Barun Goyot Research Articles

Description and ecologic analysis of Hollanda luceria, a Late Cretaceous bird from the Gobi Desert (Mongolia)

Avian fossils from the Upper Cretaceous of Mongolia provide significant scientific insight into the evolution of early birds, primarily due to the scarcity of continental interiors with a well-documented avifauna in the Cretaceous record. This paper describes in detail the anatomy and histology of a new taxon of early ornithuromorph bird, Hollanda luceria, from the Barun Goyot Formation at Khermeen Tsav in the Gobi Desert of Mongolia. The new taxon is represented exclusively by hindlimb elements, and is characterized by having elongated hindlimbs with an extremely reduced metatarsal IV and an unusual tibiotarsal-femoral articulation centered on a highly peaked lateral articular facet of the tibiotarsus. Cladistic and ecospace analyses were also carried out in order to infer evolutionary relationships and ecology of this primitive bird. These analyses indicate that the new taxon is a previously undescribed lineage of basal ornithuromorph and an outgroup of Ornithurae ( sensu Chiappe, 2002), which may have had a cursorial lifestyle similar to that of the modern roadrunner, Geococcyx californianus.

Ceratonykus oculatus gen. et sp. nov., a new dinosaur (?Theropoda, Alvarezsauria) from the Late Cretaceous of Mongolia

A new dinosaur, Ceratonykus oculatus gen. et sp. nov. (Parvicursoridae, Alvarezsauria), from the Upper Cretaceous (Baruungoyot Formation) of Mongolia is described based on a fragmentary skeleton. It differs from other alvarezsaurians in many characters, including the short femora, long tarsometatarsals, and considerably reduced third metatarsals. The carpometacarpals contain spikelike bones. The natural endocast of the new taxon shows large acoustic tubercles, the ventral position of the optic lobes in the midbrain, and the absence of a vertical flexure at the brain floor. The data obtained cast doubt on the taxonomic position of alvarezsaurians in the Theropoda.

The tiny horned dinosaur Gobiceratops minutus gen. et sp. nov. (Bagaceratopidae, Neoceratopsia) from the Upper Cretaceous of Mongolia

A new horned dinosaur, Gobiceratops minutus gen. et sp. nov. (Bagaceratopidae, Neoceratopsia), from the Upper Cretaceous Baruungoyot Formation of the Khermin Tsav locality (southern Mongolia) is described based on a 3.5-cm-long skull. The nasal included in the orbital border suggests relationship between the new taxon and Bagaceratops rozdestvenskyi. It is proposed that, unlike other neoceratopsian families, the family Bagaceratopidae is of Paleoasiatic origin.

NEW SPECIMEN OF DELTATHEROIDES CRETACICUS (METATHERIA, DELTATHEROIDA) FROM THE LATE CRETACEOUS OF MONGOLIA

The holotype and only known maxillary dentition of Deltatheroides cretacicus, collected in 1925 from the Upper Cretaceous Djadokhta Formation of Bayn Dzak, Mongolia, has teeth that are badly damaged and worn, obscuring many details of their structure. Reported is a new specimen of D. cretacicus collected in 2000 from the Red Rum (Kholbot) locality near Ukhaa Tolgod, Mongolia that preserves four molars. Although the teeth are worn and have suffered some damage, they preserve details missing from the holotype. Comparisons with other deltatheroidans reveal that D. cretacicus is most similar to Deltatheridium pretrituberculare, known from Bayn Dzak, Ukhaa Tolgod, and the younger Barun Goyot Formation. In 1998, we published the first broadscale phylogenetic analysis of basal metatherians and relevant outgroups. That analysis is updated here with amendments taken from the new specimen of Deltatheroides cretacicus as well as from relevant literature appearing since our publication. As in 1998, the consensus trees in the updated analyses identify deltatheroidans as a basal clade of Metatheria, and Deltatheroides and Deltatheridium as more closely related to each other than to Sulestes from the Coniacian of Uzbekistan. Two isolated upper molars from the Albian–Aptian of Oklahoma and the Oldman Formation of Alberta, Atokatheridium boreni and cf. Deltatheroides sp., respectively, fall at a tetrachotomy with Deltatheroides and Deltatheridium, supporting a North American occurrence for a clade generally held to be Asiatic.

