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Finally......done.....with......Caudipteryx.......must.....sleep
:-)
Caudipteryx Ji, Currie, Norell and Ji
1998
Diagnosis- premaxillary teeth limited to rostral
half; first premaxillary tooth much larger than others; single maxillary
fenestra present; twenty-two caudal vertebrae; sternal plates oval; only two
phalanges present on manual digit III; metatarsal III extremely narrow
proximally, but not arctometatarsalian.
C. zoui Ji, Currie, Norell and Ji 1998
?= Caudipteryx dongi Zhou and Wang
2000
Etymology- "Zou's tail feather", referring to Zou
Jiahua, vice-premier of China and an avid supporter of the scientific work in
Liaoning.
Barremian, Early Cretaceous
Yixian Formation, Liaoning, China
Holotype- (NGMC 97-4-A) (890 mm) skull (76 mm),
lower jaws, cervical vertebae, cervical ribs, dorsal vertebrae, dorsal ribs,
gastralia, twenty-two caudal vertebrae, chevrons, coracoid, sternal plate (36
mm), humeri (69 mm), radii, ulnae, mani, ilia, pubes, ischia (77 mm), femora
(147 mm), tibiae (188 mm), astragali, calcanea, metatarsi (115 mm), pedes, body
feathers, retrices, remiges, gastroliths
Paratype- (NGMC 97-9-A) (725 mm) incomplete skull
(79 mm), lower jaws, hyoid, cervical vertebrae, cervical ribs, dorsal vertebrae,
dorsal ribs, sacrum, caudal vertebrae, chevrons, scapulae, coracoids, sternal
plates, sternal ribs, humeri (70 mm), radii, ulnae, incomplete mani, partial
pubes, femora (149 mm), tibiae (182 mm), astragali, calcanea, metatarsi (117
mm), pedes, body feathers, retrices, remiges, gastroliths
Referred- (IVPP V 12344, holotype of Caudipteryx
dongi) (896 mm) frontal, pterygoid, two cervical vertebrae, six dorsal
vertebrae, dorsal ribs (100 mm), three uncinate processes (30 mm), gastralia,
sacrum, eleven caudal vertebrae, chevrons, partial coracoid, sternal plates (25
mm), sternal ribs (35 mm), incomplete humeri (~73 mm), radii (~58 mm), ulnae (61
mm), semilunate carpal, radiale, ulnare, metacarpal I (13 mm), phalanx I-1 (25
mm), manual ungual I (15 mm), metacarpal II (29 mm), phalanx II-1 (18.5 mm),
phalanx II-2 (25 mm), manual ungual II (18 mm), metacarpal III (27 mm), ilia
(115 mm), pubes, ischia (73 mm), femora (146, 152 mm), tibiae (196 mm), fibula
(181 mm), astragali, calcaneum, distal tarsal III, distal tarsal IV, metatarsal
I (19 mm), phalanx I-1 (12 mm), pedal ungual I (11 mm), metatarsal II (112 mm),
phalanx II-1 (25 mm), phalanx II-2 (16 mm), pedal ungual II (19 mm), metatarsal
III (124 mm), phalanx III-1 (27 mm), phalanx III-2 (20 mm), phalanx III-3 (17
mm), pedal ungual III (20 mm), metatarsal IV (116 mm), phalanx IV-1 (15
mm), phalanx IV-2 (9 mm), phalanx IV-3 (7 mm), phalanx IV-4 (7 mm), pedal ungual
IV (16 mm), metatarsal V (~36 mm), body feathers, remiges (182 mm),
gastroliths
Diagnosis- premaxilla sharply pointed anteriorly;
quadratojugal posterior process slightly developed; manual ungual II larger than
manual ungual I.
C. sp. nov.*
Barremian, Early Cretaceous
Yixian Formation, Liaoning, China
* see discussion Specimens- (BPM 0001, referred to Caudipteryx zoui)
(852 mm) skull, lower jaws, twelve cervical vertebrae, cervical ribs, nine
dorsal vertebrae, dorsal ribs (~114 mm), uncinate processes, gastralia, sacrum,
twenty-two caudal vertebrae, chevrons, scapulae (80 mm), coracoids (34 mm),
sternal plates (~30 mm), sternal ribs (~38 mm), humeri (72 mm), radii (59 mm),
ulnae (62 mm), semilunate carpal, radiale, ulnare, metacarpal I (11 mm), phalanx
I-1 (25 mm), manual ungual I (16 mm), metacarpal II (28 mm), phalanx II-1 (17
mm), phalanx II-2 (24 mm), manual ungual II (15 mm), metacarpal III (25 mm),
phalanx III-1, phalanx III-2, ilia (115 mm), pubes (~124 mm), ischia (72 mm),
femora (145 mm), tibiae (188 mm), fibulae (188 mm), astragali, calcanea, distal
tarsal III, distal tarsal IV, metatarsal I (16 mm), phalanx I-1 (13 mm), pedal
ungual I (12 mm), metatarsal II (102 mm), phalanx II-1 (23 mm), phalanx II-2 (16
mm), pedal ungual II (19 mm), metatarsal III (113 mm), phalanx III-1 (24 mm),
phalanx III-2 (19 mm), phalanx III-3 (15 mm), pedal ungual III (18 mm),
metatarsal IV (107 mm), phalanx IV-1 (14 mm), phalanx IV-2 (8 mm), phalanx IV-3
(6 mm), phalanx IV-4 (4 mm), pedal ungual IV (14 mm), metatarsal V (30 mm), body
feathers, remiges, retrices, gastroliths
(IVPP V 12340, referred to Caudipteryx sp.) (836
mm) skull, lower jaws, twelve cervical vertebrae, cervical ribs, nine dorsal
vertebrae, dorsal ribs (120 mm), uncinate processes (26 mm), gastralia, sacrum,
twenty-two caudal vertebrae, chevrons, scapulae (80 mm), coracoids (35 mm),
sternal ribs (36 mm), humeri (69 mm), radii (~56 mm), ulnae (61 mm), semilunate
