MA R IAN M t. Y N AR S KI & PA G AM NA R MAN DAC H
NEW T URTLE REMAINS FROM THE UPPER CRETACEOUS
O F THE GOBl DESERT, MONGOLl A
Abstract , - New finds o f tu rt le re mai ns co llected in 1970 by the Poli sh-M on goli a n Pal aeont ological Ex ped ition fro m th e
Up pe r Nemegt Beds in th e enviro ns of Nemegt , N em egt Basin a nd in Shcercgeen Gas hoon are d isc ussed in th e p rese nt
pap er. La rge spec imens of the grou p Amp h ichc lydia, Mo ngolemys elegans KHOSATZKY & M LYNARSKI, Zungerlia sp ., two
differ ent for m s (sma ll a nd la rge) of th e ge nus Trionyx a nd uni de nt ified fo rms wit h a stro ng ly se rra te ridge of ca ra pace ha ve
been fo und in the Up per Ncm cgt Bed s. A specimen a ssigned to Mongolemys sp. comes from Sheerc gee n Gashoon.
INTRODUCTI ON
New, not very rich but relatively well-preserved remains of various chelonian s were
found durin g the Polish-M ongolian Palaeont ological Expedition in 1970.
Most of the materials have been collected from the Upper Nemegt Beds (G RA DZINSKI
et (/1., 1968(69) in the north ern pa rt of the locality Nernegt, Nemegt Basin. The turtl es of the
same age have been found in Tsagan Khu shu, Nemegt Basin, and describ ed by KHOSATZK Y
& ML YNARSKI (1971 ).
One of the specimens, com ing from the locality Sheeregeen G ashoon (KIELAN-JAwoROWSK A & BARsBoLD, 1972), is rath er incomplete a nd dam aged . It was determin ed as M OIlgoletnys sp. The exact age of th e U pper Cretaceo us deposits of Sheeregeen Gashoon has not
been hithert o recognized. The ident ified specimens from the U pper Nemegt Beds of the locality
Nemegt do not on the whole differ from th ose fro m the sa me beds found in the locality Tsagan
Khu shu (KHOSATZKY & MLYNARSKI , 1971 ). They a re briefly describ ed or illustrated in the
present paper only for the sake of documentati on .
DESCRIPTIONS
Sub o rd e r AMPHICHELYDIA LYD EKKER, 1889
AMPHICHELYDIA gen. et sp. indet.
(Text-fig . I )
Material. - I) A skull of a la rge individual, 13.5 cm long, very strongly damaged a nd
preserved mostly as a mould with fine fragments of bones (Z .Pa1. No.MgCh(78); 2) A wellpreserved fragment of a posterior ridge of carapace of a large individual , includin g peripherals
X a nd X l, as well as a pygal plat e (Z.Pa I.No.MgCh(85). Both specimens from the Upper
Nemegt Beds of the locality Ne megt, ·Nemegt Basin.
Description. - The specimen Z.PaI.No.MgCh(85 makes up a fragmentary posterior
ridge of cara pace. Jud ging by the size of the plates preserved the entire cara pace of this indi-
96
MARIAN ML YNA RSKl & PAGAM NARMAN DACH
vid ual was abo ut 80 cm long. Well-preserved sulci allow one to reco nstruct the sha pe of the
last marginals 10 and 11, as well as postcent rals whose sulcus intersects the right ridge of pygal
plate. Shields a re markedly lower than th e periph eral plat es. Th e pygal ridge of carapace flat ,
conspicuo usly narrowed (Text -fig. I). The surface of plates is covered with a primitive ornamenta tion , the same as that on the frag ments of shells of la rge specimens of the sa me group
coming from the loca lity Tsaga n Kh ushu (K HOSATZK Y & MLY NARSKI , 1971 , p. 131 -144).
.'\
"..
I
,,
,
,
I
,.-- - -
-,
- ... . . -,
I
f
,. . -----_....
\
"<:
)
F ig. I
A mp ltichelytlia gen. et sp. indet ., frag ment of the pygal ridge of a cara pace ; Uppe r Cretaceous, Upper Nc megt Beds,
Ncmegt , Ncmegt Basin . Gobi Desert (Z .PaI.No. MgCh j85) ; x 0.5.
The specimen Z.PaI.No .MgChj78 is a stro ngly destroyed skull of a larg e individua l
whose shape, preserve d on a moul d, is similar to the skull of a lar ge turtle from the Nernegt
Basin housed at the Palaeonto logica l Museum of the U . S. S. R.' s Academ y of Sciences in
Moscow ( ROZHD ESTVE NSKY, 1969, p. 8 1). Z.Pa I.No. MgC hj78 has well-p reserved frontals
and parietals, as well as left postfro nta ls which, togeth er with fro nta ls, form the ridge of a n
orbit. Otic region strongly develo ped. Fragme nts of occipita l regio n stro ngly crumhled . T he
surface of bone s from the preserved parieta l regio n is uneven , ro ugh a nd indic ati ve of a stro ng
fusion of the ep idermal layer to the outer surface of bone . This is a character of man y primitive
turtles, is particular the Amphichelydia.
