Friday, March 24, 2017

Ornithoscelida Lives!

Back in 2010, I wrote a post about how surprisingly theropod-like Heterodontosaurus was, and ended by stating "Not that I'm saying Saurischia is wrong, I just think we can get so comfortable with an idea that we stop looking at alternatives."  This week I was surprised to learn of a new paper by Baron, Norman and Barrett (2017) which uses a phylogenetic analysis to recover that heterodox ornithichian+theropod topology.  In particular, they recover herrerasaurids as basal sauropodomorphs, while ornithischians and theropods are joined together in the resurrected clade Ornithoscelida*.   Vindication?

* Baron et al. redefine some clades (see below), but here I'm using the traditional concepts since I dislike some of their definitions.

"Reduced strict consensus tree of [Baron et al.'s] main
analysis ..., after the exclusion of Saltopus elginensis, Agnosphitys
cromhallensis, Eucoelophysis baldwini
and Diodorus scytobrachion." (after Baron et al., 2017)

Well, let's see how good the study is first.  I should preface this by noting that while traditional Saurischia has been recovered in every single previously published numerical cladistic analysis, most of these were crap by today's standards.  The only exceptions are really Nesbitt et al.'s (2009) Tawa analysis, which used 30 dinosauromorphs and 315 characters, Ezcurra's (2006) Eucoelophysis analysis that used 26 dinosauromorphs and 287 characters, and Cabreira et al's Ixalerpeton/Buriolestes analysis that used 42 dinosauromorphs and 256 characters  Yates' is large but focuses mainly on sauropodomorphs, and others are small (11 taxa, 98 characters for Langer and Benton, 2006; 18 taxa, 139 characters for Martinez et al., 2011; etc.).  Baron et al. include 72 dinosauromorphs and 456 characters, so by that measure is much better.

It also uses only species-level OTUs and properly orders characters, so that's good.  And it has excellent taxon sampling, including basically every basal dinosauromorph except Ixalerpeton, Buriolestes and Isaberrysaura (which were presumably published too late) and a couple fragmentary taxa (Teyuwasu, Alwalkeria) [Edit: I did not realize at the time it doesn't have Daemonosaurus, Scutellosaurus or rhodesiensis, and less importantly the fragmentary Chromogisaurus.  The absence of Daemonosaurus is particularly odd given it's somewhat heterodontosaury features...].  In particular, ornithischians are well represented unlike any prior analysis (14 taxa vs. 5 in Nesbitt et al., 3 in Ezcurra, and 5 in Cabreira et al.).  I'd say sauropodomorphs are almost over-represented, except that with this heterodox topology, it might have been a good thing to include even the basal gravisaurs they did just in case those ended up being the earliest diverging branches.  Sauropodomorpha has the standard topology in their trees btw, except Eoraptor is recovered as a theropod.

The next thing to check is if this result is robust, and at a whopping 20 extra steps needed to recover Saurischia, is it ever*!  For comparison, the original TWG matrix needs 22 more steps to recover Bullatosauria and 23 steps to get Russell and Dong's (1994) crazy topology.  They tested this in an IMO un-ideal way, by constraining all 42 saurischians to be in an exclusive clade.  Would have been better to just use a backbone of e.g. (Euparkeria, Lesothosaurus (Plateosaurus, Coelophysis), in case e.g. herrerasaurids aren't dinosaurs.  Baron et al. also deleted various sets of taxa but found "the recovery of Ornithoscelida as a monophyletic clade, as well as Sauropodomorpha+Herrerasauridae (Saurischia, new definition), occurred in all of these analyses, regardless of which taxa were included or excluded."  So that's impressive.  They also tested Dimorphodon as an alternate outgroup (the defaults are Euparkeria and Postosuchus which is wrongly called an ornithosuchid; an ornithosuchid would have been better ironically, since they're the first branching pseudosuchian group if parasuchians aren't), and found the same topology.

* To those who noted the 66% bootstrap for Ornithoscelida (Cerny on the DML, *cough cough*), realize that with very incomplete taxa like most fossils, bootstrap percentages mean very little.  It's easy for a fragmentary taxon like Nyasasaurus to fall inside Ornithoscelida, for example.  And every time it does, that lowers the bootstrap score.

The Lori analysis if limited to the taxonomic scope of Barron et al. (2017).  The topology changed from my last post after the inclusion of non-dinosauromorph outgroups, but is still unlike either the traditional topology or Baron et al.'s.  Instead, it features non-dinosaurian herrerasaurids and a Phytodinosauria with paraphyletic sauropodomorphs.

Of course, I just posted about recovering a heterodox dinosaur topology using the Lori matrix, which has more characters than even Baron et al.'s (481 are parsimony informative for basal dinosauromorphs) and 71 dinosauromorphs within Baron et al.'s scope (more coelophysoids, less plateosaurs).  Yet I don't trust that part of the Lori tree.  That's because the Lori matrix wasn't designed to sort basal dinosauromorphs, so lacks many of the proposed characters that support traditional clades.  Is Baron et al.'s similar?  To determine that, we need to check and see if the characters traditionally used to support Saurischia are included.  Of the 28 characters recovered as supporting the clade in Nesbitt et al.'s study, 27 are included by Baron et al., and one is even (correctly) divided into two characters since it was a composite.  The one excluded character ("Femur, surface between the lateral condyle and crista tibiofibularis on the distal surface: smooth (0); deep groove (1)") doesn't actually support Saurischia anyway.  Cabreira et al.'s analysis was published after Baron et al. had done their analysis, so the latter can't be faulted for not including all of their characters.  Ironically, they also found 28 characters, but 16 of these are different than Nesbitt et al.'s.  Five of these sixteen are not in Baron et al.'s matrix, which considering the 20 steps needed to get Saurischia there, aren't a help even assuming coding accuracy.  Finally, Ezcurra had 39 characters of which 23 aren't used in the prior two, and 9 of these aren't in Baron et al.'s.  Even adding these nine to the preceding five, it doesn't match the twenty.  So I'd say Baron et al. did a decent job testing saurischian monophyly character-wise, and that adding published suggested saurischian characters aren't going to overturn Ornithoscelida.  For comparison, only 5 of Nesbitt et al.'s characters are in the Lori matrix and only 5 of Cabreira et al.'s new ones and 5 of Ezcurra's new ones, though the Lori topology eliminates Saurischia by recovering Phytodinosauria instead.

