Wednesday, September 2, 2015

Terror Birds Cometh: A New Hypothesis Unlocking Phorusrhacid Feeding Dynamics & Ecology

*Warning scenes and depictions of extreme animal violence will commence

If you are new to this blog or this series of posts you will get best utility by starting with this post and working forwards to follow the thrust of my thought and ideas since these posts build into one another.

All right time to talk about terror birds or, as I like to think of them, the most recent radiation of large bodied terrestrial ziphodont theropods. Yep they have all the hallmarks of a true ziphodont theropod (except for, you know, the teeth); long and muscular neck; strong and rugose orbital brow ridge/top of skull; tall and deep skull braced for strength in the dorso-ventral plane but still relatively lightweight with a central hollow cavity and mechanically weak in the lateral plane; and a relatively weak bite force. Sound like anybody we know?

Now wait a second... what about that whole study pointing to these birds using a unique punch and jab routine in which repeated hammer blows delivered from the tip of the beak killed prey (Degrange et al. 2010)? Well, I am going to be getting into that study on Andalgalornis, in fact the data from that study is what I am going to use to prop up my contention that not only were teratornithids true big game hunting ziphodont predators they were "toothed" but not in the normal sense of the word. Like modern carcass rendering birds (new & old world vultures, petrels) they were equipped with cutlery in the form of a serrated tongue and choanal papillae that interfaced together to commence "choanal grinding" and were true flesh rendering machines of the highest caliber.

Andalgalornis credit Degrange et al. 2010

Again, note the congruence in general form to other theropods. Deep reinforced skull but with weight saving pneumatic cavities, narrow laterally, vaulted and thick orbital ridge and upper bill to absorb stress and strain. Remind you of somebody else with similar features?

Allosaurus credit Witmer labs
Now Allosaurus had those serrated, mechically reinforced teeth that, I argued, when combined with rapid dorsoventral movements of the neck in a "shimmy" motion instigated a diabolical bone saw technique to saw through skin, muscle, cartilage, and bone. The jaw was weak because the driving power was outsourced to the neck musculature. Phorusrachids lacked serrated teeth but they did have that strong downcurved beak. It was the hooked tip of the bill that grabbed onto a plug of meat from a prey animal (alive or dead) which brought said plug of meat into the shearing section - the middle of the jaw - I contend. Here a combination of rapid dorsoventral shimmies of the neck and rapid serrated tongue oscillations against the choanal papillae worked to render the meat. After being mechanically compromised, the flesh was broken off with a strong leveraging hook and pull action powered by the entire head, neck, and legs.

If choanal grinding was the predominant feeding method of these birds we should expect to see the highest capacity for stress and strain along the middle section of the jaw.

Granted these various finite element tests (from Degrange et al. 2010) on Andalgalornis, a golden eagle, and cariama were calculated with the bite force (133 N for the terror bird) centered at the tip of the jaw. It is worth looking at where the stress is greatest though. In order to help read this the small chart in the upper left of the diagram goes from relatively weak Von Mises force in the blue upwards to progressively higher forces through the green, blue, yellow, and red colors. If the color is white, well that means the force is off the charts and could potentially imply catastrophic mechanical failure with increasing force. In A, D & G we see that the lateral shake is not looking to good for any of the birds. Note that although the middle of the jaw for Andalgalornis is running red the tip of the beak is off the charts in white realm. I will return to lateral forces later in this post btw. If we look at B, E & H which is a normal bite the whole jaw line is in the nice blue realm for Andalgalornis while the tip of the beak is running red. This suggests that the tip of the beak - which supposedly is meant to withstand the most harrowing pressures when it is slammed into prey - is actually starting to trend into inferior performance during a normal bite pressure. What would happen if it slammed into struggling prey at even higher pressures? And finally we get to the pull back and here again we see the middle of the jaw outperforming the tip of the beak which we can quite readily see is going from red into white color implying the potential for catastrophic failure.

credit Marcos Cenizo
If the tip of the beak really functioned in the battle axe capacity that has been suggested for it as a way to stun/kill prey then we should expect this portion of the skull to show lots of blue color during these strain tests. Except we don't. In all the tests the middle of the jaw - which is where the action is occurring via choanal grinding I suggest - is outperforming the tip of the jaw.

Prediction is met and the battle axe interpretation appears less valid than typical choanal grinding as performed by modern carcass rendering birds (new & old world vultures/petrels) which I first discussed here.

*It should also not go unnoticed, per my previous post theorizing on the mechanical stress relief of theropod head crests/ridges/lacrimal crests that the surparorbital ridges maintain some of the most "blue" areas confirming the mechanical advantage I ascribed them.

Here are some other problems with the battle axe interpretation:

1) Lack of a modern analogue. If this method of prey acquisition is adaptive we should expect to see at least a few of the 10,000 or so birds in the world evolve some type of analogous prey capture technique. But they are lacking.

2) Difficulty striking a moving, struggling prey item with precision. To kill an animal with a precise blow to the back of the skull or neck as suggested in this method is likely more difficult than assumed. Felids have to grapple and restrain prey in order to initiate their precise biting mechanism. Repeated blows to kill larger prey items seems problematic too as such hooked tips tend to gouge into and get caught in flesh rather than cut through items.  We know this due to recent functional tests on the "sickle" claws of dromaeosaurid theropods working more as hooks than slicers. Additionally if a phorusrhacid gets entangled with a large prey item in this manner it is now in danger of sustaining destructive lateral forces from said prey struggling.

3) Dubious depth perception capabilities. For the head to swing back and then into a prey item it is hard to imagine how the phorusrhacid's eyes can stay trained on the prey - especially to hit precise targets such as the back of the skull, vertebral articulation ete etc. If I were to play creator for a second and wanted to design a bird that could pull off this killing technique I would make a sort of composite heron/woodpecker design. Exquisite depth perception, reinforced skull, straight and pointed bill for precise powerful blows. Phorusrhachid skull design is more similar to other carcass rendering birds and extinct theropods and most likely suggests that it fed in a similar fashion.

4) Prey size question. While the battle axe interpretation does not outright dismiss large prey capture it certainly favors a more small/medium game emphasis. This interpretation is ecologically untenable because - with the exception of a few land crocs and marsupial predators - phorusrhacids were far and away the largest, most diverse, and longest lasting predators in South America. They were also the only large South American predators that penetrated into North America. It just makes more ecological sense for them to prey on the largest prey items available to them. No extant terrestrial predators grow to the size of Titanis or Kelenken to primarily hunt prey the size of rabbits or small antelopes.

5) Bite strength. The authors of the Degrange et al. study openly struggle with the relatively weak bite force of Andalgalornis (133 N) which is less than several small mammalian predators. This relatively weak bite force, especially when combined with an increasingly akinetic skull is a bit of an enigma.

Larry Witmer (from here) on bite force:

"We were surprised that the force of biting wasn't greater in Andalgalornis. As we say in the article, our estimate of bite force might be a bit low for some technical reasons, but in general we don't think this bird was delivering hugely powerful bites."

