- Email: [email protected]
Two new mammal localities within the Lower Cretaceous Ilek Formation of West Siberia, Russia
Accepted Manuscript Title: Two new mammal localities within the Lower Cretaceous Ilek Formation of West Siberia, Russia Author: Alexander Averianov Alexey Lopatin Pavel Skutschas Sergey Leshchinskiy PII: DOI: Reference:
S0016-6995(15)00015-7 http://dx.doi.org/doi:10.1016/j.geobios.2015.02.004 GEOBIO 700
To appear in:
Geobios
Received date: Revised date: Accepted date:
10-10-2014 3-1-2015 3-2-2015
Please cite this article as: Averianov, A., Lopatin, A., Skutschas, P., Leshchinskiy, S.,Two new mammal localities within the Lower Cretaceous Ilek Formation of West Siberia, Russia, Geobios (2015), http://dx.doi.org/10.1016/j.geobios.2015.02.004 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Two new mammal localities within the Lower Cretaceous Ilek Formation of West Siberia, Russia Alexander Averianov a,b,*, Alexey Lopatin c, Pavel Skutschas b,d, Sergey Leshchinskiy b
Zoological Institute of the Russian Academy of Sciences, Universitetskaya nab. 1, 199034
ip t
a
Saint Petersburg, Russia
Laboratory of Mesozoic and Cenozoic Continental Ecosystems, Tomsk State University,
cr
b
c
us
Prospekt Lenina 36, 634050 Tomsk, Russia
Borissiak Paleontological Institute of the Russian Academy of Sciences, Profsoyuznaya 123,
Vertebrate Zoology Department, Saint Petersburg State University, Universitetskaya Nab.
7/9, 199034 Saint Petersburg, Russia
M
d
an
117997 Moscow, Russia
Corresponding editor: Gilles Escarguel.
Abstract
ce pt
ed
* Corresponding author. E-mail address: [email protected] (A. Averianov).
Two new mammal localities have been discovered in the Lower Cretaceous Ilek
Ac
Formation of West Siberia, Russia, during a field work in 2014. The Smolenskii Yar locality in the Chebula District of Kemerovo Province produced an upper molariform tooth (M2) of a Gobiconodontidae indet. The Ust’-Kolba locality in the Tisul’ District of Kemerovo Province yielded a lower molar (m2) of the zhangheotherian Kiyatherium sp. These are the ninth and tenth Mesozoic mammal localities for Russia. The Kiyatherium-bearing vertebrate assemblage from the Shestakovo 3 and Ust’-Kolba localities is likely to be the youngest within the Ilek Formation, reflecting the time after the extinction of the Tritylodontidae.
Keywords:
1
Page 1 of 16
Mammalia Gobiconodontidae Zhangheotherian Kiyatherium sp. Early Cretaceous Ilek Formation
cr
ip t
Siberia
1. Introduction
us
A rich vertebrate fauna, including various dinosaurs and mammals, have been recovered during the last two decades at Shestakovo 1 and 3 localities from the Lower
an
Cretaceous Ilek Formation in West Siberia (Maschenko and Lopatin, 1998; Alifanov et al., 1999; Tatarinov and Maschenko, 1999; Efimov and Leshchinskiy, 2000; Averianov and Fayngertz, 2001; Averianov and Voronkevich, 2002; Averianov et al., 2002, 2003a, b, 2006;
M
Maschenko et al., 2003; Lopatin et al., 2005, 2009, 2010a, b; Averianov and Lopatin, 2008; Kurochkin et al., 2011; O'Connor et al., 2014; Skutschas, 2014). The Ilek Formation is widely
ed
distributed in West Siberia. Extensive exploration of various outcrops of this formation by the field parties of the Tomsk State University and affiliated colleagues led to the discovery of some other vertebrate localities, but so far only new localities within the Bol’shoi Kemchug
ce pt
River basin, Krasnoyarsk Territory, produced fossil mammals (Leshchinskiy and Fayngertz, 2001; Averianov et al., 2005).
Here we report on the discovery of two new mammal localities from the Ilek Formation in the Kiya River basin, Kemerovo Province, close to the Shestakovo localities
Ac
(Fig. 1; Table 1). Both vertebrate localities, namely Ust’-Kolba and Smolenskii Yar, have been found during prospections in 2000 and 2001 (Leshchinskiy and Fayngertz, 2001). Some additional screen-washing was made at these localities in 2002 and 2005. The first mammal specimens have been found in 2011 after screen-washing of ~230 kg of matrix from Ust’Kolba locality and ~380 kg from Smolenskii Yar locality. These mammal specimens are described herein. The specimens are housed in the collection of the Laboratory of Mesozoic and Cenozoic Continental Ecosystems, Tomsk State University (LMCCE).
2. Geographic and geological setting
2
Page 2 of 16
The Ust’-Kolba locality (GPS coordinates: N 55°52’36.2’’, E 88°19’07.6’’) is a small quarry on the left bank of the Serta River near the Ust’-Kolba settlement, ~2 km upstream from the mouth of the river (Tisul’ District, Kemerovo Province). The visible section (Fig. 1(c)) starts at the altitude of ~187 m and encompass approximately 20 m of fluvial facies of the Ilek Formation. It is dominated by yellowish-green assorted sands with an admixture of pebble and gravel, confined mainly to the bottom of cross-bedded layers and lenses. Pebbles
ip t
and gravel are presented by pellets (up to 0.1 m) of thick clays, silts, and carbonate nodules. Vertebrate fossils (scales, bone fragments, and teeth) are confined mainly to the gravel lenses
cr
at the bottom of the visible part of the section. These sediments represented a relatively high energy condition, but the preservation of the fossils, although fragmentary, indicates that they
us
were not reworked.
The Smolenskii Yar locality (GPS coordinates: N 55°58’23.9’’, E 88°05’35.9’’) is
an
confined to a natural outcrop on the right bank of Serta River, 1 km downstream from the Kursk-Smolenka settlement (Chebula District, Kemerovo Province). The section is similar to that of the Shestakovo 1 locality (Leshchinskiy et al., 1997). Eleven layers can be recognized
M
in the section at the southwest part of the escarpment from the water level (Fig. 1(d); from bottom to top):
ed
1) Yellowish to green, assorted dense sand (> 2.5 m); 2) Green coarse-grained sand with dense pellets of clay, silt and carbonate nodules. The vertebrate fossils (mainly scales, bone fragments, and teeth) are confined to the roof of
ce pt
this layer which has a cross-bedded texture; 3) Yellowish to green, fine-grained dense sand. In some places there are small ripple flow textures. At the top there is a body of dense calcareous sandstone (up to 0.5 m) projecting from the outcrop as a cornice (~3.6 m);
Ac
4) Dark gray compact clay (~0.3 m);
5) Yellowish to green fine to medium-sized dense sand (~0.7 m); 6) Bluish-gray stratified tight siltstone (~2.5 m); 7) Brown-red marly dense clay (~1.5 m); 8) Alternating layers of bluish-gray siltstone and brownish-red clay (~2 m); 9) Yellowish-green, fine-grained sand interbedded with gray siltstone (~5 m); 10) Alternating layers of bluish-gray siltstone and brownish-red clay (> 15 m); 11) Quaternary deposits (subaerial loam, sandy loam, and modern soil) (~1 m); The vertebrate assemblages from both localities are globally similar (Table 1). Most taxa are represented by isolated and usually fragmentary specimens. The most common fossils 3
Page 3 of 16
are fish scales. The salamanders are represented by postcranial elements. The turtles are surprisingly rare in the Ilek Formation, contrasting with the majority of other Cretaceous assemblages; the discussed localities yielded only small fragments of turtle plates likely belonging to the macrobaenid turtle cf. Kirgizemys sp., also known from the Shestakovo 1 locality from the same formation (Averianov et al., 2003a). The lizards and choristoderes are known from jaw fragments and isolated vertebrae; crocodyliforms are known from vertebrae,
ip t
jaw fragments, and teeth. Only two pterosaur teeth have been found, one for each locality.
