Warning: Creating default object from empty value in /home/offpanel/parryandcarney.com/wp-includes/functions.php on line 364
Parry and Carney » Archive » A Farewell to Arms
Mike Keesey  

A Farewell to Arms

October 10th, 2006 by Mike Keesey :: see related comic

(Tip of the hat to Tim Williams for the title.)

Carnotaurus arms are ridiculous. They’re tiny, with three stubby clawed fingers and one that isn’t even clawed. And there’s barely any forearm, so the hand sprouts almost directly from the elbow. Short and inflexible.

But Carnotaurus and other abelisaurids aren’t alone in this regard. Other members of the Silly Little Arms Club are spinosauroids, carcharodontosaurids, tyrannosaurids, ratites (ostriches, kiwi birds, etc.), phorusrhacids (”fear cranes”), diatrymatids, etc. Why did this reduction happen so many times across so many different lineages? What’s the common factor?

The most obvious commonality is that these are all theropods. The other major dinosaur groups, the generally herbivorous sauropodomorphs and ornithischians, actually trended in the opposite direction, starting out as facultatively bipedal runners and developing into quadrupeds with bulky forelimbs. This happened at least four times: in sauropods, in coronosaurian ceratopsids, in hadrosauriform ornithopods (which retained some degree of bipedality), and in eurypods (ankylosaurs and stegosaurs).

Why are these theropods different? For some, it may be the predatory lifestyle. In many groups, as body size increases, the heads grow larger as the arms grow smaller. Abelisaurids, spinosauroids, carcharodontosaurids, tyrannosaurids, phorusrhachids, and (possibly) diatrymatids all probably used their massive jaws, lined with sharp teeth (or, in the last two cases, sharp beaks) to catch prey, with assistance from taloned feet. No need for arms.

Interestingly, two other types of large theropod, therizinosaurids and ornithomimosaurs, had the opposite condition: gigantic forelimbs and tiny little heads. Perhaps not coincidentally, these are two of the few Mesozoic theropod groups thought to be potentially herbivorous.

Where does this leave ratites, with tiny heads and tiny arms? Perhaps because they are secondarily flightless, the forelimbs had become too modified for any other use, and so they were reduced when flight was abandoned or completely lost, in the case of dinornithid ratites, a.k.a. moas. Penguins (spheniscids) are the only long-flightless birds to have retained substantial forelimbs, and they arguably still fly, albeit in a different, more viscous medium than most avians.

9 Responses to “A Farewell to Arms”
Ivan wrote:

Spinosauroids have puny arms? Oh, wait. You mean the megalosaurs.

Mike Keesey wrote:

Yes, spinosauroids are a.k.a. megalosauroids or torvosauroids. Spinosaurid arms may not be as puny as those of abelisaurids and tyrannosaurids, but they are still punier than those of similarly-sized therizinosaurids, ornithomimosaurs, and dromaeosaurids (well, presumably—we don’t have complete arms for the largest dromaeosaurid, Utahraptor). (You may occasionally see a restoration of a spinosaurid as quadrupedal, but this is erroneous.)

Debbie wrote:

I don’t really understand all the content in the post (and my heart is still sore from the tragic deaths of Ferd and Dan) but the title is BRILLIANT.

dakiwiboid wrote:

Poor Carny! Not only has Carnita left him, but he looks ridiculous!

ReBecca wrote:

I love this one! To funny! Thanks for the laugh, hope to see you at the meeting next week.

Neutrino Cannon wrote:

Alvarezsaurs. Silliest. Limbs. Ever.

And what’s the final word on advanced phorusrhacids having clawed raptorial forelimbs?

Mike Keesey wrote:

Mononykine alvarezsaurs are definitely in the running.

As far as I know, nobody’s ever found such a claw, just a place where it “might have” attached. Been a while since I read about it, though.

Mike Keesey wrote:

Yeah, see ya in a few days, ReBecca!

Albert (Netherlands) wrote:

I compared the forelimbs of the alvarezsaurs with diatrymid birds … fascinating !