So far it's looking very good for Ornithoscelida.  However- here are some caveats.  First, Baron et al.'s matrix has some correlated characters.  Examples are "Third cervical vertebra, centrum length: 0, subequal to the axis centrum; 1, longer than the axis centrum (Gauthier, 1986; Langer and Benton, 2006; Nesbitt, 2011)" compared to "Elongation of cervical centrum (cervicals 3–5): 0, less than 3.0 times the centrum height, 1, 3.0-4.0 times the centrum height, 2, >4.0 times the centrum height (Upchurch, 1998; Pol et al., 2011b). ORDERED"; "Digit I with metacarpal: 0, longer than the ungual; 1, subequal or shorter than the ungual (Sereno, 1999; Langer and Benton, 2006; Nesbitt, 2011)" compared to "Manual digit I, first phalanx: 0, is not the longest non-ungual phalanx of the manus; 1, is the longest non-ungual phalanx of the manus (Gauthier, 1986; Langer and Benton, 2006; Nesbitt, 2011)", and "Deltopectoral crest: 0, less than 30% the length of the humerus; 1, more than 30% the length of the humerus (Bakker and Galton, 1974; Benton, 1990; Juul, 1994; Novas, 1996; Benton, 1999)" compared to "Humerus, apex of deltopectoral crest situated at a point corresponding to: 0, less than 30% down the length of the humerus; 1, more than or equal to 30% down the length of the humerus but less than 50% down the length of the humerus; 2, more than 50% down the length of the humerus (modified from Bakker and Galton, 1974; Benton, 1990; Juul, 1994; Novas, 1996; Benton, 1999, Nesbitt, 2011)."  There are also no polymorphies in the matrix, which is impossible in reality with taxa like Coelophysis and Plateosaurus known from tons of variable individuals.  So it's not an excellent character list.

Second, despite the great taxon sample, Buriolestes would seem to be a most relevant taxon to include, being a supposed basalmost sauropodomorph that is very theropod-like.  Maybe it'd fall out as a theropod in Baron et al.'s trees, since Eoraptor does, but who knows until it's added.  Another issue is that no neotheropods are included, unlike Nesbitt et al.'s and Ezcurra's matrices.  If coelophysoid-grade taxa are paraphyletic, that's fine.  But if Dilophosaurus, Cryolophosaurus, Dracovenator and (?)Sinosaurus are coelophysoids, we're missing a whole side of the avepod tree.  And that could be important since heterodontosaurids seem particularly similar to coelophysoids among avepods.  So add Ceratosaurus, Elaphrosaurus, Piatnitzkysaurus and Monolophosaurus?

Also, how accurate is the coding?  There's no premade TNT file and the matrix is presented in a way that without copy-pasting it's basically impossible to check codings.  But the last character is an obvious one to code- "Singular and unbranched filamentous integumentary structures covering, or partially covering, the outer body: 0, absent; 1, present. NEW".  Depressingly, the following taxa are coded as lacking filamentous integument- Saltopus, Silesaurus, Lewisuchus, Pisanosaurus, Fruitadens, Abrictosaurus, Heterodontosaurus, Eocursor, Lesothosaurus, Scelidosaurus, Emausaurus, Agilisaurus, Hexinlusaurus, Jeholosaurus, Dracoraptor, Massospondylus carinatus, Guaibasaurus, Unaysaurus, Plateosaurus, Efraasia, Pantydraco, Herrerasaurus, Eodromaeus, Coelophysis, Eoraptor, Procompsognathus, Euparkeria, Dilophosaurus, Sinosaurus, Pampadromeus and Dimorphodon.  Obviously none of these taxa preserve integument (does Dimorphodon preserve pterofuzz?), excluding osteoderms in a few.  So this is a massive and worthless miscoding (only Tianyulong preserves filaments among the OTUs and none is known to lack them).  I can only hope this misrepresents the coding accuracy of the matrix.

So where does this leave us?   Honestly, I'm rather strongly in favor of Ornithoscelida.  For all my caveats, I could say the same for at least Nesbitt et al.'s matrix.  I haven't examined Ezcurra's or Cabreira et al.'s in depth.  Also, Baron et al. did include a lot of new ornithischian info, both taxon- and coding-wise.  Given the apparent robusticity of the result, the size of the matrix, and the coverage of proposed saurischian characters, any analysis that aims to disprove Ornithoscelida needs to use this study as its base.

Holotype and referred specimen of Nyasasaurus, Middle Triassic massopod? (after Nesbitt et al., 2013)

One other unexpected result of this analysis is the position of Nyasasaurus.  In its unofficial pre-cladistic days, considered a prestosuchid or thecodontosaurid (heh, what are those? ;) ), Nesbitt et al. (2013) recovered it as closer to Dinosauria than silesaurids, but outside examined ornithischians, sauropodomorphs and Tawa+avepods.  Well, Baron et al. recovered it as... a massopod sauropodomorph outside Anchisauria.  In the Middle Triassic.  Which would be weird.  Oddly enough, Nyasasaurus emerges sister to Plateosaurus in the Lori result.  Hmm...

FINALLY (long post), Baron et al. redefine several clades given their new topology.  This is where I have some serious issues.

