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Thought I forgot about it, didn't you? Well,
you'd be correct :-) . Here's chapter 27 of The Age of Dinosaurs in Russia
and Mongolia- Mesozoic Birds of Mongolia and the former USSR.
Kurochkin does a pretty good job with this
chapter. More illustrations would have been nice, but Soviet birds aren't
much to look at anyway. His phylogeny of enantiornithines is hard to
decipher. He seems to have two orders- the Alexornithiformes and
Euornithiformes. The former includes the Alexornithidae (Alexornis,
Gobipteryx, Kizylkumavis, Lenesornis, Nanantius, Neuquenornis, Sazavis,
Zhyraornis), Avisauridae (Avisaurus, Enantiornis, Soroavisaurus) and
Enantiornithidae (Gurilynia). The Euornithiformes includes Holbotia,
although it is unnamed in the chapter. There are several problems with
this arrangement. Enantiornis needs to be in the Enantiornithidae, which
would be a senior synonym of Avisauridae. I'm also weary of the
Enantiornithiformes not existing and the Euornithiformes existing without any
apparent named taxa included. I don't know what the official word on these
issues is though. The diagnoses for the groups are fairly extensive,
although nearly all taxa are too fragmentary to be assigned to a group based on
more than one character. Note that when alexornithids, avisaurids and
enantiornithids are referred to in the discussion below, it is merely in
accordance with Kurochkin's phylogeny and does not represent my feelings as to
the classification of enantiornithine taxa. The Alexornithiformes is
diagnosed by-
- cranial half of synsacrum low and
broad. True in Lenesornis and Zhyraornis. The sacrum
of Nanantius? valifanovi is said to be similar to those genera, but is not
described. No members of Kurochkin's Enantiornithidae or Avisauridae have
preserved sacra. Moreover, other enantiornithines that do preserve sacra
(Iberomesornis, Cathayornis, etc.) seem to have this character. This is
not surprising, as transversely broad sacral centra are characteristic of
coelurosaurs in general. Thus, I reject the character.
- synsacrum convex dorsally. Present in
Lenesornis and Zhyraornis, the former only slightly. Unknown in other
enantiornithines. This is also present in several coelurosaurs, including
Tyrannosaurus, Chirostenotes, Ornithodesmus, Saurornitholestes(?) and
Patagopteryx. It does not seem to be present in Gallimimus or
Velociraptor. I find this character invalid as well.
- acrocoracoid and coracoidal process narrow and
tapered. A proximal scapula is known in Nanantius? valifanovi and
Alexornis. Neuquenornis also has a scapula preserved. Compared to
the avisaurid Enantiornis, there is no significant difference in acromion
narrowness in Nanantius? valifanovi. The coracoideal process is more
prominent in the former however. Whether other alexornithids share the
character is unknown, as that of Alexornis is not figured in lateral or medial
view and Neuquenornis' is poorly preserved. This character cannot be used
to diagnose alexornithids.
- scapular facet and scapular glenoid fused.
I must admit I don't understand this character. The scapula and coracoid
are never fused in enantiornithines and no portions of either bone would be
expected to be separate from each other.
- shaft of coracoid strut-like and narrow. A
strut-like coracoid is synapomorphic of pygostylians. Nanantius?
valifanovi would appear to have an extremly slender coracoid, although it may be
in lateral view. Neuquenornis also has a slender coracoid, that of
Enantiornis being the next thinnest. Other enantiornithines grade into
increased coracoid width, culminating in Eoenantiornis. As the coracoid
width of Nanantius? valifanovi is uncertain and that of Enantiornis is so close
to Neuquenornis, this character is also rejected.
- shaft of coracoid with deep and short depression
dorsally. The dorsal coracoideal depression is characteristic of
Protopteryx and basal ornithothoracines. Although depth of the fossa is
difficult to gauge from descriptions and figures, the length is not much
different in Neuquenornis (55% of coracoid length) than in Enantiornis
(61%). I'm uncertain of the ratio in Nanantius? valifanovi.
Regardless, the 6% difference seems insignificant to me.
- entepicondyle strongly projected distally.
There is no distinct difference in this character between Enantiornis,
Kizylkumavis or Alexornis.
- no manual unguals. All enantiornithines
have manual unguals on digits I and II where known.
- ischium narrow. This element is unknown in
any supposed alexornithid (or enantiornithid or avisaurid for that
matter). Reason enough to reject it.
