
Alan H TurnerStony Brook University | Stony Brook · Department of Anatomical Sciences
Alan H Turner
PhD, Columbia University
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Introduction
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Publications
Publications (98)
The femora of diapsids have undergone morphological changes related to shifts in postural and locomotor modes, such as the transition from plesiomorphic amniote and diapsid taxa to the apomorphic conditions related to a more erect posture within Archosauriformes. One remarkable clade of Triassic diapsids is the chameleon-like Drepanosauromorpha. Th...
Among archosaurs, thalattosuchian crocodylomorphs experienced the most extensive adaptations to the marine realm. Despite significant attention, the phylogenetic position of the group remains uncertain. Thalattosuchians are either the sister-group to Crocodyliformes, basal mesoeucrocodylians, or nest among longirostrine neosuchians. The earliest de...
A central challenge for biology is to reveal how different levels of biological variation interact and shape diversity. However, recent experimental studies have indicated that prevailing models of evolution cannot readily explain the link between micro‐ and macroevolution at deep time scales. Here, we suggest that this paradox could be the result...
Secondarily marine tetrapod lineages have independently evolved osmoregulatory adaptations for life in salt water but inferring physiological changes in extinct marine tetrapods is difficult. The Mesozoic crocodylomorph clade Thalattosuchia is unique in having both direct evidence from natural endocasts and several proposed osteological correlates...
Dromaeosaurid theropods represent a rare but important clade of nonavialan dinosaurs. Their close evolutionary relationship to modern birds has placed them at the center of paleonto-logical research for the last several decades. Herein we describe a new species of dromaeosaurid-Kuru kulla, gen. et sp. nov.-based on a partial skeleton from the Late...
Eopneumatosuchus colberti Crompton and Smith, 1980, known from a single partial skull, is an enigmatic crocodylomorph from the Lower Jurassic Kayenta Formation. In spite of its unique morphology, an exceptionally pneumatic braincase, and presence during a critical time period of crocodylomorph evolution, relatively little is known about this taxon....
Thalattosuchians represent one of the several independent transitions into the marine realm among crocodylomorphs. The extent of their aquatic adaptations ranges from the semiaquatic teleosauroids, superficially resembling extant gharials, to the almost cetacean‐like pelagic metriorhynchids. Understanding the suite of osteological, physiological, a...
Dyrosaurids were highly specialized, largely marine, relatives of living crocodylians, and one of the few archosaur lineages to survive the K-Pg extinction. Dyrosaurids lived during the Cretaceous to the Eocene and represent a unique combination of morphology and ecology not seen in living crocodylians. Little is known about their endocranial anato...
A new dromaeosaurid dinosaur, Shri devi, from the Late Cretaceous deposit of the Barun Goyot Formation at Khulsan, Mongolia, is described here. The Barun Goyot Formation (herein referred to as the Barun Goyot) is stratigraphically intermediate between the overlying Nemegt Formation and the underlying Djadokhta Formation, where much of the dromaeosa...
Pterosaurs were the first vertebrates to evolve powered flight¹ and comprised one of the main evolutionary radiations in terrestrial ecosystems of the Mesozoic era (approximately 252–66 million years ago), but their origin has remained an unresolved enigma in palaeontology since the nineteenth century2–4. These flying reptiles have been hypothesize...
Mesozoic birds display considerable diversity in size, flight adaptations and feather organization1–4, but exhibit relatively conserved patterns of beak shape and development5–7. Although Neornithine (that is, crown group) birds also exhibit constraint on facial development8,9, they have comparatively diverse beak morphologies associated with a ran...
Crocodylians are currently facing evolutionary decline. This is evinced by the rich fossil record of their extinct relatives, crocodylomorphs, which show not only significantly higher levels of biodiversity in the past but also remarkable morphological disparity and higher ecological diversity. In terms of body size, crocodylians are mostly large a...
New and important pennaraptoran specimens continue to be discovered on a regular basis. Yet, with these discoveries the number of viable phylogenetic hypotheses has increased, including ones that challenge the traditional grouping of dromaeosaurids and troodontids within a monophyletic Deinonychosauria. This chapter will cover recent efforts to add...
An unabated surge of new and important discoveries continues to transform knowledge of pen-naraptoran biology and evolution amassed over the last 150+ years. This chapter summarizes progress made thus far in sampling the pennaraptoran fossil record of the Mesozoic and Paleocene and proposes priority areas of attention moving forward. Oviraptorosaur...
