Well, that was painful. I decided to join the trend and review the show that's been so hyped- Dinosaur Revolution. Little did I know my yearly allowance of eyerolls would be used up. I only watched the frirst episode "Evolution's Winners" and frankly have no desire to sample more.
First the good. The models were usually excellent, with non-pronated hands and all that good stuff. I especially enjoyed the dilophosaurian snouts on the Cryolophosaurus, and the Mongolian mammals which weren't just shrews or mice. I also liked the homage to Dryptosaurus and Ceratosaurus artwork in the Cryolophosaurus section (though I don't think they could really stand on their tails, given how most theropod chevrons look). The Gigantoraptor's feathering was more problematic, as it seemed more like a naked theropod covered in feathers than an actual feathered creature like a bird, where body outlines are hidden and feathers interact and fold. Its wings were always held out in front, which for a display is fine, but even the female who wanders up is posed this way. The animation itself was a mixed bag. Most moved smoothly, but the Saurosuchus looked unnatural for instance. Similarly, the rendering was good for most, but the therapsids in the opening seen looked plasticy. What's that you say? My "good" paragraph's actually mostly full of criticisms? Guess that prepares the way for the rest of the review...
What made Dinosaur Revolution most difficult to watch is the rampant anthropomorphism. Basically none of the subjects actually behaves like a reptile, or a bird, or even a non-ape mammal for that matter. They're chock full of human mannerisms. You can always tell what they're supposed to be feeling, as if brains that size could even house such emotion. But it's not just behavior. My jaw dropped at the blatant 'sexy eyelash' marks on the female Eoraptors. Why not just go the whole hog and give them real eyelashes they can flutter alluringly? Then the male's heart (shaped like a heart of course) could project from its chest like a piston. Would have been almost as realistic as the expectant smile he shows as she approaches in the actual program. Even ignoring the behavior, the plotlines have so many "entertaining" improbable portions, like the Eoraptor unwittingly throwing a therapsid into Saurosuchus' mouth, that any illusion you're watching reality is destroyed. And what was up with that swarm of hostile flies chasing the Antarctic fauna and killing the lizard... for blood! Is this a 1950s horror movie or something?
Which would have all been excusable if the show at least taught us something. Then it'd be a Dinosaur Train for adults, which wouldn't be my idea of a good program to watch, but would at least educate the part of the public that finds documentaries boring. But no, I don't think there was any actual paleontological data contained in that hour, besides most of the portrayed anatomy and a few basic facts like "birds are dinosaurs" and "Cryolophosaurus is from Antarctica". I say "most" because while the models were largely accurate, they sometimes contained some fictional aspect. The rhamphorhynchoid tail fin on the female Eoraptors, for instance. Or the highly elaborate wattles and soft horns on the male Gigantoraptor. And when it comes to behavior, we have bower-building Eoraptors, color flushing Cryolophosaurus which killed the young of rival males, a stomping and twirling Gigantoraptor mating dance, Glacialisaurus which lived in harems (which we so know from the partial hindlimb...), etc. It's not that these soft parts or behaviors are impossible, but Joe Public's only going to remember Gigantoraptor as "that goofy rainbow-colored thing that dances" or Eoraptor as "those raptors that cutely chirp and build mounds to select mates, and then care for their baby who adorably falls down, awwww". So you're emphasizing the fictional aspects of these animals, while not going into any of the actual known interesting facts about them.
But maybe the show could have retained some use if all of this human-like/fictional appearance and behavior was there to illustrate some greater true scientific fact, that even network execs think viewers could remember. Alas, no. The implication of the Eoraptor portion was that dinosaur success was due to more complex parental care, but my impression has been that evidence for such care is limited to maniraptorans, supposed evidence for care in hadrosaurs (and thus Ornithischia) has been refuted, and that baby sauropods were too small to associate with adults and aren't apparent in herd trackways. And even the mosasaur cares for its babies enough to get revenge on sharks for eating them (vengeance is such a widespread trait in squamates...). As does the Cretaceous mammal, more realistically. If you want to make the point dinosaurs were probably often brightly colored with display structures as the Gigantoraptor portion tries to, a far superior method would be to show say ten different possibilities for a few species in quick succession. Changing colors and adding wattles wouldn't be that resource intensitive and would get the idea across to laymen without making it seem like we know they had definite soft features and patterns (I'm guessing the Yixian pigments were unknown when this was made). The Cryolophosaurus portion taught us about the factual behavior... of lions. The mosasaur segment taught us... er... "a mother's protective instinct is a force of nature than can change the world." And the Glacialisaurus one taught us "a little bad luck goes a long way." That's certainly scientific. Maybe the next episode will teach us "the disadvantaged underdog can succeed with perseverance and faith in himself." Sigh
To sum up, watch if you like largely accurate-looking dinosaurs acting like humans in zany situations and learning valuable life lessons. If you want a show that clearly indicates which parts are based on paleontology, shows dinosaurs as they may have been, and teaches you something about them, keep dreaming.
