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Vorona berivotrensis, a Primitive Bird from the Late Cretaceous of Madagascar

Forster et al. Vorona 621
Vorona berivotrensis, a Primitive Bird from the Late Cretaceous of Madagascar
Catherine A. Forster, Luis M. Chiappe, David W. Krause, and Scott D. Sampson
Running head: Forster et al.Vorona
Forster et al. Vorona 622
Vorona berivotrensis was discovered in the Upper Cretaceous (Maastrichtian) Maevarano
Formation, Mahajanga Basin, northwestern Madagascar (Rogers et al., 2000) in the austral winter
of 1995 by a joint State University of New York at Stony Brook-Université d’Antananarivo
expedition. Three specimens assigned to Vorona and previously described by Forster et al.
(1996a) were recovered from a productive quarry (site MAD 93-18) near the village of Berivotra.
This quarry has also produced a partial skeleton of the primitive bird Rahonavis ostromi (Forster
et al., 1998), teeth of the large abelisaurid theropod Majungatholus atopus, a nearly complete
skeleton and partial skull of a juvenile titanosaurid sauropod dinosaur, as well as isolated
elements of an undescribed small abelisaurid, crocodilians, fish, frogs, snakes, turtles, and at
least three additional taxa of birds (Krause et al., 1997a, 1999; Forster et al., 1996a, b; Fig. 12.1).
Interestingly, the faunal composition at site MAD 93-18 is nearly identical to that of the Late
Cretaceous El Brete site (Lecho Formation), Salta Province, Argentina, where a quarry in fluvial
sandstone produced four taxa of birds, associated titanosaurid sauropod remains, teeth of a large
theropod, and scattered elements of a small theropod (Bonaparte and Powell, 1980; Chiappe,
Place Figure 12.1 near here
Vorona was the first pre-Holocene avian described from Madagascar. The record of
Mesozoic birds in Gondwana is very poor, and no Jurassic birds have yet been discovered
(Chiappe, 1995, 1996b; Fig. 12.2). For the Cretaceous there is a growing number of taxa known
from South America, particularly Argentina (e.g., Walker, 1981; Chiappe, 1991, 1993; Alvarenga
and Bonaparte, 1992; Chiappe and Calvo, 1994; Novas, 1996). However, there are only three
occurrences of skeletal remains of Cretaceous birds outside of South America: two from the
Antarctic Peninsula (Chatterjee, 1989; Noriega and Tambussi, 1995; see also Hope, this volume)
and one from eastern Australia (Molnar, 1986). Several footprints from a single locality in the
Cretaceous of Morocco (Ambroggi and Lapparent, 1954; see also Lockley and Rainforth, this
volume) are the only record of Mesozoic birds from a large part of Gondwana that includes
Africa, Madagascar, the Indian subcontinent, and mainland Antarctica. Vorona thus marks the
first Mesozoic record of avian skeletal remains from this large area of the world.
Place Figure 12.2 near here
The extant Malagasy avifauna is striking in its low diversity (only 256 species) and high
endemism (53% of species) (Langrand 1990), which are odd characteristics in view of the high
habitat diversity on the island and the high vagility of birds relative to most other vertebrates.
Whether or not Madagascar obtained some of its modern and recently extinct avifauna prior to
separation from other major landmasses has been the subject of some considerable speculation
and controversy (Andrews, 1894; Lamberton, 1934; Rand, 1936; Darlington, 1957; Battistini,
1965; Moreau, 1966; Dorst, 1972; Mahé, 1972; Sauer, 1972; Cracraft, 1973, 1974; Feduccia,
1980; Keith, 1980; Briggs, 1995; Quammen, 1996; Chatterjee, 1997). Keith (1980:106), for
instance, posed the question in the following manner: "Are any of the birds found on Madagascar
today descendants of those that remained behind after its separation, or did all of these become
extinct, leaving Madagascar to be populated by birds that later flew in from overseas?" He
concluded that "the fossil record is so poor that unless further discoveries are made we may never
have a proper answer to this question."
The published record of fossil birds from Madagascar is indeed poor. Outside of the
avifauna recovered from the Maevarano Formation, it is restricted to the Holocene (MacPhee et
al. 1985). This, in turn, is owing in no small measure to the overwhelming predominance of
marine strata throughout the Cenozoic (Besairie, 1972). Included among extinct forms are the
FIGURE 12.1. Map showing the general location of quarry site MAD93-18 (marked
Study Area) in the Upper Cretaceous (Maastrichtian) Maevarano Formation. Inset map
shows the location of the Mahajanga Basin (in black) in northwestern Madagascar. At
least four taxa of fossil birds, including Vorona berivotrensis (described here) and
Rahonavis ostromi (Forster et al., 1998), were recovered from this site. Exact locality
information is on file in the Department of Geology, Field Museum of Natural History,
FIGURE 12.2. Right femur of referred specimen FMNH PA 715: A) cranial, lateral,
caudal, and medial views (left to right); B) proximal view, femoral head to the left (top),
and distal view, cranial surface facing up (bottom). Abbreviation: tc, trochanteric crest.
Scale bars = 1 cm.FIGURE 12.2. Right femur of referred specimen FMNH PA 715: A)
cranial, lateral, caudal, and medial views (left to right); B) proximal view, femoral head to
the left (top), and distal view, cranial surface facing up (bottom). Abbreviation: tc,
trochanteric crest. Scale bars = 1 cm.
Forster et al. Vorona 623
giant, flightless elephant-birds (Aepyornithidae), which according to some workers (e.g.,
Rothschild, 1911; Lambrecht, 1929, 1933; Sauer and Rothe, 1972; Sauer, 1976) are represented
outside of Madagascar as well (Egypt, Algeria, India, Mongolia, Canary Islands, Turkey). Others
(e.g., Feduccia, 1980, 1996; Olson, 1985; Rasmussen et al., 1987), however, are skeptical about
these records. In any case, the biogeographic origins of the Malagasy avifauna remain enigmatic,
and have previously been interpreted largely through the relationships of modern taxa. The
affinities of most species are generally regarded to be with Africa, but a few species indicate
Asian or even Australasian connections (e.g., Rand, 1936; Dorst, 1972; Cracraft, 1973; Keith,
1980). As stressed by Walker (1978:208) with regard to the origin of the Malagasy mammalian
fauna, the “one major piece of evidence missing is... fossils of Cretaceous, Paleocene or Eocene
age.” The discovery of Vorona, Rahonavis, and other taxa in the Late Cretaceous of Madagascar
provides the first pre-Late Pleistocene fossil evidence with which to address questions
concerning the biogeographic origins of the extant and recently extinct Malagasy avifauna.
