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Navajodactylus boerei n. gen., n. sp. (Pterosauria,? Azhdarchidae) from the Upper Cretaceous Kirtland Formation (Upper Campanian) of New Mexico

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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 1 st 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 1 st 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 Provincial 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.
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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.
INTRODUCTION
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-
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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.
395
nate a new genus and species of pterosaur based on the former specimen,
and compare them to other North American Late Cretaceous pterosaur
remains.
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-
tersburg, Russia.
SYSTEMATIC PALEONTOLOGY
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-
5, 7D).
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;
Sullivan, 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,
D).
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.
?Navajodactylus boerei
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
Formation.
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
396
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.
397
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.
398
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.
399
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.
400
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
Deer River.”
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
(1996).
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
boerei.
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.
DISCUSSION
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.
401
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.”
SYSTEMATIC POSITION
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.
402
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.
403
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.
CONCLUSIONS
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.
ACKNOWLEDGMENTS
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
SMP specimens.
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... Ulnae are reported in the azhdarchiform species M. minor (Padian et al., 1995); the azhdarchid species Q. lawsoni (Padian, 1984a), A. philadelphiae (NHMUK PV R 9228) (Bennett, 2001a), ?Arambourgiania (FSAC-OB 203) (Longrich et al., 2018), Z. linhaiensis (Unwin and Lü, 1997), C. boreas (Hone et al., 2019), possibly M. maggii (Vullo et al., 2018), and A. lancicollis (Nesov, 1984); as well as the putative azhdarchid specimens CCMGE 1/12671 (Averianov, 2014), NZGS CD 467 (Wiffen and Molnar, 1988), SMP VP-1853 (Sullivan and Fowler, 2011), WAM 60.57 (Bennett and Long, 1991), ZIN 56/43 (Averianov et al., 2015), and ZIN 58/43 (Averianov, 2014). Antebrachial material is reported in MOR 553, but it is not specified whether this includes ulnae or radii . ...
... This tubercle appears to be present and larger in A. lancicollis (Averianov, 2010:fig. 25) and is described as a narrow patch and a muscle scar in SMP VP-1853 by Sullivan and Fowler (2011), although they label it as present on the anterior surface in their Figure 6. The rest of the anterior aspect of the ventral expansion is a convex rounded surface (convex bulbous prominence of McGowen et al., 2002), unlike the concave surface of A. lancicollis (Averianov, 2010:300), the broad groove of D. banthensis to receive the radius (Padian and Wild, 1992:72), or the longitudinal ridge reported in I. latidens (Hooley, 1913:388, pl. ...
... The proximal and shaft fragments are separated by an unknown amount of missing bone, and considering that the preserved shaft is parallel-sided and both pieces have similar widths of their broken ends, it will likely never be known. First wing phalanges are preserved in the azhdarchiform species M. minor (Padian et al., 1995); the azhdarchid species Q. lawsoni, cf. A. philadelphiae (SMNK 1286 and 1287 PAL) possibly including NHMUK PV R 9227, Z. linhaiensis (Unwin and Lü, 1997), C. boreas (Hone et al., 2019), E. langendorfensis (Vremir et al., 2013b), M. maggii (Vullo et al., 2018), and A. lancicollis (Averianov, 2010); the questionable and tentative azhdarchid Navajodactylus boerei Sullivan andFowler, 2011 (Sullivan andFowler, 2011); and the possible azhdarchid specimens KCM VP 000,120 (Averianov, 2014), ZIN PH 13/43 (Averianov, 2014), TMM 41839-2.2, TMM 41839-3.4, ...
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... Sullivan and Fowler (2011) referred two wing phalanges, TMP 1972.1.1 andTMP 1982.19.295, to Navajodactylus boerei, a medium-sized pterosaur from the upper Campanian Kirtland Formation of New Mexico, U.S.A. However, this referral is problematic because both Alberta specimens are poorly preserved and appear to lack the diagnostic characters of Navajodactylus, and even appear to differ in having an extended ridge rather than a dorsal boss on the dorsal cotyle as seen in the Navajodactylus holotype ( Sullivan and Fowler, 2011: fig. 4b) and in lacking the pneumatic foramen. ...