6) Battle Axe/Hammer blow model not consistent with pneumatic structure within skull. Although the skull was large, reinforced mechanically in the dorso-vental plane, and, due to it's size, was absolutely heavy it was made relatively light by a large central pneumatic cavity in the upper jaw. In the battle axe model such a cavity would diminish the impact of blows because of loss of mass. Although, in fairness, such loss of mass could be compensated for by increased acceleration.

Andalgalornis with special prominence of choanal papillae & serrated tongue (c) Duane Nash

However these problems seem to melt away if we invoke a biting adaptation analogous to modern  carcass rendering birds (new & old world vultures, giant petrels) and Mesozoic theropods.

1) Loads of modern analogues for this method. In terror birds what you are essentially looking at is a hopped up lappet-faced vulture or giant petrel. While typically castigated as weak billed scavengers these birds routinely dominate the "predatory" eagles/hawks/falcons at carcasses, engage in combative behavior amongst themselves, drive off and intimidate mammalian carnivores, and are well established hunters and killers in their own right. The absolutely more massive and robust bodied/billed phorusrhachids would be even more impressive in these regards.

2) No precision bite necessary in this model. Prey is bit, hooked into by the bill tip, grinded in the mouth against serrated tongue and choanal papillae, and finally yanked back by the beak/neck & leg musculature until massive trauma facilitates death. Consumption of prey likely began before death. Not pretty or quick but a time honored theropod tradition.

3) Depth perception to a high degree is uncalled for. Through comparison with the way giant petrels and various vultures kill prey - through prolonged and repeated biting, yanking, and grinding encounters - we see it is not necessary for precision bites as called for in the battle axe model i.e. precise depth perception not necessary.

4) Average prey size increases. Giant petrels kill birds almost as large as themselves. Vultures kill relatively large ungulate calves, especially in mobs. Single phorusrhacids were likely capable of killing animals as large, or slightly larger, as themselves and, in groups, targeting animals absolutely larger than themselves. This makes sense ecologically because although South America hosted other large carnivores, phorusrhacids were the most diverse, widespread, long-lasting, and common large predators on the continent. It makes ecological sense for them to be targeting the largest prey available to them. There are no large 50 kg plus terrestrial predators that concentrate or is limited to a prey base that is 1/4 or less of their own size. You might not agree with this assertion but I can't think of one predator that is so ecologically hemmed in. Comments section is open. Peer review has been outsourced to the readers of this post. Generally large carnivores take prey up to and marginally beyond their own size.

5) Strong bite force is not necessary for this model. The cutting of meat via choanal grinding is dependent on speed and friction - not static pressure. The driving musculature facilitating prey trauma and flesh rendering is the serrated tongue and choanal papillae followed by pulls from the neck and  legs to pull off bites. These were the two largest muscle masses in the bird's body and are where we should look for possible clues to feeding tactics.

6) Large pneumatic cavity in skull convergent with large foramen (especially antorbital) in ziphodont theropod skulls. Such a weight saving adaptation proves useful in the need for rapid dorsoventral movements of entire head to assist in choanal grinding and pull back motions for prey dismemberment.

credit Degrange et al., pneumatic cavity in Andalgalornis skull

There is no need to invoke a feeding method for which there is no modern proxy, and which has significant mechanical and practical problems. A method largely congruent with modern day large carcass rendering birds (new & old world vultures, giant petrels) provides an elegant analogy for phorusrhacid feeding behavior albeit not taken to the extremes that phorusrhacids took such behavior and adaptations. All things being equal, it is more parsimonious to seek modern analogues - especially within the same order - than assume novel and unparalleled feeding adaptations.

For physical confirmation of the likely presence of potentially robust and mechanically reinfornced choanal papillae below is a still taken from the video from this study. You can clearly see the two large ridges of bone - on which the choanal papillae would have sat - in this shot of the roof of the mouth in Andalgalornis.

Turkey vulture mouth closeup showing serrated tongue & choanal papillae.
credit Williston Conservation Bird Trust Blog

Now the above gif is not provided to provide simple shock value, shocking as it is, but used to argue a corollary in the feeding apparatus that I argue is largely congruent among phorusrhacids, Mesozoic ziphodont theropods, and modern flesh rendering birds like giant petrels. You should note the strong leveraging capability of both the neck and legs working in conjunction. As well as the rapid "chewing motions" of the beak where I have argued the serrated and stiff tongue is shredding the tissue against the choanal papillae. But more importantly you want to note how the petrel works to keep the fight in the vertical realm. As mentioned earlier and as supported by the Degrange et al. study the phorusrhacid skull is weak when confronted with stresses in the lateral realm. Allosaurus and Mesozoic ziphodont theropods likewise had skulls that were ill-equipped to handle substantial stress in this realm. Petrels and vultures too have skulls likely weak in this realm and their feeding behavior supports this notion. They don't shake their head side to side when interacting with prey or a large carcass. Instead all these animals have a vested interest in keeping the field of battle strictly limited to the vertical plane.

Gina Carano Ground & Pound CC2.0
To make a rough analogy to sports let us look at the two main contrasting styles of fighting in mixed martial arts. You have fighters that are most comfortable and effective as upright strikers. They would rather play to their strengths and keep the fight off the mat but upright where their ability for rapid and powerful strikes is most useful. And then you have the specialist floor grapplers. They want to take the fight to the floor where they can utilize their superior grappling skills and specialized submission hold technique. And of course there are fighters that blend the two such as in the pic above where Gina Carano blends grappling with striking to devastating effect in a technique known as "ground and pound". The take home message is that it is in the fighters vested interest to dictate the terms of in what realm the fight occurs based on his/hers respective abilities.

So if we look at the topic from this perspective we can test it to see if it holds any merit based on presumed prey base for these birds. If phorusrhacids were analogous to "strikers" and wanted to keep the fight upright and in the vertical plane we should expect their prey base to be on the whole more like "grapplers" with a lower center of gravity and more geared towards taking the fight to the lateral realm. Which when we look at the presumed prey base of phorusrhacids they are, as a whole, not striking me as especially swift/cursorial track & field superstars.

Notoungulates (including toxodonts): although there are some smaller and swifter varieties like Protypotherium that might have been about as quick as rabbits they are overwhelmingly pretty stolid, clunky bruisers when you get down to it. Certainly no indication that they were on their way to matching the cursorial abilities of derived horses or antelopes. *Update, spoke too soon. Thomas Holtz caught my mistake - there were cursorial herbivores in South America. (see comments below)

Homalodotherium cunninghami. Notoungulate. credit Smokeybjb. CC3.0

Nesodon imbricatus. Charles R. Knight. public domain

Xenarthrans - these are the weird armored guys - including ground/tree sloths, armadillos, glyptodonts, anteaters & tamanduas. Again these animals are not going to win any races.

Megatherium americanum. Hakan Svensson. CC3.0
Glyptodon & Doedicurus. credit Robert Bruce Horsfall. public domain
And later after the great American interchange Gomphotheres were very successful in South America as well.

Stegomastondon mirificus. Wolfman SF. public domain
But don't forget about Macrauchenia. These interesting animals - what is that a camel spliced with an elephant - appear a little leggier than the other critters discussed so far. Speed is always a good tactic but, just giving it an eyeball test I would probably most likely infer it on par with a camel. Probably a good fast trot - but not on par with advanced horses/antelopes.

