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Giant Mosasaurus hoffmanni (Squamata, Mosasauridae) from the Late Cretaceous (Maastrichtian) of Penza, Russia

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This study provides a morphological description of the fragmentary skull of a mosasaur discovered in 1927 in the Upper Cretaceous (Maastrichtian) deposits in the city of Penza (Russia). Some bones from the original material had been lost since their discovery; their description is based on plaster casts. The Penza mosasaur displays characteristic features of Mosasaurus hoffmanni such as the posterior carina that shifts from a somewhat lateral position in the anterior teeth to a posterior position further along the tooth row, a frontal with convex lateral margins, and a powerfully built dentary. This is the first unequivocal record of this taxon from Russia. M. hoffmanni from the Penza is one of the largest mosasaurs ever known with an overall length of the body about 17 m. Приведено детальное морфологическое описание фрагментарного черепа мозазавра, найденного в 1927 г. в верхнемеловых отложениях (маастрихт) г. Пенза, Россия. Часть оригинальных костей была впоследствии утрачена; их описание выполнено по сохранившимся гипсовым слепкам. На основании изменения положе- ния зубной карины от передних к задним зубам, лобной кости с выгнутыми боковыми сторонами и массив- ных зубных костей пензенская особь отнесена к Mosasaurus hoffmanni. Это первая достоверная находка дан- ного вида на территории России. Мозазавр из Пензы был одним из крупнейших представителей семейства, с длиной тела достигавшей не менее 17 м.
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Proceedings of the Zoological Institute RAS
Vol. 318, No. 2, 2014, рр. 148–167
УДК 568.113.3
GIANT MOSASAURUS HOFFMANNI (SQUAMATA, MOSASAURIDAE)
FROM THE LATE CRETACEOUS (MAASTRICHTIAN) OF PENZA, RUSSIA
D.V. Grigoriev
Saint Petersburg State University, Universitetskaya Emb. 7-9, 199034 Saint Petersburg, Russia;
e-mail: grigoriev_dmitry@mail.ru
ABSTRACT
This study provides a morphological description of the fragmentary skull of a mosasaur discovered in 1927 in the
Upper Cretaceous (Maastrichtian) deposits in the city of Penza (Russia). Some bones from the original material
had been lost since their discovery; their description is based on plaster casts. The Penza mosasaur displays
characteristic features of Mosasaurus hoffmanni such as the posterior carina that shifts from a somewhat lateral
position in the anterior teeth to a posterior position further along the tooth row, a frontal with convex lateral
margins, and a powerfully built dentary. This is the first unequivocal record of this taxon from Russia. M. hoffmanni
from the Penza is one of the largest mosasaurs ever known with an overall length of the body about 17 m.
Key words: Maastrichtian, Cretaceous, Penza, Mosasaurus hoffmanni, Mosasauridae
ГИГАНТСКИЙ MOSASAURUS HOFFMANNI (SQUAMATA, MOSASAURIDAE)
ИЗ ПОЗДНЕГО МЕЛА (МААСТРИХТА) ПЕНЗЫ, РОССИЯ
Д.В. Григорьев
Санкт-Петербургский Государственный Университет, Университетская наб. 7-9, 199034 Санкт-Петербург,
Россия; e-mail: grigoriev_dmitry@mail.ru
РЕЗЮМЕ
Приведено детальное морфологическое описание фрагментарного черепа мозазавра, найденного в 1927 г. в
верхнемеловых отложениях (маастрихт) г. Пенза, Россия. Часть оригинальных костей была впоследствии
утрачена; их описание выполнено по сохранившимся гипсовым слепкам. На основании изменения положе-
ния зубной карины от передних к задним зубам, лобной кости с выгнутыми боковыми сторонами и массив-
ных зубных костей пензенская особь отнесена к Mosasaurus hoffmanni. Это первая достоверная находка дан-
ного вида на территории России. Мозазавр из Пензы был одним из крупнейших представителей семейства,
с длиной тела достигавшей не менее 17 м.
Ключевые слова: маастрихт, мел, Пенза, Mosasaurus hoffmanni, Mosasauridae
INTRODUCTION
In the Russian territory and adjacent countries,
mosasaurs are predominantly known from fragmen-
tary specimens, predominantly isolated bones. More
or less complete mosasaur skeletons are extremely
rare. Such findings include a partial skeleton of Prog-
nathodon lutugini Yakovlev, 1901 from the Campanian
deposits in East Ukraine (Yakovlev 1905; Grigoriev
2013); a partial strongly deformed skeleton from the
Maastrichtian locality Rasstrigin (the right-bank
part of the Volgograd Region) (Lavrentiev 1930;
Yarkov 1993), lost during World War II; a partial
skeleton from the Maastrichtian locality Sergievka
Mosasaurus hoffmanni from the Late Cretaceous of Penza 149
(the right-bank part of the Saratov Region), which
has been defined by Bayarunas (1914) as a Mosasau-
rus sp. and which was severely damaged during a fire;
and a partial skeleton from the early Maastrichtian
site Nevezhkino-1 (Saratov Region), which has also
been damaged (Pervushov et al. 1999).
One of the most complete findings, which has
been preserved till our time almost undamaged, is a
mosasaur skull found in Penza (Fig. 1). This skull is
remarkable because of its large size and for the his-
torical circumstances of its discovery.
In 1927, political exile, the socialist revolutionary
M.A. Vedenyapin found the bones of a large marine
reptile at the outskirts of Penza in a ravine where Red
Army soldiers trained in machine gun shooting. Exca-
vations were started at the site of Vedenyapin’s find-
ing. The entire population of Penza soon began speak-
ing about the excavations. In a church, a preacher
gave a sermon that these were the bones of the animal
that did not go on Noah’s Ark, and many interested
people would often crowd around the excavations.
Vedenyapin would lecture on the geological past of
Penza. According to Vedenyapin, there were 10s of
thousands of people one day. There were thefts of the
findings, after which a militiaman was appointed to
guard the excavation site. When more bones were sto-
len at night, a Red Army patrol was sent to carry out
day-and-night security. The works were performed
quickly because of rains, which could cause landslides
on the slope. Lower jaw bones, scapula, vertebrae, and
ribs were found during the excavations. To ensure bet-
ter preservation of the found material, it was placed in
boxes together with the matrix and sent to the Saint
Petersburg Geological Committee (Archive of the
Penza Regional Museum; Arkhangelsky et al. 2012).
According to the A.N. Ryabinin’s entry in the
inventory book of Chernyshev’s Central Museum
of Geological Exploration the bones were assigned
to Mosasaurus giganteus Sömmerring, 1816. N.P
.
Stepanov mounted the skull, after which it was ex-
hibited in Chernyshev’s Central Museum of Geologi-
cal Exploration, Saint Petersburg (Fig. 2). An exact
plaster copy was sent to the Penza Regional Museum.
Unfortunately, the skull exposed in Saint Petersburg
suffered the same fate as some of the bones from the
excavations: all small and unsecured bones and teeth
were stolen by visitors of the museum. The skull has
been covered with a bell glass only relatively recently
(oral communication from the museum staff T.V. Vi-
nogradova and N.M. Kadlets).
It is necessary to note that some mosasaur remains
were found at the same site before Vedenyapin’s find-
ing. In 1925, the right part of a lower jaw with teeth,
apparently a caudal vertebra with processes, quad-
rate, and several teeth were found at the same site.
From photos, this material was assigned to Mosasau-
rus giganteus or Mosasaurus camperi by Tsaregradskii
(1926). Earlier, in 1918, during digging in a cellar in
Penza (at Dvoryanskaya street, presently Krasnaya
street), 11 mosasaur vertebrae were found. All of
the found materials were transferred to the Penza
Regional Museum but were later lost (Archive of the
Penza Regional Museum).
Institutional abbreviations. CCMGE – Cherny-
shev’s Central Museum of Geological Exploration,
Saint-Petersburg, Russia; IRSNB – Institut Royal
des Sciences Naturelles de Belgique, Brussels, Bel-
gium; PRM – Penza Regional Museum, Penza, Rus-
sia; TMP – Royal Tyrrell Museum of Palaeontology,
Drumheller, Alberta, Canada.
MATERIAL AND METHODS
The original skull of the Penza specimen
(CCMGE 10/2469) is mounted in the exhibition
hall of Chernyshev’s Central Museum of Geological
Exploration in Saint Petersburg (Figs 2, 3, 5A, B).