An unabated surge of new and important discoveries continues to transform knowledge of pen-naraptoran biology and evolution amassed over the last 150+ years. This chapter summarizes progress made thus far in sampling the pennaraptoran fossil record of the Mesozoic and Paleocene and proposes priority areas of attention moving forward. Oviraptorosaur...
New and important pennaraptoran specimens continue to be discovered on a regular basis. Yet, with these discoveries the number of viable phylogenetic hypotheses has increased, including ones that challenge the traditional grouping of dromaeosaurids and troodontids within a monophy-letic Deinonychosauria. This chapter will cover recent efforts to ad...
Major evolutionary transitions, in which animals develop new body plans and adapt to dramatically new habitats and lifestyles, have punctuated the history of life. The origin of cetaceans from land-living mammals is among the most famous of these events. Much earlier, during the Mesozoic Era, many reptile groups also moved from land to water, but t...
During the Cretaceous and Paleogene periods, the Earth experienced tectonic and climatic changes, which included continental drift following the breakup of the supercontinents Gondwana and Laurasia, the end-Cretaceous mass extinction event, and several climatic events, including the Paleocene–Eocene Thermal Maximum and the Middle Eocene Climatic Op...
The sternum is a functionally important but poorly understood component of the pectoral girdle in both living and extinct dinosaurs. When ossified, the dinosaur sternum consists of paired plates situated just posterior to the clavicles and scapulocoracoid. In Avialae, the sternal plates are fused at the midline to form a single element, aiding in p...
New discoveries at the Arlington Archosaur Site (AAS), a Cenomanian (Late Cretaceous) locality in north‐central Texas, are filling gaps in our knowledge of mid‐Cretaceous Appalachian ecosystems, which remain poorly characterized. The AAS is notable because it preserves a diverse crocodyliform record. As seen in other sites that preserve four or mor...
Late Cretaceous dinosaur assemblages of North America—characterized by gigantic tyrannosaurid predators, and large-bodied herbivorous ceratopsids and hadrosaurids—were highly successful from around 80 million years ago (Ma) until the end of the ‘Age of Dinosaurs’ 66 Ma. However, the origin of these iconic faunas remains poorly understood because of...
Living crocodylians are exceptional ambush predators in near-shore environments. Utilizing a combination of large body size, stealth, and remarkable prey-capture abilities, these apex predators have dominated regions within and around ponds, lakes, rivers, and oceans since the age of the dinosaurs. Cleuren and de Vree (2000), in their contribution...
Crocodyliforms have a rich fossil record, attained global distribution, and filled a wide variety of ecological niches throughout their history. The group has explored a broad range of cranial morphologies through time, particularly in relation to rostral and supratemporal fossa (STF) form. These character complexes are functionally related, with t...
Understanding growth patterns is central to properly interpreting paleobiological signals in tetrapods, but assessing skeletal maturity in some extinct clades may be difficult when growth patterns are poorly constrained by a lack of ontogenetic series. To overcome this difficulty in assessing the maturity of extinct archosaurian reptiles—crocodylia...
Extant crocodylomorphs are semiaquatic ambush predators largely restricted to freshwater or estuarine environments, but the group is ancestrally terrestrial and inhabited a variety of ecosystems in the past. Despite its rich ecological history, little effort has focused on elucidating the historical pattern of ecological transitions in the group. T...
ELife digest
The brains of mammals consist of the same basic structures, but each of these structures varies from one species to the next. A given structure may be larger in one species than another, for example. It may contain different numbers or sizes of cells. It may even have different connections to other brain regions. By comparing individua...
Tree used in the analyses.
phylogenetic ancova procedures for relative cerebellum size, using the regimes as identified by Bayesian reversible-jump estimation of multi-optima OU models (SI1) as groups.
Brain data used in the analyses.
Simões et al. (2016) argued that large matrices are linked to the construction of “problematic” characters, and that those characters negatively affect tree topology. In their re-evaluation of two squamate datasets, however, Simões et al. (2016) simply eliminated what they termed “problematic” characters, rather than recode them. This practice igno...
Estimating divergence times on phylogenies is critical in paleontological and neontological studies. Chronostratigraphically-constrained fossils are the only direct evidence of absolute timing of species divergence. Strict temporal calibration of fossil-only phylogenies provides minimum divergence estimates, and various methods have been proposed t...
The tetrapod forelimb is one of the most versatile structures in vertebrate evolution, having been co-opted for an enormous array of functions. However, the structural relationships between the bones of the forelimb have remained largely unchanged throughout the 375 million year history of Tetrapoda, with a radius and ulna made up of elongate, para...