Institutional abbreviations: FMNH: Field Museum of Natural History, Chicago, IL; UA:
Université d’Antananarivo, Service de Paléontologie, Antananarivo, Madagascar.
The Maevarano Formation is the uppermost nonmarine unit of Cretaceous age in the
Mahajanga Basin and has recently been considered Maastrichtian in age (Rogers and Hartman,
1998; Rogers at al., 2000). The Maevarano Formation is divided into three distinct members:
Masarobe, Anembalemba, and Miadana (Rogers et al., 2000). The quarry at MAD 93-18, like
most of the fossil-bearing sites in the Maevarano Formation, occurs in the Anembalamba
Member. This member averages 10-15 m in thickness and is composed of two distinctive,
alternating sandstone facies (facies 1 and facies 2). Facies 1 consists of light gray to white, fine-
to coarse-grained poorly sorted sandstone with an abundant clay matrix which displays small- to
medium-scale tabular and trough cross stratification. Facies 2 consists of a massive, fine- to
coarse-grained, poorly sorted, clay-rich sandstone that is olive green in color (Rogers et al.,
2000). Specimens of Vorona described here were recovered from both the top of a facies 1 layer
and the overlying facies 2 layer.
The importance of Vorona to the Mesozoic avian record is enhanced by its
paleogeographic location in eastern Gondwana. As discerned from a wealth of geophysical data,
the Cretaceous represents the most active period in the breakup of Gondwana. The sequence and
pattern of breakup, however, is poorly tested paleontologically. The current geophysical model
for plate tectonic evolution of the western Indian Ocean holds that Madagascar has long been an
island (summarized in Storey, 1995; Krause and Hartman, 1996; Krause et al., 1997b, 1999).
With the Indian subcontinent attached to its eastern coast, Madagascar separated from Africa in
the Late Jurassic, approximately 160-150 Ma, considerably earlier than generally regarded in
previous biogeographic scenarios involving the island's avifauna (e.g., Sauer, 1972; Cracraft,
1973; Keith, 1980). Indo-Madagascar attained its current position relative to the east coast of
Africa in the Early Cretaceous, approximately 130-125 Ma, and, according to most geophysical
reconstructions, rifted from Antarcto-Australia at about the same time. Hay et al. (1999),
however, posited a lingering connection between Indo-Madagascar and western Antarctica across
the Kerguelan Plateau that lasted well in to the Late Cretaceous, possibly as late as 80 Ma.
Separation of Madagascar from the Indian subcontinent did not occur until late in the Late
Cretaceous, at approximately 88 Ma (Storey et al. 1995). Thus, it is only since the Late
Cretaceous that Africa has been the nearest major landmass to Madagascar and it appears more
likely that the Late Cretaceous terrestrial and freshwater vertebrate fauna of Madagascar was
Forster et al. Vorona 624
more similar to that of the Indian subcontinent and, more distantly, with Antarctica, Australia,
and South America, than with Africa (Krause et al., 1997b, 1999; Sampson et al., 1998).
Taxonomic Hierarchy
Aves Linnaeus, 1758
Ornithothoraces Chiappe and Calvo, 1994
Vorona Forster et al., 1996a
Vorona berivotrensis Forster et al., 1996a
HolotypeUA 8651, a distal left tibiotarsus found in articulation with a complete
Referred specimensFMNH PA 715, associated right tibiotarsus, fibula, and femur;
FMNH PA 717, left femur.
Locality and HorizonUpper Cretaceous (Maastrichtian) Maevarano Fm., Mahajanga
Basin, near the village of Berivotra, northwestern Madagascar. Specimens were collected from
quarry site MAD 93-18. Locality coordinates are on file at FMNH and UA.
DiagnosisPossesses short, blunt cnemial crest on tibiotarsus; irregular low ridge on
medial surface of proximal tibiotarsus; narrow but deep notch on proximodorsal tarsometatarsus
between metatarsals II and III; expanded vascular groove proximal to distal foramen on
The three specimens assigned to Vorona together comprise nearly complete left and right
hindlimbs. The tibiotarsus and tarsometatarsus of UA 8651 were found in direct articulation in
the lower facies 1 level. The tibiotarsus, fibula, and femur of FMNH PA 715 were loosely
articulated in the overlying facies 2 level; the fibula was lying next to and paralleling the tibia,
and the proximal portion of the femur was lying next to the proximal tibiotarsus. The shaft and
distal portion of the femur was recovered a few centimeters south of the rest of the specimen.
At the time of its original description (Forster et al., 1996a), only a small portion of the
proximal right femur (FMNH PA 715) could be assigned with confidence to Vorona (Fig. 12.3).
Since then, additional preparation revealed contacts between this femoral fragment and the shaft
and distal right femur of a then unidentified avian. This discovery has allowed us to reconstruct
the now nearly complete right femur, and to assign another specimen from the quarry, a nearly
complete left femur (FMNH PA 717), to Vorona. Additionally, a more proximal segment of the
holotype tibiotarsus (UA 8651) was recovered during preparation of quarry material.
Measurements of all limb elements are given in Table 12.1.
Place Figure 12.3 near here
Place Table 12.1 near here
Pelvic Limb
FemurThe neck of the femur is short, robust, and weakly constricted (Figs. 12.2, 12.3).
The outline of the femoral head is nearly round in proximomedial view. The flattened
proximomedial surface of the femoral head bears a broad, shallow depression for the attachment
of the capital ligament. A fossa for the capital ligament is also present in Enantiornithes and
Ornithurae, but is absent in non-avian maniraptorans, Unenlagia (Novas and Puerta, 1997),
Archaeopteryx, and Mononykus (Perle et al., 1994). There is a distinct trochanteric crest
projecting slightly above the level of the femoral head. The lateral surface of the proximal femur
FIGURE 12.3. Left femur of referred specimen FMNH PA 717 in (left to right) cranial,
lateral, caudal, and medial views. Abbreviations: fcl, fossa for capital ligament; il,
intermuscular line; t, tubercle on lateral supracondylar ridge. Scale bar = 1 cm.
Forster et al. Vorona 621
TABLE 12.1
Measurements in millimeters of specimens of Vorona berivotrensis.