An unassembled plaster copy of the same specimen
(PRM 2546) is exhibited in the Penza Regional
Museum. During the mounting of the original skel-
eton by N.P. Stepanov, the bones were covered with
a very thick layer of polyvinyl butyral (PVB), and
it is therefore very difficult or sometimes impossible
to define the contacts between certain bones on the
original material. Because the mosasaur skull is ex-
posed in the museum, it was impossible to dissolve
the PVB and study some bones in detail due to their
rigid attachment to the frame. Unlike the original
material, in most cases, it is possible to trace these
contacts on plaster casts. In addition, the original
material was damaged by museum visitors. Thus, all
the original teeth from the mandibles were stolen (the
plaster casts of the teeth on the original mandibles
do not correspond to the real teeth that were set in
their places because they were made after the theft,
unlike the Penza casts). The right angular-surangu-
lar-coronoid-articular-prearticular unit was heavily
damaged on the edges, and the left angular, parietals,
left postorbitofrontal, left squamosal and element of
the scapula-coracoid (It is impossible to determine
D.V. Grigoriev
150
whether it is scapula or coracoid) have been lost.
Additionally, the skull mounted in Saint Petersburg
has incorrectly placed bones. For example, the right
splenial was oriented backwards, and right dentary
fragments are set in the wrong order (Fig. 5A). A de-
tailed study of this specimen is possible only because
a plaster copy was preserved as were some original
photographs. For the reconstruction of the skull (Fig.
4A–C), all available data were used. A photo of the
skull (Figs 2, 3) made right after the mounting in
1927 was used in addition to the existing original and
plaster copy material. Through this pictures, the cor-
rect position of the dentary fragments was restored.
This photo was also used for the splenial reconstruc-
tion (9C, F), which was not entirely preserved in the
original or plaster material. Apparently, in the pho-
tos, it is possible to observe mistakes made during the
mounting (shown by the arrows in Figs 2 and 3). For
example, the left angular is placed on the right side,
thereby increasing the height of the right posterior
mandibular unit, and the dentary is pushed too far
forward, thus creating a false impression of its total
length. In Fig. 3, the arrow and dotted line shows
incorrectly fitted bone to the articular. In this study,
photos of bones with protruding elements have been
taken at different depth levels and combined using
Helicon Focus 4.2.9 X64 (Focus stacking software
that increase the depth of field in an image).
The osteological terminology is based predomi-
nantly on Russell (1967), and the systematics follow
Palci et al. (2013).
SYSTEMATICS
Order Squamata Oppel, 1811
Family Mosasauridae Gervais, 1853
Subfamily Mosasaurinae Gervais, 1853
Genus Mosasaurus Conybeare, 1822
Mosasaurus hoffmanni Mantell, 1829
(Figs 2–12)
Material. Original material: CCMGE 10/2469, a
partial skull including two dentaries, with one pre-
served replacement tooth in the alveolar margin on
the left ramus (?), right and left splenials, the right
Fig. 1. Locality of Mosasaurus hoffmanni (PRM 2546), indicated by a star in the city of Penza (Penza Region, Russia).
Mosasaurus hoffmanni from the Late Cretaceous of Penza 151
Fig. 2. Laboratory assistant Stepanov N.P. and prepared skull of the Penza specimen. Year 1929. The single arrow shows the incorrectly
positioned left angular. The two arrows and the dotted line between them illustrate the correct position of the posterior end of the dentary.
Fig. 3. Prepared skull of the Penza specimen. The dotted line and arrow indicate the incorrectly fitted undefined bone to the articular.
D.V. Grigoriev
152
Fig. 4. Reconstruction of Mosasaurus hoffmanni (CCMGE 10/2469, PRM 2546) in the right lateral (A), left lateral (B) and dorsal (C)
views. Redrawn from Lingham-Soliar (1995). The presented skeletal elements are marked in gray. Oblique hatching represents skeletal
elements recovered exceptionally from the archival photos (Figs 2 and 3). Vertical hatching represents the skeletal elements that were
not preserved in the original material but that are presented in the form of plaster casts. The dotted line indicates missing portions of the
skull. Abbreviations: a, angular; ar, articular; cor, coracoid; d, dentary; f, frontal; p, parietal; pof, postorbitofrontal; pra, prearticular; sa,
surangular; spl, splenial; sq, squamosal.
Mosasaurus hoffmanni from the Late Cretaceous of Penza 153
Fig. 5. Preserved original Mosasaurus hoffmanni (CCMGE 10/2469) material in the right lateral (A) and left lateral (B) views. The arrow indicates the correct position of the
dentary fragment. All represented teeth are plaster copies that do not correspond to the real teeth.
D.V. Grigoriev
154
angular in articulation with the right surangular,
coronoid, articular and prearticular, left surangular,
articular and prearticular in the articulation as well.
Plaster copy: PRM 1-5/2546, right dentary
consisting of five parts with eight teeth sitting in
the alveolar margins; PRM 6-10/2546, left dentary
consisting of six parts with three teeth sitting in
the alveolar margins and one separate tooth with
the root; PRM 13,14/2546, right and left splenials;
PRM 16/2546, right angular in articulation with the
right surangular, coronoid, articular and prearticular;
PRM 15/2546, left angular; PRM 18/2546, left coro-
noid; PRM 17/2546, left surangular in articulation
with the articular and prearticular; PRM 19/2546
left postorbitofrontal; PRM 22/2546, left squamosal;
PRM 21/2546, parietals; PRM 23/2546, element of
the scapula-coracoid. In addition, it is known that
there were frontals and ribs initially; however, they
are not preserved to the present day.
Locality and horizon. The specimen was col-
lected in the outcrop in the Prolom ravine within the
city of Penza, near the Mironositskoe cemetery (Fig.
1). The exact modern position of the locality is un-
known. Now on this site most likely the Prolomnaya
street passes, and the locality no longer exists.
The highest horizons of the Maastrichtian (Up-
per Cretaceous) of the Belemnitella americana zone
are exposed along the Sura River in the city of Penza
area. They are represented by micaceous quartz glau-
conitic aleurite (depth of deposits – 18–20 m) along
with B. lanceolata Schloth. and B. americana Mart.
(Chibrikova 1954). Tsaregradskii (1926) notes that
the oyster genus Ostrea praesinzowi Archangelsky,
1905 (guide fossil for Maastrichtian (Glazunova
1972)) was also found in these deposits. An unusual
microfaunal complex was found in the same layer and
comprises the guide fossil for the Turonian (Bolivinita
couvigeriniformis Keller), Santonian (Reussia sub-
rotundata Cuschm. et Phomas) and Maastrichtian
(Bolivina incrassata Reuss) stages, suggesting all the
deposits listed above were eroded and took part in
the resedimentation of the B. americana zone (Chi-
brikova 1954).
DESCRIPTION
Postorbitofrontal. The left postorbitofrontal
is preserved only in the form of a plaster copy (Fig.
6A–C). The articulation for the postorbital process
of the parietal is broken at the base. The articulation
for the frontal posterolateral is also absent, and the
tip of the squamosal process is slightly broken off.
The postorbitofrontal is straight and narrow, and
the oblique suture between the postorbitofrontal
and squamosal is at least 215 mm long, begins un-
der the jugal process and is represented as a sulcus
posteriorly turning in a laterally compressed process
sandwiched between the squamosal laminas. The
jugal process is triangular in outline and extends to
approximately the same length as the main body of
the postorbitofrontal. It gradually tapers off to the
squamosal process. The jugal process is 50 mm long.
There are no signs of a postorbitofrontal transverse
dorsal ridge. Overall length of the postorbitofrontal
is 286 mm.
Squamosal. There is a preserved plaster copy of
the left squamosal (Fig. 6D–G). All processes except
for the quadrate process are more or less broken off.
The squamosal is comma shaped, tall and laterally
compressed. The postorbitofrontal process occupies
most of the squamosal. The suture with the postorbi-
tofrontal is represented by the thin, deep sulcus. The
medial wall of this sulcus is somewhat shallower than
the lateral wall. The squamosal and postorbitofrontal
together are slightly arched dorsally. The parietal
and quadrate processes are positioned relative to
each other at an angle of 90 degrees. Length of the
squamosal is 255 mm.
Frontal. The original material or casts of the fron-
tals did not survive; however, in photos (Figs 2, 3)
taken in 1927, they are distinctly visible. The bones
can be observed in two photos in lateral and dorsolat-
eral views. However, a lack of image resolution and
limited viewing angles do not allow for an accurate
description, but it is still possible to obtain some
information from the photos. Relying on the photos,
it is possible to infer that the frontals are broad and
short with sinusoidal sides. In the anterior part of the
frontals, a low midline dorsal keel is present.
Parietal. Preserved only as a plaster cast of the
parietals (Fig. 7A–F). The suspensorial rami and
right postorbital process are partly broken, and the
left postorbital process is broken at the base. In the
dorsal aspect, the main body of the bone has an hour-
glass shape with approximately the same anterior
and posterior portions without boss in the middle.