carpal, radiale, ulnare, metacarpal I (11 mm), phalanx I-1 (26 mm), manual
ungual I (16 mm), metacarpal II (28 mm), phalanx II-1 (19 mm), phalanx II-2 (24
mm), manual ungual II (15 mm), metacarpal III (23 mm), phalanx III-1, phalanx
III-2, ilia (112 mm), pubes (~125 mm), ischia (~72 mm), femora (145 mm), tibiae
(183 mm), fibulae (175 mm), astragali, calcanea, distal tarsal III, distal
tarsal IV, metatarsal I (15 mm), phalanx I-1 (12 mm), pedal ungual I (12 mm),
metatarsal II (102 mm), phalanx II-1 (22 mm), phalanx II-2 (14 mm), pedal ungual
II (17 mm), metatarsal III (112 mm), phalanx III-1 (23 mm), phalanx III-2 (17
mm), phalanx III-3 (13 mm), pedal ungual III (18 mm), metatarsal IV (106
mm), phalanx IV-1 (12 mm), phalanx IV-2 (8 mm), phalanx IV-3 (6 mm), phalanx
IV-4 (5 mm), pedal ungual IV, metatarsal V (31 mm), body feathers, remiges,
retrices, gastroliths
Diagnosis- large premaxillary subnarial process;
maxilla extended anteriorly with promaxillary fossa; external naris close to
antorbital fenestra in length; jugal strongly concave posterodorsally;
posterodorsal dentary process subequal in width to posteroventral process;
posterodorsal dentary process longer than posteroventral process; no
intramandibular joint; vomers do not extend past external nares?; ectopterygoid
very thin and C-shaped; twelve cervical vertebrae?; ventral margin of coracoid
irregular?; anterior margin of preacetabular process posteroventrally
oriented.
Description-
The various specimens referred
to Caudipteryx show quite a bit of variation. They will be described
together and the implications for the number of species and individual variation
will be discussed afterward.
Skulls are illustrated for BPM
0001, IVPP V 12430 and NGMC 97-9-A. A complete skull is shown in the
skeletal drawing of NGMC 97-4-A, but not illustrated in detail. A frontal
and possible pterygoid are known in IVPP V 12344, but not illustrated in detail
either. The skull is fairly short, with a snout taking up about half the
length. Contra Zhou et al., the external naris is not larger than the
antorbital fenestra once the specimens are articulated. It is much
smaller in NGMC 97-9-A, but only slightly smaller in BPM 0001. It extends
to the rostral border of the antorbital fenestra. The maxilla has a very
small contribution to the external naris. The orbits are large and round,
while the laterotemporal fenestrae are shorter and dorsoventrally
elongate. The latter are broadest in IVPP 12430 and smallest in NGMC
97-9-A. The premaxilla is gently rounded
anterodorsally, with a slightly convex ventral margin. There is an
elongate narial fossa anteroventral to the external naris. The premaxilla
is lower and more triangular in NGMC 97-9-A, with a narrower external naris,
more vertical maxillary suture and shorter, narrower subnarial process.
The naris is widest in BPM 0001, while the subnarial process is largest in IVPP
V 12430. The ventral edge appears to have three notches in BPM 0001, while
it is smooth in IVPP V 12430 and NGMC 97-9-A. The premaxillae are unfused
and contain teeth in the anterior half. There are four procumbant teeth,
the first is by far the largest. Teeth are serrationless and constricted
at the base. The maxilla is reduced, with
narrow ascending and posterior processes. The latter is much shorter in
IVPP 12430 and thicker in BPM 0001. A single maxillary fenestra is
present; there does not seem to be much of an antorbital fossa. BPM 0001
and IVPP V 12430 have an elongate anterior portion with a pneumatic fossa, while
NGMC 97-9-A is blunt anteriorly without accessory fossae. Maxillae are
toothless. The nasal is shorter or subequal
to the frontal in length. The nasals lack rugosities and are
unfused. The lacrimal is triradiate,
with an elongate posterior process, suggesting the prefrontal is fused to
it. While the processes are 120 degrees apart in IVPP V 12430, the
anterior and posterior processes are 160 degrees apart in BPM 0001. There
is a large pneumatic lacrimal foramen, but no rugosities or horns are
evident. The jugal is relatively low,
although not rod-like. The anterior process is more elongate in
IVPP V 12430 and NGMC 97-9-A. The dorsal process is much more robust in
BPM 0001 and IVPP V 12430 than in NGMC 97-9-A , but contacted the postorbital in
all of them. The posterior process is shortest and not visibly
bifurcated. The frontal is roughly
triangular, with an elongate anterior section seemingly overlapped by the
nasal. The orbital rim is raised and ventral impressions indicate a large
brain. The frontals seem fused in BPM 0001, but separate in NGMC
97-9-A. The frontonasal suture appears anteriorly convex.