Macrauchenia patachonica. credit Robert Bruce Horsfall. public domain
But, whatever cursorial ability this animal had, what is more important is the suggestion that via its flexible shin and ankle bones these animals had outstanding agility. They could twist and turn on a dime. Admittedly I can't track down an actual source for this ability - it is just repeated several times on the wikipedia page. If anyone has more info, the comments section is open.

All right, so a prey base not necessarily highly cursorial but with armor plated skin, striking hand claws or clubbed tails, large size/robust build, and potentially good maneuverability. Does this sound familar? It should because these characteristics describe the Mesozoic prey base for theropods pretty much tit for tat.

Thyreophoran dinosaurs - stegosaurs, nodosaurs, and ankylosaurs - were both squat, armored, and to varying degrees armed with counterattacking tail clubs, shoulder spikes etc etc. Very reminiscent of xenarthan mammals such as armadillos/glyptodonts.

Pelorplites & H. sapiens immature female
Sauropods/Saurolophine hadrosaurs - Absolutely larger than theropods but also armed to varying degrees with strong tails/tail clubs, foot claws, dermal armor, and lateral sweeps of neck and tail. Analogous to gomphotheres but also tail wielding glyptodonts and giant sloths to a point.

Saurophaganax, Apatosaurus ajax, & Matt Weddel CC4.0

Therizinosaurs/Giant Oviraptors/Ornithomimids - Hand claws and stout build have often been compared to giant sloths.

Nothronychus credit Taylor/Weddel 2013 CC4.0

Cerartopsids/Pachycephalosaurians aka Marginocephalia - Stout, sturdy build & counterattacking head armament & beaks. Some parallels to notoungulates.

Montanoceratops cerorychos. credit Barnum Brown. public domain

Hadrosaurs/Iguanodonts - Turning agility superior to theropods perhaps analogous to turning ability in Macrauchenia vs. phorusrhacids. Kicks and tails swipes also important.

Iguanocolossus. credit lukas Panzarin from PLOS ONE

To have such high congruence in anti-predator strategies in Mesozoic dinosaurs and South American mammals should not be dismissed. I am not the first person to note this congruence. But it is suggestive of a similar method of attack - and weakness - shared between phorusrhacids and Mesozoic predatory theropods.

Faced with theropod marauders you can out-grow, out-fight, out-manoeuvre, or out armor them. Or some combination there of. But none of these methods was likely completely foolproof and phorusrhacids, as their theropod antecedents did likewise, probably were crafty enough to find flaws to exploit in all of the above defenses.

An interesting comparative test is useful when we compare placental mammalian predators/herbivores. The dominant trend here I would argue is that mammalian herbivores have been characterized by an increasing cursorial adaptation. This makes sense when we look at their predators. Canids and hyaenids are pursuit pack hunters. Felids are stealth grapplers. If you are big and strong it is sometimes a good tactic to stand your ground and fight - but this is only viable if you are many orders of magnitude larger and stronger than your predator. Otherwise running is probably the best tactic that works against both felids and canid type predators. Which is taken to extreme levels in various ungulates but especially horses and gazelles. If marsupial predators in South America were the prime danger to the large prey species that lived there we should expect them to evolve primarily in a direction that negated the likely stealth/ambush/grapple strategies employed by borhyaenids / sebecid crocodylomorphs / sabre-toothed Thylacosmilus. Except we don't see that pattern. South American prey species were relatively slow - although sometimes agile - and were more often big, clunky, armored brutes. Exactly opposite the pattern we see in mammalian pack hunting/ambush predator faunas but exactly congruent with Mesozoic ziphodont theropod dominated ecosystems. And like Mesozoic prey species they developed anti-predator armament - tail clubs, large clawed forelimbs, large size - useful in dealing a strong lateral blow to the theropod glass jaw.

The eastern Shasta ground sloth (Nothrotheriops texanus) and the four Titanis walleri terror birds had been at an impasse for several hours. Although both species were recent immigrants to North America the long standing predator prey arms race between these two lineages was not a recent development and heralded back tens of millions of years to their cooevolution on South America. The ground sloth had backed itself into a thicket of palmetto palms and cactus where it turned and faced its attackers.

Scrub Palmetto credit Jud McCranie CC4.0
The terror birds could not attack from the rear here and, faced with the pummeling hand claws of the sloth, were disadvantaged. But the location was in the full hot Florida sun and the birds then commenced a waiting game. When the sloth - after several hours in the sun and facing heat exhaustion - saw several of the scurrilous birds engage in an actual physical fight made it's break for cover. Less than 50 meters away it had excavated an extensive burrow system in the Karst topography. But the sloth would not make it 10 meters.

Although surprisingly quick, especially in dense brush, the sloth had failed to account for the location of the dominant matriarch of the birds. She, the largest of the flock, stood over 2.5 meters tall and weighed over 170 kg. Having quietly crept down to lie behind some palmettos posterior and adjacent to the sloth she had simply waited for her opportunity. When the sloth made for cover her long legs covered the distance in less than a second. Her aim was deliberate and intentional. She quickly drove into and bit with her hooked beak the softest and most exposed area on the rear of the sloth under the tail - it's anus . And with a series of almost imperceptibly quick serrated tongue and neck oscillations she had established a grip on the sloth's rectum and large intestine. Now with the muscles in her neck and muscular legs working in conjuction she pulled back hard. In a macabre and gruesome tug of war,  the sloth pulling in the other direction from the bird helped facilitate its own fatal outcome - disembowelment.

The sloth realizing it's predicament switched from fleeing to fighting. Mortally wounded it's fate was already sealed. Dancing and lunging from all directions the terror birds harried and harassed the cornered sloth. They knew that exhaustion and blood loss would hasten the death. And with their superior aerobic capacity, speed, and heat threshold the advantage lay firmly with the birds now.

Perhaps there was good reason for ground sloths to excavate and seek shelter in their extensive tunnel systems....

bats in ground sloth paleoburrow Brazil. c/o GeorgiaBeforePeople

We can just be thankful for the advent of relatively quick killing predators like felids and constricting/poisonous snakes. The most common method of killing prey during the Mesozoic and in Cenozoic South America was most likely breaching of the body cavity via the anal/cloacal opening. They eat your asshole out of you while you are still alive.

P.S. Some, or even most, might strongly disagree with my self-publishing style via blog post. Indeed the pitfalls of such method are well documented. I choose this method because it is accessible to all, and - with the use of visuals, video, links, gifs - a superior platform to express ideas in my opinion. Furthermore published academic papers tend to suck the life out of such work, are often behind paywalls, insist on inane formatting rules, cumbersome citation regulations, and peer review is no fool-proof method anyways. To be perfectly transparent I am not going to go through all that. So this is what you get. I know that I have an intelligent and growing audience so I would rather out-source the peer review process to them. If something can survive the slings and arrows of the internet comment section then maybe there is some merit there.

And what does everyone ask as soon as a new paper is published? "Is it online? open access? Can someone send me a pdf?"

Finally going through such prescribed channels is against my D.I.Y. ethos. Why should I PAY some other agency for the privilege to publish MY idea? Especially when they are going to insist on such a dry, cumbersome format? And then THEY get to profit from it?

