Sullivan et al., eds., 2011, Fossil Record 3. New Mexico Museum of Natural History and Science, Bulletin 53.
NAVAJODACTYLUS BOEREI, N. GEN., N. SP. (PTEROSAURIA, ?AZHDARCHIDAE)
FROM THE UPPER CRETACEOUS KIRTLAND FORMATION
(UPPER CAMPANIAN) OF NEW MEXICO
ROBERT M. SULLIVAN1 AND DENVER W. FOWLER2
1 Section of Paleontology and Geology, The State Museum of Pennsylvania, 300 North Street, Harrisburg, PA 17120;
2 Museum of the Rockies, Montana State University, 600 West Kagy Boulevard, Bozeman, MT 59717
Abstract—Navajodactylus boerei gen. et sp. nov. is a new ?azhdarchid pterosaur from the Upper Cretaceous
Kirtland Formation (Hunter Wash Member), San Juan Basin, New Mexico. The holotype consists of the proximal
portion of a right 1st wing phalanx with a fused extensor tendon process. Comparison to other named and unnamed
pterosaurs indicates that the morphology of the extensor tendon process can be used to differentiate pterosaur
taxa. Navajodactylus boerei is characterized by having a well-developed extensor tendon process that covers 75%
of the proximal articulation surface of the 1st wing phalanx, with a pronounced dorsal boss on the superior margin
of the dorsal cotyle, and it has a shallow, open extensor tendon process saddle. The arc of metacarpal IV is large and
occupies more than 50% of the proximal area of the dorsal cotyle on the extensor tendon process.
Navajodactylus boerei is a component of the Hunter Wash local fauna (Kirtlandian land-vertebrate age [LVA]),
which is approximately 75 Ma (late Campanian). This age date is based on the stratigraphic position of the type
locality which lies below ash 2, dated at 74.44 Ma, and above ash DEP, dated at 75.56 Ma. Navajodactylus boerei
is also identified among the pterosaur material recovered from the the Dinosaur Park Formation, Dinosaur Provin-
cial Park, Alberta, Canada. This material is late Judithian LVA and is dated approximately 76-75.3 Ma, an age
slightly older than the age of the holotype.
Campanian and Maastrichtian pterosaurs are relatively rare and
usually known from very incomplete material. Until recently only a few
of these Late Cretaceous pterosaur taxa had been named and described;
most of the reported material has been identified to family or higher
taxonomic ranks because of the incomplete nature of the specimens and
lack of diagnostic elements. In general, the Old World Campanian-
Maastrichtian pterosaurs are better known than their New World coun-
terparts, but they, too, are largely incomplete.
The European pterosaurs were largely summarized by Company
et al. (1999), but additional pterosaur material from Europe has been
reported by Buffetaut (2001) and Buffetaut et al. (2002, 2003). Outside
of Europe, Campanian-Maastrichtian pterosaur remains are known from
North Africa, Jordan, China and Russia. These include the large azhdarchid
Zhejiangopterus linainsis Cai and Wei, a taxon based on a compressed
skull and jaws, from the ?Santonian-early Campanian Tangshang Forma-
tion of Zhejiang Province, China (Cai and Wei, 1994; Unwin and Lü,
1997). A number of large azhdarchids are known from the Old World.
These include: Arambourgiania (= Titanopteryx) philadelphiae
(Arambourg), first described by Arambourg (1959), based on an elon-
gated cervical vertebra – the holotype was later lost, then later found
(Martill et al. 1998), but not before a neotype cervical vertebra was
designated and described (Frey and Martill, 1996); Phosphatodraco
mauritanicus Pereda-Suberbiola, Bardet, Jouve, Iarochè Bouya and
Amaghzaz, based on five associated cervical vertebrae (from one indi-
vidual) from the late Maastrichtian of Morocco (Pereda-Suberbiola et al.,
2003); Hatzegopteryx thambema Buffetaut, Grigorescu and Csiki, a taxon
based on a single individual consisting of skull fragments, incomplete left
humerus and unidentified fragments from the Maastrichtian of Romania
(Buffetaut et al., 2002, 2003); Aralazhdarcho bostobensis Averianov, a
taxon based on the anterior part of cervical vertebra 5-6 reported from
the Bostobe Formation (late Santonian-early Campanian) of Kazakhstan
(Averianov, 2007); and Volgadraco bogolubovi Averianov, Arkhangelesky
and Pervushov, a taxon based on anterior part of the lower jaw (symphy-
sis) and several fragmentary skeletal remains from the Rybushka Forma-
tion (early Campanian) of Russia (Averianov et al., 2008).
Fewer Campanian-Maastrichtian pterosaur skeletal remains have
been reported from North America. Some of the more important speci-
mens include fragmentary material (incomplete femur, tibia and cervical
vertebrae) from the lower Campanian Merchantville Formation, Dela-
ware attributed to the family Ornithocheiridae (Baird and Galton, 1981);
two azhdarchid pterosaurs have been reported from the Two Medicine
Formation (Campanian) of Montana; one referred to Quetzalcoatlus
northropi Lawson (a taxon known from the late Campanian-early
Maastrichtian that has not been diagnosed and arguably could be consid-
ered a nomen nudum) and the other to Montanazhdarcho minor (Lawson,
1975a, b; Padian and Smith, 1992; Padian et al., 1995; McGowen et al.,
2005). Fragmentary Campanian pterosaur material from Dinosaur Pro-
vincial Park, originally cited as coming from the “Judith River” and/or
“Oldman” formations (Russell, 1972; Currie and Russell, 1982; Currie
and Padian, 1983), are now all known to be from the Dinosaur Park
Formation (Godfrey and Currie, 2005). An incomplete azhdarchid pte-
rosaur (TMP 92.83) is the most complete specimen known from the
Dinosaur Park Formation (Currie and Jacobsen, 1995; Godfrey and Currie,
2005). Indeterminate questionable pterosaur remains have been reported
from the upper Maastrichtian Lance Formation of Wyoming (Estes,
1964). A complete global list of Mesozoic pterosaurs has been recently
published by Barrett et al. (2008).
