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Re: It's HERE!!!



Hi everyone!  I finally got The Age of Dinosaurs in Russia and Mongolia today.  This post will detail the new data contained within.
I don't know enough about most of the non-dinosaurian taxa discussed, but Sharovipteryx and Longisquama are often talked about on the list, so let's start with their chapter.  I must say the "enigmatic small reptile" chapter was dissapointing in the lack of illustrations.  The holotype of Sharovipteryx is shown only as a small photo and an undetailed drawing.  Longisquama's illustration is redrawn from Sharov.  Regarding Sharovipteryx, the forelimbs and pectoral girdle (except possibly a coracoid fragment) are not preserved, the supposed remains being shafts of anterior dorsal ribs.  The animal was covered by small tubercular or keeled scutes.  The authors classify it as a prolacertiform.  They seem to avoid classifying Longisquama, saying the interclavicle and acrodont teeth are against archosaurian relations and the antorbital fenestra and mandibular fenestra have to be reexamined, but don't comment further.  In fact, Tom Holtz's recent post (http://www.cmnh.org/fun/dinosaur-archive/2000Jun/msg00633.html) is much more useful in this regard.  Oh well.
 
22. Theropod dinosaurs from the Cretaceous of Mongolia, Phillip J. Currie
On to what I was anticipating the most, the theropod chapter.  Unfortunately, this is the worst "taxon" chapter in the book as far as I'm concerned, especially considering the amount of taxa known from Mongolia.  As opposed to most other chapters, the drawings are all rather sketchily redrawn from other works (well, I suppose I'd say that was Gallimimus' pelvis if I HAD to choose...).  Much of the text is wasted on general descriptions of the theropod familes (mostly in layman's terms) and there are no diagnoses, holotype/referred specimen lists, etc..  There is also no attempt to examine poorly known taxa, which would have been enlightening considering Currie's expertise.  Deinocheirus is said to have proportions similar to ornithomimosaurs, but the great arm length is more suggestive of therizinosaurs, and its taxonomic assignment will not be resolved until more specimens are found.  Sigh.  Embasaurus may be megalosaurid.  Double sigh.  Prodeinodon is a carnosaur on the cladogram (modified from Holtz 1994).  Triple sigh.  In all, the chapter appears to be of The Complete Dinosaur calibur, which while excellent for a non-professional, is not good scientific reference material.  But, enough ranting (Currie's probably busy on Liaoning descriptions), let's get on with the new data.  Chiappe and Norell (Norell pers. comm. to Currie) think Hulsanpes
(http://www.cmnh.org/fun/dinosaur-archive/2000Sep/msg00184.html) is not a dromaeosaurid, but from "another more speciose branch of the Maniraptora".  I wonder, does that indicate they think it's avian (like my analysis), or from their troodontid + oviraptorosaur + segnosaur clade?  Currie believes there were two distinct lineages of caenagnathids- large caenagnathines with unfused metatarsi and small elmisaurines with fused metatarsi.  I think this is a ludicrous reason to erect subfamilies considering ontogenetic factors and the small size difference (metatarsus lengths 143-161 vs. 207-230 mm).  Also, as noted by Paul (1988) and Sues (1998), the taxa are so similar as to be possibly congeneric.  Regarding avimimids, "A number of isolated vertebrae, tarsometatarsi and unguals  have been found in Upper Cretaceous strata of North America that closely resemble those of Mongolian avimimids (RTMP coll.)."  Finally, we get some published comment on the Judith River material Holtz mentioned on the list in 1999.  Regarding troodontids, "there is no significant overlap in the known specimens of these three Nemegt genera (Borogovia, Saurornithoides junior and Tochisaurus), which were recovered from the same geographic area, and it is conceivable they all represent the same species."  While S. junior is not very comparable to the other two genera, I have a hard time believing Tochisaurus and Borogovia are synonymous.  Currie thinks there is a strong possibility Archaeornithoides is a juvenile troodontid, dismissing the lack of serrations as a juvenile character.  I wonder if Archaeornithoides and Byronosaurus are synonymous..... Several partial, but undescribed, specimens of Alectrosaurus are in the GIN and another was recently collected from Erenhot, China.  Currie believes Maleevosaurus novojilovi, Tarbosaurus efremovi and Tyrannosaurus bataar are all synonymous (he refers to the species as Tarbosaurus bataar :-( ).  The reports of procoelous cervical vertebrae in Shanshanosaurus are incorrect and re-examination of the specimen (Currie and Dong, in prep.!) suggests it may be a juvenile Tyrannosaurus bataar.  Finally, a table is given which lists Mongolian theropods (and theropods "likely to be discovered in Mongolia", sigh) along with another list- "the most conservative interpretation" of the known species.  I enjoyed the "conservative" potential synonymization of Anserimimus with Gallimimus.  I think that anyone who has ever seen the description of Anserimimus will join me in laughing at the thought of it being a junior synonym of Gallimimus.
 
