ArticlePDF Available

Abstract and Figures

The fossil record of Late Cretaceous–Paleogene modern birds in the Southern Hemisphere includes the Maastrichtian Neogaeornis wetzeli from Chile, Polarornis gregorii and Vegavis iaai from Antarctica, and Australornis lovei from the Paleogene of New Zealand. The recent finding of a new and nearly complete Vegavis skeleton constitutes the most informative source for anatomical comparisons among Australornis, Polarornis, and Vegavis. The present contribution includes, for the first time, Vegavis, Polarornis, and Australornis in a comprehensive phylogenetic analysis. This analysis resulted in the recognition of these taxa as a clade of basal Anseriformes that we call Vegaviidae. Vegaviids share a combination of characters related to diving adaptations, including compact and thickened cortex of hindlimb bones, femur with anteroposteriorly compressed and bowed shaft, deep and wide popliteal fossa delimited by a medial ridge, tibiotarsus showing notably proximally expanded cnemial crests, expanded fibular crest, anteroposterior compression of the tibial shaft, and a tarsometatarsus with a strong transverse compression of the shaft. Isolated bones coming from the Cretaceous and Paleogene of South America, Antarctica, and New Zealand are also referred to here to Vegaviidae and support the view that these basal anseriforms were abundant and diverse at high southern latitudes. Moreover, vegaviids represent the first avian lineage to have definitely crossed the K–Pg boundary, supporting the idea that some avian clades were not affected by the end Mesozoic mass extinction event, countering previous interpretations. Recognition of Vegaviidae indicates that modern birds were diversified in southern continents by the Cretaceous and reinforces the hypothesis indicating the important role of Gondwana for the evolutionary history of Anseriformes and Neornithes as a whole.
a, b Proximal end of right humerus of Vegavis iaai in a medial and b lateral views. c, dAustralornis isoni; eVegavis iaai left coracoid in dorsal view; fVegavis iaai right ulnare in proximal view; g–i right femur of Vegavis iaai in g anterior, h medial, and i posterior views; j, k proximal left tibiotarsus of Vegavis iaai in j lateral and k anterior views; lVegavis iaai right hand in dorsal view; m–o left femur of Polarornis gregorii in m anterior, n medial, and o posterior views; p, q proximal left tibiotarsus of Polarornis gregorii in p lateral and q anterior views; r left scapula of Vegavis iaai in medial view; s rostrum of Polarornis gregorii in left lateral view; t articular portion of the left mandible of Vegavis iaai in lateral view; u left pterygoid of Vegavis iaai in ventral view. Abbreviations: al, alular digit; bptf, basipterygoid articular surface; cas, facies articularis clavicularis; cbc, crista bicipitalis; ccc, cranial cnemial crest; csr, capital ridge; dpc, deltopectoral crest; ep, extensor process; fib, fibula; fns, foramen nervi supracoracoidei; fo, pneumotricipital fossa; gl, glenoid; ig, intercondylar groove; isc, impressio M. sternocoracoidei; lc, lateral crest; lcc, lateral cnemial crest; lr, transverse linear ridge; mc, medial condyle; proc., procoracoidal process; pvf, proximoventral fossa; rad, radiale; rp, retroarticular process; rs, raised scar; shc, scar for M. scapulohumeralis cranialis; tbd, dorsal tubercle; tbv, ventral tubercle; tfc, tibiofibular crest; ul, ulnare. (c) and (d) modified from Mayr and Scofield (2014). Scale bar equals 1 cm for (a), (b), (c), (d), (g), (h), (i), (j), (k), (l), (m), (n), (o), (r), (s), (t), and (u) and 0.5 cm for (f), (p), and (q)
… 
This content is subject to copyright. Terms and conditions apply.
ORIGINAL PAPER
Vegaviidae, a new clade of southern diving birds
that survived the K/T boundary
Federico L. Agnolín
1,2
&Federico Brissón Egli
1,3
&Sankar Chatterjee
4
&
Jordi Alexis Garcia Marsà
1,3
&Fernando E. Novas
1,3
Received: 13 July 2017 /Revised: 21 September 2017 /Accepted: 22 September 2017
#Springer-Verlag GmbH Germany 2017
Abstract The fossil record of Late CretaceousPaleogene
modern birds in the Southern Hemisphere includes the
Maastrichtian Neogaeornis wetzeli from Chile, Polarornis
gregorii and Ve ga v i s i a a i from Antarctica, and Australornis
lovei from the Paleogene of New Zealand. The recent finding
of a new and nearly complete Ve g a vi s skeleton constitutes the
most informative source for anatomical comparisons among
Australornis,Polarornis,andVegavis. The present contribu-
tion includes, for the first time, Ve g avis,Polarornis,and
Australornis in a comprehensive phylogenetic analysis. This
analysis resulted in the recognition of these taxa as a clade of
basal Anseriformes that we call Vegaviidae. Vegaviids share a
combination of characters related to diving adaptations, in-
cluding compact and thickened cortex of hindlimb bones, fe-
mur with anteroposteriorly compressed and bowed shaft, deep
and wide popliteal fossa delimited by a medial ridge,
tibiotarsus showing notably proximally expanded cnemial
crests, expanded fibular crest, anteroposterior compression
of the tibial shaft, and a tarsometatarsus with a strong trans-
verse compression of the shaft. Isolated bones coming from
the Cretaceous and Paleogene of South America, Antarctica,
and New Zealand are also referred to here to Vegaviidae and
support the view that these basal anseriforms were abundant
and diverse at high southern latitudes. Moreover, vegaviids
represent the first avian lineage to have definitely crossed
the KPg boundary, supporting the idea that some avian
clades were not affected by the end Mesozoic mass extinction
event, countering previous interpretations. Recognition of
Vegaviidae indicates that modern birds were diversified in
southern continents by the Cretaceous and reinforces the hy-
pothesis indicating the important role of Gondwana for the
evolutionary history of Anseriformes and Neornithes as a
whole.
Keywords Vegavis .Vegaviidae .Gondwana .Neornithes
Introduction
The fossil record of Late CretaceousPaleogene modern birds
in the Southern Hemisphere is patchy and highly fragmentary
(Chiappe 2016). It includes Neogaeornis wetzeli from
Maastrichtian beds of Chile, Polarornis gregorii and Vegavis
iaai from the Maastrichtian of Antarctica, and Australornis
lovei from the Paleogene of New Zealand (Chatterjee 2002;
Clarke et al. 2005,2016;Mayr2009; Mayr and Scofield 2014).
The phylogenetic relationships of these taxa as well as various
isolated specimens from Paleogene and Cretaceous of
Antarctica have been variously interpreted by different authors
(e.g., Olson 1992; Chiappe 1996; Chatterjee 2002; Clarke et al.
2005; Acosta Hospitaleche and Gelfo 2015). The best support-
ed taxonomic referral is that of Ve g a vi s , represented by two
Communicated by: Sven Thatje
Electronic supplementary material The online version of this article
(https://doi.org/10.1007/s00114-017-1508-y) contains supplementary
material, which is available to authorized users.
*Federico L. Agnolín
fedeagnolin@yahoo.com.ar
1
Laboratorio de Anatomía Comparada y Evolución de los
Vertebrados, Museo Argentino de Ciencias Naturales BBernardino
Rivadavia^, Av. Ángel Gallardo 470, C1405DJR Buenos
Aires, Argentina
2
Fundación de Historia Natural BFélix de Azara^,Universidad
Maimónides, Hidalgo 775, C1405BDB Buenos Aires, Argentina
3
CONICET, Buenos Aires, Argentina
4
Museum of Texas Tech University, Box 43191, Lubbock, TX 79409,
USA
Sci Nat (2017) 104:87
DOI 10.1007/s00114-017-1508-y
partially articulated skeletons that exhibit several features in
common with living anseriforms (Clarke et al. 2005,2016).
Mayr and Scofield (2014) compared Australornis with
Vegavis, indicating shared anatomical details of the humerus.
A recently published (Clarke et al. 2016;ESM)Vegavis skel-
eton [MACN-PV (Vertebrate Paleontology Collection, Museo
Argentino de Ciencias Naturales Bernardino Rivadavia,
Buenos Aires, Argentina) 19.748] constitutes the most informa-
tive source for anatomical comparisons among Australornis,
Polarornis,Veg a v i s as well as other southern avian specimens.
In the present contribution, we offer evidence that these Late
Cretaceous and Paleogene birds are closely related constituting
a new clade of basal anseriforms. Isolated bones from
Cretaceous and Paleogene beds of South America, Antarctica,
and New Zealand may be also referable to this new clade of
anseriforms. Moreover, it represents the first avian lineage to
have definitely crossed the KPg boundary, supporting that
some avian clades were not affected by the end Mesozoic mass
extinction event, countering previous interpretations.
Results
Comparative study of Vegavis,Polarornis,
and Australornis
Vegavis is represented by two articulated partial skeletons
(Clarke et al. 2005,2016). It overlaps with Australornis
(Mayr and Scofield 2014) in the proximal portion of the hu-
merus, proximal part of the coracoid, scapula, and ulna.
