Cretaceous Of Mongolia Research Articles

A Palaeogene stem crotaphytid (Aciprion formosum) and the phylogenetic affinities of early fossil pleurodontan iguanians.

Pleurodonta is an ancient, diverse clade of iguanian lizard distributed primarily in the Western Hemisphere. Although the clade is a frequent subject of systematic research, phylogenetic resolution among the major pleurodontan clades is elusive. That uncertainty has complicated the interpretations of many fossil pleurodontans. I describe a fossil skull of a pleurodontan lizard from the Palaeogene of Wyoming that was previously allocated to the puzzling taxon Aciprion formosum, and provide an updated morphological matrix for iguanian lizards. Phylogenetic analyses using Bayesian inference demonstrate that the fossil skull is the oldest and first definitive stem member of Crotaphytidae (collared and leopard lizards), establishing the presence of that clade in North America during the Palaeogene. I also discuss new or revised hypotheses for the relationships of several early pleurodontans. In particular, I examine potential evidence for crown-Pleurodonta in the Cretaceous of Mongolia (Polrussia), stem Pleurodonta in the Cretaceous of North America (Magnuviator) and a stem anole in the Eocene of North America (Afairiguana). I suggest that the placement of the fossil crotaphytid is stable to the uncertain phylogeny of Pleurodonta, but recognize the dynamic nature of fossil diagnosis and the potential for updated systematic hypotheses for the other fossils analysed here.

A new caddisfly of the family Baissoferidae (Insecta: Trichoptera) from the Lower Cretaceous of Mongolia

This article is devoted to the description of a new representative of the family Baissoferidae from the Khutel-Khara locality (Mongolia, East Gobi Aimag) located 75 km southwest of Mount Sain-Shand. The insect-bearing deposits of the Tsagan Tsab Formation, the Lower Tsagan Tsab Subformation in this locality are dated to the earliest Cretaceous, Berriasian-Valanginian. In total, about 3,300 fossil insect imprints of 14 orders were collected from the Khutel-Khara locality. It is important that the fauna of insects has both Jurassic and Cretaceous features. For example, many mayfly and stonefly nymphs that lived there (Sinitshenkova, 1987, 1989) were still typical Jurassic lacustrine forms, while among terrestrial insects, on the contrary, forms that occur mainly in the Lower Cretaceous of Transbaikalia (some rove beetles and scarabaeoids) prevailed (Ponomarenko, 2021). It is especially interesting that many forms are represented in Khutel-Khara, first appearing in the geological record, then widespread in the Lower Cretaceous. This primarily concerns hymenopteran insects (Rasnitsyn, 1990; Kopylov & Rasnitsyn, 2020).

DIRECT EVIDENCE OF THE MOLARIFORM TOOTH REPLACEMENT IN Gobiconodon borissiaki (GOBICONODONTIDAE, MAMMALIA) FROM THE EARLY CRETACEOUS OF MONGOLIA.

The maxillary fragment of eutriconodontan Gobiconodon borissiaki Trofimov, 1978 (Gobiconodontidae) is described from the Early Cretaceous Zuun-Höövör locality in Mongolia (Övörkhangai aimag, Guchin-Us sum). It demonstrates erupting М2RR (second molariform tooth of the third generation) along with the presence of the almost unworn M4R and alveoli of M3R and M5. This is the first direct evidence of the molariform tooth replacement in Gobiconodon from the Early Cretaceous of Mongolia. The CT study of the specimen revealed the absence of mineralized germs of other teeth.

A re-appraisal of Parvicursor remotus from the Late Cretaceous of Mongolia: implications for the phylogeny and taxonomy of alvarezsaurid theropod dinosaurs