PA 715 PA 717
total length 93.7 --- 94.1
craniocaudal width trochanteric crest 10.9 --- ---
greatest diameter at mid-shaft 8.4 --- 8.1
mediolateral width distal condyles 15.3 --- 15.5
length of preserved portion --- 76.0 ---
craniocaudal length proximal end --- 9.3 ---
mediolateral width proximal end --- 3.9 ---
total length --- 165.8 ---
height astragalar ascending process 33.3 32.5 ---
mediolateral width proximal end --- 11.8 ---
craniocaudal length proximal end --- 16.0 ---
mediolateral diameter at mid-shaft 5.9 6.1 ---
craniocaudal diameter at mid-shaft 7.1 7.0 ---
mediolateral width distal condyles 12.3 12.4 ---
craniocaudal width distal condyles 11.8 12.0 ---
total length 60.9 --- ---
mediolateral width proximal end 12.9 --- ---
dorsoplantar width proximal end 8.0 --- ---
mediolateral width at mid-shaft 9.0 --- ---
dorsoplantar depth at mid-shaft 4.2 --- ---
mediolateral width across trochleae 13.7 --- ---
MT II: total length 3.8 --- ---
mediolateral width trochlea 4.2 --- ---
dorsoplantar depth trochlea 4.7 --- ---
MT III: total length 61.0 --- ---
mediolateral width trochlea 5.6 --- ---
dorsoplantar depth trochlea 6.3 --- ---
MT IV: total length 58.4 --- ---
mediolateral width trochlea 3.9 --- ---
dorsoplantar depth trochlea 5.7 --- ---
MT V: total length 16.4 --- ---
length of tarsometatarsus/tibiotarsus
(UA 8651/FMNH PA 715) .37
Forster et al. Vorona 625
is slightly depressed but, unlike the condition seen in Enantiornithes, Archaeopteryx, and some
non-avian maniraptorans, it bears no evidence of a posterior trochanter.
The shaft of the femur is cranially bowed, and lacks a fourth trochanter. An
intermuscular line courses from the trochanteric crest down to the medial side of the distal femur,
crossing the cranial aspect of the femoral shaft. A caudal intermuscular line runs from the medial
condyle proximally across approximately three-fourths of the femur. A third intermuscular line
runs the length of the entire caudolateral edge of the shaft.
The distal femur is flat cranially and lacks a patellar groove. A well-developed patellar
groove is a synapomorphy of ornithurine birds (Chiappe, 1996a). On the caudal aspect, the
triangular popliteal fossa is bounded distally by an intercondylar bridge. This condition is
comparable to that of Enantiornithes, Patagopteryx, and Ornithurae. The lateral margin of the
popliteal fossa is developed into a supracondylar ridge that projects caudally beyond the level of
the medial margin, as in Enantiornithes (Chiappe and Calvo, 1994; Sanz et al., 1995; Chiappe,
1996a). Approximately 0.5 cm above the lateral condyle this ridge swells into a tubercle. This
tubercle does not occur in any known enantiornithine bird. The lateral supracondylar ridge,
along with the lateral condyle, defines the medial boundary of a weak fibular trochlea. This
trochlea, and the tibiofibular crest of the lateral condyle, appears less developed than in
TibiotarsusThe tibiotarsus is long, slender, and straight (Figs. 12.4, 12.5). The shaft is
piriform in cross-section, with an evenly rounded medial surface that narrows to the lateral
margin. The tibiotarsus has a very blunt, broad, and robust cnemial crest. This single cnemial
crest is homologous to the lateral cnemial crest of neornithines (Chiappe, 1996a). A single
cnemial crest is also present in non-avian maniraptorans, Archaeopteryx, Alvarezsauridae, and
Patagopteryx, while two distinct crests are typical of Ornithurae (Chiappe, 1996a).
Iberomesornis (Sanz and Bonaparte, 1992) is specialized in having no distinct cnemial crest,
whereas Enantiornithes (Walker, 1981) have a faint, craniomedially placed crest. The proximal
articular surface of the tibiotarsus slopes slightly caudolaterally. Except for the rather bulbous,
subcircular lateral articular facet, the tilted proximal articular surface is nearly planar. The lateral
and medial articular facets are well developed and separated caudally by a broad notch; the
medial articular facet projects slightly more caudally than the lateral one. Running down the
medial surface of the proximal one-fifth of the tibiotarsus is a low, irregular ridge not found on
any other known Mesozoic bird. For most of its length, this ridge defines the cranial boundary of
an elongate rugose area, almost certainly an area of muscle attachment. The lateral surface of the
proximal one-fourth of the tibiotarsus bears a prominent fibular crest, which projects more
laterally at its distal end. A small vascular foramen pierces the shaft caudal to the distal fibular
crest, as in neornithines.
Place Figure 12.4 near here
The calcaneum and astragalus are firmly co-ossified, but are only partially fused to the
distal tibia. A well-defined line of contact on the caudal, medial, and lateral aspects of the tibia
delimit the edges of the proximal tarsals. Although patterns of fusion clearly have an ontogenetic
component, there nevertheless appears to be a phylogenetic signal present in the co-ossification
of the proximal tarsals, as well as their incorporation into the tibia (e.g., McGowan, 1984, 1985).
The two proximal tarsals are apparently fused to each other in some non-avian maniraptorans.
For example, in juvenile specimens of the troodontid Saurornithoides there is no sign of a
separate calcaneum, implying that fusion may have occurred early in ontogeny (Currie and Peng,
1993). These elements are also fused in the troodontid Sinornithoides (Russell and Dong, 1993).
The calcaneum and astragalus are co-ossified in all known birds except Archaeopteryx
FIGURE 12.4. Referred specimen FMNH PA 715: A) right tibiotarsus
in (left to right, on left) cranial, lateral, caudal, and medial views; and
partial right fibula in (left to right, on right) lateral and medial views; B)
articulated fibula and tibiotarsus in proximal view, cranial end facing
up; C) tibiotarsus in distal view, caudal end facing up. Abbreviations:
ap, ascending process of the astragalus; cc, cnemial crest; fc, fibular
crest; ir, irregular ridge; s, suture between tibia and proximal tarsals.
Scale bars = 1 cm.Scale bars = 1 cm.
Forster et al. Vorona 626
(Wellnhofer, 1992), Iberomesornis, and Alvarezsaurus (Bonaparte, 1991; Novas, 1997). In non-
avian maniraptorans, Archaeopteryx, Alvarezsauridae, and Iberomesornis, the proximal tarsals
are not co-ossified to the tibia. However, the proximal tarsals are completely fused to the tibia in
Enantiornithes, Patagopteryx, and Ornithurae (Chiappe, 1996a).
Place Figure 12.5 near here
The astragalus, including the ascending process, is one-fifth the length of the tibia in
Vorona, a proportion similar to that in other birds and non-avian maniraptorans. The tall,
triangular, ascending process is laterally placed and nearly fused to the tibia, although a faint
suture can still be seen around its perimeter on the cranial aspect.
Martin et al. (1980) disputed the homology of the ascending process of non-avian
theropods with that of Archaeopteryx on the basis of the lateral position of the ascending process
of the latter, and its interpretation as a non-homologous structure called the pretibial bone.