Tuesday, September 13, 2011
Friday, September 9, 2011
Tehuelchesaurus and how to describe the affinities of a taxon
I've often complained about the tendency for authors to view their most parsimonious cladogram as "the right" tree, such as here and here. I note that it's usually more helpful to describe how parsimonious different hypotheses are, since while new analyses usually change the topology somewhat, they rarely support relationships that were strongly rejected before. Carballido et al. (2011) recently redescribed the sauropod Tehuelchesaurus, and in addition to a detailed osteology and several other important discussions, their paper contains a phylogenetic analysis that did things just the way they should. The analysis (249 characters, 45 taxa) is based on Wilson's (2002) analysis with added data, including numerous newly added macronarians. Some characters were ordered, taxa which cause polytomies were deleted a posteriori, and Tehuelchesaurus emerged as a basal camarasauromorph sister to Galveosaurus, not a relative of Omeisaurus as originally thought by Rich et al. (1999). But instead of simply letting the matter rest there, Carballido et al. included the section "Testing Alternative Positions for Tehuelchesaurus." Music to my ears. They tested not only the Omeisaurus alternative (9 steps longer), but also positions slightly more (1 step longer) and less (2 steps longer) than Galveosaurus, and noted the character support for all of these. In addition, the authors wrote the following which basically covers any plausible position-
"Other positions within basal camarasauromorphs (in any position within the Janenschia/Tastavinsaurus clade, as sister taxon to Europasaurus, more basal than Europasaurus, and as sister taxon to Camarasaurus) and as a macronarian outside Camarasauromorpha, but more derived than Haplocanthosaurus, require three additional steps. Placing Tehuelchesaurus as sister taxon of Haplocanthosaurus results in a suboptimal tree four steps longer than the MPTs, and as the most basal macronarian needs even five additional steps. Even more steps are required to place this taxon in the Titanosauriformes (seven additional steps as a basal somphospondyl and eight additional steps as a basal brachiosaurid).
Any position outside Macronaria also results in considerably suboptimal tree lengths. Five additional steps are needed to make Tehuelchesaurus the most basal diplodocoid, but any position within higher diplodocoids results in trees that are at least ten steps longer than the MPTs. Likewise, placing Tehuelchesaurus outside Neosauropoda requires six additional steps, and any placement among basal, nonneosauropodan taxa results in trees at least nine steps longer than the MPTs. Thus, the possibility of a Jurassic Patagonian clade of sauropods, including Patagosaurus and Tehuelchesaurus, can also be rejected, as it requires 12 additional steps."
The paper succeeds in giving you a much clearer idea of Tehuelchesaurus' relationships than any one cladogram could. Anybody describing a new taxon should follow their example.
Carballido, Rauhut, Pol and Salgado, 2011. Osteology and phylogenetic relationships of Tehuelchesaurus benitezii (Dinosauria, Sauropoda) from the Upper Jurassic of Patagonia. Zoological Journal of the Linnean Society. DOI: 10.1111/j.1096-3642.2011.00723.x
"Other positions within basal camarasauromorphs (in any position within the Janenschia/Tastavinsaurus clade, as sister taxon to Europasaurus, more basal than Europasaurus, and as sister taxon to Camarasaurus) and as a macronarian outside Camarasauromorpha, but more derived than Haplocanthosaurus, require three additional steps. Placing Tehuelchesaurus as sister taxon of Haplocanthosaurus results in a suboptimal tree four steps longer than the MPTs, and as the most basal macronarian needs even five additional steps. Even more steps are required to place this taxon in the Titanosauriformes (seven additional steps as a basal somphospondyl and eight additional steps as a basal brachiosaurid).
Any position outside Macronaria also results in considerably suboptimal tree lengths. Five additional steps are needed to make Tehuelchesaurus the most basal diplodocoid, but any position within higher diplodocoids results in trees that are at least ten steps longer than the MPTs. Likewise, placing Tehuelchesaurus outside Neosauropoda requires six additional steps, and any placement among basal, nonneosauropodan taxa results in trees at least nine steps longer than the MPTs. Thus, the possibility of a Jurassic Patagonian clade of sauropods, including Patagosaurus and Tehuelchesaurus, can also be rejected, as it requires 12 additional steps."
The paper succeeds in giving you a much clearer idea of Tehuelchesaurus' relationships than any one cladogram could. Anybody describing a new taxon should follow their example.
Carballido, Rauhut, Pol and Salgado, 2011. Osteology and phylogenetic relationships of Tehuelchesaurus benitezii (Dinosauria, Sauropoda) from the Upper Jurassic of Patagonia. Zoological Journal of the Linnean Society. DOI: 10.1111/j.1096-3642.2011.00723.x
Wednesday, August 17, 2011
Do we have dromaeosaurid evolution backwards?
The basic evolution of Maniraptora has seemed pretty well established in the past decade, thanks to TWG papers describing Sinovenator, Mei, Mahakala, Xiaotingia and such. The basal paravian was a little bird-like taxon, like Microraptor on the dromaeosaurid end or Jinfengopteryx on the troodontid end, with genera like Rahonavis and Anchiornis breaking the boundaries even more. Going further towards the base of Maniraptora, the cranial similarities between scansoriopterygids and basal oviraptorosaurs have suggested a short-snouted herbivorous ancestor, while Shuvuuia and Pelecanimimus have similar skulls that suggest the first maniraptoriform was not a macropredator. Large, more obviously carnivorous taxa like eudromaeosaurs are seen as reversals to a more traditional theropod lifestyle. It's a nice story and may be right, but what if it's wrong?
Dromaeosaurid morphology forms a continuum from the extreme of Achillobator with its deep snout, mesially serrated teeth, low DSDI, rather short coracoid, posteriorly facing glenoid, relatively short arms, deep brevis fossa, large anterior pubic boot and proximally placed obturator process, though Deinonychus, Velociraptor, Bambiraptor, Sinornithosaurus, Microraptor, Buitreraptor/Unenlagia and ending at Rahonavis. Even if the unenlagiines are avialans though, dromaeosaurids need a lot of reversals no matter which direction evolution went. Note that stratigraphy doesn't strongly support either option. We have Utahraptor from the Barremian which is very similar to Achillobator, and dromaeosaurid-like teeth with mesial serrations resembling both dromaeosaurines and velociraptorines in the Late Jurassic. Then again, there's the microraptorian-like Graciliraptor and Shanag which also lived early, and the possible microraptorian "Paleopteryx" from the Morrison.
