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In recent decades numerous findings, mostly from the Early Cretaceous of China, have changed traditional conceptions about the diversity and evolution of the most ancient Aves. Findings of Mesozoic birds in Russia are extremely rare. Here we describe a new bird from the Lower Cretaceous (Barremian–Aptian, Ilekskaya Svita) Shestakovo-1 locality (southern Western Siberia, Russia), that has also yielded dinosaurs, mammals, crocodiles, pterosaurs and lizards. Mystiornis cyrili gen. et sp. nov. is based on an isolated metatarsus which displays a mosaic of morphological features allowing us to create a new order, Mystiornithiformes. Mystiornis has a fully consolidated (ornithurine-like) gracile metatarsus with a primitive coplanar arrangement of the metatarsals, three separate proximal articular facets, and a uniquely located distal interosseal canal. It also displays diving adaptations previously documented only in Ornithurae.
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Journal of Systematic Palaeontology, Vol. 9, Issue 1, March 2011, 109–117
A new taxon of birds (Aves) from the Early Cretaceous of Western Siberia, Russia
Evgeny N. Kurochkina, Nikita V. Zelenkova, Alexandr O. Averianovband Sergei V. Leshchinskiyc
aProfsojuznaya 123, Borissiak Palaeontological Institute, Moscow 117997, Russia; bZoological Institute, Saint-Petersburg, Russia;
cTomsk State University, Tomsk, Russia
(Received 29 January 2010; accepted 6 July 2010)
In recent decades numerous findings, mostly from the Early Cretaceous of China, have changed traditional conceptions
about the diversity and evolution of the most ancient Aves. Findings of Mesozoic birds in Russia are extremely rare. Here
we describe a new bird from the Lower Cretaceous (Barremian–Aptian, Ilekskaya Svita) Shestakovo-1 locality (southern
Western Siberia, Russia), that has also yielded dinosaurs, mammals, crocodiles, pterosaurs and lizards. Mystiornis cyrili gen.
et sp. nov. is based on an isolated metatarsus which displays a mosaic of morphological features allowing us to create a new
order, Mystiornithiformes. Mystiornis has a fully consolidated (ornithurine-like) gracile metatarsus with a primitive coplanar
arrangement of the metatarsals, three separate proximal articular facets, and a uniquely located distal interosseal canal. It
also displays diving adaptations previously documented only in Ornithurae.
Keywords: Aves; Mystiornithiformes ordo nov.; Mystiornis gen. n.; Early Cretaceous; Russia; metatarsus
Introduction
Numerous findings from the Cretaceous of China have
greatly improved our knowledge of the early history of
birds, resulting in essential changes in traditional concepts
of the evolution of Mesozoic Aves (Chiappe & Witmer
2002; Kurochkin 2006; Zhou & Zhang 2007). By the
Early Cretaceous, enantiornithines were well established
and diverse; Ornithurae were present, as well as an aber-
rant primitive clade, the Confuciusornithidae. Simultane-
ously, the systematic position of some Cretaceous birds (e.g.
Jeholornis,Sapeornis,Zhongornis,Piksi,Zhongjianornis,
Hollanda,Vorona) has remained obscure: some are simply
identified as Aves incertae sedis, with unknown affinities to
the main lineages of Avialae (Varricchio 2002; Gao et al.
2008; Zhou & Zhang 2006b, Zhou, Zhang & Li 2010; Bell
et al. 2010). Plumage has been shown to be present in
several families of Theropoda (Xu & Guo 2009).
Outside China, Mesozoic birds have been described from
other regions of Asia, Europe, North and South America,
Africa, Australia and even Antarctica. These discoveries
testify to the degree of evolutionary experimentation that
characterized these birds, including numerous attempts to
master the air, parallel evolution of different groups, and
the absence of a direct connection between the origin of
flight and the occurrence of plumage (Zhou et al. 2003;
Kurochkin & Bogdanovich 2008a, b; Xu & Guo 2009).
Findings of Mesozoic birds in Russia are very rare
(Kurochkin 2000; Kurochkin et al. 2006). Here we describe
a new order of birds (Aves) from the Early Cretaceous
Corresponding author. Email: enkur@paleo.ru
(Barremian-Aptian, Ilekskaya Svita) Shestakovo-1 local-
ity in Western Siberia (Fig. 1). Dinosaur remains from
this locality have been known since 1953. Since the mid
1990s, employees of the Tomsk State University and the
Palaeontological and Zoological Institutes of the Russian
Academy of Sciences have discovered numerous mammals,
new crocodiles, pterosaurs and lizards in addition to diverse
dinosaurs (Alifanov et al. 1999; Lopatin et al. 2005). The
only avian find to date is an isolated metatarsus, collected
in 2000 by a joint team of Tomsk and Moscow palaeon-
tologists, showing a peculiar mosaic of ornithurine and
enatiornithine characters. This specimen is housed in the
Paleontological Museum of Tomsk State University (PM
TSU). Despite the isolated nature of the find, morphological
features of this metatarsus are considered both taxonomi-
cally significant and diagnostic, thus making it possible to
provide a taxonomic description. As the metatarsus in ques-
tion differs considerably from those of the main clades of
birds (see below), we believe it to represent a new order
within class Aves.