- tibiotarsus thin. This is not specific
enough, even ignoring the fact no avisaurids have preserved
tibiotarsi.
- metatarsal III straight. Not only is this
present in almost all enantiornithines (exceptions include Yungavolucris and
some Yixian taxa), including the avisaurids Avisaurus and Soroavisaurus, it is
also symplesiomorphic.
- metatarsals II-IV short and gracile. This
can only be determined if other elements are preserved in addition to the
metatarsus. This cannot be determined in avisaurids or enantiornithids and
so cannot be diagnostic of alexornithids.
Thus, alexornithids, as defined by Kurochkin,
cannot be differentiated from other enantiornithines. Avisaurids are
diagnosed by several characters, some the opposite of alexornithid characters
(scapular facet and scapular glenoid separated; ischium wide; tibiotarsus
straight and robust), so these don't need to be examined again. Other
characters are-
- deep fossa on cranial surface of scapula.
Only known in Enantiornis, as other avisaurids are known from metatarsi.
Thus it cannot be diagnostic of the group.
- metatarsal III with strongly transversely convex
dorsal surface. This is much more prominent in Neuquenornis than in
Avisaurus, as can be seen in Chiappe and Calvo (1994) fig. 8. This is
opposite of the distribution that would be expected by this
character.
- medial rim of trochlea of metatarsal III with
strong plantar projection. This is character 2 in Chiappe (1993) and is
found in Neuquenornis as well as Avisaurus and Soroavisaurus. It therefore
does not support the separation of Neuquenornis from the latter
taxa.
It can be seen that none of the
suggested characters unite Enantiornis with actual avisaurids or separate
Avisaurus and Soroavisaurus from Neuquenornis. The Enantiornithidae is
undiagnosed, I suspect it may be a typo. The Euornithiformes is also
undefined. In conclusion, I see no evidence to suggest Kurochkin's
phylogeny is correct and recommend not subdividing the Enantiornithes until more
studies are published.
The next section is a rundown of the taxa included
in the chapter. They are similar to my details segments, but not nearly as
detailed. This is because I lack the original descriptions of most, which
would be needed before I wrote a details segment I felt confident
in.
Bissekty birds
As all birds from the Bissekty Formation are known
from single elements, I've arranged them by which element is known, instead of
by species. This allows quick comparison between taxa where it is possible
and ephasizes both the paucity of known remains and the likelihood many of the
taxa are synonyms of each other. Keep in mind more specimens are known
than listed by Kurochkin, but only those mentioned by him in this chapter are
dealt with here.
Enantiornithes indet.
Coniacian, Late Cretaceous
Bissekty Formation, Uzbekistan (PO 3473) axis (13.5 mm)
Comments- This axis is said by Kurochkin to
resemble that of Nanantius? valifanovi because they share- craniocaudal
elongation; poorly developed cranial articular facets; lateral extensions of
cranial articular facets; broad dorsal neural arch with flat lamina that is
strongly projected caudally; low dorsal process; shallow lateral excavation of
body. They apparently differ only in size (218% larger than N?
valifanovi). Based on the fact they are so similar, I provisionally accept
assignment to the Enantiornithes, but not neccessarily to the Alexornithidae,
which Kurochkin suggests.
"Ichthyornis" minusculus Nessov 1990
Coniacian, Late Cretaceous
Bissekty Formation, Uzbekistan
Holotype- (PO 3941) dorsal
vertebra Ichthyornithiformes? indet.
Coniacian, Late Cretaceous
Bissekty Formation, Uzbekistan (TsNIGRI 43/11915) dorsal vertebra (6.9
mm)
Comments- The unnamed dorsal was originally
referred to Zhyraornis kashkarovi. Kurochkin assigns "I." minusculus
to the Alexornithiformes. These two vertebrae are gently
amphicoelous, with deep lateral depressions and a large neural canal (height
>60% of central height). This combination of characters is only known
in enantiornithines and ichthyornithiformes. "I." minusculus has a
D-shaped central articular surface, while the unnamed vertebra's is roughly
oval. The unnamed dorsal's parapophysis is placed anterior to the
transverse process, which suggest it is not enantiornithine. Perhaps it is
ichthyornithiform.
