Morphometric analysis of the teeth and taxonomy of the enigmatic theropodRichardoestesiafrom the Upper Cretaceous of Uzbekistan (original) (raw)
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Journal of Vertebrate Paleontology, 2019
Richardoestesia is an enigmatic theropod dinosaur originally described on the basis of a pair of dentaries (holotype of R. gilmorei Currie et al., 1990) and isolated distinctive teeth, which are abundant in the Upper Cretaceous of North America. Richardoestesia asiatica (Nesov, 1995) is represented by numerous isolated teeth from the Upper Cretaceous Khodzhakul, Bissekty, and Aitym formations of Uzbekistan. Richardoestesia asiatica shows the typical features of the genus, including small mesial and distal denticles (on average 28.4 and 34.5 denticles per 5 mm, respectively), rectangular or knob-like denticles, and an apically convex distal margin of the tooth crown. The sample of R. asiatica has a large proportion of straight teeth (morphotype A) and includes several types of recurved teeth related to their position in the jaws (morphotypes BE). This species differs from R. gilmorei in the presence of straight teeth and fully serrated mesial carinae. Richardoestesia asiatica cannot be distinguished from R. isosceles Sankey, 2001, which we consider a nomen dubium due, in part, to the imperfect nature of its holotype. Discriminant function analysis (DFA) of dental measurements found no distinction between the samples from Khodzhakul and Bissekty formations. In DFA including North American samples, the morphospace of R. asiatica completely overlaps that of the sample from the Lance Formation (Maastrichtian) of Wyoming and only partly overlaps with that of the sample from the Milk River Formation (Santonian) of Alberta.
Theropod teeth from the Lower Cretaceous Ilek Formation of Western Siberia, Russia
Trudy Zoologičeskogo instituta, 2019
A sample of 136 isolated theropod teeth from nine vertebrate localities within the Lower Cretaceous (Barremian-Aptian) Ilek Formation in West Siberia, Russia, can be separated into five dental morphotypes referred to five or six theropod taxa based on morphological characters. The Morphotype A includes small to large lateral teeth with relatively large distal denticles and smaller mesial denticles. Some of these teeth can be attributed to the Dromaeosauridae, while other teeth may belong to a basal member of the Tyrannosauroidea. The distinctly smaller lateral teeth referred to the Morphotype B are similar with Morphotype A in most respects but differ in the lack of mesial denticles and mesial carina, or having a lingually displaced mesial carina. These teeth may belong to juvenile individuals of the same dromaeosaurid taxon. The teeth belonging to Morphotype C also lack mesial denticles and differ from Morphotype B by a flattened area on the lingual side, which is also often present on the labial side. These teeth may belong to either Troodontidae or Microraptorinae, or to both groups. The mesial and lateral teeth of Morphotype E are characterized by unserrated mesial and distal carinae. These teeth most likely belong to a distinct taxon of Troodontidae with unserrated dentition. The teeth of the Morphotype D include mesial teeth with the mesial carina displaced lingually at various extent and denticles present on both carinae. The teeth with moderately displaced lingual carina can be referred to the same dromaeosaurid taxon, which lateral teeth represented by Morphotype A. The teeth with more displaced mesial carina and deeply U-shaped basal crown section belong to an indeterminate Tyrannosauroidea.
Canadian Journal of Earth Sciences, 2013
Upper Cretaceous (Cenomanian-Turonian) formations in the Kyzylkum Desert of Uzbekistan, especially the Bissekty Formation at Dzharakuduk, have yielded a great diversity of continental vertebrates, including dinosaurs. Underwater screening of the sandy matrix has recovered many dinosaurian teeth. Here we describe and illustrate two types of enigmatic theropod teeth that are referable to Paronychodon and Richardoestesia, respectively. Both of these tooth taxa are well known from the Late Cretaceous of North America and possibly represent stages in the development of the teeth of various paravian theropods. Confirmation of this hypothesis awaits discovery of more complete jaws.
Acta Paleontologica Polonica, 2013
Isolated teeth from vertebrate microfossil localities often provide unique information on the biodiversity of ancient ecosystems that might otherwise remain unrecognized. Microfossil sampling is a particularly valuable tool for documenting taxa that are poorly represented in macrofossil surveys due to small body size, fragile skeletal structure, or relatively low ecosystem abundance. Because biodiversity patterns in the late Maastrichtian of North American are the primary data for a broad array of studies regarding non-avian dinosaur extinction in the terminal Cretaceous, intensive sampling on multiple scales is critical to understanding the nature of this event. We address theropod biodiversity in the Maastrichtian by examining teeth collected from the Hell Creek Formation locality that yielded FMNH PR 2081 (the Tyrannosaurus rex specimen “Sue”). Eight morphotypes (three previously undocumented) are identified in the sample, representing Tyrannosauridae, Dromaeosauridae, Troodontidae, and Avialae. Noticeably absent are teeth attributed to the morphotypes Richardoestesia and Paronychodon. Morphometric comparison to dromaeosaurid teeth from multiple Hell Creek and Lance Formation microsites reveals two unique dromaeosaurid morphotypes bearing finer distal denticles than present on teeth of similar size, and also differences in crown shape in at least one of these. These findings suggest more dromaeosaurid taxa, and a higher Maastrichtian biodiversity, than previously appreciated.