The dinosaurs are also represented, mostly by isolated teeth. A notable exception (from the
cr
Ust’-Kolba locality) is an elongated posterior caudal vertebra of a derived maniraptoran
theropod, showing a groove along the dorsal side of the neural arch and the ventral side of the
us
centrum. This vertebra may belong to a troodontid, a family also known from the
Shestakovo 1 locality by isolated teeth (Averianov and Sues, 2007). Although the observed
an
differences between the two vertebrate assemblages are likely to be of sampling origin, one important discrepancy seems to be real: teeth of the tritylodontid Xenocretosuchus sp. are quite common at the Smolenskii Yar locality, while they have not yet been found at the Ust’-
M
Kolba locality.
MAMMALIA Linnaeus, 1758
ed
3. Systematic paleontology
GOBICONODONTIDAE Chow et Rich, 1984
Fig. 2(a-d)
ce pt
GOBICONODONTIDAE indet.
Referred specimen: LMCCE 1/2, left M2 missing the mesial cusp B and the mesial root. Smolenskii Yar locality, Chebula District, Kemerovo Province, Russia; Ilek Formation,
Ac
Lower Cretaceous.
Measurements: width = 0.9 mm. Description: Cusp C is about twice lower than cusp A. Cusps are conjoined approximately up to the half of cusp A height. The missing mesial cusp B was evidently more separated from cusp A. In occlusal view, cusp C is transversely narrower than cusp A, while the distal part of the crown is wider than the middle part. There is a slight ectoflexus opposite to cusp A. At this place the labial cingulum is narrower than at its distal part. The tips of cusps A and C and the crest connecting cusp C with the cingulum are worn. The lingual cingulum is highly worn. The unworn distal portion of the lingual cingulum is rather thick. The distal root is robust, short, and mesiodistally compressed, as is typical in Gobiconodon. 4
Page 4 of 16
Remarks: The tooth is an upper molariform because of a complete cingulum around the crown. Comparing with the Mongolian species of Gobiconodon (Kielan-Jaworowska and Dashzeveg, 1998; Lopatin and Averianov, 2015), the tooth is an anterior molariform (M1 or M2) since the main cusps A, B, and C aligned longitudinally (while the mesial cusp B is missing, the reconstructed angle between these three cusps is ~175°). In more posterior molariforms (M3-5) these cusps angulated. Moreover, the relatively unreduced cusp C and
ip t
mesiodistally compressed root allow identification of this specimen as an M2 (Lopatin and Averianov, 2015; on M1 the cusp C is distinctly smaller and the roots are round in cross
cr
section).
LMCCE 1/2 resembles M2 of G. hoburensis from the Lower Cretaceous of Mongolia
us
(Lopatin and Averianov, 2015) in size and morphology. It differs by a slight ectoflexus and narrowed labial cingulum opposite to the main cusp A. LMCCE 1/2 differs from M2 of
an
Gobiconodon sp. A from the Bol’shoi Kemchug 3 locality of the Ilek Formation in Krasnoyarsk Territory (Averianov et al., 2005: fig. 5E,F) by distal part of the crown wider than the middle part, much larger cusp C, and by the lack of the distal cusp D. The
M
Gobiconodon sp. A from Bol’shoi Kemchug 3 may actually represent a distinct genus of Gobiconodontidae. There is an extensive collection of gobiconodontids from the
ed
Shestakovo 1 locality of the Ilek Formation, which is currently under study by the authors. Most likely, LMCCE 1/2 belongs to one of the undescribed new taxa from that locality.
ce pt
TRECHNOTHERIA McKenna, 1975
ZHANGHEOTHERIA Averianov, Martin et Lopatin, 2013 Genus Kiyatherium Maschenko, Lopatin et Voronkevich, 2002 Kiyatherium sp.
Ac
Fig. 2(e-i)
Referred specimen: LMCCE 1/1, left m2. Ust’-Kolba locality, Tisul’ District, Kemerovo Province, Russia; Ilek Formation, Lower Cretaceous. Measurements: length = 1.8 mm; width = 1.0 mm. Description: The crown is D-shaped in occlusal view, with straight (slightly concave) lingual margin and convex labial margin. Cusp a is high and erect, perpendicular to the crown base. Side cusps b and c are placed lingually to cusp a, forming an angle of ~117°. Cusp c is about two-thirds of cusp a in height and somewhat curved distally. A considerable part of cusp b is removed by wear; possibly it was as high as cusp c. There is a very strong lingual cingulid connecting the distal cusp d with the mesiolingual cuspule e. Cusps b, c, d, and e are aligned 5
Page 5 of 16
along the lingual margin of the crown. Cusp d is distinct but not high. Cuspule e is smaller than cusp d. The mesiolabial cuspule f, if present, is completely worn. There is a slight embayment between the latter and cuspule e. There is a large wear facet along the entire labial side of cusp b, which extends on the mesial cuspules e and f. On cusp a there is only an apical wear facet. On cusp c there is an apical facet and a facet along the c-d ridge. Also there is a horseshoe-shaped facet on the embayment between the bases of cusps c and d. On the apex of
ip t
cusp d there is a wear facet on the distal side. The roots are nearly equal in size, very robust
and long, with a terminal swelling before the end. The height of the roots is 1.6 times greater
cr
than the crown height. If the crown base oriented horizontally, the roots were slightly inclined distally. There is a thin bony lamina connecting the roots below the crown. The roots are more
us
or less round in cross section. In a parasagittal plane (Fig. 2(f, h)) the roots are bent lingually. Remarks: The tooth is a lower molar based on the lack of a cingulid on the labial side. Lower
an
molars of basal zhangheotherians (formerly “obtuse-angled” symmetrodontans) and gobiconodontids, which are likely to be closely related to the Trechnotheria (Lopatin and Averianov, 2015), have a similar design. In zhangheotherians the main cusps a, b, and c are
M
more angulated while in gobiconodontids these cusps are almost aligned. In LMCCE 1/1 the angle between these cusps is ~117°, which allows referral of this specimen to the
ed
Zhangheotheria.
There are two taxa of zhangheotherians known from the Ilek Formation: Yermakia domitor Lopatin et al., 2005 from the Shestakovo 1 locality, and Kiyatherium cardiodens
ce pt
Maschenko, Lopatin et Voronkevich, 2002 from the Shestakovo 3 locality (Maschenko et al., 2002; Lopatin et al., 2005; Lopatin et al., 2010a). K. cardiodens is slightly larger than Y. domitor, and LMCCE 1/1 fits exactly the size range of the middle molars (m2 or m3) of the former taxon (Lopatin et al., 2010a). Moreover, it is similar to K. cardiodens by less
Ac
angulation of molar cusps and much stronger lingual cingulid, while in Y. domitor the cusp angle of m2-3 is 102°-110° and the lingual cingulid is very faint (Lopatin et al., 2005). Thus attribution of LMCCE 1/1 to Kiyatherium seems to be firmly established, although it is left in open nomenclature due to the paucity of the available material. By its crown proportions, LMCCE 1/1 corresponds to the m2 of K. cardiodens. On m1 there is a greater height differential between the main and side cusps, and on m3-4 cusp c is more reduced. Also m2 is the transversely widest molar in the series, which agrees with a relatively wide crown in LMCCE 1/1. The swollen roots of LMCCE 1/1 likely reinforced the tooth implantation in the tooth sockets. A similar adaptation is characteristic for the stem mammal Morganucodon 6
Page 6 of 16
(Parrington, 1973). This is the first discovery of Kiyatherium outside its type locality (Shestakovo 3).