The triradiate postorbital is much larger in BPM
0001 and IVPP V 12430 than in NGMC 97-9-A. The anterior process is
expanded in the first two, while it is shorter and tapered in the latter.
The posterior process is broad in the former two, but shorter and tapered in the
latter. The ventral process is much more slender and elongate in NGMC
97-9-A, compared to the other two specimens. Because of these differences,
I believe the unlabeled element preserved directly anterior to the detached
ventral postorbital process in NGMC 97-9-A is actually the main postorbital
body. It is much larger and more similar in shape to the postorbitals of
BPM 0001 and IVPP V 12430, but the possibility remains it is a lacrimal or
jugal. The supposed postorbital then may be the other quadratojugal.
The parietal is poorly preserved in all
specimens, but appears subequal to the frontal in length and quadrangular.
The squamosal is also poorly preserved, but has
an elongate tapered ventral process and a hooked posterior process that exposes
the quadrate head laterally. The ventral process contacted the
quadratojugals dorsal process. The
quadratojugal is not triradiate and has a dorsal process more elongate than the
anterior process. Both processes are narrow and tapered.
The quadrate is single-headed, with a gently
concave posterior margin and a deep notch ventrally. It is vertical and
not pneumatic. The braincase is visible in
BPM 0001 and NGMC 97-9-A, but shows no details besides several large
foramina. The broad posterior portion of the pterygoid is preserved in BPM
0001, contacting the quadrate. Another similar element is unidentified in
IVPP V 12430. An L-shaped element, tapered on one end and slightly
expanded on the other, is identified as a possible pterygoid in IVPP V
12430. I can't see how this can be a pterygoid (although my grasp of
three-dimensional palates is poor) and think it resembles a quadratojugal
more. A large irregular element in BPM 0001 is identified as a
palatine. This does not resemble any palatine I have seen, but is not
triradiate. In BPM 0001, there are two pointed elements projecting
posterodorsally from the anteroventral margin of the external naris that Zhou et
al. identify as vomers. If that is true, they are very short compared to
other theropods, as they extend only halfway past the external nares. A
thin, C-shaped element in IVPP V 12430 is identified as an ectopterygoid.
This is dissimilar from both the dumb-bell shaped ectopterygoids of oviraptorids
or the hook-shaped ones of most theropods, although it is most similar to the
latter. The ectopterygoid of NGMC 97-9-A is more robust, with the usual
thickened portion seen in most theropods. Several other cranial elements
are also difficult to identify. Two elongate elements preserved in the
snout of IVPP V 12430 could be vomers or vomeral processes of the
palatines. A vertical strap-like element, wider than the lacrimal and
found in the antorbital fenestra, defies identification but is present in all
three specimens. A small element in the naris of BPM 0001 is very similar
to a coronoid, but its position makes this identification suspect.
Curiously, two scleral plates are preserved in NGMC 97-9-A, but not in other
specimens.
The dentary is toothless with
two long posterior processes. The ventral process is longer than the main
dentary body in BPM 0001 and IVPP 12430, but shorter in NGMC 97-9-A. The
processes are subequal in length in the first two, but the dorsal process is
half as long in the latter. The dorsal process is much narrower than the
ventral in NGMC 97-9-A, but wider in BPM 0001 and IVPP V 12430.
Anteroventrally, the dentary is concave. Medially, a shallow mackelian
groove seems to be present in NGMC 97-9-A and BPM 0001. The symphysis is
well-developed, but not fused. The external mandibular fenestra is 39% in
BPM 0001 and 33% in IVPP V 12430. The surangular and dentary may
be fused in these specimens, but are loosely joined in the former. Ji
et al. (1998) claim the intramandibular joint in NGMC 97-9-A was
mobile, but this could not have been the case in BPM 0001 and IVPP V
12430. A ventral surangular process crosses the external mandibular
fenestra in BPM 0001 and extends partway into it in NGMC 97-9-A, but not in IVPP
V 12430. If a surangular foramen was present, it was very
small. The angular is large, unlike oviraptorids, and connot be
distinguished from the articular. The mandibular joint is not extremely
convex, unlike caenagnathoids. The retroarticular process is moderately
elongate, narrower in NGMC 97-9-A. An elongate bone ventral to the
surangular (and fused angular?) in IVPP V 12430 is probably the other
surangular/angular in medial view, based on a posteroventral tubercle also seen
in the surangular/angular of BPM 0001. A splenial is identifiable in IVPP
V 12430, it is acutely triangular with a notched posterior edge. There is
no indication it could be seen in lateral view. Another much larger
element is identified as the splenial in BPM 0001, but appears to be a straight
narrow prearticular instead. The prearticular of IVPP V 12430 is probably
visible behind the dorsal dentary process. Another elongate element in BPM
0001 is more problematic. It is a bit larger than the splenial should be,
triangular and has a notch posterodorsally. Perhaps it is an oddly shaped
splenial. A slender, tapered hyoid is seen in NGMC 97-9-A.