Zhyraornis Nessov 1984
Z. kashkarovi Nessov 1984
Coniacian, Late Cretaceous
Bissekty Formation, Uzbekistan
Holotype- (TsNIGRI 42/11915) anterior
synsacrum (7+ vertebrae) (27 mm)
Z. logunovi Nessov 1992
Coniacian, Late Cretaceous
Bissekty Formation, Uzbekistan
Holotype- (PO 4600) anterior synsacrum (5+
vertebrae)
Lenesornis Kurochkin 1996
L. maltshevskyi (Nessov 1986)
= Ichthyornis maltshevskyi Nessov 1986
Coniacian, Late Cretaceous
Bissekty Formation, Uzbekistan
Holotype- (PO 3434) anterior synsacrum (5+
vertebrae)
Platanavis Nessov 1992
P. nana Nessov 1992
Coniacian, Late Cretaceous
Bissekty Formation, Uzbekistan
Holotype- (PO 4601) mid synsacrum (3+ vertebrae)
Kuszholia Nessov 1992
K. mengi Nessov 1992
Coniacian, Late Cretaceous
Bissekty Formation, Uzbekistan
Holotype- (PO 4602) posterior synsacrum
Referred- (PO 4623) anterior
synsacrum Comments- These five sacra are all from the
same deposits, but differ slightly from each other. Where known, the first
vertebra is procoelous. Zhyraornis has a more ventrally concave sacrum
than Lenesornis. There is a longitudinal groove on the ventral surface of
Lenesornis and Kuszholia, a double ridge in Platanavis and nothing
in Zhyraornis. The second and third costal processes are largest in
Zhyraornis, but the third and fourth are largest in Lenesornis. The costal
processes are thick in Z. logunovi and Lenesornis, but thin in Z.
kashkarovi. The synsacrum itself is wider and more robust in the former
two as well as in Kuszholia. Both large costal processes project
posteriorly in Z. kashkarovi, the third does in Z. logunovi and none do in
Lenesornis. The transverse processes of the second sacral are more
prominent in Z. logunovi than Z. kashkarovi. Zhyraornis has pleurocoels in
the first two centra, Platanavis and Kuszholia both have pleurocoels in the
preserved vertebrae.
The completely fused synsacra place these taxa in
or close to the Pygostylia. Zhyraornis kashkarovi at least is
ornithothoracine, as it has more than seven sacral vertebrae. It is also
excluded from the Ornithurae due to the procoelous first centrum. This
suggests, but does not prove, Zhyraornis kashkarovi is an enantiornithine.
Z. logunovi and Lenesornis also have procoelous first centra, but the
uncertainty of their sacral number only allows classification as
non-ornithurine pygostylians. Because Z. logunovi is similar to Lenesornis
is some respects, and the amount of sacral variation in enantiornithines is
unknown at the moment, I don't feel certain in assigning Z. kashkarovi and Z.
logunovi to the same genus. I recommend referring to the species as
Zhyraornis? logunovi. Platanavis can only be placed in Pygostylia incertae
sedis. These taxa all seem distinct from each other, but are so
fragmentary it's difficult to assign them to a higher group. Kurochkin
assigns Zhyraornis and Lenesornis to the Enantiornithes based on the
abundant enantiornithine remains from the Bissekty Formation and comparison to
Nanantius? valifanovi. It must be noted that the sacral synapomorphies of
his Alexornithidae are not valid, so such comparisons must be viewed with
caution. In a note added after the acknowledgements, Kurochkin says
investigation of zhyraornithids and discussion with Panteleev shows they "do not
belong to the Enantiornithes or any other known fossil or living group of
birds". Interesting. Kurochkin assigns Platanavis to Aves incertae
sedis, which is more inclusive than my referral to Pygostylia incertae
sedis. He assigns Kuszholia to Aves incertae sedis as well, but notes
Nessov and Panteleev assigned it to the Patagopterygiformes. This was
because they share an enlarged pair of third transverse processes and a
ventrally convex synsacrum. The distribution of the first character is not
clear, while the second is absent in Patagopteryx, so this referral remains
suspect. I need more literature to distinguish Kuszholia from Lenesornis
and hypothesize on its phylogenetic relationships, although it seems
pygostylian.