And to those who simply will not cite, mention, or acknowledge my work because it has not gone through this prescribed process I give you this. If you claim to be a curious, scientifically minded person you should be less concerned with "THROUGH WHAT VENUE I AM GETTING THIS INFORMATION?" but instead "DOES THIS INFORMATION HAVE MERIT?" I have no hidden specimens outside of scientific scrutiny. Whatever I use is from online information available to all.

BTW I have seen popular books, personal communication, unpublished data, anecdotal records all in one form or another cited in reference in published peer reviewed material. So why not blog posts?



Degrange FJ, Tambussi CP, Moreno K, Witmer LM, Wroe S (2010) Mechanical Analysis of Feeding Behavior in the Extinct “Terror Bird” Andalgalornis steulleti (Gruiformes: Phorusrhacidae). PLoS ONE 5(8): e11856. doi:10.1371/journal.pone.0011856

Snively, Cotton, Ridgely & Witmer 2013 Multibody Dynamics Model of Head and Neck Function in Allosaurus (Dinosauria, Theropoda). Paleontologica Electronica May 2013

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Thomas Holtz said...

Not so fast (:-)) on the "Certainly no indication that they were on their way to matching the cursorial abilities of derived horses or antelopes" when it comes to South American ungulates. Thoatherium, Diadiaphorus, and some of the other proterotheriids were very bovid- or equid-like. In the case of Thoatherium it was even more one-toed than Equus, losing even the splints of metatarsals II and IV which are still present in horses. The larger proterotheriids were sheep-sized animals, so well within terror bird menu range.

Duane Nash said...

Fair enough thanks for catching that. Those species certainly point to cursorial adaptations. But I still contend that a terror bird need not evolve into the size of a Titanis or Kelenken to tackle such prey. Something more along the lines of Andalgalornis at about 1.5 meters would be well suited to tackle such a prey base. Modern predators, even avian, are not nearly as limited in prey size as has been suggested for phorusrhacids. And I would still suggest that the overwhelming signal for prey animals in South America is large, graviportal, armored and more than willing to stand and fight as opposed to run away. The larger phorusrhacids evolved to match this prey base. Exactly as their theropod antecedents did.

BrianL said...

Sounds legit, all of this. Surely you'd expect a formidably sized and armed predator to take large prey. Still, how do you see these guys interacting with teratornithids? To be honest, I thought your post on them smacked a bit too much of 'awesomebro' for my liking since I find it a bit hard to imagine birds with a 5 meter wingspan and fairly short legs getting airborne and outrunning charging bison , but I guess that was also because you did not really discuss them and how you came to your conclusion as you do in your other posts. I would really like you to elaborate a bit on them. You also left *Argentavis* as an exercise to the reader, but what's your personal opinion on Argie Bulker's lifestyle?
In this post, I notice no mention of *Brontornis*. While fairly poorly known, it is probably the largest and certainly heaviest and most robust of all phorusrhacids (I noticed you spelled it as 'phorusrhachids' a number of times, by the way). What do you make of this extreme critter, a glyptodont specialist? There's also the fact that phorusrhacid legpower was tremendous, apparently. While legs certainly play a role in your scenario, neither vultures nor giant petrels have major drumsticks, as far as I know and for the regular pulling action you propose for phorusrhacids their legs seem overpowered. Do you see a role for kicking? (I'm imagining our *Brontornis* almost literally curbstomping a glyptodont's armour or skull here and secretary birds and, more importantly, seriemas certainly kick their prey to stun or kill it.) How about kicking in theropods in general?

Duane Nash said...

Thanks for comment Brian L.

I do have to counter your charges of "awesomebro" with this Livestock Depredations by Black Vultures & Golden Eagles from that paper: "Vultures disabled young lambs and calves by first pecking out their eyes and then attacking vulnerable soft parts (rectum, genitals, nose). Cows giving birth were attacked in a similar manner. The prey animals were attacked in groups of 20 to 60 vultures." (thanks YW Lee)

So if black vultures - smaller and weaker in all aspects to teratornithids - can do that to cows/calves then I don't think my interpretation is beyond the pale. Additionally, if you watch footage of large African vultures interacting with relatively faster mammalian predators (faster than giant bison anyways) they get right up on them practically and can generally get away from charging hyenas, lions etc. Teratornithids had good wing loading and pretty robust legs too which is why some envision them as ground stalking rabbit hunters or something like that (I don't think that was their primary adaptation obviously).

"neither vultures nor giant petrels have major drumsticks" I don't know about that they seem pretty adept on the ground and routinely batter themselves and other combatants (eagles, jackals) with their legs.

Yes you are right about the terror bird legs. A lot of thought has centered on how speedy they were - I have heard allusions to ostrich like speed. While I don't know about that they were certainly fast - at least as fast as any of their potential prey. Battering prey is certainly an option - especially smaller stuff - but I think that the primary driver was in pulling back against prey. As I mentioned in the post they had a vested interest to keep the interaction off the ground and in the vertical realm. Ground combat and taking lateral strikes to the skull is something that they would have tried to avoid. So when engaged with prey the legs would be pulling back hard - similar to how that petrel is pulling hard against the penguin in the gif I provided. And also how the Titanis is pulling back hard against the ground sloth in my pic.

Misspelled phorusrhacid... damn it I thought I got all those gonna go through it again.

As for Brontornis & Argentavis I have no reason to assume that they were radically different than how I have portrayed both respective types of bird - except on a larger scale. Wasn't there something about Brontornis not actually being a true phorusrhacid? Got to check more into him.

PHoovy said...

Thats an amazing theory you got there, i always got displeased how phorusrhacids are interpreted as "inferior" to mammalian predators(look at how phorusrhacos appeared on walking with beasts for instance). Your andalgalornis drawing is very original too, that huge serrated tongue looks very gorgeous and imposing at the same time, most other phorusrhacids in paleoart look too samey too me.

Some of the theories about their extinction also bother me, specially the one about mammals eating all their eggs(reminds me of the "mammals ate all the dinosaurs eggs" theory).

Do you have any thoughts on why phorusrhacids didnt get as big as large theropods?

Im hoping yours ziphodont theropod posts will get more attention in the future... But for now im only waiting to see what else you have in store.

Oh, and about the whole brontornis is not a phorusrhacid thing, i remember reading about it here:

BrianL said...

Yes, but if you take a more recent post on phorusrhacids from Darren Naish, I asked him about *Brontornis* in the comments and I was told that this classification was upturned in later studies and that Big B is indeed a phorusrhacid instead of some sort of galloanseraean. I dredged up the exact comment here:

Duane Nash said...

@PHoovy thanks and my thoughts exactly about their supposed "inferiority". I was thinking about going more into potential ideas about that and their extinction. If so how did Titanis penetrate all the way into Florida? One angle I was looking at is that phorusrhacids might be more competitive with canid type predators... I was looking for information on wolves penetrating into South America and they did make it... but the if I remember correctly dire wolves are only known from 3 locations... a potential thing to look into later.

On size not reaching dino dimensions: I have no idea!!