Besides, the new specimen of Ve ga v i s overlaps with that of
Polarornis [Chatterjee 2002;TTUP(TexasTechUniversity,
Lubbock, USA) 9265] in the humerus, femur, and proximal
end of the tibia, and with Neogaeornis in the tarsometatarsus.
This set of taxa allows comparison with fragmentary
Paleogene Antarctic and New Zealand specimens represented
by isolated coracoid, femur, tibiotarsus, and tarsometatarsus
(e.g., Case and Tambussi 1999;Caseetal.2006;Acosta
Hospitaleche and Gelfo 2015).
The humerus is probably the most diagnostic element
among anseriforms (Woolfenden 1961). This bone shows a
large number of features that are shared between Vegavis
and Australornis (Fig. 1). In the latter two taxa, the humerus
is notably narrow and medially tilted on its proximal half. It
shows an unusually proximodistally elongate deltopectoral
crest that quadruplicates the length of the bicipital crest. In
the case of Vegavis and Australornis, the deltopectoral crest
extends for more than one third of the humeral length. The
dorsal tubercle is notably robust and proximally projected, as
in presbyornithids (De Pietri et al. 2016). Both features were
previously considered autapomorphic for Australornis by
Mayr and Scofield (2014), but their presence in Veg a v i s indi-
cates that both are diagnostic of a clade including these two
taxa. The capital ridge is strongly marked, and the ventral
pneumotricipital fossa is wide, deep, and non-pneumatic.
The dorsal pneumotricipital fossa is relatively wide, well de-
fined, and subcircular in outline. The ventral tubercle is nota-
bly expanded and proximally projected.
Vegavis ,Australornis, and presbyornithids share a well-
marked and elongate scar for insertion of M. scapulohumeralis
and M. latissimus dorsi caudalis (De Pietri et al. 2016). The
coracobrachialis impression is notably deep and well defined,
and the transverse ligament groove is notably undercut and
proximally extended.
The coracoid of Ve g a v i s is well known, but it is incomplete-
ly preserved in Australornis. However, both taxa share a hu-
merus with an expanded articular surface for the furcula (a
feature recovered diagnostic for Anseriformes in recent
analyses; Clarke et al. 2016), and the main plane for the artic-
ular humeral facet is laterally oriented, thus meeting the ven-
tral surface of the humerus at an angle close to 90° (a feature
originally considered autapomorphic for Australornis by
Mayr and Scofield 2014). As in other anseriforms, Vegavis
exhibits the sternocoracoid impression with transverse linear
ridges (De Pietri et al. 2016). In Vega v i s , the sternal end of the
coracoid is transversely expanded, being subequal to total
coracoidal length. The scapula is narrow and elongate with
subparallel margins in both Veg a v i s and Australornis.
The femur is well known both in Ve g a vi s and Polarornis
(Fig. 1). They share a combination of characters absent in
other Mesozoic or Paleogene birds, including strongly anteri-
orly bowed and anteroposteriorly compressed shaft (especial-
ly near its distal end). This last condition of the distal part of
the femur produces an ovoid-shape cross-section, a popliteal
fossa wide and deep, an intercondylar distal groove wide and
shallow, a medial distal condyle smaller than the lateral one, a
trochlea fibularis wide and strongly laterally projected, and a
medial supracondylar crest proximodistally extended.
The tibiotarsi of Vegavis and Polarornis share a pair of
proximally expanded cnemial crests (Fig. 1). The cranial
cnemial crest is proximally and anteriorly expanded and ex-
tends distally down the tibiotarsal shaft. The lateral cnemial
crest is thickened in both Vega v i s and Polarornis (this feature
was originally considered autapomorphic for Polarornis by
Chatterjee 2002). It flares distally and is separated from the
cranial cnemial crest by a deepintercnemial groove. A patellar
crest is absent. In both taxa, the fibular crest is located far from
the proximal end of the bone, and the shaft is strongly
anteroposteriorly flattened.
The tarsometatarsus is only incompletely known in Vegavis,
and the nearly complete tarsometatarsus of Neogaeornis is
known. The shaft is notably transversely compressed with sharp
lateral and medial edges. In Vegav i s , the intercotylar prominence
is low and rounded, and the hypotarsus shows four small ridges
of which the medial one is larger and more distally extended
than the remaining crests. The distal end of the bone resembles
87 Page 2 of 9 Sci Nat (2017) 104:87
Fig. 1 a,bProximal end of right humerus of Vegavis iaai in amedial and b
lateral views. c,dAustralornis isoni;eVega v i s iaa i left coracoid in dorsal
view; fVegavis iaai rightulnareinproximalview;giright femur of Vegavis
iaai in ganterior, hmedial, and iposterior views; j,kproximal left
tibiotarsus of Vegavis iaai in jlateral and kanterior views; lVegavis iaai
right hand in dorsal view; moleft femur of Polarornis gregorii in m
anterior, nmedial, and oposterior views; p,qproximal left tibiotarsus of
Polarornis gregorii in plateral and qanterior views; rleft scapula of Vegavis
iaai in medial view; srostrum of Polarornis gregorii in left lateral view; t
articular portion of the left mandible of Vegavis iaai in lateral view; uleft
pterygoid of Vegavis iaai in ventral view. Abbreviations: al, alular digit; bptf,
basipterygoid articular surface; cas, facies articularis clavicularis; cbc, crista
bicipitalis; ccc, cranial cnemial crest; csr, capital ridge; dpc, deltopectoral
crest; ep, extensor process; fib, fibula; fns, foramen nervi supracoracoidei;
fo, pneumotricipital fossa; gl, glenoid; ig, intercondylar groove; isc,
impressio M. sternocoracoidei; lc, lateral crest; lcc, lateral cnemial crest; lr,
transverse linear ridge; mc, medial condyle; proc., procoracoidal process;
pvf, proximoventral fossa; rad, radiale; rp, retroarticular process; rs, raised
scar; shc, scar for M. scapulohumeralis cranialis; tbd, dorsal tubercle; tbv,
ventral tubercle; tfc, tibiofibular crest; ul, ulnare. (c)and(d) modified from
Mayr and Scofield (2014). Scale bar equals 1 cm for (a), (b), (c), (d), (g), (h),
(i), (j), (k), (l), (m), (n), (o), (r), (s), (t), and (u) and 0.5 cm for (f), (p), and (q)
Sci Nat (2017) 104:87 Page 3 of 9 87
that of diving birds (e.g., gaviiforms, podicipediforms) and
anseriforms (Ericson 1997) in having a posteriorly tilted trochlea
of metatarsal II. Interestingly, the tarsometatarsus of
Neogaeornis exhibits two anseriform traits: presence of a deep
concavity above the center of the middle trochlea and
dorsomedial to the distal vascular foramen (Cenizo 2012), and
a distally located distal vascular foramen (Bourdon 2005). This
anatomical evidence allows recognizing Neogaeornis as an
anseriform, but also as related to Veg a v i s and its kin, dismissing
previous hypotheses proposing this taxon as a hesperornithiform
oragaviiform(seeOlson1992).
Increase of osteosclerosis in the femur has been reported
previously for Polarornis (Chinsamy et al. 1998;DeMendoza
and Tambussi 2015). The humerus and femur of Ve g a vi s also
exhibit a notably thickened cortex, composed of a highly
vascularized (semi-reticular pattern), woven-fibered matrix
that grades into an avascular matrix subperiosteally and end-
osteally (Fig. 2). Lines of arrested growth are absent. Cross-
sections of the shafts are characterized by osteosclerosis. The
relative bone thickness (RBT) (sensu Smith and Clarke 2014)
in the femur is ~ 21.6, a value that is closely similar to that of
the diving ducks Tachyeres and Ayth ya, while in the case of
the humerus the RBT is ~ 20, a value similar to that of
Tachyeres. Osteosclerosis of limb bones in Vegavis and
Polarornis may constitute an additional derived trait sustain-
ing the close phylogenetic relationship between these genera.
Phylogenetic relationships
A comprehensive phylogenetic analysis of Anseriformes is
here conducted including, for the first time, Vegavis,
Polarornis,andAustralornis (ESM). As a result, a monophy-
letic clade gathering these taxa emerges at the base of
Anseriformes. This new clade is here termed as Vegaviidae
nov., and it is sustained by 12 unambiguous synapomorphies
and is supported by strong statistical values (ESM; Fig. 3).