First, Dinosauria becomes "The least inclusive clade that includes Passer domesticus, Triceratops horridus and Diplodocus carnegii."  I'm generally of the Kischlat school of phylogenetic definitions, where only taxa originally considered part of the clade (or not) are used.  But sauropodomorphs weren't included when Dinosauria was coined, so I'll make an exception here.  Since Sauropodomorpha is based on Sauropoda, and Sauropoda was based on Atlantosaurus, Apatosaurus, Morosaurus and Diplodocus, I'm fine with Diplodocus being used (better than the standard Saltasaurus).  But of course I'm a defender of D. longus remaining the type species (and submitted a Comment to the BZN over it), so would use it instead of D. carnegii, which was unknown to Marsh.  Similarly, I don't like making birds dinosaurs by fiat, so would rather use Allosaurus fragilis for the theropod specifier since it was what Marsh based Theropoda on in 1881.  For ornithischians, I follow Kischlat's arguments that Stegosaurus armatus is ideal since Triceratops was unknown to Seeley in 1887.  So I'd suggest-
The least inclusive clade that includes Allosaurus fragilis, Stegosaurus armatus and Diplodocus longus.

Ornithoscelida is defined as "The least inclusive clade that includes Passer domesticus and Triceratops horridus."  It's not a great name for the clade, because Huxley included sauropodomorphs in the group- Thecodontosaurus as a scelidosaurid and Cetiosaurus as an iguanodontid.  Huxley's point was to use it to relate all dinosaurs with Compsognathus, which was not considered dinosaurian at the time.  But since there are honestly no preexisting names for this concept, and this is a landmark paper, we might as well accept it.  Just as in the above example though, birds were never considered ornithoscelidans, and ceratopsians were still unknown back in 1870.  As Huxley's dinosaurian families were Megalosauridae, Scelidosauridae and Iguanodontidae, I'd suggest the following definition-
The least inclusive clade that includes Megalosaurus bucklandii and Iguanodon bernissartensis.

Saurischia is defined as "The most inclusive clade that contains Diplodocus carnegii but not Triceratops horridus", which is easily the worst definition of the bunch.  A clade of just herrerasaurids and 1990's+ standard sauropodomorphs is NOT Saurischia.   Seeley clearly constructed Saurischia to combine theropods and sauropods based on e.g. pelvic structure and axial pneumaticity.  All proposed definitions either self destruct in this topology or ironically include only theropods.  So I say if Ornithoscelida is a thing, then Saurischia just goes away.

Theropoda is defined as "The most inclusive clade that contains Passer domesticus but not Diplodocus carnegii or Triceratops horridus."  Again, birds shouldn't be theropods by definition, and neither Mesozoic taxon was known when Marsh named Theropoda.  Using the logic from the above examples, I'd suggest- The most inclusive clade that contains Allosaurus fragilis but not Diplodocus longus or Stegosaurus armatus.

Ornithischia is defined as "The most inclusive clade that contains Triceratops horridus but not Passer domesticus or Diplodocus carnegii."  So again, I would suggest- The most inclusive clade that contains Stegosaurus armatus but not Allosaurus fragilis or Diplodocus longus.

Sauropodomorpha is defined as "The most inclusive clade that contains Diplodocus carnegii but not Triceratops horridus, Passer domesticus or Herrerasaurus ischigualastensis."  This is the second most troubling definition because there's no reason to bring herrerasaurids in to it.  Indeed, Herrerasaurus was regarded AS a sauropodomorph by basically every author after its initial description and before the mid 80's cladistic revolution.  I even state on the Database "While these historical comparisons of Herrerasaurus to sauropodomorphs were generally vague, unpublished analysis suggests herrerasaurids can be moved to a position as basalmost sauropodomorphs without adding many extra steps" based on my experiments with a partially corrected Nesbitt et al. dataset.  Just regard herrerasaurids as basal sauropodomorphs in this topology and use the definition- The most inclusive clade that contains Diplodocus longus but not Stegosaurus armatus or Allosaurus fragilis.

The take away- I provisionally accept Ornithoscelida as better supported than Saurischia, but just get rid of the latter in this topology and let herrerasaurids be sauropodomorphs.

As a last question- what does this say about Chilesaurus?  It wasn't included, but is the prime example of an ornithischian-theropod cross after all....

References- Russell and Dong, 1994. The affinities of a new theropod from the Alxa Desert, Inner Mongolia, People’s Republic of China. Canadian Journal of Earth Sciences. 30(10), 2107-2127.

Ezcurra, 2006. A review of the systematic position of the dinosauriform archosaur Eucoelophysis baldwini Sullivan & Lucas, 1999 from the Upper Triassic of New Mexico, USA. Geodiversitas. 28(4), 649-684.

Langer and Benton, 2006. Early dinosaurs: A phylogenetic study. Journal of Systematic Palaeontology. 4(4), 309-358. 

Nesbitt, Smith, Irmis, Turner, Downs and Norell, 2009. A complete skeleton of a Late Triassic saurischian and the early evolution of dinosaurs. Science. 326, 1530-1533.

Martinez, Sereno, Alcober, Columbi, Renne, Montanez and Currie, 2011. A basal dinosaur from the dawn of the dinosaur era in Southwestern Pangaea. Science. 331, 206-210.

Nesbitt, Barrett, Werning, Sidor and Charig, 2013. The oldest dinosaur? A Middle Triassic dinosauriform from Tanzania. Biology Letters. 9(1), 20120949.

Cabreira, Kellner, Dias-da-Silva, da Silva, Bronzati, Marsola, Muller, Bittencourt, Batista, Raugust, Carrilho, Brodt and Langer, 2016. A unique Late Triassic dinosauromorph assemblage reveals dinosaur ancestral anatomy and diet. Current Biology. 26(22), 3090-3095.

Baron, Norman and Barrett, 2017. A new hypothesis of dinosaur relationships and early dinosaur evolution. Nature. 543, 5601-506.