There's also a possible transitional form between basal coelurosaurs and dromaeosaurids- Ornitholestes. Like dromaeosaurids, Ornitholestes has a third premaxillary tooth much smaller than the first two, short cervical vertebrae with tall neural spines, prominent anterior cervical epipophyses, a crest-like ventral tuberosity on the humerus, an enlarged second pedal ungual and a transversely expanded metatarsal IV. It's also similar to paravians in the elongate distal caudals and bifurcated chevrons. Deriving dromaeosaurids from something of Ornitholestes-grade would explain why they are almost unique among derived maniraptorans in having prefrontals, which unlike the dental characters of eudromaeosaurs, are not plausibly due to macropredatory habits. In this scenario, microraptorians would be convergent with birds in their aerial characters.
Is there any other evidence for this idea? Don't troodontids show the same pattern as dromaeosaurids, going from Jinfengopteryx/Anchiornis to Mei/Sinovenator to Sinornithoides/Byronosaurus to Troodon? Maybe not. Jinfengopteryx and Anchiornis can switch to Avialae easily, and the same may be true for Mei and Sinovenator. They're often avialans in the in progress Lori matrix, even with Xu et al.'s troodontid characters. Lori itself emerged sister to Sinornithoides in Hartman et al.'s SVP poster and is Jurassic in age, with serrated teeth. Maybe that's the basal grade for troodontids, and birds are related but evolved serrationless teeth, long arms, dorsal ischial processes and such on their own branch.
The Jurassic Haplocheirus also supports this idea, since it shows serrated teeth and a general morphology so primitive that Cau's Sumrukia matrix found it to clade with compsognathids. Note therizinosaurs also have mesial and distal serrations, and that Falcarius has made the clade more basal in most matrices, unlike earlier ideas they were related to oviraptorosaurs. Maybe coelurosaurs were of the compsognathid-coelurid grade all through their evolution, with ornithomimosaurs, alvarezsaurids, therizinosaurs, dromaeosaurids and troodontids+birds each developing their birdlike and/or herbivorous characters separately. This idea is kind of anti-Paulian or anti-BCF in nature and has plenty of precedent in the literature. Ostrom long suggested Ornitholestes as a dromaeosaurid ancestor, and Makovicky (1995) found the two to be sister taxa to the exclusion of birds based on vertebral characters.
Of course the real test is with cladistic analyses, so how does the idea fare? The in progress Lori matrix finds a fairly traditional tree with Ornitholestes sister to Maniraptoriformes, microraptorians and Unenlagia basal among dromaeosaurids, and is somewhat unusual in finding troodontids sister to birds. Constraining Ornitholestes to be a dromaeosaurid and the dromaeosaurid topology 'backwards' from the consensus (Achillobator,Dromaeosaurus(Deinonychus,Velociraptor(Microraptor,Sinornithosaurus))) results in trees 11 steps longer. Not too bad when you consider enforcing Longrich and Currie's (2009) plausible-seeming traditional dromaeosaurid topology is 7 steps longer than the minimum.
Dromaeosaurid morphology forms a continuum from the extreme of Achillobator with its deep snout, mesially serrated teeth, low DSDI, rather short coracoid, posteriorly facing glenoid, relatively short arms, deep brevis fossa, large anterior pubic boot and proximally placed obturator process, though Deinonychus, Velociraptor, Bambiraptor, Sinornithosaurus, Microraptor, Buitreraptor/Unenlagia and ending at Rahonavis. Even if the unenlagiines are avialans though, dromaeosaurids need a lot of reversals no matter which direction evolution went. Note that stratigraphy doesn't strongly support either option. We have Utahraptor from the Barremian which is very similar to Achillobator, and dromaeosaurid-like teeth with mesial serrations resembling both dromaeosaurines and velociraptorines in the Late Jurassic. Then again, there's the microraptorian-like Graciliraptor and Shanag which also lived early, and the possible microraptorian "Paleopteryx" from the Morrison.
There's also a possible transitional form between basal coelurosaurs and dromaeosaurids- Ornitholestes. Like dromaeosaurids, Ornitholestes has a third premaxillary tooth much smaller than the first two, short cervical vertebrae with tall neural spines, prominent anterior cervical epipophyses, a crest-like ventral tuberosity on the humerus, an enlarged second pedal ungual and a transversely expanded metatarsal IV. It's also similar to paravians in the elongate distal caudals and bifurcated chevrons. Deriving dromaeosaurids from something of Ornitholestes-grade would explain why they are almost unique among derived maniraptorans in having prefrontals, which unlike the dental characters of eudromaeosaurs, are not plausibly due to macropredatory habits. In this scenario, microraptorians would be convergent with birds in their aerial characters.
Is there any other evidence for this idea? Don't troodontids show the same pattern as dromaeosaurids, going from Jinfengopteryx/Anchiornis to Mei/Sinovenator to Sinornithoides/Byronosaurus to Troodon? Maybe not. Jinfengopteryx and Anchiornis can switch to Avialae easily, and the same may be true for Mei and Sinovenator. They're often avialans in the in progress Lori matrix, even with Xu et al.'s troodontid characters. Lori itself emerged sister to Sinornithoides in Hartman et al.'s SVP poster and is Jurassic in age, with serrated teeth. Maybe that's the basal grade for troodontids, and birds are related but evolved serrationless teeth, long arms, dorsal ischial processes and such on their own branch.
The Jurassic Haplocheirus also supports this idea, since it shows serrated teeth and a general morphology so primitive that Cau's Sumrukia matrix found it to clade with compsognathids. Note therizinosaurs also have mesial and distal serrations, and that Falcarius has made the clade more basal in most matrices, unlike earlier ideas they were related to oviraptorosaurs. Maybe coelurosaurs were of the compsognathid-coelurid grade all through their evolution, with ornithomimosaurs, alvarezsaurids, therizinosaurs, dromaeosaurids and troodontids+birds each developing their birdlike and/or herbivorous characters separately. This idea is kind of anti-Paulian or anti-BCF in nature and has plenty of precedent in the literature. Ostrom long suggested Ornitholestes as a dromaeosaurid ancestor, and Makovicky (1995) found the two to be sister taxa to the exclusion of birds based on vertebral characters.