Comparison to other non-ornithurine pygostylians is
difficult, as sacra of that group are poorly described, if described at
all. Iberomesornis differs from all three in having a ventral ridge and
being extremely broad. Patagopteryx is similar to Lenesornis and
Kuszholia, as its sacrum is wide and has a ventral groove. It is
also similar to Lenesornis because the third and fourth costal processes
are largest and perpendicular to the sacrum. It differs from Kuszholia
because it lacks pleurocoels and is procoelous posteriorly. Nanantius?
valifanovi is also similar to Lenesornis and Kuszholia in having a ventral
groove. This is a primitive coelurosaurian character however.
Euornithes indet.
proximal scapula (TsNIGRI 44/11915)
Coniacian, Late Cretaceous
Bissekty Formation, Uzbekistan
Comments- Originally regerred to Zhyraornis, this element was said by
Kurochkin to bear a certain similarity to enantiornithines. However, the
coracoid articulation is convex, a character only seen in euornithines.
Compared to Patagopteryx, it much more elongate and lacks a distinct neck
posteroventral to the glenoid. The scapula of Ambiortus has a longer, more
pointed acromion and a dorsal crest. Otogornis has a smaller
acromion. Enantiornis? martini Nessov and Panteleev
1993
Coniacian, Late Cretaceous
Bissekty Formation, Uzbekistan
Holotype- (PO 4609) proximal
coracoid Enantiornis? walkeri Nessov and Panteleev
1993
Coniacian, Late Cretaceous
Bissekty Formation, Uzbekistan Holotype- (PO 4825) proximal coracoid
Pygostylia indet.
Coniacian, Late Cretaceous
Bissekty Formation,
Uzbekistan Material- coracoid shaft (PO 4818)
Pygostylia indet.
Coniacian, Late Cretaceous
Bissekty Formation, Uzbekistan Material- proximal coracoid (PO 4819)
Pygostylia indet.
Coniacian, Late Cretaceous
Bissekty Formation, Uzbekistan coracoid shaft (TsNIGRI 56/11915)
Comments- The unnamed coracoids have actually been
named by Panteleev (1998), but I have yet to see the paper or hear about it on
the list, so I don't know what the names are. If anyone has the paper, I
would be interested to hear from you. They have dorsal fossae, which are
known in non-ornithurine pygostylians and Apsaravis. TsNIGRI 56/11915 has
a convex lateral margin, only known in enantiornithines and Jibeinia. The
two species referred to Enantiornis differ from that genus in having- narrower
coracoideal process; shorter acrocoracoid; distal broadening of proximal shaft;
narrower and more elongated coracoideal nerve foramen. E? walkeri has a
stouter coracoideal process and more gracile proximal shaft than E?
martini. While I have not seen the descriptions of these taxa, I doubt
such fragmentary material could be unambiguously assigned to Enantiornis, which
lived twenty million years later in Argentina. In all probability, these
species and PO 4819 could be assigned to the Enantiornithes based on the
scapular articulation, but I have yet to verify this.
reference- Panteleev, 1998. New species of
enantiornithines (Aves: Enantiornithes) from the Upper Cretaceous of Central
Kyzylkum. Russkii Ornitologicheskii Zhurnal. Ekspress-vy.pvsk 35:
3-15.
Kizylkumavis Nessov 1984
K. cretacea Nessov 1984
Coniacian, Late Cretaceous
Bissekty Formation, Uzbekistan
Holotype- (TsNIGRI 51/11915) distal humerus (5.1 mm
wide)
Ornithurae indet.
Coniacian, Late Cretaceous
Bissekty Formation, Uzbekistan
Material- (TsNIGRI 45/11915) humeral shaft Comments- Kizylkumavis is very similar to Alexornis
and Enantiornis. It differs from Alexornis because it has- broader dorsal
condyle; narrower intercondylar furrow; flexor process more distally
projected. It is less similar to Apsaravis and Confuciusornis and quite
different from Patagopteryx. This suggests it is an
enantiornithine.
The humeral shaft was originally referred to
Zhyraornis kashkarovi, but Kurochkin refers it to the Ornithurae because the
nutrient foramen is found on the opposite side of the shaft compared to
enantiornithines. Sazavis Nessov 1989
S. prisca Nessov 1989
Coniacian, Late Cretaceous
Bissekty Formation, Uzbekistan
Holotype- (PO 3472) distal tibiotarsus (4.5 mm wide)
Comments- This tibiotarsus is obviously pygostylian based on the completely
fused astragalocalcaneum, tubercle on the ascending process and reduced
fibula. It is more derived than confuciusornithids based on the medial
condyle projecting more anteriorly than the lateral condyle. The large
medial condyle excludes it from the Ornithurae. This leaves the
Enantiornithes and a few more basal (Jibeinia, Protopteryx) and derived
(Patagopteryx) forms. Kurochkin assigns it to the Enantiornithes based on
many of the above characters, but some other taxa also show that combination of
features.