Leave a Reply


Parry, Carney, Carny, dinosaur, dinosaurs, dino, Dinosauria, Carnotaurus, carnotaurin, carnotaur, Parasaurolophus, paleontology, paleontologist, paleo, palaeo, paleoart, paleo-art, palaeoart, palaeo-art, palaeontology, ancient, early, palaeontologist, prehistoric, prehistory, prehistorical, Mesozoic, Era, Cretaceous, Jurassic, Triassic, Cenozoic, Paleozoic, Palaeozoic, Maastrichtian, Cambrian, Precambrian, K/T, antediluvian, evolution, evolutionary, life, Darwin, Charles, Darwinism, Owen, Richard, reptile, reptiles, reptilian, Reptilia, fossil, fossils, fossilized, fossilised, saurian, extinct, extinction, predator, predation, predate, prey, ecology, ecological, paleoecology, palaeoecology, palebiology, palaeobiology, theropod, Theropoda, ornithopod, Ornithopoda, hadrosaur, Hadrosauria, hadrosaurid, Hadrosauridae, duck, billed, duckbilled, duckbill, carnivorous, carnivore, carnivory, meat, eating, meat-eating, flesh, flesh-eating, scavenger, scavenging, hunting, hunter, plant, eating, plant-eating, herbivore, herbivory, herbivorous, omnivore, omnivory, omnivorous, formation, eat, devour, consume, diet, gaping, maw, jaws, teeth, digestion, digest, digestive, habit, habits, behavior, behaviour, ethology, paleoethology, creationism, creationist, creation, intelligent, design, ID, debate, controversy, theory, hypothesis, science, scientific, scientist, vertebrate, vert, crush, development, evo, devo, evo-devo, bite, chomp, fight, coprolite, ichnite, Saurischia, saurischian, Ornithischia, ornithischian, sauropod, Sauropoda, brontosaur, bird, avian, Aves, nonavian, non-avian, Avialae, Carnosauria, carnosaur, Abelisauria, abelisaur, abelisauroid, Abelisauroidea, abelisaurid, Abelisauridae, Carnotaurinae, carnotaurine, ceratosaur, Ceratosauria, ceratosauroid, neotheropod, Neotheropoda, Lambeosaurinae, lambeosaurine, sastrei, walkeri, cyrtocristatus, sexual, dimorphism, dimorphic, robust, gracile, origin, flight, homology, digit, cranium, femur, tibia, metatarsal, metacarpal, crest, horn, vertebra, vertebrae, rib, dorsal, ventral, anterior, posterior, rostral, caudal, distal, proximal, apomorphy, synapomorphy, plesiomorphy, symplesiomorphy, character, characters, phylogeny, phylogenetic, taxonomy, taxonomic, taxa, taxon, systematics, biology, zoology, paleozoology, palaeozoology, tetrapod, Tetrapoda, endothermy, ectothermy, homothermy, endotherm, ectotherm, poikilothermy, poikilotherm, warm-blooded, cold-blooded, warm, cold, blood, blooded, bradymetabolic, tachymetabolic, metabolic, metabolism, geology, geological, geologist, strata (Who Links Here?)



Deprecated: Function eregi_replace() is deprecated in /home/offpanel/parryandcarney.com/wp-content/plugins/wp-shortstat.php on line 103

Deprecated: Function eregi() is deprecated in /home/offpanel/parryandcarney.com/wp-content/plugins/wp-shortstat.php on line 216

Deprecated: Function eregi() is deprecated in /home/offpanel/parryandcarney.com/wp-content/plugins/wp-shortstat.php on line 219

Deprecated: Function eregi() is deprecated in /home/offpanel/parryandcarney.com/wp-content/plugins/wp-shortstat.php on line 222

Deprecated: Function eregi() is deprecated in /home/offpanel/parryandcarney.com/wp-content/plugins/wp-shortstat.php on line 225

Deprecated: Function eregi() is deprecated in /home/offpanel/parryandcarney.com/wp-content/plugins/wp-shortstat.php on line 228

Deprecated: Function eregi() is deprecated in /home/offpanel/parryandcarney.com/wp-content/plugins/wp-shortstat.php on line 231

Deprecated: Function eregi() is deprecated in /home/offpanel/parryandcarney.com/wp-content/plugins/wp-shortstat.php on line 234

Deprecated: Function eregi() is deprecated in /home/offpanel/parryandcarney.com/wp-content/plugins/wp-shortstat.php on line 237

Deprecated: Function eregi() is deprecated in /home/offpanel/parryandcarney.com/wp-content/plugins/wp-shortstat.php on line 240

Deprecated: Function eregi() is deprecated in /home/offpanel/parryandcarney.com/wp-content/plugins/wp-shortstat.php on line 243

Deprecated: Function eregi() is deprecated in /home/offpanel/parryandcarney.com/wp-content/plugins/wp-shortstat.php on line 246

Deprecated: Function eregi() is deprecated in /home/offpanel/parryandcarney.com/wp-content/plugins/wp-shortstat.php on line 249

