Hans-Dieter Sues

Smithsonian Institution · Department of Paleobiology

Captorhinikos ’ chozaensis Olson, 1954 is a captorhinid eureptile with multiple tooth rows from the lower Permian (Cisuralian: Kungurian) Clear Fork Group of north-central Texas and the Hennessey Formation of Oklahoma. It has five maxillary and four dentary tooth rows. We re-examined the available specimens referred to ‘ Captorhinikos ’ chozaensis...

The Arnstadt Formation of Saxony-Anhalt, Germany has yielded some of Germany’s most substantial finds of Late Triassic tetrapods, including the sauropodomorph Plateosaurus and the stem-turtle Proganochelys quenstedti. Here, we describe an almost complete skull of a new sphenodontian taxon from this formation (Norian, 227–208 Ma), making it the olde...

Bernhard Peyer (1885–1963) was a prominent Swiss vertebrate palaeontologist and anatomist at the University of Zurich. In 1919, he discovered the occurrence of Middle Triassic (Anisian–Ladinian) ichthyosaurs, sauropterygians, and other reptiles at Monte San Giorgio on the border between Switzerland and Italy. Starting in 1924, Peyer, and later his...

Skeletal remains of a small lepidosaurian reptile from the Middle Triassic (Ladinian: Longobardian) Erfurt Formation, exposed in a commercial limestone quarry near Vellberg (Germany), represent the oldest rhynchocephalian known to date. The new taxon, Wirtembergia hauboldae , is diagnosed by the following combination of features: Premaxilla with fo...

The principles of ecosystem and community assembly developed by modern ecologists should be, in principle, applicable to the evolutionary assembly of terrestrial ecosystems during the Paleozoic. There are three broad, general, not time-specific Assembly Rules that have been described by ecologists: dispersal constraints (i.e., can a species reach a...

Taylorsville Basin new site new finds

Vertebrate assemblages from the Junggar Basin in Xinjiang, China are the only ones known from palaeoarctic continental strata of Late Triassic and Early Jurassic age. Here we present a preliminary description of these new assemblages, focusing on the underappreciated Arctic palaeolatitude and winter freezing of this coal-bearing sequence. Mostly co...

Herbivory evolved independently in several tetrapod lineages during the Late Carboniferous and became more widespread throughout the Permian Period, eventually leading to the basic structure of modern terrestrial ecosystems. Here we report a new taxon of edaphosaurid synapsid based on two fossils recovered from the Moscovian-age cannel coal of Lint...

We report the first trilophosaurid stem-archosaur from Central Europe, Rutiotomodon tytthos gen. et sp. nov., from the Middle Triassic (Ladinian) Erfurt Formation of Baden-Württemberg (Germany). It is currently known from two jaw fragments with distinctive teeth. The labiolingually wide but mesiodistally narrow maxillary and dentary teeth each have...

The Upper Cretaceous (Turonian) Bissekty Formation of Uzbekistan has yielded many isolated bones and teeth representing a variety of non-avian theropod dinosaurs. A pedal phalanx II-2 indicates the presence of a dromaeosaurid theropod that attained a larger body size than any previously known member of that clade. The same formation also yielded a...

The fossil record of Late Cretaceous non-hadrosaurid neornithischians from the Western Interior of North America is sparse. Parksosaurus warreni is an early Maastrichtian taxon currently known only from a skull and much of the associated postcranial skeleton and a referred isolated tooth from the Horseshoe Canyon Formation of Alberta, Canada. This...

The group of Permo-Carboniferous tetrapods known as Recumbirostra have recently been hypothesized to represent the earliest radiation of fossorial reptiles. Therefore, understanding the anatomy and diversity of this clade is essential to understanding the origin and early evolution of amniotes. Here, we redescribe the diminutive ‘microsaur’ Odonter...

Abundant lake ice-rafted debris in Late Triassic and earliest Jurassic strata of the Junggar Basin of northwestern China (paleolatitude ~71°N) indicates that freezing winter temperatures typified the forested Arctic, despite a persistence of extremely high levels of atmospheric P co 2 (partial pressure of CO 2 ). Phylogenetic bracket analysis shows...

