Weekly Spotlight (Mini Version): Pezosiren

4 09 2010

Good tidings and well-wishes! 

(NOTE: Due to my rough academic schedule, I’ve been forced to rely upon quotations and links far more heavily in this week’s spotlight than usual.) 

Although Ambulocetus, Rodhocetus, and their cetacean brethren may get all the media attention when it comes to exemplifying the evolution of aquatic amniotes, the sirenian fossil record has produced an equally fascinating parallel transition equipped with a number of amazing beasts of its own. Perhaps none, however, can exemplify the key components of this incredible journey from land to sea more effectively than Pezosiren portelli from the early Eocene of Jamaica. 

Pezosiren skeletal reconstruction

Pezosiren skull closeup.

Pezosiren is, to date, represented by a nearly complete skeleton (see above) unearthed during the nineties approximately 15 km south of Montego Bay alongside a number of fish, crocodylian, and rhinocerotoid specimens. The animal’s overall body shape has been informally compared to that of the famed Moeritherium. According to paenungulate experts Emmanuel Gheerbrant, Daryl P. Domning, and Pascal Tassy, 

“The basal sirenian morphotype, displayed by Pezosiren, comprises a long trunk (20 thoracic and 4 lumbar vertebrae) supported on relatively short legs… Four sacral vertebrae are present, with a firm sacroiliac articulation capable in most cases of supporting the body’s weight on dry land. However, in Pezosiren, these sacrals are no longer anklyosed in most cases, pointing to an incipient increase of flexibility of the sacral region for swimming by spinal undulation– a convergence with early whales that were comparable in their stage of evolution to Rodhocetus.  The tail was long and strong compared to that of most terrestrial ungulates, but the caudal vertebrae still lacked the enlarged transverse processes for the attachment of powerful tail muscles seen later in sirenians and cetaceans.”  

A) Partial right mandible, medial view, showing location of small mandibular foramen (white arrow). B) Dorsal view of sacrum. C.) Right innominate, ventromedial view. D.) Right and left innominates, ventral view. E.) Subadult left femur, anterior view. F.) Left tibia, anterior view. G.) Left tibia, lateral view. H.) Intermediate phalanx, dorsal view. Scale Bar = 5 cm. Courtesy of nature.com

The authors maintain that Pezosiren‘s tail was likely utilized to maximize the effects of spinal dorsoventral undulation. Theoretically, this locomotory style would have resulted in a strong propulsive force being delivered to the tail and hindlimbs. Additionally, it’s of vital importance to note that Pezosiren, like modern hippos, had osteosclerotic (“very dense”) appendicular limb elements, enabling the sirenian to almost effortlessly remain submerged for extended periods of time. The significance of this fact has been described at length by fellow paleo-blogger Brian Switek (whose upcoming book I simply cannot wait to get my greedy little paws on!) and ultimately boils down to the observation that Pezosiren would have been capable of a much wider range of motion underwater than upon any other form of terrestrial realm. 

 





Weekly Spotlight: Steropodon

24 08 2010

Good tidings and well-wishes!

Throughout its limited history, I’ve attempted to utilize “The Theatrical Tanystropheus” for the purposes of lending coverage towards bizarre prehistoric creatures who, for a variety of inexplicable reasons, have received relatively little coverage from the scientific community and the media at large. Given this favoritism towards long-extinct oddities, I figured that an ancient relative of one of the modern world’s most beloved biological eccentrics would be most fitting. With that, I give you Steropodon galmani, a Mesozoic precursor of the modern duck-billed platypus (Ornithorhynchus anatinus).

As most paleo-enthusiasts are well aware, Mesozoic mammal remains are often be maddeningly difficult to come by, as evidenced by the fact that Steropodon‘s 1985 discovery marked the first occasion in which a member of the class had ever been discovered in an Australian bed of the era’s sediment. This initial excavation was made in the mid-Albanian Girman Creek formation near the town of Lightning Ridge in New South Wales and consisted of a solitary lower jaw fragment containing three lower molars. In a taphonomic sense, the fossil is noteworthy due to the fact that the material had been long-since opalised, as seen in the following image.