Of course the real test is with cladistic analyses, so how does the idea fare? The in progress Lori matrix finds a fairly traditional tree with Ornitholestes sister to Maniraptoriformes, microraptorians and Unenlagia basal among dromaeosaurids, and is somewhat unusual in finding troodontids sister to birds. Constraining Ornitholestes to be a dromaeosaurid and the dromaeosaurid topology 'backwards' from the consensus (Achillobator,Dromaeosaurus(Deinonychus,Velociraptor(Microraptor,Sinornithosaurus))) results in trees 11 steps longer. Not too bad when you consider enforcing Longrich and Currie's (2009) plausible-seeming traditional dromaeosaurid topology is 7 steps longer than the minimum.
Tuesday, August 9, 2011
And the best paper written about a theropod is...
I'm sure I can come across as a grumpy old carmudgeon thanks to my frequent criticisms of papers, even good ones like Benson et al. (2011). Critiquing is fun and I think more important than praise when it comes to scientific papers, but for a change, here's a paper I was floored by.
I was lucky enough to be sent a copy of Dal Sasso and Maganuco's new Scipionyx monograph, and boy does it deliver! Scipionyx is one of those Science/Nature taxa that's initially described in two pages with a couple figures, then goes for years until a decent description comes out (See how I work criticism into even an article designed to praise, heh. Btw, of that list, Enantiornis has since been redescribed, and papers on Guanlong, Buitreraptor and Haplocheirus are in the works. Woo!) Luckily, the illustrations in Dal Sasso and Signore's 1998 paper were superb and covered all the material, so waiting wasn't as painful as it is for some other taxa. Even so, if every 'tabloid taxon' were given this good of a treatment once they were redescribed, I'd have no complaint waiting a decade for them. The monograph is simply unparalleled in every aspect. Quality diagnosis of autapomorphies. Huge illustrations and color photos, extensive explanatory diagrams, x-rays, ultraviolet, different angles. Measurements of everything. Eleven pages discussing the ontogenetic indicators. A phylogenetic analysis using a good base (Senter's TWG modification), codes taxa completely, has explicit coding changes based on new papers and most relevent taxa included (exceptions are Proceratosaurus and Bagaraatan). Then there's the long description of all the soft parts most taxa don't leave us. And the taphonomy. And the physiology, discussing Ruben's terrible ideas. And the quality reconstructions. And the discussion of diet, given its multiple prey remains. The tome ends with several life restorations, of which my favorite is Riboli's. See, that's why I don't write more glowing reviews- saying "x is good, y is good, etc." just gets repetitive and uninteresting. Sort of like how ancient theologians said much more about the tortures of Hell than the joys of Heaven. ;)
As for negatives, Scipionyx and Orkoraptor are grouped together based on the supposed caudal pleurocoels of the former. Yet those are so small they look more like nutrient foramina to me, which have caused similar confusion in Acrocanthosaurus and some therizinosauroids. But Dal Sasso and Maganuco correctly discuss how the Senter matrix does not include relevent taxa and characters from Benson et al.'s study, and that the latter does not include enough coelurosaur information. Also, I would disagree with a couple coding choices for ontogenetically variable characters in Scipionyx, which are discussed in Appendix 5. But hey, what other papers even mention why they code ontogenetically variable characters in young specimens? So really, even the few problems were elaborated on to the point that I can't count them against the authors. The work is simply a masterpiece.
Anyone who wants to write a description of a theropod, look at what Dal Sasso and Maganuco created, and copy its format and scope to the best of your ability.
Dal Sasso and Maganuco, 2011. Scipionyx samniticus (Theropoda: Compsognathidae) from the Lower Cretaceous of Italy: Osteology, ontogenetic assessment, phylogeny, soft tissue anatomy, taphonomy, and palaeobiology. Memorie della Società Italiana di Scienze Naturali e del Museo Civico di Storia Naturale di Milano. 281 pp.
I was lucky enough to be sent a copy of Dal Sasso and Maganuco's new Scipionyx monograph, and boy does it deliver! Scipionyx is one of those Science/Nature taxa that's initially described in two pages with a couple figures, then goes for years until a decent description comes out (See how I work criticism into even an article designed to praise, heh. Btw, of that list, Enantiornis has since been redescribed, and papers on Guanlong, Buitreraptor and Haplocheirus are in the works. Woo!) Luckily, the illustrations in Dal Sasso and Signore's 1998 paper were superb and covered all the material, so waiting wasn't as painful as it is for some other taxa. Even so, if every 'tabloid taxon' were given this good of a treatment once they were redescribed, I'd have no complaint waiting a decade for them. The monograph is simply unparalleled in every aspect. Quality diagnosis of autapomorphies. Huge illustrations and color photos, extensive explanatory diagrams, x-rays, ultraviolet, different angles. Measurements of everything. Eleven pages discussing the ontogenetic indicators. A phylogenetic analysis using a good base (Senter's TWG modification), codes taxa completely, has explicit coding changes based on new papers and most relevent taxa included (exceptions are Proceratosaurus and Bagaraatan). Then there's the long description of all the soft parts most taxa don't leave us. And the taphonomy. And the physiology, discussing Ruben's terrible ideas. And the quality reconstructions. And the discussion of diet, given its multiple prey remains. The tome ends with several life restorations, of which my favorite is Riboli's. See, that's why I don't write more glowing reviews- saying "x is good, y is good, etc." just gets repetitive and uninteresting. Sort of like how ancient theologians said much more about the tortures of Hell than the joys of Heaven. ;)
As for negatives, Scipionyx and Orkoraptor are grouped together based on the supposed caudal pleurocoels of the former. Yet those are so small they look more like nutrient foramina to me, which have caused similar confusion in Acrocanthosaurus and some therizinosauroids. But Dal Sasso and Maganuco correctly discuss how the Senter matrix does not include relevent taxa and characters from Benson et al.'s study, and that the latter does not include enough coelurosaur information. Also, I would disagree with a couple coding choices for ontogenetically variable characters in Scipionyx, which are discussed in Appendix 5. But hey, what other papers even mention why they code ontogenetically variable characters in young specimens? So really, even the few problems were elaborated on to the point that I can't count them against the authors. The work is simply a masterpiece.
