"The Princeton Field Guide to Dinosaurs" - The Ornithischians

Finishing up the review series is this post on ornithischians.  As with sauropodomorphs, these aren't my speciality, so I don't have educated opinions on most of the issues nor do I always know exactly what the latest consensus is.  Honestly, the same kinds of problems are present in this section as the previous one.  I think I've figured out Paul's splitter/lumper methodology though.  If a taxon is similar to another, but from a different horizon, it's a different species!  Doesn't matter if anyone's actually tried to name a distinct taxon from there yet, or if there are actually any differences reported in the literature.  If a taxon is from the same horizon as another similar one, they're synonymous!  Ignore priority and use the name of the most complete specimen for the taxon.  If a species forms a clade with another, they're congeneric!  With these three easy steps, you too can lump and split the GSP way. ;)

As with the other sections, there are many excellent reconstructions.  My favorites are Scutellosaurus, Gigantspinosaurus, Saichania, Pinacosaurus, Ankylosaurus, Edmontonia, Archaeoceratops, Prenoceratops, Montanaceratops, Talenkauen, Gasparinisaura, Muttaburrasaurus, Probactrosaurus, Tethyshadros, and the many derived hadrosaurs.  It's nice to see the ankylosaurs and hadrosaurs reconstructed, since usually people only bother with their skulls.

Like theropods, thyreophorans unjustly suffer from the statement "absence from Antarctica probably reflects lack of sufficient sampling." Despite the fact Antarctopelta is known AND included in the book.  Chungkingosaurus and Chialingosaurus are said to probably be juvenile Tuojiangosaurus, but the former is a diagnostic huayangosaurid (Maidment and Wei, 2006) and the latter has priority over Tuojiangosaurus.  Upper Tendaguru Kentrosaurus remains "probably belong to a different taxon" while Stegosaurus longispinus "probably is a more basal stegosaurid."  These may be true, I don't know.  Amusingly, Wuerhosaurus "is not a species of Stegosaurus as has been suggested."  I'm not sure why Paul's lumpometer fails here.  For "Hesperosaurus (or Stegosaurus) mjosi", "Lack of limbs hinders assessing whether this is a Stegosaurus as some reseachers have concluded."  Because Stegosaurus is apomorphy-defined using limb characters?

Dracopelta, Shamosaurus, Gobisaurus, Stegopelta, Niobrarasaurus and Antarctopelta are listed as "polacanthians."  Good ol' nonexistent Polacanthia...  I'm unaware of these taxa even being referred to Polacanthidae.  Pinacosaurus mephistocephalus is listed as a synonym of P. grangeri and Struthiosaurus languedocensis "may be the adult" of S. austriacus.  Again, are these plausible?  I don't know.  But claiming Pawpawsaurus "probably includes Texasetes pleurohalio" is certainly incorrect, as Texasetes has priority.  "Euoplocephalus tutus" is placed in quote marks, said to have an inadequate holotype and said to possibly consists of multiple taxa.  Horseshoe Canyon specimens are assigned to ""Euoplocephalus" unnamed species?" though, presumably because they're from a different formation.

Butler will be surprised to hear Heterodontosaurus "probably includes the smaller, tuskless Abrictosaurus consors as well as Lycorhinus angustidens."

Homalocephalids are said to probably be immature pachycephalosaurids or females, which leads to "Goyocephale (or Stegoceras) lattimorei" and "Prenocephale (or Stegoceras) prenes" with Homalocephale "probably an immature P. prenes."  There's also "Tylocephale (or Stegoceras) gilmorei."  Even if he's right about homalocephalids, none of the Asian taxa are especially close to Stegoceras.  Of course Paul's Stegoceras is a huge para/polyphyletic mass including every non-Pachycephalosaurus North American taxon at least, since Stegoceras? brevis "may include Colepiocephale lambei", and Stegoceras validum "may include Hansuessia sternbergi."  Dracorex and Stygimoloch are probably juvenile Pachycephalosaurus "in which case the spikes are a sexual characteristic, or there may be two species, the other being P. spinifer." But what about the spikes being resorbed?