4. Discussion The two new Mesozoic mammal localities reported in this paper increases up to ten the number of the Mesozoic mammal localities for Russia (Lopatin and Averianov, 2006a,
ip t
2009). Six of these localities are within the Lower Cretaceous Ilek Formation in West Siberia: two in the Bol’shoi Kemchug River basin in Krasnoyarsk Territory (localities Bol’shoi
cr
Kemchug 3 and Bol’shoi Terekhtyul’) and four in the Kiya River basin in Kemerovo Province (localities Shestakovo 1 and 3, Ust’-Kolba, and Smolenskii Yar). Although the synapsid fauna
us
of the Ilek Formation is still insufficiently known, three assemblages can be recognized so far: 1) The localities within the Bol’shoi Kemchug River basin, with tritylodontids,
an
gobiconodontids, and amphilestids;
2) The Shestakovo 1 and Smolenskii Yar localities, with tritylodontids, tegotheriids, gobiconodontids, amphidontids, and the zhangheotherian Yermakia;
M
3) The Shestakovo 3 and Ust’-Kolba localities, with the zhangheotherian Kiyatherium. The first assemblage is likely to be the oldest. The second one is better known from
ed
the Shestakovo 1 locality since the Smolenskii Yar locality produced abundant tritylodontid remains and a single mammal specimen (a gobiconodontid) so far. The third assemblage is notable in the absence of tritylodontids, although the vertebrates from the Shestakovo 3
ce pt
locality have been sampled only by quarrying since the matrix there is not suitable for screenwashing. Thus its microvertebrate assemblage remains insufficiently known. The second and third assemblages may reflect different paleoenvironments or diachronous faunas. If the latter is correct, the third assemblage may illustrate the time after the local extinction of the
Ac
Tritylodontidae. This event could be the global extinction event for this group, as the Tritylodontidae are unknown in younger rocks elsewhere. The Shestakovo area was possibly the last refugium for the tritylodontids. The abundance of tritylodontids in the Early Cretaceous of West Siberia may explain the absence of the multituberculate mammals there, which likely had the similar herbivorous diet. The mammal fauna from the Ilek Formation is also notable for absence of any tribosphenic or pretribosphenic taxa, which were present in the Early Cretaceous faunas of Asia (Shikama, 1947; Dashzeveg, 1975, 1979, 1994; Dashzeveg and Kielan-Jaworowska, 1984; Kielan-Jaworowska and Dashzeveg, 1989; Averianov and Skutschas, 2001; Ji et al.,
7
Page 7 of 16
2002; Li et al., 2005; Lopatin and Averianov, 2006b, 2007). The reason for this remains poorly understood.
Acknowledgements We thank students of the Tomsk University for the help with screen-washing. Special thanks to Anastasia Zelentsova and Lidia Kondratieva, the students who found the mammals
ip t
teeth. We are grateful to Rodolphe Tabuce, Jin Meng and an anonymous reviewer for reading the manuscript and useful suggestions. This work was supported by the Tomsk State
cr
University Academic D.I. Mendeleev Fund Program and by the Russian Foundation for Basic
us
Research (project 13-04-01401).
References
an
Alifanov, V.R., Efimov, M.B., Novikov, I.V., Morales, M., 1999. [A new psittacosaur complex of tetrapods from the Lower Cretaceous Shestakovo locality (southern Siberia)]. Doklady Akademii Nauk 369, 491-493.
M
Averianov, A.O., Fayngertz, A.V., 2001. [Lizards of the Early Cretaceous of Western Siberia], [Questions of Herpetology. Materials of the first Congress of the A.M.
ed
Nikol'skii Herpetological Society]. MGU, Pushchino, Moskva, pp. 6-8. Averianov, A.O., Leshchinskiy, S.V., Fayngertz, A.V., 2003a. [Preliminary data on turtles of the Shestakovo complex of Early Cretaceous vertebrates], in: Lipnitskaya, T.A.,
ce pt
Makarenko, S.N., Podobina, V.M., Sataev, F.R., Tatyanin, G.M. (Eds.), [Materials of the Scientific Conference "Problems of Geology and Geography of Siberia"]. Vestnik Tomskogo Gosudarstvennogo Universiteta, Supplement N 3 (II), pp. 22-25. Averianov, A.O., Leshchinskiy, S.V., Skutschas, P.P., Rezvyi, A.S., 2003b. [Pterosaur teeth
Ac
from the Lower Cretaceous of Russia and Uzbekistan]. Sovremennaya Gerpetologiya 2, 5-11.
Averianov, A.O., Lopatin, A.V., 2008. "Protocone" in a pretribosphenic mammal and upper dentition of tinodontid "symmetrodontans". Journal of Vertebrate Paleontology 28, 548552. Averianov, A.O., Martin, T., Lopatin, A.V., 2013. A new phylogeny for basal Trechnotheria and Cladotheria and affinities of South American endemic Late Cretaceous mammals. Naturwissenschaften 100, 311-326. Averianov, A.O., Skutschas, P.P., 2001. A new genus of eutherian mammal from the Early Cretaceous of Transbaikalia, Russia. Acta Palaeontologica Polonica 46, 431-436. 8
Page 8 of 16
Averianov, A.O., Skutschas, P.P., Lopatin, A.V., Leshchinskiy, S.V., Rezvyi, A.S., Fayngerts, A.V., 2005. Early Cretaceous mammals from Bol'shoi Kemchug 3 locality in West Siberia, Russia. Russian Journal of Theriology 4, 1-12. Averianov, A.O., Sues, H.-D., 2007. A new troodontid (Dinosauria: Theropoda) from the Cenomanian of Uzbekistan, with a review of troodontid records from the territories of the former Soviet Union. Journal of Vertebrate Paleontology 27, 87-98.
ip t
Averianov, A.O., Voronkevich, A.V., 2002. A new crown-group salamander from the Early Cretaceous of Western Siberia. Russian Journal of Herpetology 9, 209-214.
cr
Averianov, A.O., Voronkevich, A.V., Leshchinskiy, S.V., Fayngertz, A.V., 2006. A
ceratopsian dinosaur Psittacosaurus sibiricus from the Early Cretaceous of West
us
Siberia, Russia and its phylogenetic relationships. Journal of Systematic Palaeontology 4, 359-395.
an
Averianov, A.O., Voronkevich, A.V., Maschenko, E.N., Leshchinskiy, S.V., Fayngertz, A.V., 2002. A sauropod foot from the Early Cretaceous of Western Siberia, Russia. Acta Palaeontologica Polonica 47, 117-124.
M
Chow, M.-C., Rich, T.H.V., 1984. A new triconodontan (Mammalia) from the Jurassic of China. Journal of Vertebrate Paleontology 3, 226-231.
256, 402-403.
ed
Dashzeveg, D., 1975. New primitive therian from the Early Cretaceous of Mongolia. Nature
Dashzeveg, D., 1979. Arguimus khosbajari gen. n., sp. n. (Peramuridae, Eupantotheria) from
ce pt
the Lower Cretaceous of Mongolia. Acta Palaeontologica Polonica 24, 199-204. Dashzeveg, D., 1994. Two previously unknown eupantotheres (Mammalia, Eupantotheria). American Museum Novitates 3107, 1-11. Dashzeveg, D., Kielan-Jaworowska, Z., 1984. The lower jaw of an aegialodontid mammal
Ac
from the Early Cretaceous of Mongolia. Zoological Journal of the Linnean Society 82, 217-227.
Efimov, M.B., Leshchinskiy, S.V., 2000. [First finding of the fossil crocodile skull in Siberia], in: Komarov, A.V. (Ed.), Materials of the Regional Conference of the Geologists of Siberia, Far East and North East of Russia. GalaPress, Tomsk, pp. 361363. Ji, Q., Luo, Z.-X., Yuan, C.-X., Wible, J.R., Zhang, J.-P., Georg, J.A., 2002. The earliest known eutherian mammal. Nature 416, 816-822. Kielan-Jaworowska, Z., Dashzeveg, D., 1989. Eutherian mammals from the Early Cretaceous of Mongolia. Zoologica Scripta 18, 347-355. 9
Page 9 of 16
Kielan-Jaworowska, Z., Dashzeveg, D. 1998. Early Cretaceous amphilestid ("triconodont") mammals from Mongolia. Acta Palaeontologica Polonica 43, 413-438. Kurochkin, E.N., Zelenkov, N.V., Averianov, A.O., Leshchinskiy, S.V., 2011. A new taxon of birds (Aves) from the Early Cretaceous of Western Siberia, Russia. Journal of Systematic Palaeontology 9, 109-117. Leshchinskiy, S.V., Fayngertz, A.V., 2001. [Discovery of a new "dinosaur" region in Siberia
ip t
(results of field investigations of 2000-2001)], [Evolution of Life on the Earth. Materials of the Second International Symposium, 12-15 November]. Isdatel'stvo NTL, Tomsk,
cr
pp. 437-447.