Anyone who wants to write a description of a theropod, look at what Dal Sasso and Maganuco created, and copy its format and scope to the best of your ability.
Dal Sasso and Maganuco, 2011. Scipionyx samniticus (Theropoda: Compsognathidae) from the Lower Cretaceous of Italy: Osteology, ontogenetic assessment, phylogeny, soft tissue anatomy, taphonomy, and palaeobiology. Memorie della Società Italiana di Scienze Naturali e del Museo Civico di Storia Naturale di Milano. 281 pp.
Saturday, August 6, 2011
Pneumatic disappointment
Benson et al. have a new paper out on theropod postcranial pneumaticity which I was extremely excited about, but the paper itself came as quite the disappointment. Not the general conclusions, which I agree with, but the data collection. The abstract reads "We review recent work on the significance of pneumaticity for understanding the biology of extinct ornithodirans, and present detailed new data on the proportion of the skeleton that was pneumatised in 131 non-avian theropods and Archaeopteryx." With supposed pneumatic ilia in Piatnitzkysaurus and others, Buitreraptor's pneumatic furcula, Shixinggia's pneumatic femur and other recent records, examining 131 theropods for postcranial pneumaticity would be quite enlightening. It's one of those features that is easily missed unless looked for, not often described, and rarely apparent in photos or illustrations. This is especially true for coelurosaurs, since most of the reported unusual pneumatic bones have been from them. All of the authors (Benson, Butler, Carrano and O'Connor) have done excellent detailed work before, so my expectations were high.
The meat of the paper is appendix S1, which contains all of the primary data. It's available here for those who are interested. The first problem is that it's all axial, so there goes my hope of getting some real info on how common appendicular pneumaticity is. More disappointing though is that only 12 of the 99 coelurosaurs are coded from seeing real specimens. The rest is all from the literature. Not that I'm one to frown on using literature, since that's where much of my data comes from too. And Benson et al. are usually good at determining which data can be coded from the literature and noting when information is from a figure, data matrix, etc.. But the information is basically what I could (and have) accumulated myself, with a few new additions thanks to personal communications with Balanoff and Brusatte, but then again I have my own sets of unpublished photos and AMNH observations with data not used by Benson et al.. I suppose I should be happy since this backs up my thesis that papers covering many taxa usually rely mostly on the literature and that my own upcoming paper explicitly describing codings in coelurosaurs is comparable in this measure to one written by four professional leaders in the field. But this time I was hoping for something more, akin to what Nesbitt et al. (2009) did for theropod furculae.
Benson, Butler, Carrano and O'Connor, 2011. Air-filled postcranial bones in theropod dinosaurs: Physiological implications and the 'reptile'-bird transition. Biological Reviews. DOI: 10.1111/j.1469-185X.2011.00190.x
The meat of the paper is appendix S1, which contains all of the primary data. It's available here for those who are interested. The first problem is that it's all axial, so there goes my hope of getting some real info on how common appendicular pneumaticity is. More disappointing though is that only 12 of the 99 coelurosaurs are coded from seeing real specimens. The rest is all from the literature. Not that I'm one to frown on using literature, since that's where much of my data comes from too. And Benson et al. are usually good at determining which data can be coded from the literature and noting when information is from a figure, data matrix, etc.. But the information is basically what I could (and have) accumulated myself, with a few new additions thanks to personal communications with Balanoff and Brusatte, but then again I have my own sets of unpublished photos and AMNH observations with data not used by Benson et al.. I suppose I should be happy since this backs up my thesis that papers covering many taxa usually rely mostly on the literature and that my own upcoming paper explicitly describing codings in coelurosaurs is comparable in this measure to one written by four professional leaders in the field. But this time I was hoping for something more, akin to what Nesbitt et al. (2009) did for theropod furculae.
Benson, Butler, Carrano and O'Connor, 2011. Air-filled postcranial bones in theropod dinosaurs: Physiological implications and the 'reptile'-bird transition. Biological Reviews. DOI: 10.1111/j.1469-185X.2011.00190.x
Tuesday, July 26, 2011
Epichirostenotes and how it changes coding
Sullivan et al. (2011) just named two new caenagnathids, Ojoraptorsaurus boerei for a partial pubis and Epichirostenotes curriei for ROM 43250, a specimen from the Horseshoe Canyon Formation described as Chirostenotes by Sues (1997). Jaime Headden wrote a great post on the situation here and I agree with his assessment. I'm extremely doubtful Ojoraptorsaurus can be diagnosed, given the large amount of interspecific variation in most theropods and the low number of comparable caenagnathids. But that's not too important considering it's just a partial pubis. My main concern here is a more practical one about Epichirostenotes.
