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Fwd: About tyrannosaurids from Tsagayanskaya Svita




To: Tim Donovan I found in Yuri Bolotsky (Blagovestchinskian locality of Cretaceous
dinosaurs // Continental Cretaceous of the USSR: Coll. of Res. Papers,
Vladivostok, 1990, Pp. 109-113): "-In locality, were collected remains
of carnivorous dinosaurs represented with separate vertebrae, phalanges
and teeth. Ones seem felt into locality following resorption of root
parts and falling out of living reptiles. The most of them belongs to
the Tyrannosauridae specimens, judging by size seem compete with the
well-known genus Tarbosaurus from Mongolia.

If T. bataar remains fell into the locality they were presumably from a higher stratigraphic level and a slightly later period-Nemegtian. The Dinosauria also indicated that tyrannosaurs are not known from the Tsagayan but from an unnamed unit, considered of Nemegtian age by Lucas.




In collection are also
remains of smaller tyrannosaurids, possibly belongs to individuals of
younger age." Here Bolotsky wrote about remains of 2 species of the very
little theropods (I suppose - troodontids?), one fragment of large tooth
of a dromaeosaurid and some smaller teeth of its relatives, a Lev
Nessov's find of the fragment of small sauropod tooth, fragments of
Trionychidae and Dermathemydidae shells, undeterminable remains of
crocodyles, but the most amount of bones belongs to hadrosaurs of
various size (no less than 30 individuals).
Besides, I have my private translate of most chapters of the Lev
Nessov's last work "Dinosaurs of Northern Eurasia: new data about
assemblages, ecology and palaeobiogeography"written in 1995. Here Nessov
wrote:
Blagovestchensk, a south part of the city, Amurskaya Oblast, Russia. A
lower (or middle?) part of the Tsagayanskaya Svita. The Upper
Cretaceous, Middle Maastrichtian (Nessov et Golovnyova 1990), but not
the Cenomanian-Lower Senonian (Bolotsky et Moiseenko 1988), since in
composition of the complex are turtles Mongolemys.

This is certainly consistent with a Nemegtian age but I note on page 354 of The Age of Dinosaurs in Russia and Mongolia Sukhanov doubted Nesov's identification of Mongolemys from the Amur region.




Undoubtedly, the
material is Cretaceous, since sometimes in the locality are found bones
of postcranial skeleton of dinosaurs in the natural articulation with
each other (Bolotsky et Moiseenko 1988), but remains here are not
reworked into the Quaternary deposits (see Rozhdestvensky 1957). Data on
containing of rare-ground and other elements in bones (Bolotsky et
Moiseenko 1988) are given here, their presence is conditioned by
processes of the bone diagenesis, not by accumulation of unpeculiar
elements for bones during the life. Small theropods (Rozhdestvensky
1957), troodontids, tyrannosaurids (Bolotsky et Moiseenko 1988), the
latter are supposedly belonged to Tarbosaurus sp., a sauropod? (one
fragment of the narrow and long tooth), large hadrosaurids
(Rozhdestvensky 1957; Bolotsky et Moiseenko 1988), they were preliminary
closed to Bactrosaurus and Aralosaurus (Bolotsky 1988), definition has
more precisely to the representative of the Lambeosaurinae having a
similarity with Corythosaurus which was named Amurosaurus riabinini
Bolotsky et Kurzanov (nom. nud.?) Bolotsky 1990b), the second form seems
from the Saurolophinae Bolotsky 1990a). Remains of bones of dinosaurs,
supposedly from regurgitations of large theropods. Data on the
Sagibovsky Boguchan and Kordon heights (Amurskaya Oblast) see part
4.5.202.
Both authors belongs the Tsagayanskaya Svita to the Middle
Maasstrichtian.
I wrote a paper on co-evolution of Theropoda and Thyreophora. It is very
interesting due to the numerous comparing of taxa of these two groups on
various chrono-geographical zones. In normal situation, or stable
communities, theropods and armored dinosaurs were developed with high
level of interdependency. But such events as sudden appearances of
immigrants or replacement, as a result of quite different causes, of
large herbivores by taxa which were evolved in "subdominant complexes"
(by Olson), might break established steady bonds, leadind to the
destabilization of all the biocenoses as were at the Middle
Maastrichtian (titanosaurids settling along the North America) or at the
Middle Tatarian (occupation by pareiasaurids of the ecological niche of
disappeared deinocephalians) or at the Early Norian (occupation by
prosauropods and, possibly, aetosaurs of the ecological niche of
dicynodonts). All these events lead to an appearance of large,
specialized predators, as well as, consequently: Tyrannosaurus;
Inostrancevia; some large ceratosaurians (e.g. Liliensternus) and last
largest rauisuchoids). As a result, all other herbivores had to form
extra adaptations for resistance to dangerous predators. All that, after
all, lead them in an evolutional impasse and further in a dead-end when
both preys and predators were eliminated.
>From the middle of June to the one of July, I was in my field
expedition Paleontologists from Saint Petersburg were here. This
year they made an excellent and wery strange find: when they collect
firewood for campfire on a dump near Gusinoozersk town, they've come
upon a big sandy block and decide to investigate it. Suddenly, when
opening, appeared some bones. And how their surprise was when, finally,
they revealed almost complete skeleton of Kirgizemys, a turtle!!! It is
seems the most complete skeleton of Mesozoic tetrapods ever found in
Transbaikalia! I also found, in another locality, the Dinosaur Ravine, a well-preserved
hyoplastron of Kirgizemys. Later, St Petersburg paleontologists
found nothing in this site.
One of St Petersburgers, Pavel Skutchas, went by Jeep to other
Transbaikalian localities. He and his student assistants dug up in the
Krasnyi Yar many bones of
dromaeosaurids, ?allosaurids, two forms of sauropods, turtles, fishes -
almost the same groups as in Gusinoe. Although they didn't find mammals,
they worked brilliantly. This is my news. Alexei


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