Leshchinskiy, S.V., Voronkevich, A.V., Fayngertz, A.V., Schikhovtzeva, L.G., 1997. [Some
us
aspects of taphonomy and stratigraphic position of the localities of the Shestakovo complex of Early Cretaceous vertebrates], in: Podobina, V.M. (Ed.), Questions of
an
Geology and Paleontology of Siberia. Tomskii Gosudarstvennyi Universitet, Tomsk, pp. 83-90.
Li, C., Setoguchi, T., Wang, Y., Hu, Y., Chang, Z.-L., 2005. The first record of
M
"eupantotherian" (Theria, Mammalia) from the late Early Cretaceous of western Liaoning, China. Vertebrata PalAsiatica 43, 245-255.
ed
Linnaeus, C., 1758. Systema naturae per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Vol. 1: Regnum animale. Editio decima, reformata. Laurentii Salvii, Stockholm.
ce pt
Lopatin, A.V., Averianov, A.O., 2006a. Mesozoic mammals of Russia, in: Barrett, P.M., Evans, S.E. (Eds.), 9th International Symposium on Mesozoic Terrestrial Ecosystems and Biota. Abstracts and Proceedings Volume. Natural History Museum, London, Manchester, pp. 67-70, 165.
Ac
Lopatin, A.V., Averianov, A.O., 2006b. Revision of a pretribosphenic mammal Arguimus from the Early Cretaceous of Mongolia. Acta Palaeontologica Polonica 51, 339-349. Lopatin, A.V., Averianov, A.O., 2007. Kielantherium, a basal tribosphenic mammal from the Early Cretaceous of Mongolia, with new data on the aegialodontid dentition. Acta Palaeontologica Polonica 52, 441-446. Lopatin, A.V., Averianov, A.O., 2009. Mammals that coexisted with dinosaurs. Finds on Russian territory. Herald of the Russian Academy of Sciences 79, 268-273. Lopatin, A.V., Averianov, A.O., 2015. Gobiconodon (Mammalia) from the Early Cretaceous of Mongolia and revision of Gobiconodontidae. Journal of Mammalian Evolution 22, 17-43. 10
Page 10 of 16
Lopatin, A.V., Averianov, A.O., Maschenko, E.N., Leshchinskiy, S.V., 2009. Early Cretaceous mammals from Western Siberia: 2. Tegotheriidae. Paleontological Journal 43, 453-462. Lopatin, A.V., Averianov, A.O., Maschenko, E.N., Leshchinskiy, S.V., 2010a. Early Cretaceous mammals of Western Siberia: 3. Zhangheotheriidae. Paleontological Journal 44, 573-583.
ip t
Lopatin, A.V., Maschenko, E.N., Averianov, A.O., 2010b. A new genus of triconodont
mammals from the Early Cretaceous of Western Siberia. Doklady Biological Sciences
cr
433, 282-285.
Lopatin, A.V., Maschenko, E.N., Averianov, A.O., Rezvyi, A.S., Skutschas, P.P.,
Tinodontidae. Paleontological Journal 39, 523-534.
us
Leshchinskiy, S.V., 2005. Early Cretaceous mammals from Western Siberia: 1.
an
Maschenko, E.N., Lopatin, A.V., 1998. First record of an Early Cretaceous triconodont mammal in Siberia. Bulletin de l'Institut Royal des Sciences Naturelles de Belgique, Sciences de la Terre 68, 233-236.
M
Maschenko, E.N., Lopatin, A.V., Voronkevich, A.V., 2002. A new Early Cretaceous mammal from Western Siberia. Doklady Biological Sciences 386, 475–477.
ed
Maschenko, E.N., Lopatin, A.V., Voronkevich, A.V., 2003. A new genus of the tegotheriid docodonts (Docodonta, Tegotheriidae) from the Early Cretaceous of West Siberia. Russian Journal of Theriology 1, 75-81.
ce pt
McKenna, M.C., 1975. Towards a phylogenetic classification of the Mammalia, in: Luckett, W.P., Szalay, F.S. (Eds.), Phylogeny of the Primates. Plenum Press, New York, pp. 2146.
O'Connor, J.K., Averianov, A.O., Zelenkov, N.V., 2014. A confuciusornithiform (Aves,
Ac
Pygostylia)-like tarsometatarsus from the Early Cretaceous of Siberia and a discussion of the evolution of avian hind limb musculature. Journal of Vertebrate Paleontology 34, 647-656.
Parrington, F.R., 1973. The dentition of the earliest mammals. Zoological Journal of the Linnean Society 52, 85-95. Shikama, T., 1947. Teilhardosaurus and Endotherium, new Jurassic Reptilia and Mammalia from the Husin coal-field, south Manchuria. Proceedings of the Japanese Academy 23, 76-84.
11
Page 11 of 16
Skutschas, P.P., 2014. Kiyatriton leshchinskiyi Averianov et Voronkevich, 2001, a crowngroup salamander from the Lower Cretaceous of Western Siberia, Russia. Cretaceous Research 51, 88-94. Tatarinov, L.P., Maschenko, E.N., 1999. [A find of an aberrant tritylodont (Reptilia, Cynodontia) in the Lower Cretaceous of Kemerovo Region]. Paleontologicheskii
Ac
ce pt
ed
M
an
us
cr
ip t
Zhurnal, 85-92.
12
Page 12 of 16
Table and Figure captions Table 1. Comparison of vertebrates assemblages from the Ust’-Kolba and Smolenskii Yar localities, Ilek Formation, Lower Cretaceous.
ip t
Figure 1. Geographic and geological setting for the Ust’-Kolba and Smolenskii Yar localities. a. Map of Russia with the studied area shown by an asterisk. b. Detailed map showing
cr
position of the vertebrate localities: 1-3, Shestakovo 1 to 3; 4, Smolenskii Yar; 5, Ust’-Kolba (modified from Leshchinskiy and Fayngertz, 2001: fig. 15). c. Section at the Ust’-Kolba
us
locality. d. Section at the Smolenskii Yar locality. Position of the vertebrate bearing level in
an
each section is marked by an asterisk.
Figure 2. Mammalian teeth from the Smolenskii Yar (a-d) and Ust’-Kolba (e-i) localities, Ilek Formation, Lower Cretaceous. a-d. Gobiconodontidae indet., LMCCE 1/2, left M2, in
M
occlusal (a, stereopair), lingual (b), distal(?) (c), and labial (d) views. e-i. Kiyatherium sp., LMCCE 1/1, left m2, in occlusal (e, stereopair), distal (f), lingual (g), mesial (h), and labial (i)
ed
views. For the stereopairs the anterior mesial end is up. A, C, and a-f are cusps of the upper
Ac
ce pt
and lower molar, respectively. Scale bar: 1 mm.
13
Page 13 of 16
Table 1 OK
Table 1.
Smolenskii Yar
+ +
+ +
+
+
+ + +
an
+ + +
ip t
+
cr
+
us
+
M
+
+
+ +
+ + + + + + +
+
Ac
ce pt
Ust’-Kolba
+
ed
Taxon Pisces Paleonisciformes indet. Amiiformes indet. Caudata cf. Kiyatriton sp. Testudines Testudines indet. Squamata Lacertilia indet. Choristodera Choristodera indet. Crocodyliformes Shartegosuchidae indet. “Protosuchia” indet. Pterosauria Ornithocheiridae indet. Istiodactylidae indet. Dinosauria Psittacosaurus sp. Stegosauria indet. Sauropoda indet. Therizinosauria indet. Troodontidae(?) indet. Theropoda indet. Tritylodontidae Xenocretosuchus sp. Mammalia Gobiconodontidae indet. Kiyatherium sp.
