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David Unwin's The Pterosaurs From Deep Time - review



The Pterosaurs From Deep Time by David Unwin (2005) - a review

Robert Bakker turned the world of dinosaurs upside down with his pivotal
1986 Dinosaur Heresies. John Long set all the fish of prehistory on a
tableau of fascination  in his 1997 The Rise of Fishes. Greg Paul?s
Dinosaurs of the Air from 2002 is a must-have for any bird-dino reader.
These are the benchmark books by which all those that follow are to be
judged.

In like manner, Peter Wellnhofer opened up the world of flying reptiles
to the modern reader in his landmark Encyclopedia of Pterosaurs in 1991.
Sparing none, he presented the spectrum of taxa then known, along with
the spectrum of hypotheses surrounding these contentious little rascals.
Although in 1991 all the parts (i.e. taxa and ichnotaxa) were in place
to settle virtually all the arguments about pterosaurs, cladistic
analysis was still in its paleo infancy when the manuscript was turned
in and no one was working with many of the key taxa. They sat gathering
dust in drawers.

Enter David Unwin?s The Pterosaurs From Deep Time (2005), self described
as ?the first complete portrait of the legendary dragons of deep
time...? During the intervening 14 years since Wellnhofer?s Encyclopedia
much has been learned as many more pterosaurs have been discovered and
new hypotheses have surfaced. I hoped and expected this next major
installment on the Pterosauria to take the reader where Wellnhofer and
the preceding Handbuch could not go. Claiming to be the latest word in
pterosaurs, Unwin states, ?the true nature of these Mesozoic dragons has
proven elusive ? until now? and ?this book puts that [puzzle] picture on
display for the first time... ? and ?the pages that follow contain the
first comprehensive account of our new understanding of how pterosaurs
were constructed and how they lived their lives..?

Well, maybe that was too much build-up. I was really disappointed.

Given that the pen is mightier than the sword, Unwin had to have been
eager to lance, slash and dismember all opposing and weaker viewpoints
with unprecedented and insightful cladistic analyzes, skeletal
reconstructions and other weapons of science to set the record straight
on the nature and origin of pterosaurs as he clearly intended to and was
given license to do. Perhaps no one else has had access to more
specimens than Dr. Unwin. Perhaps no one has been more vocal on his love
and fascination for the clade.

To the disappointment of all, and foremost myself, David Unwin kept his
pen sheathed. Where questions bubbled and boiled Unwin, after a quick
peek in the pot, put the lid back on to keep the mysteries simmering.
Rather than fully employing the event and forum of a major hard cover
book to break new ground and cause all to gasp, Unwin has given us cold
leftovers. Virtually all of the figures have been seen before. Certainly
no more detail is offered - and some of what is offered is self
contradictory.

A look at Unwin?s bibliography shows few original works. He?s good at
compiling compendiums and he reviews the discoveries of others. Here,
true to his style and pattern, Unwin almost never creates detailed
anatomical studies but instead traces and copies the outline drawings of
others, mostly skulls, rarely feet. His famous 1994 Nature paper (along
with wife, N. Bakhurina) was a repeat of Sharov?s studies from twenty
years earlier. Pterosaurs from Deep Time is no different, written in a
vernacular that might appeal to paleo beginners with juicy fiction
opening each chapter, it lacks the details and substance that could have
put it in the league of great or even good books. Some of the photos are
keepers though.

Here are a few of the problems:

The family tree of the Pterosauria, as depicted by Unwin (fig. 4.5), is
a real tree with 17 select skulls figured as metaphorical fruits at the
ends of branches. The pterodacs are at the top and the rhamporhynchs are
at the bottom. Of course, this sort of graphic hearkens back to the
pre-cladistic trees of the 20s through 70s ? quaint ? but ashamedly not
keeping up with the freshman basics of paleontology. Such a tree reveals
no cladistic analysis, and would appear incomplete according to Unwin?s
own count of over 100  taxa, (over 80 percent incomplete!) Missing are
some  key taxa, such as Sordes, Dorygnathus, Huanhepterus, Wellnhofer?s
Nos. 9, 12, MPUM 6009 (the basal most pterosaur), Austriadactylus,
Arthurdactylus, Cycnorhamphus, Istiodactylus, etc. etc. and all of those
found since 1991. Where do they fit in? Here Pteranodon inexplicably
joins the toothy broad-snouted pterosaurs rather than the other
toothless sword snouts. Post-crania unfortunately do not make much of an
appearance here.

Unwin?s prime example of the new 1990s pterosaur, figure 1.5, lifted
from Frey and Tischlinger is a crested Pterodactylus, here pictured with
not five or four but three bird-like toes and a nostril as far back as
possible in the antorbital fenestra, next to the eye. Probably not
correct.