Suborder METACHEL V OlA ZANGERI., 1969
Fa m ily OERMATEMYO IOAE GRAY, 1870
Gen us M ONGOLEMYS KHOSATZKY & MLYNARSKI , 1971
M ongolemys elegans KHOSATZKY & MLYNARSKI, 1971
Diag nosis. - See KHOSATZKY & M LYNARSKl, 1971, p. 131-144.
Material. - I) An almost co mplete a ltho ugh deformed carapace together with a po sterior part of plastron of a large individ ua l (Z.PaI.No.MgC hj74); 2) A well-preserved, 24 cm
NEW T URTLE REMA INS FROM T H E U PPER C R ETAC EO US
97
lo ng carapace witho ut a neck rid ge (Z. PaI.No.MgCh j75); 3) A d am aged a nterio r cra nial part
of carapace an d part of a n a nterior lo be of plast ron of a la rge indivi d ua l; t he frag me nt p reserved is 7.2 cm lon g (Z .Pa I.No.MgC hj7 9); 4) T hirteen shell fr agm ents of a few ind ividual s
varying in size (Z .PaI. No.MgCh j82a); 5) Seven fragme nts of cara pace of la rge ind ividuals
(Z. PaI.No.MgC h j87) . A ll specimens fro m t he Upper Ne megt Bed s, N em egt, Ne megt Ba sin .
M ongolemys sp .
(Text-fig, 2)
M aterial. - A n a lmost complete altho ug h stro ngly d am aged carapace a nd a strong ly
damaged a nd broke n plastron o f a n ind ividu al abo ut 20 cm lon g (Z. Pa I.No.MgCh j7 1) fr om
Sheeregeen Gashoo n.
Description. - A single specimen fro m Shee regee n G ash o on is po orl y p reser ved . T he
surface of carapace was covered wit h a very ha rd ce me nte d laye r wh ich o bsc ured th e str ucture
of pla tes. Afte r it ha s mec hanica lly bee n removed, a del icat e dermal sculpture tu rn ed out to
be damaged. T he shape of t he entire carapace an d a n ap proximate sha pe of plastron can be
acc urately reconstructed o n t he basis ' of this spec ime n. Carapace is not very strongly va ulted,
smooth , witho ut any traces of kee ls. Its peri phera l ridge is qu ite eve n, no t serrate or undulat e.
Carapace ova l in ou tline wit h on ly a slight te nde ncy to a n exte nsio n towa rds th e lacki ng pygal
part. Pl a stron elo ngate, cross-shapped , wit h a relatively narrow but lon g poste rio r lobe. It is
co nnected wit h carapace by a wide br idge. A ll its eleme nt s were st ro ngly co n nec ted wit h eac h
ot her.
All sut ures an d s ulci a re exce llent ly visible in t he part of carapace preserved . Of th e
lacking pyga l pa rt detached fragme nts are a lso prese rved co m plete ly exposed o n t he in ner
side. P roneura l plate, not very la rge, wide a nd symmetrica l, is co nnected with neural N- I
having convex lateral ridges. T he rema ining neural s, t hat is, N - II to N -VI a re hexagon al ,
relatively wide a nd nar rowing ca uda lly. T he ir series seem s to be uni nt erru pt ed b ut th e last
plates of the pyga l regio n are lacking. Pl eu ral s wide a nd with lon g ridges para llel to each ot he r.
Periphera ls marked ly lower tha n margi na ls resti ng o n th em.
The shie lds preserved are irr egula r in shape. Ce nt ra ls a re lon ger th an wide, lateral s wide
and marginal s not ver y hig h. No sulci of the praecent ra I shield ha ve been p reserved . If this
shield occurred at all it wa s very sma ll a nd na rr ow a s shown by a small inde nta tion whic h
mig ht correspond to t he sha pe of shield a nd whic h is visib le in th is place.
Neither epiplastra no r ento plastron have been preserved . T he shape of en toplast ron
migh t be reco nstructed o n th e ba sis of a sut ure prese rved alo ng th e edge of t he fract ure, which
wa s probably ver y sma ll as co mpared to the en tire plast ro n. Pl ast ron tria ng ula r a nd shoved
far anteriorly together with sma ll a nd de licate ep iplastra Hyo- a nd hypopl a stra very la rge,
ma ssive and th e sut ures which co nnect them with each ot her are part icu larly d ist inct o n th e
inner side , Massive xiphiplastra are co n nected wit h eac h ot her by a characterist ic, zigzaggi ng
sut ure. T he sulci of shield s poorly preserved , characteristic of Mo ngolemys elegans. Fragmentary sulci of one of the infra marginals are visible o n t he right side.