In agreement with previous interpretations (Noriega and
Tambussi 1995;Clarkeetal.2005), Vegavis is here recovered
as belonging to Anseriformes. The combination of skull and
postcranial characters exhibited by Polarornis sustains that it
belongs to Anseriformes, contrary to its original interpretation
as a member of Gaviidae (Chatterjee 2002). Veg a v i s shares with
Galloanseres a well-developed and transversely compressed
retroarticular process (Mayr and Clarke 2003), an extended fos-
sa for the attachment of M. adductor mandibulae externus
(Dzerzhinsky 1995), a pronounced coronoid inflection, and
mandibular cotylae anteroposteriorly elongate, separated by a
low longitudinal crest (Weber and Hesse 1995;Ericson1997;
Clarke et al. 2016;Fig.1). Furthermore, analysis of skull mate-
rial of Polarornis indicates that this taxon shares with
Galloanserae a lacrimal lacking contact with the jugal bar
(Mayr 2011) and a well-developed craniofacial flexor zone
marked by a transverse groove between nasals and frontal pro-
cess (Worthy et al. 2016). Clarke et al. (2016)reportedforthe
pterygoid of Vegavis a large and prominent, anteriorly located
and dorsoventrally facing basipterygoid articulation, a condition
diagnostic for Galloanserae (see also Cracraft and Clarke 2001).
Vegavis differs from Galliformes, but resembles Anseriformes,
in that the basipterygoid articular surface is not located at the
anterior margin of the bone (Olson and Feduccia 1980;Fig.1).
Furthermore, vegaviids share with Anseriformes a
carpometacarpus with processus pisiformis at the level of the
Fig. 2 Histological sections of
Ve g a vi s i a a i (MACN-PV 19.748)
humerus (a), femur (b), and
polarized detail of humerus (c).
Scale bar equals 10 mm for (a),
(b)and5mmfor(c)
87 Page 4 of 9 Sci Nat (2017) 104:87
carpal trochlea (Bourdon 2005), a deep fossa within the
supracoracoidal sulcus in the coracoid (Mayr 2008), well-
developed haemal arches in distal caudal vertebrae (as evi-
denced by the well-developed haemal facets on the ventral
surface of the vertebral centra; Mayr and Clarke 2003), a
prominent tubercle on the caudal end of the dorsal ramus of
the ulnare (Ericson 1997;Clarkeetal.2016), a tibiotarsus with
proximallyextended cranial cnemial crest, and a tarsometatar-
sus with four or more hypotarsal crests (Worthy et al. 2016).
The retention in Ve g a v i s of a well-developed foramen nervi
supracoracoidei in the body of the coracoid, a transversely
expanded sternal end of coracoid, and a small distal metacar-
pal symphysis constitute plesiomorphies present in vegaviids
that sustain them as stem-Anseriformes (Fig. 1).
Polarornis and Neogaeornis were considered as related to
modern loons (i.e., Gaviiformes; Olson 1992;Chiappe1996;
Cooper and Penny 1997; Padian and Chiappe 1998; Hope
2002; Chatterjee 2002; Van Tuinen and Hedges 2004;
Acosta Hospitaleche and Gelfo 2015). However, the
gaviiform affinities of these taxa have been questioned by
several authors (e.g., Mayr 2009; Mayr and Poschmann
2009; Smith 2010; Mayr et al. 2013; Feduccia 2014), and
Mayr et al. (2013) noted the strong morphological discrepancy
in morphology between putative Late Cretaceous gaviiform
taxa and those from the early Paleogene.In fact, most features
that were originally interpreted to include Polarornis and
Neogaeornis within Gaviiformes are mostly related to the
proportions and general morphology of the femur, proximal
tibiotarsus, and distal metatarsal trochleae (Fig. 1). As noted
above, all these traits are present in the anseriform Ve g a v i s ,
and most of them are recovered as synapomorphies of
Vegaviidae. These features of the hindlimb are related to div-
ing habits and were probably convergently acquired by loons
and vegaviids (see BDiscussion^section below).
In spite of the fact that Vegav i s and Polarornis appear
roughly contemporaneous in age, both come from the same
geographical region (NE Antarctic Peninsula), and few com-
parable bones share the same general morphology. Clarke
et al. (2016) indicated some anatomical differences between
both genera. Veg a v i s is slightly over approximately one half
the size of Polarornis (Clarke et al. 2016), and details in fem-
oral anatomy (see ESM) suggest they represent two separate,
albeit closely related, taxa.
In addition to Polarornis,Vegavis,Australornis,and
Neogaeornis, there are several additional specimens that
may belong to Vegaviidae. Mayr and Scofield (2014)de-
scribed from the Paleocene of New Zealand an incomplete
proximal humerus that was referred to Phaethontiformes.
However, this element shares with Veg a v i s and Australornis
a notably wide and deep dorsal pneumotricipital fossa that is
subcircular in outline (Mayr and Scofield 2015), a distally thin
shaft, and well-developed ventral and dorsal tubercles. On this
basis, we tentatively interpret this specimen as an
indeterminated vegaviid (ESM).
Case et al. (2006) and Acosta Hospitaleche and Gelfo
(2015) described two incomplete distal femora from the Late
Fig. 3 Phylogeny with
geographical distribution of
Vegaviidae (a) and fossiliferous
localities that yielded vegaviid
genera (b). Schematic skeletal
reconstruction of Vegavis iaai
based on specimens MLP 93-I-3-
1 and MACN-PV 19.748 (c).
Skull based on preserved remains
of Polarornis gregorii (Chatterjee
2002)
Sci Nat (2017) 104:87 Page 5 of 9 87
Cretaceous of Antarctica, referred by these authors to
Cariamiformes and Gaviiformes, respectively (ESM).
Further, Yury-Yáñez et al. (2012) described the distal end of
a femur of an indeterminate bird from the Eocene beds of
Southern Chile (ESM). These three femora show a combina-
tion of features shared with vegaviids, including anteriorly
bowed shaft, medial distal condyle smaller than the lateral
one, and trochlea fibularis transversely wide and laterally
projected.
Acosta Hospitaleche and Gelfo (2015) described an isolat-
ed coracoid from the Eocene of Antarctica as belonging to
Gaviiformes (Tambussi and Degrange 2013;Acosta
Hospitaleche and Gelfo 2015). However, this element shares
with Vegavis several features, suggestive of vegaviid affinities
of the specimen (ESM).
Acosta Hospitaleche and Gelfo (2015) described from the
Late Cretaceous and Paleogene of Antarctica isolated
tibiotarsi that they referred to Gaviiformes. Nevertheless,
these specimens share with Vegavis and Polarornis several
features that suggest their inclusion among vegaviids.
Isolated tarsometatarsi from the Late Cretaceous of
Antarctica (identified as Gaviiformes by Acosta Hospitaleche
and Gelfo 2015) and from the Paleogene of New Zealand
(Ksepka and Cracraft 2008) share a combination of features
reminiscent to Vegaviidae. These tarsometatarsi share with
Vegavis, and specially Neogaeornis a transversely compressed
shaft with sharp lateral and medial edges, asymmetrical distal
trochleae, and a deep concavity above the center of the middle
trochlea (ESM).
To sum up, we recognize Polarornis,Vegavis,Australornis,
and Neogaeornis as members of the new clade Vegaviidae, and
that a large number of isolated specimens collected from Late
Cretaceous and Paleogene beds of Antarctica, South America,
and New Zealand may also belong to this group of basal
anseriforms. Consequently, previous reports of Late
Cretaceous and Paleogene Gaviiformes, Charadriiformes,
Cariamiformes, Phaethontiformes, and Hesperornithiformes
(Hou in Feduccia 1999; Chatterjee 2002;Clarkeetal.2005;
Chatterjee et al. 2006; Cenizo 2012; Cordes 2002;Tambussi
and Degrange 2013; Reguero et al. 2013) from the Southern
Hemisphere are here dismissed, but interpreted as anseriforms
and possible members of Vegaviidae.
Systematic paleontology
Aves Linnaeus, 1758.
Neornithes Gadow, 1893.
Galloanserae Sibley, Ahlquist and Monroe, 1988.
Anseriformes Wagler, 1931.
Vegaviidae nov.
Diagnosis. Clade of birds having the following synapo-
morphies: Humerus with: 1very long deltopectoral crest
that represents more than four times the length of the bicipital
crest (Mayr and Scofield 2014; ch. 122-3); 2presence of a
dorsal pneumotricipital fossa that is shallow and relatively
wide, being smaller than the ventral pneumotricipital fossa
(ch. 118-1; 119-1); 3incisura capitis conforming a distinct
proximal notch (ch. 130-2); 4humeral shaft becomes nar-
row toward its distal third (ch. 135-1); Femur with: 5absent
or distinct trochanteric fossa (ch. 186-1); 6obturator scars
represented by two rugose impressions (ch. 194-1); 7fem-
oral shaft strongly curvedin lateral view (ch. 200-2); 8well-
developed, deep, fibular trochlea with a distinct proximal de-
pression (ch. 209-1); 9patellar groove wide and flat (ch.
213-0); Tibiotarsus with: 10cranial cnemial crest proximal-
ly expanded and straight (ch. 222-2); 11indistinct cresta
patellaris (ch. 227-2); and 12fibular crest well separated
proximally from the cranial cnemial crest (ch. 228-1).
Type genus.Veg a v i s Clarke et al., 2005.
Included taxa.Polarornis gregorii Chatterjee, 2002;
Ve g a v i s i a a i Clarke et al., 2005;Australornis lovei Mayr and
Scofield, 2014;Neogaeornis wetzeli Lambrecht, 1929.
