The Armored Dinosaurs of Mongolia

94 Pages·2008·3.77 MB·English

The Armored Dinosaurs of Mongolia
T.A. Tumanova
1987
The Joint Soviet-Mongolian Paleontological Expedition Transaction
vol. 32, 76p.
Translated by Ruth Griffith, edited by Kenneth Carpenter and T. A. Tumanova
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Editor's Comments
There are two major philosophies regarding translations, one which literally translates the
words (transcription) and the other the implied meaning. The problem with transcription is that
words, sentence structure, punctuation, grammar, etc. (i.e., everything that makes each language
unique), is often unintelligible or confusing. This is especially true from Russian to English.
Anyone who has taken a foreign language knows that a word-by-word transcription to English
seldom makes sense. To avoid this problem and to make this translation of "The Armored
Dinosaurs of Mongolia" readable, I have edited the translation by my collaborator Ruth Griffith
as I would a manuscript written by a colleague for whom American English is not a first
language. I do so on the basis that American English rules of grammar are not identical to those
of Russian. In a few places, words have been added for clarification; these are inserted in
brackets, [ ]. In addition, most Russian names for localities and formations have been
standardized to Jerzykiewicz and Russell (1991) because these names are more readily
understood among English-speakers. As parts of the translation were completed, they were
checked by Tatyana Tumanova for accuracy. The resulting translation tries to be true to the
original.
Kenneth Carpenter
Denver, 1999
Reference: Jerzykiewicz, T., and Russell, D.A., 1991, Late Mesozoic stratigraphy and vertebrates
of the Gobi Basin. Cretaceous Research 12:345-377.
[Originally, this translation was sold and the proceeds used to pay for Dr. Tumanova's
membership in the Society of Vertebrate Paleontology. Now, funds are available elsewhere, so
this important monograph is being released more broadly - Kenneth Carpenter, 2008]
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CONTENTS
Introduction ................................................................................ 1
Material ................................................................................... 3
Chapter 1
A brief history of ankylosaur studies ........................................................... 5
Chapter 2
Systematic description ....................................................................... 8
Suborder Ankylosauria ........................................................................ 8
Family Nodosauridae Marsh, 1890 .......................................................... 9
Family Ankylosauridae Brown, 1908 ......................................................... 9
Subfamily Ankylosaurinae Brown, 1908 ................................................. 11
Subfamily Shamosaurinae Tumanova, 1983 ............................................... 19
Chapter 3
Morphology ............................................................................... 22
Skull ...................................................................................... 22
Shape and external features ............................................................... 22
Cranial armor ........................................................................... 23
Structure of the Skull roof ................................................................. 27
Morphology of the Nasal Cavity ............................................................ 29
Palatal area ............................................................................. 31
Ossifications of the quadrate complex ....................................................... 31
Braincase .............................................................................. 33
Ethmosphenoidal section .............................................................. 33
Otico-occipital section ................................................................ 33
Maxilla ................................................................................ 38
Mandible .............................................................................. 41
Teeth .................................................................................. 41
Hyoid apparatus ........................................................................ 42
Muscles, glands, nerves and vessels of the head ................................................. 43
Musculature of' the head .................................................................. 43
Lateral nasal gland and Jacobson's organ ..................................................... 44
Circulatory system ....................................................................... 45
Cranial nerves .......................................................................... 46
Chapter 4
Dermal armor ............................................................................. 48
Chapter 5
Phylogeny of ankylosaurs ................................................................... 51
Chapter 6
Some morphological features of ankylosaurs and their systematic significance ...................... 55
Chapter 7
Ecology ................................................................................... 59
Chapter 8
Geological and geographical distribution of ankylosaurs ........................................ 63
Localites of the Mongolian ankylosaurs ......................................................... 67
Lower Cretaceous sites ................................................................... 67
Upper Cretaceous sites ................................................................... 68
Summary ................................................................................. 72
References ................................................................................ 72
Plate Captions ............................................................................. 81
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INTRODUCTION
The Ankylosaurs are a separate group of dinosaurs known from the Cretaceous Period and
widespread throughout practically the entire World. Ankylosaur morphology reveals their
extreme specialization, as well as primitiveness compared to the rest of the dinosaurs.
Until recently, the discoveries of these animals consisted, as a rule, of scutes and spines from
armor or of fragments of the postcranial skeleton; characteristically, cranial material was poorly
preserved. Because of this, knowledge of the group remained rather limited and descriptions were
basically of a superficial character. Only in recent years have a monograph and some separate
papers appeared in which the morphology of Mongolian (Maryańska, 1971, 1977) and North
American (Coombs, 1972a,b,c, 1979) armored dinosaurs were treated in more detail. A major
obstacle to the study of ankylosaur cranial morphology was found to be the massive overlapping
of the cranial surface by osteodermal plates which are firmly fused with the underlying bones.