For pterosaur origins Unwin discounts the Scleromochlus/Ornithodire
hypotheses, which is good. He discounts Bennett?s early archosaur
hypothesis, which is good. Then he discounts the
prolacertiform/Sharovipteryx hypothesis, noting that the little arms and
long neck place Sharovipteryx far from pterosaurs. Given those
objections, why did Unwin also ignore Longisquama and Cosesaurus? These
two prolacertiforms, one closer and one further from pterosaurs, both
have a short neck and long arms and were proposed as sister taxa 5 years
ago. When discussing the prolacertiform hypothesis, Unwin omits the only
two authors who have made the suggestion: myself and himself, and uses
the general term: ?some?, as in some workers, but elsewhere he credits
others by name.

Later (but on the same subject), rather than employing a real pterosaur
sister/ancestor taxon as determined by PAUP (and PAUP can nest
everything!), Unwin opens an old curtain to reveal Rupert Wild?s
completely imaginary drawing of an arboreal lizard with short legs and a
long fourth finger. Unwin laments that the origin of flapping remains a
mystery,  ignoring yet another paper that explains it in Longisquama. So
great disappointment also in this category.  Flapping is basic to what
it means to be a pterosaur. Why not a whole chapter on its origin?

For wing shape, Unwin goes both ways. In flight (fig. 8.5) his
pterosaurs have deep chord wings that attach at the ankles. Grounded
(fig. 1.5) the wings seem to originate from the thighs, with the extra
flight membrane from the ankle (I suppose) pulled tight to the knees,
like a curtain held back by a diagonal cord. Not sure how this works and
it?s not explained, but it?s an age-old question. I was disappointed not
seeing a sequence depicting wing folding Unwin-style.

Unwin?s figure 8.12 shows a landing pterosaur sequence lifted from
Chatterjee and Templin in which the pterosaur folds its wing while still
airborne (!) and without the usual high lift thrust reversal flapping
that accompanies landings in birds and bats. Ironically (and this is the
fault of the editor I suppose), the same figure  is said to explain the
take-off process, according to the text (p. 191). Echoing Chatterjee and
Templin, Unwin suggests a bipedal running takeoff scenario with lift
generated from the wings to support the front half of the body, helped
by a headwind or running down an incline. Of course running upright with
such deep wings turns the membranes into parachutes. Pity the poor
pterosaur with such limitations. The elongated ilia and fused vertebrae,
where they any help in elevating the spine on the hind legs alone? There
may be more to this story left untold.

I suppose it is unusual to be singularly erased from a bibliography and
yet thanked in the acknowledgements (I actually had nothing to do with
this book). Not one of my abstracts or peer reviewed published studies
are to be found here. I can understand Unwin?s reason for doing so. Most
of my papers cast doubts on his hypotheses and observations or they
provide alternative views. If my theories and observations were invalid
or weak, they should have been easily dispatched and this was the forum
to do it in. With my work unconsidered, Unwin can indeed claim, as he
does, that the most vexing pterosaur questions have been answered. But
where is the victory? Evidently unable or unwilling to respond to those
published objections, he has opted to simply ignore them. While this may
seem like good science to Unwin, it is a great disappointment to ?some?.
I eagerly looked forward to Unwin?s logic and his powers of persuasion.
But they?re not here. And if it didn?t happen here (remember, you get
paid to write a book), evidently it?s not going to happen ever.

I was also hoping for a crystal clear example, even one, of a deep chord
wing membrane extending to the ankle. Unwin left it a mystery and did
not respond to an earlier published account that disputed his Sordes
observations. He did suggest that the Zittel wing was trimmed with a
knife (and if so, by how much? a millimeter seems most likely, otherwise
why slice good stuff off of a perfect specimen?). Ironically. on the
same page as the ?trimmed? Zittel wing, Unwin shows us the Vienna
specimen of Pterodactylus in which there is no doubt that the wing
membrane extends only between the elbow and wing finger  with a small
fuselage fillet (nor a part of the wing), extending to mid thigh, on
both wings.

I was hoping to see what happens, step-by-step, to a broad chord wing
membrane when it is folded after landing. Does it droop? Or what? And
why not? Unwin left it a mystery.

Unwin maintains his faith in his bizarre machine-gun style pteroid
configuration and holds Jeholopterus up as a prime example. Here the
elbow is complerely flexed in both arms reducing the distance between
the pteroid and the deltopectoral crest which relaxes the membrane and
permits the abreviated bone to drift anteriorly. The identity of the
pteroid is cast off with the phrase, ?identity aside,? ignoring an
earlier paper that showed that the pteroid and its more distal
counterpart are former centrale that have migrated to the leading edge
of the wing and act as passive restraints to overextension of the wing
finger due to drag while in flight.