Additional embryological and paleontological data have shown the proposal of Martin et al.
(1980) to be incorrect. McGowan (1985) demonstrated that the pretibial bone is indeed a
modification of the astragalar ascending process, and pointed out the occurrence of a lateralized
ascending process in several non-avian theropods (e.g., Allosaurus), as well as in ratites and
tinamous. Additionally, the morphology and position of the ascending process of Vorona, along
with that of other recently found basal birds (e.g., Mononykus, Rahonavis), strongly supports the
hypothesis that the ascending process of non-avian theropods and birds are homologous (contra
Tarsitano and Hecht, 1980; Martin et al., 1980; Martin, 1983).
The medial condyle on the distal tibiotarsus is twice the width of the lateral one in cranial
view. This condition resembles that of Patagopteryx and Enantiornithes, but contrasts with that
of Ornithurae, where the condyles are subequal in width in cranial view. A narrow, deep
intercondylar sulcus separates the condyles on their cranial aspect. This sulcus opens proximally
into a small, deep fossa; the fossa and most of the sulcus is overhung by the median edges of
both condyles. This condition also occurs in Enantiornithes and Patagopteryx. The lateral
margin of the distal tibiotarsus (calcaneum) lacks any trace of a fibular articulation.
FibulaThe proximal end of the gracile fibula is transversely compressed with a slightly
concave medial face and a convex lateral face (Fig. 12.4A, B). Although medially concave, it
does not possess the prominent medial fossa typical of non-avian maniraptorans and other
theropods (e.g., Gallimimus, Deinonychus, Allosaurus). Distally, the fibula narrows rapidly to a
slender splint. Twenty-eight millimeters down the fibula (approximately two-thirds of the way
down the fibular crest), and just proximal to the fibular spine, is a small, laterally directed
tubercle for the insertion of M. iliofibularis. The lateral orientation of this tubercle, shared with
Mononykus and Patagopteryx, has been interpreted as an intermediate condition between the
craniolateral position of the tubercle in non-avian maniraptorans, and the caudally or
caudolaterally oriented tubercle of Ornithurae (Chiappe, 1996a).
Although incomplete distally, the fibula clearly did not reach the distal end of the
tibiotarsus as it does in Archaeopteryx, Alvarezsaurus, and non-avian maniraptorans. This
derived condition is confirmed by the lack of a fibular facet on the lateral (calcaneal) condyle of
the distal tibiotarsus.
TarsometatarsusThe tarsometatarsus is approximately one-third the length of the
tibiotarsus (Fig. 12.6). Metatarsals (MT) II, III, IV, and V are preserved, and MT II, III, and IV
are completely fused except along the midshaft of MT III and IV distal to the proximolateral
foramen. This part of the tarsometatarsus is only partially fused. A lesser degree of fusion is
seen in the middle portion of their shafts: MT II and III are fused along their entire length
whereas a small gap between MT III and IV is present proximally. MT II-IV are completely co-
FIGURE 12.5. Left tibiotarsus of holotype UA 8651: A) cranial,
lateral, caudal, and medial views (left to right); B) cross section
at proximal broken end, lateral margin to the left (top); cross
section at break below fibular crest, lateral margin to left
(middle); distal view, caudal margin at top (bottom).
Abbreviations: fc, fibular crest; if, intercondylar fossa; vf,
vascular foramen. Scale bars = 1 cm.
Forster et al. Vorona 627
ossified in adults of Patagopteryx and Ornithurae, but exhibit a wide range of co-ossification
within other Mesozoic birds and non-avian maniraptorans (Chiappe, 1996a). The metatarsals are
fused only proximally in Enantiornithes (e.g., Concornis, Yungavolucris, Soroavisaurus), some
specimens of Archaeopteryx (e.g., London specimen, Solnhofen specimen), and some non-avian
theropods (e.g., Ceratosaurus, Elmisaurus, Avimimus). One enantiornithine, Avisaurus gloriae,
shows MT III and IV fused distally (Varricchio and Chiappe, 1995).
Place Figure 12.6 near here
The proximal portions of MT II-IV are coplanar, a primitive condition shared by non-
avian maniraptorans and basal birds such as Archaeopteryx, Rahonavis, Alvarezsauridae,
Iberomesornis, Enantiornithes, and Patagopteryx (Chiappe, 1996a). In proximal view, the
articular surface of the tarsometatarsus is kidney-shaped (concave dorsally), and the plantar
margin of the articular area is slightly elevated above the dorsal one. No free distal tarsals are
present despite the fact that the distal tibiotarsus and tarsometatarsus of UA 8651 were found in
articulation. We hypothesize that the distal tarsals are fused to the metatarsus and contribute to
the proximal articular surface. Metatarsal II is dorsoplantarly expanded and projects dorsally
with respect to MT III and IV. A deep, very narrow notch is present on the dorsal margin
between MT III and IV. Like most primitive birds (e.g., Archaeopteryx, Alvarezsauridae, most
Enantiornithes), the tarsometatarsus of Vorona lacks a hypotarsus and an intercondylar eminence.
The medial cotyla is transversely expanded and larger than the lateral one. It extends over the
expanded proximal surface of MT II and the small, restricted proximal surface of MT III. The
lateral cotyla is not well preserved but appears to have been circular and restricted to the
proximal surface of MT IV.
Metatarsal V is a very narrow, splintlike element that is sutured to the lateroplantar
margin of the proximal end of MT IV. Metatarsal V is slightly less than one-third the length of
MT IV. Metatarsal IV is not reduced to a noticeable degree relative to MT II and III, unlike the
condition seen in Enantiornithes (Chiappe, 1993). Aside from the grooves separating each
individual metatarsal, the shaft of the tarsometatarsus has a nearly flat dorsal surface. Plantarly,
however, it is strongly concave with a deep longitudinal fossa along most of the shaft. This
plantar fossa has MT III as its roof and is bounded by MT II and IV. A similar plantar fossa is
present in Patagopteryx and some Enantiornithes (e.g., Soroavisaurus), as well as in some non-
avian maniraptorans (e.g., Elmisaurus). The shaft of MT II is dorsoplantarly expanded and its
proximal plantar surface bears a blunt edge reminiscent of the ridge seen in Soroavisaurus. In
medial view, MT II is plantarly bowed, although less so than in Soroavisaurus (Chiappe, 1993).
There is no proximal, dorsolaterally placed tubercle on MT II (an Enantiornithes synapomorphy,
Chiappe, 1993). On the proximal end of MT III is a small, dorsally projecting tubercle. This
tubercle is situated at the level of a very weak muscular scar on the dorsolateral margin of the
proximal end of MT II. Most likely, these two features indicate the attachment area for M.
tibialis cranialis. Between the proximal ends of MT III and IV is a small, elongate
proximolateral foramen. This foramen also occurs in other primitive birds (e.g., Patagopteryx),
and in at least one non-avian maniraptoran (Elmisaurus).