The parietal foramen is located on the anterior edge
of the bone. It is relatively small (22 by 13 mm) and
oval in outline. On the ventral side, it is surrounded
by a barely distinguishable ridge. The depth of this
Mosasaurus hoffmanni from the Late Cretaceous of Penza 155
Fig. 6. Mosasaurus hoffmanni (PRM 2546) left postorbitofrontal (A–C) and left squamosal (D–G) in the dorsal (A), ventral (B), lateral
(C), dorsomedial (D), ventrolateral (E), ventromedial (F) and dorsolateral (G) views. The reconstruction shows the position of the
postorbitofrontal and squamosal of the skull. Abbreviations: app, articulation for the postorbital process of the parietal; jp, jugal process of
the postorbitofrontal; pofp, postorbitofrontal process; pp, parietal process of the squamosal; qp, quadrate process of the squamosal.
D.V. Grigoriev
156
Fig. 7. Mosasaurus hoffmanni (PRM 2546) parietal (A–F) in the anterior (A), posterior (B), lateral (C, D), dorsal (E) and ventral (F)
views. The dotted lines indicate suture surfaces with the posteriorly projecting wings of the frontal. Abbreviations: dpp, descensus proces-
sus parietalis; pfor, parietal foramen; pop, postorbital process of parietal; sr, suspensorial ramus of parietal
Mosasaurus hoffmanni from the Late Cretaceous of Penza 157
foramen is 25 mm. The anterior border of the parietal
foramen is broken. Therefore, it is not clear whether
it is formed by the parietal, or posterior edge of the
frontal. There are triangular suture surfaces with the
posteriorly projecting wings of the frontal arranged
on the right and left of the parietal foramen (Fig 7E),
which itself is fully surrounded by the parietal. From
the foregoing, it can be concluded that the parietal
foramen is protruding into the frontal. The parietal
table bears a distinct shallow medial groove, which
begins at the posterior end of the bone, and has a
length of 93 mm. Robust postorbital processes ven-
trally and gradually becomes descensus processus
parietalis. The descensus processus parietalis are
concave in outline, thin and very wide (up to 63 mm)
and do not reach the suspensorial rami. There are
no signs of the parietal posterior shelf between the
suspensorial rami.
Dentary. Both dentaries are incomplete (Fig.
8A–K). The most posterior parts of the bones are
not preserved. The right dentary (Fig. 8A–C) is
composed of six fragments (five are known from the
factual material, one restored from a photograph)
and the left dentary (Fig. 8D–F) of four. The bone
is powerfully built. The incompleteness of the den-
taries and the breaks between the dentary parts do
not allow for the determination of the exact number
of alveolar margins in its length. There are at least
12 teeth on the right dentary and at least 15 (12 al-
veolar margins on the dentary fragments with three
more implied between the dentary fragments) on the
left. Replacement teeth erupt in the alveolar margins
(Fig. 8G). A small projection (approximately 13 mm)
of the dentary anterior to the first tooth position is
present. The crowns of the posterior marginal teeth
are not swollen above the base. The dentary medial
parapet strap is equal in height to the lateral wall of
the bone. The medial surface of the dentary is slightly
concave, with a deep Meckelian canal opened for the
length of the dentary and beginning near the anterior
tip of the bone. The original reconstruction, which
can be observed in the photos (Figs 2, 3), implies that
the dentary was longer, at least 200 mm (the poste-
riormost part has been lost). However, the existing
material does not provide grounds to believe that the
reconstruction was performed correctly. For maxi-
mum dentary length accepted the length of the left
dentary, which has the greatest number of alveolar
margins. On the basis of the most preserved poste-
rior fragment of the left dentary, it can be assumed
that the size of the teeth is on the decline, therefore
the missing dentary posterior fragment should have
a small size. The alveolar margins are not concavo-
convex. The right dentary as preserved has a length
of 910 mm and the left of 1020 mm. Maximum height
is 172 mm.
Splenial. Only the posterior parts of both spleni-
als are preserved (Fig. 9A–G), with the medial wing
on the left splenial higher compared to the right.
The anterior portion (Fig. 9B, D) of the right sple-
nial was preserved in the original material (CCMGE
10/2469), and posterior (Fig. 9A, E, G) only in a
plaster copy (PRM 13/2546). The reconstruction
(Fig. 9C, F) was made by combining the original and
plaster materials. Due to material preservation or
the features of the mounting, the lateral and medial
wings of both splenials are fused together. The ante-
rior parts of the bones are broken; however, accord-
ing to the extension of the splenial facet on the left
dentary, the bones reached anteriorly to at least the
fourth tooth position. The right splenial is clearly ex-
pressed the surface, that should be laterally exposed
in contact with the dentary. The length of this surface
is 258 mm. There are no signs of a foramen for the lin-
gual nerve on the lateral surface of the bone near the
splenial articulation (likely due to the large cracks
dissecting the medial side of the bone). The articu-
lation with the angular (Fig. 9G) is present only on
the right splenial, is laterally compressed (height to
width ratio is 0.51) and has a smooth concave surface.
Angular. Preserved left separate angular (Fig.
9H–J) and right angular in articulation with the
right surangular, coronoid, articular and prearticular
(Fig. 10A–F). The right angular is in poor condition
and is overlapped by the surangular 270 mm from the
anterior tip of the bone, where the angular is broken
off. A thin and broad wing from the medial side of the
angular and a short heavy wing from the lateral side
together form a narrow groove for the prearticular.
There is a foramen for the angular branch of the man-
dibular nerve on the anterior part of the medial wing
of the left angular. The articulation for the splenials is
preserved on both angulars (Fig. 9J) in the form of a
rounded “V” with a smooth convex surface.
Surangular. The right surangular is almost
complete (with the exception of a partially broken
dorsal wall). It is in articulation with the coronoid,
articular, prearticular and angular (Fig. 10A, B, D).
The left surangular is in approximately the same
condition but articulated only with the articular
D.V. Grigoriev
158
Fig. 8. Mosasaurus hoffmanni (PRM 2546) dentary (A–F) and teeth (J–K) in the lateral (A, E), medial (B, D), dorsal (C, F), apical (G,
K), lingual (H), buccal (I) and anterior (J) views. Magnified teeth (G) are examples of the anterior (the only remaining tooth from the
original material) and posterior teeth. Arrows indicate their actual positions. Abbreviations: acr, anterior carina; meckca, Meckelian canal;
pcr, posterior carina.
Mosasaurus hoffmanni from the Late Cretaceous of Penza 159
Fig. 9. Mosasaurus hoffmanni (CCMGE 10/2469, PRM 2546) right splenial (A–G) and left angular (H–J) in the lateral (A–C, H),
medial (D–F, I), anterior (J) and posterior (G) views. Reconstruction (C, F) made by combining the original (CCMGE 10/2469 (B, D))
and plaster materials (PRM 2546 (A, E, G–J)). The arrows indicate the actual position of the skeletal elements on the reconstructions.
Abbreviations: for, foramen for the angular branch of the mandibular nerve; lp, lateral process; maw, medial ascending wing.
D.V. Grigoriev
160
and prearticular, and the posterior end of the bone is
broken right after the glenoid fossa (Fig. 10C, E, F).
The element is elongated and laterally flattened, and
the dorsal border of the surangular is a high thin wall
that forms a coronoid buttress. This wall has a slight
bend on the medial side (Fig. 10C, D). A moderate
depression is preserved on the right surangular on
the anterolateral edge of the bone under the anterior
edge of the coronoid. This depression represents the
anterior surangular foramen (Fig. 10A). The glenoid
fossa is preserved on the left surangular (Fig. 10F);
on the right surangular, it is damaged (outlines of
the glenoid fossa on the reconstruction are drawn ap-
proximately). It is well developed, roughly oval and
slightly concave. The borders of the glenoid fossa are
defined by the ridge. The surangular takes part in the
anterior and lateral borders of the glenoid fossa, with
the rest of the fossa being formed by the articular.
The surangular-articular suture extends posteriorly
from the glenoid fossa. After the glenoid fossa suran-
gular suture rises up to the posterodorsal edge of the
bone, the suture runs for 75 mm along the edge, than
bends on the other side and then abruptly turns an-
teriorly. Further tracking of the suture position is im-
possible because of the poor preservation. The length
of the right surangular is 645 mm, left surangular is
525 mm. The surangular length occupies 75% of the
dentary length (if the overall length of the dentary is
approximately 1020 mm).