Steropodon sported a compound lower jaw: a trait possessed by many ancestral mammals from this point in time including Teinolophos trusleri, another Cretaceous monotreme known from the region. The fact that the two little mammals also share the derived feature of having a notably deep dentary along with double-rooted molars (as opposed to their multi-rooted counterparts in subsequent monotremes) has led many authors to suggest that the two should be placed into their own family, the Steropodontidae which, in addition to the Ornithorhynchidae, Tachyglossidae, and extinct Kollikodontidae, makes up the Monotremata order, though some researchers have asserted that Steropodon could be more accurately viewed as an ornithorhynchid. Steropodon‘s molars are also noteworthy for their tribosphenic arrangement comparable to that found in modern insectivores and, more importantly from a cladistic standpoint, young platypuses and Obdurodon, their toothed Miocene forebear. However, this particular dental arrangement is considerably more advanced in Steropodon than in its extant duck-billed kin; a fact which has given rise to a considerable amount of debate concerning the phylogenetic affiliations of monotremes as a whole. Intriguingly, the advanced nature of these teeth in Steropodon implies to many Mesozoic paleo-mammologists that the Monotremata split from the Therian subclass of mammals (whose members give birth to live young in lieu of a shelled egg) far more recently than had been previously assumed.

With regards to the animal’s lifestyle, the dietary and ecological habits of Steropodon were likely quite analogous to those of modern amphibious platypuses, although it’s been said that despite their theoretically identical overall size, the deeply rooted teeth of this Cretaceous monotreme may have enabled it to tackle larger forms of fish and other aquatic denizens than those pursued by their present-day descendants.





Weekly Spotlight: Barylambda

19 06 2010

Good tidings and well-wishes!

Last December, as part of a week-long posting extravaganza, I lent the coverage of a “Weekly Spotlight”-style entry to the superficially hippo-like  Coryphodon sp., a pantodont of the North American and European Eocene whose appearance and, in all probability, lifestyle superficially resembled those of extant hippos. In that article, I showcased the considerable range of pantodont diversity by including the following illustration in which the semiaquatic beast is perched at the top:

Restorations of some pantodonts of the North American Paleocene. A. Coryphodon. B. Barylambda. C Titanoides primaevus. D. Caenolambda. E. Pantolambda cavirictus. E. Pantolambda bathmodon. (Courtesy of paleocene-mammals.de)

This week, the sights shall be set just a wee bit lower and, consequently, we’ll discuss the creature immediately below the aforementioned Coryphodon. Barylambda sp. (a genus which contains three known species: B. faberi, B. jackwilsoni, & B. churchilli) was an equally bizarre Paleocene beast whose form and habits were similarly analagous to a subsequent group of well-known mammals: in this case, the famed giant ground sloths of the Americas.

Once again, special thanks go to regular reader Doug for the image!

For those interested in acquiring a quick read concerning the evolution and diversity of pantodonts, please consult the link provided in the opening paragraph. With regards to the purposes of this post, however, some additional taxonomic information must be discussed. Barylambda serves as the namesake genus of the Barylambdidae family whose constituents are known for exhibiting (among others) the following characteristics:

-Robust zygomatic arches which don’t flare outward.

-Long coronoid processes.

-Relatively small heads in comparison to overall body size.

-Unfused scaphoids and centrals.

-Short phalanges… ungual phalanges fissured.

-Long and heavy tails with weight-bearing modifications.

-Enormous pelvises which similarly exhibit graviportal morphologies.

The latter pair of characters (along with the Barylambdids’ noticeably elongated skulls and overall size: the largest individuals reached 2.5 meters in length and weighed approximately 650 kg) are chiefly responsible for the hypothesis which maintains that Barylambda and its kin inhabited the niche which would later be occupied by ground sloths and chalicotheres. As in their xenarthran counterparts, barylambdids almost certainly utilized their powerfully built hindlimbs and muscular tails to enable temporary periods of bipedal locomotion, which would have allowed these beasts to browse on high vegetation in a dietary style which had theoretically remained unseen in nature since the extinction of the therizinosauridae over 10 million years earlier.

May the fossil record continue to enchant us all!





Weekly Spotlight: Plotopterum

12 06 2010

Good tidings and well-wishes!

NOTE: Due to the scarcity of images depicting Plotopterum and its family, this post will be somewhat more “text-heavy” than usual.

Many creationists deride the paleontologist’s seemingly dubious ability to reconstruct entire organisms from solitary bones or even from fragments thereof. Granted, this practice is far from fool-proof and, consequently, the experienced student of this prehistoric study knows better than to inject an irresponsibly large amount of purely hypothetical ideas into reconstructions based on these mysterious fossils. However, what young-Earthers and other non-scientists fail to realize is that a single bone, even an incomplete one, can reveal an immense amount of information about its owner’s anatomy, lifestyle, and taxonomic relationships. A perfect example of this fact lies within the story of the plotopteridae: a family of penguin-like diving birds of the Oligocene and Miocene of Japan and North America.

