Genus of nyctosaurid pterosaur from the Late Cretaceous
Nyctosaurus
|
|
Fossil specimen (CM 11422) of
Nyctosaurus gracilis
in the
Carnegie Museum of Natural History
|
Scientific classification
|
Domain:
|
Eukaryota
|
Kingdom:
|
Animalia
|
Phylum:
|
Chordata
|
Order:
|
†
Pterosauria
|
Suborder:
|
†
Pterodactyloidea
|
Family:
|
†
Nyctosauridae
|
Genus:
|
†
Nyctosaurus
Marsh
, 1876
|
Type species
|
†
Nyctosaurus gracilis
Marsh, 1876
|
Species
|
- †
N. gracilis
(Marsh, 1876)
- †
N. nanus
(Marsh, 1881)
- †
"N." lamegoi
Price, 1953
|
Synonyms
|
- Pteranodon
(Nyctosaurus)
(Marsh, 1876)
- Nyctodactylus
Marsh, 1881
- Pteranodon gracilis
Marsh, 1876
- Pteranodon (Nyctosaurus) gracilis
(Marsh, 1876)
- Nyctodactylus gracilis
(Marsh, 1876)
- Nyctosaurus leptodactylus
Williston
, 1903
- Pteranodon bonneri
Miller, 1972
- Pteranodon (Nyctosaurus) bonneri
(Miller, 1972)
- Nyctosaurus bonneri
(Miller, 1972)
- Pteranodon nanus
Marsh, 1881
|
Nyctosaurus
(meaning "night lizard" or "bat lizard") is a
genus
of
nyctosaurid
pterosaur
from the
Late Cretaceous
period of what is now the
Niobrara Formation
of the mid-western
United States
, which, during the time
Nyctosaurus
was alive, was covered in an extensive shallow sea. Some remains belonging to a possible
Nyctosaurus
species called
N.lamegoi
have been found in
Brazil
, making
Nyctosaurus
more diverse. The genus
Nyctosaurus
has had numerous species referred to it, though how many of these may actually be valid requires further study. At least one species possessed an extraordinarily large antler-like
cranial crest
.
[2]
Nyctosaurus
was a mid-sized pterosaur that lived along the shores of the Niobrara Formation of the United States, which back then was within a large inland sea called the
Western Interior Seaway
. It has been suggested that it would have flown similar to modern-day
soaring birds
such as
albatrosses
, which consisted of flying very long distances and rarely flapping.
[3]
The species
N. gracilis
and
N. nanus
have previously been considered as species of the closely related
Pteranodon
, back then known as
P. gracilis
and
P. nanus
, due to their similarities.
Discovery and species
[
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]
The first
Nyctosaurus
fossils were described in 1876 by
Othniel Charles Marsh
, based on fragmentary material,
holotype
YPM 1178, from the
Smoky Hill River
site in
Kansas
. Marsh referred the specimen to a species of his new genus
Pteranodon
, as
Pteranodon gracilis
.
[4]
Later that year, Marsh reclassified the species in its own genus, which he named
Nyctosaurus
, meaning "night lizard" or "bat lizard", in reference to the wing structure somewhat paralleling those of
bats
.
[5]
In 1881, Marsh incorrectly assumed the name was preoccupied and changed it into
Nyctodactylus
, which thus is now a
junior synonym
.
[6]
In 1902,
Samuel Wendell Williston
described the most complete skeleton then known (P 25026) discovered in 1901 by H. T. Martin. In 1903, Williston named a second species,
N. leptodactylus
, but this is today considered identical to
N. gracilis
.
In 1953, Brazilian paleontologist
Llewellyn Ivor Price
named a partial
humerus
, DGM 238-R found in
Brazil
,
N. lamegoi
; the specific name honours the
geologist
Alberto Ribeiro Lamego
. This species has an estimated wingspan of four metres; today, it is generally considered to be a form different from
Nyctosaurus
, but has not yet been assigned its own genus name.