An element labeled "?" by Zhou
et al. located behind the skull of IVPP V 12430 looks like an atlantal
neurapophysis to me. It is triangular, with a small process on one
corner. Ten cervicals are reported by Ji et al., while Zhou et al.
estimate twelve. They are amphicoelous and have slender
unfused ribs. The axial neural spine is prominent and expanded, the
neural spine of the third cervical is tall and rectangular. More posterior
cervical neural spines are low. Prominent cervicodorsal hypapophyses are
said to be present. Zhou et al. report nine dorsal vertebrae. They
are procoelous and reported to lack deep pleurocoels. Currie (pers. comm.
2000) states pleurocoels are present anteriorly, but not posteriorly.
Details are hard to make out, but the dorsals appear longer than Nomingia, with
slightly shorter quadrangular neural spines. Nine pairs of dorsal ribs are
present, the fourth the longest. Three uncinate processes are preserved in
IVPP V 12344, four in BPM 0001 and six in IVPP V 12430. On the latter
specimen, they are present on the first six dorsal ribs. The second, third
and fourth processes are longest. They are flat, slightly curved and
expanded ventrally. Gastralia are also present. There are five
sacral vertebrae, unfused in IVPP V 12344. The tail contains twenty-two
vertebrae, none are fused into a pygostyle. The centra lack pleurocoels
and decrease in length posteriorly. Twelve to fifteen have transverse
processes, the last seven have elongate prezygopophyses. It appears the
centra may be grooved ventrally and are not procoelous. The last chevron
is after the seventeenth caudal. Dorsoventrally elongate chevrons are
present until after the tenth caudal, all but the first are distally
expanded. No dromaeosaur-like highly elongated prezygopophyses or chevrons
are present.
The scapula is gently curved and
gradually expanded distally to 2.4 times minimum shaft width. The acromion
forms a prominent, though broad, anteriorly projecting process. The
scapulocoracoid suture is broad, unfused in NGMC 97-9-A and IVPP V 12430, but
fused in BPM 0001. The coracoid is subrectangular and taller than
long, though not as much as in dromaeosaurids. A prominent triangular
posteroventral process is present. There is a large coracoid tubercle and
a foramen located near the scapulocoracoid suture. The glenoid seems to
point mostly posteroventrally. The furcula is broad (interclavicular angle
~90) and U-shaped, probably without a hypocleidium. Two oval sternal
plates are present, smaller than the coracoids. There is no keel or
lateral processes. Several sternal ribs are preserved, they are straight,
flatter than dorsal ribs and longer than the sternum.
The humerus is poorly described,
but lacks a pneumatic fossa and a well-developed olecranal fossa. It is
relatively straight, slender and has a low deltopectoral crest. The radius
is slnder (~60-80% of ulnar width) and the ulna is bowed posteriorly. The
carpus consists of a large semilunate, triangular radiale and small rounded
ulnare. There are three unfused metacarpals. The first is 39-45% the
length of the second. It lacks an extensor process. Phalanx I-1 is
longest, so the first digit reaches well past metacarpal II. The first
manual ungual is moderately curved with a well-developed flexor tubercle, but
lacks a proximodorsal lip. It is slightly larger than the second manual
ungual in BPM 0001 and IVPP V 12430, but smaller in NGMC 97-4-A and IVPP V
12344. Phalanx II-2 is longer than phalanx II-1. The second manual
ungual is similar to the first, but has a lower flexor tubercle.
Metacarpal III is very slender, straight and slightly shorter than metacarpal II
(82-93%). There are only two phalanges in manual digit III. They are
both very small, the second smallest, and do not reach past the midpoint of
phalanx II-1. There is no ungual.
The pelvis is propubic and
unfused. The ilium has a long ventrally expanded preacetabular process and
rounded, posteroventrally sloped postacetabular process. The preacetabular
process is 15-29% longer than the postacetabular process. The anterior
margin is anterodorsally oriented in IVPP 12344, but posteroventrally oriented
in IVPP V 12430. The anterodorsal margin is higher than the posterodorsal
margin and is rounded anteriorly. The pubic peduncle reaches further
ventrally than the ischial peduncle does. It is slightly anteroventrally
oriented and notched ventrally, although this is not seen in lateral view.
The m. cuppedicus fossa is shallow and reduced. The pubis is nearly
straight and has an anterior foot much larger than the posterior. The
pubic symphysis extends about halfway up the shaft, which is not compressed
mediolaterally. The ischium is 58% of pubic length. It lacks any
posterior processes, but does have a large triangular obturator process placed
60% down the shaft. It is concave posteriorly.
The greater and lesser
trochantors are separated by a small notch, while the greater trochantor is well
separated from the head. There is no distinct fossa for the capital
ligament, and no transverse ridge bounding the popliteal fossa. The tibia
is anteroposteriorly elongate when viewed proximally. The fibula is very
slender, but extends distally to contact the calcaneum. The astragalus and
calcaneum are not fused to the tibia, and are separate from each other as
well. The ascending process of the astragalus extends 22% up the tibia and
is broad and triangular. There is a shallow groove or fossa separating the
process from the condyles. Two unfused distal tarsals are present.
