Itat Formation

Itat Formation
Stratigraphic range: Bajocian-Bathonian
~170–166 Ma
↓
TypeGeological formation
Sub-unitsLower, Middle and Upper members
UnderliesTyazhin Formation
OverliesIlan Formation
ThicknessSeveral hundred metres
Lithology
PrimarySandstone, mudstone, coal
OtherSiltstone
Location
Coordinates55°42′N 89°12′E / 55.7°N 89.2°E / 55.7; 89.2
Approximate paleocoordinates58°12′N 86°42′E / 58.2°N 86.7°E / 58.2; 86.7
RegionSiberia
Country Russia
ExtentKrasnoyarsk krai, Nazarovo depression, SE West Siberian basin
Type section
Named forItatsky
Itat Formation is located in Russia
Itat Formation
Itat Formation (Russia)
Itat Formation is located in Krasnoyarsk Krai
Itat Formation
Itat Formation (Krasnoyarsk Krai)

The Itat Formation (Russian: итатская свита) is a geologic formation in western Siberia. It was deposited in the Bajocian to Bathonian ages of the Middle Jurassic.[1] Dinosaur remains are among the fossils that have been recovered from the formation, including the proceratosaurid Kileskus, as well as fish, amphibians, mammals and many other vertebrates.[2] The formation is noted for bearing significant coal reserves, with large open pit coal mines extracting lignite from the unit currently in operation.

Lithology

The lower section of the formation is around 50–130 m thick, and consists of light grey sandstones with gravel, siltstone and rare coal beds.[3] At the Dubinino locality, the 50 m exposed section of the upper part of the formation shows an irregular rhythmic alteration of fine grained sandstone, siltstone and mudstone and coal seams typically a few tens of cm's but up to several meters thick.[1] The deposit is located on the South Eastern margin of the West Siberian basin[4]

Locality

Most of the fossils were found in the overburden of Berezovsk coal mine[ru], which is located in southern Krasnoyarsk Krai (Sharypovsky District) near the border with Kemerovo Oblast. The deposit is stratigraphically located in the upper member of the formation. The fossiliferous level of the locality is located above thick (> 50 m) coal seams and consists of unconsolidated silt and sand, which were deposited on an alluvial plain. Due to the fluvial origin of the sediment the remains are disarticulated and often are water worn, though they are mostly well preserved, which suggests they had not been significantly transported.[5] The fossils were largely obtained by screenwashing of the debris. 10-15 tons of material have been processed so far.

Paleobiota

Taken from[2] unless otherwise noted.

Fish

Fish of the Itat Formation
Genus Species Location Stratigraphic position Abundance Notes Images
Hybodus Indeterminate Berezovsk coal mine Upper Member Partial tooth
Acipenseriformes Indeterminate Berezovsk coal mine Upper Member Scales
Amiiformes Indeterminate Berezovsk coal mine Upper Member "Abundant vertebrae, jaws and vomer fragments, as well as isolated teeth, and numerous isolated rhomboidal scales"
Dipnoi Indeterminate Berezovsk coal mine Upper Member One complete upper tooth plate, several tooth plate fragments
Palaeonisciformes Undescribed Berezovsk coal mine Upper Member Many partial skeletons Similar to Palaeoniscinotus and Pteroniscus

Amphibians

Amphibians of the Itat Formation
Genus Species Location Stratigraphic position Abundance Notes Images
?Eodiscoglossus[6] Indeterminate Berezovsk coal mine Upper Member Atlantal centrum Frog
Kiyatriton[7] K. krasnolutskii Berezovsk coal mine Upper Member Dentary, atlantes, trunk vertebrae and fragmentary cranial and postcranial bones Formerly known as "Berezovsk salamander B"; genus also known from Early Cretaceous Ilek Formation. Crown group Salamander
Urupia[8] U. monstrosa Berezovsk coal mine Upper Member Dentary, femur, an incomplete atlas, an anterior fragment of the left dentary, and fragments of trunk vertebrae Estimated length of 480-560 centimetres Stem-Salamander
Egoria [9] E. malashichevi Berezovsk coal mine Upper Member Atlantal centra, trunk vertebrae Formerly known as "Berezovsk salamander A" Possibly neotenic Stem-Salamander