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Azhdarchid pterosaurs have been known since 1972 from upper Campanian deposits of Alberta, Canada. Originally represented by only very fragmentary remains tentatively assigned to the genus Quetzalcoatlus, additional material uncovered over the years has revealed that the taxonomic identity of the Alberta pterosaur material is at odds with this in the light of the growing understanding of azhdarchid diversity. Here, we describe previously undocumented pterosaur remains from Alberta and reassess previously studied material. The specimens collected from the Dinosaur Park Formation can be assigned to a new genus and species Cryodrakon boreas, gen. et sp. nov. The largest elements referable to this taxon suggest that this genus reached sizes comparable to those of other giant azhdarchids.
... In North America, azhdarchid pterosaurs have been reported from Alberta, Canada (Currie and Russell, 1982), and in the United States, from Texas (Lawson, 1975), Wyoming (Estes, 1964), New Jersey (D. Baird, pers. comm. in Bennett, 1989), Montana (Padian and Smith, 1992;McGowen et al., 2002;Henderson and Peterson, 2006), and possibly New Mexico (Sullivan and Fowler, 2011). Here we note a new North American record of these long-necked pterosaurs from the state of Tennessee, which has no previous record of pterosaur fossils (Corgan, 1976;Corgan and Breitburg, 1997). ...
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Late Cretaceous azhdarchid pterosaurs are known from fairly incomplete remains in North America. These remains have primarily been reported from continental and fluvial deposits of the western United States. Here we refer a fragmentary cervical vertebra from the Late Campanian micaceous facies of the Coon Creek Formation of Tennessee, a near-shore marine deposit, to the azhdarchid pterosaur taxon Arambourgiania philadelphiae. This specimen represents the first reported occurrence of A. philadelphiae from North America, expands the temporal range of A.philadelphiae from the Maastrichtian to the Late Campanian, is the first reported occurrence of Pterosauria from the state of Tennessee, and extends the known geographic range of the Azhdarchidae to the eastern Gulf Coastal Plain of the United States.
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Dromaeosaurids (Theropoda: Dromaeosauridae), a group of dynamic, swift predators, have a sparse fossil record, particularly at the end of the Cretaceous Period. The recently described Dineobellator notohesperus, consisting of a partial skeleton from the Upper Cretaceous (Maastrichtian) of New Mexico, is the only diagnostic dromaeosaurid to be recovered from the latest Cretaceous of the southwestern United States. Reinterpreted and newly described material include several caudal vertebrae, portions of the right radius and pubis, and an additional ungual, tentatively inferred to be from manual digit III. Unique features, particularly those of the humerus, unguals, and caudal vertebrae, distinguish D. notohesperus from other known dromaeosaurids. This material indicates different physical attributes among dromaeosaurids, such as use of the forearms, strength in the hands and feet, and mobility of the tail. Several bones in the holotype exhibit abnormal growth and are inferred to be pathologic features resulting from an injury or disease. Similar lengths of the humerus imply Dineobellator and Deinonychus were of similar size, at least regarding length and/or height, although the more gracile nature of the humerus implies Dineobellator was a more lightly built predator. A new phylogenetic analysis recovers D. notohesperus as a dromaeosaurid outside other previously known and named clades. Theropod composition of the Naashoibito Member theropod fauna is like those found in the more northern Late Cretaceous North American ecosystems. Differences in tooth morphologies among recovered theropod teeth from the Naashoibito Member also implies D. notohesperus was not the only dromaeosaurid present in its environment.
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The horned dinosaurs (Ceratopsidae) were a diverse family of herbivorous dinosaurs originating in the Late Cretaceous in western North America (Laramidia). As one of the most species-rich dinosaur groups, their diversity and distribution are important to understanding Cretaceous dinosaur evolution. Ceratopsids have previously been hypothesized to have high levels of endemism despite inhabiting a relatively small land mass with few barriers to dispersal. Here, we document a new chasmosaurine ceratopsid, Sierraceratops turneri gen. et sp. nov., from the Upper Cretaceous (latest Campanian–Maastrichtian) Hall Lake Formation of south-central New Mexico, consistent with the hypothesis that southern Laramidia supported an endemic dinosaur fauna. Sierraceratops is distinguished by its relatively short, robust, and mediolaterally compressed postorbital horns; a flattened medial ridge on the posterior end of the pterygoid; a jugal with pronounced anterior flanges; a long pyramid-shaped epijugal horncore; a D-shaped cross section of the median parietal bar; and a squamosal with a pointed tip and low episquamosal ossifications. Phylogenetic analysis recovers Sierraceratops as sister to Bravoceratops and Coahuilaceratops, part of a clade endemic to the southwestern United States and Mexico. Sierraceratops adds to the diversity and disparity of the Chasmosaurinae in the Late Cretaceous and provides additional evidence for Laramidian endemism. Together with Sierraceratops, the Hall Lake Formation dinosaur fauna suggests that the latest Cretaceous of southern Laramidia was characterized by endemic clades and distinct community structures.