In 2002, as part of an ongoing investigation to resample fossil
vertebrates from the Upper Cretaceous rocks of the San Juan Basin,
New Mexico, a member of our field crew, Arjan C. Boere, recovered the
first pterosaur remains to come from New Mexico. The specimen (SMP
VP-1445), preliminarily reported as the proximal end of a theropod ulna
and parts of the radius (Sullivan, 2006), has recently been re-identified as
the greater part of the proximal end of the 1st right wing phalanx (D-IV-1)
with two shaft sections. It was recovered from the lower part of the
Kirtland Formation (Hunter Wash Member) at Denver’s Blowout (SMP
locality 281) located in Ah-shi-sle-pah Wash (Ah-shi-sle-pah Wilder-
ness Study Area [WSA]), San Juan Basin, New Mexico (Fig. 1). A second
specimen, SMP VP-1853, consisting of the proximal end of a right ulna,
was discovered two years later by one of us (DF) about one mile south
of SMP locality 281, at the same stratigraphic horizon. Here we describe
these two new and rare specimens, comment on their significance, desig-
FIGURE 1. Locality map showing the location of the holotype of Navajodactylus boerei gen. et sp. nov. (SMP VP-1445) and ?right ulna (SMP VP-1853),
Ah-shi-sle-pah Wilderness Study Area, San Juan Basin, New Mexico.
nate a new genus and species of pterosaur based on the former specimen,
and compare them to other North American Late Cretaceous pterosaur
Institutional abbreviations: MOR, Museum of the Rockies,
Bozeman, Montana; SMP, The State Museum of Pennsylvania, Harris-
burg, Pennsylvania; TMP, Royal Tyrrell Museum of Palaeontology,
Drumheller, Alberta, Canada; and ZIN PH, Zoological Institute
(Paleoherpetology Collections), Russian Academy of Sciences, St. Pe-
PTEROSAURIA Kaup, 1834
PTERODACTYLOIDEA Plieninger, 1901
?AZHDARCHIDAE Nesov, 1984
Navajodactylus, n. gen.
Type and only species: Navajodactlyus boerei, sp. nov.
Distribution: Late Cretaceous of North America (Alberta, Canada
and New Mexico).
Etymology: Derived from the word “Navajo” to honor the native
people who have long resided in northwestern New Mexico, and the
common suffix “dactylus,” meaning finger, and commonly used to refer
to members of the Pterosauria.
Diagnosis: Same as for the type species.
Navajodactylus boerei, n. sp.
Holotype: SMP VP-1445. Greater portion of the 1st right wing
phalanx (D-IV-1) with partially fused extensor tendon process (Figs. 2-
Type locality: SMP locality 281 (Denver’s Blowout), Ah-shi-
sle-pah Wash, San Juan Basin, New Mexico (Fig. 1). Precise GPS coor-
dinates are available to qualified researchers.
Formation/Age: Kirtland Formation (Hunter Wash Member),
upper Campanian (Kirtlandian LVA) (Sullivan and Lucas, 2003, 2006;
Etymology: The species name honors Arjan C. Boere, who dis-
covered and collected the holotype specimen in 2002.
Diagnosis: A medium-size pterosaur (estimated wing span 3.5
meters) that differs from all other azhdarchid pterosaurs in having the
following combination of features that pertain to the extensor tendon
process: occupies 75% of the proximal articulation surface of the 1st wing
phalanx; prominent dorsal boss on the superior margin of the dorsal
cotyle; two pneumatic foramina on ventral cotyle; shallow opened ex-
tensor tendon process saddle; arc of metacarpal IV large, occupying more
than 50% of the proximal area.
Remarks: We have determined that the morphology of extensor
tendon process (= processus tendinis extensoris) is diagnostic and al-
lows for comparison with other pterosaur material. Frey and Martill
(1998) recognized that this element is a sesamoid bone that fuses to the
proximal end of the 1st wing phalanx late in ontogeny (see also Bennett,
1994). Although these two elements are fully fused in SMP VP-1445,
indicating that the specimen is an adult, the suture is still visible between
them (Fig. 4A, B and D).
Description: The holotype, SMP VP-1445 (Fig. 2), consists of
an incomplete right 1st wing phalanx (D-IV-1) with extensor tendon pro-
cess and measures 183 mm (maximum length) and two shaft sections of
the same phalanx. All three bones were found together with their ventral
sides up and what appeared as being in near articulation (Fig. 2D). At
first, the orientation and association of the bones suggests that the large
shaft section may represent the right 4th metacarpal, but due to the lack
of a tuberculum, plus the fact that the shaft appears more gracile, it is
likely to be a misplaced shaft section of the 1st wing phalanx. This
element is severely crushed for about 75% of its length and has a maxi-
mum length of 175 mm; both its distal and proximal ends are broken. We
interpret the smaller shaft section, measuring 80 mm long, as belonging to
the larger shaft. Both distal and proximal ends are also broken. We believe
it to be the most distal of the three sections of the 1st wing phalanx.