[2]
[7]
[8]
In 1972, a new skeleton, FHSM VP-2148, in 1962 discovered by
George Fryer Sternberg
, was named
N. bonneri
; today, it is generally seen as identical to
N. gracilis
.
[2]
[9]
[10]
In 1978, Gregory Brown prepared the most complete
Nyctosaurus
skeleton currently known, UNSM 93000.
[11]
In 1984,
Robert Milton Schoch
renamed
Pteranodon nanus
(Marsh 1881), "the dwarf",
Nyctosaurus nanus
.
[6]
The question of this species validity is currently pending further study.
[2]
In the early 2000s, Kenneth Jenkins of
Ellis, Kansas
collected two specimens of
Nyctosaurus
, which were the first to demonstrate conclusively that not only was this species crested, but that the crest in mature specimens was very large and elaborate. The specimens were purchased by a private collector in
Austin
,
Texas
. Despite being in private hands rather than a museum collection, paleontologist Chris Bennett was able to study the specimens and gave them the manuscript reference numbers KJ1 and KJ2 (for Kenneth Jenkins). Bennett published a description of the specimens in 2003. Despite the unusual crests, the specimens were otherwise indistinguishable from other specimens of
Nyctosaurus
. However, the then-currently named species were extremely similar and Bennett declined to refer them to a specific one pending further study of the differences, or lack thereof, between species of
Nyctosaurus
.
[2]
Description
[
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]
Size and weight
[
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]
Nyctosaurus
was similar in anatomy to its close relative and contemporary,
Pteranodon
. It had relatively long wings, similar in shape to modern seabirds. However, it was much smaller overall than
Pteranodon
, with an adult wingspan of little over 2 meters (6.6 ft).
[2]
Some wingspan estimates by German paleontologist
Peter Wellnhofer
in 1991 however, reached a total of about 2.9 meters (9.5 ft), and the dubious species
"N." lamegoi
had a wingspan estimate of around 4 meters (13 ft) according to Price back in 1953.
It is estimated that
N. gracillis
was about 37.6 centimeters (1.23 ft) long and weighed 1.86 kilograms (4.1 lb).
[13]
Skull and beak
[
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]
Some skull specimens preserve a distinctively large crest, at least 55 centimeters (1.80 ft) tall in the older adults, and was relatively gigantic compared to the rest of the body, while also being over three times the length of the head. The crest is composed of two long, grooved spars, one pointed upward and the other backward, arising from a common base projecting up and back from the back of the skull. The two spars were nearly equal in length, and both were nearly as long or longer than the total length of the body. The upward-pointing crest spar was at least 42 centimeters (1.38 ft) long and the backward-pointing spar was at least 32 centimeters (1.05 ft) long.
[2]
The jaws of
Nyctosaurus
were long and extremely pointed. The jaw tips were thin and needle sharp, and are often broken off in fossil specimens, giving the appearance that one jaw is longer than the other, though in life they were probably equal in length.
[2]
Wings
[
edit
]
Nyctosaurus
had wings very similar in built to those of its relative
Pteranodon
, which have a high
aspect ratio
and low
wing loadings
. The wing structure generally resembles that of the modern-day albatross, and therefore also flew like it. Unlike the related
Pteranodon
however,
Nyctosaurus
was much smaller in size, and had a relatively shorter wingspan, though still large compared to earlier pterosaurs.
[2]
Forelimbs
[
edit
]
Like the closely related
Pteranodon
,
Nyctosaurus
also had relatively long forelimbs compared to other earlier genera. Most of the tendons of the upper arm and forearm were mineralized within, this is a unique feature only seen in nyctosaurids, another of which was the related
Muzquizopteryx
. Another distinctive feature seen in
Nyctosaurus
was that it only had three
phalanges
instead of four, as seen in other
pterodactyloids
, this trait is rarely seen in other pterosaurs, and perhaps may have been an
autapomorphy
only found in
Nyctosaurus
.