Cretaceous Research, 2015
The oviraptorosaurian theropod Caenagnathasia martinsoni is the least common dinosaur taxon in the Late Cretaceous (Turonian) vertebrate assemblage from the Bissekty Formation of the Kyzylkum Desert, Uzbekistan. The dentaries show numerous caenagnathid synapomorphies, including a fused dentary symphysis bearing distinct vascular grooves and associated foramina on its lingual surface, a lingual triturating shelf on the dentary, and extensive pneumatization of the dentary. Cervical and dorsal vertebrae attributed to C. martinsoni show a structure typical for Caenagnathoidea, whereas a referred partial femur is relatively plesiomorphic in having a large, finger-like anterior (lesser) trochanter separated from the greater trochanter. A referred synsacrum has only four vertebrae but may represent an immature individual. Caenagnathasia martinsoni is closely related to the clade comprising the North American Campanian-Maastrichtian caenagnathids.
Anais da Academia Brasileira de Ciências, 2002
The genera Nuculites and Cucullella have originated in different geographic areas, with the oldest record found in the Llandovery (Lower Silurian). The former was reported in Gondwana with two subgenera, Nuculites and Trilobonuculites, while the latter is found in Avalonia. Due to environmental and tectonic factors, those taxa became associated and distributed throughout Gondwana, Avalonia, Kazakhistan and Laurussia from the Late Silurian to the Late Devonian. The subgenus Trilobonuculites appeared firstly at the Pitinga Formation, Amazon Basin, Brazil, and the subgenus Nuculites is only recorded in the Silurian from the Tabuk Formation, Saudi Arabia. Cucullella was found in the Ross Brook Formation of New Scotia, Canada. Since the Late Silurian (Ludlow), which is marked by a marine transgression, Trilobonuculites and Cucullella started to occur associated, invading other paleocontinents, confirmed by the presence of Cucullella in the Gondwana (Bolivia) and Trilobonuculites in Avalonia (New Scotia). This suggests that the environment in these areas became more uniform due to the rise of the sea level and the narrowing of the ocean Rheic. The Silurian-Devonian boundary is marked by a marine regression followed by a new transgression, with maximum in the Frasian, and the collision of Avalonia/Baltica and Laurentia forming Laurussia. At this point, the subgenus Nuculites reappeared. Still in the Lower Devonian (Pragian-Emsian), the genus Nuculites diversified, dominating by the subgenus Trilobonuculites, while Cucullella was only represented by a sole species from Kazakhistan. In the Middle Devonian (Eifelian-Givetian) the subgenus Nuculites predominated while Trilobonuculites was restricted to the Maecuru Formation (Brazil). The only species of Cucullella dispersed to the oriental Laurussia and North and Occidental Gondwana. In the Late Devonian (Frasnian), the occurrence of these taxa was restricted to the Armorican Massif, Northeastern of Brazil and some doubtful occurrences in Bolivia. At that time, the oceans deepened, dysaerobic and anoxic environments spread out and Gondwana and Laurussia were approaching. These factors, associated with thermal stress, led to extinction of several taxa at the Frasnian/Fammenian boundary, including those studied here. The paleogeographic distribution of Nuculites and Cucullella agrees with the sea level curves and the movement of the continents suggested to have taken place during the Silurian and Devonian.-(
Therian Femora from the Late Cretaceous of Uzbekistan
Acta Palaeontologica Polonica, 2012
Femora referable to metatherians and eutherians recovered from the Bissekty Formation, Dzharakuduk, Kyzylkum Desert, Uzbekistan (90 Mya), are described. Fourteen isolated specimens were sorted based on size and morphology into groups that likely correspond to the species level or higher. Groups were then tentatively assigned to taxa known from teeth, petrosals, and/or other postcrania at these localities. One distal femur of a small arboreal metatherian, and several eutherian distal femora that probably represent zhelestids and/or zalambdalestids were identified. With the exception of one proximal femur that is similar in some aspects to the zalambdalestid Barunlestes, and a previously described multituberculate specimen, all other proximal femora from the Bissekty Formation exhibit a metatherian−like morphol− ogy. The dental record currently suggests the presence of twelve eutherian species and only one metatherian at Dzharakuduk, whereas the humeral and crurotarsal evidence supports the presence of at least two or four metatherian spe− cies, respectively. Given the sample size of the proximal femora, the morphological diversity present, and the over− whelming presence of eutherians at these localities, it is highly unlikely that the overwhelming majority of proximal femora actually represent metatherians. Therefore, this sample may suggest that the metatherian proximal femoral condi− tion is primitive for Theria and that some eutherian taxa (probably including Zhelestidae, which are dentally most abun− dant at these localities) retain this condition.
The Anatomical Record Part A: Discoveries in Molecular, Cellular, and Evolutionary Biology, 2005
Isolated theropod teeth are common Mesozoic fossils and would be an important data source for paleoecology biogeography if they could be reliably identified as having come from particular taxa. However, obtaining identifications is confounded by a paucity of easily identifiable characters. Here we discuss a quantitative methodology designed to provide defensible identifications of isolated teeth using Tyrannosaurus as a comparison taxon. We created a standard data set based as much as possible on teeth of known taxonomic affinity against which to compare isolated crowns. Tooth morphology was described using measured variables describing crown length, base length and width, and derived variables related to basal shape, squatness, mesial curve shape, apex location with respect to base, and denticle size. Crown curves were described by fitting the power function Y ϭ a ϩ bX 0.5 to coordinate data collected from lateral-view images of mesial curve profiles. The b value from these analyses provides a measure of curvature. Discriminant analyses compared isolated teeth of various taxonomic affinities against the standard. The analyses classified known Tyrannosaurus teeth with Tyrannosaurus and separated most teeth known not to be Tyrannosaurus from Tyrannosaurus. They had trouble correctly classifying teeth that were very similar to Tyrannosaurus and for which there were few data in the standard. However, the results indicate that expanding the standard should facilitate the identification of numerous types of isolated theropod teeth. 2005 Wiley-Liss, Inc.