Although these shaft sections do not readily articulate with each other,
their size and shape are consistent with the length of the 1st wing phalanx,
so we consider them to be part of this element (see Fig. 2E).
The extensor tendon process is well-developed and is fused to
75% of the proximal end of the 1st wing phalanx. It measures approxi-
mately 32 mm (maximum base length) and 34 mm (maximum proximal-
distal length). In posterior view, the dorsal and ventral cotyles are sepa-
rated by a distinct ridge (Fig. 5). The dorsal cotyle (= Facies articularis
proximalis pars dorsalis of Frey and Martill, 1998) is recessed and is
more pronounced than the ventral cotyle (= Facies articularis proximalis
pars ventralis of Frey and Martill, 1998). The proximal surface of the 1st
phalanx forms the distal end of the dorsal cotyle. The ventral cotyle is
less distinct and occupies a larger area. The inner surface of the ventral
cotyle is pierced by a prominent pneumatic foramen toward the distal
end and there is a lesser foramen situated lateral and closer to the ridge
that separates the cotyles (Figs. 4B, C and 5). There is a prominent
dorsal boss forming the superior margin of the dorsal cotyle (Figs. 4B, 5).
Anterior and adjacent to the dorsal boss is a well-developed depression,
lying between the dorsal boss and the anterior boss for muscle attach-
ment (Fig. 4B). The anterior surface of the extensor tendon process
forms an angle of 44o with the long axis of the phalanx. There is a
prominent open saddle (= proximal groove of Frey and Martill, 1998)
adjacent, and proximal to, the anterior muscle attachment boss (Fig. 4B,
The proximal end of the 1st wing phalanx is nearly intact; only the
proximal posterior edge is badly eroded and broken. The proximal ven-
tral surface, adjacent to the Fossa triangularis (see Frey and Martill,
1998, fig. A), is crushed posteriorly for 43 mm. It is part of a larger area
of deformation due to crushing of the medial part of the shaft on the
ventral side (Fig. 3D). There is a foramen located on ventral surface
towards the posterior side approximately 1 cm from the suture. This
foramen lies within the crushed surface, making it difficult to examine.
Referred material: TMP 72.1.1 (Fig. 8A-B), incomplete proxi-
mal end of left 1st wing phalanx and fused extensor tendon process.
Quarry 139, Dinosaur Park Formation, Dinosaur Provincial Park, Alberta,
Canada; and TMP 82.19.295 (Fig. 8D), incomplete left 1st wing phalanx
and fused extensor tendon process. Locality no. 25, Dinosaur Park For-
mation, Dinosaur Provincial Park, Alberta, Canada.
Material: SMP VP-1853 (Fig. 6), incomplete distal portion of a
?right ulna. SMP locality 288, Ah-shi-sle-pah Wash, San Juan Basin,
New Mexico. Collected from the Hunter Wash Member of the Kirtland
Description of SMP VP-1853: This specimen, SMP VP-1853
(Fig. 6), consists of an incomplete distal portion of a ?right ulna. It
measures 132 mm long and is crushed and slightly distorted. The distal
end is expanded, the anterior surface is concave, and the posterior surface
is convex. Proximally the shaft is oval in cross-section and is crushed,
with four main fractures running parallel on each of four sides (anterior,
posterior, dorsal and ventral). Distally between the ventral and posterior
surfaces, there is a prominent ridge that extends 55 mm to the mid-
section of the shaft where it expands, forming a narrow patch (muscle
scar). The shaft is slightly concave dorsally. The walls of the bone are
very thin, measuring 1 to 2 mm thick. There are no visible foramina.
Remarks: The slightly curved shaft of SMP VP-1853 differs
from TMP 65.14.398 (Fig. 8C), an incomplete pterosaur ulna reported
by Godfrey and Currie (2005). There is presently no way to determine
whether SMP VP-1853, or for that matter, TMP 65.14.398 belong to
Navajodactylus boerei. Because SMP VP-1853 is known from the same
stratigraphic horizon and same area as the holotype, we tentatively refer
FIGURE 2. Navajodactylus boerei gen. nov., sp. nov., SMP VP-1445, greater proximal end of right wing 1st phalanx with partially fused extensor tendon
process medial and distal shaft sections. A, Right wing 1st phalanx with partially fused extensor tendon process (with cross-section). B, Medial shaft section
1st right wing phalanx. C, Incomplete distal shaft section of 1st wing phalanx. D, Line drawing of specimen as found in the field (posterior is up): 1=A,
proximal end of 1st right wing phalanx with fused extensor tendon process; 2=B, medial section of 1st right wing phalanx; 3=C, distal section of 1st right
wing phalanx. All are ventral view and proximal ends are to the left, anterior direction is down. Abbreviation: d, distal end. Bar scale = 1 cm.
FIGURE 3. Navajodactylus boerei gen. nov., sp. nov., SMP VP-1445, proximal end of right wing 1st phalanx with partially fused extensor tendon process
in A, anterior, B, dorsal, C, posterior and D, ventral views. Proximal end is up. Scale = 1 cm.
