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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 |