Temporal and geographical distribution.Latest
Cretaceous and Paleogene of Antarctica, New Zealand, and
Latest Cretaceous and Eocene of Chile (South America)
(Fig. 3).
Discussion
Diving adaptations of vegaviids
Ve g a v i s,Polarornis,andNeogaeornis show the following dis-
tinctive features typically present among foot-propelled div-
ing birds (e.g., Hesperornithidae, Baptornithidae, Gaviidae,
Podicipedidae, Anhingidae): compact and thickened cortex
of hindlimb bones (Fig. 2), femur with anteroposteriorly com-
pressed and bowed shaft, deep fovea ligamentariscapitis,deep
and wide popliteal fossa delimited by a medial ridge, wide
patellar groove, medial condyle smaller than the lateral one,
and expanded fibular condyle; tibiotarsus with notably prox-
imally expanded cnemial crests, expanded fibular crest,
anteroposteriorly compressed shaft, and broad distal extensor
groove; and tarsometatarsus with strongly transversely com-
pressed shaft and asymmetrical distal end with proximally
located distal trochlea II (Chatterjee 2002;Worthyetal.
2007; Ksepka and Cracraft 2008;Noriegaetal.2008;
Cenizo 2012; Acosta Hospitaleche and Gelfo 2015;Fig.1).
Furthermore, in Vegavis and Australornis, the humerus
shows a distally narrowing shaft, strongly marked capital ridge,
and pneumotricipital fossa wide, deep, and non-pneumatic, a
combination of characters typical of diving anseriforms
(Watanabe and Matsuoka 2015). Furthermore, the large dorsal
tubercle does not indicate well-developed soaring capabilities
(Mayr and Scofield 2014).
87 Page 6 of 9 Sci Nat (2017) 104:87
Paleohistological analysis (Garcia Marsà et al. 2017)
(Fig. 2) indicates that Vegavis and Polarornis were diving
birds and, based on the osteosclerotic condition of the femur
and shape of the hindlimb bones, were foot-propelled (Ibañez
and Tambussi 2012). Furthermore, the humeral cross-section
has RBT values that approach taxa that use their wings for
underwater strokes (Humphrey and Livezey 1982), which al-
so may have been the case for Ve g a vi s . These interpretations
are in agreement with Chinsamy et al. (1998) who on the basis
of the high degree of osteosclerosis propose flightless habits
for Polarornis.
Paleobiogeographical implications
Mayr and Scofield (2014) suggested the possibility that early
Paleocene marine avifaunas from New Zealand had a similar
composition to those from Antarctica due to their geographi-
cal closeness. In this context, they also speculated that Ve g a v i s
and Australornis may be closely related, but comparisons be-
tween these taxa were impossible because of the absence of
overlapping materials. The new Veg a v i s specimen MACN-PV
19.748 allows comparing each other, bolstering the suspicion
of these authors.
The geographical proximity, as well as the land connec-
tions among Southern South America and Antarctica, and
the latter continent with Oceania, resulted in a shared fauna
and flora on these landmasses. Zinsmeister (1982) recognized
the Weddellian Bioprovince for the marine invertebrate faunas
shared during the Late Cretaceous and Paleogene of
Patagonia, Antarctica, Australia, and New Zealand. Novas
et al. (2002) indicated that marine reptile faunas for these
southern continents were also related to each other and were
isolated from Laurasian taxa. The same is true for marine fish
faunas (Bogan et al. 2016). On land, the Weddellian realm
includes plants, remarkably Nothofagus, metatherian mam-
mals (Case et al. 1988), and dinosaurs (Agnolin et al. 2010;
Rozadilla et al. 2016). The presence of Vegaviidae in marine
sediments of southern South America, Antarctica, and New
Zealand during the Cretaceous and Paleogene reinforces such
paleobiogeographical scenarios.
Furthermore, the recognition of Polarornis,Ve g a vis,
Neogaeornis,Australornis, and a wide array of isolated spec-
imens as belonging to Vegaviidae also dismisses previous
hypotheses explaining the past distribution of some avian
clades. Acosta Hospitaleche and Gelfo (2015) indicated that
Gaviiformes were abundant during the Late Cretaceous and
Paleogene of Antarctica, but later ecological competition with
sphenisciforms geographically displaced gaviiformes to the
northern hemisphere. Our present reinterpretation of
Antarctic bird remains as possible vegaviid anseriforms,
instead of Gaviiformes, contradicts this alternative
hypothesis. However, we concur with Acosta Hospitaleche
and Gelfo (2015)inthattwodifferentfaunalstagesmaybe
recognized among the Late CretaceousEarly Tertiary diving
birds from southern seas: a first CretaceousPaleocene assem-
blage dominated by vegaviid anseriforms and a second post-
Paleocene stage dominated by penguins.
It is worth mentioning that the oldest record of modern
diving ducks is from the Oligocene of Kazakhastan
(Zelenkov 2012). Vegaviids constitute an early experiment
of diving forms that preceded modern ducks for more than
30 million years.
The fossil record of Mesozoic birds from the Southern
Hemisphere is still relatively poor. In spite of the paucity of
this record, some authors proposed that Southern Hemisphere
Cretaceousavifaunas were dominated by archaic birds such as
enantiornithes and basal ornithurines, and suggested thatmod-
ern birds were absent from the Southern Hemisphere
(Feduccia 2003; Longrich 2008; O'Connor and Forster,
2010). However, documentation of the neornithines Veg a v i s
and Polarornis in Cretaceous beds from Antarctica clearly
demonstrates that modern birds were already present in south-
ern Gondwana by the Late Cretaceous, at least. Furthermore,
recognition that Vegaviidae is a clade deeply nested within
Galloanseres indicates that the early radiation of Neornithes
in Gondwana was more complex than previously thought.
Additionally, the recognition of this group reinforces the hy-
pothesis that southern landmasses constituted a center for
neornithine diversification and emphasizes the role of
Gondwana for the evolutionary history of Anseriformes and
Neornithes as a whole (Ericson et al. 2006;Cracraft2001).
Vegaviidae, first documentation of an avian clade that
survived the K/T boundary
The hypothesis of an avian mass extinction at the KPg
boundary has been hotly debated. Many studies based on mo-
lecular evidence imply mass survival of birds across the KPg
boundary (Hedges et al. 1996; Cooper and Penny 1997),
whereas paleontological studies (see summary in Feduccia
1999,2003,2014; Longrich et al. 2011) claim that a large
neornithine radiation by the Late Cretaceous is not supported
by the present fossil record. The recognition of Vegaviidae in
Cretaceous as well as Paleogene beds constitutes the first doc-
umented clade that crossed the K/T boundary.
Longrich (2008) and Bono et al. (2016), based on the fossil
record from the Northern Hemisphere, considered the possi-
bility that derived ornithurines (including Neornithes)
exploited niches which were available at high latitudes,
whereas Enantiornithes did not. In support of his hypothesis,
Longrich (2008) indicated that Neornithes had remarkably
higher growth rates than enantiornithes, a physiological adap-
tation that may be critical for surviving in seasonal climates at
high latitudes. The same argument may be applied to the high
latitudes in the Southern Hemisphere: all specimens collected
from Antarctica, southern South America, and New Zealand
Sci Nat (2017) 104:87 Page 7 of 9 87
belong to Neornithine-like birds, whereas Enantiornithes and
other basal birds remain unknown from these circumpolar
regions of the southern hemisphere. In this regard,
paleohistological data from Ve g a v i s and Polarornis suggests
that they exhibited relatively rapid and uninterrupted growth
rates as in most living birds (Chinsamy 2002; Padian et al.
2001). High growth rates may have been an advantage in
highly seasonal climates (i.e., presence/absence of freezing
conditions) because it enabled these birds to acquire adult
body size rapidly (see Chinsamy 2002; Bono et al. 2016).
This high growth rate, as demonstrated by paleohistological
analysis on Veg a v i s, may also constitute the key adaptation
that allowed vegaviids to survive the K/T mass extinction
event.
Acknowledgements Special thanks to Y. Davies and S. Bogan who
allowed reviewing material under their care. We are deeply indebted to
S. Lucero, S. Rozadilla, G. Lo Coco, M. Motta, M. Aranciaga Rolando,
and J. DAngelo for their comments and discussion about early bird
radiations. Julia Clarke and Trevor Worthy made valuable comments on
an early draft of this manuscript. Special thanks to T. Worthy for his
enlightening comments on Ve g a vi s specimen and discussions regarding
its phylogenetic position. We also like to thank the anonymous reviewers
who made valuable comments that greatly improved the quality of this
paper. We thank M. Isasi who skillfully prepared the specimen MACN-
PV 19.748 of Veg a v i s .
References
Acosta Hospitaleche C, Gelfo JN (2015) New Antarctic findings of
Upper Cretaceous and lower Eocene loons (Aves: Gaviiformes).
In: Annales de Paléontologie (vol 101, no. 4, pp 315324).