In this connection, was a lucky find by the Polish Mongolian Paleontological Expedition to Bayn
Dzak (MPR) of a young specimen of Pinacosaurus grangeri (Maryańska, 1971, 1977); on the
skull sutures were still visible.
A detailed study of ankylosaur morphology and comparisons with other dinosaurs and reptiles
enable us to solve more definitely the problems of their systematic position, relationships, and
origins of both North American and Asian specimens, and allows us to raise questions concerning
dinosaur evolution as a whole. The aim of the present work is an attempt to make a detailed study
of ankylosaur morphology, especially of the skull, so it provide us with the key to clarifying the
origin and phylogeny of this independent group of animals.
Because of the poor state of previous ankylosaur morphology studies, there were still
problems concerning their origin and connection with related groups, and even about
relationships within the group.
In the present work, only the least studied specimens of ankylosaurs from Mongolia are
considered in detail, including Talarurus known almost solely by the postcranial skeleton, and
the new genus Amtosaurus, the same age as Talarurus. A revised diagnosis of the genus
Maleevus is also presented. A new Early Cretaceous genus of ankylosaurid, Shamosaurus, is also
established. The family Ankylosauridae is divided into two subfamilies, the Shamosaurinae and
the Ankylosaurinae. Shamosaurinae, the more primitive, is represented at present by only one
genus, Shamosaurus, from the Lower Cretaceous; the Ankylosaurinae includes all the rest of the
known ankylosaurids. Sauroplites, from the Lowest Cretaceous of China, possibly belongs to the
Shamosaurinae, but we can not resolve the problem definitively because its remains are
incomplete (Bohlin, 1953).
As criteria for this division [into two subfamilies], we have the following: difference in form
of the preorbital section of the skull, orientation of the orbits, relative distance of the orbits from
the occiput, and also some structures of the skull of Shamosaurus that are intermediate between
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Ankylosauridae and Nodosauridae. These include the construction of the premaxillary section
of the muzzle, the large curves anterior to the pterygoid flanges, contact of the pterygoids with
the basisphenoid, the structure of the quadrates and paroccipital process, and the circular shape
of the occipital condyle. All of these intermediate traits are obviously due to the very great age
of Shamosaurus and its proximity to the ancestry of both families.
The study of the discoveries, including some preliminary material we received, supports the
claims of W. Coombs for the extremely isolated position of the ankylosaurs within the
ornithischian dinosaurs, their peculiar morphology, and, consequently it is possible to consider
the phylogeny of ankylosaurs to some extent.
A detailed morphological study is also important for paleoecological research. Naturally, the
results of a morphological analysis must be augmented by stratigraphy, lithology, etc. Obviously,
the more a group is studied, the greater importance these [ankylosaur] specimens have for
biostratigraphy. In recent years, the remains of ankylosaurs were found in all Upper Cretaceous
strata discovered in the territory of the Mongolian Peoples Republic. This makes it possible to
consider ankylosaurs in fauna complexes for correlation of Cretaceous deposits in Mongolia and
other Asiatic regions, but also of Asia and North America (ankylosaurid remains are also found
in the territory of Kazakhstan, but due to their fragmentary state, they have not been studied at
the present).
The study of Mongolian ankylosaurs is very important for several reasons. First, they provide
clues about the evolution of groups, assuming they are representative samples. The work in recent
years by expeditions from several countries (including the Joint Soviet-Mongolian
Paleontological Expedition) has shown Mongolian ankylosaurs to be numerous and the
discoveries comparatively complete. In addition, the quality of preservation makes the Mongolian
material unique, and is perhaps better than any other specimens of these animals in the world.
The major collection [of Mongolian ankylosaurs] is in the Paleontological Institute of the
Academy of Sciences, USSR. It contains material belonging to seven genera, three of which were
established by the author. [The taxonomic description of] two genera were revised, and the
description of the other genera were expanded from more complete material.
In addition, we utilized for comparison the discoveries of the Polish-Mongolian
Paleontological Expedition; these are preserved in Warsaw in the Museum of Earth and in the
Institute of Paleobiology, and were kindly offered for study by the Polish Academy of Science.
This work was completed in the laboratory of Lower Tetrapods of the Paleontological
Institute, Academy of Sciences, USSR, under the guidance of Academician L. P. Tatarinov, to
whom the author expresses heartfelt thanks. The author is deeply grateful to A. K.
Rodzdestvensky for thesis definition and guidance in the first stages of the study.
The author sincerely thanks the coworkers in the Paleontological Institute for valuable advice.