New Avialan Remains and a Review of the Known Avifauna from the Late Cretaceous Nemegt Formation of Mongolia

Small vertebrates have remained relatively poorly known from the Nemegt Formation, although it has produced abundant and well-preserved large dinosaur remains. Here we report three new avialan specimens from the Late Cretaceous (Maastrichtian) of Omnogov Aimag, Mongolia. These fossils were collected from the Nemegt Formation exposed at the locality of Tsaagan Khushu in the southern Gobi Desert. All of the new finds are partial isolated bones with a limited number of preserved morphologies; however, they further understanding of dinosaur diversity in the Late Cretaceous of Mongolia and, specifically, from the Nemegt Formation. The new specimens are described and evaluated in phylogenetic analyses. These analyses indicate that all three fossils are placed as part of the clade Ornithurae.Avialan diversity of the Nemegt Formation is reviewed and briefly compared with that of the underlying Djadokhta and Barun Goyot Formations. These formations have been considered to represent at least two distinct Late Cretaceous environments, with the Nemegt typically interpreted as representing more humid conditions. Ornithurine and enantiornithine birds are known from the Nemegt as well as the Djadokhta and Barun Goyot Formations, although ornithurine remains are more common in the Nemegt. No avialan species known from the Djadokhta, or Barun Goyot, are also known from the Nemegt Formation and, overall, the avialan taxa from these formations do not appear more closely related to each other than to other avialans. Whether these faunal differences are best interpreted as environmental, temporal, or sampling/preservational should be further investigated.

Iguanians From the Upper Cretaceous Djadochta Formation, Gobi Desert, China

ABSTRACT Newly discovered lizard fossils from the Upper Cretaceous Djadochta Formation in the Gobi Desert of Inner Mongolia, China, include early iguanids and agamids that are taxonomically and biogeographically important. Two iguanids reported here, Anchaurosaurus gilmorei, gen. et sp. nov. and Xihaina aquilonia, gen. et sp. nov., document the geologically earliest record of the family from Asia, and extend the fossil record of the group by 11–13 Myr. The geological age and primitive structure of these Cretaceous iguanids, coupled with other material of the same group from the slightly younger Barun Goyot Formation, suggest that the group had a long evolutionary history on the northern continents, and hence, challenge the widely accepted South American origin hypothesis of the Iguanidae (sensu lato). Three taxa of agamids are documented in the new collection: Mimeosaurus crassus Gilmore, 1943, Priscagama gobiensis Borsuk-Bialynicka and Moody, 1984, and Pleurodontagama aenigmatodes Borsuk-Bialynicka and M...

Palaeognathous bird from the Cretaceous of Central Asia

Two skulls of an unquestionably palaeognathous bird were found by the Polish–Mongolian Palaeontological Expedition to the Gobi Desert1. Both specimens originate from the same locality, the beds being referred to as Barun Goyot Formation (?Campanian2). One skull, badly damaged, has been described as Gobipteryx minuta and the new order Gobipterygiformes has been allocated tentatively to the Palaeognathae3. Examination of the second, better preserved, although incomplete skull has now confirmed this allocation. Thus, Gobipteryx is the oldest known palaeognathous bird, the earliest hitherto recorded fossils of this group being of Eocene age4. I estimate the skull of Gobipteryx to be 45 mm long, so that the bird was roughly the size of a partridge.

Possible occurrence of marsupial bones in Cretaceous eutherian mammals

MARSUPIAL bones (epipubes, prepubes) occur in Marsupialia, Monotremata and have also been found in Cretaceous Multituberculata1. Gregory and Camp2 and Romer3 supposed that prepubic cartilages existed in therapsids. Fourie4,5 described a tritylodontid skeleton in which these bones were preserved. Marsupial bones have not been found in eutherian mammals unless one accepts Jellison's6 idea that the baculum is homologous to the epipubic bones. The earliest known eutherian postcranial skeletons come from the Djadokhta Formation (?Santonian) and Barun Goyot Formation (?middle Campanian) in the Gobi Desert, Mongolia7,8 (and are now in the Zaklad Paleozoologii, Warsaw). The most complete are the skeletons of Zalambdalestes and Barunlestes8, both assigned to the family Zalambdalestidae. Study of the structure of their dentition and skulls leaves no doubts that the Zalambdalestidae are members of the Eutheria.

Dinosaur- and mammal-bearing aeolian and associated deposits of the Upper Cretaceous in the Gobi Desert (Mongolia)

The Barun Goyot Formation (? Campanian-Maastrichtian) consists of continental red-bed type sandstones. The formation was interpreted in terms of intertonguing and/or alternating dune deposits and sediments of intermittent lakes and streams. The mega cross-stratified sandstone units which show considerable lateral continuity and little variation of foresets dip were described as buried transverse dunes. They are rather poor in animal fossils. Most dinosaurs and mammals occur in water-deposited interdune sediments. This is due to ecological differences between bare dunes and the interdune depression which had a vegetation cover.

Deltatheroides—like mammals from the Upper Cretaceous of North America

THE family Deltatheridiidae1 has been redifined to include primitive therian mammals of tribosphenic grade referrable to only two genera Deltatheridium1 and Deltatheroides2, from the Djadokhta and Barun Goyot Formations, of uncertain age within the Upper Cretaceous of Mongolia2. The Deltatheridiidae, long considered Eutheria, although of disputed taxonomic dimensions and phyletic position within the infraclass1–5, seem now best classified as therians of metatherian–eutherian grade, but referrable to neither Metatheria nor Eutheria2. A combination of apparent marsupial-like and placental-like features in the known parts of the dentition and skull of members of the Deltatheridiidae insures that the family will be of continuing interest.