Elsevier Masson, France
Agnolin FL, Ezcurra MD, Pais DF, Salisbury W (2010) A reappraisal of
the Cretaceous nonavian dinosaur faunas from Australia and New
Zealand, evidence for their Gondwanan affinities. J Syst Palaeontol
8:257300
Bogan S, Agnolin FL, Novas FE (2016) New Selachian records from the
Upper Cretaceous of Southern Patagonia, paleobiogeographical im-
plications and the description of a new taxon. J. Vert. Paleont 36(3):
e1105235
Bono RK, Clarke J, Tarduno JA, Brinkman D (2016) A large ornithurine
bird (Tingmiatornis arctica) from the Turonian High Arctic: climatic
and evolutionary implications. Sci Rep 6:38876
Bourdon E (2005) Osteological evidence for sister group relationship
between pseudo-toothed birds (Aves: Odontopterygiformes) and
waterfowls (Anseriformes). Naturwissenschaften 92(12):586591
Case J, Tambussi CP (1999) Maastrichtian record of neornithine birds in
Antarctica, comments on a Late Cretaceous radiation of modern
birds. J. Vert. Paleont 19(3, Suppl):37A
Case JA, Woodburne MO, Chaney DS (1988) A new genus and species
of polydolopid marsupial from the La Meseta Formation, Late
Eocene, Seymour Island, Antarctic Peninsula. In: Feldmann RM,
Woodburne MO (eds) Geology and paleontology of Seymour
Island. Geological Society of America, Boulder, pp 505521
Case J, Reguero M, Martin J, Cordes-Person A (2006) A cursorial bird
from the Maastrichtian of Antarctica. J Vertebr Paleontol 26(3,
Supplement):48A
Cenizo MM (2012) Review of the putative Phorusrhacidae from the
Cretaceous and Paleogene of Antarctica: new records of ratites and
pelagornithid birds. Pol Polar Res 33(3):239258
Chatterjee S (2002) The morphology and systematics of Polarornis, a
Cretaceous loon (Aves, Gaviidae) from Antarctica. In: Zhou Z,
Zhang F (eds) Proceedings of the 5th Symposium of the Society
of Avian Paleontology and Evolution. Science Press, Beijing, pp
125155
Chatterjee S, Martinioni D, Novas F, Mussel F, Templin R (2006) A new
fossil loon from the Late Cretaceous of Antarctica and early radia-
tion of foot-propelled diving birds. J Vertebr Paleontol 26:49A
Chiappe LM (1996) Early avian evolution in the Southern Hemisphere,
the fossil record of birds in the Mesozoic of Gondwana. Mem
Queensland Mus 39:533554
Chiappe LM (2016) Birds of stone, Chinese avian fossils from the age of
dinosaurs. 304 pp. Johns Hopkins University Press, Baltimore
Chinsamy A (2002) Bone microstructure of early birds. In: Chiappe LM,
Witmer LM (eds) Mesozoic birds, above the heads of dinosaurs.
Univ. California Press, Berkeley, pp 421431
Chinsamy A, Martin LD, Dodson P (1998) Bone microstructure of the
diving Hesperornis and the volant Ichthyornis from the Niobrara
Chalk of western Kansas. Cretac Res 19:225235
Clarke JA, Tambussi CP, Noriega JI, Erickson GM, Ketcham RA (2005)
Definitive fossil evidence for the extant avian radiation in the
Cretaceous. Nature 433:305308
Clarke JA, Chatterjee S, Li Z, Riede T, Agnolin F, Goller F, Novas FE
(2016) Fossil evidence of the avian vocal organ from the Mesozoic.
Nature 538(7626):502505
Cooper A, Penny D (1997) Mass survival of birds across the Cretaceous
Tertiary boundary, Molecular evidence. Science 275:11091113
Cordes AH (2002) A new charadriiform avian specimen from the early
Maastrichtian of Cape Lamb, Vega Island, Antarctic Peninsula. J
Vertebr Paleontol 22:99A
Cracraft J (2001) Avian evolution, Gondwana biogeography, and the
CretaceousTertiary mass extinction event. Proc. Roy. Soc.
London B 1268:459469
Cracraft J, Clarke J (2001) The basal clades of modern birds. In: New
perspectives on the origin and early evolution of birds: proceedings
of the international symposium in honor of John H. Ostrom.
Peabody Museum of Natural History, New Haven, pp 143152
De Mendoza R, Tambussi C (2015) Osteosclerosis in the extinct Cayaoa
bruneti (Aves, Anseriformes). Insights on behavior and
flightlessness. Ameghiniana 52:305313
De Pietri VL, Scofield RP, Zelenkov N, Boles WE, Worthy TH (2016)
The unexpected survival of an ancient lineage of anseriform birds
into the Neogene of Australia: the youngest record of
Presbyornithidae. Open Sci 3(2):150635
Dzerzhinsky FY (1995) Evidence for common ancestry of the
Galliformes and Anseriformes. Cour Forschungsinst Senck 181:
325336
Ericson PG (1997) Systematic relationships of the Palaeogene family
Presbyornithidae (Aves: Anseriformes). Zool J Linnean Soc
121(4):429483
Ericson PG, Anderson CL, Britton T, Elzanowski A, Johansson US,
Källersjö M, Mayr G (2006) Diversification of Neoaves: integration
of molecular sequence data and fossils. Biol Lett 2(4):543547
Feduccia A (1999) The origin and evolution of birds. Yale University
Press, New Haven 245 pp
Feduccia A (2003) BBig Bang^for Tertiary birds? Trends Ecol. Evolution
16:172176
Feduccia A (2014) Avian extinction at the end of the Cretaceous:
assessing the magnitude and subsequent explosive radiation.
Cretac Res 50:115
Garcia Marsà JA, Agnolín FL, Novas F (2017) Bone microstructure of
Ve g a vi s i a a i (Aves, Anseriformes) from the Upper Cretaceous of
Vega Island, Antarctic Peninsula Historical Biology, 15
87 Page 8 of 9 Sci Nat (2017) 104:87
Hedges SB, Parker PH, Sibley CG, Kumar S (1996) Continental breakup
and the ordinal diversificationofbirdsandmammals.Nature
381(6579):226
Hope S (2002) The Mesozoic radiation of Neornithes. In: Chiappe LM,
Witmer LM (eds) Mesozoic birds, above the heads of dinosaurs.
Berkeley University Press, Berkeley, pp 168218
Humphrey PS, Livezey BC (1982) Flightlessness in flying steamer-
ducks. Auk 99:368372
Ibañez B, Tambussi CP (2012) Foot-propelled aquatic birds, pelvic mor-
phology and locomotor performance. Ital J Zool 79:356362
Ksepka DT, Cracraft J (2008) An avian tarsometatarsus from near the KT
boundary of New Zealand. J Vertebr Paleontol 28(4):12241227
Longrich N (2008) An ornithurine-dominated avifauna from the Belly
River Group (Campanian, Upper Cretaceous) of Alberta, Canada.
Cret Res 30:161177
Longrich NR, Tokaryk T, Field DJ (2011) Massextinction of birds at the
CretaceousPaleogene (KPg) boundary. PNAS 108:1525315257
Mayr G (2008) Phylogenetic affinities and morphology of the late Eocene
anseriform bird Romainvillia stehlini Lebedinsky, 1927. Neues
Jahrb Geol Paläontol-Abh 248(3):365380
Mayr G (2009) Paleogene fossil birds. Springer, Berlin 262 pp
Mayr G (2011) Metaves, Mirandornithes, Strisores and other novelties
a critical review of the higher-level phylogeny of neornithine birds. J
Zool Syst Evol Res 49(1):5876
Mayr G, Clarke J (2003) The deep divergences of neornithine birds: a
phylogenetic analysis of morphological characters. Cladistics 19:
527553
Mayr G, Poschmann M (2009) A loon leg (Aves, Gaviidae) with croco-
dilian tooth from the late Oligocene of Germany. Waterbirds 32(3):
468471
Mayr G, Scofield RP (2014) First diagnosable non-sphenisciform bird
from the early Paleocene of New Zealand. J R Soc N Z 44(1):4856
Mayr G, Zvonok E, Gorobets L (2013) The tarsometatarsus of the middle
Eocene loon Colymbiculus udovichenkoi. In: Göhlich UB, Kroh A
(eds) Paleornithological research 2013proceedings of the 8th
International Meeting of the Society of Avian Paleontology and
Evolution. Natural History Museum Vienna, Vienna, pp 1722
306 pp
Noriega JI, Tambussi CP (1995) A Late Cretaceous Presbyornithidae
(Aves: Anseriformes) from Vega Island, Antarctic Peninsula:
paleobiogeographic implications. Ameghiniana 32(1):5761
Noriega JI, Tambussi CP, Cozzuol MA (2008) New material of Cayaoa
bruneti Tonni, an early Miocene anseriform (Aves) from Patagonia,
Argentina. Neues Jahrb Geol Paläontol-Abh 249(3):271280
Novas FE, Cambiaso AV, Lirio JM, Núñez HJ (2002) Paleobiogeografía
de los dinosaurios polares de Gondwana. Ameghiniana 39:15R
O'Connor PM, Forster CA (2010) A Late Cretaceous (Maastrichtian)
avifauna from the Maevarano Formation, Madagascar. J Vertebr
Paleontol 30(4):11781201
Olson SL (1992) Neogaeornis wetzeli Lambrecht, a Cretaceous loon from
Chile (Aves, Gaviidae). J Vert Paleont 12:122124
Olson SL, Feduccia A (1980) Presbyornis and the origin of the
Anseriformes (Aves: Charadriomorphae) (No. 598.2 OLSp).