Turtles

Turtles of the Itat Formation
Genus Species Location Stratigraphic position Abundance Notes Images
Annemys A. variabilis[10] Berezovsk coal mine Upper Member Thousands of isolated bones and several fragmented specimens, including three partial braincases and larger fragments of connected shell parts[11] Xinjiangchelyid
Testudines Indeterminate Berezovsk coal mine Upper Member Likely one or two taxa distinct from Annemys.[11]

Lepidosauromorphs

Lepidosauromorphs of the Itat Formation
Genus Species Location Stratigraphic position Abundance Notes Images
Lepidosauromorpha Indeterminate Berezovsk coal mine Upper Member Several fragments of dentaries and maxillae Basal form similar to Marmoretta
Scincomorpha Indeterminate Berezovsk coal mine Upper Member Fused premaxillae and two dentary fragments additionally several fragmentary maxillae and dentaries Two distinct taxa, one of which is two times smaller than the other.

Choristoderes

Choristoderes of the Itat Formation
Genus Species Location Stratigraphic position Abundance Notes Images
Cteniogenys Indeterminate Berezovsk coal mine Upper Member Skull roof bones, maxillary and dentary fragments, vertebrae, ribs

Pterosaurs

Pterosaurs of the Itat Formation
Genus Species Location Stratigraphic position Abundance Notes Images
?Rhamphorhynchidae Indeterminate Berezovsk coal mine Upper Member Numerous isolated teeth and very rare bone fragments

Crocodyliforms

Crocodyliforms of the Itat Formation
Genus Species Location Stratigraphic position Abundance Notes Images
Goniopholididae[12] Indeterminate Berezovsk coal mine Upper Member Several dozens of isolated teeth, osteoderms, and a few cranial fragments

Dinosaurs

Dinosaurs of the Itat Formation
Genus Species Location Stratigraphic position Abundance Notes Images
Kileskus[13] K. aristotocus Berezovsk coal mine Upper Member Holotype description: "premaxilla, maxilla, a mandible fragment, and several limb bone parts"; referred material includes cervical and caudal vertebrae and numerous isolated teeth, as well as a fibula[14] Proceratosaurid
Heterodontosauridae Indeterminate Berezovsk coal mine Upper Member Isolated maxillary and dentary teeth
Mamenchisauridae[15] Indeterminate Berezovsk coal mine Upper Member Numerous isolated teeth and two platycoelous posterior caudal vertebrae Sauropod
Stegosauria[16] Indeterminate Berezovsk coal mine Upper Member Fragmentary skeletons of at least two individuals

Mammaliamorphs

Mammaliamorphs of the Itat Formation
Genus Species Location Stratigraphic position Abundance Notes Images
Amphibetulimus[17] A. krasnolutskii Berezovsk coal mine Upper Member Dentary fragments, canine and upper molar[18] Alternately considered an amphitheriid or a cladotherian
Amphitherium Indeterminate Berezovsk coal mine Upper Member Upper and lower molars and an edentulous dentary fragment An amphitheriid
Anthracolestes[19] A. sergeii Berezovsk coal mine Upper Member Isolated teeth and edentulous dentary fragments A dryolestid
Hutegotherium[20] H. yaomingi Berezovsk coal mine Upper Member A docodont
Itatodon[21] I. tatarinovi Berezovsk coal mine Upper Member Either a docodont or a member of the family Shuotheriidae
Maiopatagium M. sibiricum[22] Berezovsk coal mine Upper Member A euharamiyidan
Sharypovoia[22] S. arimasporum, S. magna Berezovsk coal mine Upper Member A euharamiyidan
Simpsonodon[20] S. sibiricus Berezovsk coal mine Upper Member A docodont
"Sineleutherus"[23] "S." issedonicus Berezovsk coal mine Upper Member A haramiyidan, now believed to represent a number of different euharamiyidan taxa.[22]
Stereognathus[24] Indeterminate Berezovsk coal mine Upper Member Upper and lower postcanine teeth A tritylodontid
Tagaria[5] T. antiqua Berezovsk coal mine Upper Member Isolated premolar and two molars A multituberculate
Tashtykia[5] T. primaeva Berezovsk coal mine Upper Member Isolated premolars and incisors A multituberculate
Eutriconodonta[25] Indeterminate Berezovsk coal mine Upper Member One large tooth and several tooth fragments A large tooth similar to those of Gobiconodon
Multituberculata Indeterminate Berezovsk coal mine Upper Member Molariforms