In 1968, ornithologist Hildegarde Howard of the Los Angeles County Museum classified the isolated proximial end of a coracoid hailing from a mid-Tertiary deposit in the outskirts of Bakersfield. In her official scientific paper on the subject, she gave voice to her suspicion that the bone came from a pelicaniform bird such as a cormorant, gannet, booby or pelican yet was distinct enough to justify not only the creation of a new species, Plotopterum joaquinensis, but a new family as well: the Plotopteridae, the name of which literally means “the swimming winged”.

The coracoid in question.

Just what made this coracoid fragment so special as to warrant this significance in Howard’s view? In her original short communication, she writes:

“The swelling of the lower part of the triosseal canal in the fossil coracoid, the narrowness and thickness of the bone in this area and through the neck, and the anterior overhang of the head are characters found in marine birds such as the penguins and alcids. Although taxonomically unrelated, these two groups of birds are alike in the modification of the wing bones toward a flipper-like condition adapted to under water “flight.” Even in those alcids still capable of aerial flight, the coracoid has similar characters. The swelling of the lower triosseal region tends to narrow and deepen the passageway for the pectoral tendon, and presumably afforded support to the tendon so as to strengthen the upstroke of the wing in swimming. The channel is even more constricted and deeper in the alcids and penguins than in Plotopterum, suggesting that the fossil bird may not have been the equal of these other birds as a swimmer…

The modifications of the bone are entirely different from those found in the coracoid of the flightless cormorant, Nannopterum. In Nannopterum the modifying process has been one of degeneration, whereas the evidence indicates that in Plotopterum the wing had assumed a secondary function as a strong swimming organ. The fact that the modifications of the coracoid parallel those of the coracoid of penguins and auks suggests that the wing elements were shorter and more flattened in the fossil than in the cormorants and anhingas. Obviously Plotopterum represents a trend in aquatic adaptation sufficiently distinct from either of these two existing groups to warrant the designation of a separate family, to be known as the Plotopteridae.”

This conclusion was significantly less obvious to several of Howard’s colleagues. Storrs Olson, a distinguished Smithsonian ornithologist (who still resides at the institution and is considered to be one of the foremost paleo-ornithologists of our time), heavily criticized the perceived boldness of her argument and was vehemently skeptical of her decision to create an entire family on the basis of a single fossilized scrap.

However, Olson was eventually forced to concede the validity of Howard’s contentions when a near-complete bird skeleton which nearly rivaled the largest modern penguins in size was unearthed from the Oligocene of Washington in 1977 by the late, great amateur fossil collector Douglas Emlong. According to David Rains Wallace’s “Neptune’s Ark: From Ichthyosaurs To Orcas”:

“Its rigid, paddlelike wings were powerful enough to ‘fly’ through the water penguin-fashion, and its sturdy leg bones suggested that it too had waddled about on land. But it wasn’t a penguin. In fact, its wing bone turned out to be like Plotopterum‘s proving that Howard’s new family had existed, and Olson accordingly named it Tonsala hildegardae. Other skeletal aspects upheld Howard’s idea that Tonsala was a pelican and cormorant relative, although its affinities were more with freshwater anhinga, which [use] feet instead of wings for underwater propulsion. Tonsala must have been an even more efficient underwater predator than its closest living relative and, given its size, doubtless consumed vast quantities of fish, squid, and other prey.”

A reconstruction of Copepteryx, a Plotopterid from the Japanese Oligocene.

Olson has subsequently observed that the presence of these giant, penguin-like birds off the North American West Coast indicates that not only was food abundant, but that the shoreline must have contained islands upon which Plotopterum and its kin could seek refuge from any contemporaneous predatory marine mammals.

It should be noted that in addition to the  aforementioned relationship of Plotopterum and its kin to modern anhingas, Gerald Mayr has suggested that the plotopteridae may have also fact been a sister taxon to penguins as well. Regardless of the precise affiliations of this most intriguing avians, their amazing scientific history stands as a monument to what incredible academic feats the deductive reasoning of knowledgable paleontologists and anatomists can achieve.

May the fossil record continue to enchant us all!





Weekly Spotlight: Onychodus

6 06 2010

Good tidings and well-wishes!