On mammals eating eggs... I am actually intrigued by the potential for mammalian predators - with their emotional intelligence - to target immature phorusrhacids in order to wipe out future potential competitors. Mammals do seem to have that sort of "blood feud" thing going for them. I.E. Lion/hyena wars or wolves killing coyotes were they kill off each others' offspring - and hunger is not the motive. But then again raptors kill off other raptors in their territory too...

All in all it was probably a more mundane combination of loss of herbivores/weather changes/loss of open habitat.

On Brontornis hey probably it was!! I wish there was a dedicated blogger/source of info on the web for phorusrhacids. It's just kinda scattershot out there...

Anonymous said...

I wonder if sabretooths also used their tongues for delivering nasty cutting wounds. Cats have some huge papillae anyways.

Anonymous said...

Also, Harpagornis has a vulture or phorusracid-like skull. Could it also have had chainsaw jaws?

Duane Nash said...

Doubtful on sabretooths they had those fangs already!! The serrated tongue/papillae in carcass rendering birds evolved to mimic the role of serrated teeth in their theropod antecedents I argue. In birds the gene to grow teeth has been turned off.

The serrated tongue in cats is actually used for scraping meat off bones.

On Harpagornis it potentially could have evolved a parallel system. Looking at the pic on wikipedia the skull looks relatively long with some nice ridging on the palate like I pointed out in the Andalgalornis skull. Maybe!!!

Mark Gelbart said...

Ground sloths would have crushed terror birds. They had armor under thick fur...terror birds could not have penetrated that. They were much larger and heavier and had powerful upper body strength and big claws. A ground sloth vs. a terror bird or birds would have been a complete mismatch. Giant anteaters, a much smaller but similarly built animal, can kill jaguars.

I doubt terror birds preyed on anything larger than a rodent or rabbit.

Duane Nash said...

Thanks for sharing your opinion Mark Gelbert. I do concede that a strong lateral blow to the skull of a terror bird by a sloth could have a devastating impact as their skulls are not optimized for handling strong lateral blows.

But I don't accept the assertion that just because animals are dangerous and difficult to handle that they are universally avoided. And on the armor plated skin you will note that in my vignette the birds targeted the anal region thus negating the armor defense. And regarding the osteoderms in the skin - is there any proof that they covered the entire body in a solid chain mail suit? Most likely there were significant gaps in the armor - the face, genitals, anal region, underbelly, movable joints.

And per your use of the giant anteater vs jaguar as an argument: Of the 438 prey killed, we documented 139 head of cattle (43 adults, 96 calves), 107 caiman (Caiman crocodilus yacare), 92 peccaries (mostly Tayassu pecari), 18 feral hogs (Sus scrofa), 17 marsh deer (Blastocerus dichotous), 14 giant anteaters (Myrmecophaga tridactyla), 9 capybaras (Hydrochaeris hydrochaeris), 7 brocket deer (Mazama americana and M.gouazoubira), and a number of other avian, mammalian, and reptilian species. source Predator-Prey Relationships and Spatial Ecolgoy of Jaguars in the Southern Pantanal, Brazil: Implications for Conservation and Management Utah State University Digital Commons 2008. available online

Note that, despite their danger. these jaguars ate more giant anteaters (14) than capybara (9) or brocket deer (7).

Your argument, sir, is invalid.

And finally I am dismissive of the notion that such a long-lasting lineage of predators was so ecologically hemmed in that they could only eat rodents or rabbits. This quite patently makes no sense. Name me one type of large predator that is so limited as has been suggested for phorusrhacids. There is no modern terrestrial predator of similar size that is so constrained as you suggest. Even great blue herons eat rabbit sized prey.

BrianL said...

The more I think about it, the more I think Haast's Eagle was not just weird in being as huge as it was, but even more so in an ecological sense.
In its case, we are looking at a very large eagle existing in an environment without any non-chiropteran mammals, with no crocodiles, no large monitor lizards, no snakes, no vultures, no other eagles, no giant barn owls or eagle owls and no large accipitters. Instead, it co-existed with a decidedly 'difficient' predator guild consisting of a falcon, a goshawk- or eagle-mimicking harrier, two small owls, a raven, an opportunistically hunting parrot (kea), a large, omnivorous flightless rail (weka)and a large, flightless and very robust likely omnivore/carnivore (*Aptornis*, the adzebill) in an environment with plenty of flightless herbivorous birds. Of those, the eagle likely preferentially hunted the larger/largest ones around, moa, which weighed many times its own weight.
*Harpagornis* lived in the strange situation where it was a flighted top predator with very large prey indeed and very little, if any, meaningful competition to share it with. Given your outline about vultures in these articles, their absence seems pretty significant here. Unlike most large eagles, *Harpagornis* did not have these powerful and aggressive competitors and kleptoparasites around, unless adzebills played that role. Even then, this might mean that *H.* could ecologically, in a sense, be both eagle and vulture when dealing with carcasses that would generally be much larger and meatier than what other eagles normally deal with. If so, this would probably have made its abilities and lifestyle even more interesting than already seems obvious. It certainly makes me wonder to what extent this bird was, ecologically speaking, a flighted phorusrhacid.

Other birds that might be interesting to consider given their status as large, likely terrestrial hunting birds of potentially large prey are the Cuban *Ornimegalonyx* owls (incidentally mistaken for phorusrhacids at first) and the possibly flightless caracaras of Jamaica and perhaps elsewhere in the Antilles.
The absence of mammalian competitors and the presence of ground sloths and large rodents may have made them big game hunters in their own right.

Duane Nash said...

Very insightful comment Brian L. I do also wonder about how our vision of eagles today might be coloring our vision of how Harpagornis operated. All very pertinent comments about lack of viable terrestrial competition and duality as the dominant scavenger and predator. I honestly have gave it less research than you have but I would be curious about its leg musculature and if it was a little more terrestrial than modern eagles? Maybe a bit like a giant caracara?

I am going to be steering away from aves in future posts but lots of room for future studies/speculations/and thought from your comments. Would love to see someone pursue these ideas further in some format whether it be art/blogging/research etc etc.

Anonymous said...

Adding to discussion of Harpagornis again, it does seem being a specialist moa slayer seems to have made it into a flying phorusracid. From what I have seen the legs do seem in proportion with caracaras or vultures.

And could adzebills have had shearing mechanisms (possibly modified to work on plants as well as meat)?

Anonymous said...

And I'm tempted to talk about another insular macropredatory toothless ornithodiran-Hatzegopteryx. It was clearly not a super-stork like its relatives, what with its vastly different bauplan, and it was the biggest carnivorous animal (and tallest animal) around. It is now seem as much more of a predator than thought, and considering just how massive that bill is could it have had serrated tongues combined with papilae?

Anonymous said...

Arent seriemas the closest living relatives to phorusrhacids? So, If phorusrhacids had choanal papillae and serrated tongues, shouldnt we also see those present in seriemas?

Duane Nash said...

Now I don't know if this is all just one person posting as anonymous or three of you. Maybe do me a solid next time and use a name.

Adzebills? I have not looked into them deeply but good question!!