Insects

Numerous insect species are known from the Kubekovo village locality located within the upper member of the formation.[26]

Insects of the Itat Formation
Genus Species Location Stratigraphic position Abundance Notes Images
Epiosmylus Epiosmylus longus Osmylid lacewing
Mesosmylina Mesosmylina sibirica
Kubekius Kubekius multiramosus
Thaumatomerobius Thaumatomerobius mirabilis Saucrosmylid lacewing
Archizelmira Archizelmira jarzembowskii Archizelmirid fly
Protanyderus P. invalidus Tanyderidae fly
Boreomerope B. antiqua Meropeidae scorpionfly
Itaphlebia Itaphlebia completa, Itaphlebia jeniseica, Itaphlebia multa, Itaphlebia reducta Nannochoristid scorpionfly
Eublattula E. curvinervis A cockroach
Mesobittacus M. kubekovensis hangingfly
Eoptychoptera E. maxima, E. modica, E. paramaculata Ptychopteridae fly
Eoptychopterina E. glabra
Proptychopterina Proptychopterina amota, Proptychopterina handlirschi , Proptychopterina yeniseica
Crenoptychoptera Crenoptychoptera antica, Crenoptychoptera defossa
Palaeoperissomma P. collessi Perissommatidae fly
Prohyperoscelis Prohyperoscelis jurassicus Canthyloscelidae fly
Microdiplatys Microdiplatys perfectus Protodiplatyidae earwig
Cicadocoris Cicadocoris admotus, Cicadocoris frater Progonocimicidae bug
Olgamartynovia Olgamartynovia nana
Locustopsis Locustopsis picta Locustopsidae orthopteran
Tinaphis Tinaphis sibirica Szelegiewicziidae aphid
Tarantogus Tarantogus obscurus, Tarantogus opiparus, Tarantogus sibiricus Mesopsychidae scorpionfly
Blattula Blattula aberrans, Blattula sibirica Blattulid cockroach
Kemobius Kemobius lux Archijassid leafhopper
Kisa Kisa fasciata
Kubecola Kubecola guttatus
Necrotaulius Necrotaulius kubekovi Necrotauliidae caddisfly
Orthophlebia Orthophlebia obunca Orthophlebiidae scorpionfly

Flora

Flora of the Itat Formation[1]
Genus Species Location Stratigraphic position Abundance Notes Images
Lycopodites Indeterminate Club moss
Equisetites E. asiaticus, E. cf. lateralis Stem-horsetail
Coniopteris C. hymenophylloides, C. simplex, C. cf. maakiana Fern
Cladophlebis C. denticulata Fern
Gonatosorus G. cf mrassiensis Fern
Todites T. cf. princeps Fern
Lobifolia Indeterminate Fern
Rhizomopteris Indeterminate Fern
Ginkgo Indeterminate, G. ex gr. insolita Genus extant
Podozamites Indeterminate Conifer
Sphenobaiera Indeterminate Ginkgoales
Stenorachis S. cf. scanicus Gymnosperm
Czekanowskia Indeterminate Czekanowskiales

See also

References

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