Like many (if not most) of my fellow blogospheric paleo-nerds, I’ve long been a fan of the cultural sensation that is Ray Troll: the only paleontological (and ichthyological) artist I know of whose work can often be cited as “surreal” (how else would you describe an image like this?). Troll’s eccentric style has, in fact, inspired many of my own doodles over the years. However, another passion of this incomparable illustrator has encouraged me to elect this week’s “spotlight”: namely, his undying adoration for bizarre prehistoric fish.

And frankly, they just don’t get much weirder than the mid-to-late-Devonian lobe-fin Onychodus sp. of Germany, England, Norway, the U.S., the Middle East, the Baltic region, and, most notably, Western Australia.

Although I’m completely certain that the animal’s fantastically bizarre dentition has more than a few visitors to this humble publication thoroughly scratching their heads, this will be discussed in-depth later on (Eh, ain’t I a stinker? 🙂 ).

Onychodus is one of the most famous residents of Western Australia’s 375-million-year-old, exquisitely preserved Devonian reef known as the Gogo formation. This paleontologically-vital site has yielded approximately 45 species of fish from essentially every major group alive at the time. As I mentioned earlier, Onychodus itself was an early sarcopterygian or “lobe-fin”, meaning that, in life, its fins were fleshy as opposed to bony and ray-like. More specifically, the (roughly) 2-to-4-meter-long beast is the namesake genus of both the Onychodontida order and Onychodontidae suborder: an exact list of distinguishing characteristics concerning both may be found here.

Onychodus reconstruction. Note that the animal was much more sinuous and eel-like in life.

In the event that anyone interested in paleo-ichthyology and the field’s Australian front in particular might wish to acquire a source of further information, I’d most heartily recommend John Long’s excellent book on the subject entitled “Swimming In Stone: The Amazing Gogo Fossils Of The Kimberley”, which dedicates an entire chapter to this marvelous fish. In it, Long writes:

Onychodus [was first described] in 1857 from isolated tooth whorls, which are sets of curved, dagger-like teeth anchored to a thin bony base. These stabbing lower-jaw teeth are the most characteristic feature of Onychodus and have enabled palaeontologists to identify it from  Middle-Late Devonian rocks in many parts of the world, including the United States, Germany, the Baltic region, the Middle East, and Australia. But the Gogo material is the only known occurrence of articulated, nearly-complete specimens. The Gogo Onchyodus skulls are so well-preserved that when we close the mouth of a reconstructed skull, the lower jaw teeth [will] actually stab through the top of the skull if they couldn’t retract into the mouth. Just as vipers have elastic ligaments that allow them to move their fangs as they open and close their mouths, so Onychodus must have been able to rotate the huge tooth whorls outwards as its mouth opened, and retract them with closure. The extensive cartilaginous jaw joints also indicate extraordinarily wide jaw movement of 120 degrees or more!”

A reconstructed fragment from an Onychodus tooth whorl.

Onychodus lower jaw reconstruction.

The conclusion that Onychodus predated upon contemporary fish, while decidedly unsurprising, has been graphically supported by a juvenile  Gogo specimen of the animal which boasts the remains of a small, unidentified placoderm tucked away in its skull. The latter creature was an estimated 30 cm in length while its attacker is believed to have stretched for  approximately 60 cm in life. Ergo, this particular Onychodus likely died as a result of attempting to swallow a victim which was half of its own size: a predicament similar to that which almost certainly befell the participants of the famed Kansan “fish-in-a-fish” skeletal pair.

Courtesy of palaeos.com

But just how did Onychodus capture its prey and, more interestingly, how did its distinctive tooth whorl come into play? To answer this most engaging question, I shall once again turn to John Long who writes:

Onychodus… [has a] retractable tooth [whorl] and a… specialized short braincase structure that allows a high degree of movement. Such features are perfectly in accord with the early specialization of an ambush-lunge predator that crunches down hard on its prey with massive stabbing teeth. Like the modern moray eels, which its skull superficially resembles, I envisage Onychodus lurking within dark crevices in the reef waiting for unsuspecting prey to pass by the opening before it darts out and grabs it, And as its mouth closes, the retractable whorls bring the struggling prey further into its huge mouth and throat cavity. Finally, with a few quick but well-timed lunges forward, the prey is swallowed whole…

[Some 2001] Onychodus material from Gogo revealed some amazing features. The sensory-like canals, which in early lobe-finned fishes are normally confined to the bones surrounding the eye, opened into the upper jaw bone on Onychodus, which would have enabled the hunter to utilize a special sensory field immediately in front of its jaws. The braincase was ossified in the front half; the rear half was largely cartilaginous. This would have been useful as a shock absorber when biting down hard. The pectoral girdle bones, which are usually tightly fitting in many primitive oteichthyans, were usually loose fitting, enabling the fish to open its jaws really wide. All these features spoke to me of one thing: predation.”