Coronoid. The preserved right coronoid is in
contact with the surangular (Fig. 10A, B) and a
plaster copy of the left coronoid. The tip of the pos-
terodorsal process, the partial medial wall, and likely,
the most anterior part are crushed. The coronoid is
saddle shaped with a well-developed posterodorsal
process. The dorsal border of the coronoid is concave
and inclined at approximately 115 degrees. There is
a “C”-shaped excavation on the medial side of the
posterodorsal process (Fig. 10B). A small broken
posteromedial process is present below this excava-
tion. The anteroventral border of the lateral wing
is emarginated for the anterior surangular foramen
(Fig. 10A). The lateral descending wing is relatively
shallow and semicircular (with the exception of
the anteroventral excavation). Because of the large
amount of the PVB glue on the bones, the position
of the lower bound of the lateral wall may be located
somewhat below those shown in the reconstruction.
The medial wing descends much lower; however, the
exact position of the lower boundary is undefined.
Even though the medial wing of the right angular is
also partially broken, on the basis of the left angular,
it can be assumed that upper medial wall of the an-
gular should be in contact with the medial wing of
the coronoid or at least that they should be in close
proximity to each other. The distance between the
preserved bones on the right posterior mandibular
unit is 27 mm.
Maximum length of the coronoid is 180 mm;
height of the lateral wing in the anterior part of the
bone is 70 mm; height of the medial wing in the mid-
dle part of the bone is 150 mm. Posterodorsal process
height is 50 mm.
Articular-prearticular. In the material there are
right articular-prearticular presented in articulation
with surangular, angular and coronoid, and missing
most of the anterior part contacting with dentary
(Fig. 10A, B, D), and left articular-prearticular ar-
ticulated with surangular also without most of the
anterior part (Fig. 10C, E, F). The prearticular is pos-
teriorly fused with the inner surface of the articular,
and they are exposed on the medial side of the suran-
gular. It is overlapped from below by the medial wing
of the angular and bounded above superficially by the
coronoid. The prearticular forms the medial margin
of the Meckelian canal. The retroarticular processes
are broken on the original material. However, on the
plaster copies, it is possible to observe that they lie in
a nearly vertical orientation (almost without twist-
ing) (Fig. 10C, D). No large foramina on the lateral
face of the retroarticular processes are present on the
existing material. They are roundly rectangular in
outline.
Marginal dentition. The description of the teeth
is based predominantly on the plaster cast material
(Figs 8H–K, 11A–H). On the original material, only
one replacement teeth on the five tooth position is
preserved on the left dentary (Fig. 8G). The teeth are
posteromedially recurved, with the exception of the
most posterior teeth (the twelfth tooth on the right
dentary and the fifteenth tooth on the left dentary),
which are slightly bent forward. The bases of the
teeth protrude above the dentary almost more than
one-third of the overall length of the tooth crowns.
The teeth are strongly bicarinate. The plaster casts
do not allow for us to hypothesize about the presence
of serrations on the carinae. The lingual and labial
surfaces are nearly equal on the posterior teeth (Fig.
8G). On the anterior teeth, the lingual surface is more
convex and large in comparison with the labial (the
Mosasaurus hoffmanni from the Late Cretaceous of Penza 161
Fig. 10. Mosasaurus hoffmanni (PRM 2546) right (A, B, D) and left (C, E, F) posterior mandibular units in the lateral (A, E), medial
(B, F) and posterior (C, D) views. Abbreviations: a, angular; ar, articular; aw, anteromedial wing; asf, anterior surangular foramen; cor,
coracoid; gl, glenoid fossa; mcp, medial crescentic pit; pmp, posteromedial process; pra, prearticular; sa, surangular.
D.V. Grigoriev
162
anterior and posterior carinae converge at angles up
to 110 degrees). The crowns of the posterior marginal
teeth are conical (Fig. 8H–K). Some crowns are dis-
tinctly faceted (for example fourth tooth on the left
mandible). The teeth are up to 103 mm high (when
measured together with the base protruding above
the dentary) and 56 mm wide at the base.
Scapula-coracoid. The base of the scapula-
coracoid element has two facets, a partly broken
neck and strongly broken off fan-like blade with an
unbroken posterior edge, which are preserved (Fig.
12A–E). On the basis of interposition of facets and
overall morphology of the bone it is possible to state
that this is the scapula-coracoid element. However,
Fig. 11. Mosasaurus hoffmanni (PRM 2546) two right anterior teeth (A–C) and a single anterior tooth with the root (D–H) in lingual
(A, D), buccal (B, D), apical (C, H), anterior (F) and posterior (G) views.
Mosasaurus hoffmanni from the Late Cretaceous of Penza 163
Fig. 12. Mosasaurus hoffmanni (PRM 2546) scapula-coracoid element in the posterior (A), anterior (B), dorsal or ventral (C), medial (D)
and ventral (E) views.
D.V. Grigoriev
164
lack of the most part of the blade and absence of di-
agnostic elements don’t allow determining whether it
is scapula or coracoid or even a right or left element.
The largest facet is strongly concave without traces
of interdigitated suture with adjacent element of the
scapula-coracoid. The main dorsal (or ventral) facet
is almost flat and less than one-third in comparison
with the anterior facet. The angle between the facet
surfaces is approximately 130 degrees. The base with
the facets is rotated by 40 degrees relative to the
blade. The neck is relatively short, and the bone be-
comes thinner right after the facets.
DISCUSSION
A.N. Ryabinin assigned the bones to Mosasaurus
giganteus; however, the only evidence of this is an
entry in the inventory book of CCMGE. No articles
or even notes with the description of this skull have
ever been published.
Because the Penza specimen has powerfully built
jaws, all of the Plioplatecarpinae may be removed
from consideration in assessing its relationships
(Konishi and Caldwell 2011). Penza specimen has
a saddle-shaped coronoid with a well-developed
posterodorsal process, while Plioplatecarpinae have
coronoid with a slight dorsal curvature (except for
Platecarpus planifrons (Konishi and Caldwell 2007)
and Selmasaurus johnsoni (Polcyn and Everhart
2008)). The absence of a long anterior projection for
the dentary and coronoid along with a slight dorsal
curvature strikes it from the candidate list for all the
Tylosaurinae (Russell 1967). Among Halisaurinae
Halisaurus ortliebi is the most similar to the Penza
mosasaur by the position of the parietal foramen,
but the relatively large size of the latter and different
contact between parietal and frontal (without over-
lapping flanges) differentiate it from the Penza speci-
men (Bardet et al. 2005). The specimen is clearly a
Mosasaurinae due to its possession of a thin-walled
surangular rising anteriorly to the posterior surface
of the coronoid.
The coronoid of the Penza specimen bears a large
vertically oriented posterior process (Fig. 10A, B), as
in Mosasaurus or Prognathodon. Clidastes also has a
significantly expanded coronoid posterior process.
However, in contrast to the Mosasaurus and Prog-
nathodon, it is more elongate with a weakly expressed
descending lateral wall (Williston, 1898). In addi-
tion, the dentary is more delicately constructed in
Clidastes (Russell 1967).
The Penza specimen has much in common with
Prognathodon genus. For example, the posterior
mandibular unit of Prognathodon overtoni Williston,
1897 (TMP 2007.034.0001), is similar compared to
the Penza specimen (Konishi et al. 2011). The only
difference is in the position of the suture between the
angular-articular and surangular on the lateral side
of the mandibular unit. In the Penza specimen, the
articular is completely overlapped by the surangular
before the glenoid suture position (Fig. 10A). Thus,
the articular-angular suture position is obscured,
whereas in P. overtoni, the surangular does not have
a complete overlap of the articular and angular. In
addition to the above, P. overtoni and other species
of Prognathodon and also Globidens have concavo-
convex alveolar margins, relatively straight frontal
sides, the absence of tooth facets and posterior teeth
with swollen crowns (Russell 1975; Bardet et al.
2005; Schulp 2006; Schulp et al. 2008).
The Penza specimen does not follow lots of
characters considered by Leblanc et al. (2012) to be
diagnostic for the tribe Mosasaurini: large triangular
posteromedial flanges of frontal dorsally overlap-
ping parietal table and the presence of dentary an-
terior projections. Furthermore, the retroarticular
inflection of the Penza specimen does not fit into the
Mosasaurini diagnosis. The Penza specimen’s retro-
articular processes lie in a nearly vertical orientation
(Fig. 10C, D), whereas in Mosasaurini, they should
be horizontal. However, included in the Mosasaurini
tribe, Mosasaurus lemonnieri Dollo, 1889, does not
exhibit this character either (personal observation of
IRSNB R28). The retroarticular process inflection of
Mosasaurus lemonnieri is 45 degrees, which is almost
the same as the dorsoventral plane of the surangular.