FIGURE 4. Navajodactylus boerei gen. nov., sp. nov., SMP VP-1445, proximal end of right wing 1st phalanx with partially fused extensor tendon process.
Line drawing of Fig. 3 showing key features of the proximal end, in A, anterior, B, dorsal, C, posterior and D, ventral views. Abbreviations: db, dorsal
boss; dco, dorsal cotyle; etps, extensor tendon process saddle; msc, muscle attachment on extensor tendon process; pf, pneumatic foramen; s, suture
dividing the extensor tendon process from the proximal end of the 1st wing phalanx; vco, ventral cotyle. Proximal end is up. Scale = 1 cm.
FIGURE 5. Navajodactylus boerei gen. nov., sp. nov., SMP VP-1445, close-up of proximal end of right wing 1st phalanx with partially fused extensor
tendon process. Posterior view (in stereo). Abbreviations: 1wp, proximal portion of 1st wing phalanx; cr, ridge dividing the cotyles; db, dorsal boss of
extensor tendon process; dco-p, proximal surface of dorsal cotyle on 1st wing phalanx; etp, extensor tendon process; pf, pneumatic foramen; vco-p,
proximal surface of ventral cotyle on 1st wing phalanx. Proximal end is up. Scale = 1 cm.
it to Navajodactylus boerei. We consider TMP 65.14.398 to be an inde-
terminate pterosaur. It comes from an unspecified locality cited as “Red
COMPARISONS BASED ON
THE EXTENSOR TENDON PROCESS
Because Navajodactylus boerei is a taxon diagnosed on the mor-
phology of the extensor tendon process, it is necessary to compare it to
other named taxa that are known to preserve this element. There is only
one named late Campanian pterosaur that has this element,
Montanazhdarcho minor (MOR 691). Another taxon, “Quetzalcoatlus
sp.” a species that is half the size of Q. northropi, has been reported from
the late Campanian-Maastrichtian Aguja Formation and the Maastrichtian
Javelina Formation of Texas (Kellner and Langston, 1996). Unfortu-
nately, no 1st wing phalanges, and their companion extensor tendon pro-
cesses, were reported among the material listed by Kellner and Langston
The holotype of Montanazhdarcho minor (MOR 691) consists
of an incomplete left wing (Padian et al. 1995; McGowen et al. 2002).
The proximal end of the left first wing phalanx (D-IV-1) is preserved in
articulation with the 4th metacarpal. The length of the digit, from the
proximal end of the extensor tendon process to the broken end of the 1st
wing phalanx, is 195 mm (maximum length) (McGowen et al., 2002;
RMS, pers. observ.). The extensor tendon process is indistinguishably
fused to the phalanx, further indicating that it is a mature individual (see
below). As indicated by McGowen et al. (2002), the shaft is severely
crushed at its distal end. The width of the shaft is 16 mm, indicating that
it is approximately 30% smaller than the holotype of Navajodactylus
Because the 4th metacarpal is preserved in articulation with the
extensor tendon process, it is not possible to view the posterior articula-
tion surfaces of this element. However, enough of the extensor tendon
process is visible in dorsal, ventral and anterior aspects to allow for
comparison with the holotype of Navajodactylus boerei.
The extensor tendon process is proportionally smaller in MOR
691 and not as prominent. In dorsal view, the dorsal boss is weakly
developed, represented by a narrow ridge measuring 5 mm long. The
height of the extensor tendon process is estimated at about 16 mm,
measured from the inferred extensor tendon process/1st wing phalanx
contact. The extensor tendon process saddle of MOR 691 is relatively
flat and not as pronounced as in SMP VP-1445, seen in dorsal and
ventral views (see Fig. 4B, D).
Comparisons to other pterosaur taxa further attest to the unique
morphology of the extensor tendon process. Navajodactylus boerei dif-
fers from the Early Cretaceous Brazilian pterosaur Tupuxuara
longicristatus (Kellner and Campos, 1988, fig. 3 [immediate left]) in
having a more arcuate, proximately tapered, extensor tendon process
with its base occupying and fused to 75% of the proximal end of the 1st
wing phalanx. Lü and Ji (2005b) briefly described the 1st wing phalanx
and extensor tendon process of the azhdarchid Eoazhdarcho liaoxiensis
from the Early Cretaceous of China, and noted that the fused extensor
tendon process lacked pneumatic foramina. The same authors also briefly
described the extensor tendon process of the Early Cretaceous
ornithocheirid Boreopterus cuiae noting that it was sutured but not fused
(Lü and Ji, 2005a, p. 160) with the proximal end being 20 cm [sic] wide.
The width is, no doubt, 20 mm wide, which is about half that of
Navajodactylus boerei. Moreover, in their line drawing (Lü and Ji, 2005a,
fig. 1, p. 158), the proximal end of the 1st wing phalanx, with the extensor
tendon process, does not conform to Navajodactylus. The istiodactylid
Istiodactylus sinensis has a much reduced extensor tendon process (Andres
and Ji, 2006, fig. 2, p. 72), which is dramatically different from
Navajodactylus boerei. The fused extensor tendon process on the 1st
wing phalanx of the Dsungariperus weii also differs from Navajodactylus
boerei in having a more robust, perpendicularly directed (from the axis of
the 1st wing phalanx) process (see Lim et al., 2002, fig. 1, p. 1209). Line
illustrations showing the variation in size and morphology of the exten-
sor tendon process in selected pterosaurs is presented here (Fig. 7).