The diversity of mid-Cretaceous tyrannosauroids is poorly understood. We describe a partial tyrannosauroid femur from the Albian–Cenomanian Wayan Formation of eastern Idaho that helps to fill in an important spatiotemporal gap in the North American record of tyrannosaurs. This specimen, consisting of the proximal half of the bone, is morphologicall...

Most Triassic terrestrial diapsids belong to two clades, Lepidosauromorpha or (the more diverse) Archosauromorpha. Nevertheless, the phylogenetic relationships of some Triassic diapsids have remained uncertain for decades because of the lack of preservation of phylogenetically relevant anatomical regions or because of unusual combinations of featur...

Parioxys ferricolus Cope, 1878 is a long-neglected taxon of dissorophid temnospondyls from the early Permian (Cisuralian) of Texas. Reexamination of the original material and preparation of a previously undescribed specimen shed some light on the ontogeny and reveal numerous eucacopine features. P. ferricolus is characterized by: (1) a preorbital r...

A new alvarezsaurid theropod, Dzharaonyx eski, gen. et sp. nov., is documented by a variety of dissociated but well-preserved postcranial bones from the Upper Cretaceous (Turonian) Bissekty Formation at Dzharakuduk, Uzbekistan. It has opisthocoelous posterior dorsal vertebrae lacking infrapostzygapophyseal fossae. The posterior caudal vertebrae are...

Triassic strata of the Economy Member of the Wolfville Formation (Newark Supergroup) exposed along the shorelines in Colchester County, Nova Scotia, have yielded an assemblage of continental tetrapods that is clearly different from other Triassic tetrapod communities in eastern North America, including the Late Triassic (Carnian) one from the overl...

We provide a detailed description of the poorly known reptile Eifelosaurus triadicus Jaekel, 1904 from the Upper Buntsandstein (Triassic: early Anisian) of Oberbettingen in the southwestern Eifel region of Rhineland-Palatinate, Germany. The holotype and only known specimen is a partial postcranial skeleton exposed in ventral view. Since its origina...

The Middle Triassic was an important time in the evolutionary history of reptiles because it was during this time that many modern groups originated and initially diversified. In this context, the rich fossiliferous deposits of the Ladinian-age Erfurt Formation in southern Germany play an important role in elucidating reptilian diversity during thi...

Present‐day crocodylians exhibit a remarkably akinetic skull with a highly modified braincase. We present a comprehensive description of the neurocranial osteology of extant crocodylians, with notes on the development of individual skeletal elements and a discussion of the terminology used for this project. The quadrate is rigidly fixed by multiple...

Background Weigeltisauridae is a clade of small-bodied diapsids characterized by a horned cranial frill, slender trunk and limbs, and a patagium supported by elongated bony rods. Partial skeletons and fragments are definitively known only from upper Permian (Lopingian) rocks in England, Germany, Madagascar and Russia. Despite these discoveries, the...

We describe a new taxon of lepidosauromorph reptile, Vinitasaura lizae, based on a nearly complete dentary and the posterior portion of a second dentary from the Upper Triassic (upper Carnian) Vinita Formation in east-central Virginia. It offers new insights into the morphological diversification and spatiotemporal distribution of lepidosauromorphs...

Dzharatitanis kingi gen. et sp. nov. is based on an isolated anterior caudal vertebra (USNM 538127) from the Upper Cretaceous (Turonian) Bissekty Formation at Dzharakuduk, Uzbekistan. Phylogenetic analysis places the new taxon within the diplodocoid clade Rebbachisauridae. This is the first rebbachisaurid reported from Asia and one of the youngest...

A new taxon of sphenodontian reptile, Micromenodon pitti new genus new species is described from the Upper Triassic (Carnian) Vinita Formation of the Richmond basin of the Newark Supergroup in Virginia. It is diagnosed by a dorsoventrally deep facial process of the maxilla that extends for almost the entire anteroposterior length of the bone and by...