Systematic palaeontology
Class: Ave s Linnaeus, 1758
Order: Mystiornithiformes ordo nov.
Diagnosis. Metatarsals II–IV completely ossified, copla-
nar throughout their entire length, except for the separate
ISSN 1477-2019 print / 1478-0941 online
Copyright C
2011 The Natural History Museum
DOI: 10.1080/14772019.2010.522202
http://www.informaworld.com
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110 E. N. Kurochkin et al.
Figure 1. Map showing the location of the Early Cretaceous Shestakovo-1 locality in Western Siberia.
proximal ends of metatarsals III and IV. Metatarsals II–IV
each have isolated proximal concave articulate facets.
Dorsal surfaces of metatarsals II–IV tapered in the form of
longitudinal ridges. Fossa infracotylaris dorsalis not devel-
oped. Canalis interosseus distalis originates in the distal
part of sulcus extensorius and terminates on the proximal
wall of foramen vasculare distale.
Remarks. Mystiornithiformes differs from all other
known avians by the unique combination of apomor-
phies (coplanar ossification of metatarsals, development
of the longitudinal ridges on the dorsal surface, and
absence of fossa infracotylaris dorsalis) with autapo-
morphies (distinctive canalis interosseus distalis, three
concave proximal articulated facets). The coplanar arrange-
ment of three metatarsals is considered a primitive avian
condition (Chiappe 1996), since it is present in most
basal Avialae: Archaeornithes, Enantiornithes, Vorona,
Confuciusornithes, Sapeornis (Forster et al. 1996, 2002;
Zhou & Zhang 2002), and also in advanced theropods:
Alvarezsauridae, Rahonavis and non-avian maniraptors
(Chiappe et al. 2002; Clark et al. 2002). But in almost all of
these, the metatarsals are fused just proximally, with their
distal ends remaining either completely separate or tightly
attached. Nearly complete fusion of metatarsals II and III
is observed only in the Upper Cretaceous enantiornithines
Lectavis and Yungavolucris from Argentina, and Vorona
from Madagascar (Chiappe 1993; Forster et al. 1996,
2002). In contrast, Mystiornithiformes has three metatarsals
completely coalesced for almost all their lengths, except
for the divided proximal ends of metatarsals III and
IV and an oval, fissure-like foramen between the proxi-
mal parts of their shafts. Ornithurine birds (Neornithes,
Ichthyornithes, Hesperornithes, Early Cretaceous Chinese
Yixianornis,Yanornis,Hongshanornis and Gansus, and
also the Late Cretaceous Apsaravis and Vegavis)differ
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A new taxon of birds from the Early Cretaceous 111
in that the metatarsals are fully consolidated throughout
their entire lengths. However, in Ornithurae the proximal
part of metatarsal III submerges plantad, i.e. below the
level of metatarsal II and IV. Only the ornithuromorph
Archaeorhynchus from the Lower Cretaceous of China
and Patagopteryx from the Upper Cretaceous of Argentina
possess coplanarly fused metatarsals (Alvarenga &
Bonaparte 1992; Zhou & Zhang 2006a). The state of fusion
of the three metatarsals in Mystiornithiformes is close to
the condition seen in Ornithurae. Another peculiar feature
of the described bird is that its metatarsus is very gracile,
which is also characteristic of Ornithurae in contrast to
Enantiornithes.
The presence of three isolated concave articulate facets
(cotylae medialis, centralis and lateralis) on the proximal
surface of the metatarsals is not known for any group within
Ornithuromorpha. Normally only lateral and medial facets
separated by eminentia intercotylaris are present. Basal
Avialae with a coplanar arrangement of their metatarsals
(Enantiornithes, Confuciusornithes) lack eminentia inter-
cotylaris, but also only have two facets. In non-avian
theropods, each metatarsal bears a separate but convex artic-
ular facet (Barsbold 1983). However, in Dromeosauridae
these facets are concave.
