Hooked Mako Isurus planus (Agassiz, 1856) from the Miocene of Sakhalin

2013·1.5 MB·

by  M. V. Nazarkin

ZOOSYSTEMATICA ROSSICA, 22(2): 311–314 25 DECEMBER 2013
Hooked Mako Isurus planus (Agassiz, 1856)
from the Miocene of Sakhalin
Крючкозубый мако Isurus planus (Agassiz, 1856)
из миоцена Сахалина
M.V. NAZARKIN
М.В. НАЗАРКИН
M.V. Nazarkin, Zoological Institute, Russian Academy of Sciences, 1 Universitetskaya Emb., St Petersburg, 199034,
Russia. E-mail: [email protected]
An isolated upper lateral shark tooth from the Middle-Late Miocene Kurasiiskaya Formation,
Sakhalin Island, Russia, is identified as an Isurus planus (Agassiz, 1856). This is the first record
of hooked mako for Russia, and the northernmost finding of this fossil shark.
Сообщается о находке верхнего бокового зуба крючкозубого мако Isurus planus (Agassiz,
1856) в отложениях среднего-позднего миоцена острова Сахалин (курасийская свита).
Это первая находка данного вымершего вида в России и наиболее северная точка его
обнаружения.
Key words: Miocene, Sakhalin, fossil sharks, Isurus planus
Ключевые слова: миоцен, Сахалин, ископаемые акулы, Isurus planus
INTRODUCTION meters south from the settlement of Pen-
zenskoye and about two kilometers north
Finding of ancient chondrichthians in-
from the mouth of the Cherepok River (To-
cluding selachians are uncommon fossils in
mari District, Sakhalin Province).
the Paleogene and Neogene strata of the Far
The cliff exposed clayish aleurolites and
East of Russia. Teeth of fossil sharks in this
siliceous soapstones with layers of sand-
territory are found on rare occasions. The
stones and diatomites. These beds belong to
number of the shark’s remains, which have
Kurasiiskaya Formation which are common
been collected from each known locality,
along the southwestern coast of the Sakha-
doesn’t exceed one tooth. That’s why any
lin Island in the Tomari District (Savitskyi,
new data on the Tertiary sharks from this
1982). The deposits of this formation con-
wide territory are of special importance.
tain rich complexes of bivalves, foramini-
During the field season in 2013 one lateral
fers, and mesopelagic and neritic teleoste-
tooth of lamnid shark was collected in the
ans. Based on the analysis of fossil bivalves
Middle-Late Miocene deposits of south-
and foraminifers, a conclusion was made
western Sakhalin Island. Below, this finding
that these fossiliferous beds were formed in
is described in details.
comparatively deep marine environments in
the Middle-Late Miocene (Savitskyi, 1982;
LOCALITY, MATERIAL
Zhidkova, 1986; Gladenkov et al., 2002).
AND METHODS
The beds of this formation were deposited
The fossil tooth was found on a coastal during the largest Cenozoic sea transgres-
cliff of the Tatar Strait (47°52´9.48´´N sion in the Far East of Russia (Gladenkov
142°05´44.34´´E) located about five kilo- et al., 2002).
© 2013 Zoological Institute, Russian Academy of Scienсes
312 M.V. NAZARKIN. HOOKED MAKO SHARK FROM NEOGENE OF SAKHALIN
Tooth preparation was made by needles tive foramina, most of them being concen-
under binocular microscope. Measurements trated at the central part of the root.
follow Glickman (1964: 47, fig. 24) to fa- Measurements (in mm): maximum
cilitate comparison; the tooth proportions tooth height 41.6; maximum tooth thick-
follow Shimada (2005). Maximum tooth ness (wr in Glikman, 1964) 34.2; lingual
height was calculated using a tooth imprint. crown height (hcr) 30.6; crown thickness
The material is deposited in the fish collec- at base (wcr1) 33.0; crown thickness (dcr)
tion of the Zoological Institute of Russian 8.8; neck height (hz) 1.5; root thickness
Academy of Sciences, St Petersburg (ZIN). (dr) 9.9; root height (hr) 14.0. The crown
acuteness 0.86; the tooth inclination 1.58;
SYSTEMATIC PART the crown height/ basal crown width ratio
0.94.
Order LAMNIFORMES Berg, 1958
Family LAMNIDAE Bonaparte, 1837 DISCUSSION
Genus Isurus Rafinesque, 1810 Species identification. This fossil tooth
Isurus planus (Agassiz, 1856) possesses smooth cutting edges, smooth
(Fig. 1) labial and lingual coronal faces, lacks lat-
eral cusplets; its central foramen does not
Material. ZIN 55411, left upper lateral tooth. open into a well-defined transverse groove;
Coastal cliff of Tatar Strait about five kilometers root lobes are not round and not extend-
south of the settlement of Penzenskoye, Tomari
ing noticeably beyond the basal limit of the
District, Sakhalin Province, Russia; Kurasi-
crown. These characters clearly indicate
iskaya Formation, Middle-Late Miocene; coll.
that the tooth belongs to a shark of the ge-
M.V. Nazarkin, Aug. 2013.
