Wednesday, February 24, 2016

Fukuivenator thoughts

So we have another new theropod, Fukuivenator paradoxus (Azuma et al., 2016).  With Fukuiraptor, Fukuititan and Fukuisaurus also in existence, we just need a Fukuipelta, Fukuimimus and Fukuiornis to round out the Kitadani Formation.  This was first announced in an anonymous 2009 msn article (now defunct) and Shibata and Azuma's (2010) SVP abstract.  While those sources called it a dromaeosaurid, Azuma et al. interestingly say "it in fact represents a bizarre, basally branching maniraptoran theropod with a large number of autapomorphies."  Intriguing.  Let's check it out...

A partial skull is present (though the jugal, palatine, ?ectopterygoid and pterygoid are unillustrated) as well as a dentary fragment.  The weirdest thing is the gigantic premaxilla, which is so odd that I would question its identity and propose it's actually the right maxilla, except that it lacks the pneumatic fossa and foramina present on the left maxilla.  Contra the authors, the posterolateral process of the premaxilla is broken so (barring the presence of some really well preserved sutures on the maxilla) it cannot be determined if it extends posterior to the external naris like in dromaeosaurids.  Similarly, the supposedly large promaxillary fenestra (cited in the diagnosis as well) is actually small.  The text claims the lacrimal is T-shaped, but the figure shows the posterodorsal process is unpreserved, and the character is coded unknown in their matrix.  Although the authors claim the frontals have dromaeosaurid-like anterolateral notches and sigmoid supratemporal fossa edges, neither is visible in the figured left element.  Amusingly, Azuma et al. say one premaxillary tooth "exhibits a "ridge," on which denticles are absent."  Ah, you mean a carina? ;)  The other premaxillary tooth is indeed interesting in being D-shaped.  Surely the fenestra labeled "IX?" in figure 4  is the otic fenestra, and the basipterygoid processes are confusingly labeled as laterosphenoids twice in that figure.  The supposed medial eustachian foramina are the paired foramina of the basisphenoid recess.  Oddly, neither of the eustachian tube characters are coded, but the basisphenoid recess characters are coded correctly.  It's an interesting braincase, with no obvious dorsal or posterior tympanic recesses, a reduced basisphenoid recess and laterally diverging basipterygoid processes, most of which are troodontid-y.

Reconstructed skull of Fukuivenator paradoxus holotype, premaxilla and dentary flipped, and frontal shown in dorsal view (modified from Azuma et al., 2016).

An almost complete vertebral series is present.  The description states "ten cervical vertebrae are preserved, missing at least the atlas but the materials list only says "eight cervical vertebrae" are present.  Hmm.  The text states "the middle cervical vertebrae have a highly modified hyposphene-hypantrum with the hypantrum extending ventrally below the dorsal border of the neural canal (Fig. 6b)", but the figure shows nothing extending ventrally into the neural canal and I thought hyposphene-hypantrum articulations were absent from most theropod anterior dorsals, let alone cervicals.  "Dorsal centra are longer anteroposteriorly than tall dorsoventrally, unlike the dorsal centra of typical predatory theropods."  :|  Tell that to coelophysoids, compsognathid-grade taxa, troodontids, microraptorians...  "Likely pleurocoels are present in all dorsal vertebrae in the form of longitudinal fossae on the lateral surfaces of centra."  Haven't we progressed since the days of Osmolska et al. and Welles calling central fossae pleurocoels?  This is another character coded as dromaeosaurid-like, but the posterior dorsals (at least) actually lack pleurocoels as is standard for theropods.  Azuma et al. also state "the parapophyses of the dorsal vertebrae including the posterior ones are stalk-like as in derived alvarezsauroids and dromaeosaurids, though they are not as prominent as in the latter groups", but they're actually short.  My matrix uses a ratio of parapophyseal length (measured from the ventromedial corner to the apex) and centrum width, so that even Alxasaurus and some Sinraptor and Allosaurus vertebrae count as apomorphic (contra the unchanging TWG matrix), but Fukuivenator still falls short.  The authors state "the [sacral] zygapophyses are fused to each other to form a platform lateral to the neural spines, a feature also known in dromaeosaurids", but the figured sacrum lacks neural arches in the first four vertebrae.  Azuma et al. say the sacral ribs+diapophyses are "bifurcated distally to contact the ilium, a feature previously unreported in any other theropod", but this is true in e.g. the middle four sacrals of Gallimimus.  They also say "the most unusual feature is that the prezygapophyses of the middle caudal vertebrae are distally bifid (Fig. 6i), which has not been reported in any dinosaurs", but this is a standard dromaeosaurid character reported in e.g. Deinonychus (Ostrom, 1969) and Velociraptor (Norell and Makovicky, 1999).