The unfused metatarsus is elongate and although the third metatarsal is very
narrow, it is not arctometatarsalian. Rather, it expands proximally after
reaching it's narrowest point at midlength. The first metatarsal is
placed two thirds down on the posteromedial surface of the second metatarsal and
has a ball-shaped distal end. It is at least partially reversed. The
phalanx is short and stout, while the small ungual is more curved than the
others. The second metatarsal is 90-91% the length of the second, the
fourth is 94-95%. The second digit shows no predatory specializations-
there is no proximoventral heel on phalanx II-2 and the ungual is subequal in
size to the others. Unlike eumaniraptorans, the first phalanx of digit II
is less than 90% of phalanx III-1. The fifth metatarsal is 27-29% of the
third in length.
The body was covered with small
plumulaceous feathers up to 14 mm long. At least fourteen remiges are
present on metacarpal II, phalanx II-1 and phalanx II-2. They lengthen
proximally (30, 63.5 and 95 mm long starting with most distal), are symmetrical
and have well-developed rachis and vanes. Barbules seem not to have been
present. Eleven retrices are present on each side of the tail. They
are attached to the last six caudals. These are also symmetrical.
Small rounded gastroliths are preserved in all specimens, measuring up to 4.5 mm
in diameter, although most are less than 4 mm.
Comparison of specimens-
Five specimens of Caudipteryx
have been described. NGMC 97-4-A, NGMC 97-9-A and BPM 0001 are
referred to the type species, C. zoui. IVPP V 12344 was referred to a new
species, C. dongi. IVPP V 12430 was referred simply to C. sp..
Zhou and Wang differetiated C. dongi from C. zoui based on the smaller
sternum and longer first metacarpal. Most differences I can see between
the specimens are cranial, although this may be due to the fact the skulls are
well illustrated, while the postcrania is not. Are these differences real
or preservational? A large amount of the variety seems to be due to
crushing and distortion. For instance, there is no way the lacrimal of
IVPP V 12430 could have had such a small angle between its anterior and
posterior processes in life. Similarily, the posterior postorbital process
of BPM 0001 is much too long, as it would extend well past the quadrate when
articulated. The anterior squamosal process of that specimen is much too
large and bulbous, as it would reach through the postorbital and into the
orbit. More evidence that distortion has occured might come from
the asymmetry in specimens. The dentaries visible in medial view is always
deeper and more decurved, with a more pronounced chin, than the dentaries
visible in lateral view. This is very unusual and I lack a good
explanation. Perhaps Caudipteryx had an asymmetrical lower beak in life
(like crossbills- Loxia), although the larger side is the left in two specimens
and the right in the other. I provisionally consider this oddity due to
distortion, although the other possibility is quite intriguing. The dorsal
cranial elements (nasal, frontal, parietal) are often distorted and
asymmetrical. The differences least likely to be due
to distortion or individual variation support BPM 0001 and IVPP V
12430 being separate from NGMC 97-9-A. Characters these two specimens
share not found in the latter are- premaxilla blunt anteriorly; large
premaxillary subnarial process; maxilla extended anteriorly with promaxillary
fossa; external naris close to antorbital fenestra in length; jugal strongly
concave posterodorsally; quadratojugal posterior process not developed;
posterodorsal dentary process subequal in width to posteroventral process;
posterodorsal dentary process longer than posteroventral process; no
intramandibular joint. Most of the postcranium is not figured in
sufficient detail to determine morphological differences in specimens. The
differing number of reported cervical vertebrae might be due to
misinterpretation, as Zhou et al. state "there are estimated twelve cervical
vertebrae". The coracoid has a smoothly rounded ventral border in NGMC
97-9-A, unlike the irregular border of BPM 0001, although the significance
of this is uncertain. The orientation of the anterior preacetabular edge
differs in IVPP V 12344 and IVPP V 12430, but as the skull of the former is
fragmentary, it cannot be determined if this is correlated with the cranial
differences noted above. Contra Zhou and Wang, no significant differences
in postcranial ratios is evident. Most ratios vary within a few percentage
points of each other, so fall within the expected range of individual
variation. The sternal plates are 24% of femoral length in the holotype of
C. zoui, 17% in the holotype of C. dongi and an intermediate 21% in BPM
0001. A three percent difference in size does not seem to fall outside the
range of individual variation. The first metacarpal of BPM 0001 and IVPP V
12430 is 39% of metacarpal II length. In IVPP V 12344, the ratio is
45%. This difference might be considered diagnostic if not for NGMC
97-4-A, which has a 42% ratio. Although stated to be "about .4" in Zhou
and Wang, this figure comes from Ji et al., who only measured to the tenths
place. The exact ratio, as mentioned above, is intermediate between
the more divergent specimens. Once again, the 3% difference is considered
insufficient to diagnose a species. The ilium is much shorter in NGMC
97-4-A (69% of femoral length) than in BPM 0001, IVPP V 12344 and IVPP V 12430
(77-79%). This is due to the broken anterior edge in the former specimen
however, as can be seen in my photo on the Dinosauricon. The only
potentially significant proportional difference between specimens is- manual
ungual I vs. manual ungual II (106% in BPM 0001 and IVPP V 12430, 84% in IVPP
12344). Although the first manual ungual of NGMC 97-4-A is incomplete, it
was much smaller than manual ungual II, so seems to match IVPP V 12344
better. A complete chart of proportions can be found at the end of this
post (copy and paste to a text program such as Notepad to view
correctly). It therefore seems that BPM 0001 and IVPP V 12430 share
several cranial characters not seen in NGMC 97-9-A; NGMC 97-9-A has a slightly
different coracoid morphology than BPM 0001; BPM 0001 and IVPP V 12430
have a different preacetabular morphology than IVPP V 12344; and that BPM
0001 and IVPP V 12430 have different manual ungual ratios than IVPP V 12344 and
NGMC 97-4-A. Two groups of specimens are suggested by these differences-
IVPP V 12344, NGMC 97-4-A and NGMC 97-9-A are one group, while BPM 0001 and IVPP
V 12430 are in the other. The inclusion of IVPP V 12344 and NGMC 97-4-A
with NGMC 97-9-A is far from certain, but the fact they all differ from the
other two specimens and that the latter two have similar ungual ratios suggests
this may be the case. Are these differences due to ontogenetic, sexual or
taxonomic variation? The minute size variation (femur 145-152 mm) suggests
it is not ontogenetic. Settling whether two sexes or species are involved
is not easily resolved with only five specimens to work with, all from different
localities. One potential way to decide this would be if the groups are
not sister groups in a phylogenetic analysis.