Parvicursor remotus Karhu & Rautian, 1996, based on a fragmentary skeleton from the Campanian Barungoyot Formation at Khulsan, in the Gobi Desert of Mongolia, is re-described in detail. Contrary to the original description, we find no evidence that the last dorsal vertebra is opisthocoelous. A biconvex last dorsal vertebra could be present in Parvicursor as in other parvicursorines. The transversely compressed sacral centrum with a sharp ventral keel is the last sacral, not the first sacral as originally alleged. The pelvic bones are not fused at the acetabulum. The holotype of P. remotus, the smallest known alvarezsaurid specimen, is a juvenile individual far from skeletal maturity. New morphological details of Parvicursor that are revealed include a ventral ridge on the posterior dorsal vertebrae; a horizontal supraacetabular crest of the ilium whose anterior end is placed anterior to the most ventrally projecting part of the pubic peduncle; the possible presence of a pubic obturator foramen; an entocondylar tuber on the femur; internal flexor flanges on metatarsals II and IV; a lateral flexor ridge on metatarsal IV; and a proximoventral notch on pedal phalanx IV-1. The Tugriken Shireh alvarezsaurid is not referable to Parvicursor because of its much larger ungual phalanx on the second pedal digit. Kol ghuva is excluded from Alzarezsauridae. The two successive sister taxa for Parvicursor are Ceratonykus and Linhenykus. Ceratonykus differs little from Parvicursor and might be a synonym of the latter. Linhenykus is very similar to Parvicursor in all overlapping skeletal elements. The Parvicursorinae includes all Asian Late Cretaceous alvarezsaurids except Qiupanykus and Nemegtonykus.

A neoceratopsian dinosaur from the early Cretaceous of Mongolia and the early evolution of ceratopsia

Ceratopsia is a diverse dinosaur clade from the Middle Jurassic to Late Cretaceous with early diversification in East Asia. However, the phylogeny of basal ceratopsians remains unclear. Here we report a new basal neoceratopsian dinosaur Beg tse based on a partial skull from Baruunbayan, Ömnögovi aimag, Mongolia. Beg is diagnosed by a unique combination of primitive and derived characters including a primitively deep premaxilla with four premaxillary teeth, a trapezoidal antorbital fossa with a poorly delineated anterior margin, very short dentary with an expanded and shallow groove on lateral surface, the derived presence of a robust jugal having a foramen on its anteromedial surface, and five equally spaced tubercles on the lateral ridge of the surangular. This is to our knowledge the earliest known occurrence of basal neoceratopsian in Mongolia, where this group was previously only known from Late Cretaceous strata. Phylogenetic analysis indicates that it is sister to all other neoceratopsian dinosaurs.

Halszkaraptor escuilliei and the evolution of the paravian bauplan

The evolution of birds from dinosaurs is a subject that has received great attention among vertebrate paleontologists. Nevertheless, the early evolution of the paravians, the group that contains birds and their closest non-avian dinosaur relatives, remains very poorly known. Even the most basal members of one paravian lineage, the Dromaeosauridae, already show a body plan that differs substantially from their closest non-paravian relatives. Recently, the dromaeosaurid Halszkaraptor escuilliei was described from the Cretaceous of Mongolia. Halszkaraptor possesses numerous unserrated premaxillary teeth, a platyrostral rostrum with a developed neurovascular system, an elongate neck, bizarrely-proportioned forearms, and a foreword-shifted center of mass, differing markedly from other paravians. A reevaluation of the anatomy, taphonomy, environmental setting, and phylogenetic position of H. escuilliei based on additional comparisons with other maniraptorans suggests that, rather than indicating it was a semiaquatic piscivore, the body plan of this dinosaur bears features widely distributed among maniraptorans and in some cases intermediate between the conditions in dromaeosaurids and related clades. I find no evidence for a semiaquatic lifestyle in Halszkaraptor. A phylogenetic reevaluation of Halszkaraptorinae places it as the sister clade to Unenlagiinae, indicating the bizarre features of unenlagiines previously interpreted as evidence of piscivory may also represent a mosaic of plesiomorphic, derived, and intermediate features. The anatomy of Halszkaraptor reveals that dromaeosaurids still possessed many features found in more basal maniraptoran and coelurosaur clades, including some that may have been tied to herbivory. Rather than being a semiaquatic piscavore, Halszkaraptor was a basal dromaeosaurid showing transitional features.