These differences are considered by use to have taxonomic utility in
diagnosing species of pterosaurs.
The extensor tendon process of Montanazhdarcho minor differs
dramatically in both size and shape from that of Navajodactylus boerei.
The holotype of Montanazhdarcho minor (MOR 691) was interpreted
as being an adult based on histological analysis (Padian et al., 1995;
McGowen et al., 2002). This is noteworthy, as Monatanazhdarcho mi-
nor is considerably smaller than Navajodactylus boerei, which is clearly
an adult based on the near complete fusion of the extensor tendon pro-
cess to the 1st wing phalanx. The extensor tendon process is proportion-
ally smaller in Montanazhdarcho compared to Navajodactylus, abbrevi-
ated posteriorly and is less prong-like. Consequently, the arc of the
cotyle is smaller compared to Navajodactylus, suggesting that
Navajodactylus had a more massive metacarpal IV. Although the cotyles
of the extensor tendon process are obscured by the articulation with the
4th metacarpal in Montanazhdarcho, it is evident that this process is
proportionally smaller than that of Navajodactylus. Montanazhdarcho
minor also lacks a prominent dorsal boss, and the saddle of the extensor
tendon process is deeper compared to that of Navajodactylus boerei.
Lastly, in posterior view, the articulation surface of the dorsal cotyle is
proportionally broader and more shelf-like compared to Navajodactylus.
Two other late Campanian specimens, consisting of the 1st wing
phalanx and fused extensor tendon process, are worth noting. The first,
TMP 72.1.1 (Fig. 8A-B), is the larger of the two, and consists of an
incomplete proximal end and the greater part of the shaft. It was first
FIGURE 6. ?Navajodactylus boerei, SMP VP-1853, greater distal portion
of an incomplete ?right ulna in A, anterior and B, posterior views.
Abbreviation: ms, muscle scar. Proximal end is up. Scale = 1 cm.
identified and commented on by Russell (1972) and was later redescribed
by Godfrey and Currie (2005). TMP 72.1.1 not only agrees in size with
the holotype of Navajodactylus boerei, but also has the same morphol-
ogy with regard to the extensor tendon process and outline of both
elements. Unfortunately, the area along the margin of the dorsal cotyle,
where the dorsal boss would be, is damaged (Fig. 8B), so the dorsal boss
is missing. Although the process is broken proximally, the deep ventral
cotyle, the large arc, near central position of the ventral cotyle border,
and the prominent open saddle of the extensor tendon process, clearly
indicate it is referable to N. boerei. The trace of the suture between the 1st
wing phalanx and extensor tendon process is faint, but visible, and con-
forms to that of the holotype.
Russell (1972) noted that the maximum width of the proximal end
is 34 mm (we note here that his measurements in his table 1 were re-
versed). The holotype (SMP VP-1445) is 40 mm, measured along the
extensor tendon process/1st wing phalanx suture, so it is slightly larger
than TMP 72.1.1. Russell (1972) concluded that the wing span of the
latter was the same as the type of Dsungaripterus weii (3.5 m) which is
the same wing span we estimate for the holotype of Navajodactylus
boerei, based on relative lengths of the 1st wing phalanx to the entire wing
of Montanazhdarcho minor.
The second specimen, TMP 82.19.295 (Fig. 8D), is slightly smaller
but has more of the proximal end preserved, including the extensor ten-
don process, although it is badly eroded. Most of the diagnostic features
of the extensor tendon process are missing, although the proximal por-
tion of the dorsal and ventral cotyles occupies the same position as in the
holotype of Navajodactylus boerei and TMP 72.1.1. The trace of the
suture between the extensor tendon process and the 1st wing phalanx is
visible and conforms to that of the holotype and TMP 72.1.1. A promi-
nent foramen is located on the ventral surface towards the posterior side
approximately 1 cm from the suture. Godfrey and Currie (2005) con-
cluded that the only difference between the two were size, implying that
the individual differences are ontogenetic differences only, not taxonomic.
We tentatively assign TMP 82.19.295 to Navajodactylus boerei. We
note that although some of the Canadian material was referred to
Quetzalcoatlus sp. (Currie and Russell, 1982; Godfrey and Currie, 2005)
because it was the only large North American azhdarchid known, that
reason alone is not sufficient rationale for assigning it to this genus.
Godfrey and Currie (2005, p. 308) stated that “there may have been as
many as three species of azhdarchid (with wing spans of 2.5, 6, and 11
m) living in the region (Alberta) at that time.”
Navajodactylus boerei is questionably, and tentatively, included
in the family Azhdarchidae. Kellner (2003) reviewed and revised the
characters of Nesov (1984) used to defined the clade. Kellner (2003)
recognizes only two synapomorphies for the Azhdarchidae: 1) mid-
cervical vertebrae extremely elongated; and 2) neural spines of mid-cervi-
cal vertebrae extremely reduced or absent. Neither of these features are
known in Navajodactlyus boerei. Unwin (2003) presented additional
characters that may have diagnostic utility but, with the possible excep-
tion of “a relatively short wing finger (~ 50% total wing length),” none of
these serve to anchor Navajodactylus in the family Azhdarchidae. Com-
parison of the morphology of the extensor tendon process, to other
known azhdarchids does suggest similarities and it is on this basis that
we tentatively place it in this family.