Smithsonian Institution Press
Padian K, Chiappe LM (1998) The origin and early evolution of birds.
Biol Rev 73(1):142
Padian K, de Ricqlés AJ, Horner JR (2001) Dinosaurian growth rates and
bird origins. Nature 412:405408
Reguero M, Goin F, Acosta Hospitaleche C, Dutra T, Marenssi S (2013)
Late Cretaceous/Paleogene West Antarctica terrestrial biota and its
intercontinental affinities, p 120
Rozadilla S, Agnolin FL, Novas FE, Aranciaga AR, Motta MJ, Lirio JM,
Isasi MP (2016) A new ornithopod (Dinosauria, Ornithischia) from
the Upper Cretaceous of Antarctica and its palaeobiogeographical
implications. Cretac Res 57:311324
Smith ND (2010) Phylogenetic analysis of Pelecaniformes (Aves) based
on osteological data: implications for waterbird phylogeny and fossil
calibration studies. PLoS One 5(10):e13354
Smith NA, Clarke JA (2014) Osteological histology of the Pan-Alcidae
(Aves, Charadriiformes), correlates of wing-propelled diving and
flightlessness. Anat Rec 297:188199
Tambussi CP, Degrange FJ (2013) The Paleogene birds of South
America. In: South American and Antarctic Continental Cenozoic
Birds. Springer Netherlands, pp 2947
Van Tuinen M, Hedges SB (2004) The effect of external and internal
fossil calibrations on the avian evolutionary timescale. J Paleontol
78(1):4550
Watanabe J, Matsuoka H (2015) Flightless diving duck (Aves, Anatidae)
from the Pleistocene of Shiriya, northeast Japan. J Vertebr Paleontol
35(6):e994745
Weber E, Hesse A (1995) The systematic position of Aptornis, a flightless
bird from New Zealand. Cour Forschungsinst Senck 181:293301
Woolfenden GE (1961) Postcranial osteology of the waterfowl.
University of Florida, Gainesville
Worthy TH, Tennyson AJ, Jones C, McNamara JA, Douglas BJ (2007)
Miocene waterfowl and other birds from Central Otago, New
Zealand. J Syst Palaeontol 5(1):139
Worthy TH, Mitri M, Handley WD, Lee MS, Anderson A, Sand C (2016)
Osteology supports a stem-galliform affinity for the giant extinct
flightless bird Sylviornis neocaledoniae (Sylviornithidae,
Galloanseres). PLoS One 11(3):e0150871
Yury-Yáñez RE, Otero RA, Soto-Acuña S, Suárez ME, Rubilar-Rogers
D, Sallaberry M (2012) First bird remains from the Eocene of
Algarrobo, central Chile. Andean Geol 39(3):548557.
Zelenkov NV (2012) A new duck from the Middle Miocene of Mongolia,
with comments on Miocene evolution of ducks. Paleontol J 46(5):
520530
Zinsmeister WJ (1982) Late CretaceousEarly Tertiary molluscan bioge-
ography of the southern circum-Pacific. J Paleontol 56:84102
Sci Nat (2017) 104:87 Page 9 of 9 87
... More recently, the description of the second specimen (previously MLP 93-I-3-2, now MACN-PV 19.748 housed in the Museo Argentino de Ciencias Naturales in Ciudad Aut onoma de Buenos Aires, Argentina) from the same stratigraphic horizon and locality as the holotype revealed hitherto unknown morphology for the taxon (Clarke et al., 2016). Far from providing improved phylogenetic resolution, the analyses on expanded datasets incorporating data from both individuals resolved Vegavis outside crown-group Anseriformes (Agnolin et al., 2017;Worthy et al., 2017). Worthy et al. (2017) found the relationship of Vegavis was unresolved relative to Galliformes or Anseriformes within Galloanseres. ...
... Worthy et al. (2017) found the relationship of Vegavis was unresolved relative to Galliformes or Anseriformes within Galloanseres. In contrast, Agnolin et al. (2017) found that the clade Vegaviidae, which including Vegavis and several other taxa, was the sister group to crown Anseriformes. The proposal by Agnolin et al. (2017) to include in Vegaviidae, type genus Vegavis, such disparate taxa as Polarornis gregorii Chatterjee, 2002, Australornis lovei Mayr and Scofield, 2014, and Neogaeornis wetzeli Lambrecht, 1929 was strongly criticized by most of the paleornithological community (e.g. ...
... In contrast, Agnolin et al. (2017) found that the clade Vegaviidae, which including Vegavis and several other taxa, was the sister group to crown Anseriformes. The proposal by Agnolin et al. (2017) to include in Vegaviidae, type genus Vegavis, such disparate taxa as Polarornis gregorii Chatterjee, 2002, Australornis lovei Mayr and Scofield, 2014, and Neogaeornis wetzeli Lambrecht, 1929 was strongly criticized by most of the paleornithological community (e.g. Mayr et al., 2018). ...
Article
Vegavis iaai has key importance as the most complete of the few neornithine birds known from the Cretaceous, yet its phylogenetic relationships remain controversial. To seek new data to resolve this problem, we fully extracted the skeleton of the holotype MLP 93-I-3-1 from the sedimentary matrix it had been found in to enable new direct observations on its osteology. We provide the first detailed descriptions of the synsacrum confirming the presence of fifteen ankylosed vertebrae, and of the cervical and thoracic vertebrae for this specimen, and elaborate on the available descriptions of the coracoid, humerus, radius, and all pelvic limb elements. A well-marked proximo-caudal fossa of the femur, described as a diagnostic character for Vegavis from observations of the referred specimen, is shallow and poorly defined in the holotype. The skeleton reveals a mix of features supporting enhanced diving ability for the bird. We make three-dimensional scans and high-quality images of all bones in the holotype available for further comparisons.
... Las contribuciones sobre aves fósiles comenzaron con los trabajos sobre las colecciones efectuadas por Otto Nordenskjöld (1901Nordenskjöld ( -1903. Poco después de que estos restos atribuidos a pingüinos (Sphenisciformes) fueran descritos (Wiman, 1905), Florentino Ameghino revisó y discutió estas asignaciones en un extenso trabajo sobre los pingüinos fósiles de Patagonia e isla Marambio (Seymour) en la que se ilustra material antártico (Ameghino, 1905). ...
... Our results also shed further light on the phylogenetic affinities of two other Late Cretaceous birds, Vegavis and Asteriornis. Initially proposed to be a stem anatid within waterfowl (Anseriformes), the phylogenetic affinities of the Antarctic Vegavis have been controversial (43)(44)(45). We recover Vegavis in its traditional place within crown group waterfowl in a polytomy with the Mallard (Anas platyrhynchus) and the Early Paleocene Antarctic bird Conflicto (Fig. 3) (46). ...
Article
Full-text available
Birds today are the most diverse clade of terrestrial vertebrates, and understanding why extant birds (Aves) alone among dinosaurs survived the Cretaceous-Paleogene mass extinction is crucial to reconstructing the history of life. Hypotheses proposed to explain this pattern demand identification of traits unique to Aves. However, this identification is complicated by a lack of data from non-avian birds. Here, we interrogate survivorship hypotheses using data from a new, nearly complete skull of Late Cretaceous (~70 million years) bird Ichthyornis and reassess shifts in bird body size across the Cretaceous-Paleogene boundary. Ichthyornis exhibited a wulst and segmented palate, previously proposed to have arisen within extant birds. The origin of Aves is marked by larger, reshaped brains indicating selection for relatively large telencephala and eyes but not by uniquely small body size. Sensory system differences, potentially linked to these shifts, may help explain avian survivorship relative to other dinosaurs.
... Should the fragmentary Teviornis fall out elsewhere, the minimum age might nonetheless not have to rest on Asteriornis, because Vegaviidae, a clade containing the late Maastrichtian (Clarke et al., 2005;Salazar et al., 2010) Vegavis, Polarornis, and Neogaeornis and probably the end-Campanian (McLachlan et al., 2017) Maaqwi, has been found on the anserimorph stem in some of the latest analyses (Agnolín et al., 2017;Tambussi et al., 2019). However, Mayr et al. (2018) discussed reasons for skepticism, and the analyses of McLachlan et al. (2017), Bailleul et al. (2019: supplementary trees 7-11, 16, 17), Field et al. (2020), andO'Connor et al. (2020) found the vegaviids they included close to but outside Aves (or at least Galloanserae in the case of Bailleul et al., 2019;O'Connor et al., 2020, who did not sample Neoaves or Palaeognathae in the analyses in question). ...