Diversity and homologies of corystosperm seed-bearing structures from the Early Cretaceous of Mongolia

New discoveries of corystosperm seed-bearing structures from the Tevshiin Govi locality, Mongolia, which is of Early Cretaceous (Aptian–Albian) age, show that the individual seed-bearing units of Umkomasia mongolica were borne in a cone, as also documented for the very similar reproductive units of Doylea tetrahedrasperma. New material from the Tevshiin Govi locality also documents two additional species of Umkomasia – U. corniculata sp. nov. and U. trilobata sp. nov. – that most likely grew in a different environment to U. mongolica. The occurrence of three different Umkomasia species in the Early Cretaceous of Mongolia, together with other records from the Early Cretaceous of the Northern Hemisphere, indicate that previous concepts of corystosperms, based mainly on material from the Southern Hemisphere, need to be revised. The consistent reproductive architecture of the seed-bearing structures in all three corystosperm species, with a bract subtending a variously modified axis bearing ovules, is similar to the situation in Ginkgo and conifers. These underappreciated architectural commonalities among the reproductive structures of major groups of seed plants are likely significant for a deeper understanding of seed plant evolution and require further exploration.

On Polymorphism of Protoceratops andrewsi Granger et Gregory, 1923 (Protoceratopidae, Neoceratopsia)

Cervical vertebrae of six horned dinosaurs from the Upper Cretaceous of Mongolia, which are identified as Protoceratops andrewsi are examined. It is shown that vertebrae of the same serial number essentially differ in different specimens. The differences concern, for example, the shape of the vertebral centra, proportions of the centra and neurapophyses, inclination of pedicles of the neural arch and long axis of the diapophyseal base relative to the longitudinal axis of the centrum. Comparison has shown that available sample contains representatives of at less four morphotypes.

Bone histology of Protoceratops andrewsi from the Late Cretaceous of Mongolia and its biological implications

Bone histology of Protoceratops andrewsi from the Late Cretaceous of Mongolia and its biological implications

Troodontids (Theropoda) from the Dinosaur Park Formation, Alberta, with a description of a unique new taxon: implications for deinonychosaur diversity in North America

Troodontids are known from Asia and North America, with the most complete specimens from the Jurassic of China and the Cretaceous of Mongolia. North American troodontids are poorly known, and specimens that have been described are isolated elements or partial skeletons with limited material. A new troodontid from the upper Dinosaur Park Formation (upper Campanian) is based on partial skulls, several vertebrae, ribs, gastralia, chevrons, a sacrum, partial pelvis, and partial fore and hind limbs. It is the largest troodontid known, with an estimated height of 180 cm and length of 350 cm. Like other troodontids, it possesses an elongated ambiens process and has a horizontal ventral margin of the postacetabular process. It differs from all other derived troodontids in that the slightly retroverted pubis has a shaft that curves anteroventrally. Some specimens from the Dinosaur Park Formation previously assigned to Troodon are reassigned to the new taxon, including multiple partial crania, an associated dentary and metatarsus, and a partial skeleton. Previously undescribed elements from the lower part of the Dinosaur Park Formation are assigned to the resurrected Stenonychosaurus inequalis. Distinct stratigraphic separation of Stenonychosaurus inequalis and the new taxon indicates a replacement in troodontid fauna, similar to the turnover of large ornithischians in the same formation. The new taxon is phylogenetically more closely related to Mongolian taxa, indicating the replacement of Stenonychosaurus may have been from an earlier Asian form immigrating into North America.

Leaves of Podozamites and Pseudotorellia from the Early Cretaceous of Mongolia: stomatal patterns and implications for relationships

Strap-shaped, parallel-veined leaves of Podozamites and Pseudotorellia are among the most common fossils in Late Triassic to Early Cretaceous floras from the Northern Hemisphere. Podozamites is considered to be the leaf of a voltzian conifer, but its cuticle is poorly known, whereas Pseudotorellia, with a thick cuticle and haplocheilic stomata, is commonly considered to be the leaf of a ginkgoalean. Here we describe the leaf morphology, cuticle and stomata of Podozamites and Pseudotorellia based on excellently preserved material from the Early Cretaceous of central Mongolia. Podozamites harrisii sp. nov. has transversely oriented, paracytic (probably syndetocheilic) stomata that are regularly arranged in longitudinal files. Pseudotorellia resinosa sp. nov. and Pseudotorellia palustris sp. nov. have scattered, longitudinally oriented stomata in which the two guard cells are sunken and surrounded by 2–5 specialized lateral subsidiary cells and 1–3 unspecialized polar cells. Association evidence and similarities in cuticular structure suggest that Podozamites harrisii was produced by the same plant as the seed cone Krassilovia. The distinctive stomatal pattern of Podozamites harrisii and Krassilovia is also seen in some species of Swedenborgia and Cycadocarpidium, suggesting these plants may all belong to the same natural group. Cycadocarpidium, Krassilovia and Swedenborgia have previously been treated as conifers, but their transversely oriented, paracytic stomata hint instead at a possible relationship with Bennettitales and Gnetales.