Comparison to other taxa is limited. Lectavis differs because-
lateral condyle does not project laterally; medial condyle mediolaterally larger
compared to lateral condyle; medial condyle projects further anteriorly.
Another tibiotarsus from the Lecho Formation (Walker 1981,
fig.2bB) also has a more reduced lateral condyle. The medial condyle
in this specimen doesn't project as medially as Sazavis. Boluochia
apparently differs in having subequal medial and lateral condyles.
The issues involving using single traits to classify taxa and of Boluochia's
position as an enantiornithine should be evident, but this is not the place to
discuss them. Vorona has a narrower medial condyle that extends
further proximally and a less prominent lateral condyle. The medial
condyle doesn't extend as far anteriorly, the condyles are not as distinct
anteriorly in distal view and the tibiotarsus is anteroposteriorly longer
compared to mediolateral width. Patagopteryx differs in having a laterally
concave lateral condyle that is tapered distolaterally an probably a narrower
medial condyle. Sazavis resembles the Lecho enantiornithines most, so I
think that it should provisionally be assigned to the Enantiornithes.
Horezmavis Nessov 1983
H. eocretacea Nessov 1983
Coniacian, Late Cretaceous
Bissekty Formation, Uzbekistan
Holotype- (PO 3390) proximal tibiotarsus
Enantiornithes indet.
Coniacian, Late Cretaceous
Bissekty Formation,
Uzbekistan proximal tarsometatarsus (PO 3394)
Comments- Kurochkin assigns Horezmavis to the Neognathae and questionably
to the Gruiformes. Horezmavis is euornithine based on the complete fusion
of its metatarsus and not ornithurine based on the low intercondylar eminance
and is not neornithine based on the lack of distinct hypotarsal crests.
The ventrally displaced proximal third metatarsal is more derived than
Patagopteryx.
PO 3394 has metatarsals fused only proximally, characteristic of
non-euornithine pygostylians. In addition, the fourth metatarsal is
strongly reduced, seen only in enantiornithines.
So for the time being, the table below represents my thoughts regarding the
classification of Bissekty birds. Taxonomic assignments are bound to
become more specific as I acquire the original descriptions and a few pertinant
enantiornithine papers.
Pygostylia
Kuszholia mengi Lenesornis maltshevskyi Platanavis nana Zhyraornis? logunovi Jibeinia+Ornithothoracines clade
Enantiornis? martini Enantiornis? walkeri (PO 4818) coracoid (PO 4819) coracoid (TsNIGRI 56/11915) coracoid Ornithothoracines
Ichthyornis? minusculus Zhyraornis kashkarovi Enantiornithes
Kizylkumavis cretacea (PO 3394) metatarsus ? Sazavis prisca ? (PO 3473) axis Euornithes
Horezmavis eocretacea (TsNIGRI 44/11915) scapula Ornithurae
(TsNIGRI 45/11915) humerus Ichthyornithiformes
? (TsNIGRI 43/11915) dorsal vertebra Other Soviet birds
Some other birds are known from Soviet countries, most are
fragmentary.
Asiahesperornis Nessov and Prizemlin 1991
A. bazhanovi Nessov and Prizemlin 1991
Late Santonian-Early Campanian, Late Cretaceous
Eginsai Formation, Kazakhstan
Holotype- (IZASK 5/287/86a) tarsometatarsal shaft (~122 mm)
Referred- (IZASK 5/287/86) two dorsal vertebrae, distal tibiotarsus,
tarsometatarsal shaft
Comments- This species is currently unstable. It must be reexamined
to determine if any apomorphies are present. In addition, the referred
tarsometatarsal shaft was provisionally assigned to a new species by Nessov and
Yarkov (1993) and the dorsals and tibiotarsus referred to as
"hesperornithiformes".
