, with a phylogenetic analysis of the South American extinct Tremarctinae (Ursidae) Journal of Vertebrate Paleontology 14, 552-556

Giant Leptocephali

Elopomorpha is a diverse group of basal teleost orders united by a leaf-like larval form known as a leptocephalus; members include the tarpons and relatives (Elopiformes), bonefish (Albuliformes), halosaurs and spiny eels* (Notacanthiformes), true eels (Anguilliformes), and the gulper eels and relatives (Saccopharyngiformes) (Inoue et al. 2004). Inoue et al. (2004) finally corroborated the monophyly of Elopomorpha with character matrices and determined this phylogeny:

*Halosaurs and spiny eels have been placed in order Albuliformes by Inoue et al. (2004).

Fig. 5 from Inoue et al. (2004). Elops and Megalops are Elopiformes, Albula and Pterothrissus are members of Albulidae (bonefish), Aldrovandia and Notacanthus are members of Halosauridae and Notocanthidae, Gymnothorax through Anguilla are Anguilliformes, Saccopharynx and Eurpharynx are Saccopharyngiformes. Note that Albulidae and Anguilliformes are paraphyletic according to this phylogeny. The leptocephalus tail shape is important later on in this post.

Leptocephali are not normally very large, typically some 2-4 inches (50-100 mm) in length, so specimens substantially larger than this certainly raise eyebrows. The most commonly mentioned giant leptocephali were those collected by the Dana, the largest of which measured around 1800 mm (Castle 1959, citing Bertin 1954). Unfortunately, I have not found any information on these specimens aside from the length of the one individual and the number of myomeres (450*); their current whereabouts appear to be unknown. The ambiguity of this report has not stopped some cryptozoologists (e.g. Heuvelmans) from assuming that the larvae were true eels** with Anguilla-like growth (45 mm leptocephalus to a 800 mm adult) and a ~30 m adult size! Castle (1959) pointed out that Nemichthys scolopaceus has a larvae up to 253 mm in length and a growth rate which would turn a 1.8 m larvae into a 2.7-5.4 m adult. As we'll see, it's not entirely out of the question for the 1.8 m larvae to have an adult length shorter than that of the larvae.

*The number of myomeres apparently led Bertin to think that the larvae were members of Nemichthys (Castle 1959).

** Castle (1959) seems to synonymize "leptocephalid" with "eel larvae", so apparently he was unaware of the larval stage occuring in several other orders. Elopomorpha was established in 1966 on the basis of leptocephalus larvae (Inoue et al. 2004), and it seems improbable that four leptocephalus-adult relationships were worked out in 7 years. Heuvelmans, writing in 1968, certainly should have known.


Leptocephalus giganteus was first described by Castle (1959) on the basis of a 893 mm leptocephalus caught in shallow water off South Westland, New Zealand. The larvae was extremely attenuated with an 18.1 mm head, pre-vent length of 883 mm, depth of 18 mm, and 466-486 myomeres (Castle 1959). Castle (1959) suggests that characteristics such as the lack of fin rays, lack of cranial and pectoral development, V-shaped myomeres, and a subterminal vent indicate that this larvae is not a pathological giant and has not yet reached its full growth. He concluded that there's a giant bathypelagic eel living off the coast of New Zealand...

Another L. giganteus from S. Africa was described in 1967 and two more were reportedly found in an Alepisaurus* stomach, but it wasn't until Smith (1970) that an incredibly important feature was recognized. True eels never have pelvic fins at any of their life stages and sure enough, Smith (1970) noticed barely visible pelvic fins at the 34th myomere of his large individual. Coupled with the short-based dorsal fin, L. giganteus was recognized as a notacanthiform (Smith 1970). Interestingly, this excerpt from Early Stages of Fishes in the Western North Atlantic puts the maximum length of L. giganteus at 1840 mm (or 2 m), awfully close to the reported length of the largest 1930 Dana specimen. Are there reasons for thinking that the Dana specimens are L. giganteus aside from the length and myomere count (300-486 in L. giganteus, 450 in Dana)? Even more curiously, the book cites a source which suggests that L. giganteus may be a synonym for Notacanthus chemnitzi; are size and a widespread distribution the reasons for thinking this? I found a Moser and Charter (1996), but it did not have any unique information on L. giganteus...

*What's with all these fish having a suffix that means "lizard"?


Giant leptocephali appear to have been known since 1810 (from Rafinesque) and these unusual elongated larvae were eventually placed in the "genera"/categories Tilurus and "Tiluropsis"* by Roule (Smith 1970). While L. giganteus has an elongated head and round eyes, Tilurus can be distinguished by its short head and round eyes and "Tiluropsis" has a short head with vertically elongated eyes (Smith 1970). "Tiluropsis"-type larvae were recently captured in Brazilian waters, giving the authors an opportunity to discuss how prior workers tenuously connected the larvae to the halosaur Aldrovandia gracilis; the two have similar branchiostegal and pectoral ray counts and overlapping distributions, but the authors feel that much work is needed to clear up the life cycle of the enigmatic larvae. The book excerpt suggests that Tilurus belongs to the other notacanthiform subgroup, Notacanthidae.

* Tilurus has nomenclatural standing and "Tiluropsis" doesn't - somehow. Another type, "Tilurella" turned out to be a post-larval Nemichthys - it was distinguished by having elongated dorsal and anal fins, an anguilliform nasal organ, et cetera (Smith 1970).


With the advent of molecular data, if someone manages to get hold of giant leptocephalus and notacanthiform tissues they could theoretically resolve the mysteries surrounding the larvae. Do the larvae shrink in size at transformation? How many species compose each of the leptocephalus types? Do all notacanthiform larvae have this elongated shape? Although I'm somewhat doubtful that any of these will turn out to be a 30 m eel, it should still be a fascinating study nonetheless...



Reference:

Castle, P. H. J. 1959. A Large Leptocephalid (Teleosti, Apodes) from off South Westland, New Zealand. Transactions of the Royal Society Society of New Zealand 87, 179-184. Available

Figueroa, Daniel E. et al. 2007. The southernmost record of notacanthiform Tiluropsis leptocephali, with notes on possible species identity. JMBA2 - Biodiversity Records. Available

Inoue, Jun G. et al. 2004. Mitogenomic evidence for the monophyly of elopomorph fishes (Teleostei) and the evolutionary origin of the leptocephalus larvae. Molecular Phylogenetics and Evolution 32, 274-286.

Smith, David G. 1970. Notacanthiform Leptocephali in the Western North Atlantic. Copeia 1970, 1-9.