The family Phryganeidae (Insecta, Trichoptera) from the Mesozoic and Cenozoic of Asia (with a brief worldwide overview of the fossil caddisfly fauna)

The following new taxa of the family Phryganeidae are described: Proagrypnia sinitsae gen. et sp. nov. from the Upper Jurassic or Lower Cretaceous of Russia (Chernovskie Kopi locality) and Baissophryganoides popovi sp. nov. from the Lower Cretaceous of Mongolia (Anda-Khuduk locality). A larval case of Folindusia (Acrindusia) phryganoides sp. nov. from the Paleocene of Russia (Arkhara–Boguchan brown coal field) is described. A worldwide overview of the records of fossil adult insects and larval cases of Phryganeidae is presented.

A historical specimen of enantiornithine bird from the Early Cretaceous of Mongolia representing a new taxon with a specialized neck morphology

We describe Holbotia ponomarenkoi gen. et sp. nov., the first articulated specimen of an enantiornithine bird from Mongolia, unearthed in 1977 from Early Cretaceous deposits and formerly thought to be a pterosaur. The specimen shows a series of morphological details that are either unique to the new taxon or very poorly known for Enantiornithes. A previously unobserved specialized cervical morphology, the development of a crest on the caudal surface of the distal tibia, and the presence of unusually widely spaced small teeth in the lower jaw are unique features of Holbotia. The results of a phylogenetic analysis indicate that Holbotia is more closely related to the Late Cretaceous edentulous Gobipteryx than to the Early Cretaceous enantiornithines with reduced dentition (Longipterygidae), which implies a different evolutionary pathway for the loss of teeth in Enantiornithes, as compared with Ornithuromorpha. The only preserved cervical vertebra of Holbotia ponomarenkoi displays partly ventrally facing prezygapophyseal articular surfaces, otherwise found only in the darters (Anhingidae), which implies an unusually increased degree of neck mobility. Morphology of the palate, described in detail for an Early Cretaceous enantiornithine bird for the first time, is roughly similar to that of Archaeopteryx and non-avian paravians. It shows that the evolution of specialized rostral morphology in Early Cretaceous enantiornithines was possible with retention of the primitive palatal structure, in contrast to modern birds (Neornithes), where the diversification of skull types was coupled with the evolution of several types of palate.http://zoobank.org/urn:lsid:zoobank.org:pub:42845FFC-4E4B-4FEE-9D76-0B5A7D9E127B

Reidentification of avian embryonic remains from the cretaceous of mongolia.

Embryonic remains within a small (4.75 by 2.23 cm) egg from the Late Cretaceous, Mongolia are here re-described. High-resolution X-ray computed tomography (HRCT) was used to digitally prepare and describe the enclosed embryonic bones. The egg, IGM (Mongolian Institute for Geology, Ulaanbaatar) 100/2010, with a three-part shell microstructure, was originally assigned to Neoceratopsia implying extensive homoplasy among eggshell characters across Dinosauria. Re-examination finds the forelimb significantly longer than the hindlimbs, proportions suggesting an avian identification. Additional, postcranial apomorphies (strut-like coracoid, cranially located humeral condyles, olecranon fossa, slender radius relative to the ulna, trochanteric crest on the femur, and ulna longer than the humerus) identify the embryo as avian. Presence of a dorsal coracoid fossa and a craniocaudally compressed distal humerus with a strongly angled distal margin support a diagnosis of IGM 100/2010 as an enantiornithine. Re-identification eliminates the implied homoplasy of this tri-laminate eggshell structure, and instead associates enantiornithine birds with eggshell microstructure composed of a mammillary, squamatic, and external zones. Posture of the embryo follows that of other theropods with fore- and hindlimbs folded parallel to the vertebral column and the elbow pointing caudally just dorsal to the knees. The size of the egg and embryo of IGM 100/2010 is similar to the two other Mongolian enantiornithine eggs. Well-ossified skeletons, as in this specimen, characterize all known enantiornithine embryos suggesting precocial hatchlings, comparing closely to late stage embryos of modern precocial birds that are both flight- and run-capable upon hatching. Extensive ossification in enantiornithine embryos may contribute to their relatively abundant representation in the fossil record. Neoceratopsian eggs remain unrecognized in the fossil record.

