ISSN 0031-0301, Paleontological Journal, 2009, Vol. 43, No. 4, pp. 453462. Pleiades Publishing, Ltd., 2009.Original Russian Text A.V. Lopatin, A.O. Averianov, E.N. Maschenko, S.V. Leshchinskiy, 2009, published in Paleontologicheskii Zhurnal, 2009, No. 4, pp. 92100.
is a memberof the Early Cretaceous Shestakovo Vertebrate Assem-blage of Western Siberia, which has been studiedintensely during the past years (Maschenko and Lopa-tin, 1998; Maschenko et al., 2002, 2003; Lopatin et al.,2005; Lopatin and Averianov, 2007; see also referencesin these papers). This species was described based onthree mandibular fragments, one of which (holotypePM TGU, no. 16/5-22) contains two deciduous premo-lars and
and others have more posterior molars, pre-sumably identified as M
in specimen PM TGU,no. 16/5-14 and as M
in specimen PM TGU,no. 16/5-2 (Maschenko et al., 2003). The holotypeadditionally has four alveoli of two relatively smalldouble-rooted teeth; therefore, the lower cheek teethformula of
was initially deter-mined as P
. In 2004, E.N. Maschenko (PIN) andA.S. Rezvyi (SPbGU) found a new dentary fragment of
(specimen PM TGU, no. 120/9-34) in theShestakovo 1 locality. This specimen has M
, threeposterior premolars, the posterior alveolus of thecanine, and six small alveoli (with partially preservedroots) of three anterior premolars. Close to the dentaryfragment in the matrix, there were three isolated pre-molars and a fragment of the symphyseal region of thedentary, with a strongly damaged large double-rootedtooth, which was identified as the canine, and an alveo-lus of a single-rooted tooth anterior to it (which pre-sumably contained the ultimate incisor). As the speci-men was prepared, the breaks of roots of the isolatedpremolars fit into the fragments preserved in the alve-oli; thus, these teeth were glued to the dentary. The den-
tary fragment with the canine, alveolus of the incisor,and partial symphysis also belongs to this hemimandi-ble; they come in contact just anterior to the alveoli ofthe anterior premolar. This allowed the establishment ofthe structure and number of the lower premolars of
and variation in the structure of the lowermolars and correctness of identification of M
. Anotherimportant find is a maxillary fragment with the penulti-mate and ultimate molars (specimen PM TGU,no. 120/5-Sh1-5), which were found by P.P. Skuchas(SPbGU), A.S. Rezvyi, and other researchers in 2005 inthe Shestakovo 1 locality. In addition, in 2007, Shesta-kovo 1 yielded another isolated upper molar (specimenPM TGU, no. 120/7-Sh1-3). These specimens allow thestructure of the upper molars of
to bedescribed for the first time. The present study revisesthe morphology of
based on all knownspecimens, including new finds listed above and others.
In the description, we use the dental nomenclatureand terminology of Docodonta developed by Butler(1997) and modified by us (Averianov et al., 2009; seealso Fig. 1) based on subsequent works (Hu et al., 2007;Luo and Martin, 2007). The letter designations of den-tal cusps correspond to those accepted by some otherresearchers (Kermack et al., 1987; Sigogneau-Russell,2001, 2003; Kielan-Jaworowska et al., 2004): in thelower molars, cusp
is the main cusp, cusp
is themesiolabial cusp, cusp
is the distolingual cusp, cusp
is the mesiolingual cusp, cusp
is the anterior cusp,cusp
is an additional anterolingual cingular cusp, cusp
is the distolabial cusp or labial talonid cusp, cusp
is the lingual talonid cusp; in the upper molars, cusp
is the mesiolabial cusp, cusp
is the labial cingularcusp, cusp
is the distolabial cusp, cusp
is the distal
Early Cretaceous Mammals of Western Siberia: 2. Tegotheriidae
A. V. Lopatin
, A. O. Averianov
, E. N. Maschenko
, and S. V. Leshchinskiy
Borissiak Paleontological Institute, Russian Academy of Sciences, Profsoyuznaya ul. 123, Moscow, 117997 Russiae-mail: email@example.com
Zoological Institute, Russian Academy of Sciences, Universitetskaya nab. 1, St. Petersburg, 199034 Russia
Tomsk State University, pr. Lenina 36, Tomsk, 634050 Russia
Received July 21, 2008
New specimens of the tegotheriid docodont
Maschenko et al., 2003, includ-ing a maxillary fragment with two posterior teeth, an isolated upper molar, and mandibular fragments with teeth fromthe Early Cretaceous Shestakovo locality are described. The dental formula of
1 + ?