The Upper Triassic tetrapod fossil record of North America features a pronounced discrepancy between the assemblages of present-day Virginia and North Carolina relative to those of the American Southwest. While both are typified by large-bodied archosaurian reptiles like phytosaurs and aetosaurs, the latter notably lacks substantial representation...

In the phylogenetic system, the Synapsida include Mammalia and all other amniotes more closely related to Mammalia than to Reptilia. The most characteristic feature is the presence of a single large opening behind the orbit on either side of the skull. This opening is small in basal synapsids but increases in size in later, more derived forms inclu...

The early evolution of dinosaurs is documented by abundant postcranial material, but cranial material is much rarer and comparisons of cranial features among early dinosaurs are limited to only a few specimens. Here, we fully detail the osteology of the unusual early-diverging dinosaur Daemonosaurus chauliodus from the latest Triassic Coelophysis Q...

This paper provides a description and analysis of cranial remains of a rhynchosaur from the Upper Triassic Evangeline Member of the Wolfville Formation of Nova Scotia, Canada. This material, primarily comprising jaw elements, represents the first definitive record of Late Triassic rhynchosaurs from eastern North America. All cranial bones can be as...

Skeletal remains of a small reptile with a distinctive dentition from the Lower Keuper (Erfurt Formation; Middle Triassic, Ladinian) of the Schumann quarry near Eschenau, in the municipality of Vellberg in Baden-Württemberg, Germany, represent a new taxon of non-archosaurian archosauriforms, Polymorphodon adorfi. It is diagnosed by various craniode...

We describe in detail three braincases of the ankylosaur Bissektipelta archibaldi from the Late Cretaceous (Turonian) of Uzbekistan with the aid of computed tomography, segmentation, and 3D modeling. Bissektipelta archibaldi is confirmed as a valid taxon and attributed to Ankylosaurinae based on the results of a phylogenetic analysis. The topograph...

Correctly identifying taxa at the root of major clades or the oldest clade-representatives is critical for meaningful interpretations of evolution. A small, partially crushed skull from the Late Triassic (Norian) of Connecticut, USA, originally described as an indeterminate rhynchocephalian saurian, was recently named Colobops noviportensis and rei...

The origin of the unique body plan of turtles has long been one of the most intriguing mysteries in evolutionary morphology. Discoveries of several new stem-turtles, together with insights from recent studies on the development of the shell in extant turtles, have provided crucial new information concerning this subject. It is now possible to devel...

An isolated dorsal osteoderm of a chroniosuchian from a late Permian fissure filling in the lower Zechstein (Z1) of central Germany represents the first Permian-age record of this enigmatic tetrapod clade outside Russia and China. Based on a number of features, the specimen is designated the holotype of a new taxon, Hassiacoscutum munki, and referr...

Unlike any other tetrapod, turtles form their dorsal bony shell (carapace) not from osteoderms, but by contribution of the ribs and vertebrae that expand into the dermis to form plate-like shell components. Although this was known from embryological studies in extant turtles, important steps in this evolutionary sequence have recently been highligh...

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 Cretaceo...

Teeth provide an excellent model system for understanding evolutionary change and how it has led to adaptive diversity across tetrapods. Their durability over geological timescales and their ubiquity in the fossil record make teeth unique and allow direct comparison of dental structure for both extant and extinct species. We can detail diversity of...

Teraterpeton hrynewichorum is an unusual archosauromorph reptile from the Upper Triassic (Carnian) Evangeline Member of the Wolfville Formation in Nova Scotia (Canada). Its long snout has transversely broad, cusped 'molariform' teeth posteriorly and lacks teeth anteriorly. The temporal region of the cranium is 'euryapsid' with large upper and close...

A cynodont from the Early Jurassic reveals unexpectedly large litters in these early mammal relatives, supporting the hypothesis that an increase in brain size was connected to smaller litters during the early evolution of mammals.