Nyctosaurus
had unusually elongated
metacarpals
which measured about 2.5 times the length of its
humerus
. Proportions such as these can only be seen in two other groups of pterosaurs: the
pteranodontids
and the
azhdarchids
. Another feature that
Nyctosaurus
had in common with
Pteranodon
was its wing fingers, which occupied about 55 percent of the whole wing.
Studies on
Nyctosaurus
anatomy have concluded that the first, second and third metacarpals have lost contact with the
carpus
, similar to pteranodontids, but unlike them,
Nyctosaurus
, and possibly other nyctosaurids, had also lost the corresponding digits except the "flight" digit.
As a result, it was likely to have impaired its movement on the ground, leading scientists to conjecture that it spent almost all of its time on the wing and rarely landed. In particular, the lack of claws with which to grip surfaces would have made climbing or clinging to cliffs and tree trunks impossible for
Nyctosaurus
.
[2]
Hindlimbs
[
edit
]
Contrary to its elongated forelimbs,
Nyctosaurus
had proportionally short hindlimbs compared to the overall body size. Analyses show that
Nyctosaurus
had the shortest hindlimbs of any pterosaur genera, in terms of hindlimb-to-body ratio, which was only about 16 percent the size of its wing.
Classification
[
edit
]
Below is a
cladogram
following Brian Andres and Timothy Myers in 2013, showing the phylogenetic placement of this genus within the clade
Pteranodontia
. Two species of
Nyctosaurus
(
N. gracilis
and
"N." lamegoi
) were included in the analysis, and were placed within the family
Nyctosauridae
, sister taxa to
Muzquizopteryx
.
[15]
In 2018, a topology by Nicholas Longrich and colleagues had made the clade
Pteranodontoidea
the more inclusive group, while Pteranodontia was restricted to only pteranodontids and nyctosaurids. In this analysis, three species of
Nyctosaurus
were included:
N. lamegoi
,
N. nanus
and
N. gracilis
; all three of which were placed as derived members of the Nyctosauridae.
[16]
[9]
Paleobiology
[
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]
Life history
[
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]
Nyctosaurus
, like its relative
Pteranodon
, appears to have grown very rapidly after hatching. Fully adult specimens are no larger than some immature specimens such as P 25026 (pictured below), indicating that
Nyctosaurus
went from hatching to adult size (with wingspans of 2 meters (6.6 ft) or more) in under a year. Some sub-adult specimens have been preserved with their skulls in nearly pristine condition, and lack any trace of a head crest, indicating that the distinctively large crest only began to develop after the first year of life. The crest may have continued to grow more elaborate as the animal aged, though no studies have examined the age of the fully adult, large-crested specimens. These individuals may have been 5 or even 10 years old at the time of their deaths.
[2]
Crest function
[
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]
Only five relatively complete
Nyctosaurus
skulls have been found. Of those, one is juvenile and does not possess a crest (specimen FMNH P 25026), and two are more mature and may show signs of having had a crest but are too badly crushed to say for sure (FHSM 2148 and CM 11422). Two specimens (KJ1 and KJ2) described in 2003, however, preserved an enormous double-pronged crest.
[2]
A few scientists had initially hypothesized that this crest, which resembles an enormous
antler
, may have supported a skin "headsail" used for stability in flight. While there is no fossil evidence for such a sail, studies have shown that a membranous attachment to the bony crest would have imparted aerodynamic advantages.
[3]
However, in the actual description of the fossils, paleontologist Christopher Bennett argued against the possibility of a membrane or soft tissue extension to the crest. Bennett noted that the edges of each prong were smooth and rounded, and showed no evidence for any soft-tissue attachment points. He also compared
Nyctosaurus
with large-crested
tapejarids
, which do preserve soft tissue extensions supported by prongs, and showed that, in those species, the attachment points were obvious, with jagged edges where the transition from bone to soft tissue occurred. Bennett concluded that the crest was most likely used solely for display, citing similar structures in modern animals.