Wednesday, March 1, 2017

Basal Dinosauromorpha in the Lori tree

Hi everyone!  Sorry for being away so long.  As an interesting experiment, after adding every decently preserved theropod to the Lori matrix, I added every decently preserved basal dinosauromorph as well.  As you all know, the Lori matrix is basically every TWG analysis through 2012 combined together with a complete taxon sample.  This yields 700 characters designed to sort out coelurosaurian phylogeny, excluding crown Aves, tyrannosaurids (fixed with Brusatte's later additions), enantiornithines and caenagnathoids.  Only a few non-coelurosaurian theropods have ever been included in TWG analyses- Sinraptor dongi and Allosaurus as outgroups from the beginning, with a few authors adding Coelophysis, Dilophosaurus and Monolophosaurus as well.  It actually performs pretty well at approximating avepod phylogeny, but once we get to the base of Dinosauromorpha, this happens-

Initial majority rule consensus of the non-avepod section of the Lori tree.  Running a traditional TBR search from this shows that Nyasasaurus, Lagosuchus, Teyuwasu and Dromomeron gregorii all have uncertain positions, as does Pisanosaurus within Neornithischia.  Also the pairing of Guaibasaurus and Saturnalia within their basal phytodinosaur clade lowers to 97%.  TNT crashed before I could screen capture the reduced consensus however.

Notice how Peters-ian it is.  Not that it has a similar topology to Peters' Large Reptile Tree, though there are a few similarities (Phytodinosauria, ornithischian Chilesaurus, Buriolestes and Marasuchus as theropods...).  Indeed, our ornithischian topologies are completely different.  No, what I mean is that while there are some consensus clades recovered (in my case Ornithischia, Scelidosaurus+Huayangosaurus, the Agilisaurus+ clade, herrerasaurids, avepods), it's largely a novel tree with newly paraphyletic groups (e.g. Silesauridae) and misplaced taxa (e.g. Diodorus and Dromomeron romeri in Ornithischia; Eucoelophysis and Dromomeron gregorii in a clade of basal sauropodomorphs).  Like Peters' trees, mine actually has a bigger taxon sample than prior basal dinosauromorph analyses.  Superior to Peters' analyses, I use far more characters than prior analyses (700 vs. 228 in Peters, online 2016; 315 in Nesbitt et al., 2009; 256 in Cabreira et al., 2016; 139 in Martinez et al., 2011; 221 in Butler et al., 2008; 255 in Boyd, 2015; ~370 characters in the newest version of Yates' basal sauropodomorph analysis), and these are formed well and the taxa coded accurately.

Yet despite the latter facts, I wouldn't even think of claiming e.g. Tawa and Daemonosaurus aren't dinosaurs, or that sauropodomorphs are diphyletic and partly paraphyletic to ornithischians.  This is because I haven't included the characters supporting the consensus topology in most cases, so I haven't really tested those ideas.  Conversely, it may be that some TWG characters actually do overwealm those used in basal dinosauromorph analyses to support novel relationships.  But we'll never know that until we combine the character sets.

I do find it interesting that Chilesaurus falls out basally by ornithischians, and not all that far away from the Tawa+Daemonosaurus clade I proposed it belonged to in my last post on the taxon.  Certainly it never clades with basal tetanurans, and still emerges as a basal alvarezsaur if it's an avepod.  Of course in the Lori tree, it emerges within a paraphyletic derived Thyreophora which is itself the basalmost group of ornithischians within a paraphyletic Sauropodomorpha.  So the combination of character states there probably doesn't reflect the combination of character states in a traditional basal Ornithischia, where they're sister to Saurischia or various silesaurids.  Ideally without adding the hundreds of characters involves with this part of the tree, I could constrain a traditional topology here, but that's assuming the traditional topology is correct.  Honestly there's no easy way to test such a controversial taxon as Chilesaurus.

Finally, I'd like to mention the excellent new paper by Marjanovic and Laurin (2016), which is basically a published version of what I do on the Evaluating Phylogenetic Analyses portion of the Database, targeting an analysis of basal tetrapods.  It's incredibly detailed and finds "thousands of suboptimal scores" (I'd like to know the percentage changed, but it's not listed AFAIK) and a very different topology from the original.

References- Butler, Upchurch and Norman, 2008. The phylogeny of the ornithischian dinosaurs. Journal of Systematic Palaeontology, 6(1), 1-40.

Nesbitt, Smith, Irmis, Turner, Downs and Norell, 2009. A complete skeleton of a Late Triassic saurischian and the early evolution of dinosaurs. Science. 326, 1530-1533.

Martinez, Sereno, Alcober, Columbi, Renne, Montanez and Currie, 2011. A basal dinosaur from the dawn of the dinosaur era in Southwestern Pangaea. Science. 331, 206-210.

Boyd, 2015. The systematic relationships and biogeographic history of ornithischian dinosaurs. PeerJ. 3:e1523.

Cabreira, Kellner, Dias-da-Silva, da Silva, Bronzati, Marsola, Muller, Bittencourt, Batista, Raugust, Carrilho, Brodt and Langer, 2016. A unique Late Triassic dinosauromorph assemblage reveals dinosaur ancestral anatomy and diet. Current Biology. 26(22), 3090-3095.

Marjanovic and Laurin, 2016. Reevaluation of the largest published morphological data matrix for phylogenetic analysis of Paleozoic limbed vertebrates. PeerJ Preprints. 4:e1596v2.

Wednesday, August 31, 2016

The Monster of Minden published at last

Those of you who frequented the Dinosaur Mailing List in the early 2000s might remember references to a supposedly gigantic German theropod- Das Monster von Minden.  After a few news stories, it was quickly forgotten until an abstract published last year (Rauhut et al., 2015) confirmed it as a new megalosaurid.  As of today it has been officially published and described as Wiehenvenator albati (Rauhut et al., 2016). 