Hesperornis rossicus Nessov and Yarkov 1993
Early Campanian, Late Cretaceous
unnamed formation, Volgograd Province, Russia; unnamed formation, Scone,
Sweden
Holotype- (VPM 26306/2) proximal tarsometatarsus Referred- proximal tarsometatarsus
Comments- The holotype differs from H. regalis because the proximal
articular surface is deeper and the lateral cotyla is more proximally
projected. This species was originally named H. rossica, but must be
emended to rossicus as Hesperornis is masculine.
Hesperornis sp. nov.
Early Campanian, Late Cretaceous
unnamed formation, Volgograd Province, Russia
Material- proximal tarsometatarsus
Comments- A tarsometatarsus differing from H. rossicus was found at the
same locality. It differs in the more medially located intercotylar
prominence and larger ridge in the dorsal base of the intercotylar
prominence.
Hesperornis sp. indet.
Early Campanian, Late Cretaceous
unnamed formation, Volgograd Province, Russia Material- cervical vertebra fragment, dorsal vertebra fragment,
tarsometatarsal shaft, pedal phalanx IV-? Comments- Hesperornithid material found at the same locality as H. rossicus
and H. sp. nov. cannot be referred to either. It was originally referred
to H. rossicus.
Volgavis Nessov and Yarkov 1989
V. marina Nessov and Yarkov 1989
Danian, Paleocene
unnamed formation, Volgograd, Russia
Holotype- (PO 3638) anterior mandible, surangular fragment
Comments- This taxon was originally thought to be from the Late
Maastrichtian, but the deposits where it was discovered are now thought to be
Danian. In any case, the dentaries are fused, slender, decurved and
edentulous. It's presumedly a neornithine, assigned by Kurochkin to the
Limnofregatinae (Fregatidae, Pelecaniformes).
Praeornis Rautian 1978
P. sharovi Rautian 1978
Late Jurassic
Balabansai Formation, Kazakhstan
Holotype- (PIN 2585/32) feather?
Comments- Normally, I wouldn't include a feather taxon, but this one is
rather controversial. A photo is included and really doesn't look like a
feather to me. The shaft is much too wide (about one fourth the total
feather width) and the barbs are pointed spine-like structures without
barbules. Despite this, SEM data (Glazunova et al. 1991) and an analysis
by Unwin and Bakhurina suggest it actually is a feather. I'll have to see
those analyses to believe it.
Mongolian birds
This a topic several of you have asked about in the past. There
are actually quite a few birds from Mongolia, some well preserved.
Gobipteryx Elzanowski 1974
G. minuta Elzanowski 1974
Late Campanian, Late Cretaceous
Baruungoyot Formation, Mongolia
Holotype- (ZPAL MgR-I/12) anterior skull and mandible
Referred- (ZPAL MgR-I/32) anterior skull and mandible
Comments- This is a fairly well known genus, so a detailed description
isn't neccessary. Kurochkin brings up two odd points regarding it
however. First, he says that because comparable material is limited to
Nanantius? valifanovi, the enantiornithine status of Gobipteryx is
uncertain. I have no idea why he ignores the numerous Chinese
enantiornithines (which he refers to on page 544) that have excellent skull
material. Here's a question I have- are the holotype and paratype all
that's known of Gobipteryx? I thought some postcrania was known as well
(or is everyone referring to the embryos?). Second, he says the presence
of an ectopterygoid is "further confirmation of the relationship between the
Enantiornithers and Archaeornithes and their assignment to a phylogenetic
lineage separate from ornithurine birds". He continues, "This and some
other cranial synapomorphies support a theropodan origin for Sauriurae, but not
all birds". First of all, the presence of an ectopterygoid is not a
sauriurine synapomorphy, as it is present in reptiles (tetrapods?)
basally. Does he expect ornithurines to have evolved from an ancestor that
lacked ectopterygoids? Secondly, the idea "sauriurines" evolved from
theropods while ornithurines evolved from something else (probably ABSRD) is
preposterous. The numerous synapomorphies shared by all pygostylians,
theropod synapomorphies shared with ornithurines and intermediate taxa
(Patagopteryx, etc.) show this idea is fundamentally flawed. Kurochkin
refers Gobipteryx to the Alexornithidae, but without comparable material, I find
this hard to justify. Gobipteryx's closest relative seems to be Nanantius?
valifanovi, based on the elongate toothless premaxillae and toothless
dentary. It differs in having a narrow dentary with subparallel dorsal and
ventral edges, unlike the deep triangular dentary of N? valifanovi.