23. Sauropod dinosaurs from the Cretaceous of Mongolia, Teresa Maryanska
Maryanska appears to have submitted this article in 1994, which is unfortunate considering the new opinions on the phylogenetic positions of Opisthocoelicaudia and nemegtosaurids.  Opisthocoelicaudia is placed as a camarasaurid, with mention of Upchurch's reassignment to the Titanosauroidea, but no opinion or discussion regarding the papers conclusions.  Another skull of Nemegtosaurus is known (GIN coll.).  Again, Upchurch's assignment to the Nemegtosauridae is noted, as is a brief note on Calvo's assignment to the Titanosauridae, but it is still placed as a dicraeosaurine diplodocid and again there are no comments regarding alternate placements.  It's a shame Calvo and Salgado's major papers were not published yet, nor Upchurch's larger analysis and nemegtosaurid JVP paper.
 
24. Ornithopod dinosaurs from the Cretaceous of Mongolia, Central Asia, and Siberia, Hans-Dieter Sues and David B. Norman
This is a great chapter, as it is full of detailed illstrations and is up to date (references span until 1999).  Saurolophus angustirostris may be synonymous with S. osborni, as the latter is poorly described and nearly identical.  Further research is needed to verify this however.  The skull pictured in The Dinosauria is juvenile, by the way.  I think Norman and Sues make too many species nomen dubium, without detailed comparison.  These include Aralosaurus, Barsboldia, Jaxartosaurus and Nipponosaurus.  This is an irritating practice and is often refuted once the specimens are studied (eg. Suzuki, et al. 2000 on Nipponosaurus).  On the other hand, Mandschurosaurus of all taxa is considered incertae sedis.  I do praise Norman on his papers on Arstanosaurus and Iguanodon orientalis, both of which he made nomina dubia after detailed description and comparison.  More papers should follow their examples.  Interestingly, "Gilmoreosaurus" atavus is not hadrosaurid.  Its broad crowns with prominent keels suggest the taxon is a more basal iguanodont.  Also, the material of "Gilmoreosaurus" arkhangelskyi is a mixture of hadrosaurid and more basal ornithopod elements.  I'm looking forward to several papers in preparation by Norman (Redescription of Probactrosaurus gobiensis; New hadrosaurids from Bainshin Tsav; The systematics of the Iguanodontia and the origin of hadrosaurid ornithopods).
 
