Short note on the first record of fossil shark teeth in the Chehel-Kaman Formation, Iran

. Shark teeth discovered in the late Paleocene-early Eocene Chehel­ Kaman Formation in NE Iran bring new data on the fossil fish record from this country. Two genera from the location are described and figured. The present record is one of the very few reports of fossil shark teeth from the Cenozoic of Iran and the first one from this formation and region. The marine vertebrates known from this region of the Tethys Sea are very scarce.


Introduction
The Cenozoic fossil sharks are poorly known in Iran. Only a few other records from this country are known (A dnet

Geological Setting
The study area is located in the North-Khorasan province, n o rth east Iran (Fig. 1)  Like other regions of Iran, tectonical m ovements in the early Tertiary, equal to Laramian orogenesis, led to sea retrograd ation from south to north in such a way that a continental succession (Pestehligh Form ation -Early Paleocene) is deposited in the south o fth e Kopet-Dagh sedim entary basin. During the middle Paleocene, except for the Sheikh area, a fossiliferous lim estone (Chehel-Kaman Form ation) is deposited because of the subsidence of the basin. During early Eocene the Sheikh area was also covered, so the m arine Eocene strata are p resent (Khangiran Form ation) (A fs h a r-H a rb , 1 9 94, A gh ana b a ti, 2 0 0 4 ) (Fig. 2).
The Chehel-Kaman Form ation (Paleogene) in the Kopet-Dagh basin is mainly com posed of lim estone, dolomite and interbeds of marl, shale and evaporite sedim ents. It conform ably overlies the siliclastic sedim ents of Pestehligh Form ation and underlies the olive shale of Khangiran Formation. The upper contact is m arked by a coquina bed that is taken as base of the Khangiran Formation. In the upper part, the lim estone contains echinoids, gastropods and large oysters. The Chehel-Kaman Form ation is named after the Chehel-Kaman locality in the Sarakhs area, southeastern Kopet-Dagh. This name is used by the geologists of the National Iranian Oil Company (NIOC) (A f s h a r -H a r b , 1 9 6 9 ) . The nam e has been used to designate a unit o f dense or chalky, massively bedded, ridge-form ing organodetrital lim estone developed in the eastern Kopet-Dagh sedim entary basin. In som e other localities (such as Gonbadli oil well no. 3) there are some layers of sandstone as well as gypsum beds. In the type area (Che-
Bart.  The locality from which the sam ples containing the shark teeth w ere collected is named "Behkadeh stratigraphic section" and is located about 2.5 km northw est of the Behkadeh village. At the Behkadeh stratigraphic section, the Chehel-Kaman Form ation is about 12 m thick. It is overlaid by the Quaternary deposits and underlaid unconform ably in som e areas by the Sanganeh and in som e other areas by the Aitamir form ations (Fig. 3). The Chehel-Kaman Form ation starts with a light grey sandy lim estone which is rich in bivalve rem ains and continues with medium to thick-bedded fossiliferous lim estone accom panied by thick-bedded w hite to grey sandy lim estone. For the purpose of understanding the exact biostratigraphic position of the strata, we collected lim estone samples. Micropaleontological investigations led to the identification of the following foraminifera assem blages, with an age ranging from the late Paleocene to the early Eocene:

