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E&P of Pteros, 7 - Notes, Final



E&P of Pterosaurs, 7 - Notes, Final

Pterosaur phylogeny and comments on the evolutionary history of the
group - Kellner

Here Alex publishes his doctoral thesis without much change.
Unfortunately this cladistic analysis suffers the same basic problems
that Dr. Unwin?s has, namely:

1. too few characters -- please add fingers and toes, palates, pelvic
shapes, etc., etc.
2. too few taxon-- Pterodactylus, Rhamphorhynchus, Scaphongnathus and
Dorygnathus, to name a few, need to be broken out into a number of taxa
each. Tiny pterosaurs need to be included.
3. no correct outgroup -- needs to include prolacertiforms
4. all taxon drawings are prepublished, no full body reconstructions are
offered -- suggesting that details overlooked by previous workers were
also overlooked here

Without the tiny, higher prolacertiforms to polarize against, Kellner
chose a basal dinosaur and a basal ornithosuchid, both with a terminal
naris, not one that was set back from the tip, as in prolacerts. Hence
his basal pterosaur clade, the Anurognathidae also has a naris that is
at the tip of the snout. Other problems followed.


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Quick note on Unwin?s phylogeny paper:

Notably absent were any new drawings of Sordes, a specimen near and dear
to Dr. Unwin?s heart. Hope we don?t have to wait for my drawings to get
published to see what Sordes really looks like.


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The detailed ananatomy of Rhamphorhynchus: axial pneumaticitiy and its
implications -- Bonde and Christiansen

An acid-prepared skeleton of Rhamph. is the subject of this paper.
Fascinating and important new insights are offered. The authors note
that advanced pterosaurs, advanced (and perhaps all) sauropodomorphs,
and advanced theropods all appear to have pneumatic air sacs, some of
which invade the axial and appendicular skeleton, but basal members of
the three groups apparently did not possess these features. From this
they conclude that the last common ancestor of the three had air-sac
systems, although they did not penetrate the skeleton and accept the
Ornithodiran model.

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New  specimens of Pterosauria (Reptilia) with soft parts with
implications for pterosaurian anatomy and locomotion -- Frey et al.

This paper repeats much of the data already found in previous papers
regarding the Frey and Tischlinger Pterodactylus, the Tischlinger
Rhamphorhynchus with veined wings, and the super-clawed ?azhdarchide?.
Discussion ensues regarding the evolution of edentulous beaks, cranial
crests, and the anatomy of the foot and hand with regard to aerodynamics
and ichnites respectively. They show a long-clawed hand with unguals
elevated off the substrate in one case. Pretty radical.

The work on edentulous beaks is interesting because it shows an enlarged
terminal hook on the rostrum replacing teeth from front to back and
leading toward the edentulous condition. What I?ve seen is that the
medial premaxillary teeth on some of the descendants of scaphognathids
become terminal, but remain paired through the Germanodactylids, then
merge in later sharp-snouted pterodacs, like Dsungaripterus, Tapejarids,
Nyctos and Pterandon. Hence, ?edentulous? pterodacs appear to retain
their most anterior teeth at the tips of their beaks.

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Middle- and bottom-decker Cretaceous pterosaurs: unique designs in
active flying vertebrates -- Frey, Buchy and Martill

Seems some scapulocoracoids have flat tops, others have flat bottoms,
some have their glenoids right in the middle. At first I thought there
must be some kind of mistake. The bottom-deckers look exactly like
inverted top-deckers. But now I?m a convert!

The authors seem to think that the difference is due to aerodynamics.
They show airplanes with high and low wings, and note that roll
stability is enhanced by high wings above the center of gravity. Not so,
but I?ll let Jim C. address this question. They also show airplanes with
and without uplifted wing tips (dihedral) and note that increased
dihedral increases stabilty. This is established fact, but has nothing
to do with bottom-decking, because dihedral can be present in high-wing
aircraft (but this was not shown as a possibility). Of course, during a
flapping sequence the dihedral angle is all over the place. Their
observations are good, but their arguments are weak. Other causes and
benefits of bottom-decking need to be looked at.

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Pterosaur tracks from the latest Campanian Cerro del Pueblo Formation of
Southeastern Coahuila, Mexico -- Rodrguez de la Rosa

A short description of some small, narrow, short-toed tracks. Not much
to say here. They remind me of Pterodaustro prints.

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Ichnological evidence for quadrupedal locomotion in pterodactyloid
pterosaurs: trackways from the Late Jurassic of Crayssac (southwestern
France) - Mazin et al.

A description of the track assemblage here and elsewhere, discussions of
substrate cohesion and lack thereof, crocodilian vs. pterosaurian
tracks, the problem of manus only tracks, concluding that
pterodactyloids were able to walk quadrupedally without much difficulty,
and sometimes to have unexpectedly high terrestrial velocity.

The authors present their walking pterosaur with a backbone elevated
some 20 degrees, but only in one pose, so the walking sequence is left
to the imagination. The running pose, ironically is lowered to a
horizontal backbone. Here I would have liked to have seen if there was a
suspended phase during the running cycle. With a lower, more lizard-like
pose, it is difficult to imagine how the wings could have been taken out
of the cycle in preparation for lift-off. But this is only conjecture on
my part. Perhaps, as Jim suggests, there was a bounding leap before
take-off.

Yesterday I offered an alternative walker with a backbone elevated some
50-60 degrees.  Mpegs of the complete cycle are still available.


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Pterosaur swim tracks and other ichnological evidence of behaviour and
ecology - Lockley and Wright

Traces of swimming, wading and floating pterosaurs are presented here,
along with feeding traces (beak tip imprints). The size and morphology
range of known tracks is shown. The Purbeckopus track has traditionally
been identified with the widest, least straight digit being No. 4, but
it may be the first digit. As in the Korean tracks, digit V makes an
impression midway down the foot. Both are azhdarchid tracks. With a
separate ancestry, Azhdarchids  did not experience the same reduction of
digit V that other ?pterodacs? did. The Purbeckopus and Korean tracks
also point up a cladistic division within the Azhdarchidae, between
short metatarsal-long toe forms (like big Q.) and those with long
metatarsals and short toes (like Zhejiangopterus).

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The systematic problem of tetrapod ichnotaxa: the case study of
Pteraichnus Stokes, 1957 (Pterosauria, Pterodactyloidea -- Billon-Bruyat
and Mazin

Interesting point brought up by the authors: Agadirichnus may be a
possible senior synonym for Pteraichnus.


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The John Quekett sections and the earliest pterosaur histological
studies -- Steel

Short paper on 150 year-old thin section studies.


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Histovariability in bones of two pterodactyloid pterosaurs from the
Santana Formation, Araripe Basin, Brazil: preliminary results -- Sayao

Two specimens from South America are thin-sectioned at various
anatomical places and compared. Differential growth rates are found
within a single specimen demonstrating bone growth cessation in some
parts, but not others. Also first reports of pneumatic canals are
reported in the femur of one specimen. Good paper.