Relationships-
Caudipteryx has been included in
several phylogenetic analyses. Much of the following is modified from my
earlier e-mails.
Ruben and Jones (2000) support
the hypothesis Caudipteryx is a secondarily flightless bird. They argue
against the theropod status of Caudipteryx by refuting the three "unambiguous
characters" cited by Ji et al. (1998) that birds have and it lacks. They
say the quadratojugal cannot be proven to have been sutured with the quadrate,
as they do not contact in the holotype and show a photo of the specimen which
differs in this aspect from the figure in Ji et al.. Oviraptorid specimens
GIN B and ZPAL MgD-I/96 (Maryanska and Osmolska, 1997) show a cotylar
articulation between the two bones and Velociraptor has a reduced loose contact
(Barsbold and Osmolska, 1999), so the character wouldn't mean much even if
they are correct (the cranial elements of Caudipteryx are loosely
articulated and sutures between most cannot be seen). They claim the
quadratojugal is far too short to contact the squamosal. New specimens
confirm this is incorrect. Finally, "an obturator process may or may not
exist in Caudipteryx, but, in any case, a similar structure is also known to
have occured in some birds (e.g., Concornis)." First of all, they
articulate the ischia upside-down, which is confirmed as being incorrect by the
new specimens. Secondly, they misstate the character, which was to have a
reduced or absent obturator process. I personally don't think
Archaeopteryx has a reduced obturator process, but Concornis has a very reduced
process. Ruben and Jones present no convincing evidence Caudipteryx is a
bird.
Martin and Czerkas (2000) also
argue Caudipteryx is a bird, one more derived than Archaeopteryx. The
evidence presented is-
- teeth with expanded roots. Also in
troodontids, Archaeornithoides, Microraptor, alvarezsaurids (which Martin
considers ornithomimosaur relatives), etc.
- primary feathers. This is circular reasoning, as feathers are the only reason the authors argue against Caudipteryx being a dinosaur. - carpus with at least four bones. Actually, there are three, but more are present in allosaurids, segnosaurs, tyrannosaurids and ornithomimids anyway. - absence of pubic foot. Completely false (Zhou and Wang, 2000; Currie pers. comm. 1999). - reflexed hallux. The hallux is said to be partially reversed, but a fully reflexed hallux is present in Rahonavis and MIcroraptor in any case. - shortened tail. While the tail of
Caudipteryx is shorter than any other non-avian theropod (and Archaeopteryx,
Rahonavis and Yandangornis), it is not fused at all. The character
"shortened tail", properly quantified, would be a potential
Caudipteryx-pygostylian synapomorphy.
It's more derived than Archaeopteryx based on: - no maxillary or dentary teeth. Enantiornithines and ornithurines primitively lack this. Is Caudipteryx supposed to be a carinate? Many dinosaurs (ornithomimids, oviraptorosaurs) also have this. - external mandibular fenestra present. Plesiomorphic and present in virtually all theropods, while absent in a couple enantiornithines and maybe Archaeopteryx. - enlarged premaxilla. No more than oviraptorids. - reduced maxilla. Correlated with the above character and also present in oviraptorids. - reduced hypopubic cup. Plesiomorphic and present in nearly all dinosaurs anyway.... - ball-shaped femoral head. Plesiomorphy only absent in Archaeopteryx and Rahonavis. - reduced fibula. False (Ji et al., 1998), but present in troodontids, etc. anyway. - reduced calcaneum. Less reduced than troodontids :-) - greatly shortened tail with evidence of pygostyle formation. See above. In conclusion, "shortened tail" is the only character presented by critics that is a potential Caudipteryx-pygostylian synapomorphy. Several new discoveries surprisingly add evidence to this hypothesis, including the possible low dorsal vertebral count and the reduced third manual digit. Still, even when these are added to a phylogenetic analysis, the non-avian hypothesis is much more parsimonious. Originally thought of as a non-avian avialan by Ji, Currie, Norell and Ji (1998), recently it has been allied with oviraptorids. Ji et al. made Caudipteryx sister group to avians based on two characters- unserrated teeth; premaxilla reaches to anterior border of antorbital fossa. As only the premaxilla is toothed in Caudipteryx, and premaxillary teeth are often unserrated in coelurosaurs (juvenile tyrannosaurids, ornithomimosaurs, compsognathids, Byronosaurus, Sinornithosaurus, avians, etc.), this character is suspect. The second character is also seen in oviraptorids and more bird-like taxa (Bambiraptor, Sinornithosaurus), so can also be dismissed. Even Currie (1999 Ostrom Symposium) now places it as an oviraptorosaur. Sereno (1999) groups it as an
oviraptorosaur basal to caenagnathids and oviraptorids. This was based on
twelve characters.