The only new non-theropod taxonomic name proposed in the book is Paxceratopsia for psittacosaurs and neoceratopsians, but not chaoyangosaurs.  Psittacosaurus meileyingensis "probably includes P. ordosensis", Udanoceratops "may include Bainoceratops efremovi" and Gobiceratops "may be a juvenile" Bagaceratops.  Again, I'm not sure if these are plausible.  I was disappointed to see all non-ceratopsid neoceratopsians called protoceratopsids.  Cerasinops is listed twice in the book, with identical entries at least.  For ceratopsids, Paul has the odd division between centrosaurines, chasmosaurines AND ceratopsines.  Err.... Paul includes only Triceratops and Avaceratops in Ceratopsinae and says "The existence of this group is not certain." Well, since it's never been recovered in an analysis and there's no reason Ceratops itself is close to either genus, I suppose that's true.  Paul's ceratopsids are lumped like there's no tomorrow.  There's "Albertoceratops (=Diabloceratops) eatoni".  All other centrosaurines are Centrosaurus, so we get Centrosaurus (=Styracosaurus) albertensis, C. (=Styracosaurus) ovatus, C. (=Einosaurus[sic]) procurvicornis, C. (=Achelousaurus) horneri, C. (=Pachyrhinosaurus) lakustai, and C. (=Pachyrhinosaurus) canadensis.  But Centrosaurus nasicornis and C. apertus are separate, no doubt because they're from different levels of the Dinosaur Park.  Not only is such lumping pointless, IF it were true, Monoclonius would be the proper genus since crassus is definitely somewhere in that clade.  For chasmosaurines, we get Chasmosaurus (Pentaceratops = Agujaceratops) mariscalensis and Chasmosaurus (Pentaceratops) sternbergi.  Which makes both Chasmosaurus and the supposed subgenus Pentaceratops para/polyphyletic.  And of course Triceratops is lumped, with Triceratops (=Eotriceratops) xerinsularis, and Nedoceratops (incorrectly listed as Diceratops) a synonym of T. horridus. 

Moving on to ornithopods, Hexinlusaurus "is probably immature example of" Agilisaurus louderbacki.  Even though the former is closer to ornithopods in Butler's tree.  Then we have "Agilisaurus? unnamed species" which was "named Yandusaurus hongheensis based on inadequate remains."  Not only is Yandusaurus closer to ornithopods than Agilisaurus, but Yandusaurus has priority over Agilisaurus AND how can you have an unnamed species that used to be a named species?!  More predictably bad taxonomy- Othnielosaurus consors was "once Othnielia rex."  More like Othnielia isn't necessarily Othnielosaurus.  Anabisetia, Gasparinisaura, Talenkauen, Thescelosaurus and Parksosaurus are all listed as hypsilophodonts, but are iguanodonts.  Iguanodonts also get the old "absence from Antarctica probably reflects lack of sufficient sampling" treatment, but there's a hadrosaur from there (Case et al., 2000).  The Tenontosaurus dossi cranial reconstruction doesn't have premaxillary teeth.  For rhabdodont lumping, Rhabdodon (=Zalmoxes) robustus "probably includes Z. shqiperorum."  But then for horizon-based splitting, "Dryosaurus unnamed species" (for Utah Middle Morrison remains) is "usually placed in D. altus but probably is a different species than the latter dryosaur, and differing genera cannot be ruled out."  The placement of taxa in Paul's iguanodont grades seems problematic, with e.g. Planicoxa being a dryosaur.  I was amused that Paul's own taxon Dollodon bampingi is misspelled "bambingi" every time.

Finally, there's the lumptastic hadosaurs.  It honestly looks like Paul just used a twenty-year old classification and applied his three lumping/splitting steps.  Bactrosaurus "probably includes Gilmoreosaurus mongoliensis." We get Saurolophus (=Lophorthothon[sic]) atopus, Saurolophus (=Prosaurolophus) blackfeetensis, and Saurolophus (=Prosaurolophus) maximus.  Lophorhothon isn't even a hadrosaurid, while blackfeetensis is a synonym of maximus, but silly me it's from a different formation.  Maisaura (or Brachylophosaurus) peeblesorum "may be a subgenus of Brachylophosaurus", which is just meaningless.  There's Kritosaurus (or Gryposaurus) latidens, notabilis, incurvimanus, and monumentensis and Kritosaurus (or Anasazisaurus) horneri.  Last I heard, horneri was a synonym of navajovius, incurvimanus was a synonym of notabilis, and you'd need to put Secernosaurus in Kritosaurus if you put Gryposaurus there.  Most sadly, we have Aralosaurus (or Kritosaurus) tubiferus, despite the fact Aralosaurus is a lambeosaurine.  Pararhabdodon "probably includes Koutalisaurus", which agrees with Prieto-Marquez.  Parasaurolophus walkeri and "P. tubicen are not distinctive from one another, and short crested New Mexican P. cyrtocristatus may be a female or subadult of this species."  I'm not sure about the evidence for that.  Olorotitan "may be the same genus or species as Amurosaurus riabinini", which is untrue as they're not closely related within Lambeosaurinae.  We get both Nipponosaurus (or Hypacrosaurus) sachaliensis and Barsboldia (or Hypacrosaurus) sicinskii, though the latter is a saurolophine.  In fact, all the helmet-crested lambeosaurines get placed in one genus.  There's Hypacrosaurus (=Velafrons) coahuilensis, Hypacrosaurus (=Corythosaurus) casuarius and intermedius, Hypacrosaurus (=Lambeosaurus) clavintialis, lambei and mangicristatus, and Hypacrosaurus? laticaudus.  Again, I didn't think clavintialis was valid, while you'd need to put Amurosaurus and Sahaliyania in Hypacrosaurus too if you're lumping like that.

And that's it.  Be sure to check out Jaime Headden's review and future commentary too.