Methods for size reconstruction in distorted and damaged vertebrae of fossil tetrapods

The methods for reconstruction of the initial dimensions of distorted and damaged vertebrae in fossil tetrapods are elaborated and tested, using the axial skeleton of horned dinosaurs from the Upper Cretaceous of Mongolia as an example. These methods allow not only more reliable resolution of the problems of vertebrae preservation for processing morphometric data, but also improvement of reconstructions of the vertebral column, as skeletons are mounted for museum exposition.

Cretaceous soft-shelled turtles (Trionychidae) of Mongolia: new diversity, records and a revision

This paper is devoted to the description and revision of material of Cretaceous soft-shelled turtles (Trionychidae) of Mongolia. It includes the description of seven trionychid species, six of which are new, and two new genera: the cyclanorbine Nemegtemys conflata gen. et sp. nov. from the Nemegt Formation (Maastrichtian), and the trionychines Gobiapalone breviplastra gen. et sp. nov. from the Nemegt and Barungoyot (Campanian) formations, G. orlovi from the Baynshire Formation (Cenomanian–Santonian), ‘Trionyx’ baynshirensis sp. nov. from the Baynshire Formation, ‘T.’ gilbentuensis sp. nov. from the Nemegt Formation, ‘T.’ gobiensis sp. nov. from the Nemegt Formation, and ‘T.’ shiluutulensis sp. nov. from an unknown formation (Campanian). In addition, one shell from the ?Baynshire Formation of Khermin Tsav is assigned to Gobiapalone sp. The type material of Amyda menneri is considered to be Trionychidae indet. and Amyda menneri to be a nomen dubium. Finally, we revise other available materials of Cretaceous trionychids from 45 localities in Mongolia. Nemegtemys conflata, if correctly assigned, is the earliest known member of Cyclanorbinae. The two species of the new genus Gobiapalone are included in two phylogenetic analyses of Trionychidae. In both analyses Gobiapalone is monophyletic. In the first analysis, Gobiapalone is placed within Apalonina. In the second analysis, Gobiapalone is sister to Apalonina. Thus, the results of both analyses show that Apalonina, which is a rather advanced and well-supported trionychid clade, or its closest sister taxon (stem-Apalonina), were present in the Late Cretaceous of Asia. These results suggest that most other supra-generic clades of modern trionychids had been established in Asia by the Late Cretaceous. That suggestion is supported by the discovery of a cyclanorbine Nemegtemys conflata in the Late Cretaceous of Mongolia. Finally we summarize the latest data on temporal and geographical distributions of Cretaceous Trionychidae of Asia and North America.http://zoobank.org/urn:lsid:zoobank.org:pub:921DA1C5-C4B2-463D-A49D-608024C6036A

An embryonic enantiornithine bird and associated eggs from the cretaceous of Mongolia

Enantiornithes is the most speciose clade of Cretaceous birds, but many taxa are known from isolated postcranial skeletons. Two embryonic enantiornithine bird skeletons of Gobipipus reshetovi gen. et sp. nov. from the Upper Cretaceous (Campanian) Barun Goyot Formation of the Gobi Desert in Mongolia provide new insights into the anatomy, radiation, and mode of development of early avialans. In recent times, both enantiornithine and ornithuromorph birds are known from the Barun Goyot Formation as well as from the Djadokhta and Nemegt Formations. The 80-million-year-old Gobipipus skeletons encased within eggshells shows several features characteristic of enantiornithine birds. The wing skeleton and shoulder girdle show morphological features indicating that Gobipipus achieved sophisticated powered flight. Gobipipus reshetovi gen. et sp. nov. is quite distinct from the sympatric enantiornithine species Gobipteryx minuta from the same strata in many anatomical features. Phylogenetic analysis of 26 avialan ingroup taxa based on distribution of 202 characters indicate that Gobipipus is a basal member of enantiornithine birds along with Confuciusornis and shares more characters with ornithuromorphs than previously recognized. The embryonic nature of Gobipipus specimens sheds new light on the developmental history of enantiornithine birds. The well-ossified bones of the fore- and hind limbs, and fusion of many skeletal elements indicate a precocial mode of development in Gobipipus. Apparently Gobipipus hatchlings could walk away from the ground nests as soon as they emerged from their eggs. The asymmetry of egg poles are unique features of Gobipipus eggs (oogenus Gobioolithus) among Cretaceous avialans. The microstructure of the shell in Gobioolithus eggs with the embryos of Gobipipus is typical avian (of ornithoid basic type) and less ratite-like in morphology of the spongy layer than is that in the other possible egg-remains of enantiornitine birds (oofamily Laevisoolithidae).