Materials and methods
The material comprises 18 specimens, only eight of vvhich could be determined systematically. All of the studied samples, hand-picked by the authors, are housed in the inventory system of the Geological Survey of Iran and Geosciences Research Center, NE Territory, Geoscience Museum of Mashhad (Jafar Taheri collection), with the GMM (Geoscience Museum of Mashhad] prefix, under the official depository numbers GMM97FT0246, GMM97FT0248, GMM97FT0252, GMM97FT0254, GMM97FT0261, GMM97FT0262 and GMM97FT0263. The pictures were taken by using a Canon EOS 80D and a tripod. For the systematics we follow C a p p e t t a (2012) and   D e scrip tio n . The material includes both anterior and lateral teeth. Anterior main cusps are long, slender, with a convex lingual side and a flat or almost flat labial side. The main cusps representing lateral teeth are smaller, distally inclined and labio-lingually compressed. All the teeth have well marked cutting edges. Only one specim en (G M M 97FT0246, Fig. 4, m -o) preserves the root and the lateral cusplets. Its main cusp is long and slender, with faint striations on the lingual crown face. The tooth preserves a partial root and the lateral cusplets. The cutting edge does not reach the base of the crown. The lateral cusplets are divergent, reduced and circular in cross-section view. The root is bilobate, the lobes m eet in an acute angle, forming a strong lingual protuberance. The ends of the lobes are broken and we cannot observe if they are round or sharp. D iscu ssio n s. The described morphology of our specim ens corresponds well with the descriptions of the Striatolamia genus (C ap p etta, 2 0 1 2 , p. 189; Z helezko & Kozlov, 1 9 9 9 , p. 1 2 8 ). Taking into consideration th at our specim ens com e from a Paleocene-E ocen e form ation, we com pared our specim ens w ith the th ree valid species of Striatolamia from this interval, S. cederstroem i, S. striata and S. macrota. We found that Striatolamia macrota can be easily distinguished from the Paleocene species S. cederstroemi by the different morphology of the lateral cusplets. In S. cederstroemi these lat-eral cusplets are flat, labio-lingually com pressed even in the an terior teeth w hile in S. macrota are cone like, low and pointed (Siverson, 1995, p. 9). The distinction betw een S. macrota and S. striata is more difficult to make. The description of S. striata (Capp etta ,19 8 7 ,p. 88; Herman, 1 9 7 7 , p. 2 3 9 ) indicates that the striations on the lingual face are in general m ore pronounced than in S. macrota and the lateral denticles of the anterior teeth are barely perceptible. The size is also indicated as a differentiating characteristic (Herm an, 1 9 7 7 ; N olf, 1 9 8 8 ), but without a certain threshold. It is likely th at S. striata evolved into S. macrota increasing in size and reducing the striations o f the m ain cusp's lingual face.
Considering the very small differences betw een S. macrota and S. striata and the large tim e interval included in the Chehel-Kaman Form ation we assign our specim ens only to the genus level.  The tooth is incom plete, with the apex of the main crown missing and only one half of the root and one lateral cusplet preserved. The crown of the tooth is convex on the lingual side and flat on the labial side with a well marked basal depression. Both crown faces are com pletely smooth. The cutting edge reaches the base of the crown and the base o fth e lateral cusplet. In lateral view we can notice th at the main cusp is arched lingually. The only preserved cusplet is sharp, convergent and strongly ben t lingually. The preserved root lobe is m oderately long, has a rounded end and m eets with the rest of the other lobe in an acute angle. The central furrow cannot be observed due to the hardened sedim ent still present on the tooth. family Odontaspididae. These genera w ere reported from the Thanetian-Ypresian interval and have a sim ilar general morphology. From the beginning we excluded som e of them based on the characteristic defined by the extension of the cutting edge along the crown of the tooth. Thus we excluded the Carcharias and Odontaspis genera in which the cutting edge does not reach the base of the crown in the ante rio r teeth (C ap p etta & N olf, 2 0 0 5 ). We also excluded the Glueckmanotodus genus w here the cutting edge reaches the base of the crown but the cusp has a torsion on the vertical axes. The lobes of the root are sharply pointed in Glueckmanotodus (Z h elezko & Kozlov, 1 9 9 9 , p. 11 4 ; C appetta & N olf, 2 0 0 5 , p. 2 4 3 ), differing from our specim en. The Brachycarcharias genus was also excluded. This genus has short folds of the enam el on the lingual face and the lateral cusplet is aligned with the cutting edge of the crow n (C ap p etta & N olf, 2 0 0 5 , p. 2 4 1 ), both characteristics missing in our case. A distinction can also be made in regards to the Hypotodus genus, w hich has a labial base of the crown slightly convex in the contact region with the root (C ap p etta & N olf, 2 0 0 5 , p. 2 4 4 ), som etim es with a small sh o rt basal m edian ridge (C a rls e n & Cuny, 2 0 1 4 , p. 57).
Facies analyses, biostratigraphy and radiometric dating ofthe Lovver-Middle Miocene succession near Zaječar (Dacian basin, eastern Serbia) The described morphology of our specimen corresponds with the descriptions and illustrations of the various species in th eJaekelotodus genus (Cappetta , 2 0 12 , p. 199; Eckhaut & De S c h u tte r , 2 0 09, p. 45).

Results and discussion
Both genera figured and described here are very common around the world and have a sim ilar stratigraphic distribution. Striatolamia can be found from the Lower Paleocene (M U ller, 19 9 2 ; D u th eil, 1992] up to the Priabonian (C appetta, 2 0 1 2 ] while Jaekelotodus was described from the Danian to Priabonian (Cappetta, 20 1 2 ). Taking into account the paleogeography of the low er p art of the Eocene (Fig. 1), we consider th at the Behkadeh area still has potential for other taxa finds. The lower Eocene rich fauna of the close-by Caspian Sea area is well known to researchers (Glikman, 1 9 6 4 ; King et al., 2 0 1 3 ), so we expect th at future studies will im prove the fauna list.
The white colour of som e of the specim ens indicates th at the teeth w ere exposed to sunlight and acidic environm ent (acid precipitations or acids of the soil) for a long time. Considering th at the m aterial com es from surface finds, from a taphonom ic point of view we cannot make too many com ments, the fragm entation of the teeth could be entirely the result of recen t processes. This is the first report of shark teeth in this area