Skull of Wiehenvenator albati holotype (WMN P27275, P27504, P27457, P27477, P27470, P27461, P27462 and P27466), scale equals 100 mm (after Rauhut et al., 2016).
The description is generally excellent, with multiple colored high resolution views of each element.  Anatomically, Weihenvenator is basically Torvosaurus, so is not that intriguing.  Rauhut et al. are the first I know to alter Carrano et al.'s basal tetanurine analysis however- "Several character definitions of the original list of Carrano et al. (2012), especially of cranial characters, were revised and taxa recoded correspondingly." "A complete documentation of the changes in character definition and character codings will be presented elsewhere (Rauhut and Pol, in prep.)."  So that's interesting.  They also "added the basal tyrannosaur Guanlong to the matrix in order to improve taxon and character sampling in coelurosaurs", which is good but not nearly enough to fix that issue.  They also deleted "the Chinese theropod Leshansaurus, as neither Carrano et al. (2012) nor we studied this taxon personally, and the published description (Li et al., 2009) is in Chinese, so codings could only be based on the sparse illustrations."  The illustrations are actually rather good, and the Chinese can be translated via Google Translate, so I'd argue against this.  In any case, their resulting tree matches Carrano et al.'s except Cryolophosaurus and Sinosaurus are outside Neotheropoda (their Averostra), Chuandongocoelurus is in a trichotomy with ceratosaurs and tetanurines, and Monolophosaurus is closer to megalosaurians than piatnitzkysaurids, all in Megalosauroidea.  Several taxa later added to the Carrano et al. matrix are not analyzed (e.g. Chilesaurus, Sciurumimus), which I think would be important when considering basal tetanurine phylogeny.  Rauhut was an author of Sciurumimus after all.  Finally, their informal supertree in figure 26 list "Anchiornithosaurs" in quote marks as a group sister to Avialae, which is... interesting.

Phylogeny found by Rauhut et al. (2016) after a posteriori exclusion of Streptospondylus using a modified version of Carrano et al.'s basal tetanurine matrix (modified after Rauhut et al., 2016).
But what about its size?  That was the big thing about the Minden Monster back in the day, with some paleontologists estimating its length as high as ~15 m (http://www.miketaylor.org.uk/dino/faq/s-size/predator/index.html#9).  Back in 2001 I estimated its size as ~7-8 m (http://dml.cmnh.org/2003Jul/msg00355.html) based on maxillary and fibular dimensions.  Rauhut et al. don't do a convincing job of calculating this.  They say "the maxilla is c. 82% of the size of that of Torvosaurus gurneyi, which was estimated to be approximately the size of Gorgosaurus or Daspletosaurus (c. 10 m in length and 4 to 5 tons in weight) by Hendrickx and Mateus (2014a)."  So that'd be ~8 meters long.  They then say "On the other hand, the caudal vertebrae are closely comparable in size to elements from a similar position in Torvosaurus tanneri, and the fibulae are even slightly longer than those referred to the latter taxon (Britt, 1991); this taxon was estimated to be approximately 9 m in body length by Britt (1991). Thus, Wiehenvenator is one of the largest theropods found so far in Europe and might only have been slightly smaller than Torvosaurus gurneyi."  Except that there are multiple Torvosaurus individuals present in the collection described by Britt, who never says what his ~9 meter estimate is based on.  If you use the scale bar on their skeletal reconstruction, Wiehenvenator is ~8.3 m long.  So good job me thirteen years ago.

References- Rauhut, Hübner and Lanser, 2015. A new theropod dinosaur from the late Middle Jurassic of Germany and theropod faunal turnover during the Jurassic. Libro de resúmenes del V Congreso Latinoamericano de Paleontología de Vertebrados. 62.

Rauhut, Hübner and Lanser, 2016. A new megalosaurid theropod dinosaur from the late Middle Jurassic (Callovian) of north-western Germany: Implications for theropod evolution and faunal turnover in the Jurassic. Palaeontologia Electronica. 19.2.26A, 1-65.

Wednesday, July 13, 2016

Is Gualicho Aoniraptor?

A very cool theropod was published today- Gualicho shinyae (Apesteguia et al., 2016).  It's a large taxon from the Huincul Formation of Argentina, notable for having tiny, didactyl arms and generally resembling Deltadromeus.  The authors propose both are related to megaraptorans instead of ceratosaurs... and wait, didn't we just have this situation (Motta et al., 2016)?  I might as well be the first person* to propose this seemingly obvious synonymy- Gualicho is the same taxon as the recently named Aoniraptor.  Both are from the same formation, of similar size (mid caudals ~87 vs. 83 mm), and Gualicho has two diagnostic characters noted for Aoniraptor- "anterior mid-caudal vertebrae with fan-shaped prezygapophyses lacking a discernible articular surface for contacting the postzygapophyses; presence of a blunt and thick process on the lateral surface of the prezygapophyses of anterior midcaudal vertebrae", and might have the third- "mid-posterior caudals with a pair of nonarticular flat surfaces located on the posterodorsal corner of the centrum."  As Aoniraptor was named first (June 16th vs. July 13th), it has precedent over Gualicho.  Edit #2: As Brad McFeeters notes in a comment below, the volume Aoniraptor was named in has yet to be physically published and does not contain a ZooBank registration, thus Gualicho has precedent.

*Edit: After posting this, I learned both Andrea Cau (here) and Brad McFeeters (on Facebook) independently came to the same conclusion.  Guess it really was an obvious synonymy. ;)

I'm skeptical that these and Deltadromeus belong in Tetanurae, as it only takes 4 steps to move them to Ceratosauria in Apesteguia et al.'s version of Carrano's tetanurine analysis, and Deltadromeus wasn't added to their version of Novas' tetanurine analysis which also lacks any ceratosaurs except the outgroup Ceratosaurus.  They note "Gualicho does exhibit some apparent ceratosaurian synapomorphies, most notably a robust MT III with posteriorly expanded proximal articulation and a flange-like m. iliofibularis tubercle."  It would have been interesting to run them in a ceratosaur analysis.