[2]
The 2009 study by Xing and colleagues testing the aerodynamics of the giant crest with a "headsail" also tested the aerodynamics of the same crest with no sail, and found that it added no significant negative factors, so a crest with no headsail would not have hindered normal flight.
[3]
It is more likely that the crest acted mainly for display, and that any aerodynamic effects it may have had were secondary. Bennett also argued that the crest was probably not a sexually dimorphic character, as in most crested pterosaurs, including the related
Pteranodon
, both sexes are crested and it is only the size and shape of the crest that differs. The apparently non-crested
Nyctosaurus
specimens therefore probably came from sub-adults.
[2]
Wing loading and speed
[
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]
Researchers
Sankar Chatterjee
and R.J. Templin used estimates based on complete
Nyctosaurus
specimens to determine weight and total wing area, and to calculate its total wing loading. They also estimated its total available flight power based on estimated musculature. Using these calculations, they estimated the cruising speed of
Nyctosaurus gracilis
as 9.6 meters/second (34.5 kilometers/hour or 21.4 miles/hour).
[13]
Paleoecology
[
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]
All known
Nyctosaurus
fossils come from the Smoky Hill Chalk of
Kansas
, part of the
Niobrara Formation
. Specifically, they are found only within a narrow zone characterized by the abundance of
ammonite
fossils belonging to the species
Spinaptychus sternbergi
. These limestone deposits were laid down during a
marine regression
of the
Western Interior Seaway
that lasted between 85 and 84.5 million years ago. Therefore,
Nyctosaurus
was a relatively short-lived species, unlike its relative
Pteranodon
, which is found throughout almost all of the Niobrara layers into the overlying
Pierre Shale Formation
, and existed between 88 and 80.5 million years ago.
[17]
The ecosystem preserved in this zone was unique in its abundance of vertebrate life.
Nyctosaurus
shared the sky with the bird
Ichthyornis
and with
Pteranodon longiceps
, though the second Niobrara
Pteranodon
species,
P. sternbergi
, had disappeared from the fossil record by this point. In the waters of the
Western Interior Seaway
below swam
mosasaurs
such as
Clidastes
,
Ectenosaurus
,
Eonatator
,
Halisaurus
,
Platecarpus
and
Tylosaurus
, several remains of the
plesiosaurs
Dolichorhynchops
and
Polycotylus
,
cephalopods
like
Baculites
and
Tusoteuthis
, and the sea turtles such as
Ctenochelys
and
Toxochelys
were also found. Flightless diving birds such as
Parahesperornis
were also known from the fossil site, and a wide variety of fish including swordfish-like
Protosphyraena
, as well as the predatory fishes
Pachyrhizodus
,
Xiphactinus
,
Ichthyodectes
,
Gillicus
,
Leptecodon
,
Enchodus
and
Cimolichthys
, the
filter feeding
Bonnerichthys
, the
dorsal finned
Bananogmius
, and the
cartilaginous fishes
Cretolamna
,
Ptychodus
,
Rhinobatos
and
Squalicorax
were also found within the formation.
[17]
Several
dinosaur
genera were found along with
Nyctosaurus
remains, these included the
nodosaurids
Hierosaurus
and
Niobrarasaurus
, as well as the
hadrosaur
Claosaurus
.
[18]
See also
[
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]
References
[
edit
]
- ^
Hone, David; Witton, Mark; Martill, David (2018).
New Perspectives on Pterosaur Paleobiology
. London: The Geological Society. p. 213.
ISBN
978-1-78620-317-5
.
- ^
a
b
c
d
e
f
g
h
i
j
k
l
m
n
Bennett, S.C. (2003).
"New crested specimens of the Late Cretaceous pterosaur
Nyctosaurus
"
.
Palaontologische Zeitschrift
.
77
: 61?75.
doi
:
10.1007/BF03004560
.
S2CID
129438441
.
.
- ^
a
b
c
Xing, L.; Wu, J.; Lu, Y.; Lu, J.; Ji, Q. (2009).
