NESSOV, L. A.
and A. O. AVERIANOV. 1996. Early Chimaeriformes of Russia, Ukraine, Kazakhstan
and Middle Asia II. Description of New Taxa. Vestnik Sankt-Peterburgskogo
Universitita, Ser. 7, Iss. 3(21):3-10.
Translated by Oleg LEBEDEV
New materials of the fossil chimaeriform fishes were collected in the
Commonwealth of Independent States (CIS) recently (see locality overview
in ). The most productive year was 1994; in this year, L. A.
NESSOV, A. V. GRUBA and A. A. TIMOFEYEV collected about 1,000 chimaeriform
tooth plates in the sands and sandstones of the Upper Albian-Cenomanian
deposits in the Stoylo quarry close to the town of Gubkin (the Belgorod
Region). A part of the material from the localities near Gubkin originates
from unweathered and undisturbed deposits and is well dated. This new
material is extremely important for the estimate of chimaeriform diversity
at the Early-Late Cretaceous boundary, when this group flourished, and
especially for the study of the morphology of the dentition of the rare
chimaeriforms. New chimaeriform taxa from the Albian-Cenomanian of Russia
(in the vicinity of the town of Gubkin) and the Oligocene of Kazakhstan
are described below.
Genus Callorhinchus Lacepede 1798
Callorhinchus borealis sp. nov.
From the Latin borealis - northern.
TsNIGR museum N 1/12963, a right palatine tooth plate
(Text fig. 1: 3), the Stoylo quarry; Upper Albian, Lower Cretaceous.
Palatine tooth plates (Text figs. 1: 2, 3) are wide, with
a short symphyseal margin; the length of the latter is no longer than
that of the lingual edge; these plates bear two tritors (internal and
median) which may be completely isolated (two specimens, text fig. 1:
3a; and  text fig. 1:3) or connected to each other by a narrow
bridge in the posterior part (one specimen, text fig. 1: 2). The median
tritor is approximately twice as short as the internal one. There is a
small oval-shaped median tritor on the mandibular tooth plate (text fig.
1: 4), as well as one or two short and narrow symphyseal tritors and a
similar external one. The descending lamina  is well expressed
on both the palatine and mandibular tooth plates. The vomerine tooth plates
conditionally assigned to this species (text fig. 1: 1) bear three tubercles
each close to a wide symphyseal surface; the anterolateral slope of each
exhibits a short row of small rounded tritors. A field of closely spaced
vertical "point" tritors, whose elements are only somewhat disposed in
longitudinal rows is found over the wear surface.
C. borealis is most close to the Late Cretaceous
C. hectori Newton 1876 from New Zealand in its tooth plate
construction , differing from that form by its shorter symphyseal
margin and the lesser elongation of the junction of its internal and median
tritors. From C. newtoni Ward 1973 (Paleocene, Thanetian)
and C. regulbiensis Gurr 1963 (Lower Eocene, Sparnacian)
of England [5,6] the new species differs in the comparatively
smaller area occupied by tritors on the palatine tooth plate and in the
greater isolation of the internal tritor from the median one. It also
differs from the latter species by the oval shape and relatively smaller
size of the median tritor on the mandibular tooth plate, as well as the
smaller size of the external and posterior tritors on that plate. Compared
to C. crassus Woodward and White 1930 from the Oligocene-Miocene
of Argentina , the labial edge of the mandibular tooth plate
in this species is more convex and rounded when viewed from below, the
external tritor is comparatively shallower and placed closer to the lingual
margin, and there are 1-2 symphyseal tritors.
In Recent adult callorhynchids, the internal and median tritors on the
palatine tooth plate are usually fused over much of their length. This
is true for Callorhinchus callorhynchus (L., 1758) from the
coastal basins of South America, C. capensis Dumeril 1865
from the South African seas, and C. milii Bory 1823 from
the South Australian and New Zealand waters [3: fig.3, 4, 8; Pl.6:
fig. 1, 2, 5-7,9; fig.9]. However, in one of the modern Callorhinchus
species, C. smithi Lay and Bennett 1939 from the coastal
waters of South America [8: Pl.6, fig. 1], the internal and median
tritors are completely separated and appear as two narrow parallel crests.
In all extant species the palatine tooth plates are comparatively narrow
(rostrocaudally elongated), their symphyseal margin being 1.5 to 2 times
longer than the lingual one; only the median tritor is present on the
mandibular tooth plate.