I was hoping to see the famous ?flat-footed? Dimorphodon weintraubi set
in various phases of the walk cycle and at no time extending the toes.
Unwin left it a mystery. The one drawing of the tree-perching pterosaur
next to D. weintraubi unfortunately is drawn with forbidden extended
toes. Guess it was missed in editing. Lizards capable of bipedal
locomotion have similar restrictions and it doesn?t stop these flatfoots
from going bipedal and digitgrade at high speed. The human hand is
likewise incapable of extension -- except when pressure is applied --
and the same could apply to pterosaur feet adding a bit of spring to
each liftoff. Unwin offered no explanation.

I was hoping to see any basal or pre pterosaur foot and what that darn
fifth toe was doing when grounded or branch bound or as a stepping
sequence. Unwin left it a mystery. He also did not include the one
undisputed bipedal digitgrade anurognathid track, the so-called ?sauria
aberrante,? but that?s been missed by others as well. The evolution of
this novelty toe would have been interesting to see.

I was hoping to see a matching of track-makers to tracks. Unwin left
that a mystery.

I was hoping to see full body reconstructions of pterosaurs discovered
since Wellnhofer?s 1991 Encyclopedia. Unwin left that a mystery too.

I was hoping to see a matching of juveniles to adults - especially among
the tiny pterodactyloids. This is a hot topic. Except for the
Rhamphorhynchus ?growth? series of skulls lifted from Wellnhofer (which
has been shown to be a phylogenetic series leading from
Campylognathoides when tested in PAUP), none were shown. Those tiny
'babies' may actually be hummingbird and bat-sized adults.

I was hoping to see a reconstruction of what exactly was in those eggs.
Unwin left that a mystery. Speaking of eggs, Unwin reports that the
pterosaur eggs were thin and soft-shelled, like those of lizards and
turtles, rather than birds and alligators. Hmm, maybe that clue can help
us in the search for pterosaur origins. Unwin suggests that pterosaurs
buried their eggs, but if they were like lizards, they had the option of
retaining the embryo within the mother until just before shell formation
and hatching. Perhaps this explains why 3 for 3 pterosaur eggs are full
term and so few archosaur eggs are as well formed.

With all these mysteries still left unsolved, as often noted by Unwin
himself, why would he claim that all these mysteries are settled now?

The following few errors also spoil an otherwise good-looking and
easy-to-read book.

Unwin describes the walking posture as elbows in, but illustrates it in
figure 9.3 as elbows out - so far out that the elbows precede the
shoulders gorilla-fashion. Unlikely in that the fingers would point
forward then.

Unwin reports that in a balanced pose the feet must be below the center
of gravity, which in winged creatures is near the shoulder, but to
discredit the bipedal configuration in figure 9.2  he tips the pterosaur
far forward to show it out of balance.

Unwin and Henderson?s Robodactylus is built on the plan of an
ornithocheirid. Out of step with actual anatomy the femora are
completely erect and the feet are only a hip width apart. In reality
these  are the most bow-legged of all pterosaurs.

Unwin describes the primitive uropatagium as binding the hind legs
together, as if one were wearing a raincoat clamped to one?s pants legs
? and that this medial membrane connected to the lateral toes (!) How
this can happen mechanically is not shown. Neither is any explanation
given for its gradual evolution and benefit prior to its use in flight.
He neglects the situation in Sharovipteryx. This sprinter is not
encumbered by its uropatagia because they are split, as in, as Unwin
describes them, the pterodactyloids. The mistaken idea about a binding
uropatagium in basal pteros comes from a misinterpretation of Sordes. It
has been shown (but not cited in Unwin?s book) that what appears to be a
single membrane is instead a standard one membrane per leg
configuration, as in Sharovipteryx and pterodactyloids, with the medial
parts overlapping in this case.

Unwin?s grounded pterosaurs, especially his Robo-Rhamphorhynchus, is in
a difficult configuration that can be immediately remedied by elevating
the angle of the spine.

The analog of living bow-legged lizards capable of rapid bipedal
progression still has not sunk into Unwin?s academic mind. Perhaps it
will when he learns that pterosaurs are indeed lizards. In fact you can
throw away all the closest sister taxa and include only archosaurs (as
many as you like), a pterosaur and either an iguana or monitor lizard
and the pterosaur will nest with the lizard.

On the plus side, great photographs. Stirring colorful fiction. Unwin?s
command of the English language makes for easy and delightful reading,
but he really should have stepped out swinging and set the record
straight, as he claimed he was going to do.

Instead he bunted.

David Peters
St. Louis

PS. Haven't been on or even read the list for many weeks while busy with
basal diapsids of all things. Be back someday soon. Best wishes to all.
Enjoy Phoenix. I'll wish I was there.