In the present paper, we provide a comprehensive revision of the large-sized neosuchians Kansajsuchus and ‘Turanosuchus’ from the Late Cretaceous of Central Asia. Kansajsuchus extensus from the Kansai locality of the Yalovach Formation, Tadzhikistan, is confirmed as a valid taxon. Previously hypothesized goniopholidid affinities of Kansajsuchus are...

Continued excavations during the last decade have yielded large quantities of tetrapod remains from the Middle Triassic (Ladinian) Erfurt Formation (Lower Keuper) in Germany. The temnospondyl dental morphotypes are highly variable but represent low taxonomic diversity. This is in contrast to the reptilian tooth morphotypes, which comprise a minimum...

Although lepidosaurs are by far the most diverse and widespread group of present-day nonavian reptiles, with over 10,000 formally named species, their early diversification is documented only by a handful of incomplete fossils with few diagnostic features. Recent excavations in strata of the Lower Keuper (Middle Triassic: Ladinian) of Baden-Württem...

Procoelous caudal vertebrae, a carpometacarpus with a hypertrophied metacarpal II, and robust proximal and ungual phalanges of manual digit II of a small theropod dinosaur from the Upper Cretaceous (Turonian) Bissekty Formation at Dzharakuduk, Uzbekistan, show unequivocal synapomorphies of the clade Alvarezsauridae and thus are referred to it. The...

Pappochelys extends the fossil record of Triassic stem-turtles back by some 20 million years and provides important new insights into how and in what sequence the key features of turtles arose. It shares various derived features with the early Late Triassic stem-turtle Odontochelys, such as T-shaped ribs, a short trunk, and features of the girdles...

Amniotes have been the most diverse and successful group of land vertebrates. They attained a global distribution and are found everywhere except in the deepest realms of the ocean. Amniotes repeatedly and successfully invaded the seas and took to the air. All amniotes share the possession of the amniotic (cleidoic) egg, which freed them from depen...

Citation for this article: Scheyer, T. M., and H.-D. Sues. 2016. Expanded dorsal ribs in the Late Triassic pseudosuchian reptile Euscolosuchus olseni. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2017.1248768.

Tyrannosaurids — the familiar dinosaur group including Tyrannosaurus, Albertosaurus, Alioramus, and kin-occupied the apex predator role in Asia and North America during the latest Cretaceous. It has long been thought that sophisticated senses and distinctive brain and endocranial morphologies were among the keys to tyrannosaurid success. Little is...

Basal saurian lineages, especially archosauromorphs, diversified widely during the Triassic Period, exploring a remarkable range of different ecological roles (e.g., terrestrial predators, herbivores with complex teeth, aerial gliders). Many of these early lineages differ greatly from one another in the structure of the postcranium. Teraterpeton hr...

Arctosaurus osborni is known only from an incomplete cervical vertebra from the Upper Triassic Heiberg Formation of Cameron Island, Nunavut, Canada. Re-examination of the unique specimen indicates that it represents an archosauromorph reptile, possibly from the clade Allokotosauria. To date, Arctosaurus osborni represents the sole record of Late Tr...

There are 24 known localities for skeletal remains of sauropod dinosaurs in the republics of Central Asia (Kazakhstan, Kyrgyzstan, Tajikistan, and Uzbekistan). Sauropod remains are very rare at all these localities and represented usually only by isolated teeth. Only narrow-crowned teeth are known from the Cretaceous of Central Asia. The oldest rec...

An ornithomimid theropod dinosaur from the Upper Cretaceous (Turonian) Bissekty Formation of Uzbekistan is one of the basal members of Ornithomimidae. Here we present a description of ontogenetic changes in the long-bone histology of this taxon and distinguish four distinct histological stages. Analysis of a growth series of femora demonstrates ear...

The isolated adult teeth of titanosaurian sauropods from the Upper Cretaceous Bissekty Formation at Dzharakuduk, Uzbekistan, differ little in overall structure but show considerable variation in enamel sculpturing and wear patterns. The crown shape of unworn juvenile teeth ranges from lanceolate to conical. Most specimens have enamel texture resemb...