/ 25. Marginocephalians of Mongolia, Paul C. Sereno
Although I'm not a fan of many of Sereno's methodologies, this chapter is beautifully illustrated, detailed and even includes two phylogenetic analyses.  It is surely the best dinosaurian chapter in the book.  Wannanosaurus is illustrated nicely and is immature (skull has open sutures, contra Maryanska 1990).  Diagnosis- low, fan-shaped crowns with marked median eminence on the lateral surface; extreme flexure of humerus (proximal and distal ends set at 30 degrees to one another).  Diagnosis of Goyocephale- skull with sinuous lateral margin in dorsal view; sternals more slender and gently curved than Stegoceras.  Diagnosis of Homocephale- crescent-shaped, ventrally deflected postacetabular process.  There is also a wonderful illustration of Prenocephale's skull.  Diagnosis- proximal end of quadrate tongue-shaped; bulbous knob on free dorsal margin of quadratojugal.  Another great illustration is given of Tylocephale.  Diagnosis- narrow, deep skull; large lateral quadratojugal fossa.  The supposed antorbital fossa of psittacosaurids is seen as a neomorphic condition unrelated to the cranial sinus system.  Breviceratops is regarded as a junior synonym of Bagaceratops and B. kozlowskii may be synonymous with B. rozhdestvenskyi.  The supposedly diagnostic characters are found in other basal neoceratopsians.  For instance, the dorsally placed nasofrontal suture is also present in Protoceratops and juvenile Bagaceratops.  The advanced postcranial characters are based on the immature holotype and not illustrated adequately.  The nasal horn and accessory premaxillary-maxillary fenestra are also seen in Bagaceratops.  Diagnosis of Bagaceratops- accessory fenestra between premaxilla and maxilla; coosified median nasal horn; reduction of squamosal-jugal contact above laterotemporal fenestra?.  Adult specimens have fenestrated frills.  The nasal may not participate in the antorbital fossa, as this is based on a specimen that does not preserve the area.  Attachment scars indicate an epijugal as large as Protoceratops is present.  The squamosal does contact the jugal above the laterotemporal fenestra.  The low number of teeth and straight lower jaw are probably due to immaturity, as juvenile Protoceratops show the same characters.  The absence of premaxillary teeth cannot be documented, as the area is poorly preserved and juveniles do have premaxillary teeth.  Diagnosis of Protoceratops- short lateral processes on the rostral; low tab-shaped processes on the frill margin; parasagittal nasal prominences; hoof-shaped pedal unguals.  Microceratops gobiensis is based on a dentary without complete crowns that is now lost.  Other referred specimens and M. sulcidens are also based on indeterminate immature material, so are nomina dubia.  Graciliceratops mongoliensis (ety.= slender horn from Mongolia) is described based on a specimen (PAL MgD-I/156) referred to Microceratops gobiensis by Maryanska and Osmolska (1975).  The specimen came from the Shireegiin Gashoon of Mongolia and consists of an articulated skeleton.  It is diagnosed by the very slender median and posterior parietal frill margins and high tibiofemoral ratio (1.2:1).  The skull is shown in ventral view, with a lateral view of the posteroventral section.  There is a short, fenestrated frill and prominent epijugal.  Anyone who wants a scan of the skull (or anything else in this volume), feel free to ask.  Sereno finds no pachycephalosaur features or autapomorphies in Micropachycephalosaurus, so considers it a nomen dubium.  He finds the dentary of Psittacosaurus sattayaraki not neccessarily referrable to Psittacosaurus because the short deep dentary and primary dentary tooth ridges are found on all basal neoceratopsians.  Also, the dentary flange is developed differently in P. sattayaraki than other psittacosaurs, and the anterior end of the dentary is unfinished and weathered, making the broad attachment area for the predentary questionable.    Sereno also refers P. mazongshanensis to Psittacosaurus sp., as he finds no diagnostic features.  Finally, he finds no apomorphies in the holotype or referred material of Asiaceratops, making it a nomen dubium.  Again, I am dismayed by the amount of taxa made nomina dubia so quickly (especially when pondering Sigilmassasaurus, Cristatusaurus, etc.), but the evidence for Microceratops, P. sattayaraki and the synonymization of Breviceratops with Bagaceratops seems fairly good.  Microcephale is not officially named yet (it's still referred to as "dwarf North American species").  The synapomorphies cannot be listed due to space limitations, but the topology is (Stenopelix (Wannanosaurus (Goyocephale (Homocephale, Ornatotholus (Yaverlandia (Stegoceras ((Prenocephale + Tylocephale) (Stygimoloch + Pachycephalosaurus)))))))) (41 characters) and (Psittacosaurus (Chaoyangsaurus (Archaeoceratops ((Leptoceratops + Udanoceratops) ((Bagaceratops + Graciliceratops + Protoceratops) (Montanoceratops (Turanoceratops (Centrosaurinae + Chasmosaurinae)))))))) (72 characters).  As is usual for Sereno's analyses, there is virtually no homoplasy (15 discordant codings out of 936!; 2 discordant out of 574!), so the results seem shaped by Sereno's character choices rather than discovered from relatively unbiased data.  Maybe I'm just being cynical and there is actually very little homoplasy in marginocephalian phylogeny, but his theropod matrices are similar and that worries me.  Also, Ornatotholus was recently found to be a junior synonym of Setgoceras validum (Sullivan 2000), which has implications for this analysis.  My ignorance of ornithischians prevents further comments.
 
26. Ankylosaur dinosaurs from the Cretaceous of Mongolia, Tat'yana A. Tumanova
This chapter is well done, with lots of cranial illustrations and detailed descriptions, but very little discussion and no specific diagnoses.  In fact, nothing new is really said.  Amtosaurus and Maleevus are kept separate from Talarurus (which is not a shamosaurine).
 
27. Mesozoic Birds from the FSU and Mongolia, Evgenii N. Kurochkin
This great and detailed chapter will be reviewed tomorrow.  It has several noval placements for taxa.  Any questions or comments are welcome.
 
Mickey Mortimer