. Theupper molars of
, with two main labial and three lingual cusps, are convergently similar to themolars of tribosphenic mammals. In the dentary, the symphysis is short and Meckels groove is reduced.
is similar in the structure of lower teeth to
from the Upper Jurassic of Mongolia; itis the latest known representative of Docodonta.
: Docodonta, Tegotheriidae, Lower Cretaceous, Western Siberia.
LOPATIN et al.
stylar cusp, cusp
is the mesial stylar cusp, cusp
isthe mesiolingual cusp, and cusp
is the distolingualcusp (homologues of the cusp
have not been recog-nized). The crests between particular cusps are desig-nated as follows:
ab, ag, ac, ad, bg, bbb, bbg,cd, ddd, ddc, AB, AC, CD, BE, XZ
We use the following abbreviations: (L) maximumlength of the tooth crown; (W) maximum width of thetooth crown, (H) height of the tooth crown along thelabial side of the cusp
; and (h) depth of the horizontalramus of the lower jaw on the labial side.
The material described and discussed in the presentstudy is stored in the Paleontological Museum ofTomsk State University (PM TGU), Tomsk, Russia.
Order Docodonta Kretzoi, 1946
Family Tegotheriidae Tatarinov, 1994
Tegotheriidae: Tatarinov, 1994, p. 104; Maschenko et al., 2003,p. 76.
Ty p e g e n u s.
Tatarinov, 1994,Upper Jurassic of Mongolia.
D i a g n o s i s. Upper molars with cusp
; lower molars with cusp
and largepseudotalonid basin bordered by crests
, without crest
G e n e r i c c o m p o s i t i o n. In addition to thetype genus,
Sigogneau-Russell, 2003 fromthe Middle Jurassic of England and
Maschenko, Lopatin et Voronkevich, 2003 from theLower Cretaceous of Western Siberia.
C o m p a r i s o n. The family Tegotheriidae differsfrom other docodonts in the presence of the cusp
andthe absence of the crest
on the upper molars, thepresence of the cusp
and the formation of walls ofthe pseudotalonid basin by the crests
combined with the absence of a crest
onthe lower molars.
R e m a r k s. The family Tegotheriidae was consid-ered to include
Martin et Averianov,2004 from the Middle Jurassic of Kyrgyzstan and
Lopatin et Averianov, 2005 from the MiddleJurassic of Western Siberia (Martin and Averianov,2004; Lopatin and Averianov, 2005; Averianov andLopatin, 2006). At present, based on new phylogeneticanalysis, we regard these genera as Docodonta incertaesedis, assuming a basal position of
amongdocodonts (Averianov et al., 2009).
Maschenko, Lopatin et Voronkevich, 2003
: Maschenko et al., 2003, p. 76.
Ty p e s p e c i e s.
Maschenko, Lopatin et Voronkevich, 2003, Lower Cre-taceous of Western Siberia.
D i a g n o s i s. Upper molars with strongly trans-versely expanded lingual projection. In lower molars,cusp
larger than cusp
incomplete, reduced, crest
or distinct cusp
well developed, crest
present or absent,supplementary crests of posterior basin absent, lingualcingulid well developed.
S p e c i e s c o m p o s i t i o n. Type species.C o m p a r i s o n.
in the shorter crest
, reduced crest
, and well-developed crest
It differs from
in the more strongly expanded lingual pro-jection of the upper molars, the reversed size ratio ofcusps
, the absence of crest
and distinct cusp
, possible presence of crest
, the absence of sup-plementary crests of the posterior basin, and in thewell-developed lingual cingulid of the lower molars.
Maschenko, Lopatin et