Pes of Fukuiraptor paradoxus holotype, as shown in figure 7h on left, and with my reidentification of the phalanges on right (modified from Azuma et al., 2016).  Note the longer phalanges on digit II as in other theropods, and how digit II isn't particularly developed into a sickle-claw.
Contra the text and coding, the coracoid is proximodistally shallow, unlike pennaraptorans.  Surely, figure 7's caption is incorrect and the humeri shown are a right in anterior view and left in lateral view, not the left "in lateral (left) and posterior (right) view."  Also, the femur in figure 7f is in medial and posterior views, not lateral and posterior.  In figure 7h, the pedal phalanges are almost certainly placed incorrectly, with II-1 and II-2 switched with IV-1 and IV-2, which explains why digit II looks ridiculously short (see figure above).  "IV-1" has the standard shape of II-1 with the medial side highly concave (so it actually belongs on the other foot), plus I don't think any terrestrial Mesozoic theropod has IV-1 longer than II-1.  The measurement table is partly inconsistent as it has IV-2 subequal to IV-3 and IV-4 in length, unlike the figure.  Contra the text and coding, I don't think the second pedal digit looks particularly deinonychosaurian- Tanycolagreus has the same dorsally prominent distal articular surface on II-1, and the ungual in Ornitholestes is comparatively larger.  Alas, the text continues to use the II-III-IV manual digit identification, thanks to Xu, which at least Choiniere has disavowed (in his recent Ceratosaurus forelimb paper with Carrano).  It was an intriguing idea Xu, but it's long past time to let it die.

Azuma et al. add Fukuivenator to Turner et al.'s (2012) TWG analysis, which is unfortunately flawed by having numerous taxa left uncoded for entire sections of the matrix, and most of the codings retained from the original TWG matrix of Norell et al. (2001).  So don't put much credit into e.g. the joining of oviraptorosaurs and therizinosaurs, because the latter are only represented by the 2001 codings for Alxasaurus, Segnosaurus and Erlikosaurus.  No Beipiaosaurus, let alone Falcarius or Jianchangosaurus.  In any case, contra the text, they do not recover Fukuivenator as a maniraptoran.  In their trees, it's actually in a polytomy with compsognathids, Ornitholestes, ornithomimosaurs and maniraptorans.  They also didn't find "Anchiornis and Xiaotingia outside the Troodontidae", instead the base of Deinonychosauria is unresolved with those genera part of the polytomy.  Frustratingly, the authors never try excluding taxa a posteriori, so we don't know if e.g. the underlying structure of Turner's tree is still there and Fukuivenator can fall out in multiple places, or if it creates an actual polytomy between some taxa there.  Running the matrix myself, I find the latter is true- Fukuivenator's character combination creates a polytomy there even if it's pruned from the tree a posteriori.  Also, the Anchiornis+Xiaotingia situation exists because in a minority of trees these are sister to microraptorians+eudromaeosaurs instead of being basal troodontids.  Interestingly, the authors do check how parsimonious it is to place Fukuivenator in alternative positions and find it only takes three more steps to make it a paravian, deinonychosaur or dromaeosaurid. 

Adding Fukuivenator to the Lori matrix recovers it in a trichotomy with Ornithomimosauria and Maniraptora.  Makes sense considering its general basal coelurosaur grade anatomy.  There are a few dromaeosaurid-like characters- the fossa around the maxillary fenestra, the short ventral postorbital process, the squamosal shelf over its ventral process, the twisted paroccipital processes, the reduced crista prootica, the bifurcated caudal prezygapophyses.  But the vast majority are quite unlike paravians, and as seen above, many of the supposedly dromaeosaurid-like characters aren't present.  Andrea Cau recovered Fukuivenator as sister to Pennaraptora in his Megamatrix, which isn't far from my result as only alvarezsauroids and therizinosaurs are between the two Fukuivenator positions, basal members of which (e.g. Haplocheirus, Falcarius) are like Ornitholestes-grade coelurosaurs in much of their anatomy. 