Page 14 of 16
Ac ce p
te
d
M
an
us
cr
ip t
Figure 1 OK
Page 15 of 16
Ac
ce
pt
ed
M
an
us
cr
i
Figure 2 OK
Page 16 of 16
S0016-6995(15)00015-7 http://dx.doi.org/doi:10.1016/j.geobios.2015.02.004 GEOBIO 700
To appear in:
Geobios
Received date: Revised date: Accepted date:
10-10-2014 3-1-2015 3-2-2015
Please cite this article as: Averianov, A., Lopatin, A., Skutschas, P., Leshchinskiy, S.,Two new mammal localities within the Lower Cretaceous Ilek Formation of West Siberia, Russia, Geobios (2015), http://dx.doi.org/10.1016/j.geobios.2015.02.004 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Two new mammal localities within the Lower Cretaceous Ilek Formation of West Siberia, Russia Alexander Averianov a,b,*, Alexey Lopatin c, Pavel Skutschas b,d, Sergey Leshchinskiy b
Zoological Institute of the Russian Academy of Sciences, Universitetskaya nab. 1, 199034
ip t
a
Saint Petersburg, Russia
Laboratory of Mesozoic and Cenozoic Continental Ecosystems, Tomsk State University,
cr
b
c
us
Prospekt Lenina 36, 634050 Tomsk, Russia
Borissiak Paleontological Institute of the Russian Academy of Sciences, Profsoyuznaya 123,
Vertebrate Zoology Department, Saint Petersburg State University, Universitetskaya Nab.
7/9, 199034 Saint Petersburg, Russia
M
d
an
117997 Moscow, Russia
Corresponding editor: Gilles Escarguel.
Abstract
ce pt
ed
* Corresponding author. E-mail address: [email protected] (A. Averianov).
Two new mammal localities have been discovered in the Lower Cretaceous Ilek
Ac
Formation of West Siberia, Russia, during a field work in 2014. The Smolenskii Yar locality in the Chebula District of Kemerovo Province produced an upper molariform tooth (M2) of a Gobiconodontidae indet. The Ust’-Kolba locality in the Tisul’ District of Kemerovo Province yielded a lower molar (m2) of the zhangheotherian Kiyatherium sp. These are the ninth and tenth Mesozoic mammal localities for Russia. The Kiyatherium-bearing vertebrate assemblage from the Shestakovo 3 and Ust’-Kolba localities is likely to be the youngest within the Ilek Formation, reflecting the time after the extinction of the Tritylodontidae.
Keywords:
1
Page 1 of 16
Mammalia Gobiconodontidae Zhangheotherian Kiyatherium sp. Early Cretaceous Ilek Formation
cr
ip t
Siberia
1. Introduction
us
A rich vertebrate fauna, including various dinosaurs and mammals, have been recovered during the last two decades at Shestakovo 1 and 3 localities from the Lower
an
Cretaceous Ilek Formation in West Siberia (Maschenko and Lopatin, 1998; Alifanov et al., 1999; Tatarinov and Maschenko, 1999; Efimov and Leshchinskiy, 2000; Averianov and Fayngertz, 2001; Averianov and Voronkevich, 2002; Averianov et al., 2002, 2003a, b, 2006;
M
Maschenko et al., 2003; Lopatin et al., 2005, 2009, 2010a, b; Averianov and Lopatin, 2008; Kurochkin et al., 2011; O'Connor et al., 2014; Skutschas, 2014). The Ilek Formation is widely
ed
distributed in West Siberia. Extensive exploration of various outcrops of this formation by the field parties of the Tomsk State University and affiliated colleagues led to the discovery of some other vertebrate localities, but so far only new localities within the Bol’shoi Kemchug
ce pt
River basin, Krasnoyarsk Territory, produced fossil mammals (Leshchinskiy and Fayngertz, 2001; Averianov et al., 2005).
Here we report on the discovery of two new mammal localities from the Ilek Formation in the Kiya River basin, Kemerovo Province, close to the Shestakovo localities
Ac
(Fig. 1; Table 1). Both vertebrate localities, namely Ust’-Kolba and Smolenskii Yar, have been found during prospections in 2000 and 2001 (Leshchinskiy and Fayngertz, 2001). Some additional screen-washing was made at these localities in 2002 and 2005. The first mammal specimens have been found in 2011 after screen-washing of ~230 kg of matrix from Ust’Kolba locality and ~380 kg from Smolenskii Yar locality. These mammal specimens are described herein. The specimens are housed in the collection of the Laboratory of Mesozoic and Cenozoic Continental Ecosystems, Tomsk State University (LMCCE).
2. Geographic and geological setting
2
Page 2 of 16
The Ust’-Kolba locality (GPS coordinates: N 55°52’36.2’’, E 88°19’07.6’’) is a small quarry on the left bank of the Serta River near the Ust’-Kolba settlement, ~2 km upstream from the mouth of the river (Tisul’ District, Kemerovo Province). The visible section (Fig. 1(c)) starts at the altitude of ~187 m and encompass approximately 20 m of fluvial facies of the Ilek Formation. It is dominated by yellowish-green assorted sands with an admixture of pebble and gravel, confined mainly to the bottom of cross-bedded layers and lenses. Pebbles
ip t
and gravel are presented by pellets (up to 0.1 m) of thick clays, silts, and carbonate nodules. Vertebrate fossils (scales, bone fragments, and teeth) are confined mainly to the gravel lenses
cr
at the bottom of the visible part of the section. These sediments represented a relatively high energy condition, but the preservation of the fossils, although fragmentary, indicates that they
us
were not reworked.
The Smolenskii Yar locality (GPS coordinates: N 55°58’23.9’’, E 88°05’35.9’’) is
an
confined to a natural outcrop on the right bank of Serta River, 1 km downstream from the Kursk-Smolenka settlement (Chebula District, Kemerovo Province). The section is similar to that of the Shestakovo 1 locality (Leshchinskiy et al., 1997). Eleven layers can be recognized
M
in the section at the southwest part of the escarpment from the water level (Fig. 1(d); from bottom to top):
ed
1) Yellowish to green, assorted dense sand (> 2.5 m); 2) Green coarse-grained sand with dense pellets of clay, silt and carbonate nodules. The vertebrate fossils (mainly scales, bone fragments, and teeth) are confined to the roof of
ce pt
this layer which has a cross-bedded texture; 3) Yellowish to green, fine-grained dense sand. In some places there are small ripple flow textures. At the top there is a body of dense calcareous sandstone (up to 0.5 m) projecting from the outcrop as a cornice (~3.6 m);
Ac
4) Dark gray compact clay (~0.3 m);
5) Yellowish to green fine to medium-sized dense sand (~0.7 m); 6) Bluish-gray stratified tight siltstone (~2.5 m); 7) Brown-red marly dense clay (~1.5 m); 8) Alternating layers of bluish-gray siltstone and brownish-red clay (~2 m); 9) Yellowish-green, fine-grained sand interbedded with gray siltstone (~5 m); 10) Alternating layers of bluish-gray siltstone and brownish-red clay (> 15 m); 11) Quaternary deposits (subaerial loam, sandy loam, and modern soil) (~1 m); The vertebrate assemblages from both localities are globally similar (Table 1). Most taxa are represented by isolated and usually fragmentary specimens. The most common fossils 3
Page 3 of 16
are fish scales. The salamanders are represented by postcranial elements. The turtles are surprisingly rare in the Ilek Formation, contrasting with the majority of other Cretaceous assemblages; the discussed localities yielded only small fragments of turtle plates likely belonging to the macrobaenid turtle cf. Kirgizemys sp., also known from the Shestakovo 1 locality from the same formation (Averianov et al., 2003a). The lizards and choristoderes are known from jaw fragments and isolated vertebrae; crocodyliforms are known from vertebrae,
ip t
jaw fragments, and teeth. Only two pterosaur teeth have been found, one for each locality.