As per the last one regarding seriemas and choanal papillae and serrated tongue. I think seriemas are a bit of red herring with regard to phorusrhacids. FIrst off we don't know how closely related they are. Their bills have differing robustness; seriemas are still flighted so they are not as heavy and muscled; and seriemas are more like secretary birds over-all. There are some images on the web showing inside their mouth - they do have choanal papillae. Bu they don't have serrated tongue mincing action going on from the looks of it. They dismember stuff by hashing it against the ground and pinning and ripping with their second toe which is a little sickle claw.

I'm gonna leave Hatzegopteryx alone cuz there is some new stuff coming out on it.

Its very likely that the genes that control the soft tissue in the mouth of a bird are very active. These attributes - serrated tongue & choanal papillae can likely be gained and lost fairly quickly in bird evolution. They are in a sense the birds dentition.

Bk Jeong said...

I'm the guy who posted as Anonymous re; Harpagornis and Hatzegopteryx.

The former is another case of how we grossly maligned a predatory species based on the assumption of a slow, stupid scavenger. They seriously thought it was a vulture analogue (as in the popular view of vultures, not actual vultures)

Duane Nash said...

Yeah, I mean there is a lot of "underselling" the capabilities of predators in paleontological interpretation these days. I know it is in the spirit of being conservative but when your interpretation is so conservative that it makes no sense in terms of what real animals do time to go back to the drawing board. Ex. phorusrhacids only eating rabbit sized prey; T-rex the obligate scavenger; sauropods that can't lift their neck above horizontal; small fish only eating plesiosaurs; rabbit or fish hunting teratornithis; theropods as "baby killing specialists" - you can go on and on. If you look at large terrestrial predators today they commonly take prey of their own size or even bigger. Even cheetahs. This trend of diminishing the predatory capabilities of extinct animals - suggesting that 3 meter tall terror birds concentrated on rabbit size prey - it just makes no ecological, physical, or common sense. We might not always know how they did it... but this overt conservatism has to be dialed back in my opinion.

Bk Jeong said...

As much as I hate awesomebros I have to agree. There are ways to kill the most formidable prey animals without risking life and limb.

I was recently criticized for putting adult Mawsonia on Spinosaurus menu; Yes, Mawsonia is huge and a top predator itself, but it's less than half the size of the spinosaur. It's doable.

Bk Jeong said...

And isn't it bizarre only sauropsids are treated that way? Mammalian bias anyone?

Mark Gelbart said...

My argument is not invalid. You didn't even address the size and bulk advantage that a giant ground sloth would have over a terror bird. They would simply crush a terror bird.

To protect the anus, a giant ground sloth would merely have to sit down on its haunches and it would be pretty much invulnerable to a terror bird attack.

My point about the giant anteater killing jaguars was to show how dangerous a small edentate is. Anteaters are smaller than jaguars. Ground sloths were much much larger and heavier than terror birds. It would be like wolves attacking elephants or full grown rhinos. This would result in impotent attacks.

BTW, Gelbart, not Gelbert.

Duane Nash said...

@Mark Gelbert If you go back and read my little fictional vignette I used Nothrotheriops, which is a fairly modest sized ground sloth coming in at about 250 kg (550 lbs). Titanis comes in at at only 100 kg less at about 150 kg (330 lbs). Not a huge discrepancy in size there especially with mob tactics. And you should note that we are in congruence on sloth defense - which I mentioned in my story - as long as it keeps its butt down it is pretty well defended - this sloth was pinned down and made a dash for shelter exposing itself.

Surely you did not assume that I implied giant ground sloths such as Megatherium? I don't think that I made that argument anywhere in the post. Yes giant sloths, when prime, healthy, and fully mature were probably fairly invincible - the young, old, and infirm not so much.

On the jaguar/anteater issue I really don't see that argument being a strong one. Predators do often tackle prey that can and do kill them/cause grievous bodily injury. A cursory review of jaguar diet shows that despite the danger jaguar eat anteater and do so fairly often.

The notion that 3 meter tall terror birds >only< or even mainly ate rabbit size prey is a little silly in my opinion when much smaller and less robust predatory or even primarily scavenging birds can kill rabbits and much bigger.

Daniel Hartig said...

I agree with your argument that terror birds probably tackled larger prey, up to the size of themselves, and they probably used similar tactics to therapods and vulture which is a cool analogy. But I'm going to disagree with you about "inferiority".

I think that evolutionary history shows that some forms are "best" or at least "better" since they repeatedly drive out the competition before them. Here are some questions that I think frame the debate best in the Socratic method:

-Where is there evidence of terrestrial predators (e.g. not crocodillians) competing with carnivorans of >= 50kg (e.g. dogs, cats, hyenas, bears) without those other predators eventually going extinct?

-If terror birds and metatherian sparassadonts had "superior" predatory strategies why did they not drive each other to extinction? Why did they both succumbing quickly to the influx of carnivorans evident with the great american interchange?

I see it like this: With the invasion of new types of herbivore, the cursorial paradigm came to South America, and the existing terror birds and metatherians were simply not able to compete. The weakness of a strategy based on defending yourself is that a predator might come along that is much bigger than you. Well terror birds and metatherians couldn't get bigger, but carnivorans certainly could. After the great american interchange, gigantic cats and bears (such at Smilidon and Arctotherium) evolved that could easily overpower medium size prey that tried to stand its ground, and with ambush tactics suited for tackling more agile prey. Meanwhile, competing herbivores from North American (cervids and equuids I know of, other I am sure were there too) came to the south and competed with these medium sized native herbivores. However, they had already developed an effective cursorial defense against carnivorans and the increase in size just made them easier to avoid. Medium sized south american herbivore species were driven into extinction. From the terror bird's perspective, there are now two types of prey, those too large to tackle, and those too fast to catch. Now it is their turn to go extinct.


Daniel Hartig said...


The stand and defend yourself paradigm is just not an effective strategy in modern terrestrial ecosystems unless you are really big (at least 1 ton). But why is that? I mentioned that carnivorans got a lot larger than the terror birds or metatherians were able to. I believe this has something to do with a carnivoran giving live birth to a pup/cub that can be quickly grown on milk while it spends years learning critical hunting skills. Something I always hear and see repeatedly on David Attenborough nature specials is big cat mothers taking care of two year old cubs that are nearly her size but still can't hunt for themselves. This seems especially important if the prey runs away; you need skills and experience to ambush your prey, but just brute strength to disembowel a fleeing sloth. I do not know if terror birds or metatherians could invest that kind of time and effort in children.

Therapod dinosaurs could get to large sizes because of all the sub-adult dinosaurs of intermediate sizes being spawned by R-selected species that formed an easy an rapidly replenishing prey base (an assumption I got from this blog). For terror birds, the prey base was primarily self-defensive mammals who have an K-selected strategy which means that sub-adults are protected by full adults; which means there is much less meaty reward for much more effort. This basically forces the terror birds to adopt a more K-selected strategy themselves. Here they are at a big disadvantage when a competitor shows up with a fast easy way to fatten up their young (like milk). For metatherians, if they carried their young in a pouch for a long time (I don't know if they are thought to have done that, though they are most closely related to marsupials), that could have been their significant disadvantage.