Late Cretaceous vertebrates are known from the Turonian Zhirkindek and Santonian Bostobe formations in the western Kazakhstan region northeast of the Aral Sea. The Zhirkindek vertebrate assemblage resembles that known from the Turonian Bissekty Formation of the Kyzylkum Desert, Uzbekistan, because of the presence of the rhinobatoid ray Myledaphus t...

Skeletal remains of indeterminate therizinosauroid dinosaurs are present in the Cenomanian Khodzhakul Formation and common in the Turonian Bissekty Formation of Uzbekistan. At least two taxa are present in the Bissekty Formation based on different frontal and humerus morphotypes. Phylogenetic analysis based on a dataset with 348 morphological chara...

Significance Tyrannosaurs—the iconic group of dinosaurian carnivores that includes Tyrannosaurus rex —dominated latest Cretaceous ecosystems with their colossal sizes and sophisticated senses. A gap in the mid-Cretaceous fossil record between these giant apex predators and their older, smaller relatives makes it difficult to understand how the char...

The origin of turtles has been a persistent unresolved problem involving unsettled questions in embryology, morphology, and paleontology. New fossil taxa from the early Late Triassic of China (Odontochelys) and the Late Middle Triassic of Germany (Pappochelys) now add to the understanding of (i) the evolutionary origin of the turtle shell, (ii) the...

Dakotaraptor steini is a recently described dromaeosaurid dinosaur from the Upper Cretaceous (Maastrichtian) Hell Creek Formation of South Dakota. Included within the D. steini hypodigm are three elements originally identified as furculae, one of which was made part of the holotype specimen. We show that the elements described as D. steini ‘furcula...

The stratigraphically oldest remains of ornithomimid theropod dinosaurs are known from the Cenomanian Khodzhakul Formation and the Turonian Bissekty Formation of Uzbekistan. The ornithomimid from the Bissekty Formation is documented by more than 800 isolated bones that represent much of the skeleton. It shows at least three unambiguous synapomorphi...

Parts of the hind limbs of what appears to be a single individual of a theropod dinosaur from the Upper Cretaceous (Santonian–?Campanian) Bostobe Formation of the northeastern Aral Sea region, Kazakhstan, are identified as belonging to an indeterminate ornithomimid based on combination of derived and primitive traits including one ornithomimosauria...

In 1834, the salt-mining expert Friedrich von Alberti applied the name “Trias” to a succession of sedimentary rocks in Germany, which (from oldest to youngest) are the Buntsandstein (“colored sandstone”), Muschelkalk (“clam limestone”), and Keuper (derived from a word for the characteristic marls of this unit) (1). The Buntsandstein and Keuper each...

Dakotaraptor steini is a recently described dromaeosaurid dinosaur from the Upper Cretaceous (Maastrichtian) Hell Creek Formation of South Dakota. Included within the D. steini hypodigm are three elements originally identified as furculae: one which is part of the holotype specimen and two referred specimens. We show that the elements described as...

Dakotaraptor steini is a recently described dromaeosaurid dinosaur from the Upper Cretaceous (Maastrichtian) Hell Creek Formation of South Dakota. Included within the D. steini hypodigm are three elements originally identified as furculae: one which is part of the holotype specimen and two referred specimens. We show that the elements described as...

The holotype and only known specimen of the enigmatic small reptile Elachistosuchus huenei Janensch, 1949 from the Upper Triassic (Norian) Arnstadt Formation of Saxony-Anhalt (Germany) is redescribed using μCT scans of the material. This re-examination revealed new information on the morphology of this taxon, including previously unknown parts of t...

The origin and early evolution of turtles have long been major contentious issues in vertebrate zoology. This is due to conflicting character evidence from molecules and morphology and a lack of transitional fossils from the critical time interval. The 220-million-year-old stem-turtle Odontochelys from China12 has a partly formed shell and many tur...