In the extant callorhynchids, the median and internal
tritors on the palatine tooth plate are usually isolated in juvenile individuals
and fuse at the later ontogenetic stages . Possibly, in C.
borealis n. sp. both tritors remained isolated in some individuals
during their lifetime.
Fossil callorhynchid tooth plates are exceptionally rare. Callorhinchus
remains compose only 0.83% of the total of 1,500 tooth plates collected
by various authors in the Stoylo and Lebedi quarries . It is
interesting to note that Callorhinchus species have survived
until now, being represented by solitary tooth plates found in Mesozoic
and Cenozoic deposits, whereas Ischyodus and Edaphodon
, dominant in the Cretaceous assemblages, became extinct in the Late Cretaceous
and Neogene, respectively. Callorhinchus 's survival may
be due to its insignificant dietary specialization , while
the more specialized Ischyodus and Edaphodon
possessed robust tooth plates and were more restricted to a durophagous
and probably scavenging mode of eating . Callorhinchus
remains are found in the Northern Hemisphere only up to the Eocene; its
extant members in the Southern Hemisphere are probably relicts forced
out of northern waters.
The Callorhinchus collection described is the largest of
those known from a single locality or a group of close localities. The
new species from the vicinity of the town of Gubkin is the earliest species
erected on tooth plate material.
Apart from the holotype (collected by E. B. Ivashintsova
and Yu. V. Starikov), 2 palatine and 3 mandibular tooth plates, the Stoylo
and Lebedi quarries.
Lebediodon , gen. nov.
Lebediodon oskolensis sp. nov., Cretaceous
(Late Albian-Cenomanian); Belgorod Region, Russia.
Vomerine plates are small; the distance between the labial and
lingual edges is short. The tooth plates are thin and bear a deep symphyseal
surface, as well as a small projection at the labial margin situated quite
far from the symphyseal area. A faintly expressed gentle crest runs across
the oral surface posteriorly from this projection. The anterior internal
tritor is situated at the tip of the symphyseal projection and consists
of several vertical tubes disposed in a short longitudinal row. The anterior
external tritor is composed of similar tubes also forming the same kind
of row. A row of separate tritoral tubes, up to 33 in number, runs practically
without interruption along the whole of the labial margin. The descending
lamina is quite short and the pocket posterior to it is very shallow.
The parasymphyseal furrow on the basal side is almost unexpressed. The
palatine tooth plates are long (anteroposteriorly), rather thin and possess
a wide symphyseal surface; the plane of the latter forms an obtuse angle
with the oral side of the tooth plate. The anterior internal tritor dominates
the others; it is very narrow, and it extends a long distance close to
the symphyseal edge of the oral surface. The external tritor partly occupies
a small projection of the labial edge anteriorly. The latter is also very
narrow; it turns posteriorly into a set of isolated tubes occupying a
rather long labial cutting edge. The descending lamina on the basal side
is short, oblique and is accompanied by a shallow pocket. It crosses a
wide and shallow longitudinal parasymphyseal furrow. The mandibular tooth
plates are strongly elongated; the distance between the labial and lingual
edges is short. The anterior external and posterior internal tritors are
very narrow; a gentle longitudinal low ridge runs posteriorly from the
latter. The anterior tritor represented by a row of isolated tubes follows
the cutting edge. The external posterior tritor consists of a row of isolated
tubes. The symphyseal surface is narrow.
The new genus differs from Rhinochimaera Garman
1901  by the presence of tritors on the labial margin of the
tooth plates; from Neohariotta Bigelow and Schroeder 1950
[11, fig. 4] by the presence of only two, not three or four, longitudinal
tritor lines and the absence of a deep longitudinal furrow on the oral
side of the palatine tooth plate; from Hariotta Goode and
Dean 1895 [8, Pl.5; 12, fig. 1F; 13, fig. 2; Pl. 1B] by a considerably
narrower posterior internal tritor on the mandibular tooth plate.
Lebediodon oskolensis sp. nov.
The generic name originates from the former Lebedi village and
the specific one from the Oskol River.
TsNIGR museum N 6/12963, a left palatine tooth plate (Fig. 1-5),
Stoylo quarry; Cretaceous (Upper Albian-Cenomanian).