nus Isurus (for Isurus, see Cappetta, 1987;
Description. The tooth with a single cusp;
Pardy et al., 2001; Pardy, 2006). Within
lateral cusplets are absent (Fig. 1). There are
enameloid shoulders instead of cusplets on the genus, the fossil tooth is very similar to
each side of the cusp which somewhat hangs a lateral teeth of hastalis / planus species
over the root branches. The crown is wide, group because of its triangular shape, the
triangular and flattened labiolingually, con- wide and totally labiolingually flattened
siderably inclined distally. The medial edge crown, and the comparatively large size. Fi-
of the crown is convex; the distal edge is nally, the root apexes of the tooth are round
mostly straight, but considerably concave and the crown is considerably inclined dis-
at the crown base. The enameloid is com- tally. These features are more characteristic
pletely smooth, without ornamentation. of I. planus rather than I. hastalis which pos-
The labial crown surface is nearly flat; the sesses square root apexes and a straighter
lingual surface is slightly convex. The labial crown (Kuga, 1985; Karasawa, 1989). This
crown surface with a shallow concavity from fossil tooth most probably represents an up-
the base of the crown to about two-third of per lateral tooth because, in Isurus species,
its height. The cutting edges are complete, the depression between the root branches
without serration, and almost reach the is usually smaller in an upper lateral tooth
root. The tooth neck is very thin. The root than in a lower lateral tooth.
is massive, wide and flat; without any pro- Geographic and stratigraphic distribution.
tuberance. Root edges are roundish, slightly Two recent species of the genus Isurus are
extend out of the crown margins. The root widely distributed in temperate and tropi-
branches are merged and poorly divided by cal waters of the World (Compagno, 1984;
a small depression; distal branch is 1.2 times 2002). Fossil records of mako sharks are
wider than the medial one. The nutritive known starting from the Early Paleocene of
groove is absent; there are eight small nutri- Mexico (Gonzalez-Rodriguez et al., 2013).
© 2013 Zoological Institute, Russian Academy of Scienсes, Zoosystematica Rossica 22(2): 311–314
M.V. NAZARKIN. HOOKED MAKO SHARK FROM NEOGENE OF SAKHALIN 313
Fig. 1. Isurus planus, ZIN 55411: labial (a), mesial (b) and lingual (c) views, (d) – an imprint of the
labial tooth side. Scale bar: 10 mm.
This group apparently reached the greatest cene of Australia (Kemp, 1991), and from
species variety during the Middle Miocene. the Middle to Late Miocene of California
In the deposits of that time of the Pacific (USA) (Agassiz, 1856; Jordan & Hannibal,
Rim six species of Isurus in Japan (Kuga, 1923), Mexico (Gonzalez-Rodriguez et al.,
1985; Yabumoto & Uyeno, 1994) and five 2013) and Japan (Karasawa, 1989; Kuga,
species in Mexico (Gonzalez-Rodriguez et 1985; Yabumoto & Uyeno, 1994; Takakuwa
al., 2013) were found. Unlike other fossil et al., 2009). This species is one of the com-
species of this genus, which were cosmopol- mon fossil sharks in Japan (Kuga, 1985) but
itan, distribution of I. planus was apparently it was thus recorded for the first time in
limited by the Pacific Ocean (Kuga, 1985). Russia. This finding from the Sakhalin rep-
For the present, it has been known since resents the northernmost known locality of
the Late Oligocene until the Middle Mio- occurrence of I. planus.
© 2013 Zoological Institute, Russian Academy of Scienсes, Zoosystematica Rossica 22(2): 311–314
314 M.V. NAZARKIN. HOOKED MAKO SHARK FROM NEOGENE OF SAKHALIN
ACKNOWLEDGEMENTS (eds.). Mesozoic Fishes 5 – Global Diversity
and Evolution: 9–34. München: Verlag Dr.
The author is grateful to Tatyana Malyshki- Friedrich Pfeil.
na (Zavaritskii Institute of Geology and Geo- Karasawa H. 1989. Late Cenozoic Elasmo-
chemistry, UB RAS) for reading the manuscript branchs from the Hokuriku district, central
and valuable comments. Many great thanks go Japan. The science reports of the Kanazawa
to Alexander Averianov (Zoological Institute University, 34(1): 1–57.
RAS, Saint Petersburg, Russia) and Yoshiaki Kemp N.R. 1991. Chapter 15: Chondrichthyans
Kai (Kyoto University, Japan) for their help in the Cretaceous and Tertiary of Austra-
with the literature. This study was supported lia. Vertebrate Palaeontology of Australasia:
by the Russian Foundation for Basic Research 497–568.
(11-04-00001а). Kuga N. 1985. Revision of Neogene mackerel
shark of genus Isurus from Japan. Memoirs
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