 
Holotypes of Gualicho shinyae (MPCN PV 0001; top) and Aoniraptor libertatum (MPCA-Pv 804; bottom) in posterior (E), anterior (F), left lateral (G) and dorsal (H) views.  Modified from Apesteguia et al. (2016) and Motta et al. (2016).

 Wonder where they go in the Lori analysis....

References- Apesteguía, Smith, Juárez Valieri and Makovicky, 2016. An unusual new theropod with a didactyl manus from the Upper Cretaceous of Patagonia, Argentina. PLoS ONE. 11(7), e0157793.

Motta, Aranciaga Rolando, Rozadilla, Agnolin, Chimento, Brisson Egli and Novas, 2016. New theropod fauna from the Upper Cretaceous (Huincul Formtation) of northwestern Patagonia, Argentina. In Khosla and Lucas (eds.). Cretaceous period: Biotic diversity and biogeography. New Mexico Museum of Natural History and Science Bulletin. 71, 231-253.


Wednesday, July 6, 2016

Is Lagerpeton a proterochampsian? The Dromomeron angle

Sorry for the lack of posts (or Database updates) lately, as I've been working with Scott Hartman to add Lori to the coelurosaur matrix and finalizing that study.  But I started writing this as a DML reply and figured why not make it a post instead...

Novas and Agnolin (2015) have an abstract on Lagerpeton that proposes it is actually a proterochampsian sister to Tropidosuchus.  If true, this would be a rare time David Peters got something right, as he had this idea back in 2011- https://pterosaurheresies.wordpress.com/2011/10/15/what-is-lagerpeton-the-heretical-view/ .  I hope Novas and Agnolin credit him if they write a paper on this.

However, something not addressed by Novas and Agnolin is how Dromomeron relates.  According to Nesbitt (2011), Tropidosuchus lacks all lagerpetonid characters shared by Lagerpeton and Dromomeron- Anterolateral tuber of the proximal portion of the femur absent, the anterolateral face is flat (302-1), Femoral head hook shaped in medial and lateral views (306-1), Ventral emargination present on anterolateral side of the femoral head (310-1), Crista tibiofibularis larger than the medial condyle (326-1), Dorsally expanded process on the posterolateral portion of the tibial facet of the astragalus expanded into a distinct, raised process (5 posterior ascending process of Sereno and Arcucci, 1994a) (355-1), Concave articular surface for the fibula on the calcaneum (378-2).  Of the proterochampsian characters noted by Novas and Agnolin as present in Lagerpeton, Dromomeron lacks two- femoral 4th trochanter proximodistally expanded; caudal surface of distal tibia with a middle tubercle surrounded by two shallow concavities; but has one- astragalus with anteromedial corner acute.  Others are unknown since Dromomeron is so fragmentary, but at least "elongate and compact metatarsus with metatarsal V reduced and devoid of phalanges" would be expected in a taxon close to Marasuchus (which has the conditions), so that works for either placement of Lagerpeton.  Then there are the dinosauriform-like characters of Lagerpeton scored by Nesbitt as absent in Tropidosuchus- Straight cnemial crest (328-1); Longest metatarsal longer than 50% of tibial length (383-1); Metatarsal V "hooked" proximal end absent, and articular face for distal tarsal 4 subparallel to shaft axis (398- 1).  And the archosaurian characters of Lagerpeton scored as absent in Tropidosuchus- Articular surfaces for fibula and distal tarsal IV on the calcaneum continuous (380-1), Anteromedial tuber of the proximal portion of the femur present (300-1), Tibial facet of the astragalus divided into posteromedial and anterolateral basins (366-1).


Phylogeny of eucrocopodans recovered by Ezcurra (2016), with Novas and Agnolin's (2015) proposed reidentification of Lagerpeton indicated in red (modified from Ezcurra, 2016).

Taking all of this into account (with the caveats that I haven't checked the accuracy of any characters except the proterochampsian states of Dromomeron, and that this only uses unambiguous characters listed by Nesbitt), Novas and Agnolin have ten characters that might need to converge if Lagerpeton is a dinosauriform relative, but there are nine characters that might need to converge if Lagerpeton is a proterochampsian (the seven from Nesbitt listed here plus two listed by Novas and Agnolin).  So that's one step in favor of a proterochampsian identity.  But if Dromomeron is a proterochampsian too, that adds three more steps (the two listed above plus dinosauromorph character 313 of Nesbitt that is present in Dromomeron but unknown in Lagerpeton).  Thus dinosauriform-relative Lagerpeton is two steps shorter.  And if Dromomeron is a dinosauriform relative but Lagerpeton is not, that adds five steps (the six lagerpetonid characters that would need to be convergent minus the proterochampsian-like acute astragalar corner).

So basically, ignoring Dromomeron might make proterochampsian Lagerpeton a slightly better option but a proterochampsian Dromomeron turns those odds around, and a proterochampsian Lagerpeton but a dinosauriform-relative Dromomeron is even worse.  So pending further analysis, I favor the traditional view (note Ezcurra's huge 2016 archosauromorph analysis which sampled proterochampsian diversity also recovered this topology).  If Lagerpeton is a proterochampsian, then Lagerpetonidae is a junior synonym of Proterochampsia definition-wise (and Proterochampsidae ICZN-wise).  However, Novas and Agnolin are wrong in claiming "The exclusion of Lagerpeton from the dinosaur lineage results in the removal of the clade Dinosauromorpha, which was originally conceived to encompass Lagerpeton plus Dinosauriformes."  The only proposed definition of Dinosauromorpha that mentions Lagerpeton is one of Sereno's (1991) which is "Lagerpeton chanarensis, Lagosuchus talampayensis, Pseudolagosuchus major, Dinosauria (inc. Aves), and all descendants of their common ancestor."  Following this definition, Dinosauromorpha merely moves stem-ward to be the Proterochampsia+Archosauria clade which is AFAIK otherwise unnamed.  The other proposed definitions are all basically "taxa closer to dinosaurs than pterosaurs", so Dinosauromorpha would stay where it is even if Lagerpeton isn't a member.