Besides, I would like from all my heart to thank the Assistant Director of the Museum of Earth,
Dr. T. Maryańska, for her help and valuable consultations.
Drawings for the paper were completed by artists T. D. Rakova, K. P. Meshkov and V. D.
Kolganov.
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MATERIAL
Shamosaurus scutatus
3779/2 - skull with incomplete postcranial skeleton and part of the armor. Khamareen Us, Lower
Cretaceous, Dzun Bayn Formation.
?Shamosaurus
3779/1 - portion of skull, Khamareen Us, Lower Cretaceous, Dzun Bayn Formation.
?Shamosaurus
3101 - lower mandible, separate fragments. Khovboor, Lower Cretaceous.
Talarurus plicatospineus
557 - partial postcranial skeletons of 6 individuals and two fragments of skulls. Bayn Shiren,
Eastern Gobi, Upper Cretaceous, Bayn Shiren Formation. (Cenomanian - Lower Santonian
according to Barsbold, 1972).
3780/1 - incomplete skull with skull roof, part of occiput and braincase. Baynshin Tsav,
Southeast Gobi, Upper Cretaceous, Bayn Shiren Formation.
Maleevus disparoserratus
554/1-2 - fragments of right maxilla.
554/1-1 - left maxilla of specimen described by E. A. Maleev (1952b) as the holotype
Syrmosaurus disparoserratus. Shiregin Gashun, Mongolia, Upper Cretaceous, Bayn Shiren
Formation.
554/2-1 - endocranial fragment with occipital condyle.
Amtosaurus magnus
3780/2 - part of skull - endocranium. Amtgai, Upper Cretaceous, Bayn Shiren Formation.
Pinacosaurus grangeri
614 - complete postcranial skeleton of animal, described by E. A. Maleev (1952) as the holotype
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Syrmosaurus viminicaudus. Bayn Dzak, Upper Cretaceous, Djadokhta Formation, Santonian
according to Kielan-Jaworowska (1974a, b).
4043 - cranial fragments. Baga Tarjach, Upper Cretaceous.
3780/3 - skull, Shilt-Ula, Upper Cretaceous.
3144 - cranial fragments and fragments of postcranial skeleton. Alag Teg, Upper Cretaceous.
Saichania chulsenensis
3142/251 - complete skeleton with skull. Khermeen Tsav II, Upper Cretaceous, Barun Goyot
Formation.
Tarchia gigantea
3142/250 - skull with incomplete postcranial skeleton. Khermeen Tsav, Upper Cretaceous,
Nemegt Formation.
551-29 - disarticulated caudal vertebrae, metacarpals and phalanges manus, fragments of armor
plate. This specimen was described by E. A. Maleev as holotype Dyoplosaurus giganteus.
Nemegt, Upper Cretaceous, Nemegt Formation.
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Chapter 1
A BRIEF HISTORY OF ANKYLOSAUR STUDIES
Before proceeding into the history of research on the Ankylosauridae of Asia, it is necessary
to say a few words about the history of the classification of ankylosaurs as a whole. This is
necessary because the first studies of armored dinosaurs debated the validity of the group.
When the first ankylosaurid Stereocephalus (Lambe, 1902) was discovered in the Oldman
Formation in North America, ankylosaurs were placed in three families of the suborder
Stegosauria. They were united with the stegosaurs because of the armor (Marsh, 1895, 1896).
Gradually, within the suborder [Stegosauria], groups of genera stood out - the future families
of the ankylosaurs. The new family, Ankylosauridae Brown, 1908, was established on a new
genus Ankylosaurus, which was based on a cranium and an incomplete post-cranial skeleton. This
one family of ankylosaurs contained, according to modern classification (Coombs, 1978a),
Ankylosaurus and Euoplocephalus (formerly named Stereocephalus, Lambe, 1910).
For several decades, no significant changes were proposed in the systematics of ankylosaurs
as a whole, and in the Ankylosauridae in particular. Ankylosaurs were still closely linked to
stegosaurs as a different family. In 1923, F. Nopsca (1923) proposed to equalize the ranks of the
three groups of quadrupedal ornithischians: stegosaurs, ankylosaurs, and ceratopsians. They were
reduced in taxonomic rank [from individual suborders] and placed [together] in the suborder
Thyreophora.
A. Romer (1927) adopted the separation of ankylosaurs within the boundaries of the
Ornithischia and of the separation from Stegosaurs. No detailed explanation was given for his
change of Ankylosauria as a suborder, but the difference in pelvic structure was emphasized
because its unique structure did not occur among the other Ornithischians.