Article
Full-text available
Molecular divergence dating has the potential to overcome the incompleteness of the fossil record in inferring when cladogenetic events (splits, divergences) happened, but needs to be calibrated by the fossil record. Ideally but unrealistically, this would require practitioners to be specialists in molecular evolution, in the phylogeny and the fossil record of all sampled taxa, and in the chronostratigraphy of the sites the fossils were found in. Paleontologists have therefore tried to help by publishing compendia of recommended calibrations, and molecular biologists unfamiliar with the fossil record have made heavy use of such works (in addition to using scattered primary sources and copying from each other). Using a recent example of a large node-dated timetree inferred from molecular data, I reevaluate all 30 calibrations in detail, present the current state of knowledge on them with its various uncertainties, rerun the dating analysis, and conclude that calibration dates cannot be taken from published compendia or other secondary or tertiary sources without risking strong distortions to the results, because all such sources become outdated faster than they are published: 50 of the (primary) sources I cite to constrain calibrations were published in 2019, half of the total of 280 after mid-2016, and 90% after mid-2005. It follows that the present work cannot serve as such a compendium either; in the slightly longer term, it can only highlight known and overlooked problems. Future authors will need to solve each of these problems anew through a thorough search of the primary paleobiological and chronostratigraphic literature on each calibration date every time they infer a new timetree, and that literature is not optimized for that task, but largely has other objectives.
... The position of the Late Cretaceous (69-66 Mya) Vegavis iaii was reviewed in two studies published in 2017. Agnolín et al. (2017) proposed a new anseriform family, Vegaviidae, to include Vegavis iaii and other Palaeogene divers of the Southern Hemisphere. Worthy et al. (2017), evaluating the evolution of giant flightless Galloanseres, excluded Vegavis iaii from crown group Anseriformes and proposed a new order, Vegaviiformes. ...
Article
A new Anseriformes, Conflicto antarcticus gen. et sp. nov., represented by associated bones of a single individual, from the early Palaeocene of Antarctica is described. The new taxon is unlike any other known member of the order. Conflicto antarcticus is a medium-sized (2 kg) stem anseriform. The forelimb and pectoral girdle bones suggest that it was a flying bird, and the bones of the hindlimb show that it had elongated legs. The os quadratum represents a unique combination of features; some are similar to the features of the ancestral quadrate for galloanserines and some are similar to Anseriformes, but features such as the presence of three foramina are exclusive among Neornithes. The incisura or foramen nervi suracoracoidei is absent in C. antarcticus, as in most anatids and all Galliformes. Phylogenetic analysis shows that C. antarcticus + Anatalavis oxfordi is the most basal stem Anseriformes clade. This implies that the duck-type beak must have developed at an early stage of anseriform evolution. Conflicto antarcticus represents one (and possibly the most) substantial record of a non-marine Palaeocene bird from the Southern Hemisphere and supports the hypothesis that Neognathae had already diversified in the earliest Palaeocene.
... transitional link between presbyornithids and modern ducks (Mayr, 2008). This allows presbyornithids to be considered the probable ancestors of Anatidae s. l. or, more likely, the ancestors of all Anatoidea (Anseranatidae + Anatidae s. l.), since presbyornithids appear in modern phylogenetic analyses as a sister group to all Anatoidea (Agnolin et al., 2017;Worthy et al., 2017). If the latter is true (Presbyornithidae are the ancestors of Anatoidea), then Anseranatidae can be considered a rather early deviation from the common phylogenetic stem of Anatidae and, possibly, a morphologically aberrant branch. ...
Article
Full-text available
An analysis of the Eurasian Cenozoic (late Eocene-Neogene) fossil record of anatids (Anatidae s. l.; including Romainvilliinae and Dendrocygninae) is presented. The evolutionary origin of Anatidae s. l. may be associated with the appearance of large shallow waterbodies in Asia during the Late Eocene as a result of the fall in the global sea level and the resulting retreat of the epicontinental seas. Four major temporal stages can be recognized in the evolution of the Cenozoic Eurasian anatids communities, without any traceable continuity between particular stages (at the current stage of knowledge). Some recent anatid genera (e.g., Tadorna) first appear in the paleontological record at the level of the early and middle Miocene (17-15 Ma), but temperate faunas of essentially modern ecological composition became widespread only in the late Mio-cene (9-6 Ma). The details of transitions between various faunistic stages, as well as the origin of modern communities, remain largely unstudied.
Chapter
There is strong molecular support for a clade including the non-monophyletic “Pelecaniformes” except the Phaethontiformes (tropicbirds), as well as the Sphenisciformes (penguins), Gaviiformes (loons), Procellariiformes (tubenoses), and the taxa of the non-monophyletic “Ciconiiformes”. This “waterbird clade” was termed Aequornithes, and the Phaethontiformes result as close relatives of it in current analyses. The fossil record shows that the Aequornithes have a very long evolutionary history. Stem group representatives of the Sphenisciformes date back to the mid-Paleocene and stem group Procellariiformes may have already existed in the Late Cretaceous. The early evolution of the Aequornithes remains, however, poorly understood. The skeletal morphology of early Eocene stem group representatives of the Threskiornithidae, for example, is markedly different from that of coeval Sphenisciformes, which indicates a long evolutionary separation of the lineages leading to these two taxa already by that time. It is also elusive where the stem species of the Aequornithes occurred, although this may well have been on one of the southern continents.
Article
The deposits of the Chorrillo Formation (Maastrichtian) were accumulated during a ‘continental window’ that occurred during the Late Cretaceous in the Austral-Magallanes foreland basin, southern Patagonia, Argentina. The aim of the present contribution is to describe the depositional conditions as well as new vertebrate and plant fossils from this unit. The analysis of these deposits resulted in the definition of five architectural elements: Complex sandy narrow sheets channels (SS), Complex gravelly narrow sheets channels (GS), Sandstone lobes (SL), Thick fine-grained deposits (GF) and Thin dark fine-grained deposits (DF). These were separated into channelized and non-channelized units and represent the accumulation in a fine-grained dominated, fossil rich fluvial depositional system. Vertebrates fossil records include two species of frogs of the genus Calypteocephalella (representing the southernmost record of Pipoidea), snakes belonging to Madtsoiidae and Anilioidea (the latter ones being the first records for the basin), chelid turtles similar to Yaminuechelys-Hydromedusa, meiolaniiform turtles, titanosaur sauropods, megaraptoran theropods, new remains of the elasmarian Isasicursor santacrucensis (including the first cranial remains available for this species), hadrosaur ornithischians, enantiornithine birds. Sharks and elasmosaurs are also recorded and may possibly derive from the overlying marine Calafate Formation. These new taxa, together with previous findings from the Chorrillo Formation, are included into a stratigraphic column, thus providing valuable information that sheds new light on faunistic composition and paleobiogeography of high-latitude biotas of Gondwana.
Chapter
Molecular clocks can be used to reconstruct evolutionary timescales based on analyses of genetic data, but these clocks need to be calibrated in order to give estimates in absolute time. Calibration is most often carried out using fossil evidence of the timing of evolutionary events, corresponding to internal nodes in phylogenetic trees. Early molecular dating studies treated fossil calibrations as point values, whereas later methods allowed calibrations to be specified as age constraints on nodes. The application of Bayesian methods to phylogenetic analysis opened up opportunities for fossil calibrations to take more complex forms. In this chapter, we trace the development and use of fossil calibrations and describe some a priori and a posteriori methods and criteria for evaluating their quality. We then present two examples of fossil calibrations from modern birds. Our chapter concludes with a discussion of the limitations of fossil calibrations, along with the changing role of the palaeontological record in molecular dating.
Article
Full-text available
A specialized diving lifestyle has repeatedly evolved in several lineages of modern and fossil waterfowl (Anseriformes), with the oldest previously known representative being the late Oligocene Australian oxyurine ducks Pinpanetta. However, diving specializations have never been previously documented for any of the primitive Paleogene anseriforms ( “stem-anatids”), and thus may be associated with the origin of modern anatid-like body plan. Here I describe a tarsometatarsus of a new duck-sized diving anseriform bird from the latest Eocene (late Priabonian) Kusto Svita in Eastern Kazakhstan, which predates the previously reported occurrence of diving specialization in Anseriformes by at least 6 MA. The new taxon Cousteauvia kustovia gen. et sp. nov. has an unusual and previously undocumented morphology, but partly resembles the stem-anatids Paranyrocidae and Romainvilliidae, thus representing the first known occurrence of diving adaptations in primitive non-anatid anseriforms. The evolutionary appearance of specialized waterfowl taxa in the late Eocene of Central Asia supports a view that this region might have played an important role in the evolution of morphologically derived Anseriformes. The structure of the intertarsal joint in basal and modern anseriforms is here further discussed in relation with adaptations for aquatic locomotion. The presence of elongate and evenly narrow condyles of the tibiotarsus in Anatidae and other swimming/diving birds allows a firm contact with the hyperprotracted tarsometatarsus at the initial phase of the propulsion. This morphology contrasts with the restricted condyles of Presbyornithidae, which indicate a different, strictly wading locomotory specialization. Cousteauvia obviously evolved diving specializations on the basis of a more primitive structure of the intertarsal joint.
