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Longisquama errors



This weekend several errors in the literature came to my attention
regarding Longisquama, some of them mine.

The multiple head crests are equal in size to the dorsal crests. This
may be the cause of the confusion regarding an earlier hypothesis
regarding paired dorsal crests capable of gliding. No, its a single
lineup of plume-like scales (not feathers) from premaxilla to the hips.
This thing is like a walking lionfish! Or maybe a weedy sea dragon with
legs.

The coracoid has a triangular head and a narrow stem that curves
posteriorly, not quite as in pterosaurs, and it is only a third the size
of the scapula. Two scapulocoracoid sets are visible and both remain
connected to one another despite the one set disarticulating beyond the
outlines of the dewlap. The other coracoid has been flopped so that it
is concave anteriorly. This appears to have occurred as it followed the
drifting sternal complex to its present location anterior to the rib
cage. Here the clavicles assume the position that they assume in
theropods and birds and humans. (Don't tell me Mother Nature doesn't
have a wry sense of humor.) Of course the clavicles overlap one another,
they frame the sternum proper and the keeled interclavicle extends
anterior to the horseshoe shaped clavicles, as in all pterosaurs.

The humerus has a deltopectoral crest. A small one, but it's there.
Twice.

All of the phalanges of at least one hand are present, as are all of the
carpals. It's a mess. Digit one found its way between the radius and
ulna of the opposite fore limb. Among Longisquama's many frills a
propatagium is present. It does not appear to stretch between proximal
humerus and wrist, but rather matches the bend in the elbow. A pteroid
(= medial centrale) is present in the position it assumes in pterosaurs.
So to the preaxial carpal. A minor tenopatagium is present. It extends
from the arm pit down 3/4 of the humerus. Some "tassles" extend
posteriorly from it. Other tassles extend posterior to the ulna. They
appear loose and not part of a wing.

The pelvis is present. It's in the classic primitive pterosaur shape
with an anterior ilium separated from the posterior ilium by about 120
degrees. Most other pterosaurs have the ilial processes oriented
opposite one another, as in Cosesaurus and Sharovipteryx. The ilium is
as long as the existing vertebral column. Part of a prepubis might be
present, but it is represented by a broken piece of the right shape and
in the right position. Not a firm ID.

A robust femur, tibia and fibula are present, as are two complete pedes.
The tibia is much longer than femur, and twice as thick and twice as
long as the humerus. Dang, could be another bipedal pterosaur sister
taxon! Penultimate phalanges are not the longest. It think that means
its a sprinter, rather than a climber. Toes are subequal. with the first
toe slightly shorter, as in pteros. Fifth toe has a claw and appears to
be the smallest of all the toes. Wasn't expecting that. Other pedal
claws are sharp but flat, rather than raptorial.

The tibia was the most obvious bone of all the new ones. I'm surprised
no one noticed it before. But then those frills are like a covering of
seaweed.

I can't find anything more of the remainder of the dorsal vertebral
series, nor any sacrals or caudals.

Anyone wishing jpegs can contact me privately.

More later,

David Peters
St. Louis