The tapered dorsal surfaces of the metatarsals are also
characteristic of Avisauridae. In the Shestakovo specimen,
a longitudinal ridge is especially strongly developed on
the proximal half of metatarsal III, with a characteristic
expansion to the edge of the articular surface, consistent
with other avisaurids (Chiappe & Walker 2002). In all other
feathered and other Theropoda, these surfaces are usually
flattened (Weishampel et al. 2004).
Also characteristic of Mystiornithiformes is the absence
of an excavation (fossa infracotylaris dorsalis) in the proxi-
mal part of the dorsal surface of the metatarsus. This fossa,
with vascular foramens and tubercles for attachment of m.
tibialis cranialis, is well developed in the Ornithurae, but
absent in Patagopteryx, in which a submerged metatarsal
III is absent. The absence of this fossa and placement of the
tubercle for the m tibialis cranialis on the dorsal surface of
metatarsal II is consistent with enantiornithines.
The canalis interosseus distalis begins in Mystiornithi-
formes in the distal part of the sulcus extensorius and opens
inside the foramen vasculare distale, on its proximal wall.
Similar localization of the canalis interosseus distalis has
no analogue among known feathered theropods. In Ornithu-
rae, if such an interosseus canal is present, it begins on the
distal wall of the vascular foramen, perforates a bony bridge
between the distal ends of metatarsals III and IV, and opens
between the corresponding metatarsal trochleae. A foramen
vasculare distale is absent in the majority of the Enantior-
nithes, but is present in Avisauridae.
Fam ily Mystiornithidae fam. nov.
Genus Mystiornis gen. nov.
Type species. Mystiornis cyrili sp. nov.
Etymology. From mysterion (Gr.) – mysterious, and ornis
(Gr.) – bird. The gender is masculine.
Diagnosis. Proximal articular surface of metatarsal II posi-
tioned more distally than the proximal articular surfaces of
the other two metatarsals, but its plantar part protrudes prox-
imally beyond the level of the proximal articular surface.
Middle parts of metatarsal shafts and metatarsal trochleae
curved plantad. Plantar part of metatarsal II flattened medi-
olaterally and noticeably projected plantad. Metatarsal II
shortest of the three, tr. metatarsi II not reaching the level
of distal vascular foramen and strongly flattened dorsoplan-
tarly. Trochleae of all three metatarsals lying in different
planes, so their sagittal planes meet plantarly with sharp
angles.
Occurrence. Lower Cretaceous of Western Siberia,
Russia.
Remarks. Proximal articular surfaces of metatarsals II–IV
in all Enantiornithes and Vorona are positioned at the
same level. The condition in adult Ornithurae is differ-
ent since their proximal tarsometatarsus is formed by fused
distal tarsals, completely covering the proximal ends of the
metatarsals. However, in juvenile ornithurine specimens,
before fusion of the distal tarsals with the metatarsals, the
proximal ends of the metatarsals are at the same level (visi-
ble as well in the osteology of juvenile Ornithurae).
Plantar convexity of the metatarsal shafts is also char-
acteristic of some avisaurids (Soroavisaurus) and Vorona
(Chiappe 1993; Forster et al. 1996). Soroavisaurus also
shares with Mystiornis a flat metatarsal II with a tapered
plantar surface of its shaft. A strongly shortened metatarsal
II and similar mutual orientation of trochleae are charac-
teristic of the Early Cretaceous Gansus and the Late Creta-
ceous gaviiform Neogaeornis (Lambrecht 1929; Hou & Liu
1984; Olson 1992). In these birds, such structure is obvi-
ously connected with diving adaptations.
Mystiornis cyrili gen. et sp. nov.
(Fig. 2)
Holotype. PM TSU,16/5–45, left metatarsus.
Diagnosis. As for the genus.
Etymology. This species is dedicated to Cyril Walker.
Slim-legged, from leptos (Gr.) – slim, and kolon (Gr.) –
leg.
Material. Holotype only.
Locality and horizon. Shestakovo-1 locality (5554.6N,
8756.9E), Tchebulinski District, Kemerovskaya Oblast,
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112 E. N. Kurochkin et al.
Figure 2. Mystiornis cyrili gen. et sp. nov., holotype, PM TSU
No. 16/5-45; left metatarsus; Kemerovskaya Oblast, Shestakovo-
1 locality; Lower Cretaceous, Barremian-Aptian, Ilekskaya Svita.
A, dorsal view; B, lateral view; C, plantar view; D, medial view; E,
distal view; F, proximal view. Abbreviations: cc, cotyla centrale;
cid, canalis interosseus distalis; cl, cotyla laterale; cm, cotyla medi-
ale; cmIII, crista metatarsi III; ddtIII, depressio dorsalis trochlea
III; dptII, depressio plantaris trochlea II; emII, eminentia metatarsi
II; fmI, fossa metatarsi I; fvd, foramen vasculare distale; fvp, fora-
men vasculare proximale; tII, trochlea metatarsi II; tIII, trochlea
metatarsi III; tIV, trochlea metatarsi IV.