A re-evaluation of goniopholidid crocodylomorph material from Central Asia: Biogeographic and phylogenetic implications

Central Asia is a key area for crocodylomorph evolution, lying midway between the highly documented deposits in Europe and North America, but crocodylomorph fossils from this part of the world are rare. Included among these are specimens collected in the 1970s and 1980s by the Soviet-Mongolian Expeditions in the Jurassic and Cretaceous of Mongolia, Tajikistan, and Kazakhstan. Three species, “Sunosuchus” shartegensis, Kansajsuchus extensus, and Turanosuchus aralensis are redescribed and subjected to phylogenetic analysis for the first time. “Sunosuchus” shartegensis and Kansajsuchus are relatively derived goniopholidids, and part of a pan-east-Laurasian radiation of goniopholidids from which the European goniopholidids subsequently radiated. No characters can be used to distinguish “Sunosuchus” shartegensis from “S.” thailandicus; the two species are therefore synonymized. Turanosuchus aralensis is here considered a nomen dubium. Cladistic analysis suggests that Sunosuchus is polyphyletic, indicating a hig...

Dinosaur eggshell and tooth enamel geochemistry as an indicator of Mongolian Late Cretaceous paleoenvironments

The Late Cretaceous fossiliferous beds of Mongolia's Gobi Desert have yielded spectacular articulated remains of a remarkable diversity of fossil mammals, lizards, turtles, birds, and non-avian dinosaurs. Paleoenvironmental interpretations of the deposits at these localities have ranged from arid wind-blown dune fields to more mesic, moist environments. Among the diversity of fossils, dinosaur eggshells and teeth are commonly found at these localities. Dinosaur eggs, like modern avian eggs, are constructed of biomineralized calcite (CaCO3) and proteins, allowing carbon and oxygen stable isotopes to be quantified to provide information about the environment in which the egg-laying animals were living. Here it is shown that dinosaur eggshell and teeth from the Djadokhta and Nemegt Formations have not been significantly altered and reflect an environment of dry dunes during deposition of the Djadokhta Formation and a more mesic stream environment for conditions in the Nemegt Formation. Carbonate nodules from the same eggshell-bearing layers also independently reflect a similar environmental signal. This study represents the first geochemical analysis of dinosaur remains from the Cretaceous of Mongolia and illustrates the potential of utilizing dinosaur fossil geochemistry of both eggs and teeth to reconstruct Mesozoic environments.

A redescription and phylogenetic reinterpretation of the fossil lizard Hoburogekko suchanovi Alifanov, 1989 (Squamata, Gekkota), from the Early Cretaceous of Mongolia

ABSTRACT Additional information about one of the oldest known gecko-like lizards, Hoburogekko suchanovi from the Early Cretaceous of Mongolia, is provided in light of recent advances in the understanding of gekkotan osteology. The phylogenetic affinities of this taxon were assessed by adding it into an existing morphological data set of 224 taxa coded for 364 characters. The effects of character ordering and scoring on tree topology and the composition of Gekkonomorpha were also explored. The results of the analysis indicate that Gekkonomorpha is highly unstable and additional revision of stem gekkotans (e.g., Parviraptor, Gobekko) is required to refine the basal relationships of this clade. Like modern gekkotans, Hoburogekko possess a tubular frontal bone. In contrast to extant gekkotans, the Meckelian canal is only partially fused and may represent an incipient form of the gekkotan condition. The posterior shelf of the maxilla is wider than in modern gekkotans, perhaps related to a plesiomorphically large jugal. The short, rounded snout may indicate a lifestyle as found in some modern gekkotans found in equivalent xeric environments to the inferred paleoenviroment of the Höövor (Mongolia) locality during the Early Cretaceous.