Details on Jibeinia II

[Michael Mortimer <mickey_mortimer111@msn.com>]

This was written up for my website, though it's not uploaded yet.

Jibeinia Hou, 2000
= "Jibeinia" Hou, 1997
J. luanhera Hou, 2000
= "Jibeinia luanhera" Hou, 1997
Early Aptian, Early Cretaceous
Dawangzhangzi Beds of Yixian Formation, Hebei, China
Holotype- (IVPP collection; lost) (juvenile) partial skull, mandible (22 
mm), six cervical vertebrae (~2.4 mm), five dorsal vertebrae (~2.9 m), 
dorsal ribs, gastralia, sacrum, six caudal vertebrae, pygostyle (13 mm), 
scapula (20 mm), coracoids (11.5 mm), incomplete furcula, sternum (17 mm), 
humerus (23.3 mm), radius (24.2 mm), ulna (24 mm), semilunate carpal, 
ulnare, metacarpal I (2 mm), phalanx I-1 (4 mm), manual ungual I (2.5 mm), 
metacarpal II (9.3 mm), phalanx II-1 (6 mm), phalanx II-2 (3.7 mm), manual 
ungual II (2.1 mm), metacarpal III (8.3 mm), phalanx III-1 (1.5 mm), phalanx 
III-2 (2.9 mm), manual ungual III (1 mm), partial ilium, pubis (21 mm), 
partial ischium, femora (22.2 mm), tibiae (28 mm), astragali, calcanea, 
distal tarsal, metatarsal I, phalanx I-1, pedal ungual I, metatarsal II, 
phalanx II-1, phalanx II-2, pedal ungual II, metatarsal III (16.3 mm), 
phalanx III-1, phalanx III-2, proximal phalanx III-3, pedal ungual III, 
metatarsal IV, phalanx IV-1, phalanx IV-2, phalanx IV-3, phalanx IV-4, pedal 
ungual IV, feather impressions
Diagnosis- narrow furcular branches; metacarpal II does not extend past 
metacarpal II (?); three phalanges on manual digit III (?); trochlea of 
metatarsal II not wider than that of metatarsal III (?).
Comments- The name "Jibeinia luanhera" was first used in Hou (1997), but 
only in the captions of three illustrations. In the text, it was merely 
called Ji Bei bird (this is untrue in the English translation). Because the 
scientific name was not given in the text itself, "Jibeinia" was a nomen 
nudum. Later, Hou (2000) used the scientific name in the text of his 
semipopular Picture Book of Chinese Fossil Birds, with accompanying 
illustrations and disgnosis. This counts as the first official use of the 
name. Unfortunately, neither work contains trustworthy descriptions or 
accurate illustrations. The illustrations in Hou (1997) are hopelessly 
schematic, while the skeletal reconstructions in Hou (2000) aren't 
respresentative of bird anatomy, let alone that of Jibeinia itself. Hou's 
(1997) descriptions contain features not known in birds (e.g. septomaxillae, 
presternae) as well as numerous characters which clash with those described 
in more recent and better illustrated papers (e.g. Confuciusornis in Chiappe 
et al., 1999). In addition, the holotype is presently lost (Hou pers. comm., 
2001 to Zhang et al., 2004) and existing casts are of low quality. Thus all 
morphological details of Jibeinia are suspect, except the few which can be 
gleaned from published photographs.