STRATIGRAPHY, DEPOSITIONAL ENVIRONMENT AND AGE
Denver’s Blowout (SMP locality 281) is a small expanse of low-
lying, weathered badlands, made up of predominately light-to-medium
gray and tan sandy mudstones. The holotype (SMP VP-1445) 1st right
wing phalanx (consisting of three sections) was found in situ weathering
out on the surface.
In the area immediately surrounding SMP VP-1445, the same
outcrop has proven especially rich in well-preserved vertebrate fossils
(mostly fishes, turtles and dinosaurs). Specimens were typically pre-
served as isolated occurrences distributed over a rather confined area.
None of the skeletal remains showed any indication of abrasion, and they
all lacked weathered surfaces, suggesting a minimum amount of transport
before burial. Subsequent excavation at the site of the holotype (SMP
VP-1445), during the summer of 2008, did not yield more material.
The ?right ulna (SMP VP-1853) was recovered from a sandier
lithology in what has been designated SMP locality 288, which includes
the subsite “hoodoo site” of Charles H. Sternberg (Sullivan, 2006). It
was near the hoodoo site that this second specimen was discovered. The
stratigraphic interval is slightly lower than that of Denver’s Blowout
(SMP locality 281) to the northeast. As with Denver’s Blowout, a num-
ber of well-preserved fossil micro- and macro-vertebrates, representing
the same taxa (and more) have been recovered from this site.
Fassett and Steiner (1997) identified two ash beds in the upper
Fruitland Formation and lower Kirtland Formation of lower reaches of
Hunter Wash drainage: ash DEP and ash 2. 40Ar/39Ar dates for these two
ashes are75.56 Ma and 74.55 Ma, respectively (Fassett and Steiner,
1997). Navajodactylus boerei is from the lower part of the Kirtland
FIGURE 7. Line drawings of selected pterosaurs showing differences in the morphology of the extensor tendon process (in ventral view). A, Azhdarchidae
indet., ZIN PH no. 47/43, proximal end of left phalanx (image reversed) (after Averianov 2007, fig. 5d). B, Pteranodon sp., redrawn from Wellnhoffer
(1978, fig 13). C, Montanazhdarcho minor, MOR 691, holotype, (image reversed). D, Navajodactylus boerei nov. gen. nov., sp. nov., SMP VP-1445
(holotype). E, Nyctosaurus gracilis Marsh, redrawn from Wellnhoffer (1978, fig 13). Dashed lines inferred extensor tendon process/1st wing phalanx suture.
Light gray = extensor tendon process; Dark gray = 1st wing phalanx; White = 4th metacarpal (in articulation). Scale = 1 cm.
FIGURE 8. Canadian pterosaurs. A-B, Navajodactylus boerei, TMP 72.1.1, incomplete proximal end of left 1st wing phalanx and fused extensor tendon
process in A, dorsal and B, posterior views. C, cf. Navajodactylus boerei, TMP 82.19.295, incomplete left 1st wing phalanx and fused extensor tendon
process in posterior view. D, ?Azhdarchidae indet., TMP 65.14.398, distal end of left ulna in posterior view. Abbreviation: db(m), dorsal boss missing due
to breakage; see Fig. 3 for additional abbreviations. Scale = 1 cm.
Formation at Denver’s Blowout (SMP loc. 281). Based on extrapolation
to the southeast, the section exposed at Denver’s Blowout, in Ah-shi-
sle-pah Wash, lies slightly below ash 2. Thus, the stratum at Denver’s
Blowout is slightly older than 74.55 Ma and the vertebrate fossils from
there are part of the Hunter Wash local fauna. The Hunter Wash local
fauna is early Kirtlandian LVA (Kirtlandian land-vertebrate age) as de-
fined by Sullivan and Lucas (2006). The Kirtlandian LVA ranges from
75.0 MA to 72.8 Ma, an interval between the classic Judithian and
“Edmontonian” LVAs of late Campanian to early Maastrichtian time
(Sullivan and Lucas, 2006).
All the Canadian material is from the lower half of the Dinosaur
Park Formation (Brinkman, pers. comm. to RMS, 2009) which ranges
approximately 76-75.3 Ma (Eberth, 2005). The Canadian pterosaurs are
late Judithian and thus slightly older than the New Mexican material.
Navajodactylus boerei is a new genus and species of pterosaur
based on the unique morphology of the extensor tendon process of the 1st
wing phalanx. A survey of pterosaur taxa shows that this element is
distinct among each of the late Campanian-Maastrichtian genera and
thus can be used for purposes of identification and characterization.