A shallow longitudinal furrow runs along the symphyseal
margin on the basal surface of the palatine tooth plate (Fig. 1: 6). Incremental
lines on the oral surface (Fig. 1: 6A) are inclined at about 40 degrees
to the symphyseal margin. There may exist a point (single tube) median
tritor (specimen no. 8/12963). The anterior external and anterior internal
tritors of the vomerine tooth plate consist of 2-5 tubes each. The symphyseal
surface of the mandibular tooth plate bears one to two longitudinal grooves
(Fig. 1: 7). The descending lamina is not expressed on the basal surface
of the mandibular plate (Fig. 1: 7).
The individual body size was small. The dentition is sectorial.
Only about 2.1% of the chimaeroid tooth plates from the localities near
the town of Gubkin belong to Lebediodon . The vomerine tooth
plates of L. oskolensis are somewhat similar to the presumed
mandibular of Elasmodectes willetti (NEWTON 1878) from the
Upper Cretaceous of England; (this tooth plate may turn out to be a vomerine
and belong to Rhinochimaeridae). However, in contrast to E. willetti
, in L. oskolensis the anterior internal tritor is short
and the anterior external one is elongated longitudinally.
The Ischyodus sp. cf. I (?) incisus
Newton 1878 tooth plates from the Albian-Cenomanian near the town of Gubkin
(12 tooth plates) differ from L. oskolensis by the presence
of a well defined, although narrow, posterior external tritor on the mandibular
plate. This tritor in L. oskolensis disintegrates into a
set of "point" tritors [tritoral rods]. The tooth plates of L.
oskolensis differ from those of I. (?) incisus
f rom the Upper Cretaceous of England [4: Pl. 12, fig. 10]
not only by having these tritoral rods instead of an anterioposteriorly
elongated posterior external tritor but also by lacking a descending lamina
on the mandibular tooth plate.
Three palatine, 9 vomerine and 20 mandibular tooth plates from
the Lebedi and Stoylo quarries.
Stoilodon , gen. nov.
Stoilodon aenigma sp. nov., Cretaceous (Late
Albian- Cenomanian) of the Belgorod Region, Russia.
Presumably vomerine or, less probably, mandibular tooth plates
possess no tritors, with the exception of tritoral rods exposed as "points"
at the cutting edges. The plates possess a very long, narrow parasymphyseal
process, as well as a narrow second one strongly projecting anteriorly
and situated at the labial edge of the tooth plate. These projections,
when viewed from the oral surface, are separated by a very deep labial
notch, the angle between its margins being less than 90 degrees. The tooth
plate margin between the projections mentioned above and laterally from
the second projection is sectorial. The symphyseal surface is deep and
significantly flattened. The descending lamina is absent.
The genus differs from other known Rhinochimaeridae [8; 11;
12] by its very large size, strongly expressed labial projections
on the vomerine (?) tooth plate and the deep notch between these projections.
Stoilodon aenigma sp. nov.
From the former Stoylo village and aenigma (Latin)
- a puzzle.
Holotype: TsNIGR museum, N 10/12963; a left vomerine (?) tooth plate (Fig.
2: 1), the Stoylo quarry; Cretaceous (Upper Albian- Cenomanian).
