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Louis L. Jacobs,Octavio Mateus,Michael J. Polcyn,Anne S. Schulp,Miguel Telles Antunes,Maria Luisa Morais,Tatiana da Silva Tavares 한국고생물학회 2006 고생물학회지 Vol.22 No.1
아프리카 사하라 지역에 척추동물화석을 배태한 백악기 지층의 노출은 매우 적다. 왜냐하면 대륙의 상당 부분을 선캄브리아기 변성암 육괴가 넓게 분포하고 있을 뿐 아니라 젊은 시대의 지층들과 식물들이 이들 백악기 지층을 덮고 있기 때문이다. 그러나 백악기 해성층과 육성층이 넓게 발달한 지역이 앙골라 해안과 내륙 사이에서 발견되었다. 앙골라의 주변부는 곤드와나 대륙이 갈라지면서 남대서양이 확장되는 것과 관련되어 형성되었다. 백악기 퇴적층은 해양지각의 덮고 있어 시대는 매우 제한적이며 가장 오래된 지층은 지자기대 (magnetozone) M3 (대략 128Ma, Barremian) 보다 오래되지 않았다. 얕은 해양퇴적 환경은 해안가에 드러나 있지만 내륙으로 점점 육성퇴적 환경이 증가한다. 상어화석이외에는 앙골라에서 척추화석이 거의 발견되지 않았었다. 예외적인 화석은 앙골라 북부에서 산출된 후기 Turonian 모사사우루스 Angolasaurus bacagei와 Tylosaurus iembeensis이다. 이들 화석은 가장 초창기에 진화된 모사사우루스들이기 때문에 중요하다. 최근 야외조사를 통해 새로운 Angolasaurus의 머리뼈뿐만 아니라 상어, 물고기, 수장룡, 새로운 거북의 머리뼈, 앙골라에서는 처음 발견되는 용각류의 앞다리가 발견되었다. 앙골라 남부에는 백악기에서 팔레오세 경계까지 퇴적된 해양퇴적층이 발견된다. Vertebrate-bearing fossiliferous outcrops of Cretaceous age in sub-Saharan Africa are rare because of younger superficial deposits, vegetation cover, and the widespread occurrence of Precambrian metamorphic plateau basement comprising much of the continent. However, one area of extensive marine and nonmarine Cretaceous exposures is found between the plateau and the coast in Angola. The Angolan margin was formed in conjunction with the breakup of Gondwana and subsequent growth of the South Atlantic. Cretaceous deposits are constrained in age by the emplacement of oceanic crust, which began no later than magnetozone M3 (approximately 128 Ma, Barremian). Shallow marine facies are exposed in sea cliffs but equivalent facies become increasingly terrestrial inland. Few vertebrate fossils have been described from Angola aside from sharks. Notable exceptions are the late Turonian mosasaurs Angolasaurus bocagei and Tylosaurus iembeensis from northern Angola. Those taxa are significant because they are among the earliest derived mosasaurs. Recent field work led to the discovery of a new skull of Angolasaursus as well as sharks, fish, plesiosaurs, the skull of a new taxon of turtle, additional mosasaurs, and the articulated forelimb of a sauropod dinosaur, the first reported dinosaur from Angola. In southern Angola, marine sediments spanning the Cretaceous-Paleogene boundary are found.
Lee, Hang-Jae,Lee, Yuong-Nam,Adams, Thomas L.,Currie, Philip J.,Kobayashi, Yoshitsugu,Jacobs, Louis L.,Koppelhus, Eva B. Elsevier 2018 Palaeogeography, palaeoclimatology, palaeoecology Vol.494 No.-
<P><B>Abstract</B></P> <P>A theropod tracksite was discovered in the Nemegt Formation (Maastrichtian) at Bügiin Tsav, Mongolia by the Korea-Mongolia International Dinosaur Project in 2009. A total of 67 tracks (14 trackways [one didactylous, 13 tridactylous] and 12 isolated tracks) belonging to four ichnomorphotypes were mapped on a single horizon. This indicates at least four different theropod trackmakers lived in the same area at the same time. This tracksite consists of laminated gray mudstone-yellowish brown siltstone couplets interbedded with eolian yellowish brown sandstone deposited on a distal floodplain. Abundant footprints with V-shaped profiles (cross-section) within in the vertical section indicate that dinosaurs repeatedly walked across in this area. Before the discovery of the tracks, the site was illegally excavated by fossil poachers, a widespread problem in the Gobi Desert. During excavation of the track horizon, a clenched, inclined <I>Gallimimus</I> foot skeleton was found in the mudstone, extended down 20cm below the track-bearing sandstone layer. The occurrence of tracks closely associated with body fossils is unusual and taphonomically intriguing. It is possible that the foot skeleton represents an animal that died in its tracks. However, the depth of the foot in mud is probably too shallow for the animal to have been mired. Sedimentological and taphonomic evidence also suggests that the pes of <I>Gallimimus</I> may have passed straight through the track-bearing sandstone layer. The inclined right pes indicates that the body lay on its left side on the substrate. During decomposition in the mud, all digits were flexed but the distal phalanges were stuck and anchored in the stiff lower mud. Consequently, as more proximal phalanges were able to accommodate flexing, they were pulled away and dislocated from the anchored distal phalanges. Subsequent trampling by dinosaurs in the track-bearing sandstone would have further distorted the underlying foot.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The first report of theropod trackways from the Nemegt Formation in Bügiin Tsav, Mongolia </LI> <LI> Taphonomic interpretation of a <I>Gallimimus</I> foot skeleton associated with theropod tracks </LI> <LI> An interpretation of disarticulation and distortion of the foot skeleton is proposed. </LI> </UL> </P>
