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I've just read the description of Rapetosaurus and
have some comments.
"Currently we recognize
two titanosaur taxa in the Maevarano Formation that are distinguished, in part,
by their caudal vertebrae. Deperet's
T. madagascariensis syntype includes both caudal morphologies and is therefore
considered a nomen dubium."
Ughh. Damn the current trend to trash old
species just to name a new one. They should designate one of the
"Titanosaurus" madagascariensis caudals the lectotype and name one of the new
genera "genus A" madagascariensis. "T." madagascariensis is obviously not
nomen dubium if its remains can be referred to two other species. It's
simply a chimaera and must be split.
"Rapetosaurus also offers
the best opportunity yet to resolve the phylogenetic
position of two controversial Mongolian sauropods,
Nemegtosaurus and Quaesitosaurus."
I agree here, Nemegtosaurus and Quaesitosaurus are
definitely titanosaurids. I was a believer in diplodocoid nemegtosaurids
before, but Rapetosaurus is just too similar to nemegtosaurs and has too many
titanosaurid postcranial characters. Well Upchurch, you did your best
:-)
A rather large phylogenetic analysis was performed
(228 characters, 16 taxa), with the following result-
_______Omeisaurus
|_______Dicraeosaurus
|
|___Apatosaurus
|
|__Diplodocus
|________Camarasaurus
|________Brachiosaurus
|________Euhelopus
|________Antarctosaurus
|
|_____Malawisaurus
| |_____Quaesitosaurus
| |_____Nemegtosaurus
| |_____Rapetosaurus
|___________Titanosaurus
|___________Alamosaurus
|___________Opisthocoelocaudia
|___________Saltasaurus
|___________Neuquensaurus
Good job finally including Titanosaurus. They
call the (Titanosaurus + Alamosaurus + Opisthocoelocaudia + Saltasaurus +
Neuquensaurus) clade Saltasaurinae. However, I thought Saltasaurinae was
defined as all taxa closer to Saltasaurus than Opisthocoelocaudia. I think
Titanosaurinae should have priority over Saltasaurinae if the latter is used
like Curry Rogers and Forster do. Also, Titanosauridae should be
somewhere, why have people forgotten it? Making Rapetosaurus,
Nemegtosaurus and Quaesitosaurus diplodocoids adds 29 steps. I dislike the
inclusion of Euhelopus in the Titanosauria. Wonder what happens when
Mamenchisaurus or Rebbachisaurus are included. When Mamenchisaurus is
added to Wilson and Sereno's matrix, it clades right below Omeisaurus, but only
2 more steps are needed to make it go into the Titanosauria with
Euhelopus. Eight more steps make the (Omeisaurus, Mamenchisaurus,
Euhelopus) clade monophyletic and fall below neosauropods.
Below is a summary of the basic facts about
Rapetosaurus. It is not a details segment, as I have not added a
description or relationships section. Perhaps I'll write one
later.
Rapetosaurus Curry Rogers and Forster
2001
R. krausei Curry Rogers and Forster
2001
Etymology- "David Krause's giant lizard", after
Rapeto, a mischevious giant in Malagasy folklore.
Anembalemba Member of Maevarano Formation,
Madagascar
Maastrichtian, Late Cretaceous
Holotype- (UA 8698) maxillae, nasals, lacrimal,
jugal, quadrate, pterygoids, partial basioccipital, paroccipital process,
dentary, surangular, angular, twenty-four teeth
Referred- (FMNH PR 2184-2192, 2194, 2196, 2197,
2210) exoccipital, opisthotic, laterosphenoid, supraoccipital, frontals, prefrontals, surangular, parietal, squamosal,
mid-caudal centrum
(FMNH PR 2209) (juvenile) 75% complete
skeleton
(UCB 92829) mid-caudal centrum
Diagnosis- expanded
antorbital fenestra extends over tooth row; preantorbital fenestra positioned
posterior to antorbital fenestra; subnarial foramen anteriorly positioned and
dorsoventrally elongate; jugal process of maxilla posterodorsally elongate and
narrow; frontals with median dome; quadrate with V-shaped quadratojugal
articulation; supraoccipital with two anteriorly directed median parietal
processes; pterygoid with extremely shallow basipterygoid articulation and
dorsoventrally expanded anterior process; basipterygoid processes diverge only
at distal extremes; dentary with 11 alveoli that extend two-thirds the length of
the element; gracile cylindrical teeth with high-angle planar wear facets; 16
cervical vertebrae with constricted neural canals and continuous pre- and
postspinal coels devoid of pre- or postspinal laminae; cervicalneural spines
with proximal bifurcation and three pneumatized coels bounded by discrete
laminae; 11 dorsal vertebrae with deep lateral pleurocoels; dorsal neural spines
with strong pre- and postspinal laminae in deeply excavated anterior and
posterior coels; dorsals with median interpre- and interpostzygapophyseal
laminae; middle and posterior dorsals with divided spinodiapophyseal lamina; six
sacral centra with deep lateral pleurocoels; all caudal centra procoelous with
convex ventral margin lacking excavation; anterior
caudal centra broad transversely and anteroposteriorly compressed;
middle-posterior caudal centra with constant length:width ratio; anterior-middle
caudal neural spines with spinoprezygapophyseal, prespinal and postspinal
laminae on rectangular and anteriorly positioned neural arches; chevrons
throughout 80% of tail; iliac peduncle of ischium comprises one-quarter of
acetabulum; ischial peduncle of ilium low and poorly developed; pubis more than
twice as long as ischium; scapula and coracoid with equal glenoid contribution;
scapular blade not distally expanded; humerus/femur length quotient 0.80; radius
and ulna with oblique interosseus ridges.
Those who want the pdf, contact me offlist. Mickey Mortimer |