Metatarsal II is slightly shorter than MT IV, which, in turn, is shorter than MT III.
Metatarsal III is more slender than MT II and, especially, IV proximally, but expands distally to
exceed the others in width. The dorsal surface of the distal one-third of MT III is laterally
excavated by a broad vascular groove. This groove ends in a broad distal foramen, which opens
distally between the trochleae of MT III and IV rather than onto the plantar surface. This distal
foramen is dorsally roofed by a bony bridge formed by projections of these two trochleae that fail
to fuse together. An elongate, shallow facet for the articulation of MT I is present on the medial
FIGURE 12.6. Left tarsometatarsus of holotype UA 8651: A) dorsal, lateral, palmar, and
medial views (left to right); B) proximal view, palmar margin up (top); cross section at
mid-shaft, dorsal margin up (middle); distal view, dorsal margin up. Abbreviations: df,
distal foramen; n, notch between MT III and IV; pf, proximolateral foramen; pfo, palmar
fossa; roman numerals refer to metatarsal number. Scale bar = 1 cm.
Forster et al. Vorona 628
surface of MT II just proximal to its trochlea. The distal location of MT I in Vorona is consistent
with the capability for perching.
The equally spaced trochleae are coplanar. The trochleae of MT II and III are square in
distal view and bear well formed ginglymi. The trochlea of MT II is significantly smaller than
that of MT III, the reverse of the condition in Enantiornithes. Proximal to each of these
trochleae, on the dorsal surface, there are small, circular fossae. Metatarsal III bears the largest
trochlea and lacks the medial plantar projection of avisaurid enantiornithines. The trochlea of
MT IV is subrectangular in distal view, with its main axis dorsoplantarly oriented. This trochlea
is non-ginglymoid, and its lateral face has a well-developed collateral fossa. No phalanges are
Although represented by incomplete specimens, the avian nature of Vorona berivotrensis
was clearly outlined by Forster et al. (1996a). In this initial article, a preliminary phylogenetic
placement was established for Vorona by scoring its preserved characters into the data matrix of
Sanz et al. (1995; Appendix 2) with minor modifications and additions. This analysis placed
Vorona in a trichotomy with Enantiornithes, and a clade that consists of Patagopteryx deferrariisi
plus Ornithurae (Forster et al., 1996a).
Due to the incompleteness of the known specimens, the position of Vorona within
primitive birds has proved difficult to refine. A reanalysis of Vorona among primitive birds is
presented elsewhere in this volume (Chiappe, Chapter 20 in this volume), in a new phylogenetic
analysis based on many more characters and taxa than that of Sanz et al. (1995). Importantly,
femoral characters for Vorona not available for the initial analysis were included in the
reanalysis. In this new analysis, Vorona forms a trichotomy with Patagopteryx and Ornithurae.
Although the relationship of Vorona to other basal avians is still not fully resolved, its
separation from the Enantiornithes is supported by several derived characters shared between
Vorona, Patagopteryx, and Ornithurae. These characters include the presence of a fossa for the
capital ligament in the head of the femur, the near complete fusion of metatarsals II-IV, and the
complete enclosure of the vascular distal foramen by metatarsal III and IV. The superficial
resemblance of Vorona and certain Enantiornithes (e.g., Soroavisaurus australis, Chiappe, 1993)
is shown to be plesiomorphic since these characters (e.g., bulbous medial condyle of tibiotarsus,
excavated plantar surface of the tarsometatarsus) are also present in the far more primitive bird
Confuciusornis sanctus (see Chiappe, Chapter 20 in this volume).
The hypothesis that Vorona lies outside Enantiornithes as a basal member of the
Ornithuromorpha (see Chiappe, Chapter 20 in this volume) reminds us that the phylogenetic
diversity of Mesozoic Gondwanan avifaunas is likely far greater than that sampled thus far. Of
particular note is the consistent phylogenetic proximity of Vorona and Patagopteryx, another
non-enantiornithine basal bird from Gondwana, in both cladistic analyses (Forster et al., 1996a;
Chiappe, Chapter 20 in this volume). Nevertheless, characters supporting a sister-taxon
relationship between Vorona and Patagopteryx have not been found yet, although future findings
may support such a relationship. Clearly, whatever the outcome, more complete material of
Vorona is necessary for a full understanding of its phylogenetic relationships.
The discovery of Vorona demonstrates conclusively that birds were present on
Madagascar during the Late Cretaceous. This occurrence represents a significant geographic
range extension for Gondwanan birds since the only previous Late Cretaceous records of avian
Forster et al. Vorona 629
skeletal material are known from the western part of Gondwana (Argentina and the Antarctic
Peninsula) and from eastern Australia. The virtual absence of Mesozoic birds from other
landmasses surrounding the western Indian Ocean, coupled with our incomplete knowledge of
morphology for Vorona (and thus its unresolved phylogenetic placement) precludes the
derivation of a strong biogeographic signal from this new record.
The current biogeographic significance of Vorona, however, derives, in large part, from
what it is not. It is not a sister-taxon to, or a basal representative of, any of the modern or
recently extinct groups of Malagasy birds (including the Aepyornithidae), all of which belong
within Neornithes. The occurrence of Vorona, as well as that of the other four non-neornithine
birds from quarry MAD93-18, hardly constitute strong and persuasive evidence that the ancestors
of modern and recently extinct groups were not present on Madagascar in the Late Cretaceous. It
is, nevertheless, the only fossil evidence currently available that bears directly on the question.
Speculation that ancestors of these groups might have been isolated on Madagascar prior to the
island’s separation from Africa is not supported by any fossil evidence.
None of this work could have been accomplished without the effort and endurance of the
1995 Madagascar field crew: R. Asher, G. Buckley, Prosper, L. Rahantarisoa, L.
Randriamiarimanana, A. Rabarison, F. Ravoavy, and C. Wall. We also thank B.
Rakotosamimanana, B. Andriamihaja, the staff of the Institute for the Conservation of Tropical
Environments, P. Wright, and S. Goodman for crucial logistical help in Madagascar. We
especially thank R. Fox for an early review of this work, and L. M. Witmer for a later review.
The specimens were prepared by V. Heisey and photographed by M. Stewart; L. Betti-Nash
drafted all the figures. We also thank the Field Museum of Natural History, Chicago, for
additional preparation and specimen assistance. This work was supported by National Science
Foundation grants EAR-9418816 and EAR-9706302 and The Dinosaur Society.
