'Pterodactyloidea' reconsidered

[David Peters <davidrpeters@earthlink.net>]

David Unwin latest post regarding the subject of Pterodactyloid
monophyly kindly rejected my suggestion to offer his current six
pterodactyloid characters -- and instead put the onus on me to rock
established thinking. He referred us instead to Unwin 1995, among other
sources, but we should keep this as current and restricted as possible.
Unfortunately, Unwin 1995 lists 7 or 8 characters (a redundant character
made it to the list) supporting the monophyly of the Pterodactyloidea,
leaving us to wonder which one or two listed below has dropped out. So
that's why I asked for the current list of six when I originally
accepted his challenge.

Node F of Unwin 1995 lists the following characters which support the
monophyly of the Pterodactyloidea. Here's Node F. My comments follow.

1. narial and antorbital openings confluent

2. quadrate inclined 135º ? 165º (or "radial degrees" if that shift
option character doesn't translate to the web) to the ventral margin of
the skull

3. basipterygoids fused medially

4. loss of ribs in cervicals 1-7

5. 15 or less caudals in tail

6. metacarpal 4 at least 90% length of humerus

7. pes digit 5 reduced to a single phalanx

8. (also see Howse 1986) who adds "loss of cervical ribs" (see No. 4
above).


Howse considered Pterodactylus antiquus and P. kochi as the most
primitive pterosaurs. Unwin 1995 appears to consider Istiodactylus
(formerly Ornithodesmus) and the Ornithocheiridae (including Pteranodon)
at the bottom of his Pterodactyloid family tree. A later paper, Unwin,
Lü and Bakhurina 2000 indicates that the following are the most primtive
pterosaurs: ?'Ornithostoma,' ?'Puntanipterus', Ornithocheiroidea (=
?Nyctosaurus, 'Ornithodesmus' and the Ornithocheridae).

1. I found a separate narial opening in every pterodactyloid. Larger in
more primitive taxa, very small the higher you go. The position is
always anterior to the antorbital fenestra and sometimes overlaps it
dorsally. The narial opening is always bounded dorsally by the nasal and
ventrally by the jugal, both of which extend much further anteriorly
than I've seen in any text. If you don't think a narial opening is
there, you'll see cracks and breakage. Rather than look for the narial
opening, though, which is often infilled with matrix,  or the primary
maxillla ascending process is so reduced as to break off and float
about, I would suggest looking for the anteriormost extent of the nasal
and jugal.

2. The angle of the quadrate varies widely in pterosaurs, extending
beyond 165 degrees to 180 degrees in certain cases.

In MPUM 6009, the most primtive pterosaur, the quadrate angle is 135
degrees, as in Scaphognathus (the new one), certain Dorygnathids and
Angustinaripterus (* perhaps not a "rhamphorhynchoid" grade, after all,
but higher).

Among pterodactyloids, the Dsungaripterids, Thalassodromeus, PAL 1136,
and the tree-biter anhangueride, plus certain, but by no means all,
Pteranodons and Nyctosaurids, appear to be exceptions to Unwin's rule
with higher quadrate angles than 135 degrees.

3. A closer examination reveals separated basipterygoids are retained in
most pterodactyloids, with clear patterns of various sorts of fusion
(top down, bottom up) in separate clades. The basipterygoids are
typically among the first elements to become dislocated, hence first you
have to find them.

4. A closer examination reveals cervical ribs in many pterodactyloids.
They are never robust, but are subequal to each centrum primitively and
shorter to absent in higher taxa in a well-defined pattern that occurs
twice, once in the sword-snouts and once in the straight snouts.

5. The literature typically misses the caudals in pterodactyloids, but I
have found a number of specimens in which the  caudal string is a little
longer than 15, up to 20.  And some retain a small vane. A recent poster
at SVP showed a Pterodaustro caudal series of the latter number. There
is no doubt that the caudals are greatly diminished in all
'pterodactyloids', but considering the pattern of reduction, it appears
to have occurred twice.

6. Only BPM 0002 appears to break this very good rule. Here, however,
PAUP said it happened twice.

7. I found two tiny phalanges on most pterodactyloids. Dsungaripterids +
Pteranodontids + Tapejarids appear to follow the rule however.

Admittedly, I haven't made my case for a diphyletic Pterodactyloidea
here, but just as in the case of the former 'Ornithodira,' first one has
to test and attempt to dismantle current dogma. The case for a
diphyletic Pterodactyloidea will have to be made on a separate occasion,
perhaps after the list of six appears. I though this was going to be an
easier paper to write. Sorry it's taking so long.

More later,

David Peters