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Hey, look! Another details segment.
Seems I have a bird thing going.....
Longipteryx Zhang, Zhou, Hou and Gu
2001
L. chaoyangensis Zhang, Zhou, Hou and Gu
2001
Etymology- "long-wing from Chaoyang
City"
Barremain, Early Cretaceous
Yixian Formation, Liaoning, China
Holotype- (IVPP V 12325) (~190 mm) skull (58 mm),
mandible, seven cervical vertebrae, three dorsal vertebrae, nine pairs of dorsal
ribs, five uncinate processes, six rows of gastralia, sacrum, four caudal
vertebrae, pygostyle, scapulae, coracoids, furcula, sternum (25 mm), four pairs
of sternal ribs, humeri (46 mm), radii (41 mm),
ulnae (45 mm), radiale, ulnare, semilunate, metacarpal I (4.4 mm), phalanx I-1
(8.5 mm), manual ungual I (7.7 mm), metacarpal II (17 mm), phalanx II-1 (10
mm),phalanx II-2 (9.3 mm), manual ungual II (8.5 mm), metacarpal III (18 mm),
phalanx III-1 (5.1 mm), phalanx III-2 (1.5 mm), femora (30 mm), tibiotarsi (32
mm), fibulae (12 mm), metatarsal I (4.8 mm), phalanx I-1, pedal ungual I,
metatarsal II (20 mm), phalanx II-1, proximal phalanx II-2, metatarsal III (20.5
mm), phalanx III-1, proximal phalanx III-2, metatarsal IV (21 mm),
phalanges from digit IV
Referred- (IVPP V 12552) complete
skeleton
(IVPP V 12553) furcula, humerus
(IVPP V 12554) ulna
Diagnosis- elongate beak forms over 60% of skull
length; forelimb long compared to hindlimb- humerofemoral ratio over 1.6;
metatarsal IV longer than metatarsal III.
Description- Although two fairly complete skeletons
are known, the text does not indicate which are being described at a given
time. Similarily, the figure does not list which specimen is illustrated,
although the photo is clearly the holotype. It will be assumed the
holotype is described and illustrated in this description. The holotype is
approximately 190 mm long, assuming the pygostyle is complete. Certain
characters (unfused metacarpus and tibiotarsus) are considered primitive
here, while the fused metatarsus indicates some amount of maturity.
The skull is very elongate compared to other basal
avians, with a long narrow beak. Most of this is due to the elongate
premaxilla. There appears to be a long external naris taking up the
posterior two-thirds of the snout. The posterior skull is angled
downwards, similar to ornithomimosaurs, and houses enlarged orbits. An
interorbital septum is preserved, as is a sclerotic ring of nine elements.
The quadrate is double-headed, with a poorly developed orbital process.
The mandibular elements are unfused, with a longer dentary and shorter posterior
elements than other basal pygostylians, due to the elongate
beak. Six teeth are preserved in the premaxilla and maxilla, three in the
dentary. They are conical and slightly recurved.
Seven heterocoelous cervicals are preserved.
The last three dorsal vertebrae are articulated with the sacrum. At least
nine pairs of dorsal ribs are present, with at least five pairs of uncinate
processes. The uncinates are not fused to the ribs, slightly expanded
distally and decrease in length posteriorly. At least six rows of
gastralia are also present. Eight vertebrae make up the synsacrum, the
last three of which have the longest transverse processes. Of those three,
the longest is on sacral seven. Four free caudals are preserved and
have transverse processes. The pygostyle is longer than the four free
caudals.
The scapula is blunt distally, while the
coracoid is strut-like and appears concave laterally. The furcula is
V-shaped with an interclavicular angle of 59 degrees. It has an elongate
hypocleidium and U-shaped shaft cross section. The sternum is basically
wider than long and semicircular in front. Two elongate posterolateral
processes are expanded distally and anteriorly separated from the sternal body
by notches. Posteriorly, there is an elongate medial process and two
smaller processes between it and the posterolateral processes. A carina is
developed posteriorly. At least four pairs of sternal ribs are present and
decrease in length posteriorly.
The humerus resembles enantiornithines in general
outline- sigmoid with a long low deltopectoral crest, strongly posteriorly
projected bicipital crest and distally projected internal condyle.