Forster et al. Vorona 630
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... In spite of a number of enantiornithine features, K. mater differs from Enantiornithes (including Cratoavis cearensis, which was found in roughly coeval beds; Carvalho et al., 2015a, b) in having a plantarly displaced metatarsal III. In Enantiornithes such as Yungavolucris brevipedalis, Avisaurus archibaldi, Soroavisaurus australis, and Gobipteryx minuta Elzȧnowski, 1974, as well as some basal ornithuromorphs such as Patagopteryx deferrariisi, Archaeorhynchus spathula, Bellulornis rectusunguis Wang, Zhou, and Zhou, 2016 and Vorona berivotrensis, the metatarsals are coplanar (Brett-Surman and Paul, 1985;Elzanowski, 1995;Chiappe, 1996Chiappe, , 2002Forster et al., 1996Forster et al., , 2002Wang, Zhou et al., 2016). In K. mater there is a slender shaft of metatarsal II, being subequal to slightly narrower to metatarsal IV, features that are widespread among non-enantiornithine basal birds. ...
... In plantar view, the tarsometatarsus of K. mater is not excavated, as in other taxa such as confuciusornithids, Enantiornithes and basal ornithuromorphs (e.g., Mystiornis cyrili, Vorona berivotrensis, Patagopteryx deferrariisi, Belluliornis rectusunguis, Jianchangornis microdonta, Schizooura lii, Yixianornis grabaui, Hongshanornis longicresta Zhou and Zhang, 2005;Forster et al., 2002;Zhou et al., 2009Zhou et al., , 2012O'Connor et al., 2014;Wang, Zhou et al., 2016) where the plantar surface of metatarsal III is flat or gently concave and limited by the medial and lateral plantar crests of metatarsal II and IV, respectively (Fig. 6). This depression must have been the area of insertion of several digital muscles, as well as of tendons of flexor digital musculature (Chiappe, 2002). ...
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The fossil record of Early Cretaceous birds in South America has been restricted to members of Enantiornithes from the Crato Formation (Aptian) of Brazil. Here we describe a new genus and species of bird discovered at Pedra Branca Mine, Nova Olinda County, Ceará State, Brazil, which adds to the avian fossil record from the Crato Formation. The specimen is represented by an isolated foot that is exposed in plantar view. A plantarly displaced metatarsal III with a well-developed hypotarsus supports its referral to Ornithuromorpha, representing the oldest member of the clade reported for Gondwana. Its unique foot conformation indicates that it may belong to an unknown ornithuromorph clade with some cursory similarities to extant flightless ratites. The presence of Early Cretaceous ornithuromorphs in Brazil indicates that the clade was widespread in Gondwana during the Mesozoic.
... Two paravians have been named from the Maevarano Fm.: Rahonavis ostromi , and the non-ornithurine avialan Vorona berivotrensis Forster et al., 1996 (see also Forster et al., 2002). A number of other mostly isolated avialan remains also have been recovered from the Maevarano Fm., including synsacra, humeri, coracoids, furculae, ulnae, radii, a carpometacarpus, a femur, tibiotarsae, and pedal elements; these specimens are fully described and illustrated in O' Connor and Forster (2010). ...
... However, scattered amongst these bones were elements belonging to turtles (isolated fragments of carapace), isolated vertebrae of the snake Madtsoia madagascariensis (see LaDuke et al., 2010), isolated teeth of the abelisaurid theropod Majungasaurus crenatissimus (see Sampson et al., 1998;Krause et al., 2007), isolated elements and teeth of the small abelisaurid theropod Masiakasaurus knopfleri (see Sampson et al., 2001;Carrano et al., 2002Carrano et al., , 2011, and a number of avialan bones. The avialan material belongs to Vorona berivotrensis (see Forster et al., 1996Forster et al., , 2002O'Connor and Forster, 2010), and at least five other unnamed taxa (O'Connor and Forster, 2010). ...
... 26A and 26B). Although the development of the femoral trochanter is poorly characterized among stem euornitheans, the minimal dorsal extent of the trochanter in Ichthyornis is similar to the condition in Patagopteryx (Chiappe, 2002), Gansus and Abitusavis (Wang et al., 2020c), but distinct from Vorona (Forster et al., 2002), Apsaravis (Clarke & Norell, 2002) Iteravis and Hesperornithes (Zinoviev, 2011;Bell & Chiappe, 2016Bell, Wu & Chiappe, 2019), in which it extends beyond the femoral head. The dorsal extension of the femoral trochanter has been suggested to have a strong correlation with the swimming capabilities of water-dwelling birds, and in particular, a short femoral trochanter at the same level as the femoral head appears to be associated with foot-propelled swimming (Raikow, 1970(Raikow, , 1985Zinoviev, 2011;Clifton, Carr & Biewener, 2018;Bell, Wu & Chiappe, 2019). ...
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Ichthyornis has long been recognized as a pivotally important fossil taxon for understanding the latest stages of the dinosaur–bird transition, but little significant new postcranial material has been brought to light since initial descriptions of partial skeletons in the 19th Century. Here, we present new information on the postcranial morphology of Ichthyornis from 40 previously undescribed specimens, providing the most complete morphological assessment of the postcranial skeleton of Ichthyornis to date. The new material includes four partially complete skeletons and numerous well-preserved isolated elements, enabling new anatomical observations such as muscle attachments previously undescribed for Mesozoic euornitheans. Among the elements that were previously unknown or poorly represented for Ichthyornis, the new specimens include an almost-complete axial series, a hypocleideum-bearing furcula, radial carpal bones, fibulae, a complete tarsometatarsus bearing a rudimentary hypotarsus, and one of the first-known nearly complete three-dimensional sterna from a Mesozoic avialan. Several pedal phalanges are preserved, revealing a remarkably enlarged pes presumably related to foot-propelled swimming. Although diagnosable as Ichthyornis, the new specimens exhibit a substantial degree of morphological variation, some of which may relate to ontogenetic changes. Phylogenetic analyses incorporating our new data and employing alternative morphological datasets recover Ichthyornis stemward of Hesperornithes and Iaceornis, in line with some recent hypotheses regarding the topology of the crownward-most portion of the avian stem group, and we establish phylogenetically-defined clade names for relevant avialan subclades to help facilitate consistent discourse in future work. The new information provided by these specimens improves our understanding of morphological evolution among the crownward-most non-neornithine avialans immediately preceding the origin of crown group birds.