How should we now code Chirostenotes? The genus has been used in many analyses, including the Theropod Working Group matrix, which I've been correcting for the description of a new paravian. In that matrix, it is apparently based on a combination of the Chirostenotes, Macrophalangia and Caenagnathus holotypes, as well as partial skeletons RTMP 79.20.1 (Currie and Russell, 1988) and ROM 43250. It wouldn't be too important, except ROM 43250 is our only described source for coding Chirostenotes' maxilla, braincase, cervicals, dorsals, caudals and pubis. So if we leave it out, we're losing a lot of information. And without a more complete caenagnathid to code, and few overlapping elements, there's a large chance it won't group with Chirostenotes, so could harm oviraptorosaur topology (like coding Caenagnathus separately did for Senter, 2007). But combining it with Chirostenotes could be misleading once Elmisaurus and Hagryphus are added, since nothing argues ROM 43250 isn't closer to these latter genera. While ROM 43250 isn't comparable to either, a second specimen from the same formation (metatarsal II CMN 9570, unmentioned by Sullivan et al.) is distinctive from Elmisaurus due to its lack of fusion and straight distal end. These are plesiomorphies though, so do not argue strongly for its referral to Chirostenotes. And the metatarsal isn't comparable to ROM 43250 anyway, so any referral to Epichirostenotes is based purely on size and provenence. But nothing argues the Horseshoe Canyon specimens aren't Chirostenotes either, since so far the apomorphies of Chirostenotes are only known from the mandible (assuming Caenagnathus collinsi is properly synonymized) and other parts of the metatarsus. The minor differences between the ischia of Epichirostenotes and RTMP 79.20.1 are just like those found between individuals of Tyrannosaurus rex, Microraptor zhaoianus and other species. The distinction boils down to size (which could easily be ontogenetic) and provenence. Now this doesn't make Epichirostenotes a nomen dubium, because the braincase and maxilla are certainly distinct from comparable named theropods, it's just that no other named caenagnathid can be compared for the most part.
Note how the Tyrannosaurus ischial variation mirrors that between Chirostenotes and Epichirostenotes. The latter's ischial diagnosis is-
1. "Ischium long and expanded posteriorly; broad behind obturator process." There is no known comparative length difference, since Epichirostenotes doesn't preserve an ilium and Chirostenotes doesn't preserve a pubis. The posterior expansion and breadth posterior to the obturator process refers to the greater depth in Epichirostenotes. As seen most distinctly between the upper right and lower left pictures above.
2. "obturator process expanded and triangular." This refers to the greater depth of the obturator process and non-rectangular tip in Epichirostenotes. As seen between the two left pictures above.
3. "having a prominent anterior proximal hook-like projection." This refers to the pubic peduncle being longer and more ventrally projecting in Epichirostenotes, enclosing the obturator notch more. Note the two right pictures above also differ in the length and angle of the ventral portion of the pubic peduncle.
Also notice the other differences within Tyrannosaurus. The lower right pic has a narrower body proximal to the obturator process. It also has a longer and more rounded proximodorsal process. The two right pics have curved shafts compared to those on the left.
So it's a very awkward situation. I'd bet curriei really is a distinct species from pergracilis, if only because that seems to be true for other theropods compared between those formations (though the published evidence for this is usually as tenuous as the current case). But the known remains don't justify that anatomically, and whether curriei is more closely related to Chirostenotes than Elmisaurus or Hagryphus is basically unknowable. If it is closer to pergracilis, then I could see only the most extreme splitter keeping them as separate species based on known remains, let alone genera. Maybe CM 78000 and 78001 will help sort things out, and it would have been prudent to wait until Sues and Lamanna finish describing them before dealing with the taxonomy of ROM 43250. I think for now I'll just call ROM 43250 Chirostenotes? curriei and keep the Chirostenotes OTU intact that way. There's no evidence against it at least, even though it's not necessarily true. And it's not unheard of for other taxa in the matrix. The Struthiomimus OTU has always included both the Dinosaur Park S. altus and the unnamed Horseshoe Canyon species represented by AMNH 5257 and exceptionally complete RTMP 90.26.1. If someone were to name the latter "Epistruthiomimus unnecessari" based on Longrich's comment the metacarpus is more slender, would we have to break up our Struthiomimus OTU? Note that like the caenagnathid situation, the described differences between species are few and of debatable significance, while there has been no study showing they form a monophyletic group based on apomorphies. So the facts are the same, but the new genus for ROM 43250 just complicates matters.
 |
| Ischia previously referred to Chirostenotes (from Sues, 1997). A- RTMP 79.20.1, which is still placed in Chirostenotes pergracilis. B- ROM 43250, now the holotype of Epichirostenotes curriei. The only other shared elements are ilial fragments and a sacrum for which no differences have been noted. |
How should we now code Chirostenotes? The genus has been used in many analyses, including the Theropod Working Group matrix, which I've been correcting for the description of a new paravian. In that matrix, it is apparently based on a combination of the Chirostenotes, Macrophalangia and Caenagnathus holotypes, as well as partial skeletons RTMP 79.20.1 (Currie and Russell, 1988) and ROM 43250. It wouldn't be too important, except ROM 43250 is our only described source for coding Chirostenotes' maxilla, braincase, cervicals, dorsals, caudals and pubis. So if we leave it out, we're losing a lot of information. And without a more complete caenagnathid to code, and few overlapping elements, there's a large chance it won't group with Chirostenotes, so could harm oviraptorosaur topology (like coding Caenagnathus separately did for Senter, 2007). But combining it with Chirostenotes could be misleading once Elmisaurus and Hagryphus are added, since nothing argues ROM 43250 isn't closer to these latter genera. While ROM 43250 isn't comparable to either, a second specimen from the same formation (metatarsal II CMN 9570, unmentioned by Sullivan et al.) is distinctive from Elmisaurus due to its lack of fusion and straight distal end. These are plesiomorphies though, so do not argue strongly for its referral to Chirostenotes. And the metatarsal isn't comparable to ROM 43250 anyway, so any referral to Epichirostenotes is based purely on size and provenence. But nothing argues the Horseshoe Canyon specimens aren't Chirostenotes either, since so far the apomorphies of Chirostenotes are only known from the mandible (assuming Caenagnathus collinsi is properly synonymized) and other parts of the metatarsus. The minor differences between the ischia of Epichirostenotes and RTMP 79.20.1 are just like those found between individuals of Tyrannosaurus rex, Microraptor zhaoianus and other species. The distinction boils down to size (which could easily be ontogenetic) and provenence. Now this doesn't make Epichirostenotes a nomen dubium, because the braincase and maxilla are certainly distinct from comparable named theropods, it's just that no other named caenagnathid can be compared for the most part.