Russia; Lower Cretaceous, Barremian-Aptian, Ilekskaya
Svita.
Measurements. Length of metatarsus 26.4 mm; length of
metatarsal II 21.4 mm, length of metatarsal III 26.1 mm;
length of metatarsal IV 25.8 mm; maximal mediolateral
width of proximal end 3.6 mm; depth of medial cotyle
2.0 mm, mediolateral width of metatarsus at the level of
fossa metatarsi I 2.0 mm; maximal depth of metatarsus
in the middle 1.3 mm; mediolateral width of tr. metatarsi
II 1.9 mm; depth of tr. metatarsi II 1.2 mm; mediolateral
width tr. metatarsi III 1.6 mm dorsoplantar diameter of tr.
metatarsi III 1.9 mm, depth of tr. metatarsi IV 1.5 mm.
Description and comparisons. The holotype is repre-
sented by a graceful, elongated and practically complete
metatarsus with well preserved metatarsals II, III and IV,
as well as proximal cotylae and distal trochleae. Slightly
destroyed are the surfaces of the dorsolateral angle of the
proximal articular surface of metatarsal II, lateroplantar
side of the proximal end of metatarsal IV, the lateral side
of metatarsal III at the level of the proximal foramen,
and the top point of a tuberculum on the medioplantar
angle of trochlea II. Metatarsal V and signs of its artic-
ulation are missing. The metatarsals are tightly co-ossified
with each other practically throughout their entire lengths,
except for the most proximal ends of metatarsals III and IV,
visible in proximal and dorsal views. A similar condition,
partial non-fusion of the shafts, is known in the ornithurine
Liaoningornis and in enantiornithine avisaurids (Chiappe
1993; Hou 1997). Besides the lack of fusion of the prox-
imal metatarsals III and IV, there is a narrow oval crack
between metatarsals III and IV in the proximal quarter
of their shafts. This crack is most likely to be of natu-
ral origin (proximal vascular foramen?), although it might
be the result of postmortal destruction of the thin edges
of the metatarsals. The distal tarsals and a cap covering
the metatarsus are clearly absent. All three metatarsals lie
in coplanar (transversal) plane. The proximal surfaces of
metatarsals II–IV have concave separated articular facets:
medial, largest central and smallest lateral cotylae, accord-
ingly. There is a small longitudinal prominence between
the medial and central cotylae that confirms their separa-
tion. An elevation (eminentia metatarsi II) on the plantar
part of the medial cotyle protrudes proximally beyond the
surfaces of the central and lateral cotylae. The hypotarsus
is not developed. The dorsal surfaces of the metatarsals
are tapered in the form of longitudinal crests, especially
distinctive on metatarsals III and IV. Therefore, the shaft of
the metatarsus looks three-crested in dorsal view. The crest
of metatarsal III is the highest, while that of metatarsal II
is the least pronounced. The most proximal area of crista
metatarsi III abruptly extends on the dorsal edge of the
central cotyle.
In lateral aspect, the middle portion of the metatarsus is
slightly curved plantad, the whole proximal end is slightly
inclined dorsally, and the entire distal part with trochleae
is noticeably deflected plantad. Metatarsal II is the shortest
and completely co-ossified with metatarsal III throughout
its entire length. The shaft of metatarsal II is mediolater-
ally flattened; its plantar surface forms a ridge (crista plan-
taris medialis) which circumscribes a deep plantar concav-
ity (sulcus flexorius), as is present in a number of taxa of
Enantiornithes. In lateral view, this ridge noticeably projects
plantad beyond the plantar edge of metatarsal IV. There is
a small but conspicuous tubercle (tuberculum metatarsi II)
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A new taxon of birds from the Early Cretaceous 113
with a roughness (possibly a place for the attachment of
the tendon for m. tibialis cranialis) on the dorsal surface
of metatarsal II on the proximal fifth of its length. This
character is considered a synapomorphy of Enantiornithes
(Chiappe & Witmer 2002).