- ventral margin of external naris dorsal
to maxilla. Not true in Caudipteryx, as can be clearly seen in BPM
0001.
- premaxilla participates in antorbital
fossa. There does not appear to be much of an antorbital fossa in
Caudipteryx. The promaxillary fossa is clearly separated from the
premaxilla by a raised anterior maxillary rim.
- nasal shorter than frontal. The frontal
length is difficult to determine in Caudipteryx. The nasals are
shorter in NGMC 97-9-A, but longer in BPM 0001. The frontals are
impossibly long in IVPP V 12430, as the orbit would be intersected by the jugal
dorsal process. This suggests the long anterior portion of the frontals
was overlapped by the nasals. This would also explain why the nasals are
longer in BPM 0001, which is articulted, while the disarticulated NGMC 97-9-A
shows the opposite condition. Thus, when articulated, the nasals
would appear longer than the frontals. I use the character "nasals
subequal in length to frontals", which is diagnostic of a more inclusive group,
as it is present in the oviraptorosaur outgroup Erlikosaurus.
- ventral margin of dentary inset medially for
dentary and surangular. This would be very difficult to determine from
crushed two-dimensional specimens such as are preserved at Liaoning.
Moreover, in BPM 0001 and IVPP V 12430, the maxilla ventrally overlaps the
dentary and surangular on their lateral sides, suggesting the opposite
condition. Thus, I do not consider the character an oviraptorosaur
synapomorphy.
- anterior process of jugal rod-shaped in cross
section. While the cross section of any element is nearly impossible to
determine from the literature, the jugal of Caudipteryx is comparable to
compsognathids, Ornitholestes, Scipionyx, ornithomimids, segnosaurs and many
other coelurosaurs in slenderness. On the other hand, oviraptorids have
rod-like jugals comparable to Avimimus, Shuvuuia and pygostylians. Because
of this, I do not consider this an oviraptorosaurian character.
- palate mostly ventral to maxilla and jugal.
This is also not easy to determine in Caudipteryx. However, I consider it
unlikely based on a few observations. First, there is no indication of a
ventrally projecting maxillary palate. Secondly, the vomers may be
incredibly short and posterodorsally projected, in no position to reinforce
maxillary "teeth". Finally, the C-shaped ectopterygoid would not be able
to function like a strut between the maxilla and pterygoid. These
features make it improbable that Caudipteryx had a ventrally projecting palate
and the character is rejected as an oviraptorosaur synapomorphy.
- dentary dorsal margin convex. This is also
present in therizinosauroids, so was a more inclusive character.
- external mandibular fenestra 40% of lower jaw
length. Only confuciusornithids have such long mandibular fenestrae.
Oviraptorids vary from 26-36%, while Chirostenotes has a 27% ratio and
Caudipteryx varies between 33-39%. Change the ratio to 25% and it becomes
a defensible oviraptorosaur character.
- caudal centra twice as wide as tall. The
disarticulated caudal vertebrae of NGMC 97-9-A (visible in ventral view) show
this not to be the case in Caudipteryx.
- anterior caudal transverse processes (1-8) twice
length of neural spines. This is hard to determine when the vertebrae are
preserved in lateral view, but the eighth caudal of NGMC 97-9-A is preserved in
anterior (or posterior) view and seems to have transverse processes subequal in
length to the neural spine.
- acromion prong projected anteriorly or
anterodorsally. This is valid, although paralleled in most
eumaniraptorans.
So most of Sereno's evidence for referring
Caudipteryx to the Oviraptorosauria is not valid. An external mandibular
fenestra over 25% of mandibular length and an anteriorly or anterodorsally
projected acromial prong do support this assignment.
Holtz (1999 Ostrom Symposium)
found it to either be a basal maniraptoran or a basal member of the
segnosaur-oviraptorosaur group. His more recent analysis from SVP 2000
places it as an oviraptorosaur- sister group to Nomingia, which are in turn the
sister group to Microvenator and caenagnathoids.
Although they did not perform a
phylogenetic analysis, Zhou and Wang (2000) came to a similar conclusion, that
it is either a basal oviraptorosaur or a basal paravian. Xu, Wang and Wu
(1999) and Xu, Zhou and Wang (2000) (with near-identical analyses) also find it
to be a basal paravian. Norell, Makovicky and Clark (1999 Ostrom
Symposium) place Caudipteryx in a troodontid + segnosaur + oviraptorosaur group
that is sister group to the Eumaniraptora. Zhou et al. (2000) admit that
although cladistic analysis places Caudipteryx as a non-avian dinosaur, this is
based on the untestable principle of parsimony and hypothetically no amount of
characters could not have been reversed in a basal avian. This could just
as easily be true if reversed (an infinite amount of bird-like characters could
have evolved in parallel) and therefore is as good as saying "we can never know
for sure what anything is related to". While this may be true, there are
ways to test the probability one hypothesis is superior, which in this case is
parsimony.
My analysis of 322 characters
and 47 coelurosaur taxa* independently agree with Holtz's 2000 analysis.