Deprecated: Function eregi() is deprecated in /home/offpanel/parryandcarney.com/wp-content/plugins/wp-shortstat.php on line 249

Deprecated: Function eregi() is deprecated in /home/offpanel/parryandcarney.com/wp-content/plugins/wp-shortstat.php on line 249

Deprecated: Function eregi() is deprecated in /home/offpanel/parryandcarney.com/wp-content/plugins/wp-shortstat.php on line 252

Deprecated: Function eregi() is deprecated in /home/offpanel/parryandcarney.com/wp-content/plugins/wp-shortstat.php on line 257

Deprecated: Function eregi() is deprecated in /home/offpanel/parryandcarney.com/wp-content/plugins/wp-shortstat.php on line 262

Deprecated: Function eregi() is deprecated in /home/offpanel/parryandcarney.com/wp-content/plugins/wp-shortstat.php on line 262

Deprecated: Function eregi() is deprecated in /home/offpanel/parryandcarney.com/wp-content/plugins/wp-shortstat.php on line 267

Deprecated: Function eregi() is deprecated in /home/offpanel/parryandcarney.com/wp-content/plugins/wp-shortstat.php on line 302

Deprecated: Function eregi() is deprecated in /home/offpanel/parryandcarney.com/wp-content/plugins/wp-shortstat.php on line 307

Deprecated: Function eregi() is deprecated in /home/offpanel/parryandcarney.com/wp-content/plugins/wp-shortstat.php on line 312

Deprecated: Function eregi() is deprecated in /home/offpanel/parryandcarney.com/wp-content/plugins/wp-shortstat.php on line 317

Deprecated: Function eregi() is deprecated in /home/offpanel/parryandcarney.com/wp-content/plugins/wp-shortstat.php on line 322

Deprecated: Function eregi() is deprecated in /home/offpanel/parryandcarney.com/wp-content/plugins/wp-shortstat.php on line 327

Deprecated: Function eregi() is deprecated in /home/offpanel/parryandcarney.com/wp-content/plugins/wp-shortstat.php on line 332

Deprecated: Function eregi() is deprecated in /home/offpanel/parryandcarney.com/wp-content/plugins/wp-shortstat.php on line 337

Deprecated: Function eregi() is deprecated in /home/offpanel/parryandcarney.com/wp-content/plugins/wp-shortstat.php on line 342

Deprecated: Function eregi() is deprecated in /home/offpanel/parryandcarney.com/wp-content/plugins/wp-shortstat.php on line 347

Deprecated: Function eregi() is deprecated in /home/offpanel/parryandcarney.com/wp-content/plugins/wp-shortstat.php on line 352

Deprecated: Function eregi() is deprecated in /home/offpanel/parryandcarney.com/wp-content/plugins/wp-shortstat.php on line 357

Deprecated: Function eregi() is deprecated in /home/offpanel/parryandcarney.com/wp-content/plugins/wp-shortstat.php on line 362

Deprecated: Function eregi() is deprecated in /home/offpanel/parryandcarney.com/wp-content/plugins/wp-shortstat.php on line 367

Deprecated: Function eregi() is deprecated in /home/offpanel/parryandcarney.com/wp-content/plugins/wp-shortstat.php on line 372

Deprecated: Function eregi() is deprecated in /home/offpanel/parryandcarney.com/wp-content/plugins/wp-shortstat.php on line 393

Deprecated: Function eregi() is deprecated in /home/offpanel/parryandcarney.com/wp-content/plugins/wp-shortstat.php on line 400

Deprecated: Function eregi() is deprecated in /home/offpanel/parryandcarney.com/wp-content/plugins/wp-shortstat.php on line 405

Deprecated: Function eregi() is deprecated in /home/offpanel/parryandcarney.com/wp-content/plugins/wp-shortstat.php on line 410

Deprecated: Function eregi() is deprecated in /home/offpanel/parryandcarney.com/wp-content/plugins/wp-shortstat.php on line 415

Deprecated: Function eregi() is deprecated in /home/offpanel/parryandcarney.com/wp-content/plugins/wp-shortstat.php on line 420

Deprecated: Function eregi() is deprecated in /home/offpanel/parryandcarney.com/wp-content/plugins/wp-shortstat.php on line 423

Deprecated: Function eregi() is deprecated in /home/offpanel/parryandcarney.com/wp-content/plugins/wp-shortstat.php on line 428

Deprecated: Function eregi() is deprecated in /home/offpanel/parryandcarney.com/wp-content/plugins/wp-shortstat.php on line 433