The dinosaurs are also represented, mostly by isolated teeth. A notable exception (from the
cr
Ust’-Kolba locality) is an elongated posterior caudal vertebra of a derived maniraptoran
theropod, showing a groove along the dorsal side of the neural arch and the ventral side of the
us
centrum. This vertebra may belong to a troodontid, a family also known from the
Shestakovo 1 locality by isolated teeth (Averianov and Sues, 2007). Although the observed
an
differences between the two vertebrate assemblages are likely to be of sampling origin, one important discrepancy seems to be real: teeth of the tritylodontid Xenocretosuchus sp. are quite common at the Smolenskii Yar locality, while they have not yet been found at the Ust’-
M
Kolba locality.
MAMMALIA Linnaeus, 1758
ed
3. Systematic paleontology
GOBICONODONTIDAE Chow et Rich, 1984
Fig. 2(a-d)
ce pt
GOBICONODONTIDAE indet.
Referred specimen: LMCCE 1/2, left M2 missing the mesial cusp B and the mesial root. Smolenskii Yar locality, Chebula District, Kemerovo Province, Russia; Ilek Formation,
Ac
Lower Cretaceous.
Measurements: width = 0.9 mm. Description: Cusp C is about twice lower than cusp A. Cusps are conjoined approximately up to the half of cusp A height. The missing mesial cusp B was evidently more separated from cusp A. In occlusal view, cusp C is transversely narrower than cusp A, while the distal part of the crown is wider than the middle part. There is a slight ectoflexus opposite to cusp A. At this place the labial cingulum is narrower than at its distal part. The tips of cusps A and C and the crest connecting cusp C with the cingulum are worn. The lingual cingulum is highly worn. The unworn distal portion of the lingual cingulum is rather thick. The distal root is robust, short, and mesiodistally compressed, as is typical in Gobiconodon. 4
Page 4 of 16
Remarks: The tooth is an upper molariform because of a complete cingulum around the crown. Comparing with the Mongolian species of Gobiconodon (Kielan-Jaworowska and Dashzeveg, 1998; Lopatin and Averianov, 2015), the tooth is an anterior molariform (M1 or M2) since the main cusps A, B, and C aligned longitudinally (while the mesial cusp B is missing, the reconstructed angle between these three cusps is ~175°). In more posterior molariforms (M3-5) these cusps angulated. Moreover, the relatively unreduced cusp C and
ip t
mesiodistally compressed root allow identification of this specimen as an M2 (Lopatin and Averianov, 2015; on M1 the cusp C is distinctly smaller and the roots are round in cross
cr
section).
LMCCE 1/2 resembles M2 of G. hoburensis from the Lower Cretaceous of Mongolia
us
(Lopatin and Averianov, 2015) in size and morphology. It differs by a slight ectoflexus and narrowed labial cingulum opposite to the main cusp A. LMCCE 1/2 differs from M2 of
an
Gobiconodon sp. A from the Bol’shoi Kemchug 3 locality of the Ilek Formation in Krasnoyarsk Territory (Averianov et al., 2005: fig. 5E,F) by distal part of the crown wider than the middle part, much larger cusp C, and by the lack of the distal cusp D. The
M
Gobiconodon sp. A from Bol’shoi Kemchug 3 may actually represent a distinct genus of Gobiconodontidae. There is an extensive collection of gobiconodontids from the
ed
Shestakovo 1 locality of the Ilek Formation, which is currently under study by the authors. Most likely, LMCCE 1/2 belongs to one of the undescribed new taxa from that locality.
ce pt
TRECHNOTHERIA McKenna, 1975
ZHANGHEOTHERIA Averianov, Martin et Lopatin, 2013 Genus Kiyatherium Maschenko, Lopatin et Voronkevich, 2002 Kiyatherium sp.
Ac
Fig. 2(e-i)
Referred specimen: LMCCE 1/1, left m2. Ust’-Kolba locality, Tisul’ District, Kemerovo Province, Russia; Ilek Formation, Lower Cretaceous. Measurements: length = 1.8 mm; width = 1.0 mm. Description: The crown is D-shaped in occlusal view, with straight (slightly concave) lingual margin and convex labial margin. Cusp a is high and erect, perpendicular to the crown base. Side cusps b and c are placed lingually to cusp a, forming an angle of ~117°. Cusp c is about two-thirds of cusp a in height and somewhat curved distally. A considerable part of cusp b is removed by wear; possibly it was as high as cusp c. There is a very strong lingual cingulid connecting the distal cusp d with the mesiolingual cuspule e. Cusps b, c, d, and e are aligned 5
Page 5 of 16
along the lingual margin of the crown. Cusp d is distinct but not high. Cuspule e is smaller than cusp d. The mesiolabial cuspule f, if present, is completely worn. There is a slight embayment between the latter and cuspule e. There is a large wear facet along the entire labial side of cusp b, which extends on the mesial cuspules e and f. On cusp a there is only an apical wear facet. On cusp c there is an apical facet and a facet along the c-d ridge. Also there is a horseshoe-shaped facet on the embayment between the bases of cusps c and d. On the apex of
ip t
cusp d there is a wear facet on the distal side. The roots are nearly equal in size, very robust
and long, with a terminal swelling before the end. The height of the roots is 1.6 times greater
cr
than the crown height. If the crown base oriented horizontally, the roots were slightly inclined distally. There is a thin bony lamina connecting the roots below the crown. The roots are more
us
or less round in cross section. In a parasagittal plane (Fig. 2(f, h)) the roots are bent lingually. Remarks: The tooth is a lower molar based on the lack of a cingulid on the labial side. Lower
an
molars of basal zhangheotherians (formerly “obtuse-angled” symmetrodontans) and gobiconodontids, which are likely to be closely related to the Trechnotheria (Lopatin and Averianov, 2015), have a similar design. In zhangheotherians the main cusps a, b, and c are
M
more angulated while in gobiconodontids these cusps are almost aligned. In LMCCE 1/1 the angle between these cusps is ~117°, which allows referral of this specimen to the
ed
Zhangheotheria.
There are two taxa of zhangheotherians known from the Ilek Formation: Yermakia domitor Lopatin et al., 2005 from the Shestakovo 1 locality, and Kiyatherium cardiodens
ce pt
Maschenko, Lopatin et Voronkevich, 2002 from the Shestakovo 3 locality (Maschenko et al., 2002; Lopatin et al., 2005; Lopatin et al., 2010a). K. cardiodens is slightly larger than Y. domitor, and LMCCE 1/1 fits exactly the size range of the middle molars (m2 or m3) of the former taxon (Lopatin et al., 2010a). Moreover, it is similar to K. cardiodens by less
Ac
angulation of molar cusps and much stronger lingual cingulid, while in Y. domitor the cusp angle of m2-3 is 102°-110° and the lingual cingulid is very faint (Lopatin et al., 2005). Thus attribution of LMCCE 1/1 to Kiyatherium seems to be firmly established, although it is left in open nomenclature due to the paucity of the available material. By its crown proportions, LMCCE 1/1 corresponds to the m2 of K. cardiodens. On m1 there is a greater height differential between the main and side cusps, and on m3-4 cusp c is more reduced. Also m2 is the transversely widest molar in the series, which agrees with a relatively wide crown in LMCCE 1/1. The swollen roots of LMCCE 1/1 likely reinforced the tooth implantation in the tooth sockets. A similar adaptation is characteristic for the stem mammal Morganucodon 6
Page 6 of 16
(Parrington, 1973). This is the first discovery of Kiyatherium outside its type locality (Shestakovo 3).