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A new and articulated specimen of a pterosaur wing including upper arm, forearm, parts of the carpus and metacarpus, and a wing phalanx from Maastrichtian phosphatic deposits of Morocco are assigned to Tethydraco cf. regalis Longrich et al., 2018. The specimen comes from the village of Ouled Abdoun, close to the Oued Zem basin and its phosphatic mines (Morocco). The fossil is part of the collection of the Université Hassan II of Casablanca (ID Number FSAC CP 251). In the first part, the thesis presents a synthetic introduction about the morphology, anatomy, physiology and evolution of pterosaurs in order to offer a comprehensive framework on this fascinating group of extinct flying tetrapods. The main goal of this work is the taxonomic identification of the specimen, principally by morphological and morphometric/statistic analysis, based on the comparison with the most similar pterosaurs of the same epoch. Aspect of the humerus morphology and dimensional ratios of the wing elements suggest that T. cf. regalis is an azhdarchid rather than pteranodontid, as originally proposed. A high abundance of azhdarchid remains in the open marine setting of the Moroccan phosphates casts doubt on suggestions that Azhdarchidae were largely terrestrial pterosaurs.
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Pterosaurs were widespread during the Late Cretaceous, but their fossils are comparatively rare in terrestrial depositional environments. A large pterosaur bone from the Kaiparowits Formation (late Campanian, ~76–74 Ma) of southern Utah, USA, is tentatively identified as an ulna, although its phylogenetic placement cannot be precisely constrained beyond Pterosauria. The element measures over 36 cm in preserved maximum length, indicating a comparatively large individual with an estimated wingspan between 4.3 and 5.9 m, the largest pterosaur yet reported from the Kaiparowits Formation. This size estimate places the individual at approximately the same wingspan as the holotype for Cryodrakon boreas from the penecontemporaneous Dinosaur Park Formation of Alberta. Thus, relatively large pterosaurs occurred in terrestrial ecosystems in both the northern and southern parts of Laramidia (western North America) during the late Campanian.
A proximal process, the processus tendinis extensoris, of the first phalanx of the wing digit in pterosaurs remains unfused, even in late ontogeny. This suggests that at least some pterosaurs achieved considerable growth as fliers. This growth strategy is unlike the condition found in other active flying tetrapods.
Arambourgiania Philadelphias (ARAMBOURG 1959) from the Maastrichtian (Upper Cretaceous) of Ruseifa, Jordan, is one of the largest pterosaurs known and was an animal comparable in size to the North American pterosaur Quetzalcoatlus northropi. A recent visit to Jordan failed to locate the holotype of A. philadelphiae (ARAMBOURG), although new, but fragmentary remains from the type locality were discovered. The new remains may be referable to Arambourgiania and are clearly distinct from Quetzalcoatlus. Calculations suggest that the wing span of Arambourgiania may have reached 12 meters.
Two portions of the missing holotype cervical vertebra of Titanopteryx philadelphiae were rediscovered in the collection of the University of Jordan at Amman. No documentation was associated with the specimen, but it matches photographs and drawings in ARAMBOURG'S original papers and compares with plaster replicas made in Paris in the 1950's. A central portion of the vertebra is still missing and is presumed to be destroyed. The taxon Arambourgiania used by NESSOV & JARKOV (1989) to replace Titanopteryx is valid. Quetzalcoatlus is significantly distinct from Arambourgiania. Long-necked azhdarchid pterosaurs could not scavenge from the carcasses of large dinosaurs, nor could they feed on infaunal invertebrates, rather they were aerial piscivores or planktivores.