The distal portion of the shaft of metatarsal II, before
its transition into the trochlea, is flattened dorsoplantarly
and extends considerably lateromediad. Metatarsal II ends
much more proximally than metatarsals III and IV. Fossa
metatarsi I faces medioplantad, is positioned on the shaft
of metatarsal II, and closely approaches the correspond-
ing trochlea. Such an orientation of this fossa indicates a
completely reversed position of the hallux and thus the pres-
ence of an anisodactyl foot. The shaft of metatarsal III is
flattened dorsoplantarly and is approximately twice as wide
as the shafts of metatarsals II and IV; it has a constant
width almost throughout its entire length. The shaft of
metatarsal IV is flattened lateromedially and is the narrow-
est of the three, as in Enantiornithes. There is a narrow
extensor groove running alongside the dorsal surface of
the bone between the distal third of metatarsals III and
IV. A small entry foramen of a canal (?canalis interosseus
distalis) lies within an excavation in the distal end of this
groove. This canal opens on the proximal wall of a rather
large distal vascular foramen. The latter has an oval shape
and is circumscribed distally by a bony bridge between
metatarsals III and IV; this bridge is not perforated by any
foramen. The plantar outlet of the distal vascular foramen
is wide; a low tubercle, circumscribing a shallow groove
(possibly for the tendon of m. extensor brevis dig. IV)on
the bony bridge, is present on the lateral edge of the base
of metatarsal III.
The plantar surface of the metatarsus is trough-shaped
(sulcus flexorius), with a wide flat floor formed by
metatarsal III, and the lateral and medial sides of the sulcus
circumscribed by the keeled plantar edges of metatarsals II
and IV, as in representatives of Strigidae and Accipitridae
as well as numerous enantiornithines and other Mesozoic
birds. The sulcus continues distally practically to the base
of metatarsal II, but in its distal part is bounded just by a
narrow plantar edge of metatarsal IV.
The sagittal planes of the metatarsal trochleae meet the
sagittal plane of the metatarsus at different angles. The
sagittal plane of trochlea II is inclined with an angle of about
15with respect to the sagittal plane of metatarsus. Trochlea
metatarsi II is very strongly flattened dorsoplantarly; its
distal edge does not reach the level of the distal vascular
foramen. This trochlea is the largest of the three and is
dorsoplantarly compressed, as in Enantiornithes (Chiappe
& Witmer 2002). On the dorsal and plantar surfaces of
the base of trochlea metatarsi II are shallow dorsal and
plantar depressions. The lateral condyle of trochlea II is
slightly larger than the medial one, and a ginglymoid notch
between them is almost not developed. The medial margin
of trochlea II appears to be flattened, with a low rugosity at
the probable point of origin of the collateral ligament. On
the lateral margin of this trochlea there is a rather deep pit
which probably marked the place of origin of another collat-
eral ligament. A small plantarly directed pointed tubercle is
also developed on the medioplantar angle of this trochlea.
Trochlea metatarsi II is positioned very close to the shaft of
metatarsal III, from which it is separated only by a narrow
fissure on the dorsal side; on the plantar side they are
completely fused to each other. Trochlea metatarsi III is
inclined at an angle about 5to the longitudinal axis of
the metatarsus; it is the longest of the three trochleae. This
trochlea is practically rounded in lateral and medial views.
Its medial condyle is somewhat larger than the lateral one.
The lateral and medial surfaces of the trochlea have deep
pits for collateral ligaments. There is a conspicuous depres-
sion (depressio dorsalis trochlea III) on the dorsal side of
the base of the trochlea. Distally this continues into a small
ginglymoid notch between condyles which have a quite
similar depth. Trochlea metatarsus IV is the smallest of the
three and is slightly abducted. It is rounded, the condyles
and intercondyle notch are almost not developed, and its
plantar margin is pointed and shifted somewhat laterally.
Small pits are present on the medial and lateral surfaces, at
possible places of origin of collateral ligaments. The sagit-
tal plane of this trochlea is inclined to the sagittal plane of
the metatarsus at an angle of about 10.
Cladistic analysis
Since the mosaic pattern of characters of Mystiornis
prevents unambiguous placement of this fossil within any
known higher taxa of Aves using the comparative morphol-
ogy approach, we performed a cladistic analysis to resolve
its phylogenetic position. For this purpose we used one of
the most recent and complete matrices for Mesozoic birds,
that of O’Connor et al. (2009). Along with Mystiornis we
coded several other Mesozoic taxa, such as the avialans
Vorona and Avisaurus archibaldi, as well as the troodontids
Mei and Anchiornis. Allosaurus was used as an outgroup.
The modified matrix includes 242 characters across 35 taxa
(see Online Supplementary Material for coding of the newly
included taxa). PAUP 4.0 (Swofford 2002), WinClade, and
TNT (Goloboff et al. 2008) were used to analyse the matrix.
The strict consensus of 576 MPTs, each 626 steps in
length (CI: 0.49; RI: 0.69), that resulted from the analysis
with PAUP is shown in Fig. 3. On this tree, Mystiornis is
optimized as the sister taxon of Avisaurus, and both are
included in Clade A that also includes Mei and Vorona.