References- Sereno, 1991. Basal archosaurs: Phylogenetic relationships and functional implications. Society of Vertebrate Paleontology Memoir. 2, 1 53 pp

Nesbitt, 2011. The early evolution of archosaurs: Relationships and the origin of major clades. Bulletin of the American Museum of Natural History. 352, 292 pp.

Novas and Agnolin, 2015. Lagerpeton chanarensis Romer (Archosauriformes): A derived proterochampsian from the Middle Triassic of NW Argentina. Libro de resúmenes del V Congreso Latinoamericano de Paleontología de Vertebrados. 48.

Ezcurra, 2016. The phylogenetic relationships of basal archosauromorphs, with an emphasis on the systematics of proterosuchian archosauriforms. PeerJ. 4:e1778.

Saturday, April 2, 2016

Database update plus Predatory Dinosaurs of the World with phylogenetic nomenclature

Hey fellow 80s kids!  Like me, you probably grew up with Paul's (1988) Predatory Dinosaurs of the World as your first serious non-technical theropod source, along with The Dinosauria.  After raking Peters' horrific theropod phylogeny over the coals and applying current phylogenetic nomenclature for fun, I wondered how the most famous non-technical topology of our time would fare.  So here's Paul's phylogeny from his influential book using the taxonomy from The Theropod Database.  Note a number of his named groups are paraphyletic in his topology (based on overleaf 10-1, with additional details based on his comments in the taxonomic section).  Only species with entries were included.

Dinosauromorpha
Dinosauriformes

|*-Saltopus
|--Lagerpetonidae
|  |--Lagosuchus (inc. Marasuchus)
|  |--Lewisuchus

|  `--Lagerpeton
`--Herrerasauridae

   |--Staurikosaurus
   `--+--Ischisaurus
      `--+--Herrerasauria
         |  |?*Alwalkeria
         |  |?-Protoavis
         |  |--Freguellisaurus
         |  `--+--Aliwalia
         |     `--Herrerasaurus
         `--Avepoda
            |--Procompsognathus
            `--Megalosauria
               |--Spinosauroidea (= Coelophysoidea, Spinosauridae)
               |  |?-Elaphrosaurus
               |  |--Coelophysidae
               |  |  Coelophysis
               |  |  |--rhodesiensis
               |  |  `--bauri
               |  `--Dilophosauridae
               |     |--Liliensternus
               |     `--+--Dilophosaurus
               |        `--+--Baryonychinae
               |           |  Baryonyx
               |           `--Spinosaurinae
               |              Spinosaurus
               `--Neotheropoda (= Averostra, Neoceratosauria, Abelisauroidea, Torvosauridae)
                  |--Ceratosauria (= Ceratosauridae)
                  |  |--Sarcosaurus
                  |  `--Ceratosaurus
                  |     |?-ingens
                  |     `--nasicornis
                  `--Tetanurae (= Abelisauridae, Orionides)
                     |--Megalosauroidea (= Megalosauridae)
                     |  |--+--Megalosaurus
                     |  |  |--Torvosaurus 
                     |  |  `--Poekilopleuron
                     |  `--Abelisauria
                     |     |?-Noasauridae
                     |     |  Noasaurus
                     |     |--Carnotaurinae
                     |     |  Carnotaurus
                     |     `--Abelisaurinae
                     |        Abelisaurus
                     `--+--Eustreptospondylinae
                        |  Eustreptospondylus (inc. Streptospondylus)
                        `--+--Piatnitzkysauridae
                           |  Piatnitzkysaurus
                           `--+--Gasosaurus
                              `--+--Marshosaurus
                                 `--Allosauroidea
                                    |--Metriacanthosauridae (= Sinraptoridae)
                                    |  |--Yangchuanosaurus (inc. Metriacanthosaurus? sp.)
                                    |  `--Metriacanthosaurus (assuming Sinraptor)
                                    `--Avetheropoda (= Neotetanurae, Allosauria, Tyrannoraptora)
                                       |*-Dryptosaurus
                                       |--Compsognathidae
                                       |  Compsognathus
                                       |--Tyrannosauroidea (= Carnosauria)
                                       |  |--Coeluridae
                                       |  |  |--Aristosuchus
                                       |  |  `--Coelurus
                                       |  |--Proceratosauridae
                                       |  |  |--+--Proceratosaurus
                                       |  |  |  `--Pivetaeusaurus 
                                       |  |  |--Rapator
                                       |  |  `--Ornitholestes
                                       |  `--+--Allosauridae
                                       |     |  Allosaurus fragilis (inc. A. atrox, A. amplexus)
                                       |     `--Carcharodontosauridae (= Carcharodontosauria)
                                       |        |--+--Chilantaisaurus
                                       |        |  `--Shaochilong
                                       |        `--+--+--Acrocanthosaurus
                                       |           |  `--Becklespinax
                                       |           `--+--Indosaurus
                                       |              `--+--Labocania
                                       |                 |--Erectopus
                                       |                 |--Carcharodontosaurus
                                       |                 |--Bahariasaurus
                                       |                 `--+--Aublysodontinae
                                       |                    |  |--Aublysodon
                                       |                    |  |--Shanshanosaurus
                                       |                    |  `--Stygivenator
                                       |                    `--+--Indosuchus
                                       |                       `--+--Alioramini
                                       |                          |  Alioramus
                                       |                          `--Tyrannosauridae
                                       |                             |--Albertosaurinae
                                       |                             |  |--Alectrosaurus
                                       |                             |  `--+*-Albertosaurus
                                       |                             |     |--Nanotyrannus
                                       |                             |     `--+--Gorgosaurus
                                       |                             |        `--+--arctunguis
                                       |                             |           `--Dinotyrannus
                                       |                             `--Tyrannosaurinae
                                       |                                |--Daspletosaurus
                                       |                                `--+--Tarbosaurus
                                       |                                   `--Tyrannosaurus
                                       `--Coelurosauria (= Aviremigia, Ornithes)
                                          |--Archaeopterygidae (= Saurornithes)
                                          |  Archaeopteryx
                                          `--Eudromaeosauria
                                             |--Dromaeosauridae (= Dromaeosaurinae)
                                             |  |--Dromaeosaurus
                                             |  `?-Adasaurus
                                             `--Eumaniraptora (= Pennaraptora, Averaptora)
                                                |--Deinonychosauria (= Velociraptorinae)
                                                |  |--Deinonychus
                                                |  `--+--Saurornitholestes
                                                |     `--Velociraptor
                                                `--Avialae
                                                   |?-Ornithomimosauria (= Arctometatarsalia)
                                                   |  |--Harpymimus
                                                   |  `--Ornithomiminae
                                                   |     |?-Deinocheiridae
                                                   |     |  Deinocheirus
                                                   |     |--Garudimimus
                                                   |     `--Ornithomimidae
                                                   |        |*-affinis
                                                   |        |*-Archaeornithomimus
                                                   |        `--+--Struthiomimus 
                                                   |           |?-Ornithomimus
                                                   |           |--Dromiceiomimus
                                                   |           |  |--brevitertius
                                                   |           |  `--samueli
                                                   |           `--Gallimimus
                                                   |--Oviraptorosauria (= Caenagnathiformes)
                                                   |  Caenagnathoidea
                                                   |  |--Caenagnathidae
                                                   |  |  |--Microvenator
                                                   |  |  `--+--Caenagnathinae
                                                   |  |     |  Chirostenotes
                                                   |  |     `--Elmisaurinae
                                                   |  |        Elmisaurus
                                                   |  `--Oviraptoridae
                                                   |     |--Oviraptorinae
                                                   |     |  Oviraptor (assuming Citipati)
                                                   |     `--"Ingeniinae"
                                                   |        "Ingenia"
                                                   `--Maniraptora (= Avimimidae, Paraves)
                                                      |--Troodontidae
                                                      |  |--Troodon
                                                      |  |--Saurornithoides
                                                      |  |--Heptasteornis
                                                      |  `?-Bradycneme  
                                                      `--+--Avimimus
                                                         `--Ornithothoraces (= Avebrevicauda, Ornithopectae)
                                                            |--Enantiornithes
                                                            |  Iberomesornis (assuming Enantiornis)
                                                            `--+--Ichthyornithes (= Ambiortiformes)
                                                               |  |--Ambiortus
                                                               |  `--Ichthyornis
                                                               `--+--Gansuiformes
                                                                  |  Gansus
                                                                  `--+--Hesperornithes
                                                                     |  Hesperornis
                                                                     `--Aves