Caudipteryx is oviraptorosaurian based on- toothless maxilla; pneumatic
lacrimal; prefrontal absent; frontal subequal in length to parietal; two long
caudal dentary processes; dentary toothless; external mandibular fenestra more
than 25% of lower jaw in length; retroarticular process long and tapering; no
interdental plates; thin, rod-like prearticular?. It is the sister group
of Nomingia based on- less than eleven dorsal vertebrae; tail less than 2.5
times femoral length; less than twenty-five caudal vertebrae; some distal caudal
prezygopophyses elongate. It is more basal than Microvenator and
caenagnathoids based on- distal caudals lack transverse processes; distal
prezygopophyses elongate. When both groups of Caudipteryx
specimens are included as separate OTU's, they are sister groups.
This leaves open both possibilities- that the differences are sexual or
taxonomic. I think the variation is too great to be sexual, but that is
simply my undefendable personal preference. I therefore recommend
Caudipteryx dongi be provisionally synonymized with C. zoui and that BPM 0001
and IVPP V 12430 be referred to as Caudipteryx sp. nov. until a more in depth
study is published. Those who want to place all specimens in C. zoui are
welcome to do so, as this is largely a subjective matter until a better study is
completed or more specimens are discovered.
* Adding four characters and separating the
Caudipteryx groups changed the results somewhat. Siamotyrannus has been
kicked out of the Tyrannosauroidea and is now next to the outgroup (smile Nick
:-) ). Ornitholestes is not maniraptoriform, but other examined "basal
coelurosaurs" are maniraptoran. Bagaraatan is now in a polytomy with
"basal coelurosaurs", segnosaur-oviraptorosaurs and paravians.
Troodontids, Avimimus+alvarezsaurids and Achillobator+eumaniraptorans are in a
polytomy. The Dromaeosauridae has standardized, with Dromaeosaurus and
Adasaurus in the Dromaeosaurinae and Velociraptor, Deinonychus and
Saurornitholestes in the Velociraptorinae. Bambiraptor, Sinornithosaurus,
Microraptor, Unenlagia, Rahonavis and Archaeopteryx are successive outgroups to
Yandangornis and pygostylians (sorry, no more secondarily flightless
dromaeosaurs).
There's a lot of scans I could send people.
The skull of NGMC 97-9-A and skeletons of NGMC 97-4-A and 97-9-A are
available. Additionally, high quality photos of these specimens I took at
the RTMP can be seen at- http://dinosauricon.com/artists/mm.html .
The skeleton, pelvis and pes of IVPP V 12344 are available, as are plates of the
torso and arm, ilia, pedes and feathers. The skull and pectoral girdle of
BPM 0001are available. The skull, distal caudals and hand of IVPP V 12430
are also available. Also, plates of the skeleton, pectoral girdle and
forelimbs, pelvis and pedes are available from BPM 0001; plates of the skeleton,
pectoral girdle, distal caudals and ilia and tibiae and fibulae of IVPP V 12430
can be requested. If you want any of these, just ask.
Appendix A: ratios of skeletal elements in
Caudipteryx.
1 2 3 4 5
6 7 8 9
IVPP V 12430 55 48 39 19 77 50 126 77 BPM 0001 55 21 50 41 19 79 50 130 78 NGMC 97-9-A 47 42 122 79 NGMC 97-4-A 24 47 42 69 52 128 78 IVPP V 12344 17 49 39 19 77 49 132 83 1. scapula/femur
2. sternal plate/femur 3. humerus/femur 4. radius/femur 5. mcII/femur 6. ilium/femur 7. ischium/femur 8. tibia/femur 9. mtIII/femur 1 1 1 1 1 1 1 1 1 1 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 BPM 0001 10 10 86 6 82 63 39 89 89 57 61 86 54 10 100 14 90 95 27 IVPP V 12430 12 10 88 7 81 63 39 82 93 57 68 86 54 11 96 13 91 95 28 IVPP V 12344 12 8 84 7 79 61 45 93 86 52 64 86 62 11 92 15 90 94 29 1. humerus width/length
2. ulna width/length 3. ulna/humerus 4. radius width/length 5. radius/humerus 6. manus/femur 7. mcI/mcII 8. mcIII/mcII 9. I-1/mcII 10. muI/mcII 11. II-1/mcII 12. II-2/mcII 13. muII/mcII 14. femur width/length 15. fibula/tibia 16. mtI/mtIII 17. mtII/mtIII 18. mtIV/mtIII 19. mtV/mtIII 2 2 2 2 2 2 2 2 2 2 3 3 3 3 3 3 3 3 3 3 4 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 BPM 0001 12 11 20 14 17 21 17 13 16 12 7 5 4 12 IVPP V 12430 11 11 20 13 15 21 15 12 16 11 7 5 4 13 IVPP V 12344 10 9 20 13 15 22 16 14 16 12 6 6 6 13 20. I-1/mtIII
21. puI/mtIII 22. II-1/mtIII 23. II-2/mtIII 24. puII/mtIII 25. III-1/mtIII 26. III-2/mtIII 27. III-3/mtIII 28. puIII/mtIII 29. IV-1/mtIII 30. IV-2/mtIII 31. IV-3/mtIII 32. IV-4/mtIII 33. puIV/mtIII Mickey Mortimer
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