... Importantly, the most primitive hesperornithiforms Enaliornithidae are also known from Eurasia (Bell and Chiappe, 2016), which even supports a Eurasian origin of the clade Ornithurae. The latter hypothesis would however imply a later (probably Maastrichtian) out-of-Eurasia dispersal of the primitive lineages, such as Patagopteryx and Vorona, which are known from South America and Madagascar, respectively (Chiappe, 2002;Forster et al., 2002). These supposed dispersals however do not seem totally unlikely given enhanced flight abilities of ornithuromorph birds in general and hypothetical ancestors of these taxa, whereas the aberrant morphologies of both Patagopteryx and Vorona do not fully exclude a possibility that their phylogenetic position would be reconsidered in future. ...
Ornithuromorph birds (the clade which includes modern avian radiation) first appeared in the Early Cretaceous in Asia and achieved a great diversity during the latest ages of the Late Cretaceous (Campanian and Maastrichtian). The evolutionary history of orithuromorphs during the first 17 MYAs of the Late Cretaceous (Cenomanian to Santonian ages) remains very poorly known, as the fossil record for this time interval is largely restricted to several isolated finds of the classic avian genus Ichthyornis in North America. Here we describe an isolated distal tibiotarsus of an evolutionary advanced bird, morphologically similar to Ichthyornis, from the middle Cenomanian of Saratov Province, European Russia. This is the first documentation of an Ichthyornis-like bird in the Old World. The find further constitutes only the second pre-Campanian record of the Late Cretaceous Ornithuromorpha in Eurasia, the second record of Cenomanian birds in Russia. This discovery shows that Ichthyornis-like birds enjoyed a wide geographical distribution as early as the beginning of the Late Cretaceous. Given that the earliest and the most primitive ornithuromorph birds are known from Asia, the new find supports a Eurasian origin for Ichthyornithidae.
... obs.), all Enantiornithes that are known in this respect (Chiappe and Walker, 2002: fig. 11.12: Lamanna et al. 2006), and Vorona (Forster et al., 2002: figs. 12.2 and 12.3), there is a single rounded lateral condyle, expanding distally, without any clear groove or crest and thus any indication of subdivision into a tibiofibular and fibular semicondyles. ...
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In the dinosaurs, the lateral condyle of the femur is subdivided into two parts, here termed semicondyles: cranial semicondyle which articulates primarily with the fibula, and caudal semicondyle which is known in the theropods as the ectocondylar tuber and articulates with the tibia. Modern birds also have two semicondyles, fibular and tibiofibular (“tibiofibular crest”), which roughly correspond in position to the non-avian theropod semicondyles. However, the basal birds have a single rounded lateral condyle which must have differentiated into two modern avian semicondyles independently of those in the non-avian theropods. I therefore propose new terms that reflect non-homogy of the semicondyles in dinosaurs and modern birds: the dinosaurian semicondyles should be referred to as cranial and caudal and the modern avian semicondyles as fibular and tiobiofibular.
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Significant evolutionary shifts in locomotor behaviour often involve comparatively subtle anatomical transitions. For dinosaurian and avian evolution, medial overhang of the proximal femur has been central to discussions. However, there is an apparent conflict with regard to the evolutionary origin of the dinosaurian femoral head, with neontological and palaeontological data suggesting seemingly incongruent hypotheses. To reconcile this, we reconstructed the evolutionary history of morphogenesis of the proximal end of the femur from early archosaurs to crown birds. Embryological comparison of living archosaurs (crocodylians and birds) suggests the acquisition of the greater overhang of the femoral head in dinosaurs results from additional growth of the proximal end in the medial-ward direction. On the other hand, the fossil record suggests that this overhang was acquired by torsion of the proximal end, which projected in a more rostral direction ancestrally. We reconcile this apparent conflict by inferring that the medial overhang of the dinosaur femoral head was initially acquired by torsion, which was then superseded by mediad growth. Details of anatomical shifts in fossil forms support this hypothesis, and their biomechanical implications are congruent with the general consensus regarding broader morpho-functional evolution on the avian stem.
This Doctoral Thesis presents an exhaustive review of the Patagonian alvarezsaurids (Dinosauria, Theropoda). It includes a detailed osteological description of specimens of Patagonykus puertai (Holotype, MCF-PVPH-37), cf. Patagonykus puertai (MCF-PVPH-38), Patagonykinae indet. (MCF-PVPH-102), Alvarezsaurus calvoi (Holotype, MUCPv-54), Achillesaurus manazzonei (Holotype, MACN-PV-RN 1116), Bonapartenykus ultimus (Holotype, MPCA 1290), and cf. Bonapartenykus ultimus (MPCN-PV 738). A phylogenetic analysis and a discussion about the taxonomic validity of the recognized species and the taxonomic assignment of the materials MCF-PVPH-38, MCF-PVPH-102 and MPCN-PV 738 are presented. Different evolutionary and paleobiological studies were carried out in order to elucidate functional and behavioral aspects. Alvarezsaurus calvoi (MUCPv-54), Achillesaurus manazzonei (MACN-PV-RN 1116), Patagonykus puertai (MCF-PVPH-37) and Bonapartenykus ultimus (MPCA 1290) are valid species due to the presence of many autapomorphies. In this sense, the hypothesis proposed by P. Makovicky and collaborators that Achillesaurus manazzonei is a junior synonym of Alvarezsaurus calvoi is rejected. Likewise, certain morphological evidence allows hypothesizing that Alvarezsaurus calvoi represents a growth stage earlier than skeletal maturity. Specimen MCF-PVPH-38 is referable as cf. Patagonykus puertai, while MCF-PVPH-102 is considered an indeterminate Patagonykinae. In turn, MPCN-PV 738 is assigned as cf. Bonapartenykus ultimus based on the little overlapping material with the Bonapartenykus ultimus holotype. The results obtained from the mineralogical characterization through the X-ray diffraction method of specimens MPCN-PV 738 and the holotype of Bonapartenykus ultimus (MPCA 1290), allow to suggest that both specimens come from the same geographical area and stratigraphic level. The phylogenetic analysis, which is based upon the matrix of Gianechini and collaborators of 2018 with the inclusion of proper characters, and the database of Xu and collaborators of 2018, recovered the South American members of Alvarezsauria, such as Alnashetri cerropoliciensis (Candeleros Formation; Cenomanian), Patagonykus puertai (Portezuelo Formation, Turonian-Coniacian), Alvarezsaurus calvoi and Achillesaurus manazzonei (Bajo de La Carpa Formation, Coniacian-Santonian), and Bonapartenykus ultimus (Allen Formation, Campanian-Maastrichtian), nesting within the family Alvarezsauridae. In this sense, the forms that come from the Bajo de La Carpa Formation (Coniacian-Santonian) are recovered at the base of the Alvarezsauridae clade, while Alnashetri cerropoliciensis nests as a non-Patagonykinae alvarezsaurid. Regarding the type specimens of Patagonykus puertai and Bonapartenykus ultimus, they are recovered as members of the Patagonykinae subclade, a group that is recovered as a sister taxon of Parvicursorinae, both nested within the Alvarezsauridae. In addition, the topology obtained allows discerning the pattern, rhythm and time of evolution of the highly strange