So in conclusion, I think that terror birds are inferior predators, and I think that the combination of milk, K-selection, and long learning curves leading to increased hunting success of increasingly cursorial species is what did them in, more than any anatomical deficiencies. Carnivorans body plan isn't necessarily any better than the other predatory designs out there, but their social plan is.

Duane Nash said...

Interesting comments Daniel a lot to think about. Ultimately we may never know what drove terror birds into extinction but always fun to muse about it.

two things I like to think about with the whole inferior predator issue, or the mammal vs archosaur predator debate.

1) Mammals, in particular big brained predatory mammals, seem to - and there is really no other way to put - have a propensity to "hate". Our species does it the best but how else can you describe the seeming warfare between lions and hyenas? If I was canid or felid and I was always coming across these damn terror birds at carcasses, trying to eat my cubs or whatever I would develop a strong limbic system "hate" response to them. If I could not catch or kill the adults I would do my best to kill off all and every terror bird hatchling or clutch of eggs I came across. Maybe this was enough to do the birds in.

2) Sloppy, blade toothed archosaurian rauisuchids seem to have outdone the relatively advanced synapsid therocephalian predators of the Triassic. Whether this was due to outright competition or just one group supplanting another over time I just don't know.

Also I think metatherian predators were largely extinct by the interchange and South America did have some cursorial species that were native. Not really seeing why terror birds could not adapt to north american placental herbivores, they did penetrate at least to Florida.

Not sure if I buy the 1 ton rule for stand and fight. Anteaters, sloth bears, badgers, peccaries, ourselves.

Bk Jeong said...

@Daniel: Terror birds were very fast runners, why would they be unable to catch cursorial prey?

Also, predatory archosaurs do spend years perfecting predatory skills, whether under parental care or not.

Daniel Hartig said...

First, I'd like to say thanks for the discussion. Finding reasonable intellectual discussion on the internet is as likely as finding a winning powerball ticket on the ground. I only ran into this site last week and I'm glad I did.

The hate argument seems like a pretty good one. For large carnivores in particular it seems like a significant advantage; and again anyone who watched BBC nature specials knows the big cats and dogs can hate. I have heard that the concept of reptillian/limbic/neocortex architecture is not supported much any more; so it makes me wonder when/how "hate" evolved, what other behaviors it is associated with, and if it is plausible for it to have evolved in one or more branchees of the therapod tree. I don't know if there are any modern birds that have the same "hate" concept.

I also have read that the metatherians may have been circling the drain before the interchange; but I wonder how much of that is just lack of fossil records. After so long on the continent, what must have happened to push them to extinction? Competition for terror birds after tens of millions of years of equilibrium?

Terror birds may be fast runners, but so are lions. Lions are mostly unsuccessful predators when they don't ambush their prey. If they just came running up to some wildebeest, the wildebeest would see them a mile way and run off never to be caught. Terror birds are, first off, tall and probably bad at prowling/ambushing. Second, this is where my argument for parental care and training comes in. It takes lions 2 years plus to be effective hunters because stalking and ambushing require skills and experience. I suppose there is no reason that terror birds couldn't choose that same strategy to raising young, but I argue that mammals do it better because of having milk to power the rapid growth of their young. The slower the growth rate of baby terror bird, the more likely it is to die to predation/competitive "hate" killing/ starvation due to a bad hunting year, etc.

Which brings us to skills training. I love the concept of packs of young therapods acting as an independent ecological element from their full grown parents. And Sue's T. Rex growth curve suggests 15+ years for the big ones before they become full grown hunters; lots of time for experience. But compare apples to apples; how much experience does a 15 year old lioness have? She has been part of a pack hunting team, hunting the biggest game for 12 years now. Sue upon reaching sexual maturity has been hunting different sized creatures in a different ecological niche for the past decade. Sue probably can't even run as fast as she could 5 years ago, hunting is a different game when you weight 2 tons vice 500lbs.


Duane Nash said...

Thanks for compliments Dan. Sometimes people get very emotional with paleo and box themselves into a corner. And I know from experience that I have been that way as a youngster ( I really tried to ignore the evidence that adult T. rex could not run racehorse speed in my teens). I try to always think before I type something on the internet "would I say this to their face?"

Interesting you bring up lions which made me think about how they hunt. Yes, they can put on a pretty good turn of speed. Yes, they do hunt in wide open terrain. However lots of field studies show that they are highly dependent on doing this under the cloak of darkness when their night vision gives them a decided advantage over their prey - or at least they have a way better success rate. I have even read or heard stories of lions strolling in right in amongst herds of zebras and wildebeest on dark moonless nights plucking a hapless victim from the herd.

Which got me thinking... maybe terror birds could hold their own during the day... but at night they suffered casualties. I have no doubt that a grappling equipped large felid could kill a terror bird especially if it got the jump on it and got a good neck clamp. As much as I love archosaurian predators I do have to concede that felids are right up there in any discussion as goes killing efficiency. Maybe not the best at squabbling over carcass rights but for sheer hunting prowess I got to hand it to the cats.

I could see this playing out over several thousand years is that repeated attacks on terror bird clutches and an imbalance of nocturnal abilities could have sealed the fate for the terror birds. Great discussion thanks Daniel, probably going to evolve into a post soon!!

Bk Jeong said...

Felines have much worse stamina than birds, A lion needs cover because it can only sprint, while a phorusracid can use a long chase.

Bk Jeong said...

Also, Duane, you might be underestimating the predatory prowess of archosaurs. A cutting bite kills very quicker, far more so than a stranglehold. If a terror bird used choanal grinding on the throat of its prey, you have instant death right there.

Bk Jeong said...

If the nocturnal advantage of carnivorans is such an advantage, why didn't terror birds die out when they contacted carnivorans in the Pliocene?

PHoovy said...

"-Where is there evidence of terrestrial predators (e.g. not crocodillians) competing with carnivorans of >= 50kg (e.g. dogs, cats, hyenas, bears) without those other predators eventually going extinct?"

Well, i dont think we have many cases of that happening, but i wouldnt say just because a predator goes extinct it has to do with competition, some animals just go extinct for weird reasons. For example, i dont see why depranosaurs died off, as far as i know they were pretty widespread and likely could live just fine a long as there were trees around.

Also, hyenas die rather frequently to lions, but they still get along just fine. But what if for some reason the climate/ecosystem changed and one of those two got extinct? Would that mean one species couldnt handle competition with the other?

"-If terror birds and metatherian sparassadonts had "superior" predatory strategies why did they not drive each other to extinction? Why did they both succumbing quickly to the influx of carnivorans evident with the great american interchange?"

I dont know if it might have something to do with the fossil record? Or climate change? Or maybe youre right and the main driving factor for their extinction was competition with the members of carnivora.

"Well terror birds and metatherians couldn't get bigger, but carnivorans certainly could."

Not sure about that, kelenken and brontornis are big, but we only have fragmentary remains of those, there might have been even bigger phorusrhacids, but the fossil record isnt good enough.

And about carnivorans getting bigger. Idk, they are certainly bigger than most metatherians and S.populator was heavility built, but as far as i see, even the biggest carnivorans arent so much bigger than the biggest phorusrhacids, wasnt there something about arctotherium not being that big?