This clade is basal with respect to all other Avialae apart
from Archaeopteryx. In contrast to PAUP, the strict consen-
sus tree resulting from a traditional search in TNT does not
support Clade A. In this tree, the phylogenetic position of
most of the basal avian taxa, except Longipterygiformes,
Ornithuromorpha and clades herein, were unresolved.
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114 E. N. Kurochkin et al.
Figure 3. Strict consensus tree recovered from analysis of data matrix modified after O’Connor et al. (2009) using PAUP (tree drawn
using WinClade). Clade A (see text) is indicated.
Heuristic search with WinClade yielded both of the afore-
mentioned topologies with few variations (Fig. 4).
The clade Mystiornis +Avisaurus is supported by the
apomorphic condition of the following characters: 236
(trochlea metatarsi II broader than trochlea metatarsi III,
as also found in the Enantiornithes excluding Concor-
nis and Longipterygiformes); 230 (distal vascular fora-
men completely enclosed, as in Ornithuromorpha); and
221 (metatarsals at least nearly completely fused, as
in Ornithuromorpha and Eoalulavis). Nevertheless, the
general shape of the metatarsus in Mystiornis and
Avisauridae is different (the former has completely fused
gracile metatarsals), so we propose a new family for
Mystiornis.
There are no unique synapomorphies for Clade A,
although it is supported by the advanced conditions of char-
acters 229 (excavated plantar surface of metatarsus, also
present in Confuciusornis,Patagopteryx and Nequenor-
nis) and 233 (developed fossa metatarsi I, as in advanced
Ornithurae). In our opinion, both of these characters do not
justify establishing a new taxon since they are present in a
variety of fossil Avialae. The putative troodontid Mei is also
included in Clade A. Troodontidae are similar to Mystiornis
in that metatarsal II is markedly shorter than metatarsals III
and IV (Makovicky & Norell 2004). However, all troodon-
tids have unfused metatarsals (firmly fused in Mystiornis);
furthermore, in all taxa except the basal Sinovenator (Xu
et al. 2002) and Anchiornis (Hu et al. 2009) the third
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A new taxon of birds from the Early Cretaceous 115
Figure 4. Strict consensus tree recovered with a heuristic search in TNT (tree drawn with WinClade).
metatarsal is strongly constricted for most of its length,
being excluded from the plantar view (Makovicky & Norell
2004). Thus the morphology of the metatarsus is consid-
erably different in advanced Troodontidae and Mystiornis,
but the most basal troodontid taxa show some similarities
to the new taxon. In this case the PAUP cladogram may be
accepted as a working hypothesis, pending more data on
Mystiornis. The systematic position of Mystiornis is thus
presently considered as Avialae incertae sedis.
Conclusion
Mystiornis cyrili gen. et sp. nov. represents a small bird
the size of a thrush, with probable adaptation to underwa-
ter swimming reflected in the characteristic shortening of
metatarsal II and widening of the corresponding trochlea,
similar to Gansus. However, the mosaic of characters does
not permit assignment to any known major taxon of Avialae,
either via evolutionary morphology or by cladistic analy-
sis. Mystiornis differs from all known taxa of feathered
vertebrates in the presence of separated concave articu-
lation facets on the proximal extremities of metatarsals
II–IV and localization of a distal interosseal canal in the
proximal part of the distal vascular foramen. Mystiornis
differs from Confuciusornithes and Dromeosauridae in the
morphology of the distal extremity of the metatarsus, i.e.
complete coalescence of distal metatarsals and the pres-
ence of a distal vascular foramen. However, Mystiornis
resembles these taxa in the coplanar arrangement of the
proximal ends of the metatarsals. The new taxon shares
with Enantiornithes the wide trochlea of metatarsal II and
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116 E. N. Kurochkin et al.
the presence of a tuberculum on the dorsal surface in the
proximal part of metatarsal II. It differs from this taxon,
however, in the degree of fusion of the metatarsals and the
overall consolidation of metatarsus. It differs from Ornithu-
rae in the morphology of the proximal extremity, i.e. the
coplanar arrangement of proximal metatarsals, absence of
the hypotarsus and dorsal intercotylar fossa, and separa-
tion of the most proximal extremities of metatarsals III
and IV. However, it resembles Ornithurae in having almost
complete fusion of the metatarsals and in its fully developed
distal vascular foramen.