Besides N? valifanov, Boluochia is the only other enantiornithine with a
toothless premaxilla. It differs in having a decurved beak with a convex
ventral margin posteriorly and a toothed dentary.
Nanantius? valifanovi Kurochkin 1997
Late Campanian, Late Cretaceous
Baruungoyot Formation, Mongolia
Holotype- (PIN 4492-1) premaxilla, frontal, palate, anterior dentary, ten
partial cervical vertebrae, anterior sacrum, four caudal vertebrae, pygostyle,
proximal scapula, incomplete coracoid, furcula fragment, incomplete humerus (~42
mm), incomplete radius (~40 mm), incomplete ulna, metacarpal II, phalanx II-1,
metatarsal III, phalanx III-1, incomplete ilium, distal pubis, incomplete femur
(~40 mm), tibia (60 mm), fibula, metatarsus (22 mm), pedal phalanges and
unguals
Comments- This is a very well preserved specimen, especially for an
enantiornithine. Unfortunately, I lack the original description and must
rely on the abridged version in the book and the photo of the skeleton.
The tibiotarsus shares several characters with Nanantius eos from the Early
Cretaceous of Australia, including- laterally bowed shaft; caudal intercotylar
prominence on proximal surface; fibular shaft located on craniolateral edge of
shaft; elongate fossae along cranial and caudal bases of fibular crest.
These characters are not present in Cathayornis, Concornis, Lectavis or
Neuquenornis. While this suggests N? valifanovi is more closely related to
Nanantius eos than to those other taxa, the paucity of well described
enantiornithine tibiotarsi and large geographic and temporal distance makes me
wary of making the species congeneric. I suggest referring to the species
as Nanantius? valifanovi. The completeness of this specimen makes it very
important to deciphering enantiornithine phylogeny. As stated above, the
skull is most similar to Gobipteryx. The coracoid looks more slender than
other enantiornithines, although the perspective may exaggerate this.
There is a small, posteriorly projected pubic foot. Metatarsals II and IV
are subequal in thickness, unlike other enantiornithines. More complete
comparisons must await examination of the primary literature. Eggshells
were found in association with the specimen. These are laevisoolithid,
which links this type of eggshell with enantiornithines. Gurilynia Kurochkin 1999
G. nessovi Kurochkin 1999
Late Campanian-Early Maastrichtian, Late Cretaceous
Nemegt Formation, Mongolia
Holotype- (PIN 4499) proximal coracoid, proximal and distal ends of humerus
(26.2 mm wide proximally), ulna, radius, carpometacarpus
Comments- The humerus of this taxon looks very similar to Enantiornis and
the Spanish hatchling. Several characters (distinct dorsal depression;
prominent posteriorly projecting bicipital crest; etc.) suggest it is an
enantiornithine.
Enantiornithes indet.
Late Campanian, Late Cretaceous
Baruungoyot Formation, Mongolia
Material- (ZPAL MgR-1/33; ZPAL MgR-1/34; ZPAL MgR-1/88) embryos
Gobipipus Chatterjee, Kurochkin and Mikhailov 1998?
G. reshetovi Chatterjee, Kurochkin and Mikhailov 1998?
Holotype- (PIN 4492-3) embryo
Comments- Several embryos were described by Elzanowski (1981) and later
referred to Gobipteryx minuta. Later, Chatterjee, Kurochkin and Mikhailov
described two more embryos as a new neornithine bird, Gobipipus reshetovi.
All of these specimens are described by Kurochkin as enantiornithine embryos, as
the chapter was apparently written before he helped name Gobipipus.
The embryos described by Elzanowski are enantiornithine, as seen by the
reversed scapulocoracoid articulation. Kurochkin argues they are not
referrable to Gobipteryx, but this is questionable for two reasons. First,
the differences noted (larger and more cranially concave naris; sharper angle
between lateral edges of premaxilla; flat, rounded beak) could very well
be ontogenetic. Secondly, it is uncertain how much the incorrectly
associated Gobipipus specimens are affecting his opinion. I would need
access to the original description and the description of Nanantius? valifanovi
to have an educated opinion.
Gobipipus lacks teeth, has subequal metacarpals II and III, one phalanx on
manual digit II and a curved pointed scapula with prominent acromion.
Some characters (elongate fibula, tibia unfused to astragalocalcaneum, etc.) are
no doubt due to immaturity. Placing this genus phylogenetically will be
difficult with only embryonic remains available.