Based on comparison with undoubted juvenile enantiornithines (Dalingheornis, 
Liaoxiornis, GMV 2158, GMV 2159, etc.), Jibeinia is near certainly a 
juvenile as well. Characters supporting this conclusion include- unfused 
sacrum; sternal keel absent; high interclavicular angle; humeral head not 
concave proximally; humeral distal condyles undeveloped, which in turn 
causes the ventral condyle to not project distally; carpometacarpus fusion 
absent; pelvic fusion absent; cnemial crest absent; tibiotarsal, proximal 
tarsal and distal tarsal fusion absent. Some of these characters are seen in 
most of the taxa described by Hou (1997), so may be due to the schematic 
illustration quality or incorrect description instead. Of the diagnostic 
characters listed by Hou (1997), most are symplesiomorphic for 
enantiornithines (numerous unserrated maxillary teeth; large, broad sternum; 
reduced manual digit III; fused pubic symphysis; metatarsals partially fused 
proximally and unfused distally; metatarsal II shorter than metatarsal III 
or IV) or ambiguous (extremely concave cervical centra; unexpanded distal 
pubes). The narrow posteromedian sternal process is present in almost all 
enantiornithines as derived as Longipteryx, while the final character 
(poorly developed posterolateral sternal processes) is problematic. The 
distal end of the right process is covered by another element, while the 
right process has a broader base which may be the remains of a large distal 
expansion. If the right side is more accurate, it would resemble Hebeiornis, 
while the left side could resemble Eoenantiornis. Another possibility is 
that the sternum is similar to Sinornis in possessing a small anterolateral 
process on the right side, with most of the posterolateral process broken 
off. Interestingly, if manual phalanx III-1 is actually a broken piece of 
metacarpal III, both the apparently short metacarpal III and presence of 
three phalanges on that digit would be resolved and the manus would resemble 
those of other enantiornithines. Hou previously claims Confuciusornis has 
five phalanges on manual digit III in the same book (again probably due to a 
broken element), so such a mistake by him would not be unheard of. It would 
still have two phalanges on the digit however, which would be like basal 
enantiornithines but unlike avisaurids.
Jibeinia exhibits several primitive characters for an ornithothoracine. It 
supposedly lacks a sternal keel, has three phalanges on manual digit III, 
and a metacarpal I which is unfused to the carpometacarpus. In addition, the 
unfused carpometacarpus and pelvis, absent cnemial crest and unfused 
tibiotarsus and tarsus are all near certainly juvenile characters, being 
more primitive than more basal avebrevicaudans like Sapeornis and 
Confuciusornis. However, Jibeinia exhibits a narrower interclavicular angle 
(~66 degrees) and less phalanges on manual digit III than confuciusornithids 
and most more basal maniraptorans. Because Jibeinia is probably a juvenile, 
it is unclear if some characters it possesses are due to being juvenile or 
being basal. The posteromedian sternal process is narrow as in 
enantiornithines, but the ventral humeral condyle doesn't appear to be 
distally projected, if the illustration can be trusted. The latter is the 
juvenile condition for enantiornithines, however. Metatarsal IV is reduced 
in width as in enantiornithines as derived as Lectavis. As in Protopteryx 
and more derived enantiornithines, the medial edge of metacarpal I appears 
to be convex, though metatarsal II's trochlea appears to be smaller in size 
than that of metatarsal III and metacarpal III ends far proximally to 
metacarpal II. The latter two characters are more primitive than Protopteryx 
and do not vary with age, though the trochlear size may be due to inaccurate 
illustration. The maxillary teeth and short ulna distinguish Jibeinia from 
protopterygids, even though the posteromedial sternal processes and possibly 
narrow metatarsal II trochlea are like Cuspirostrisornis, while the large 
interclavicular angle, unfused carpometacarpus and unfused distal tarsals 
are like Protopteryx. The latter three characters may be caused by ontogeny 
on Jibeinia or both taxa however. The presence of eight sacral vertebrae, 
and the absence of lateral coracoid processes and metatarsal V are similar 
to taxa as derived as Iberomesornis. Euenantiornithine characters include 
the narrow posteromedian sternal process and pneumotricipital fossa (unknown 
in more basal enantiornithines except Wyleyia), though the humeral head is 
apparently not concave proximally (if the illustration is accurate). The 
latter is true of juvenile euenantiornithines too though. The posteromedial 
sternal processes and short manual phalanx II-2 are shared with the 
Longipteryx+Enantiornis clade. The short rostrum and toothed maxilla are 
unlike longipterygids, though Jibeinia does share some characters with each 
longipterygid genus- a wide interclavicular angle and incompletely fused 
carpometacarpus with Longipteryx (both possibly ontogenetic in Jibeinia or 
both taxa), and elongate posteromedial sternal processes and a short manus 
with Longirostravis. The short manual digit I is like Dalingheornis and more 
derived taxa, while the convex lateral coracoid margin and very short manual 
phalanx II-2 are like Eocathayornis and more derived taxa. The short ulna is 
unlike Eocathayornis+Otogornis, and the multiple phalanges on manual digit 
III are unlike avisaurids, but the short manus is similar to the latter 
clade. Elongate posteromedial sternal processes are like cathayornithids, 
but the unenlarged pedal ungual I is unlike the Concornis+Neuquenornis 
subclade. Liaoningornithid synapomorphies are almost entirely lacking 
(Jibeinia has a short sternum with posterolateral and posteromedial 
processes, an unexpanded posteromedian process, distally unfused metatarsus 
and metatarsal IV reduced in width), except for the possibly unenlarged 
metatarsal II trochlea. Finally, the premaxillary teeth are unlike the 
Boluochia+Gobipteryx subclade.