An Onychodus engaged in its theoretical hunting technique.

While Onychodus‘ cranial morphology is indubitably fascinating, the anatomy of its pectoral fin is far more significant in the evolutionary sense. Prior to the discovery of Panderichthys (and the slightly-younger but much more famous Tiktaalik), Onychodus was in fact the oldest known vertebrate of any kind to sport the basic tetrapod limb pattern of a humerus connected to a radius and ulna for quite some time. This facet of the fish’s anatomy corresponds quite nicely to the hypothesis of it being an ambush predator: such powerful forelimbs, when coupled with its muscular, serpentine post-cranial body, could have easily assisted the beast’s forward lunges while assailing its prey.

May the fossil record continue to enchant us all!





Weekly Spotlight: Daphoenus

29 05 2010

Good tidings and well-wishes!

At longtime reader Zach Miller’s request to cover an Amphicyonid “bear dog”, I’ve dedicated this post to one of the family’s most widely-preserved North American genera, Daphoenus sp.

Daphoenus sp. skeleton.

The genus was named by the famed American anatomist and paleontologist Joseph Leidy in 1853, with the first scientifically-described species being D. vetus. Five additional species have subsequently been established: D. hartshorianus, D. lambei, D. ruber, D. socialis, and D. transversus.

D. vetus skull.

Daphoenus has become the namesake genus for the Daphoneninae : one of the two known North American Amphicyonid subfamilies, with the other being the Amphicyoninae. According to Robert M. Hunt’s article in “The Evolution Of Tertiary Mammals In North America”:

“The Daphoeninae is considered here as a monophyletic North American endemic subfamily… [Its species are united by the following characters]: [Upper Molars or “M”]2-3 relative to M1 not enlarged in contrast to amphicyonines in which M2-3 are enlarged crushing teeth with amplified surface area; no reduction of premolars; p4 unreduced, often elongate, with squared posterior border; auditory bulla preserved only as an ossified ectotympanic crescent, loosely attached to the skull, without addition of any ossified entotympanic elements and without lateral prolongation into a bony external auditory meatus…; lack of expansion of the bulla posterior to the mastoid process; inferior petrosal venous sinus deeply excavated into edge of basioccipital; medial edge of petrosal in only slight contact with margin of basioccipital, not sutured to the basioccipital as seen in canids.”

Daphoenus Reconstruction.

In less technical terms, the Daphoeninae also bears the following non-exclusive generalized plesiomorphic characteristics:

-A generalized canine-like dentition.

-A relatively unspecialized and somewhat “feline” postcrania.

-Elongate cranium coupled with a short facial region of the skull.

-Presence of M3

-Lack of accessory cusps on anterior premolars.

-Elongation of lower limb elements (including the feet).

-A probable limitation in the ability to pronate/supinate the forelimb.

These features strongly insinuate that Daphoenus and its kin were cursorial beasts which were either overwhelmingly carnivorous or omnivorous with a bias towards predation.

In this figurine diorama, a Moropus is harassed by a fairly large Daphoenus.

As for Daphoenus itself, the skulls of it’s various species varied from a mere 14 cm in length (D. hartshorianus) to 24 cm in length (D. sp.) with the largest of these creatures rivaling a modern coyote in overall size. Some species are believed to have been sexually dimorphic, with the “males” sporting large canines and robust rostrums whilst the “females” maintain relatively small canines and gracile rostrums. The related species Brachyrhynchocyon sp. can be distinguished from this contemporaneous genus on the basis of the latter’s longer, narrower skulls and narrow premolars. Daphoenus is known from over sixty skulls (several of which contain associated lower jaws) along a number of postcranial skeletons, in addition to many isolated rostra, mandibles, and maxillae.

Daphoenus skull reconstruction.

The amphicyonids first emerged some 44 million years ago in Asia during the Mid-Eocene epoch before spreading into Asia and North America in the early Oligocene before eventually being out-competed by the precursors of modern ursids, canines, and felines by the Miocene’s conclusion. It should be noted that while these “bear-dogs” exhibited canine dentitions and a degree of homogeneous ursid-like cervical anatomy, they are not considered to have been members of either family: it would appear that all three groups have merely emerged from a common ancestor.