Holbotia Kurochkin 1991
H. ponomarenkoi Kurochkin 1991
Hauterivian-Barremian, Early Cretaceous
Andaikhudag Formation, Mongolia
Holotype- skull, pectoral, forelimb and hindlimb elements
Comments- This taxon is extremely poorly known and no, it's still not
officially described. Kurochkin refers to it as "the Kholboot
specimen". He assigns it to the Euornithiformes within the Enantiornithes,
for reasons never explained. It is toothed, has a V-shaped furcula with an
elongate hypocleidium and proximally fused metatarsi. Such a combination
of characters is only known in enantiornithines and some more basal taxa
(Protopteryx, Jibeinia). I would therefore place it as a non-euornithine
pygostylian more derived than confuciusornithids.
Hesperornithidae cf. Parahesperornis
Late Campanian-Early Maastrichtian, Late Cretaceous
Nemegt Formation, Mongolia
Material- distal tibiotarsus (11.7 mm wide)
Comments- This was originally referred to as Baptornis sp. (Kurochkin
1988), but Kurochkin finds it is closest to Parahesperornis based on- no distal
projection of the medial condyle, extensor groove placed extremely
medially.
Judinornis Nessov and Borkin 1983
J. nogontsavensis Nessov and Borkin 1983
Late Campanian-Early Maastrichtian, Late Cretaceous
Nemegt Formation, Mongolia
Holotype- (PO 3389) incomplete dorsal vertebra (14.1 mm)
Comments- Kurochkin places this in the Hesperornithiformes based on- very
expanded caudal ventral surface of centrum; narrow prezygopophyses; very deep
pleurocoels; transversely expanded cranial and caudal articular surfaces.
He assigns it to the Baptornithidae based on- small pit lies directly anterior
to transverse process; centrum flat ventrally; circular pit in central articular
surfaces. The generic diagnosis is- trapezoid-shaped central articular
surfaces extend transversely; prezygopophyses close together on midline.
The hesperornithiformes are outside my area of expertise, so I cannot comment on
the validity of these characters.
Hesperornithiformes fam. et gen. nov.
Late Campanian-Early Maastrichtian, Late Cretaceous
Nemegt Formation, Mongolia
Material- (PIN 4491-8) incomplete tarsometatarsus
partial mandible, cervical vertebra
Comments- Hesperornithiform characters include- inclined cross section of
tarsometatarsal shaft; high proximal position of second trochlea; proximal
position for facet of metatarsal I. Supposedly diagnostic characters are-
tarsometatarsus stout and short; metatarsal shaft transversely expanded.
This sounds like every hesperornithiform metatarsus I've seen, but what do I
know. The fact these bones are small and highly pneumatized suggests to
Kurochin this species was volant.
Ambiortus Kurochkin 1982
A. dementjevi Kurochkin 1982
Hauterivian-Barremian, Early Cretaceous
Andaikhudag Formation, Mongolia
Holotype- (PIN 3790-271, PIN 3790-272) cervical vertebrae, scapula,
coracoid, partial sternum, furcular ends, proximal humerus, partial radius,
partial ulna, carpometacarpus, phalanx II-1, phalanx II-2, manual ungual
II
Comments- The heterocoelous cervicals and normal scapulocoracoid
articulation place this species in the Euornithes. The flattened
manual phalanx II-1 shows it is ornithurine. The procoracoid process shows
it is a carinate. The lack of a pneumatic foramen in the humerus excludes
it from the Neornithines. Kurochkin places this genus in the Ambiortidae
with Otogornis and includes this family in the Palaeognathae. I
provisionally disagree, although I am not very familiar with ornithurines and
haven't examined the taxon in depth.
Presbyornithidae indet.
Late Campanian, Late Cretaceous
Baruungoyot Formation, Mongolia
Material- tarsometatarsus (40.3 mm)
Well, that's it. Feel free to ask questions or request scans of
figures. Figures available are- Nanantius? valifanovi skeleton, Gurilynia
proximal humerus and proximal coracoid, Gobipipus skeleton, cf. Parahesperornis
distal tibiotarsus, Hesperornithiformes fam. et gen. nov. tarsometatarsus,
Ambiortus skeleton, Praeornis feather. I'll need to get some more
references on these taxa and write details segments...
Mickey
Mortimer |