 | |
| Tyrannosaurus rex ischia to show interspecific variation. Left- FMNH PR2081 left and right (from Brochu, 2003); Right top- CM 9380 (from Osborn, 1906); Right bottom- AMNH 5027 (from Osborn, 1916). |
Note how the Tyrannosaurus ischial variation mirrors that between Chirostenotes and Epichirostenotes. The latter's ischial diagnosis is-
1. "Ischium long and expanded posteriorly; broad behind obturator process." There is no known comparative length difference, since Epichirostenotes doesn't preserve an ilium and Chirostenotes doesn't preserve a pubis. The posterior expansion and breadth posterior to the obturator process refers to the greater depth in Epichirostenotes. As seen most distinctly between the upper right and lower left pictures above.
2. "obturator process expanded and triangular." This refers to the greater depth of the obturator process and non-rectangular tip in Epichirostenotes. As seen between the two left pictures above.
3. "having a prominent anterior proximal hook-like projection." This refers to the pubic peduncle being longer and more ventrally projecting in Epichirostenotes, enclosing the obturator notch more. Note the two right pictures above also differ in the length and angle of the ventral portion of the pubic peduncle.
Also notice the other differences within Tyrannosaurus. The lower right pic has a narrower body proximal to the obturator process. It also has a longer and more rounded proximodorsal process. The two right pics have curved shafts compared to those on the left.
So it's a very awkward situation. I'd bet curriei really is a distinct species from pergracilis, if only because that seems to be true for other theropods compared between those formations (though the published evidence for this is usually as tenuous as the current case). But the known remains don't justify that anatomically, and whether curriei is more closely related to Chirostenotes than Elmisaurus or Hagryphus is basically unknowable. If it is closer to pergracilis, then I could see only the most extreme splitter keeping them as separate species based on known remains, let alone genera. Maybe CM 78000 and 78001 will help sort things out, and it would have been prudent to wait until Sues and Lamanna finish describing them before dealing with the taxonomy of ROM 43250. I think for now I'll just call ROM 43250 Chirostenotes? curriei and keep the Chirostenotes OTU intact that way. There's no evidence against it at least, even though it's not necessarily true. And it's not unheard of for other taxa in the matrix. The Struthiomimus OTU has always included both the Dinosaur Park S. altus and the unnamed Horseshoe Canyon species represented by AMNH 5257 and exceptionally complete RTMP 90.26.1. If someone were to name the latter "Epistruthiomimus unnecessari" based on Longrich's comment the metacarpus is more slender, would we have to break up our Struthiomimus OTU? Note that like the caenagnathid situation, the described differences between species are few and of debatable significance, while there has been no study showing they form a monophyletic group based on apomorphies. So the facts are the same, but the new genus for ROM 43250 just complicates matters.
Friday, July 15, 2011
Testing Harding's idea- Constraining topologies based on adding taxa in stratigraphic order
On the DML, Grant Harding proposed an idea. Run cladistic analyses using only the earliest taxa, then sequentially add later taxa, but each time constrain the topology to match the trees found using only earlier taxa. I tried it using my corrected TWG matrix, which at the moment covers all the taxa and characters up to Hwang et al. (2004).
So for example, the first run included only Jurassic taxa- Sinraptor, Allosaurus, Ornitholestes, Compsognathus and Archaeopteryx. The tree found was (Sinraptor,Allosaurus(Ornitholestes(Compsognathus,Archaeopteryx))), which is standard. It disagrees with the total data tree in having Ornitholestes and Compsognathus switched, presumably because of the lack of ornithomimosaurs, therizinosaurs, other compsognathids, etc.. If this were a more complete analysis, you'd have Haplocheirus, scansoriopterygids, Pedopenna, Lori and Anchiornis there as well as all the non-maniraptoriform Jurassic coelurosaurs.
I then added the taxa which lived slightly later- Shenzhousaurus, Incisivosaurus and Sinovenator. I constrained the analyses to only find trees agreeing with the relationships found using the Jurassic taxa. This resulted in- (Sinraptor,Allosaurus(Ornitholestes(Compsognathus(Shenzhousaurus(Incisivosaurus(Sinovenator,Archaeopteryx)))))). This matches the total tree besides the point noted above. Again, a more complete analysis would have Dilong, Kinnareemimus, Nqwebasaurus, Graciliraptor, Mei, Sinusonasus, "Eoconfuciusornis" and maybe a few other birds.
In any case, I added the following groups next-
- Harpymimus, Pelecanimimus.
- Utahraptor.
- Caudipteryx, Confuciusornis, Sinornithosaurus, Huaxiagnathus, Sinosauropteryx.
- Deinonychus, Microvenator, Sinornithoides, Alxasaurus, Microraptor, IGM 100/44.
- Garudimimus, Segnosaurus, Erlikosaurus, Achillobator.
Then I hit a snag. The next group was Patagonykus, Unenlagia comahuensis and U? paynemili. None of these taxa has a definite position in the cladogram when constrained to match the topology of the previous taxa. The Unenlagia species are both some kind of paravian, while Patagonykus is at least as derived as compsognathids, but is not an ornithomimosaur, therizinosaur, avialan or eudromaeosaur. And there's no way to constrain a tree to include uncertain relationships like these. The only taxon left to include before the big end Campanian-Maastrichtian group was Alvarezsaurus, but it didn't help, since it emerges as a compsognathid-grade taxon without affecting Patagonykus' relationships. So that's a problem with this kind of analysis. The same is true of the many early fragments that show character combinations unique to certain clades (e.g. Jurassic dromaeosaurid teeth with high DSDIs). These are normally useless to include in analyses since they don't have different codings than more complete later specimens, but in this variety of analysis, they'd be potentially useful early on but would form polytomies later if not deleted.