Despite the above characters, the Penza speci-
men shares the greatest number of characters with
Mosasaurus: a broad and short frontal, a generally
rectangular to trapezoidal shape of the parietal table
with sides converging but not meeting, a relatively
small parietal foramen size, the absence of a parietal
posterior shelf, narrow shape of the postorbitofron-
tal, absence of a postorbitofrontal transverse dorsal
ridge, presence of a small anterior dentary projection,
the dentary medial parapet strap is equal in height
to the lateral wall of the bone, essentially smooth
concavo-convex surfaces with an intermediate lat-
eral compression of the splenial-angular articular
Mosasaurus hoffmanni from the Late Cretaceous of Penza 165
surface, very concave shape of the coronoid with a
significantly expanded posterior wing, the presence
of a small coronoid posteromedial process, rapidly
rising anteriorly thin and high surangular coronoid
buttress, surangular-articular suture position behind
the condyle in the lateral view, no large foramina
on the lateral face of the retroarticular process, the
presence of tooth facets, non-swollen crowns of the
posterior marginal teeth, and strong and elevated
tooth carinae.
The closest Mosasaurus taxa that presents these
characters are as follows: Mosasaurus missouriensis
Harlan, 1834; Mosasaurus conodon Cope, 1881;
Mosasaurus lemonnieri Dollo, 1889; and Mosasaurus
hoffmanni Mantell, 1829.
Before comparison with this species, it is neces-
sary to say a few words about the teeth. In the Penza
specimen, there are at least 15 teeth on the dentary.
This character fits almost all considered Mosasaurus
taxa. Mosasaurus missouriensis has 14–15 teeth, M.
lemonnieri has 17, M. conodon has 17, and M. hoff-
manni has 14 (Bardet et al. 2004). Mulder (2004)
notes that using the dentary tooth number as a char-
acter is dangerous. Considering the mechanisms of
tooth replacement in mosasaurs, some intraspecific
variation in the tooth number is possible. In the same
paper mentioned, a M. hoffmanni specimen had 15
teeth. Therefore, the tooth number character was not
used in the comparison with Mosasaurus species in
this work.
In contrast to the Penza specimen, M. missourien-
sis has a shorter lateral wing of the coronoid without
emargination for the anterior surangular foramen.
Despite the fact that we could only observe the fron-
tal of the Penza specimen in the side view of photos,
it is clearly seen that the frontal sides are sinusoidal,
unlike the straight sides of M. missouriensis. In ad-
dition, the articular and angular are not completely
covered by the splenial (Goldfuss 1845).
The systematic relationships among the three
remaining Mosasaurus taxa are still unclear. Baird
& Case (1966) and Russell (1967) synonymized M.
lemonnieri with M. conodon. This decision was made
based on a lack of significant differences between
the Pierre Shale (South Dakota) skeleton with the
eroded skull and the Maastrichtian (Belgium and
Netherlands) skeletons. The cranial portion of the
diagnosis was made by Russell on the basis of the
Maastrichtian M. lemonnieri. The comparison was
conducted on the basis of Dollo’s (1894) work.
However, Lingham-Soliar (1992) re-assessed the sys-
tematic status of M. lemonnieri as a valid taxon and
noted some mistakes in Dollo’s work, including the
comparisons with other M. lemonnieri specimens. For
this reason, Russell’s research has been questioned.
Mulder et al. (2004) suggested that M. lemonnieri
could be a juvenile M. hoffmanni because the main
differences between M. hoffmanni and M. lemonnieri
can be observed only in “ideal cases”. In addition,
these specimens have almost identical quadrates.
Assuming M. lemonnieri is a valid taxon does not
allow to compare the Penza specimen and M. conodon
because the description of the M. conodon cranial
material was made on the basis of the M. lemonnieri
skull (Russell 1967). In addition, in this case, it is not
possible to provide an unambiguous definition of the
Penza material because it shares different characters
with both M. lemonnieri and M. hoffmanni. More-
over, the Penza specimen has the most characteristic
feature of the teeth in M. hoffmanni – the posterior
carina shifts from a somewhat lateral position in the
anterior teeth to a posterior position further along
the tooth row (Fig. 8G–K) (Lingham-Soliar 1992,
1995; Mulder 2004). The Penza specimen shares a
frontal with convex lateral margins and powerfully
built dentary characters with M. hoffmanni, whereas
M. lemonnieri has a slender dentary, such as in the Cli-
dastes (Russell 1967; Lingham-Soliar 1992). How-
ever, depending on the animal size, it could be more
robust (Lingham-Soliar 1992). The Penza specimen
shares approximately the same inflection of the retro-
articular processes and a similar surangular-articular
lateral suture trace with M. lemonnieri (personal ob-
servation on IRSNB R28). Characters on which it is
possible to attribute the Penza specimen to M. hoff-
manni can be considered as more relevant than those
to M. lemonnieri.
Even so, the author tends to agree with the opin-
ion of Mulder et al. (2004) and Russell (1967), i.e., M.
lemonnieri is a synonym of M. hoffmanni. In that case,
the definition of the Penza specimen as M. hoffmanni
is assured.
Characteristic features of the CCMGE 10/2469
are an enormous descensus processus parietalis (Fig.
7E, F) and the absence of a firmly interdigitated su-
ture between the scapula and coracoid, such as in M.
hoffmanni (Lingham-Soliar 1992).
There are almost no teeth under the replacement,
suggesting that the specimen likely represent a ma-
ture animal.
D.V. Grigoriev
166
The overall length of the skull is more than
1700 mm (the length of the right posterior mandibu-
lar unit is 690 mm, the length of the left dentary is
more than 1020 mm). Thus, the total length of the
animal should be approximately 17 m (using Russell’s
(1967) length of the M. hoffmanni jaw as equal to
10% of the overall body length). M. hoffmanni from
the Penza is one of the largest mosasaurs ever known.
ACKNOWLEDGEMENTS
The author warmly thanks the director of CCMGE
(A.R. Sokolov) and the director of PRM (V.N. Zimen-
kov) for permission to work with the collections and
T.V. Kurazhova, T.V. Vinogradova and N.M. Kadlets for
methodological help. The author is indebted to I.V. Agaeva
for providing access to the Penza plaster casts of the speci-
men and A. Folie to the IRSNB collections, L.N. Ivanova for
providing the archival materials of the PRM about the exca-
vations and history of the specimen findings, A.E. Nelikhov
for archival photos and other materials, and M.J. Polcyn and
E.W
.A. Mulder for help with the literature and construc-
tive comments on the manuscript. The author is grateful to
A.O. Averianov for conversations and useful advices.
REFERENCES
Arkhangelsky M.S., Ivanov A.V. and Nelikhov A.E.
2012. When the Volga River was the sea. Saratov State
Technical University. 56 p. [In Russian]
Baird D. and Case G.R. 1966. Rare marine reptiles from
the Cretaceous of New Jersey. Journal of Paleontology,
40: 1211–1215.
Bardet N., Pereda Suberbiola X., Iaroche’ne M.,
Bouya B., and Amaghzaz M. 2005. A new species of
Halisaurus from the Late Cretaceous phosphates of
Morocco, and the phylogenetical relationships of the
Halisaurinae (Squamata: Mosasauridae). Zoological
Journal of the Linnean Society, 143: 447–472.
Bardet N., Pereda Suberbiola X., Iaroche’ne M., Bou-
yahyaoui F., Bouya B. and Amaghzaz M. 2004.
Mosasaurus beaugei Arambourg, 1952 (Squamata,
Mosasauridae) from the Late Cretaceous phosphates of
Morocco. Geobios, 37: 315–324.
Bayarunas M.V. 1914. Report on the trip to Atkarsky
District of Saratovsky Governorate and Signahsky
District of Tiflisskaya Governorate. Works of the Geo-
logical Museum named after Peter The Great of Imperial
Academy of Sciences, 8: 153–158. [In Russian]
Chibrikova E.V. 1951. About the “Belemnitella Ameri-
cana” zone in the Penza Region”. Scientific notes of
Saratov State University, 23: 72–79. [In Russian]
Chibrikova E.V. 1954. State Geological Map of the USSR,
scale of 1:200000, explanatory report to the letter
N-38-XXVIII, Gorodische-Penza (edited by Olly A.I.).
The Ministry of Geology and Mineral Resources Con-
servation. 32 p. [In Russian]
Dollo L. 1894. Nouvelle note sur l’ostéologie des mosasau-
riens. Bulletin de la Société belge de Géologie, de Paléon-
tologie et d’Hydrologie, Mémories, 6: 219–259.