Article
Full-text available
Vegavis iaai is a neornithine bird coming from the Late Cretaceous Sandwich Bluff Member of the López de Bertodano Formation (Maastrichtian), Antarctic Peninsula. Vegavis constitutes the only unquestionable Cretaceous neornithine bird, and is known by the holotype and specimen MACN-PV 19.748. The goal of this paper is to present a detailed osteohistological analysis of V. iaai. Vegavis shows a highly vascularized fibrolamellar matrix lacking lines of arrested growths, features widespread among modern birds. This is consistent with previous hypotheses indicating that modern birds were dominant at high latitudes. This is probably related to high-metabolic rates shared by modern birds, whereas archaic taxa as Enantiornithes are absent or form a minority part of High-Latitude bird assemblages. Vegavis was a diver, characterised by a certain degree of limb osteosclerosis, with an increase of bone inner compactness, and inhibition of secondary remodelling, with no effect on the external dimensions of the bone, a combination of characters related to diving lifestyle. Based on Relative Bone Thickness it is possible to infer that Vegavis was a foot-propelled diving bird, similar to some extant anseriforms. Occurrence of osteosclerotic limb bones in Vegavis and Polarornis may constitute a derived shared feature, sustaining the hypothesis that both taxa are phylogenetically related.
Article
Full-text available
Bird fossils from Turonian (ca. 90 Ma) sediments of Axel Heiberg Island (High Canadian Arctic) are among the earliest North American records. The morphology of a large well-preserved humerus supports identification of a new volant, possibly diving, ornithurine species (Tingmiatornis arctica). The new bird fossils are part of a freshwater vertebrate fossil assemblage that documents a period of extreme climatic warmth without seasonal ice, with minimum mean annual temperatures of 14 °C. The extreme warmth allowed species expansion and establishment of an ecosystem more easily able to support large birds, especially in fresh water bodies such as those present in the Turonian High Arctic. Review of the high latitude distribution of Northern Hemisphere Mesozoic birds shows only ornithurine birds are known to have occupied these regions. We propose physiological differences in ornithurines such as growth rate may explain their latitudinal distribution especially as temperatures decline later in the Cretaceous. Distribution and physiology merit consideration as factors in their preferential survival of parts of one ornithurine lineage, Aves, through the K/Pg boundary.
Book
Full-text available
When fossils of birds from China's Jehol region first appeared in scientific circles, the world took notice. These Mesozoic masterpieces are between 120 and 131 million years old and reveal incredible details that capture the diversity of ancient bird life. Paleontologists all over the world began to collaborate with Chinese colleagues as new and wondrous fossil-related discoveries became regular events. The pages of National Geographic and major scientific journals described the intricate views of feathers as well as food still visible in the guts of these ancient birds. Now, for the first time, a sweeping collection of the most interesting of Jehol's avian fossils is on display in this beautiful book. Birds of Stone makes visible the unexpected avian diversity that blanketed the earth just a short time (geologically speaking) after a dinosaur lineage gave rise to the first birds. Our visual journey through these fossils is guided by Luis M. Chiappe, a world expert on early birds, and Meng Qingjin, a leading figure in China's natural history museum community. Together, they help us understand the "meaning" of each fossil by providing straightforward narratives that accompany the full-page photographs of the Jehol discoveries.
Article
Full-text available
From complex songs to simple honks, birds produce sounds using a unique vocal organ called the syrinx. Located close to the heart at the tracheobronchial junction, vocal folds or membranes attached to modified mineralized rings vibrate to produce sound. Syringeal components were not thought to commonly enter the fossil record, and the few reported fossilized parts of the syrinx are geologically young (from the Pleistocene and Holocene (approximately 2.5 million years ago to the present)). The only known older syrinx is an Eocene specimen that was not described or illustrated. Data on the relationship between soft tissue structures and syringeal three-dimensional geometry are also exceptionally limited. Here we describe the first remains, to our knowledge, of a fossil syrinx from the Mesozoic Era, which are preserved in three dimensions in a specimen from the Late Cretaceous (approximately 66 to 69 million years ago) of Antarctica. With both cranial and postcranial remains, the new Vegavis iaai specimen is the most complete to be recovered from a part of the radiation of living birds (Aves). Enhanced-contrast X-ray computed tomography (CT) of syrinx structure in twelve extant non-passerine birds, as well as CT imaging of the Vegavis and Eocene syrinxes, informs both the reconstruction of ancestral states in birds and properties of the vocal organ in the extinct species. Fused rings in Vegavis form a well-mineralized pessulus, a derived neognath bird feature, proposed to anchor enlarged vocal folds or labia. Left-right bronchial asymmetry, as seen in Vegavis, is only known in extant birds with two sets of vocal fold sound sources. The new data show the fossilization potential of the avian vocal organ and beg the question why these remains have not been found in other dinosaurs. The lack of other Mesozoic tracheobronchial remains, and the poorly mineralized condition in archosaurian taxa without a syrinx, may indicate that a complex syrinx was a late arising feature in the evolution of birds, well after the origin of flight and respiratory innovations.
Article
Full-text available
The giant flightless bird Sylviornis neocaledoniae (Aves: Sylviornithidae) existed on La Grande Terre and Ile des Pins, New Caledonia, until the late Holocene when it went extinct shortly after human arrival on these islands. The species was generally considered to be a megapode (Megapodiidae) until the family Sylviornithidae was erected for it in 2005 to reflect multiple cranial autapomorphies. However, despite thousands of bones having been reported for this unique and enigmatic taxon, the postcranial anatomy has remained largely unknown. We rectify this deficiency and describe the postcranial skeleton of S. neocaledoniae based on ~600 fossils and use data from this and its cranial anatomy to make a comprehensive assessment of its phylogenetic affinities. Sylviornis neocaledoniae is found to be a stem galliform, distant from megapodiids, and the sister taxon to the extinct flightless Megavitiornis altirostris from Fiji, which we transfer to the family Sylviornithidae. These two species form the sister group to extant crown-group galliforms. Several other fossil galloanseres also included in the phylogenetic analysis reveal novel hypotheses of their relationships as follows: Dromornis planei (Dromornithidae) is recovered as a stem galliform rather than a stem anseriform; Presbyornis pervetus (Presbyornithidae) is the sister group to Anseranatidae, not to Anatidae; Vegavis iaai is a crown anseriform but remains unresolved relative to Presbyornis pervetus, Anseranatidae and Anatidae. Sylviornis neocaledoniae was reconstructed herein to be 0.8 m tall in a resting stance and weigh 27-34 kg. The postcranial anatomy of S. neocaledoniae shows no indication of the specialised adaptation to digging seen in megapodiids, with for example, its ungual morphology differing little from that of chicken Gallus gallus. These observations and its phylogenetic placement as stem galliforms makes it improbable that this species employed ectothermic incubation or was a mound-builder. Sylviornis neocaledoniae can therefore be excluded as the constructor of tumuli in New Caledonia.
Article
Birds evolved from and are phylogenetically recognized as members of the theropod dinosaurs; their first known member is the Late Jurassic Archaeopteryx, now represented by seven skeletons and a feather, and their closest known non-avian relatives are the dromaeosaurid theropods such as Deinonychus. Bird flight is widely thought to have evolved from the trees down, but Archaeopteryx and its outgroups show no obvious arboreal or tree-climbing characters, and its wing planform and wing loading do not resemble those of gliders. The ancestors of birds were bipedal, terrestrial, agile, cursorial and carnivorous or omnivorous. Apart from a perching foot and some skeletal fusions, a great many characters that are usually considered ‘avian’ (e.g. the furcula, the elongated forearm, the laterally flexing wrist and apparently feathers) evolved in non-avian theropods for reasons unrelated to birds or to flight. Soon after Archaeopteryx, avian features such as the pygostyle, fusion of the carpometacarpus, and elongated curved pedal claws with a reversed, fully descended and opposable hallux, indicate improved flying ability and arboreal habits. In the further evolution of birds, characters related to the flight apparatus phylogenetically preceded those related to the rest of the skeleton and skull. Mesozoic birds are more diverse and numerous than thought previously and the most diverse known group of Cretaceous birds, the Enantiornithes, was not even recognized until 1981. The vast majority of Mesozoic bird groups have no Tertiary records: Enantiornithes, Hesperornithiformes, Ichthyornithiformes and several other lineages disappeared by the end of the Cretaceous. By that time, a few Linnean ‘Orders’ of extant birds had appeared, but none of these taxa belongs to extant ‘families’, and it is not until the Paleocene or (in most cases) the Eocene that the majority of extant bird ‘Orders’ are known in the fossil record. There is no evidence for a major or mass extinction of birds at the end of the Cretaceous, nor for a sudden ‘bottleneck’ in diversity that fostered the early Tertiary origination of living bird ‘Orders’.