The tooth plates are large. A short anterior part of the
symphyseal surface probably includes a contact area for the counterpart
tooth plate. The angle between the symphyseal plane and the labial edge
of the parasymphyseal projection of the holotype (Fig. 2: 1) is approximately
30 degrees, whereas in two other specimens (N11/12963 and N12/12963) it
is close to 35 degrees; the angle between the edges of the labial projection
is approximately 50 degrees and the edges of the labial notch diverge
58-60 degrees. The unworn part of the oral surface of the tooth plate
has incremental lines resembling gentle folds which follow an arch-shaped
course from the symphyseal region toward the labial surface and somewhat
backwards. Those folds are crossed by equally gentle folds and striations
situated parallel to the symphyseal margin. The wear surface in the area
of the labial notch occupies slightly less than a third of the distance
from this notch to the lingual tooth plate margin. The lateral region
of the tooth plate (specimen N11/12963) bears a short obtuse lateral margin
and a sharpened edge with a narrow wear surface. A narrow shallow groove
runs along the lower edge of the symphyseal surface at approximately 1/6-1/8
of its depth. Two wide striated stripes parallel to the symphyseal margin
are situated on the basal surface of the tooth plate (Fig. 2: 1b) in the
symphyseal area and immediately lateral to the labial projection. The
width of the medial stripe constitutes approximately 2/5-3/5 of the width
of the area between the symphyseal plane and the labial notch. Sigmoid-shaped
incremental lines running parallel to the lingual edge form a prominent
ornamentation between the above mentioned stripes and also on the lateral
part of the basal surface of the tooth plate. The wear surface is widest
at the parasymphyseal and anterolateral projections on the anterior part
of the basal surface of the tooth plate, and narrowest close to the labial
notch. When viewed from the lingual (posterior) side (Fig. 2: 2) the tooth
plate can clearly be seen to consist of three layers. The basal layer
consists of vascularized pleromin in which the canals, about 0.2-0.3 millimeter
in diameter, are approximately parallel to the symphyseal plane when viewed
from the abrasion surface. The layer close to the oral surface includes
similar canals which are approximately parallel to the incremental lines
on the oral surface of the tooth plate. These canals and those of the
basal layer become significantly narrower at a distance of 1 centimeter
from the lingual margin of the tooth plate. A very thin third layer, situated
between the first two, includes canals 1 mm. in diameter that are slightly
compressed dorsoventrally close to the lingual edge. These canals are
disposed in a single sheet, closely spaced, and oriented in an intermediate
fashion relative to those of the other two layers. When the broken surface
of the tooth plate, which is approximately parallel to the symphyseal
plane, is examined in labial view (specimen N12/12963), it may be seen
that the canals of the intermediate layer become narrower at a distance
of about 1 centimeter in the anterior direction, decreasing to 0.1 millimeter
in diameter; the pleromin around these canals is especially dense and
may be regarded as constituting "point" tritors. This kind of pleromin
forms a cutting edge as the tooth plate wears. It may also be observed
at the broken surface mentioned above that the canals in the upper layer
of the tooth plate are also directed from the oral surface anteriorly
and towards the intermediate layer, while the ones in the basal layer
are directed from the basal surface anteriorly and towards the intermediate
layer. This orientation of the canals probably provided self-sharpening
of the labial edge as wear occurred parallel to the canals simultaneously
from the oral and basal sides. Similar "point" tritors [tritoral rods]
are also found on the labial edges of the tooth plates in Rhinochimaera
If all the collected tooth plates of S. aenigma
are really vomerine, ---and the vomerine in Rhinochimaera
does have a labial notch , although not as deep as the one in Stoilodon---
then, on the basis of the vomerine tooth plate/ body length ratio in Rhinochimaera
, the body length in Stoilodon from the mouth opening to
the tip of the tail could have attained 5 meters. Nevertheless, in Stoilodon
the proportion of the body length to that of the vomerine tooth plate
could differ from that of the Recent Rhinochimaera . Even
so, it is apparent that Stoilodon was one of the largest
species in the assemblage of fishes from the vicinity of the town of Gubkin.
The dentition of this fish was specialized to cut soft tissues, an action
facilitated by the strongly sharpened labial edge of the tooth plate and
also by the prongs on either side of the notch. This species was very
rare: its remains constitute only about 0.26 % of all tooth plates found.
Stoilodon aenigma and Lebediodon oskolensis
are probably the earliest known members of the Rhinochimaeridae.
Four vomerine (?) tooth plate fragments, Stoylo quarry.
Genus Amylodon Storms 1895
Amylodon emba sp. nov.
Species name from the Emba River near which the holotype
Holotype: TsNIGR museum N 13/12963, a left palatine tooth plate (Fig.
2: 3), Kolenkaly Mts., Aktyubinsk Region, Kazakhstan; Paleogene, Middle
Oligocene, beds containing Pinna .
Anterior and posterior internal tritors are found on the
narrow palatine tooth plate; the posterior one consists of two parallel
"columns" (Fig. 2: 3).
A large posterior internal tritor, but one that is not
divided into two parts, is present in A. venablesae Casier
1966 from the Lower Eocene of England  and in A. delheidi
Storms 1895 from the Lower Oligocene of Belgium . In A.
eocenica (Woodward and White 1930) from the Eocene of England
 and Amylodon sp. nov. from the Upper Cretaceous
of the Volgograd Region, the posterior internal tritor is completely absent.
The new species from Kazakhstan differs from all known Amylodon
species by its relatively much narrower palatine tooth plate.