Glazunova A.K. 1972. Palaeontological basis for the strati-
graphic subdivision of Cretaceous deposits in the Volga
region. Leningrad: Nedra Press. 144 p. [In Russian]
Goldfuss G.A. 1845. Der Schädlbau des Mosasaurus, durch
Beschreibung einer neuen Art dieser Gattung erläutert.
Nova Acta Academia Ceasar Leopoldino-Carolinae Ger-
manicae Natura Curiosorum, 21: 173–200.
Grigoriev D.V. 2013. Redescription of Prognathodon
lutugini (Squamata, Mosasauridae). Proceedings of the
Zoological Institute RAS, 317(3): 246–261.
Konishi T. and Caldwell M.W. 2007. New specimens of
Platecarpus planifrons (Cope, 1874) (Squamata: Mosa-
sauridae) and a revised taxonomy of the genus. Journal
of Vertebrate Paleontology, 27(1): 59–72.
Konishi T. and Caldwell M.W. 2011. Two new plioplate-
carpine (Squamata, Mosasauridae) genera from the
Upper Cretaceous of North America, and a global
phylogenetic analysis of plioplatecarpines. Journal of
Vertebrate Paleontology, 31(4): 754–783.
Konishi T., Brinkman D., Massare J.A. and Caldwell
M.W. 2011. New exceptional specimens of Prog-
nathodon overtoni (Squamata: Mosasauridae) from the
upper Campanian of Alberta, Canada, and the system-
atics and ecology of the genus. Journal of Vertebrate
Paleontology, 31(5): 1026–1046.
Lavrentiev V.A. 1930. Mineral resources of Stalingrad Dis-
trict, Lower Volga Region, in connection with geologi-
cal conditions of their deposits. Preliminary report on
works of the Natural and Historical Department of the
Museum for 1928–1929. Stalingrad. 23 p. [In Russian]
Leblanc A.R.H., Caldwell M.W. and Bardet N. 2012.
A new mosasaurine from the Maastrichtian (Upper
Cretaceous) phosphates of Morocco and its implica-
tions for mosasaurine systematics. Journal of Vertebrate
Paleontology, 32(1): 82–104.
Lingham-Soliar T. 1995. Anatomy and functional mor-
phology of the largest marine reptile known, Mosasau-
rus hoffmanni (Mosasauridae, Reptilia) from the Upper
Cretaceous, Upper Maastrichtian of the Netherlands.
Philosophical Transactions of the Royal Society of Lon-
don, 347: 155–180.
Mulder E.W.A., Coernelissen D. and Verding L. 2004.
Is Mosasaurus lemonnieri a juvenile Mosasaurus hoff-
manni? A discussion. In: Schulp, A.S. and Jagt, J.W.M.
(Eds.). First Mosasaur Meeting, Maastricht, 8–12 May
2004, Abstract book and field guide: 62–66.
Palci A., Caldwell M.W. and Papazzoni C.A. 2013. A
new genus and subfamily of mosasaurs from the Up-
per Cretaceous of northern Italy. Journal of Vertebrate
Paleontology, 33(3): 599–612.
Mosasaurus hoffmanni from the Late Cretaceous of Penza 167
Pervushov E.M., Arkhangelsky M.S. and Ivanov A.V.
1999. Catalogue of the Marine Reptiles Localities of in
the Jurassic and Cretaceous Deposits of Lower Volga
Region. Izdatel’stvo Gosudarstvennogo uchebno-na-
uch nogo tsentra Kolledzh, 1–231. [In Russian]
Polcyn M.J. and Everhart M.J. 2008. Description and
phylogenetic analysis of a new species of Selmasaurus
(Mosasauridae: Plioplatecarpinae) from the Niobrara
Chalk of western Kansas. In: Everhart M.J. (Ed.). Pro-
ceedings of the Second Mosasaur Meeting. Fort Hays
Studies, Special Issue 3: 13–28.
Russell D.A. 1975. A new species of Globidens from South
Dakota, and a review of the globidentine mosasaurs.
Fieldiana, Geology: Field Museum of Natural History,
33: 235–256.
Russell D.A. 1967. Systematics and morphology of
American mosasaurs. Bulletin of the Peabody Museum
of Natural History, 23: 1–241.
Schulp A.S. 2006. A comparative description of Prog-
nathodon saturator (Mosasauridae, Squamata), with
notes on its phylogeny. In: A.S. Schulp (Ed.). On Maas-
tricht Mosasaurs. Publicaties van het Natuurhistorisch
Genootschap in Limburg 45(1): 19–56.
Schulp A.S., Polcyn M.J., Mateus O., Jacobs L.L. and
Morais M.L. 2008. A new species of Prognathodon
(Squamata, Mosasauridae) from the Maastrichtian of
Angola, and the affinities of the mosasaur genus Liodon.
In: Everhart M.J. (Ed.). Proceedings of the Second
Mosasaur Meeting. Fort Hays Studies, Special Issue 3:
1–12.
Tsaregradskii V. 1935. Detailed description of the mosa-
saur Dollosaurus lutugini Jak. Ezhegodnik Vsesoyuznogo
Paleontologicheskogo Obshestva, 10: 49–54. [In Rus-
sian]
Tsaregradskii V. 1926. Mosasaur remains from Saratov
province and Ural region. Izvestiya Geologicheskogo
Komiteta, 45: 563–571. [In Russian]
Williston S.W. 1898. Mosasaurs. The University Geological
Survey of Kansas, 4: 81–222.
Yakovlev N.N. 1905. Notes about mosasaurs. Izvestiya
Geologicheskogo Komiteta, 24: 134–152. [In Russian]
Yakovlev N.N. 1901. Remains of the Late Cretaceous
mosasaur from the south of Russia. Izvestiya Geolo-
gicheskogo Komiteta, 20: 507–522. [In Russian]
Yarkov A.A. 1993. History of Russian mosasaurs research
and some remarks on their taxonomy. Voprosy strati-
grafii paleozoya, mezozoya i kainozoya, 8: 26–40. [In
Russian]
Submitted December 13, 2013; accepted May 7, 2014.
... The posterior carina points laterally forming strongly unequal labial and lingual surfaces. The high degree of labiolingual asymmetry indicates origin from the front of the jaw (Grigoriev, 2014) (Grigoriev, 2014;Street and Caldwell, 2017). Apical curvature is mediodistally oriented. ...
... The posterior carina points laterally forming strongly unequal labial and lingual surfaces. The high degree of labiolingual asymmetry indicates origin from the front of the jaw (Grigoriev, 2014) (Grigoriev, 2014;Street and Caldwell, 2017). Apical curvature is mediodistally oriented. ...
... Russell, 1967 (Bardet and Tunoğlu, 2002;Jagt et al., 2008;Bardet et al., 2013). Definitive occurrences include Belgium (Lingham-Soliar, 1995), Bulgaria (Jagt et al., 2006), Denmark (Lindgren and Jagt, 2005), the Netherlands (Mantell, 1829;Lingham-Soliar, 1995), the Russian Federation (Grigoriev, 2014), Spain (Bardet et al., 2013), and Turkey (Bardet and Tunoğlu, 2002). Fragmentary remains attributed to Mosasaurus cf. ...
Full-text available
Article
Marginal tooth crowns from the hypercarnivorous marine reptile Mosasaurus hoffmannii Mantell, 1829 are reported for the first time from the Late Cretaceous (Maastrichtian) phosphates of Morocco. Fossilized remains of this species are previously known from Campanian and Maastrichtian outcrops in Europe, North America, and western Asia at a paleolatitudinal belt of 30-45°N. New fossil material originates from the Upper Couche III layer of the Oulad Abdoun Basin, south of Oued Zem, Morocco. The discovery of M. hoffmannii in Morocco extends its paleobiogeographic range south to 25°N and into the southern margin of the Mediterranean Tethys.
... Shapiro-Wilk tests determined that the size ranks, growth ranks, and QH measurement data are normally distributed, but the TSL measurement data are not (right, bottom). Zietlow 53 (Grigoriev, 2014); AMNH FARB 1389 is the holotype of M. maximus, which has been synonymized with M. hoffmannii (Mulder, 1999). "TSMHN" is abbreviated as "TM" by Harrell and Martin (2015); NHMUK 42929 is referred to by Lingham-Soliar (1995) and Mulder (1999) as BMNH 42929; FHSM VP 78 is referred to by Russell (1967) as FHM 1654; AMNH FARB 1389 is the holotype of M. maximus, which has been synonymized with M. hoffmannii (Mulder, 1999 Russell, 1967Russell, 1967; measurements given YPM 3977 T. proriger Russell, 1967Russell, 1967; measurements given YPM 4002 T. proriger Russell, 1967Russell, 1967; measurements given YPM 3981 T. proriger Russell, 1967Russell, 1967 Russell, 1967Russell, 1967; measurements given YPM 3992 T. nepaeolicus Russell, 1967Russell, 1967; measurements given YPM 4000 T. nepaeolicus Russell, 1967Russell, 1967; measurements given YPM 3976 T. nepaeolicus Russell, 1967Russell, 1967 ...