"Aerodynamic characteristics of the crest with membrane attachment on Cretaceous pterodactyloid
Nyctosaurus
"
.
Acta Geologica Sinica
.
83
(1): 25?32.
doi
:
10.1111/j.1755-6724.2009.00003.x
.
S2CID
129700882
.
- ^
Marsh, O.C. (1876a). "Notice of a new sub-order of Pterosauria."
American Journal of Science
,
11
(3): 507?509.
- ^
Marsh, O.C. (1876b). "Principal characters of American pterodactyls."
American Journal of Science
,
12
: 479?480.
- ^
a
b
Marsh, O.C. (1881). "Note on American pterodactyls."
American Journal of Science
,
21
: 342?343.
- ^
Price, Llewellyn Ivor (1953). "A presenca de Pterosauria no Cretaceo Superior do Estado da Paraiba".
Notas Preliminares e Estudos, Divisao de Geologia e Mineralogia, Brasil
(71): 1?10.
- ^
Kellner, Alexander Wilhelm Armin (1989).
"Os repteis voadores do cretaceo brasileiro"
.
Anuario do Instituto de Geociencias
.
12
: 86?106.
doi
:
10.11137/1989_0_86-106
.
- ^
a
b
Longrich, Nicholas R.; Martill, David M.; Andres, Brian; Penny, David (2018).
"Late Maastrichtian pterosaurs from North Africa and mass extinction of Pterosauria at the Cretaceous-Paleogene boundary"
.
PLOS Biology
.
16
(3): e2001663.
doi
:
10.1371/journal.pbio.2001663
.
PMC
5849296
.
PMID
29534059
.
- ^
Eberhard Frey, Ross A. Elgin, Wolfgang Stinnesbeck, Jose Manuel Padilla-Gutierrez, Christina Ifrim, Samuel Giersch, and Arturo H. Gonzalez-Gonzalez, 2012,
"A new specimen of nyctosaurid pterosaur, cf.
Muzquizopteryx
sp. from the Late Cretaceous of northeast Mexico."
Revista Mexicana de Ciencias Geologicas
29
(1): 131?139
- ^
Brown GW (1978) Preliminary report on an articulated specimen of
Pteranodon (Nyctosaurus
)
gracilis
. Proceedings of the Nebraska Academy of Science 88: 39.
- ^
a
b
Chatterjee, S. and Templin, R.J. (2004).
Posture, Locomotion, and Paleoecology of Pterosaurs
. Geological Society of America, 64 pp.
ISBN
0-8137-2376-0
,
ISBN
978-0-8137-2376-1
- ^
Andres, B.; Myers, T. S. (2013). "Lone Star Pterosaurs".
Earth and Environmental Science Transactions of the Royal Society of Edinburgh
.
103
(3?4): 383?398.
doi
:
10.1017/S1755691013000303
.
S2CID
84617119
.
- ^
Andres, B.; Clark, J.; Xu, X. (2014).
"The Earliest Pterodactyloid and the Origin of the Group"
.
Current Biology
.
24
(9): 1011?6.
doi
:
10.1016/j.cub.2014.03.030
.
PMID
24768054
.
- ^
a
b
Carpenter, K. (2003). "Vertebrate Biostratigraphy of the Smoky Hill Chalk (Niobrara Formation) and the Sharon Springs Member (Pierre Shale)."
High-Resolution Approaches in Stratigraphic Paleontology
,
21
: 421?437.
doi
:
10.1007/978-1-4020-9053-0
- ^
K. Carpenter, D. W. Dilkes, and D. B. Weishampel. 1995. The dinosaurs of the Niobrara Chalk Formation (Upper Cretaceous, Kansas). Journal of Vertebrate Paleontology 15(2):275?297
Further reading
[
edit
]
- Witton, Mark (2013).
Pterosaurs: Natural History, Evolution, Anatomy
. Princeton University Press.
ISBN
978-0-691-15061-1
.
External links
[
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]