and derived alvarezsaurian skeleton, concluding in a gradual evolution. The Bremer and Bootstrap supports of the nodes (Haplocheirus + Aorun), [Bannykus + (Tugulusaurus + Xiyunykus)], and Patagonykinae, show indices that represent very robust values for these nodes. Likewise, these values suggest that two endemic clades originated early in Asia, while one endemic clade is observed in Patagonia, i.e., Patagonykinae. The analysis of the directional trends of the Alvarezsauria clade, tested by means of a own database on body masses based on the Christiansen and Fariña method, subsequently calibrated with the group's phylogeny using the R software, shows two independent miniaturization events in the alvarezsaurid evolution, namely the former originating from the base of the Alvarezsauridae (sustained by Alvarezsaurus), and the latter within the Parvicursorinae. Analysis of the Alvarezsauria dentition reveals possible dental synapomorphies for the Alvarezsauria clade that should be tested in an integrative phylogenetic analysis. The general characterization of the forelimb and a partial reconstruction of the myology of alvarezsaurs demonstrate different configurations for Patagonykinae and Parvicursorinae. The multivariate analyzes carried out from the databases of Elissamburu and Vizcaíno, plus that of Cau and collaborators, show that the Patagonykinae would have had ranges of movements greater than those observed in Parvicursorinae, although the latter would have had a greater capacity to carry out more strenuous jobs. The morphometric analysis of the hindlimb and the use of the Snively and collaborators equations, show that the configuration of this element in Alvarezsauria is indicative of a highly cursorial lifestyle, as well as possible particular strategies for more efficient locomotion. The topology obtained in the phylogenetic analysis that was carried out in this Doctoral Thesis, allowed clarifying the ontogenetic changes observed in the ontogenetic series of the manual ungueal element II-2 within the clade Alvarezsauridae. In addition, the multivariate analysis carried out from the manual phalanx II-2 allows us to infer that alvarezsaurs could have performed functions such as hook-and-pull and piercing, where the arm would function as a single unit. The anatomy and myology of the alvarezsaurian tail show that the caudal vertebrae of alvarezsaurians exhibit a combination of derived osteological features that suggests functions unique among theropods, such as considerable dorsal and lateral movements, as well as exceptional abilities to support distal loading of their long tail without compromising stability and/or mobility.
Birds have evolved on the planet for over 150 million years and become the most speciose clade of modern vertebrates. Their biological success has been ascribed to important evolutionary novelties including feathers, powered flight, and respiratory system, some of which have a deep evolutionary history even before the origin of birds. The last two decades have witnessed a wealth of exceptionally preserved feathered non-avian dinosaurs and primitive birds, which provide the most compelling evidence supporting the hypothesis that birds are descended from theropod dinosaurs. A handful of Mesozoic bird fossils have demonstrated how birds achieved their enormous biodiversity after diverging from their theropod relatives. On basis of recent fossil discoveries, we review how these new findings add to our understanding of the early avian evolution.
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It is with immense pride that this volume is dedicated to our respected colleague David W. Krause, who is one of the world’s leading specialists on the Cretaceous System. David Krause is a Distinguished Service Professor at Stony Brook University, where he also holds appointments in the Department of Geosciences, the Department of Oral Biology and Pathology, the Program in Public Health, and the Interdepartmental Doctoral Program in Anthropological Sciences. Krause is also a Research Associate of The Field Museum of Natural History (Chicago) and the American Museum of Natural History (New York). Born in Alberta, Canada, Krause was raised on a remote cattle ranch on the western plains and began his formal education in a one-room schoolhouse together with his four brothers, one sister, and 13 other children, mostly cousins. Obtaining an education for their children was of paramount importance to his parents, perhaps because neither of them had been afforded the opportunity to finish or, in his mother’s case, even attend high school. Krause enrolled at the University of Alberta in Edmonton, and, despite initial interests in mathematics and engineering, after his freshman year he landed a summer job as a field research assistant to paleontologist Richard Fox. That experience, collecting Late Cretaceous vertebrate fossils in and around Dinosaur Provincial Park in southern Alberta, ignited a spark that momentously and permanently deflected Krause’s career trajectory toward vertebrate paleontology.
It is with immense pride that this volume is dedicated to our respected colleague David W. Krause, who is one of the world’s leading specialists on the Cretaceous System. David Krause is a Distinguished Service Professor at Stony Brook University, where he also holds appointments in the Department of Geosciences, the Department of Oral Biology and Pathology, the Program in Public Health, and the Interdepartmental Doctoral Program in Anthropological Sciences. Krause is also a Research Associate of The Field Museum of Natural History (Chicago) and the American Museum of Natural History (New York). Born in Alberta, Canada, Krause was raised on a remote cattle ranch on the western plains and began his formal education in a one-room schoolhouse together with his four brothers, one sister, and 13 other children, mostly cousins. Obtaining an education for their children was of paramount importance to his parents, perhaps because neither of them had been afforded the opportunity to finish or, in his mother’s case, even attend high school. Krause enrolled at the University of Alberta in Edmonton, and, despite initial interests in mathematics and engineering, after his freshman year he landed a summer job as a field research assistant to paleontologist Richard Fox. That experience, collecting Late Cretaceous vertebrate fossils in and around Dinosaur Provincial Park in southern Alberta, ignited a spark that momentously and permanently deflected Krause’s career trajectory toward vertebrate paleontology.
The birds of Madagascar are now well-known as a result of extensive fieldwork and long-term research carried out in la Grande Ile during recent decades. The affinities of the Malagasy avifauna have therefore been well defined; an analysis of these affinities leads to some interesting conclusions with a view to a biogeographical study of the island.
Alvarezsauridae represents a clade of bizarre birds with extremely reduced but powerful forelimbs. Twenty synapomorphic features shared by Patagonykus, Alvarezsaurus and Mononykus supports Alvarezsauridae as a monophyletic group of avialan theropods. Diagnostic characters, mainly referred to vertebral, forelimb, pelvic and hindlimb anatomy, emerge from a cladistic analysis of 74 derived features depicting Alvarezsauridae as the sister taxon of the avialian clade Ornithothoraces. Since the origin and early diversification of the Alvarezsauridae probably took place during, or prior to, the Early Cretaceous, their common presence in Patagonia and Mongolia reflects a wider geographical distribution over the world, prior to the development of major geographical barriers between Laurasia and Gondwana during Aptian to Cenomanian times.