Genus Belgorodon , gen. nov.
"Chimaera " bogolubovi Nessov
1986; Cretaceous (Late Albian-Cenomanian); Belgorod Region, Russia.
The distance between the labial and lingual margins of
the palatine and mandibular tooth plates is small, but it is much larger
between the symphyseal and lateral margins. There are two to three long
bar-like tritors on the palatine tooth plate anteriorly; the external
tritor is long and undivided; the posterior internal and median ones are
small and widely separated; the median tritor is close to the external
one. The mandibular tooth plate has a narrow symphyseal margin. This tooth
plate is rather thin in its symphyseal part but is strongly thickened
more laterally where the narrow, longitudinally elongated anterior external
and posterior internal tritors lie close to one another or interconnect.
The anterior [parasymphyseal] tritor is large and has a long narrow
projection extending laterally along the labial margin. The posterior
external tritor is small and short; sometimes it becomes subdivided into
two or three parts.
Belgorodon differs from Chimaera
L., 1758 and Hydrolagus Gill, 1862 [3,6,9,14,16]
in having smaller posterior internal and median tritors on the palatine
tooth plate; the extent of its anterior tritor; the smaller length and
larger width of the tooth plate itself; and the presence of a strong swelling
along the main tritoral zone on the mandibular plate.
The new species is similar to Elasmodectes
Woodward 1888 [4, 14] in the small depth of the symphyseal surface
of the mandibular tooth plate, but differs in the presence of the posterior
internal tritor and the strong swelling of the tooth plate in the area
of this tritor and the anterior external tritor.
Belgorodon bogolubovi (Nessov 1986)
"Chimaera " bogolubovi : NESSOV et al., 1986,
p. 128, Text-fig. 1, fig. 3.
The generic name after the Belgorod Region in which the material
was found; the specific one after N.N. Bogolyubov.
Holotype: TsNIGR museum, N 3/12292, a left palatine tooth plate ,
Lebedi quarry; Cretaceous (Upper Albian-Cenomanian).
The basal surface of the palatine dental element (Fig. 2: 4)
bears a short subtransverse descending lamina in the wide parasymphyseal
furrow; the symphyseal surface is deep. The median tritor on this tooth
plate has a posterolateral projection. The wear surface on the palatine
(Fig. 2: 4) and the mandibular (Fig. 2: 5) tooth plates occupies about
half of the length of the plate, measured rostrocaudally.
Belgorodon bogolubovi is probably
the earliest member of the modern family Chimaeridae. Belgorodon
remains constitute 0.46 % of the tooth plates collected.
Three palatine and four mandibular tooth plates; Lebedi and Stoylo
Only 3.35 % of all the tooth plates from the chimaeriform fishes
that inhabited the territory of the Belgorod Region about 105-99 million
years ago can be assigned to the modern families Callorhynchidae, Rhinochimaeridae
and Chimaeridae; the rest belong to the family Edaphodontidae (the dominant
genus Ischyodus and Edaphodon ). A trend in
callorhynchid evolution from the Cretaceous to the present time seems
to be the decrease in tritoral material on the mandibular plates. A similar
trend in all components of the dentition was expressed especially in rhinochimaerid
history. The comparison of the Albian-Cenomanian genus Belgorodon
to the extant Chimaera demonstrates that a similar tendency
was present in chimaerid evolution as well.
Cretaceous chimaeroids Callorhinchus borealis , sp. nov.
(the most ancient Callorhynchidae known from dental plates), Lebediodon
oskolensis , gen. et sp. nov., Stoilodon aenigma ,
gen. et sp. nov. (the oldest forms of Rhinochimaeridae), Belgorodon
bogolubovi (Nessov 1986) gen. nov., (the most ancient member of
the Chimaeridae) and Oligocene Amylodon emba , sp. nov. (Edaphodontidae)
1. NESSOV, L.A. and A.O. AVERIANOV 1996. Ancient chimaeroid fishes of
Russia, Ukraine, Kazakhstan and Central Asia. I. Some ecological characteristics
of chimaeroids and a summary of their occurrence. Bull. St. Petersburg
Univ., ser. 7, no. 7, pp. 11-19.