Diagenesis of dinosaur eggshell from the Gobi Desert, Mongolia
Graf, John,Tabor, Neil J.,Ferguson, Kurt,Winkler, Dale A.,Lee, Yuong-Nam,May, Steven,Jacobs, Louis L. Elsevier 2018 Palaeogeography, palaeoclimatology, palaeoecology Vol.494 No.-
<P><B>Abstract</B></P> <P>In order to test for paleoenvironmental and paleoecological parameters important in dinosaur evolution, thirty-four fragments of dinosaur eggshell, paleosol carbonates from six localities, and calcite crystals from inside a dinosaur femur were collected from the Campanian to Maastrichtian Baruungoyot and Nemegt formations, Gobi Desert, Mongolia. The samples were examined for diagenesis using light microscopy, SEM, and cathodoluminescence, and each was analyzed for δ<SUP>13</SUP>C and δ<SUP>18</SUP>O values. Eggshell isotope values plot along two trends of enrichment, with paleosol carbonate nodule values plotting along locality specific trends. Convergence of the trends suggests similar initial conditions among localities. Permian-age detrital zircons in the fossiliferous sediment suggest that enriched eggshell and paleosol carbonate nodule δ<SUP>13</SUP>C values may have been caused by phreatic zone diagenetic alteration by waters with an aqueous bicarbonate component derived from interaction and dissolution of Permian calcareous marine host rocks. Our hypothetical model for eggshell diagenesis assumes a stable carbon- and oxygen-isotope domain space delimited by three end members: (1) apparently unaltered eggshell with primary microstructure, (2) non-luminescent eggshell with no preserved microstructure, and (3) luminescent eggshell with no preserved microstructure. The two end members showing no preservation of microstructure indicate different phases of diagenetic alteration in the presence of vadose and phreatic waters. None of the samples analyzed can be shown to be sufficiently unaltered for analysis using standard techniques. Biologically, eggshell is porous to facilitate the movement of gases while an embryo is developing within the egg. Geologically, that same property allows the flow of diagenetic ground waters, which modifies the primary isotopic signature of eggshell.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Stable isotopes in dinosaur eggshell are used to infer paleobiology and paleoenvironment. </LI> <LI> However, porosity that facilitates movement of gases, makes fossil eggshells prone to diagenesis. </LI> <LI> δ<SUP>13</SUP>C and δ<SUP>18</SUP>O in Mongolian Cretaceous eggshell from the Gobi Desert indicate rampant diagenesis. </LI> <LI> Eggshell was subjected to shallow-burial, vadose and phreatic zone diagenesis. </LI> </UL> </P>
Su-Hwan Kim,Yuong-Nam Lee,Jin-Young Park,Sungjin Lee,Dale A. Winkler,Louis L. Jacobs,Rinchen Barsbold 대한지질학회 2021 대한지질학회 학술대회 Vol.2021 No.10
Compared to abundant dinosaur faunas, fish materials are scarce in the Nemegt Formation (Upper Cretaceous) of Mongolia. Only one report was about isolated centra assigned to the Hiodontidae (Osteoglossomopha). Here we report new additional fish materials collected from the Nemegt Formation during the Korea-Mongolia International Dinosaur Expedition (KID, 2006~2010). They include skull parts (quadrate, premaxilla, and dentary), isolated and articulated centra, and a caudal fin. New specimens appear to be the same taxon as the reported old samples based on morphological similarities in the abdominal centra. However, the suggested features for identifying the hiodontids are erroneous. All specimens represent a new genus and species of osteoglossomorph fish, Harenaichthys lui gen. et sp. nov. Furthermore, phylogenetic analysis reveals that Harenaichthys is a basal member of the osteoglossomorphs instead of being included in the hiodontids. By identifying a fish centrum associated with the theropod dinosaur Raptorex kriegsteini as Harenaichthys, we concluded that R. kriegsteini comes from the Nemegt Formation. Unusual monospecific occurrences of Harenaichthys allow us to understand their paleoecology and paleobiogeography better. In addition, the pathologic features seen on some centra of Harenaicthys indicate that they suffered from various diseases in life.