4. Discussion The two new Mesozoic mammal localities reported in this paper increases up to ten the number of the Mesozoic mammal localities for Russia (Lopatin and Averianov, 2006a,
ip t
2009). Six of these localities are within the Lower Cretaceous Ilek Formation in West Siberia: two in the Bol’shoi Kemchug River basin in Krasnoyarsk Territory (localities Bol’shoi
cr
Kemchug 3 and Bol’shoi Terekhtyul’) and four in the Kiya River basin in Kemerovo Province (localities Shestakovo 1 and 3, Ust’-Kolba, and Smolenskii Yar). Although the synapsid fauna
us
of the Ilek Formation is still insufficiently known, three assemblages can be recognized so far: 1) The localities within the Bol’shoi Kemchug River basin, with tritylodontids,
an
gobiconodontids, and amphilestids;
2) The Shestakovo 1 and Smolenskii Yar localities, with tritylodontids, tegotheriids, gobiconodontids, amphidontids, and the zhangheotherian Yermakia;
M
3) The Shestakovo 3 and Ust’-Kolba localities, with the zhangheotherian Kiyatherium. The first assemblage is likely to be the oldest. The second one is better known from
ed
the Shestakovo 1 locality since the Smolenskii Yar locality produced abundant tritylodontid remains and a single mammal specimen (a gobiconodontid) so far. The third assemblage is notable in the absence of tritylodontids, although the vertebrates from the Shestakovo 3
ce pt
locality have been sampled only by quarrying since the matrix there is not suitable for screenwashing. Thus its microvertebrate assemblage remains insufficiently known. The second and third assemblages may reflect different paleoenvironments or diachronous faunas. If the latter is correct, the third assemblage may illustrate the time after the local extinction of the
Ac
Tritylodontidae. This event could be the global extinction event for this group, as the Tritylodontidae are unknown in younger rocks elsewhere. The Shestakovo area was possibly the last refugium for the tritylodontids. The abundance of tritylodontids in the Early Cretaceous of West Siberia may explain the absence of the multituberculate mammals there, which likely had the similar herbivorous diet. The mammal fauna from the Ilek Formation is also notable for absence of any tribosphenic or pretribosphenic taxa, which were present in the Early Cretaceous faunas of Asia (Shikama, 1947; Dashzeveg, 1975, 1979, 1994; Dashzeveg and Kielan-Jaworowska, 1984; Kielan-Jaworowska and Dashzeveg, 1989; Averianov and Skutschas, 2001; Ji et al.,
7
Page 7 of 16
2002; Li et al., 2005; Lopatin and Averianov, 2006b, 2007). The reason for this remains poorly understood.
Acknowledgements We thank students of the Tomsk University for the help with screen-washing. Special thanks to Anastasia Zelentsova and Lidia Kondratieva, the students who found the mammals
ip t
teeth. We are grateful to Rodolphe Tabuce, Jin Meng and an anonymous reviewer for reading the manuscript and useful suggestions. This work was supported by the Tomsk State
cr
University Academic D.I. Mendeleev Fund Program and by the Russian Foundation for Basic
us
Research (project 13-04-01401).
References
an
Alifanov, V.R., Efimov, M.B., Novikov, I.V., Morales, M., 1999. [A new psittacosaur complex of tetrapods from the Lower Cretaceous Shestakovo locality (southern Siberia)]. Doklady Akademii Nauk 369, 491-493.
M
Averianov, A.O., Fayngertz, A.V., 2001. [Lizards of the Early Cretaceous of Western Siberia], [Questions of Herpetology. Materials of the first Congress of the A.M.
ed
Nikol'skii Herpetological Society]. MGU, Pushchino, Moskva, pp. 6-8. Averianov, A.O., Leshchinskiy, S.V., Fayngertz, A.V., 2003a. [Preliminary data on turtles of the Shestakovo complex of Early Cretaceous vertebrates], in: Lipnitskaya, T.A.,
ce pt
Makarenko, S.N., Podobina, V.M., Sataev, F.R., Tatyanin, G.M. (Eds.), [Materials of the Scientific Conference "Problems of Geology and Geography of Siberia"]. Vestnik Tomskogo Gosudarstvennogo Universiteta, Supplement N 3 (II), pp. 22-25. Averianov, A.O., Leshchinskiy, S.V., Skutschas, P.P., Rezvyi, A.S., 2003b. [Pterosaur teeth
Ac
from the Lower Cretaceous of Russia and Uzbekistan]. Sovremennaya Gerpetologiya 2, 5-11.
Averianov, A.O., Lopatin, A.V., 2008. "Protocone" in a pretribosphenic mammal and upper dentition of tinodontid "symmetrodontans". Journal of Vertebrate Paleontology 28, 548552. Averianov, A.O., Martin, T., Lopatin, A.V., 2013. A new phylogeny for basal Trechnotheria and Cladotheria and affinities of South American endemic Late Cretaceous mammals. Naturwissenschaften 100, 311-326. Averianov, A.O., Skutschas, P.P., 2001. A new genus of eutherian mammal from the Early Cretaceous of Transbaikalia, Russia. Acta Palaeontologica Polonica 46, 431-436. 8
Page 8 of 16
Averianov, A.O., Skutschas, P.P., Lopatin, A.V., Leshchinskiy, S.V., Rezvyi, A.S., Fayngerts, A.V., 2005. Early Cretaceous mammals from Bol'shoi Kemchug 3 locality in West Siberia, Russia. Russian Journal of Theriology 4, 1-12. Averianov, A.O., Sues, H.-D., 2007. A new troodontid (Dinosauria: Theropoda) from the Cenomanian of Uzbekistan, with a review of troodontid records from the territories of the former Soviet Union. Journal of Vertebrate Paleontology 27, 87-98.
ip t
Averianov, A.O., Voronkevich, A.V., 2002. A new crown-group salamander from the Early Cretaceous of Western Siberia. Russian Journal of Herpetology 9, 209-214.
cr
Averianov, A.O., Voronkevich, A.V., Leshchinskiy, S.V., Fayngertz, A.V., 2006. A
ceratopsian dinosaur Psittacosaurus sibiricus from the Early Cretaceous of West
us
Siberia, Russia and its phylogenetic relationships. Journal of Systematic Palaeontology 4, 359-395.
an
Averianov, A.O., Voronkevich, A.V., Maschenko, E.N., Leshchinskiy, S.V., Fayngertz, A.V., 2002. A sauropod foot from the Early Cretaceous of Western Siberia, Russia. Acta Palaeontologica Polonica 47, 117-124.
M
Chow, M.-C., Rich, T.H.V., 1984. A new triconodontan (Mammalia) from the Jurassic of China. Journal of Vertebrate Paleontology 3, 226-231.
256, 402-403.
ed
Dashzeveg, D., 1975. New primitive therian from the Early Cretaceous of Mongolia. Nature
Dashzeveg, D., 1979. Arguimus khosbajari gen. n., sp. n. (Peramuridae, Eupantotheria) from
ce pt
the Lower Cretaceous of Mongolia. Acta Palaeontologica Polonica 24, 199-204. Dashzeveg, D., 1994. Two previously unknown eupantotheres (Mammalia, Eupantotheria). American Museum Novitates 3107, 1-11. Dashzeveg, D., Kielan-Jaworowska, Z., 1984. The lower jaw of an aegialodontid mammal
Ac
from the Early Cretaceous of Mongolia. Zoological Journal of the Linnean Society 82, 217-227.
Efimov, M.B., Leshchinskiy, S.V., 2000. [First finding of the fossil crocodile skull in Siberia], in: Komarov, A.V. (Ed.), Materials of the Regional Conference of the Geologists of Siberia, Far East and North East of Russia. GalaPress, Tomsk, pp. 361363. Ji, Q., Luo, Z.-X., Yuan, C.-X., Wible, J.R., Zhang, J.-P., Georg, J.A., 2002. The earliest known eutherian mammal. Nature 416, 816-822. Kielan-Jaworowska, Z., Dashzeveg, D., 1989. Eutherian mammals from the Early Cretaceous of Mongolia. Zoologica Scripta 18, 347-355. 9
Page 9 of 16
Kielan-Jaworowska, Z., Dashzeveg, D. 1998. Early Cretaceous amphilestid ("triconodont") mammals from Mongolia. Acta Palaeontologica Polonica 43, 413-438. Kurochkin, E.N., Zelenkov, N.V., Averianov, A.O., Leshchinskiy, S.V., 2011. A new taxon of birds (Aves) from the Early Cretaceous of Western Siberia, Russia. Journal of Systematic Palaeontology 9, 109-117. Leshchinskiy, S.V., Fayngertz, A.V., 2001. [Discovery of a new "dinosaur" region in Siberia
ip t
(results of field investigations of 2000-2001)], [Evolution of Life on the Earth. Materials of the Second International Symposium, 12-15 November]. Isdatel'stvo NTL, Tomsk,
cr
pp. 437-447.