References- Ostrom, 1969. Osteology of Deinonychus antirrhopus, an unusual theropod from the Lower Cretaceous of Montana. Bulletin of the Peabody Museum of Natural History. 30, 165 pp.

Norell and Makovicky, 1999. Important features of the dromaeosaurid skeleton II: Information from newly collected specimens of Velociraptor mongoliensis. American Museum Novitates. 3282, 45 pp.

Anonymous, 2009. [3rd new species? Small-sized meat diet dinosaur to restoration Fukui] 3/18/2009 

Shibata and Azuma, 2010. New dinosaurs from the Lower Cretaceous Kitadani Formation of the Tetori Group, Fukui, Central Japan. Journal of Vertebrate Paleontology. Program and Abstracts 2010, 163A-164A.

Turner, Makovicky and Norell, 2012. A review of dromaeosaurid systematics and paravian phylogeny. Bulletin of the American Museum of Natural History. 371, 1-206.

Azuma, Xu, Shibata, Kawabe, Miyata and Imai, 2016. A bizarre theropod from the Early Cretaceous of Japan highlighting mosaic evolution among coelurosaurians. Scientific Reports. 6, 20478.

Thursday, February 18, 2016

Sauropod Thoughts

So this month I've been concentrating on adding sauropods to the Database, going in reverse chronological order.  I find sauropods interesting because unlike theropods, their phylogenetics are almost completely unresolved.  I mean sure there's a basic outline and diplodocoids are pretty well researched, but there are huge swaths of cetiosaur-grade and titanosaur(iform/oid) grade taxa that can go almost anywhere between Vulcanodon and Neosauropoda on the one hand, and between Camarasaurus and Eutitanosauria on the other.  What follows are some thoughts on taxa or papers describing them...

Zby is based on mostly a forelimb that was originally assigned to Turiasaurus in a SVP abstract (Mateus, 2009), but later described as a new genus (Mateus et al., 2014).  But the seven characters listed by the latter authors as distinguishing the taxa are only determinable in their holotypes, not the referred specimens of Turiasaurus.  Given their stratigraphic and geographic proximity and the variation seen within theropod species, it seems plausible Mateus was right in 2009.

Holotype of Zby atlanticus (ML 368) (after Mateus et al., 2014).

I didn't realize how sad the descriptive situation is for Galeamopus. Sure the type skull was described almost a century ago, and the other skulls have featured in discussions of Diplodocus crania, but the postcrania of the type or the new Howe Quarry specimen (SMA 0011) have never been described.  We need not only a description of these, but also a paper describing all the supposed Diplodocus skulls, since according to Tschopp et al. (2015), no skulls can actually be referred to that genus.  Thus the Diplodocus OTUs in every other analysis are composites.

Despite having four generally stellar coauthors, the description of Abydosaurus (Chure et al., 2010) is... well... bad.  Even though it has seven supplementary documents, one of which is a spreadsheet of several hundred sauropodomorph tooth elongation indices, there's no measurement table for anything except two cervicals.  The most we get for the skull is "The four known skulls of Abydosaurus are nearly the same size, measuring approximately 0.5 m long and half as tall posteriorly."  You could have used less words and given us precise data for all four specimens.  And the table with the cervical measurements includes data for seven other sauropods, all but two of which are from previously published literature anyway.  Why spend space on data already out there instead of publishing new data?  The referred postcrania don't have repository numbers listed either.  Finally, the phylogenetic analysis goes out of its way to delete data from Wilson's original version, removing all but two non-neosauropods, combining genera to make four suprageneric OTUs, deleting characters that don't vary due to those removals, etc..  All this does is make it more tedious for future workers to add Abydosaurus to the base version of Wilson's matrix that tens of other papers use, and it's not like Wilson's 234 character, 27 taxon matrix is unwieldy for any 2010 computer to handle.  They just spent a lot of time and effort to make the analysis worse.

Proximal caudal vertebra of Normanniasaurus genceyi (MHNH-2013.2.1) (after Le Loeuff et al., 2013). Scale = 10 cm.