... Measurement sources are listed in Appendix 5. Estimates made by the author using scale bars in the literature or due to incomplete material are indicated by a single asterisk, estimates from the literature are indicated by two asterisks, and missing measurements are indicated by question marks. Notes: TMP 1982.050.0010 is a cast of LACMNH 28964; CMN 51258 through 51263 are fragments from a single individual (Stewart and Mallon, 2018); AMNH FARB 124 and 134 are a skull and jaws, respectively, from a single individual (Jiménez-Huidobro and Caldwell, 2019); PRM 2546 is a cast of CCMGE 10/2469, and both were referenced for coding(Grigoriev, 2014); a measurement was published for (B) CMN 8162(Stewart & Mallon, 2018), but it is inaccurate due to restoration of the specimen(Konishi, 2019 [pers. comm.]). ...
Thesis
Mosasaurs were large aquatic lizards that lived during the Late Cretaceous. Their fossils are found across the globe, but despite a multitude of specimens of varying maturity, a detailed growth series has not been proposed for any mosasaur taxon. Four taxa – Tylosaurus proriger, T. kansasensis/nepaeolicus, Tethysaurus nopcsai, and Mosasaurus hoffmannii – have robust fossil records with specimens spanning a wide range of sizes and are thus ideal for studying mosasaur ontogeny. Furthermore, an analysis of growth provides an opportunity to test the synonymy of T. kansasensis with T. nepaeolicus, sexual dimorphism, and, by sampling several mosasaur taxa, ancestral patterns of mosasaur growth can be identified. Fifty-nine hypothetical growth characters were identified, including size-dependent, size-independent, and phylogenetic characters, and quantitative cladistic analysis was used to recover growth series for the four taxa. The results supported the synonymy of T. kansasensis with T. nepaeolicus but did not support a previous hypothesis that T. kansasensis represent juveniles of T. nepaeolicus. A Spearman rank-order correlation test resulted in a significant correlation between two measures of size (total skull length and quadrate height) and maturity for all taxa except in M. hoffmannii, which is likely due to the small sample size and limited data availability for the taxon. Finally, 11 growth changes – eight of which involve the quadrate – were shared across two or more taxa and none of the ontogram topologies showed evidence of sexual dimorphism.
... recovered from separate upper Campanianlower Maastrichtian outcrops in central Cuba. Fossils of Mosasaurus have been recorded around the globe (i.e., Mulder, 1999;Machalski et al., 2003;Fernández et al., 2008;Sakurai, 2008;Grigoriev, 2014;Polcyn et al., 2014;Bardet et al., 2004Bardet et al., , 2013Bardet et al., , 2015Jiménez-Huidobro et al., 2017), including Antarctica (Martin, 2006;Fernández and Gasparini, 2012). During the Late Cretaceous this genus experienced a rapid diversification, reaching a cosmopolitan distribution, especially in ancient coastal environments and subtropical epicontinental seas. ...
Article
Remains of Cretaceous vertebrates have been scarce in the fossil record of Cuba, but recent exploration of Upper Cretaceous outcrops in the central part of the island has led to the discovery of new fossil-bearing deposits from nearshore depositional environments. Here, we report upon two isolated marginal teeth, which we identified as belonging to the genus Mosasaurus. The specimens described here, recovered from two upper Campanian – lower Maastrichtian outcrops in central Cuba, represent the first record of mosasaurs from the West Indies, and along with other marine fossils suggest that the Caribbean played an important role in the faunal interconnection across seaways and oceans in the region.
... Late Cretaceous marine reptile fossils have been documented from European Russia (Fig. 1A) for almost 180 years (e.g., Eichwald, 1842). Most of these specimens derive from localities along the Volga River in Penza, Saratov, Ulyanovsk, and Volgograd oblasts (¼ 'provinces'), and the Chuvash Republic in the Volga Federal District (e.g., Sintsov, 1872;Yakovlev, 1901;Bogolyubov, 1911;Tsaregradsky, 1926;Persson, 1963;Ochev, 1976;Nesov et al., 1988;Yarkov, 1989Yarkov, , 1993Arkhangelsky, 1998;Pervushov et al., 1999;Storrs et al., 2000;Arkhangelsky et al., 2007a;Arkhangelsky et al., 2007b;Grigoriev et al., 2009;Berezin, 2013Berezin, , 2016Fischer et al., 2014;Grigoriev, 2014;Grigoriev et al., 2015;Arkhangelsky et al., 2017;Zverkov et al., 2018a;Zverkov and Pervushov, 2020). By contrast, specimens from the neighbouring Central Federal District (¼ Central Russia: Fig. 1A) have received less research attention. ...
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During the Cenomanian–Turonian transition (∼94 Ma), what is today Central Russia formed part of the northern epicontinental margin of the Tethys Ocean. Diverse marine vertebrate faunas inhabited these palaeoenvironments, but their fossils are incompletely documented. Here, we report the discovery of marine reptile remains, recovered together with pterosaur, chondrichthyan, and actinopterygian fish material from a basal-most glauconitic sand and gravel layer of the Dmitrov Formation. These strata are exposed in an active quarry near the village of Malyy Prolom in the Shatsky District of Ryazan Oblast, Central Russia. The Dmitrov Formation deposits are middle–upper Santonian, but unconformably contact the underlying lower–middle Cenomanian Yakhroma Formation via a condensed boundary horizon that contains the vertebrate fossils with bivalve shell fragments and siliceous and phosphatic clasts. Such sedimentary characteristics indicate a high-energy shoreface setting where the vertebrate teeth and bones were likely reworked during cyclical regressions commencing in the latest Cenomanian–early Turonian. Time-averaging is also evidenced by the mixed occurrences of brachauchenine pliosaurids, elasmosaurid and polycotylid plesiosauroids, ophthalmosaurid ichthyosaurians similar to Pervushovisaurus, and a possible yaguarasaurine mosasauroid. These taxa are typical of Cenomanian–Turonian assemblages from across the northern peri-Tethys, and represent components of what were probably palaeobiogeographically widespread marine reptile faunas.
... Scale bar equals 10 mm decortication. Proportions suggest this to be a dorsal vertebra of the mosasaurine Mosasaurus hoffmannii Mantell, 1829, the largest mosasaur species in the area (see Lingham-Soliar, 1995;Grigoriev, 2013;Street & Caldwell, 2016). ...
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Isolated bones of three taxa of marine reptiles (Mosasaurus hoffmannii Mantell, Plioplatecarpus marshi Dollo and Allopleuron hofmanni (Gray)) from various levels within the Maastricht Formation (upper Maastrichtian) at the former ENCI-HeidelbergCement Group quarry (Maastricht, the Netherlands) exhibit bioerosional traces and encrustation. Episkeletozoans include dimyid, ostreid and monopleurid bivalves, at least three species of cheilostome and cyclostome bryozoans and two adnate calcareous foraminifera. The bones show biting traces (Gnathichnus pentax Bromley, Linichnus cf. serratus Jacobsen & Bromley and Machichnus isp.), as well as borings. The latter may be referred to Karethraichnus lakkos Zonneveld, Bartels, Gunnell & McHugh, which is here considered to be a junior synonym of Gastrochaenolites isp.
... The rarity of amber-embedded anguimorphs is not surprising; amber is typically a preservation filter that entraps predominantly small organisms (Arnold and Poinar, 2008;Daza et al., 2016;Fontanarrosa et al., 2018), whereas extant anguimorphs are typically large bodied (mean maximum SVL ¼ 249 mm; Meiri, 2008). Among extant lizards they are rivaled only by the largest iguanians (to 750 mm SVL; Meiri, 2008) and include the largest living lizard (Varanus komodoensis, maximum SVL 1.54 m; Meiri, 2008) and extinct forms of even larger size (e.g., V. priscus, with an estimated precaudal length of 2.1 m and the marine mosasaurs reaching a total length of 17 m; Benton, 2014;Grigoriev, 2014). The squamate lineages thus far found in amber include iguanians, stem gekkotans, and lacertoideans (Arnold and Poinar, 2008;Daza et al., 2016;Fontanarrosa et al., 2018), groups today represented by numerous small and miniaturized species (Rieppel, 1984;Feldman et al., 2016). ...