When summed up, Jibeinia is most likely to be a basal cathayornithid of 
Eoenantiornis-Sinornis grade. The discordant characters are almost all 
potentially ontogenetic and due to Jibeinia's juvenile age. Not only are 
more basal positions less parsimonious, but the discordant characters are 
not those that could be explained by ontogeny, making such positions even 
more unlikely. For instance, a position sister to Protopteryx (as has been 
suggested by Zhou and Zhang, 2005) is at least 7 steps longer, even if the 
probably shared juvenile characters of Jibeinia and Protopteryx are counted 
as true synapomorphies.
Besides those characters listed in the diagnosis, probably non-ontogenetic 
differences from Eoenantiornis include the apparently more tapered rostrum, 
medial articular process, shorter manual digit I, broader penultimate manual 
phalanges, less curved manual unguals, and longer metatarsal IV. Differences 
from Sinornis include the more shallow anterior dentary, supposedly 
amphicoelous cervical vertebrae, narrow ventral tubercle of humerus, longer 
manual digit I, wider manual phalanx I-1, less reduced phalanx III-1/2, 
larger manual unguals, and apparently absent femoral neck. Yet even taxa 
with semiheterocoelous cervicals (e.g. Confuciusornis) are described as 
amphicoelous by Hou (1997), and central morphology varies with position in 
other enantiornithines.
Zhang et al. (2004) suggested Jibeinia may be a senior synonym of Hebeiornis 
(described by those authors as Vescornis), which they described from the 
same formation. This was based on their identical size and numerous similar 
characteristics. Indeed, it only takes one more step to place Jibeinia as a 
basal gobipterygid related to Hebeiornis. Besides those characters listed in 
the diagnosis, Jibeinia differs from Hebeiornis in- more shallow anterior 
dentary; elongate posteromedial sternal processes; narrow ventral tubercle 
of humerus; larger manual ungual I. Jibeinia supposedly has amphicoelous 
cervicals and dorsals, while Hebeiornis has heterocoelous cervicals and an 
opisthocoelous dorsal (but note the comment above regarding enantiornithine 
central articulations). Besides the numerous juvenile characters listed 
above (some of which Hebeiornis shows as well- unfused sacrum, metacarpal I 
unfused to carpometacarpus, proximal tarsals unfused to tibia), Jibeinia is 
younger based on supposed foramina between neural arches in the pygostyle, 
and its undeveloped distal femoral condyles. Based on comparison to 
Hebeiornis, the proximal coracoid of Jibeinia may be broken off, though Hou 
does describe it as having a rounded head. If it is complete, it is shorter 
than in Hebeiornis.
References- Hou, 1997. Mesozoic Birds of China. Phoenix Valley Bird Park, 
Lugu Hsiang, Taiwan. 221 pp.
Hou, 2000. Picture Book of Chinese Fossil Birds. Yunnan Science and 
Technology Press, Kunming, China.
Zhang, Ericson and Zhou, 2004. Description of a new enantiornithine bird 
from the Early Cretaceous of Hebei, northern China. Canadian Journal of 
Earth Sciences. 41(9), 1097-1107.