Normanniasaurus (Le Loeuff et al., 2013) is one of the most fragmentary taxa I've seen erected in the past few decades (the holotype consists of two presacral prezygapophyses, three fused sacral centra, an incomplete proximal caudal vertebra, an incomplete mid caudal vertebra, partial scapula, two ilial fragments, ischia [one partial, one fragmentary], a femoral fragment and a fibular fragment).  This is quite ironic considering Le Loeuff's famous 1993 paper declaring most European titanosaurs to be indeterminate (Macrurosaurus, Hypselosaurus, Aepisaurus, "Titanosaurus" lydekkeri).  Most of the supposedly diagnostic characters listed by the authors are either primitive for titanosauriforms (presacral vertebrae with hyposphene-hypantrum articulation; middle caudal vertebrae amphicoelous; ilium with anterolaterally expanded blade) or classic characters diagnosing larger clades within it (internal texture of presacral vertebrae camellate; proximal caudal vertebrae deeply procoelous; middle caudal vertebrae with anteriorly placed neural arch).  I'm very doubtful whether the remaining few caudal characters will prove diagnostic if anyone looks into them.  When added to Mannion et al.'s (2013) matrix, Normanniasaurus resolves as a eutitanosaur closer to Saltasaurus than opisthocoelicaudiines. 

Finally, Mannion and Otero (2012) did a superb job redescribing Argyrosaurus.  The taxon is only known from a forelimb, though apparently the entire skeleton was originally there but did not survive excavation.  This is my favorite kind of paper- redescribing a taxon known for decades in a modern context.  Mannion's one of my favorite sauropod authors, having redescribed Mongolosaurus (2010), "Brachiosaurus" atalaiensis (2013) and B? nougaredi (2013).  Mannion and Otero didn't include Argyrosaurus in a phylogenetic analysis, saying it has some plesiomorphic characters despite sharing many characters with derived titanosaurs.  I coded Argyrosaurus in Mannion et al.'s macronarian matrix, and I have to say the characters are well formed, so that coding is objective.  I'm not a sauropod expert, so I don't have the background comprehension of sauropod characters, but Mannion makes them easy to code.  Argyrosaurus ends up as a nemegtosaurid (sister to Mongolosaurus and Rapetosaurus), so despite Mannion et al.'s lack of many lithostrotians, the genus seems to be a member of the clade.  If it is a nemegtosaurid, Argyrosauridae Bonaparte 1987 has priority over Nemegtosauridae Upchurch 1995.  Interesting.  One critique of the paper is that it doesn't specify the horizon and locality of referred Argyrosaurus specimens (so I had to refer back to Powell 2003 and Bonaparte and Gasparini 1979), and proposes these are nomina dubia without detailed examination or comparison.

Will the next post get back to theropods? Depends on the papers published in the near future.  Come on, O'Connor, I dare ya. ;)

References- Mateus, 2009. The sauropod dinosaur Turiasaurus riodevensis in the Late Jurassic of Portugal. Journal of Vertebrate Paleontology. 29(3), 144A.

Chure, Britt, Whitlock and Wilson, 2010. First complete sauropod dinosaur skull from the Cretaceous of the Americas and the evolution of sauropod dentition. Naturwissenschaften. 97(4), 379-391.

Mannion and Otero, 2012. A reappraisal of the Late Cretaceous Argentinean sauropod dinosaur Argyrosaurus superbus, with a description of a new titanosaur genus. Journal of Vertebrate Paleontology. 32(3), 614-638.

Le Loeuff, Suteethorn and Buffetaut, 2013. A new sauropod dinosaur from the Albian of Le Havre (Normandy, France). Oryctos. 10, 23-30.

Mannion, Upchurch, Barnes and Mateus, 2013. Osteology of the Late Jurassic Portuguese sauropod dinosaur Lusotitan atalaiensis (Macronaria) and the evolutionary history of basal titanosauriforms. Zoological Journal of the Linnean Society. 168(1), 98-206.

Mateus, Mannion and Upchurch, 2014. Zby atlanticus, a new turiasaurian sauropod (Dinosauria, Eusauropoda) from the Late Jurassic of Portugal. Journal of Vertebrate Paleontology. 34(3), 618-634.

Tschopp, Mateus and Benson, 2015. A specimen-level phylogenetic analysis and taxonomic revision of Diplodocidae (Dinosauria, Sauropoda). PeerJ. 3:e857.