Article
We report the discovery of a new genus and species of amber-preserved lizard from the mid-Cretaceous of Myanmar. The fossil is one of the smallest and most complete Cretaceous lizards ever found, preserving both the articulated skeleton and remains of the muscular system and other soft tissues. Despite its completeness, its state of preservation obscures important diagnostic features. We determined its taxonomic allocation using two approaches: we used previously identified autapomorphies of squamates that were observable in the fossil; and we included the fossil in a large squamate morphological data set. The apomorphy-based identification of this specimen, including comparative data on trunk elongation in squamates, suggests its allocation to the stem-group Anguimorpha. Results from the phylogenetic analysis places the fossil in one of four positions: as sister taxon of either Shinisaurus crocodilurus or Parasaniwa wyomingensis, at the root of Varanoidea, or in a polytomy with Varanoidea and a fossorial group retrieved in a previous assessment of squamate relationships. It is clear that this fossil has many similarities with anguimorph squamates and, if this taxonomic allocation is correct, this fossil would represent the first amber-preserved member of stem Anguimorpha ever recorded, and the smallest known member of that group. It further emphasizes the role of amber inclusions in expanding our understanding of the diversity of Cretaceous lizard communities.
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Snakes comprise nearly 4,000 extant species found on all major continents except Antarctica. Morphologically and ecologically diverse, they include burrowing, arboreal, and marine forms, feeding on prey ranging from insects to large mammals. Snakes are strikingly different from their closest lizard relatives, and their origins and early diversification have long challenged and enthused evolutionary biologists. The origin and early evolution of snakes is a broad, interdisciplinary topic for which experts in palaeontology, ecology, physiology, embryology, phylogenetics, and molecular biology have made important contributions. The last 25 years has seen a surge of interest, resulting partly from new fossil material, but also from new techniques in molecular and systematic biology. This volume summarises and discusses the state of our knowledge, approaches, data, and ongoing debates. It provides reviews, syntheses, new data and perspectives on a wide range of topics relevant to students and researchers in evolutionary biology, neontology, and palaeontology.
Chapter
Snakes comprise nearly 4,000 extant species found on all major continents except Antarctica. Morphologically and ecologically diverse, they include burrowing, arboreal, and marine forms, feeding on prey ranging from insects to large mammals. Snakes are strikingly different from their closest lizard relatives, and their origins and early diversification have long challenged and enthused evolutionary biologists. The origin and early evolution of snakes is a broad, interdisciplinary topic for which experts in palaeontology, ecology, physiology, embryology, phylogenetics, and molecular biology have made important contributions. The last 25 years has seen a surge of interest, resulting partly from new fossil material, but also from new techniques in molecular and systematic biology. This volume summarises and discusses the state of our knowledge, approaches, data, and ongoing debates. It provides reviews, syntheses, new data and perspectives on a wide range of topics relevant to students and researchers in evolutionary biology, neontology, and palaeontology.
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Teleosauroidea was a clade of ancient crocodylomorphs that were a key element of coastal marine environments during the Jurassic. Despite a 300-year research history and a recent renaissance in the study of their morphology and taxonomy, macroevolutionary studies of teleosauroids are currently limited by our poor understanding of their phylogenetic interrelationships. One major problem is the genus Steneosaurus , a wastebasket taxon recovered as paraphyletic or polyphyletic in phylogenetic analyses. We constructed a newly updated phylogenetic data matrix containing 153 taxa (27 teleosauroids, eight of which were newly added) and 502 characters, which we analysed under maximum parsimony using TNT 1.5 (weighted and unweighted analyses) and Bayesian inference using MrBayes v3.2.6 (standard, gamma and variation). The resulting topologies were then analysed to generate comprehensive higher-level phylogenetic hypotheses of teleosauroids and shed light on species-level interrelationships within the clade. The results from our parsimony and Bayesian analyses are largely consistent. Two large subclades within Teleosauroidea are recovered, and they are morphologically, ecologically and biogeographically distinct from one another. Based on comparative anatomical and phylogenetic results, we propose the following major taxonomic revisions to Teleosauroidea: (1) redefining Teleosauridae; (2) introducing one new family and three new subfamilies; (3) the resurrection of three historical genera; and (4) erecting seven new generic names and one new species name. The phylogeny infers that the Laurasian subclade was more phenotypically plastic overall than the Sub-Boreal-Gondwanan subclade. The proposed phylogeny shows that teleosauroids were more diverse than previously thought, in terms of morphology, ecology, dispersal and abundance, and that they represented some of the most successful crocodylomorphs during the Jurassic.
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Als während der Späten Kreidezeit auf dem Land die Dinosaurier herrschten, waren im Meer die Mosasaurier die Top-räuber. Ein Zahnfund von Stevns Klint be-weist, dass es in Dänemark kurz vor Ende der Kreidezeit drei Gattungen dieser Mee-resungeheuer gab. Aus der Maastrichter Gegend sind in den letzten Jahren mehrere Teilskelette gefunden worden, die uns ein Bild der Di-versität im ausgehenden Maas-trichtium verschaff en.
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Dollosaurus lutugini (Yakovlev, 1901) is the only valid species known from the territory of the former USSR. It was described from Campanian deposits of Eastern Ukraine on the basis of an incomplete skeleton. This study provides a description of an osteological material including the previously undescribed epipterygoid and squamosal. Phylogenetic analysis of a data matrix of 37 terminal taxa and 135 characters shows that D. lutugini and Prognathodon solvayi Dollo, 1889 are sister taxa. P. lutugini is distinct from P. solvayi by possession of smooth enamel surface of teeth, depression of anteriormost trunk vertebrae condyles, larger relative length of cervical vertebrae, and a distinct, horizontally interdigitating articulating surface of the splenial and angular. We conclude that D. lutugini is in Prognathodon clade; generic name of Dollosaurus Yakovlev, 1901 is a subjective junior synonym of the Prognathodon Dollo, 1889. Резюме: Dollosaurus lutugini (Yakovlev, 1901), описанный по неполному скелету из кампанских отложений Восточной Украины, является единственным видом мозазавров с территории СССР. Приводится полное морфологи-ческое описание всего остеологического материала, включая ранее не описанные верхнекрыловидную и чешуйчатаю кости. Филогенетический анализ 37 таксонов мозазавров, основанный на распределении 135 признаков, показал, что D. lutugini является сестринским таксоном Prognathodon solvayi Dollo, 1889. От по-следнего вида D. lutugini отличается наличием бугорков и ямок на сочленовной поверхности между пла-стинчатой и угловой костями, более ровной поверхностью зубов, большим дорсовентральным сжатием мы-щелков переднетуловищных позвонков и большей относительной длиной шейных позвонков. Поскольку D. lutugini попадает в кладу видов Prognathodon, родовое название Dollosaurus Yakovlev, 1901 является младшим субъективным синонимом рода Prognathodon Dollo, 1889.
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Three new species of the feather mite subfamily Ingrassiinae (Acariformes: Astigmata: Xolalgidae) are described from shearwaters and petrels (Procellariiformes: Procellariidae) in the North-East of Atlantic Ocean: Ingrassia calonectris sp. n. from Calonectris borealis (Cory) (type host) and Calonectris edwardsii (Oustalet), Ingrassia micronota sp. n. and Opetiopoda bulweriae sp. n. from Bulweria bulwerii (Jardine and Selby).
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Mosasaur remains discovered in 1996 include a complete but disarticulated skull, twenty-six vertebrae, and ribs, collected from the Smoky Hill Chalk (Lower Santonian) of Gove County, Kansas, and currently housed in the collections of the Sternberg Museum catalogued as FHSM VP-13910. The remains have been informally referred to as Platecarpus planifrons in abstract, journal article, popular print, and on the Internet since 1998. Subsequent comparison with the type material of P. planifrons and other plioplatecarpine mosasaurs does not support the earlier identification but instead warrants referral of FHSM VP-13910 to the genus Selmasaurus. The new material differs from the holotype of Selmasaurus russelli in a number of respects and justifys erection of a new species, Selmasaurus johnsoni n. sp. Phylogenetic analysis recovers a topology placing Selmasaurus as the sister taxon to a clade comprised of (Angolasaurus (Platecarpus + Plioplatecarpus)) and Ectenosaurus as the sister taxon of that clade. However, derived characters shared between Ectenosaurus and Selmasaurus suggest a closer relationship between those two taxa, and is our preferred phylogenetic hypothesis.
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Referenced checklists are provided of the 86 species of parasitic feather, quill, respiratory, skin, and nest mites (Acarina) that are known from 116 species of hawks, eagles, falcons, and vultures, and the 91 species of parasitic mites known from 51 species of owls.