2. NESSOV, L.A., R.A. MERTINIENE, L.B. GOLOVNEVA et al. 1986. New finds
of the ancient organisms' remains in the Belgorod and Kursk regions. In:
Comprehensive studies of the biogeocenoses of the wood-steppe oak forests,
pp. 124-131 (Leningrad St. Univ. Publishers) Leningrad (St. Petersburg).
3. PATTERSON, C. 1992. Interpretation of the tooth plates of chimaeroid
fishes. Zool. J. Linn. Soc., 106(1).
4. NEWTON, E.T. 1878. Chimaeroid fishes of the British Cretaceous rocks.
Mem. Geol. Surv. U.K., Monogr. 4.
5. GURR, P.R. 1963. A new fish fauna from the Woolwich Bottom Bed (Sparnacian)
of Herne Bay, Kent. Proc. Geol. Assoc., 73, pt.4.
6. WARD, D.J. 1973. The English Paleogene chimaeroid fishes. Proc. Geol.
Assoc., 84, pt.3.
7. WOODWARD, A.S. and E.I. WHITE 1930. On some new chimaeroid fishes from
Tertiary formations. Ann. Mag. Nat. Hist., Ser. 10, 6(35).
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Mull., 1834), especially Rhinochimaera and its allies. Bull.
Mus. Comp. Zool., 41(2).
9. DIDIER, D.A., B.J. STAHL and R. ZANGERL 1994. Development and growth
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fishes. Pt. VI: The jaw mechanism and feeding of the holocephalan, Callorhynchus
capensis Dumeril. Zool. Africana, 6(1).
11. BULLIS, H.R. and J.S. CARPENTER 1966. Neohariotta carri
---a new species of Rhinochimaeridae from the southern Caribbean Sea.
Copeia, No. 3.
12. GARRICK, J.A.F. 1971. Hariotta raleighana , a long-nosed
chimaera (family Rhinochimaeridae), in New Zealand waters. J. Roy. Soc.
New Zealand, 1, No.3/4.
13. WERDELIN, L. 1986. A new chimaeroid fish from the Cretaceous of Lebanon.
Geobios, No. 19, fasc.3.
14. WOODWARD, A.S. 1891. Catalogue of the fossil fishes in the British
Museum (Natural History), Pt. 2. London.
15. CASIER, E. 1966. Faune ichthyologique du London Clay. London.
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Fig. 1. Tooth plates of chimaeriforms Callorhynchidae (1-4)
and Rhinochimaeridae (5-7) from the Upper Albian-Cenomanian of the Belgorod
Region, Russia. (1: 4) Callorhinchus borealis sp. nov.: (1)
a left vomerine tooth plate: 1a- from below, 1b- in anterior view; (2)
a left palatine tooth plate from below; (3) a right palatine tooth plate
(holotype): 3a- from below, 3b- in anterior view, 3c- in posterior view;
(4) a left mandibular tooth plate: 4a- from above, 4b- in anterior view;
(5-7) Lebediodon oskolensis gen. et sp. nov.: (5) a right
vomerine tooth plate: 5a- from below, 5b- in anterior view, 5c- from above;
(6) a left palatine tooth plate (holotype): 6a- from below, 6b- in anterior
view; (7) a left mandibular tooth plate: 7a- from above, 7b- in anterior
view. Scale bar: 1 centimeter. Dotted lines indicate the approximate position
of the symphyseal plane (also in Fig. 2).
Fig. 2. Chimaeriform tooth plates of the families Rhinochimaeridae (1,
2), Edaphodontidae (3) and Chimaeridae (4, 5) from the Upper Albian-Cenomanian
of the Belgorod Region, Russia (1, 2, 4, 5) and the Oligocene of the Aktyubinsk
Region, Kazakhstan (3). (1, 2) Stoilodon aenigma gen. et
sp. nov.: (1) a right vomerine tooth plate (holotype): 1a- from below,
1b- from above, outline reconstructed after specimen no. 12/12963, 1c-
in anterior view; (2) a left vomerine tooth plate (specimen no. 12/12963)
in posterior view (broken line inside tooth plate image shows the position
of an intermediate layer of dentine); (3) Amylodon emba sp.
nov., a right palatine tooth plate (holotype): 3a- from below, 3b- in
anterior view; (4, 5) Belgorodon bogolubovi (Nessov): (4)
a left palatine tooth plate: 4a- from below, 4b- the medial part of the
tooth plate from above, 4c- in anterior view; (5) a left mandibular plate:
5a- from above, 5b- from below.