So how does it fare?  Pretty well, though Herrerasauridae, Megalosauria, Spinosauridae and Tyrannosauridae have definitions that fail.  There are some uncertainties based on the unclear position of ornithomimosaurs, and due to the date there are no taxa between Archaeopteryx and ornithothoracines.  But overall, not bad. 

Among the "Theropod Odds and Ends", Taquet's (1984) taxon has yet to be redescribed but seems to be a coelophysoid, "Labrosaurus" ferox is agreed to be an allosaurid/Allosaurus specimen and maybe a portion of the A. fragilis neotype.  (Magnosaurus) nethercombensis is a megalosauroid, possibly afrovenatorine.  (Duriavenator) hesperis is a megalosaurid.  Xuanhanosaurus seems to be a metriacanthosaurid.  Iliosuchus may be a basal tyrannosauroid or other basal coelurosaurian, which is debated for taxa known from far more than only ilia.  Stokesosaurus is universally agreed to be a basal tyrannosauroid.  Finally, Segisaurus is agreed to be a coelophysoid closer to Coelophysis than Dilophosaurus.

Twenty-third (II) and twenty-second (III) dentary tooth of holotype of Segnosaurus galbinensis (IGM 10/80), after Zanno et al. (2016). Note the weird lingual carina (lc).
Oh, and I updated the Database this month, but less than usual due to coding more in the Lori matrix.  Besides the last sauropodomorph entry  (Ignavusaurus ?= Massospondylus), a couple braincases were added to the Bissekty tyrannosauroid(s?) and named Timurlengia.  Wonder where this falls out in the new tyrannosauroid matrix of Brusatte and Carr (2016).  The Pierre Shale hesperornithoids of Manitoba were clarified by Aotsuka and Sato (2016), with the description of a new species.  Segnosaurus' mandible was also redescribed (Zanno et al., 2016), which I hope is the first of many therizinosaurian redescriptions from them.  It's quite an odd specimen, exhibiting a coronoid process like oviraptorosaurs, no posterior surangular ridge or foramen and TRIcarinate posterior dentary teeth.  Yes, unlike (?)any other theropod, Segnosaurus has a lingual carina with serrations (see above).

References- Taquet, 1984. Two new Jurassic specimens of coelurosaurs (Dinosauria). In Hecht, Ostrom, Viohl and Wellnhofer (eds.). The Beginnings of Birds: Proceedings of the International Archaeopteryx Conference, Eichstaett. 229-232.

Paul, 1988. Predatory Dinosaurs of the World. Simon & Schuster. 464 pp.

Aotsuka and Sato, 2016. Hesperornithiformes (Aves: Ornithurae) from the Upper Cretaceous Pierre Shale, southern Manitoba, Canada. Cretaceous Research. doi: 10.1016/j.cretres.2016.03.003.

Brusatte and Carr, 2016. The phylogeny and evolutionary history of tyrannosauroid dinosaurs. Scientific Reports. 6, 20252.

Zanno, Tsogtbaatar, Chinzorig and Gates, 2016. Specializations of the mandibular anatomy and dentition of Segnosaurus galbinensis (Theropoda: Therizinosauria). PeerJ. 4:e1885.