Navajodactylus boerei is questionably considered to be an azhdarchid
pterosaur, but it does not preserve any features that would unequivo-
cally place it in the family Azhdarchidae. Two previously reported
incomplete pterosaur specimens from the Dinosaur Park Formation
(Alberta) preserve features known only to Navajodactylus boerei and
are herein referred to this taxon. Navajodactylus boerei is the first ptero-
saur known from New Mexico and is the first identified pterosaur genus
and species from Alberta. Based on the ratio of the length of the 1st wing
phalanx to overall wing length in Montanazhdarcho minor, we estimate
that Navajodactylus boerei had a wing span of at least 3.5 m. The holo-
type is an adult, based on the fusion of the extensor tendon process to
the 1st wing phalanx. Navajodactylus boerei lived in North America around
75 Ma during the Judithian-Kirtlandian LVA transition.
We thank Donald Brinkman (Royal Tyrrell Museum of
Palaeontology, Drumheller, Alberta) for the stratigraphic data for the
TMP pterosaur material and Donna Sloan for taking the pictures of the
TMP specimens. Thanks are extended to John Horner (Museum of the
Rockies) for access to the holotype of Montanazhdarcho minor (MOR
691). Spencer Lucas (New Mexico Museum of Natural History and
Science) read an earlier version of this paper and we thank him for
comments. We also thank three anonymous reviewers for their helpful
comments on an earlier version of our paper, although we do not agree,
and did not accept, all of their criticisms. We thank Michael O’Neill
(former BLM paleontologist, Albuquerque District Office) for the issu-
ance of Paleontological Resource Permit SMP-8270-RS-01-C for the
period of 31 January 2001 through 1 February 2004 that allowed us to
collect these and other paleontological specimens under their jurisdic-
tion. We are most grateful for the continued support provided by the
Bureau of Land Management. Christy White took the photos of the
Andres, B. and Ji, Q., 2006, A new species of Istiodactylus (Pterosaria,
Pterodactyloidea) from the Lower Cretaceous of Liaoning, China: Jour-
nal of Vertebrate Paleontology, v. 26, p. 70-78.
Arambourg, C., 1959, Titanopteryx philadelphiae nov. gen, nov. sp.,
ptérosaurien géant: Notes et Mémoires sur le Moyen-Orient, v. 7, p.
Averianov, A., 2007, New records of azhdarchids (Pterosauria, Azhdarchidae)
from the Late Cretaceous of Russia, Kazakstan, and Central Asia: Pale-
ontological Journal, v. 41, p. 189-197.
Averianov, A., Arkhangelsky, M.S. and Pervushov, E.M., 2008, A new Late
Cretaceous azhdarchid (Pterosauria, Azhdarchidae) from the Volga re-
gion: Paleontological Journal, v. 42, p. 61-68.
Baird, D. and Galton. P.M., 1981, Pterosaur bones from the Upper Creta-
ceous of Delaware: Journal of Vertebrate Paleontology, v. 1, p. 67-71.
Barrett, P., Butler, J.B. Edwards, N.P. and Milner, A.R., 2008, Pterosaur
distribution in time and space: an atlas: Zitteliana, v. 28, p. 61-107.
Bennett, C., 1994, Taxonomy and systematics of the Late Cretaceous
pterosaur Pteranodon (Pterosauria, Pterodactyloidea): University of
Kansas Museum of Natural, Occasional Papers, n. 169, p. 1-70.
Buffetaut, E., 2001, An azhdarchid pterosaur from the Upper Cretaceous of
Cruzy (Hérault, France): Comptes Rendus de l’Académie des sciences,
Paris, v. 333, p. 357-361.
Buffetaut, E., Grigorescu, D. and Csiki, Z., 2002, A new giant pterosaur with
a robust skull from the latest Cretaceous of Romania: Naturwissenschaften,
v 89, p. 180-184.
Buffetaut, E., Grigorescu, D. and Csiki, Z., 2003, Giant azhdarchid ptero-
saurs from the terminal Cretaceous of Transylvania (western Romania):
Geological Society of London, Special Publications 217, p. 91-104.
Cai, Z. and Wei, J., 1994, On a new pterosaur (Zhejiangpterus linhaiensis
gen. et sp. nov.) from the Upper Cretaceous of Linhai, Zhejiang, China:
Vertebrata PalAsiatica, v. 32, p. 181-194.
Company, J., Ruiz-Omeñaca, J.I. and Pereda Suberbiola, X., 1999, A long-
necked pterosaur (Pterodactyloidea, Azhdarchidae) from the Upper Cre-
taceous of Valencia, Spain: Geologie en Mijnbouw, v. 78, p. 319-333.
Currie, P.J. and Jacobsen, A.R., 1995, An azhdarchid pterosaur eaten by a
velociraptorine theropod: Canadian Journal of Earth Sciences, v. 32, p.
Currie, P.J. and Padian, K., 1983, A new pterosaur record from the Judith
River (Oldman) Formation of Alberta: Journal of Paleontology, v. 57, p.
Currie, P.J. and Russell, D.A., 1982, A giant pterosaur (Reptilia: Archosauria)
from the Judith River (Oldman) Formation of Alberta: Canadian Journal
of Earth Science, v. 19, p. 894-897.
Eberth, D.A., 2005, The Geology; in Currie, P. J. and Koppelhus, E. B., eds.,
Dinosaur Provincial Park: a spectacular ancient ecosystem revealed:
Bloomington, Indiana University Press, p. 54-82.
Estes, R., 1964, Fossil vertebrates from the Late Cretaceous Lance Forma-
tion Eastern Wyoming: University of California Publications in Geo-
logical Sciences, v. 49, p. 1-180.
Fassett, J.E. and Steiner, M.B., 1997, Precise age of C33N-C32R magnetic-
polarity reversal, San Juan Basin, New Mexico and Colorado: New Mexico
Geological Society, Guidebook 48, p. 239-247.
Frey, E. and Martill, D.M., 1996, A reappraisal of Ambourgiania (Pterosauria,
Pterodactyloidea): one of the world’s largest flying animals: Neues
Jahrbuch für Geologie und Paläontologie, Abhandlungen, v. 199, p. 221-
Frey, E., and Martill, D.M., 1998, Late ontogentic fusion of the processus
tendinis extensoris in Cretaceous pterosaurs from Brazil: Neues Jahrbuch
für Geologie und Paläontologic, Monatshefte, v. 1998, p. 587-594.