Rauisuchids are large (2?6 m in length), carnivorous, and quadrupedal pseudosuchian archosaurs closely related to crocodylomorphs. Though geographically widespread, fossils of this clade are relatively rare in Late Triassic assemblages. The middle Norian (?212 Ma) Hayden Quarry of northern New Mexico, USA, in the Petrified Forest Member of the Chin...
Selected measurements for Vivaron haydeni.
Selected measurements in cm unless otherwise specified.
Phylogenetic matrix.
Conducted using PAUP* version 4.0b10.
Phylogenetic analysis results as .tre files.
including the strict consensus, analysis without the ilia of Rauisuchus, analysis without Teratosaurus, and analysis without the referred material of Vivaron.
The lineage leading to modern Crocodylia has undergone dramatic evolutionary changes in morphology, ecology and locomotion over the past 200+ Myr. These functional innovations may be explained in part by morphological changes in the axial skeleton, which is an integral part of the vertebrate locomotor system. Our objective was to estimate changes i...
A new densely sampled palynological record from the vertebrate-bearing upper Chinle Formation at Ghost Ranch in the Chama Basin of northwestern New Mexico provides insights into the biostratigraphy and terrestrial ecosystem changes during the Late Triassic of northwestern Pangaea. Spore-pollen assemblages from the Poleo Sandstone, Petrified Forest,...
The lineage leading to modern Crocodylia has undergone dramatic evolutionary changes in morphology, ecology and locomotion over the past 200+ Myr. These functional innovations may be explained in part by morphological changes in the axial skeleton, which is an integral part of the vertebrate locomotor system. Our objective was to estimate changes i...
Living birds constitute the only vertebrate group whose brain volume relative to body size approaches the uniquely expanded values expressed by mammals. The broad suite of complex behaviors exhibited by crown-group birds, including sociality, vocal learning, parental care, and flying, suggests the origins of their encephalization was likely driven...
Significance
This is, to our knowledge, the first multiproxy study of climate and associated faunal change for an early Mesozoic terrestrial ecosystem containing an extensive vertebrate fossil record, including early dinosaurs. Our detailed and coupled high-resolution records allow us to sensitively examine the interplay between climate change and...
Birds are maniraptoran theropod dinosaurs. The evidence supporting the systematic position of Avialae as a derived clade within Dinosauria is voluminous and derived from multiple independent lines of evidence. In contrast, a paucity of selectively chosen data weakly support, at best, alternative proposals regarding the origin of birds and feathers....
We report on tanystropheids from the Late Triassic (middle Norian) Hayden Quarry of northern New Mexico (Chinle Formation, Hayden Quarry). These elements, consisting of isolated vertebrae and appendicular bones, represent the first unambiguously identified tanystropheid from western North America and likely the latest occurrence of the group, postd...
The crocodyliform Shamosuchus is known from numerous Late Cretaceous localities in southern and eastern Mongolia and fragmentary remains from Uzbekistan. Seven species of Shamosuchus have been named from six localities in Mongolia and three in Uzbekistan. Six species originally described as Paralligator were later referred to Shamosuchus. Only the...
Eusuchian crocodyliforms, which include all living crocodylians, have historically been characterized by two anatomical specializations: a ball-in-socket vertebral joint and an extensive secondary hard palate with a pterygoid-bound internal choana. The Early Cretaceous neosuchian clade Susisuchidae is typically regarded as phylogenetically near Eus...
Microraptorines are a group of predatory dromaeosaurid theropod dinosaurs with aerodynamic capacity. These close relatives of birds are essential for testing hypotheses explaining the origin and early evolution of avian flight. Here we describe a new 'four-winged' microraptorine, Changyuraptor yangi, from the Early Cretaceous Jehol Biota of China....
The extant anuran fauna of Madagascar is exceptionally rich and almost completely endemic. In recent years, many new species have been described and understanding of the history and relationships of this fauna has been greatly advanced by molecular studies, but very little is known of the fossil history of frogs on the island. Beelzebufo ampinga, t...
Tanystropheids are a clade of long-necked archosauromorphs whose remains are largely restricted to marine deposits from the Triassic of Europe and Asia and almost entirely known from two-dimensionally crushed skeletons. Thus far, the occurrences of Tanytrachelos along the East Coast of the United States represent the westernmost confirmed record of...
The extant anuran fauna of Madagascar is extraordinarily speciose and almost
exclusively endemic. In recent years, our understanding of the history and relationships
of this fauna has been greatly advanced by molecular studies, but very little is known of
the fossil history of frogs on the island. Beelzebufo ampinga, the first named preHolocene
fro...