Cladistic analysis using PAUP places Mystiornis within
a clade which also includes Mei,Vorona and Avisaurus,
and occupies a basal position relative to all other Avialae
except for Archaeopteryx. MacClade and TNT leave the
phylogenetic position of Mystiornis unresolved within
basal Avialae. Lack of resolution and collapse of well-
documented relationships may reflect the incompleteness
of taxa such as the new species, and Vorona,aswellas
the mosaic distribution of avian characters within closely
related maniraptorans such as Mei and Anchiornis.
The discovery of Mystiornis shows that in the Creta-
ceous, swimming adaptations were achieved not only by
Ornithurae (such as Gansus, Hesperornithiformes, Ichthy-
ornis), but independently by other groups of birds. This
testifies to the variety of morphologies seen in the early
evolution of birds, and to the parallel evolution of different
groups of feathered vertebrates.
Acknowledgements
The authors thank Zhou Zhonghe, Xu Xing and Corwin
Sullivan for data on Cretaceous birds and dinosaurs from
China, Evgenia Baikina for help in making the map, Jing-
mai O’Connor for useful comments and correction of the
English, and Gareth Dyke for correction of the English
and for the invitation to submit our paper to the meeting
and volume dedicated to the memory of Cyril Walker. This
research was supported by Grant No. 10-04-00575 of the
Russian Fund for Basic Research.
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... In order to test existing hypotheses regarding the phylogenetic affinity of potential avisaurid taxa, we created the first data matrix to include all such taxa: the Kaiparowits specimen, A. archibaldi, "A. gloriae," Soroavisaurus, Neuquenornis, Intiornis, Bauxitornis, Concornis, Mystiornis, Halimornis, Gobipteryx, and Enantiophoenix (Elzanowski, 1974;Brett-Surman & Paul, 1985;Sanz & Buscalioni, 1992;Chiappe, 1993;Chiappe & Calvo, 1994;Varricchio & Chiappe, 1995;Chiappe, Lamb & Ericson, 2002;Cau & Arduini, 2008;Dyke & Ősi, 2010;Novas, Agnolín & Scanferla, 2010;Kurochkin et al., 2011;O'Connor et al., 2009). The new analysis is based on the O' Connor & Zhou (2013) matrix, modified to include an additional state in character 233 and seven additional tarsometatarsal characters mostly derived from previous avisaurid analyses (see Supplemental Information) (Chiappe, 1993;O'Connor, 2009;O'Connor, Averianov & Zelenkov, 2014). ...
... More recently, Intiornis and Bauxitornis, both represented by tarsometatarsi, were also referred to the Avisauridae, but these assignments were not supported through cladistic analysis (Dyke & Ősi, 2010;Novas, Agnolín & Scanferla, 2010). Mystiornis, known only from an isolated tarsometatarsus, preserves some avisaurid-like features (such as a dorsally convex metatarsal III) and has been resolved in a clade with Avisaurus outside the Enantiornithes ( Kurochkin et al., 2011). However, this specimen was not referred to the Avisauridae because of the metatarsals are fully co-ossified, a feature not present in any known enantiornithine (Kurochkin et al., 2011). ...
... Mystiornis, known only from an isolated tarsometatarsus, preserves some avisaurid-like features (such as a dorsally convex metatarsal III) and has been resolved in a clade with Avisaurus outside the Enantiornithes ( Kurochkin et al., 2011). However, this specimen was not referred to the Avisauridae because of the metatarsals are fully co-ossified, a feature not present in any known enantiornithine (Kurochkin et al., 2011). Fusion is heavily affected by ontogeny, and we suggest that this conclusion is not strongly justified, especially in light of the variable amount of fusion apparent in the tarsometatarsus of other avisaurids. ...
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A sample of 136 isolated theropod teeth from nine vertebrate localities within the Lower Cretaceous (Barremian-Aptian) Ilek Formation in West Siberia, Russia, can be separated into five dental morphotypes referred to five or six theropod taxa based on morphological characters. The Morphotype A includes small to large lateral teeth with relatively large distal denticles and smaller mesial denticles. Some of these teeth can be attributed to the Dromaeosauridae, while other teeth may belong to a basal member of the Tyrannosauroidea. The distinctly smaller lateral teeth referred to the Morphotype B are similar with Morphotype A in most respects but differ in the lack of mesial denticles and mesial carina, or having a lingually displaced mesial carina. These teeth may belong to juvenile individuals of the same dromaeosaurid taxon. The teeth belonging to Morphotype C also lack mesial denticles and differ from Morphotype B by a flattened area on the lingual side, which is also often present on the labial side. These teeth may belong to either Troodontidae or Microraptorinae, or to both groups. The mesial and lateral teeth of Morphotype E are characterized by unserrated mesial and distal carinae. These teeth most likely belong to a distinct taxon of Troodontidae with unserrated dentition. The teeth of the Morphotype D include mesial teeth with the mesial carina displaced lingually at various extent and denticles present on both carinae. The teeth with moderately displaced lingual carina can be referred to the same dromaeosaurid taxon, which lateral teeth represented by Morphotype A. The teeth with more displaced mesial carina and deeply U-shaped basal crown section belong to an indeterminate Tyrannosauroidea.