Godfrey, S.J. and Currie, P.J., 2005, Pterosaurs; in Currie, P.J. and Koppelhus,
E.B., eds., Dinosaur Provincial Park: a spectacular ancient ecosystem
revealed: Bloomington, Indiana University Press, p. 292-311.
Kaup, J.J., 1834, Versuch einer Einthielung der Säugethiere in 6 Stämme und
der Amphibien in 6 Odnungen: Isis, Jena, p. 1-315.
Kellner, A.W.A., 2003, Pterosaur phylogeny and comments on the evolu-
tionary history of the group: Geological Society of London, Special
Publications 217, p. 105-137.
Kellner, A.W.A. and Campos, D.A., 1988, Sobre un novo pterossauro com
crista sagital da Bacia do Araripe, Cretaceo Inferior do Nordeste do
Brasil: Anais da Academia Brasileira de Cièncias, v. 60, p. 459-469.
Kellner, A.W.A. and Langston, Jr., W., 1996, Cranial remains of
Quetzalcoatlus (Pterosauria, Azhdarchidae) from Late Cretaceous sedi-
ments of Big Bend National Park, Texas: Journal of Vertebrate Paleon-
tology, v. 16, p. 222-231.
Lawson, D.A., 1975a, Pterosaur from the latest Cretaceous of West Texas:
discovery of the largest flying creature: Science, v. 187, p. 947-948.
Lawson, D.A., 1975b, Could pterosaurs fly?: Science, v. 188, p. 676-677.
Lim, J.-D., Baek, K.-S. and Yang, S.Y., 2002, A new record of a pterosaur
from the Early Cretaceous of Korea: Current Science, v. 82, p. 1208-
Lü, J. and Ji, Q., 2005a, A new ornithocheirid from the Early Cretaceous of
Liaoning Province, China: Acta Geologica Sinica, v. 79, p. 157-163.
Lü, J. and Ji, Q., 2005b, New azhdarchid pterosaur from the Early Creta-
ceous of western Liaoning: Acta Geologica Sinica, v. 79, p. 301-307.
Martill, D.M., Frey, E., Sadaqah, R.M. and Khoury, H.N., 1998, Discovery
of the holotype of the giant pterosaur Titanopteryx philadelphidae
Arambourg 1959, and the status of Arambourgiana and Quetzalcoatlus:
Neues Jarbuch für Geologie und Paläontologie, Abhandlungen, v. 207, p.
McGowen, M.R., Padian, K., de Sosa, M.A. and Harmon, R.J., 2002, De-
scription of Montanazhdarcho minor, an azhdarchid pterosaur from the
Two Medicine Formation (Campanian) of Montana: PaleoBios, v. 22,
Nesov, L.A., 1984, Pterosaurs and birds of the Late Cretaceous of Central
Asia: Paleontological Journal, n. 1, p. 47-57. [in Russian]
Padian, K., de Ricqlès, A.J. and Horner, J.R., 1995, Bone histology deter-
mines identification of a new fossil taxon of pterosaur (Reptilia:
Archosauria): Comptes Rendus des l’Académie des Sciences, Paris, v.
320, p. 77-84.
Padian, K. and Smith, M., 1992, New light on Late Cretaceous pterosaur
material from Montana: Journal of Vertebrate Paleontology, v. 12, p.
Pereda-Suberiola, X., Bardet, N., Jouve, S., Iaronchène, M., Bouya, B. and
Amaghzaz, M., 2003, A new azhdarchid pterosaur from the Late Creta-
ceous phosphates of Morocco: Geological Society of London, Special
Publications 217, p. 79-90.
Plieninger, F., 1901, Beiträge zur Kenntnis der Flugsaurier: Paläontographica,
v. 48, p. 65-90.
Russell, D.A., 1972, A pterosaur from the Oldman Formation (Cretaceous)
of Alberta: Canadian Journal of Earth Sciences, v. 9, p. 1338-1340.
Sullivan, R.M., 2006, Ah-shi-sle-pah Wilderness Study Area (San Juan Ba-
sin, New Mexico): a paleontological (and historical) treasure and re-
source: New Mexico Museum of Natural History and Science, Bulletin
34, p. 169-174.
Sullivan, R.M. and Lucas, S.G., 2003, The Kirtlandian, a new land-verte-
brate “age” for the Late Cretaceous of western North America: New
Mexico Geological Society, Guidebook 54, p. 369-377.
Sullivan, R.M. and Lucas, S.G., 2006, The Kirtlandian land-vertebrate “age”-
faunal composition, temporal position and biostratigraphic correlation
in the nonmarine Upper Cretaceous of western North America: New
Mexico Museum of Natural History and Science, Bulletin 35, p. 7-29.
Unwin, D.M., 2003, On the phylogeny and evolutionary history of ptero-
saurs: Geological Society of London, Special Publications 217, p. 91-
Unwin, D.M. and Lü, J., 1997, On Zhejiangpterus linhaiensis and the rela-
tionships of the pterodactyloid pterosaurs: Historical Biology, v. 12, p.
Wellnhofer, P., 1978, Pterosauria; in Wellnhofer, P., ed., Handbuch der
Paläoherpetologie: Stuttgart, Gustav Fisher Verlag, Teil 19, 82 p.