Daphoenus reconstruction.

May the fossil record continue to enchant us all!





Weekly Spotlight: Agriotherium

17 04 2010

Good tidings and well-wishes!

Bears are actually very weird creatures. They’ve adopted a plantigrade stance, they’re heavily omnivorous carnivorans, and they’re easily the largest modern amniotes to engage in hibernation (though, it should be noted that many comparative physiologists maintain that the ursid variety of this behavior can be better described as “winter lethargy”). Even the way popular culture depicts them is eccentric: in many regions of North America, indigenous people live in fear of grizzlies (Ursus arctos horribilis) and/or black bears (Ursus americanus) while simultaneously cuddling and adoring their stuffed, manufactured counterparts.

So it should come as so surprise that the prehistoric relatives of these massive beasts were largely an odd lot, too. Of course, the most famous examples of bizarre ursid kinsmen are the famed ‘Bear Dogs’ (‘Amphicyonids‘) and the over-hyped giant short-faced bear (Arctodus simus), the latter of which will be discussed in greater detail later on. Another perfect, but little-known, participant in this trend is Agriotherium sp., a genus ranging from the Miocene to the Pleistocene in North America, Europe, Africa, and Asia.

Agriotherium africanus skeletal reconstruction.

Agriotherium has been historically considered a member of the Ursavini tribe: which includes and is named after Ursavus sp., the earliest known New World constituent of the Ursinae subfamily. The tribe is most easily recognized by their shared possession of small, simple anterior molars (which, in some species, are even further reduced), the relatively large fourth frontal premolars which were well-designed for shearing, and plantigrade stance (which distinguishes them from several earlier and contemporary groups of ursids such as the aforementioned ‘bear-dogs’). However, several recent authors have claimed that Agriotherium should instead be placed within the Ursinae itself.

Agriotherium schneideri mandible.

As for the genus itself, in volume one of “The Evolution Of Tertiary Mammals In North America”, Robert Hunt writes that, among other features, “Agriotherium‘s outstanding traits are its anteriorly shortened lower jaw… [and] rudimentary [second metacarpal] talon.”

In “Ardipthecus Kadabba“, the authors explain “the possible presence of three phases of agriotheriine radiation during the Miocene. In the first phase, Indarctos arctoides was the only known species in Europe throughout the Vallesian… until it was replaced, in the second phase, by Indarctos atticus, a species that possibly arose from its predecessor. The third phase took place in the early Pliocene with the contemporaneous appearance of Agriotherium in Africa, Asia, and North America… [The] extinction of Indarctos atticus coincided with the proliferation of Agriotherium, and this may indicate a replacement of the former by the latter. However, it does not necessarily indicate an ancestor-descendant relationship, since Agriotherium was already highly diversified across continents towards the end of the Miocene…[It’s been] argued that an ancestor-descendant relationship between Indarctos and Agriotherium is merely based on stratigraphic occurence and not founded on synapomorphies. Based on [the] study of Agriotherium intermedium from China,… [some] have concluded that Agriotherium may have descended from a Hemicyon group. As a result, the origin and affinity of Agriotherium remains uncertain.”

Upon beholding the comparatively-lengthy limbs and strong dentition of the Agriotherium species, many authors have attempted to reconstruct this beast as a “hypercarnivore” which would have theoretically chased down ungulates and other land mammals to feed its disproportionately-high metabolic rate, as seen in the following illustration.

Arctodus has undergone similar treatment from the paleontological and artistic communities, having easily acquired more ‘super predator’ hype than any other fossilized ursid genus. However, Cameron McCormick of “Lord Geekington” has written an excellent article which explains why this “Godzillafication” of the short-faced bear is almost certainly a gross exaggeration, citing such reasons as its short canines, somewhat laterally-directed orbits, and a host of cranial features which closely resemble those of the largely herbivorous Tremarctos. Agriotherium has been similarly assumed to have been an insatiable, agressive, and powerful killer, yet it shares essentially all of the features which have forced the scientific community to disregard Arctodus as a creature befitting of this description. While both bears, in all likelihood, did consume meat in addition to foliage, it’s probable that this protein-rich fodder was generally acquired by way of scavenging rather than active hunting, but I have no intention of breaking open that particular can of worms by discussing this further.

May the fossil record continue to enchant us all!