Leshchinskiy, S.V., Voronkevich, A.V., Fayngertz, A.V., Schikhovtzeva, L.G., 1997. [Some
us
aspects of taphonomy and stratigraphic position of the localities of the Shestakovo complex of Early Cretaceous vertebrates], in: Podobina, V.M. (Ed.), Questions of
an
Geology and Paleontology of Siberia. Tomskii Gosudarstvennyi Universitet, Tomsk, pp. 83-90.
Li, C., Setoguchi, T., Wang, Y., Hu, Y., Chang, Z.-L., 2005. The first record of
M
"eupantotherian" (Theria, Mammalia) from the late Early Cretaceous of western Liaoning, China. Vertebrata PalAsiatica 43, 245-255.
ed
Linnaeus, C., 1758. Systema naturae per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Vol. 1: Regnum animale. Editio decima, reformata. Laurentii Salvii, Stockholm.
ce pt
Lopatin, A.V., Averianov, A.O., 2006a. Mesozoic mammals of Russia, in: Barrett, P.M., Evans, S.E. (Eds.), 9th International Symposium on Mesozoic Terrestrial Ecosystems and Biota. Abstracts and Proceedings Volume. Natural History Museum, London, Manchester, pp. 67-70, 165.
Ac
Lopatin, A.V., Averianov, A.O., 2006b. Revision of a pretribosphenic mammal Arguimus from the Early Cretaceous of Mongolia. Acta Palaeontologica Polonica 51, 339-349. Lopatin, A.V., Averianov, A.O., 2007. Kielantherium, a basal tribosphenic mammal from the Early Cretaceous of Mongolia, with new data on the aegialodontid dentition. Acta Palaeontologica Polonica 52, 441-446. Lopatin, A.V., Averianov, A.O., 2009. Mammals that coexisted with dinosaurs. Finds on Russian territory. Herald of the Russian Academy of Sciences 79, 268-273. Lopatin, A.V., Averianov, A.O., 2015. Gobiconodon (Mammalia) from the Early Cretaceous of Mongolia and revision of Gobiconodontidae. Journal of Mammalian Evolution 22, 17-43. 10
Page 10 of 16
Lopatin, A.V., Averianov, A.O., Maschenko, E.N., Leshchinskiy, S.V., 2009. Early Cretaceous mammals from Western Siberia: 2. Tegotheriidae. Paleontological Journal 43, 453-462. Lopatin, A.V., Averianov, A.O., Maschenko, E.N., Leshchinskiy, S.V., 2010a. Early Cretaceous mammals of Western Siberia: 3. Zhangheotheriidae. Paleontological Journal 44, 573-583.
ip t
Lopatin, A.V., Maschenko, E.N., Averianov, A.O., 2010b. A new genus of triconodont
mammals from the Early Cretaceous of Western Siberia. Doklady Biological Sciences
cr
433, 282-285.
Lopatin, A.V., Maschenko, E.N., Averianov, A.O., Rezvyi, A.S., Skutschas, P.P.,
Tinodontidae. Paleontological Journal 39, 523-534.
us
Leshchinskiy, S.V., 2005. Early Cretaceous mammals from Western Siberia: 1.
an
Maschenko, E.N., Lopatin, A.V., 1998. First record of an Early Cretaceous triconodont mammal in Siberia. Bulletin de l'Institut Royal des Sciences Naturelles de Belgique, Sciences de la Terre 68, 233-236.
M
Maschenko, E.N., Lopatin, A.V., Voronkevich, A.V., 2002. A new Early Cretaceous mammal from Western Siberia. Doklady Biological Sciences 386, 475–477.
ed
Maschenko, E.N., Lopatin, A.V., Voronkevich, A.V., 2003. A new genus of the tegotheriid docodonts (Docodonta, Tegotheriidae) from the Early Cretaceous of West Siberia. Russian Journal of Theriology 1, 75-81.
ce pt
McKenna, M.C., 1975. Towards a phylogenetic classification of the Mammalia, in: Luckett, W.P., Szalay, F.S. (Eds.), Phylogeny of the Primates. Plenum Press, New York, pp. 2146.
O'Connor, J.K., Averianov, A.O., Zelenkov, N.V., 2014. A confuciusornithiform (Aves,
Ac
Pygostylia)-like tarsometatarsus from the Early Cretaceous of Siberia and a discussion of the evolution of avian hind limb musculature. Journal of Vertebrate Paleontology 34, 647-656.
Parrington, F.R., 1973. The dentition of the earliest mammals. Zoological Journal of the Linnean Society 52, 85-95. Shikama, T., 1947. Teilhardosaurus and Endotherium, new Jurassic Reptilia and Mammalia from the Husin coal-field, south Manchuria. Proceedings of the Japanese Academy 23, 76-84.
11
Page 11 of 16
Skutschas, P.P., 2014. Kiyatriton leshchinskiyi Averianov et Voronkevich, 2001, a crowngroup salamander from the Lower Cretaceous of Western Siberia, Russia. Cretaceous Research 51, 88-94. Tatarinov, L.P., Maschenko, E.N., 1999. [A find of an aberrant tritylodont (Reptilia, Cynodontia) in the Lower Cretaceous of Kemerovo Region]. Paleontologicheskii
Ac
ce pt
ed
M
an
us
cr
ip t
Zhurnal, 85-92.
12
Page 12 of 16
Table and Figure captions Table 1. Comparison of vertebrates assemblages from the Ust’-Kolba and Smolenskii Yar localities, Ilek Formation, Lower Cretaceous.
ip t
Figure 1. Geographic and geological setting for the Ust’-Kolba and Smolenskii Yar localities. a. Map of Russia with the studied area shown by an asterisk. b. Detailed map showing
cr
position of the vertebrate localities: 1-3, Shestakovo 1 to 3; 4, Smolenskii Yar; 5, Ust’-Kolba (modified from Leshchinskiy and Fayngertz, 2001: fig. 15). c. Section at the Ust’-Kolba
us
locality. d. Section at the Smolenskii Yar locality. Position of the vertebrate bearing level in
an
each section is marked by an asterisk.
Figure 2. Mammalian teeth from the Smolenskii Yar (a-d) and Ust’-Kolba (e-i) localities, Ilek Formation, Lower Cretaceous. a-d. Gobiconodontidae indet., LMCCE 1/2, left M2, in
M
occlusal (a, stereopair), lingual (b), distal(?) (c), and labial (d) views. e-i. Kiyatherium sp., LMCCE 1/1, left m2, in occlusal (e, stereopair), distal (f), lingual (g), mesial (h), and labial (i)
ed
views. For the stereopairs the anterior mesial end is up. A, C, and a-f are cusps of the upper
Ac
ce pt
and lower molar, respectively. Scale bar: 1 mm.
13
Page 13 of 16
Table 1 OK
Table 1.
Smolenskii Yar
+ +
+ +
+
+
+ + +
an
+ + +
ip t
+
cr
+
us
+
M
+
+
+ +
+ + + + + + +
+
Ac
ce pt
Ust’-Kolba
+
ed
Taxon Pisces Paleonisciformes indet. Amiiformes indet. Caudata cf. Kiyatriton sp. Testudines Testudines indet. Squamata Lacertilia indet. Choristodera Choristodera indet. Crocodyliformes Shartegosuchidae indet. “Protosuchia” indet. Pterosauria Ornithocheiridae indet. Istiodactylidae indet. Dinosauria Psittacosaurus sp. Stegosauria indet. Sauropoda indet. Therizinosauria indet. Troodontidae(?) indet. Theropoda indet. Tritylodontidae Xenocretosuchus sp. Mammalia Gobiconodontidae indet. Kiyatherium sp.
Page 14 of 16
Ac ce p
te
d
M
an
us
cr
ip t
Figure 1 OK
Page 15 of 16
Ac
ce
pt
ed
M
an
us
cr
i
Figure 2 OK
Page 16 of 16