Another issue is that many taxa have unconstrained ages, and adding these in order of their earliest possible age, mean age, etc. is going to likely change the results.
To get a finished result of sorts, I simply did not constrain the position of Patagonykus, Unenlagia or U? paynemili in the final run with Campanian-Masstrichtian taxa, since they come out somewhere within their polytomies in the total data analysis anyway, though I did still force Alvarezsaurus to be compsognathid-grade. The end result was a tree 19 steps longer than the unconstrained tree. The primary differences are-
- Alvarezsaurus is by compsognathids due to its position before parvicursorines were added.
- Ornitholestes (thanks to the Jurassic analysis), therizinosaurs (thanks to Alxasaurus when analyzed with basal ornithomimosaurs) and Patagonykus+parvicursorines (probably due to following therizinosaurs) are outside Maniraptoriformes.
- Pelecanimimus is an ornithomimosaur due to alvarezsaurids not being included until after it was added.
- Microvenator is a basal maniraptoran due to the absence of more complete caenagnathoids until later runs.
- Caudipteryx is an oviraptorosaur thanks to clading with Incisivosaurus early on.
- Troodontids are paraphyletic to dromaeosaurids instead of to birds (except that Sinovenator is still an avialan), and Microraptor is a basal dromaeosaurid instead of a basal avialan.
So some results are closer to the consensus while others aren't. I suppose the real test will be to see if any of these relationships are found when I add more taxa and characters to the complete analysis.
So for example, the first run included only Jurassic taxa- Sinraptor, Allosaurus, Ornitholestes, Compsognathus and Archaeopteryx. The tree found was (Sinraptor,Allosaurus(Ornitholestes(Compsognathus,Archaeopteryx))), which is standard. It disagrees with the total data tree in having Ornitholestes and Compsognathus switched, presumably because of the lack of ornithomimosaurs, therizinosaurs, other compsognathids, etc.. If this were a more complete analysis, you'd have Haplocheirus, scansoriopterygids, Pedopenna, Lori and Anchiornis there as well as all the non-maniraptoriform Jurassic coelurosaurs.
I then added the taxa which lived slightly later- Shenzhousaurus, Incisivosaurus and Sinovenator. I constrained the analyses to only find trees agreeing with the relationships found using the Jurassic taxa. This resulted in- (Sinraptor,Allosaurus(Ornitholestes(Compsognathus(Shenzhousaurus(Incisivosaurus(Sinovenator,Archaeopteryx)))))). This matches the total tree besides the point noted above. Again, a more complete analysis would have Dilong, Kinnareemimus, Nqwebasaurus, Graciliraptor, Mei, Sinusonasus, "Eoconfuciusornis" and maybe a few other birds.
In any case, I added the following groups next-
- Harpymimus, Pelecanimimus.
- Utahraptor.
- Caudipteryx, Confuciusornis, Sinornithosaurus, Huaxiagnathus, Sinosauropteryx.
- Deinonychus, Microvenator, Sinornithoides, Alxasaurus, Microraptor, IGM 100/44.
- Garudimimus, Segnosaurus, Erlikosaurus, Achillobator.
Then I hit a snag. The next group was Patagonykus, Unenlagia comahuensis and U? paynemili. None of these taxa has a definite position in the cladogram when constrained to match the topology of the previous taxa. The Unenlagia species are both some kind of paravian, while Patagonykus is at least as derived as compsognathids, but is not an ornithomimosaur, therizinosaur, avialan or eudromaeosaur. And there's no way to constrain a tree to include uncertain relationships like these. The only taxon left to include before the big end Campanian-Maastrichtian group was Alvarezsaurus, but it didn't help, since it emerges as a compsognathid-grade taxon without affecting Patagonykus' relationships. So that's a problem with this kind of analysis. The same is true of the many early fragments that show character combinations unique to certain clades (e.g. Jurassic dromaeosaurid teeth with high DSDIs). These are normally useless to include in analyses since they don't have different codings than more complete later specimens, but in this variety of analysis, they'd be potentially useful early on but would form polytomies later if not deleted.
Another issue is that many taxa have unconstrained ages, and adding these in order of their earliest possible age, mean age, etc. is going to likely change the results.
To get a finished result of sorts, I simply did not constrain the position of Patagonykus, Unenlagia or U? paynemili in the final run with Campanian-Masstrichtian taxa, since they come out somewhere within their polytomies in the total data analysis anyway, though I did still force Alvarezsaurus to be compsognathid-grade. The end result was a tree 19 steps longer than the unconstrained tree. The primary differences are-
- Alvarezsaurus is by compsognathids due to its position before parvicursorines were added.
- Ornitholestes (thanks to the Jurassic analysis), therizinosaurs (thanks to Alxasaurus when analyzed with basal ornithomimosaurs) and Patagonykus+parvicursorines (probably due to following therizinosaurs) are outside Maniraptoriformes.
- Pelecanimimus is an ornithomimosaur due to alvarezsaurids not being included until after it was added.
- Microvenator is a basal maniraptoran due to the absence of more complete caenagnathoids until later runs.
- Caudipteryx is an oviraptorosaur thanks to clading with Incisivosaurus early on.
- Troodontids are paraphyletic to dromaeosaurids instead of to birds (except that Sinovenator is still an avialan), and Microraptor is a basal dromaeosaurid instead of a basal avialan.
So some results are closer to the consensus while others aren't. I suppose the real test will be to see if any of these relationships are found when I add more taxa and characters to the complete analysis.
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