The differences between the armor of ankylosaurs and stegosaurs were also apparent. The
main emphasis in subsequent papers focused on the distribution of genera within the
Ankylosauria (Nopsca, 1929; Gilmore, 1930). Gilmore joined all the European genera into the
family Acanthopholidae, which corresponds to the Nodosauridae.
A. Romer (1956) retained the suborder rank of Ankylosauria and divided them into the
[families] Acanthopholidae and Nodosauridae. The first family included the primitive taxa, the
last included the most derived forms. Romer noted that the proposed scheme was provisional
because of insufficient study of the group. The suborder rank for the Ankylosauria was
maintained in "Fundamentals of Paleontology" (Maleev, 1964). The group was divided into three
families: Acanthopholidae, Nodosauridae and Syrmosauridae.
One of the recent systematic revisions of the suborder Ankylosauria was produced by W.
Coombs (1978a). He divided all Ankylosaurs into two families. The family Nodosauridae, where
he placed the family Acanthopholidae and part of the Nodosauridae, included representatives
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with remarkably narrow skulls from North America and Europe. The second family,
Ankylosauridae, included two North American genera, Ankylosaurus and Euoplocephalus, and
all Asiatic armored dinosaurs.
Asian Ankylosaurs were first mentioned in 1923 by S. Matley (1923), who described
Lametesaurus indica from the Turonian deposits of the Jabbalpur (India) region. The affiliation
of Lametesaurus with armored dinosaurs, based on the a sacrum, an ilium and tibia, turned out
to be debatable (Chakravarti, 1935). Actual ankylosaurs [from Asia] were described from China
(Wiman, 1929; Gilmore, 1933a), but their remains were too fragmentary for an detailed
identification. Thus, Pinacosaurus grangeri (Gilmore, 1933b) is considered to be the first
discovery of an Asiatic armored dinosaur; it was described from the deposits of the Upper
Cretaceous (Djadokhta Formation, Bayn Dzak) of Mongolia.
In 1935, Young Chung-Chien (1935) described another species of this genus - P. nighsiensis,
from the Cretaceous deposits of China.
A. N. Ryabinin (1938) discovered in the Cretaceous fauna of the Sary Agach area in
Kazakhstan, the remains of ankylosaurs. The fragments, which he attributed to ceratopsians
(Ryabinin, 1939), proved to be from armored dinosaurs (Maryańska, 1977).
Over a period extending from 1930 - 1931, broken fragments of poorly preserved ankylosaur
skeletons, were collected by the Swedish-Chinese Expedition in China. B. Bohlin (1953)
established three new genera and species: Sauroplites scutiger, Heishansaurus pachicephalus and
Peishansaurus philemis, and also a new genus and species, Stegosaurides excavatus, which he
assigned to Stegosauria. Because the material is so fragmentary, the validity of his taxa is
questionable. Nevertheless, E. A. Maleev (1956), A. S. Romer (1966) and R. Steel (1969)
believed that Stegosaurides excavatus belonged to the Ankylosauria. Later, the Soviet-Chinese
Paleontological Expedition (Rozhdestvenskii, 1961) added to the collection of ankylosaurs from
China. But we still hardly have any descriptive papers on ankylosaurs of China. One practically
complete skeleton and scattered remains of other specimens from Ala-Shan have up to now not
been described and are in the collections at Peking (Beijing) (Maryańska, 1977).
The phylogenetic scheme for dinosaurs presented at the II Symposium on Mesozoic
Terrestrial Ecosystems (Chao Shichin, 1981) reviewed ankylosaur phylogeny and they were
united with stegosaurs into the same suborder.
During the Mongolian Paleontological Expeditions of the USSR (1946,1949), a variety of
nearly complete ankylosaur material was collected (Maleev, 1952a, b, 1953, 1954, 1956). From
the expedition's discoveries in the Upper Cretaceous Bayn Shiren Formation, E. A. Maleev
(1952a, b, 1956) described a new genus and species Talarurus plicatospineus. The author created
a new family, Syrmosauridae (Maleev, 1952b, 1954) for the genus Syrmosaurus, with two
species: S. viminicaudes and S. disparoserratum based on the upper jaws and postcranial
skeletons. The age of the Shiregin Gashun locality [where Talarurus was collected] was initially
determined to be early Late Cretaceous (Maleev, 1954). As a result, this family [Syrmosauridae]
was placed intermediately between the stegosaurs and the ankylosaurs. In the taxonomic
classifications of that time, the new family was used (Lapparent and Lavocat, 1955; Maleev,
1964). But now, based on more complete discoveries of better preserved specimens, S.
vimicaudus is a synonymy of Pinacosaurus grangeri (Maryańska, 1971), and the family
Syrmosauridae was a synonymy of the family Ankylosauridae Brown. S. disparoserratus was to
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