Compared to Enantiornis, the deltopectoral crest is longer, internal condyle
less distally projected, shaft more sigmoid, bicipital crest narrower and head
more developed internally. The humerofemoral ratio is 1.64, while the
radius is 89% of humeral length. The ulna is bowed, while the radius is
straight and 63% as wide. The carpus consists of a small radiale, large
triangular ulnare and semilunate unfused to the metacarpus. The metacarpus
is unfused, with the third metacarpal extending past the second. It
is about half as wide as the second and bowed laterally. The first digit
extends past metacarpal II and features a mid-sized ungual. On the second
digit, phalanx II-1 is slightly longer than II-2 and the ungual is larger than
that on digit I. Only two phalanges are present in the third digit, the
second which is tiny and triangular, but apparently not an ungual.
An ilium preserves a rounded preacetabular process
and a short pointed postacetabular process. The pubis is cranially convex,
with a pubic foot twice shaft width. The ischium is about 60% of pubic
length, with a reduced obturator process, straight shaft and well developed
posterodorsal process.
No femoral details are observable, but the tibia
has a strong fibular crest. It is unfused with the astragalocalcaneum, but
combined their length is only 7% longer than the femur. The fibula is
reduced, tapering distally so that it does not contact the calcaneum. The
tarsometatarsus is fused proximally, as are the distal tarsals. Metatarsal
I is curved, with a reversed first digit. Phalanx I-1 is elongate with a
moderately curved ungual. The metatarsals decrease in length medially, IV
is slightly narrower than II. The proximal phalanges are preserved,
but no details are available.
Contour feathers are preserved around the cervical,
pectoral and pelvic area. The flight feathers attached to the ulna appear
very short, but impressions of the distal sections may be present. The
extremely long arms and advanced flight adaptations show this taxon was volant
in any case.
Relationships-
Zhang et al. refer the genus to a new family and
order (Longipterygidae, Longipterygiformes) within the Enantiornithes.
They assigned it to the latter clade based on- elongate hypocleidium; "sternum
similar to that of Cathayornis and Eoalulavis"; metacarpal III longer than
metacarpal II. The first and third are found in the more basal form
Protopteryx, while the second is confusing. Eoalulavis has a very derived
sternum that is narrow without lateral processes and has a greatly expanded
posteromedial process. It is not similar to Cathayornis or Longipteryx in
any regard. Longipteryx's sternum is roughly similar to Cathayornis, like
a cross between it and Protopteryx. No sternal synapomorphies are apparent
that would unite Longipteryx with enantiornithines.
To determine Longipteryx's phylogenetic position,
it was added to my basal pygostylian character matrix of 36
characters. Included taxa are Confuciusornithidae, Protopteryx,
Longipteryx, Jibeinia, Enantiornithes and Euornithes. One most
parsimonious tree (54 steps, CI .81) was found-
______Confuciusornithidae
|______Protopteryx
|______Longipteryx
|______Jibeinia
|______Enantiornithes
|______Euornithes
When Liaoxiornis, "Archaeoraptor" or Eoenantiornis
were added, the first two grouped with Jibeinia+Ornithothoraces, while the
second was an ornithothoracine. They did not affect the
topology.
Longipteryx is more derived than confuciusornithids
based on- strut-like coracoid; interclavicular angle of furcula 70 degrees or
less; long hypocleidium; furcula laterally excavated; elongate posterolateral
sternal processes; ulna subequal or longer than humerus; less than four
phalanges on manual digit III; reduced manual unguals. It is more derived
than Protopteryx based on- more than seven sacral vertebrae; anterior sternal
edges at less than a 120 degree angle; narrow posteromedial sternal process;
noticeable processes medial to posterolateral sternal processes; manual
phalanx II-2 shorter than phalanx II-1; metatarsal V absent. It is less
derived than Jibeinia based on- gastralia present; posterior sternal processes
medial to posterolateral sternal processes not pointed; manual digit I longer
than metacarpal II. In addition, it lacks the following ornithothoracine
characters- scapula tapered distally; interclavicular angle of furcula 50
degrees or less; less than two phalanges on manual digit III. I feel the
evidence is good that Longipteryx is a non-ornithothoracine
pygostylian phylogenetically between Protopteryx and Jibeinia.
Reference- Zhang, F., Zhou, Z., Hou, L., and Gu, G.
2001. Early diversification of birds: Evidence from a new opposite bird.
Chinese Science Bulletin 46(11): 945-950.
Those who contact me offlist can get the English
pdf.
Mickey
Mortimer |