Di scussion. - The spec imen un der study sh o uld be ass igned to the re p resentat ives of
the fam ily Dermatemydidae. It d isplays t he la rgest simila rity to t he represe ntati ves of MOI/ golemys elegans from t he Upper Nemegt Beds. T he Shee regeen Gashoon Bed s are most probably
older th an the Upper Nernegt Beds, t heir exact age is, ho wever, not det erm ined . T he lack of
a d istinct, characteristic de rm a l sc ulpt ure prevents o ne from a ssig ning the specimen und er
7 - P a la e on t otogi a P ol onica No, 27
98
MAR IAN ML YNARSKI & PAGAM NA RMAN DACH
Fig . 2
M ongolemy s sp., fragment of a ca rapace ; U ppe r Cre taceo us. Sheeregeen Gas hoo n, Gobi Desert (Z. Pa I.No. MgCh/7 I);
x 0.5.
study to M ongolemys elegans. On the othe r hand , the specimen de scribed is sim ila r to Mongolemys elegans in a genera l hab itu s of th e shell a nd in th e size a nd a rra ngement of plates
and shields.
NEW TURTLE REMAINS FROM THE UPPER CRETACEOUS
99
Genus ZANGERLIA MLYNARSKJ, 1972
M onotypic species: Zangerlia testudinimorpha MLYNARSKI, 1972.
Diagnosis - see MLYNARSKI, 1972, p. 85.
?Zangerlia sp.
(Text-fig.
3)
Material. - I) A large, peripheral plate, probably Per-VU or Per-VIII, 5 cm long and
1.9 cm thick (Z.Pal.No.MgChj74); 2) a fragmentary plastron with traces of sulcus of a large
individual (Z.Pal.No.MgCh /90). Both fragments from the Upper Nemegt Beds of the locality
Nemegt, Nemegt Basin, Gobi Desert .
Fig. 3
'lZangerlia sp., peripheral plate; Upper Cretaceous, Upper Nemcgt Beds, Nernegt , Nernegt Basin , Gobi Desert (Z.Pal.
No.MgChj74) ; x I.
Discussion. - Found in the locality Nemegt, these specimens are indicative of the
presence of massive shells covered with a distinct sculpture characteristic of the monotypic
species Zangerlia testudinimorplia, described from the Lower Nemegt Beds (MLYNARSKJ, 1972).
At the first glance, the two fragments resemble the remains of the shells of soft-shelled turtles.
Among the Dermatemydidae with an uncertain taxonomic position, a similar sculpture is
met with only in the genus Tretosternon OWEN , so far known only from the Upper Cretaceous
European marine beds (LYDEKKER, 1889). These remains also cannot belong to the representatives of the genus Anosteira LEIDY since the last-named have a more delicate shell, usually
a finer sculpture and they have not so far been known from the Mesozoic. The only species,
which invites a comparison is a terrestrial representative of the Mongolian Dermatemydidae,
Zangerlia testudinimorpha (see MLYNARSKI, 1972).
7*
lOO
MA R IAN M l. YNARS K I & PAG AM NA R MANDAC H
Family TRI ONYCH IDAE
B EL L ,
1828
Genus TRIONYX G EOFFROY, 1809
Typ e species: Triony x triunguis (FORSKAL, 1775).
Diagnosis - see H UMMEL, 1929, pp. 11 -1 8, a nd M LYNARSKI , 1969, pp. 111 -11 2.
Trionyx sp, a
Materia l. - An almo st co m p lete di scu s o f a small 12 cm long indi vidual (Z .Pa l. No
MgChf76) from the Upper Nemegt Bed s, Nern egt , Nemegt Basin, G obi Desert.
T rionyx sp. b
M aterial. - I) A few larger fragment s o f the di scu s (pleurals and neural s) of med iu m-sized individual s (Z.PaI.No.MgCh j80) ; 2) a left hyopla stron of a large , 13 cm long, indi vidu al
(Z.PaI.No.MgChj81) ; 3) a n almost complet e left hyop lastron a nd hyp opl a stron , 9.5 cm long,
together with long bon es of th e sa me, not ver y large a nd probably yo u ng indi vidual
(Z.PaI.No.MgChj8 3) ; 4) a bo ut twenty fra gm ents o f pleu ral s a nd neural s of large indi vidual s
(Z.Pal.No.MgCh j88) ; 5) six fra gme nts of pla stron o f two indi vidual s va ry ing in size (Z .Pa l. N o .
MgCh j89). All th e rem ain s a re from th e U p per Ne rnegt Bed s, Nemegt. Ne megt Basin , G ob i
Desert.