The goniopholidid Eutretauranosuchus delfsi is currently known from two skulls from the Late Jurassic Morrison Formation of Colorado. Here we present a detailed osteology for a third Eutretauranosuchus delfsi specimen (AMNH FARB 570), consisting of a skull and fragmentary postcranium from Bone Cabin Quarry, Wyoming (Morrison Formation). Additional...
The first large (<1 m) diapsids appeared near the Permian-Triassic extinction and a subset of diapsids, the archosauriforms, expanded their body size range soon after in the Early- Middle Triassic. Here, we examine body size at key evolutionary events within Archosauriformes during the Triassic and through the end-Triassic extinction. Using femoral...
The Hațeg Island fauna of the terminal late Cretaceous (ca. 71-65 million years ago) of Romania is one of the most unusual dinosaur assemblages in the global fossil record. It has long been recognized that many herbivorous dinosaurs from the Hațeg fauna were dwarfed, morphologically aberrant, and/or primitive relative to mainland contemporaries, an...
Drepanosauridae is a clade of putatively arboreal diapsids from the Late Triassic of Europe and North America. They are known primarily from crushed, two-dimensional skeletons discovered in Italy and eastern North America, though isolated occurrences are known from the United Kingdom and western United States. Here we report on a new drepanosaurid...
Ossified skeletal elements within the orbit, such as scleral ossicles, palpebrals, supraorbitals and sesamoids, are widespread across Reptilia, including extant members of Crocodylia, Aves, Squamata and Chelonia. Extant crocodylians lack scleral ossicles, but have a unique palpebral that has recently been shown, through developmental studies, to be...
Coelurosauria is the most diverse clade of theropod dinosaurs. Much of this diversity is present in Paraves—the clade of dinosaurs containing dromaeosaurids, troodontids, and avialans. Paraves has over 160 million years of evolutionary history that continues to the present day. The clade represents the most diverse living tetrapod group (there are...
Recent field efforts conducted as part of the Mahajanga Basin Project have resulted in a significantly improved sampling of theropod dinosaurs from the Maevarano Formation. Both avialan and nonavialan taxa have been recovered from MAD 05-42, a locality exhibiting a mixed taphonomic signature that includes a range of preservational styles. Small (<...
Goniopholidids are a group of Laurasian basal neosuchians that were common in the Juras- sic and Early Cretaceous. With long snouts and sprawling gaits, goniopholidids occupied a semiaquatic carnivorous niche currently allocated to crocodylians. Some species of Asian and North America goniopholidids possess a partially-incomplete secondary palate,...
The dromaeosaurid Mahakala omnogovae is known from a unique specimen from the Late Cretaceous deposits of the Djadokhta Formation at Tögrögiin Shiree, Ömnögov Aimag, Mon-golia. The holotype specimen is comprised of a well-preserved but partial skull and a nearly complete postcranial skeleton. Mahakala omnogovae is included in a comprehensive phylog...
A partial postcranial skeleton of a small alvarezsaurid from the Late Cretaceous of the Mongolian eastern Gobi Desert locality of Khugenetslavkant represents the first reported articulated theropod material from that locality. The specimen is recognized as the holotype of a new taxon herein named Albinykus baatar, gen. et sp. nov. Phylogenetic anal...
The bizarre crocodyliform Simosuchus clarki shares several derived cranial characteristics with basal notosuchian taxa. In the original phylogenetic analysis assessing placement of Simosuchus among other crocodyliforms, it was recovered as a basal notosuchian. Additional preparation of the holotype skull and postcranium, and discovery of additional...
Simosuchus clarki is a small, pug-nosed notosuchian crocodyliform from the Late Cretaceous of Madagascar. Originally described on the basis of a single specimen including a remarkably complete and well-preserved skull and lower jaw, S. clarki is now known from five additional specimens that preserve portions of the craniofacial skeleton. Collective...
Early Dinosaur Discovery
Our understanding of the evolution of early dinosaurs is hampered by limited material, especially compared to the many Jurassic and Cretaceous samples. Nesbitt et al. (p. 1530 ) provide a complete view of a Late Triassic theropod based on several nearly complete skeletons from New Mexico. The dinosaur elucidates the likely...
Archaeopteryx is the oldest and most primitive known bird (Avialae). It is believed that the growth and energetic physiology of basalmost birds such as Archaeopteryx were inherited in their entirety from non-avialan dinosaurs. This hypothesis predicts that the long bones in these birds formed using rapidly growing, well-vascularized woven tissue ty...