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A new data on the geological structure, conditions of formation and faunal composition of the Early Cretaceous site of the terrestrial vertebrates by Shestakovo village (Kemerovo Region, Western Siberia) has been presented. The consolidated geological section has been constructed along the line Shestakovo-1—Shestakovo-4—Shestakovo-3 in which five lithologic members have been identified. A distribution of the vertebrates fauna taxons has been carried out along these lected lithologic members composing the Shestakovo series of the Ilek formation. A new data obtained during fieldwork in 2017 has made it possible to distinguish two main bony levels (lithologic members 3 and 5), which contain whole skeletons of reptiles. Lithofacies analysis has shown that the formation of the sites occurred under the conditions of the fluviolacustrine plain, where the channel, delta and floodplain facies were replaced by lake and lake-marshy facies, forming a series of sedimentation cycles. The latter are the evidence of the increase in the aridization of the climate upwards along the section. The given data calls into question previously expressed point of view about the coastal-marine or lagoon genesis of the Shestakovo series. Keywords: biostratigraphy; lithofacies analysis; sedimentation; Lower Cretaceous; Ilek formation; Kemerovo Region.
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Troodontidae is a clade of small, lightly built maniraptorans known from Cretaceous deposits of Asia and North America. These theropods have serrated teeth, raptorial hands, and an enlarged sickle-shaped claw on the foot. This chapter discusses the taxonomy and diagnostic features of troodontids. It also discusses phylogenetic hypotheses of troodontid relationships. Diagnostic remains of troodontids are largely restricted to Central Asia and China, and the origin and most of the evolutionary history of the clade was endemic to that continent. Only a single derived troodontid taxon, Troodon formosus, occurs in North America.
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This revised edition of this book continues in the same vein as the first but encompasses recent spectacular discoveries that have continued to revolutionize this field. A thorough scientific view of current world research, the volume includes comprehensive coverage of dinosaur systematics, reproduction, and life history strategies, biogeography, taphonomy, paleoecology, thermoregulation, and extinction. It contains definitive descriptions and illustrations of these magnificent Mesozoic beasts. The first section of the book begins with the origin of the great clade of these fascinating reptile ... More This revised edition of this book continues in the same vein as the first but encompasses recent spectacular discoveries that have continued to revolutionize this field. A thorough scientific view of current world research, the volume includes comprehensive coverage of dinosaur systematics, reproduction, and life history strategies, biogeography, taphonomy, paleoecology, thermoregulation, and extinction. It contains definitive descriptions and illustrations of these magnificent Mesozoic beasts. The first section of the book begins with the origin of the great clade of these fascinating reptiles, followed by separate coverage of each major dinosaur taxon, including the Mesozoic radiation of birds. The second part of the volume navigates through broad areas of interest. Here we find comprehensive documentation of dinosaur distribution through time and space, discussion of the interface between geology and biology, and the paleoecological inferences that can be made through this link. This revised edition of this book continues in the same vein as the first but encompasses recent spectacular discoveries that have continued to revolutionize this field. A thorough scientific view of current world research, the volume includes comprehensive coverage of dinosaur systematics, reproduction, and life history strategies, biogeography, taphonomy, paleoecology, thermoregulation, and extinction. It contains definitive descriptions and illustrations of these magnificent Mesozoic beasts. The first section of the book begins with the origin of the great clade of these fascinating reptile ... More
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— We studied sequence variation in 16S rDNA in 204 individuals from 37 populations of the land snail Candidula unifasciata (Poiret 1801) across the core species range in France, Switzerland, and Germany. Phylogeographic, nested clade, and coalescence analyses were used to elucidate the species evolutionary history. The study revealed the presence of two major evolutionary lineages that evolved in separate refuges in southeast France as result of previous fragmentation during the Pleistocene. Applying a recent extension of the nested clade analysis (Templeton 2001), we inferred that range expansions along river valleys in independent corridors to the north led eventually to a secondary contact zone of the major clades around the Geneva Basin. There is evidence supporting the idea that the formation of the secondary contact zone and the colonization of Germany might be postglacial events. The phylogeographic history inferred for C. unifasciata differs from general biogeographic patterns of postglacial colonization previously identified for other taxa, and it might represent a common model for species with restricted dispersal.