"From the terror bird's perspective, there are now two types of prey, those too large to tackle, and those too fast to catch."

I think, as long as there was some vegetation to cover them, terror birds could catch fast prey just fine, they have long legs and their good aerobic capacity must have been handy on running down prey.

"you need skills and experience to ambush your prey, but just brute strength to disembowel a fleeing sloth."

I agree on the experience part, i think the fact that carnivoran pups start to learn how to hunt from their parents gives them a advantage against predators that are more "independent" from birth, but predators that lack so much parental care can still learn how to tackle different prey. White sharks and komodo dragons can ambush prey, even though they lack that kind of parental care, i see no reason for you to assume terror birds couldnt learn how to catch fast prey on their own.

About the whole night thing, do we have evidence for terror birds not having adaptations to see during the night? I mean, they arent mammals, but they were in the south america for millions of years, couldnt they have some adaptations for hunting during the night? Or maybe they just didnt need it.


PHoovy said...


"Which got me thinking... maybe terror birds could hold their own during the day... but at night they suffered casualties. I have no doubt that a grappling equipped large felid could kill a terror bird especially if it got the jump on it and got a good neck clamp."

I dont doubt that, after reading about how some big felids are good at hunting, i think it might be possible that even adult terror birds could be in danger(nocturnal vision or not) from a big felid ambushing them. Without the surprise element, they might have been able to drive a nasty felid off, but if theres one thing that felids are good at, its ambushing dangerous game and grappling it down.

And the whole "hate" thing seems likely, im not sure if that was the main reason for terror birds dying out, but its possible. The juveniles would have a heck of a hard time with so many carnivorans wanting to kill them.

Anyway, in the end the terror birds died out, so maybe they just couldnt handle competition with carnivora? Welp, i think its more interesting to think about how they lived and how they affect their ecosystem than how they died actually.

Anonymous said...

Hey Duane, I looked at the picture of the terror bird skull where the choanal (hope I'm not misspelling that) papillae connected to, and I saw he same thing Tyrannosaurus, Velociraptor, and Giganotosaurus. Could this mean that they had the same serrated tongue and "roof teeth" as modern flesh rendering birds and terror birds? I also looked at the skulls and I found that T.rex had the largest of these bone growths, and I was wondering if this meant that T.rex had larger "roof teeth" than other theropods due to the fact that only the front teeth had meat slicing serrations, or did this just mean that they had "roof teeth" that are around the same size? I also saw your Plesiosaur Machinations and that plesiosaurs could have had Leatherback sea turtle like mouths, and I was wondering if this held true for all the marine reptiles like pliosaurs, mosasaurus, and ichthyosaurs. Again, these are just my observations on the animals and I hope you have an answer to it.

Anonymous said...

Duane, I did some more searching and I found out that Cryolophosaurus, Majungasaurus, Carnosaurus, Deinonychus, Albertosaurus, Gorgosaurus, Carcharodontosaurus, Spinosaurus, Suchomimus, Utahraptor, and Morvosaurus. I definitely see a pattern here. They also probably had the serrated tongues too match their "roof teeth", so it seems that most of the theropod groups had these bone growths, and it seems that T.rex has the biggest of these bone growth (I do not know if this is an indication for the efficiency of the flesh rendering) with raptors and carnosaurs coming in at a close second and third.

Anonymous said...

Carnosaurus was meant to be Carnotaurus.

Anonymous said...

Morvosaurus was meant to be Torvosaurus. Stupid autocorrect.

Duane Nash said...

Yeah I would not get carried away like that with choannal papillae in all those theropods - i don't even know for sure phorusrhacids had them it is just an idea. More of a hypothesis than a theory actually and needs testing. Same with the leatherback sea turtle mouth part too. I am glad that the ideas captured your imagination though.

Anonymous said...

Yeah, seems unlikely that all theropods had this, though I suggest that theropods like spinosaurs (to grip onto fish) tyrannosaurs, dromaesaurs (because they are more closely related to birds, and their teeth aren't as good for slicing as much as carnosaurs) and Majungasaurus since it would need to hold onto sauropod necks to deliver the stranglehold

Duane Nash said...

Hi anonymous ... please consider giving yourself a name so I can better follow your questions & comments. The chief reason I think choannal papillae/serrated tongues are not likely in extinct theropods is that they already have perfectly good cutlery to do the job - their teeth. A better way to think about is that toothless flesh rendering birds had to "invent" a solution to the problem of no teeth and hence the serrated choannal papillae and tongues. T. rex would do fine eating and pulverizing carcasses and spinosaurs would do fine as their teeth match well with crocodiles that do not have serrated tongues/papillae. Long and short of it toothlessness (as in modern aves) would probably be a requirement for choannal papillae & serrated tongues to evolve.

Anonymous said...

Ok. By the way, I love your posts. I am wondering what's next on your blog spot. Oh, and I am just going to repeat what I said in your Spinosaurus post: you can call me D-man, I am not comfortable for people To know my real name.

D-man said...

Yeah, sometimes I look at these things and sometimes assume them as fact when really they are either highly speculative or 50/50. Also I believe the same reasoning you put up for ziphodont not have serrated tongues and choannal papillae can also apply for many marine reptiles probably not having it since Leatherbacks have no teeth, they would evolve such a esophagus, but since ichthyosaurs, pleisosaurs, pliosaurs, and mosasaurs already have teeth, it would not be any more beneficial, although I do believe that Archelon and Protostega had it since they are both physically similar and that all sea turtles seem to have that monstrous esophagus.

D-man said...

Sorry for the bad grammar, the auto correct is really bad

D-man said...

I have a question. In the picture that shows a life restoration of Andagalornis made by you, is the smaller andie a baby.

Duane Nash said...

Yes it is mine. Not a baby just smaller .

Duane Nash said...

Regarding the spiked esophagus speculation in plesiosaurs the reasoning I used them in plesiosaurs is that the neck could be used as a food storage device and the papillae keep things moving along as this is their use in leatherbacks which must eat a huge amount of jellies to get enough nutrients from this poor quality food. The papillae in leatherbacks - I don't think they are found in any other sea turtles - are actually soft to the touch and not used in food processing just food movement. This was my reason for speculating them in plesiosaurs.

D-man said...

Ah, I see.

As for other sea turtles having spiky esophaguses, I saw an image that showed that Loggerhead Sea Turtles having a spiky esophagus, so theres that.

D-man said...

Also Duan, what posts are you going to plan for the future.

D-man said...

Thanks for the answers, and I have a question. Which theropod do you think is most suited to take down prey larger than itself. From what I've seen from the bones, I would think it would Majungasaurus because of its powerhouse build, not to mention that although it was "only" 6.5 meters and 1 ton, it took down the sauropod Rapetosaurus which was around 10 to 15 times its own weight and more than twice as long, and it was probably taking it down alone because of the whole cannabalisic issue, they probably were loners that only came together to mate. Let me her what you think

Carliro said...

Bathornithids and other macropredatory Cariamiformes also occured in the northern hemisphere, so if terror birds shaped ecology in South America then their relatives would also have impacted faunas elsewhere.

Questioning said... theropods aside from outliers use anal evisceration as a killing method.

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