Di scussion. - The rem ain s of so ft-she lled tu rtl es are met with in t he locality Ne rneg t
more often than in th e mat eri al s from T sagan Khu shu. Ther e are tw o differ en t for ms . One
of them , large Trionyx sp . b characterized by a massive st ru ct ure of she ll wh ich probably reached
80 cm in length. Anoth er , smalle r o ne Trionyx sp . a d oes not exc eed 15 cm in len gth . Th ese
sm all, so ft-shelled turtles are cha racter ist ic of the U p pe r C re ta ceous of th e G obi D esert. Their
assignment to the genu s Triony x G EOFFROY in un certain . It is . not unlikely th at they bel ong
to the genus Plastotn enus COPE, but the material av ai la ble for the st ud ies is insuffici ent for
the reconstruction of the shell. Drawing such conclusion s o f th e ba sis of th e fragm ents preser ved
in thi s material would be absolutely pr em ature.
IN D ET E R M IN AT E MATERIAL
(Text -fig. 4)
Material. -:- A right peripheral plate Per-X of a not ve ry large spe cime n with a st ro ng ly
ser rate ridge of carapace (Z .Pa I.No. M gC h j88) from U ppe r Nemegt Bed s in th e northern part
of the Nemegt loc ality, N em egt Basin , G obi D esert.
Fig. 4
Right peripheral plat e of a n unident ified specimen with st ro ngly serrate ridge of carapace ; Upper C retaceous, Uppe r
Ne rnegt Beds, Nerncgt, Ne meg t Basin, G ob i D esert (Z. Pa I.No .MgChj88) ; >: I . .
N EW T URTL E R EMAI NS FRO M TH E UP PE R CRE TACEOU S
10 1
Discussion. - Th e pre sence o f a single, isolated plate with a sha rp ridge is indicative
o r th e occurrence in the locality under st udy of a so far unknown form with a strongly serrate
ridge o f carapace. So far , none o f both the Me sozoic and Tertiary tu rtle s collected by any
of the Poli sh-Mongolian Palaeontological expeditions have displayed sim ila r characters.
Such a strong ser ra tio n of carapace is a charact er representative of evo lutionarily already more
a dv a nced groups of the subo rde r N eochelydia. Sharp terminations of peripherals are, for insta nce. characteri stic o f the representati ves of th e ge nus Geoeniyda GRA v (subgenus Heosentys GRA v), but they have never before been found in th e Dermatemydidae. The turtle,
from th e she ll o f which th e fragment comes, wa s small and did not exceed 18 cm. Thus, the
pr esence of th ese rem ain s sugges ts th e possibility of the occurrence of on e more form already
closely related to th e Recent tortoi ses of th e groups so far unknown from the Mesozoic, or
st ill another rep resentativ e of the D ermatemydid ae which then occupied a sim ila r ecological
niche a s that o f th e Recent representati ves of the genus Geoetnyda .
Institute of Sys tema tic and Expe rimental Zoo logy
of the Polish Academy of Sciences
Krakow, M arch 1971
Geological Institute, Academy of Sciences
of the M ongolian People's R epublic
Ulan Bat or, Mar ch 1971
R EF ER ENCES
GRADZINSK I, R., KAZMI ERCZAK J. & LEFELD. J. 1968/69. Geog rap hica l and geo logica l data o f the Polish-Mongolian
Palaeontological Expeditions . Result s Po lish-M ongol. Palaeont. Exped ., I. - Palacont , Pol., 19. 33-32. Warszawa.
KIIOSATZKY, L. I. & MLYNARSKI, M. 1971. T he Chelonians from the Upper Cre taceo us deposits of the G obi De sert .
Results ..., Ill. - Ibidem , 25, 131-146.
KIELAN-JAWOROWSKA, Z. & BARSBOLD, R. 1972. Narra tive of the Polish-M ongolian Palaeont ological Expeditions 1967197 1. Results ... . IV. - Ibidem , 27, 5-13.
LYDEK KER, R . 1889. Catalogue of the fossil Rept ilia and Amphibia in the British Mu seum (N atural Hi story). Part Ill,
Chelonia. 1-239, Lond on .
MLYNARSK I. M. 1972. Zanger lia tcstud inimorph a n. gcn.. n. sp.. a primitive land to rto ise from the Up per Cretaceous
of Mongolia. Results .... IV. - Palaeont . Pol. 27, 85-92, Warszawa ,
RozHDEsTVENSKY, A. K . - see PO>I<l\ECTB EllCI\IIii . A . le
I' O;H,I:\ECTBEllCHIIiI, A. K. 1969. Ha IIOIICI\II ;\IIlI03aBpoB
B
l' 0611 . 1-2 90, M ocrcua .