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January 2013 - present
January 2008 - December 2011
January 2007 - December 2011
Publications
Publications (132)
The skull is the skeletal core of a multicomponent, multifunctional system that controls organismal activities. A common set of skeletal modules is known in mammal skulls and is correlated to developmental and functional compartmentalization. However, it is unclear to what extent these modules further organize into, and evolve as, higher-level netw...
Synopsis
Analyses of form–function relationships are widely used to understand links between morphology, ecology, and adaptation across macroevolutionary scales. However, few have investigated functional trade-offs and covariance within and between the skull, limbs, and vertebral column simultaneously. In this study, we investigated the adaptive la...
The mammalian adult dentition is a non-renewable resource. Tooth attrition and disease must be accommodated by individuals using behavioral, physiological, and/or musculoskeletal shifts to minimize impact on masticatory performance. From a biomechanical perspective, the musculoskeletal system becomes less efficient at producing bite force for a giv...
The mammalian order Primates is known for widespread sexual dimorphism in size and phenotype. Despite repeated speculation that primate sexual size dimorphism either facilitates or is in part driven by functional differences in how males and females interact with their environments, few studies have directly assessed the influence of sexual dimorph...
The evolution of organisms can be studied through the lens of developmental systems, as the timing of development of morphological features is an important aspect to consider when studying a phenotype. Such data can be challenging to obtain in fossil amniotes owing to the scarcity of their fossil record. However, the numerous remains of Rancho La B...
Analyses of form-function relationships are widely used to understand links between morphology, ecology, and species fitness across macroevolutionary scales. However, few have investigated functional trade-offs and covariance among functional traits within and between the skull, limbs, and vertebral column simultaneously. In this study, we investig...
Taphonomic deformation, whether it be brittle or plastic, is possibly the most influential process hindering the correct understanding of fossil species morphology. This is especially true if the deformation affects type specimens or applies to or obscures taxonomically diagnostic or functionally significant traits. Target Deformation, a recently d...
The canine of saber‐toothed predators represents one of the most specialized dental structures known. Hypotheses about the function of hypertrophied canines range from display and conspecific interaction, soft food processing, to active prey acquisition. Recent research on the ontogenetic timing of skull traits indicates the adult canine can take y...
The diversity of vertebrate skeletons is often attributed to adaptations to distinct ecological factors such as diet, locomotion, and sensory environment. Although the adaptive evolution of skull, appendicular skeleton, and vertebral column is well studied in vertebrates, comprehensive investigations of all skeletal components simultaneously are ra...
Explorations in the past 20 years in the Plio-Pleistocene Zanda Basin (3,800–4,500 m above sea level) along the northern slopes of the Himalaya Mountains have substantially enriched our understanding of the paleoenvironments of the Tibetan Plateau and associated biologic evolution. Many elements of the mammalian fauna recovered are either new to sc...
The diversity of vertebrate skeletal forms is often attributed to adaptations to distinct ecological factors such as diet, locomotion, and sensory environment. Although the adaptive evolution of cranial, appendicular, and vertebral skeletal systems is well studied in vertebrates, comprehensive investigations of all skeletal components are rarely pe...
The evolutionary shift from a single-element ear, multi-element jaw to a multi-element ear, single-element jaw during the transition to crown mammals marks one of the most dramatic structural transformations in vertebrates. Research on this transformation has focused on mammalian middle-ear evolution, but a mandible comprising only the dentary is e...
The mammalian skull is an informative and versatile study system critical to research efforts across the broad spectrum of molecular, cellular, organismal and evolutionary sciences. The amount of knowledge concerning mammalian skull continues to grow exponentially, fuelled by the advent of new research methods and new material. Computed microtomogr...
Ornithischian dinosaurs were primary consumers in Mesozoic ecosystems, their evolution intricately linked to challenges of a plant-heavy diet. Whether phenotypic similarities among different ornithischian lineages imply a common functional solution to herbivory is unclear. New research suggests that they evolved herbivory via multiple biomechanical...
Form‐function relationships in mammalian feeding systems are active topics of research in evolutionary biology. This is due principally to their fundamental importance for understanding dietary adaptations in extinct taxa and macro‐evolutionary patterns of morphological transformations through changing environments. We hypothesize that three‐dimens...
Cat-like carnivorans are a textbook example of convergent evolution with distinct morphological differences between taxa with short or elongated upper canines, the latest being often interpreted as an adaptation to bite at large angles and subdue large prey. This interpretation of the sabretooth condition is reinforced by a reduced taxonomic sampli...
The evolutionary shift from a single-element ear, multi-element jaw to a multi-element ear, single-element jaw during the transition to crown mammals marks one of the most dramatic structural transformations in vertebrates. Research on this transformation has focused on mammalian middle-ear evolution, but a mandible comprised of only the dentary is...
Machairodontinae, including the famous Smilodon and Homotherium, was an iconic Pleistocene carnivore lineage that occupied a critical ecological palaeo‐niche and is thought to have had a profound impact on ice‐age ecosystem structure. Recent ancient molecular studies on Homotherium suggest a wider distribution than that inferred from the fossil rec...
The charismatic sabretooth cat Amphimachairodus has numerous but largely fragmentary records across late Miocene deposits of Africa, Eurasia and North America. The genus has a complex taxonomic history, and the majority of Amphimachairodus materials come from isolated localities, often studied without stratigraphic context. Here, we analyse the lon...
The aardwolf Proteles cristatus is the only known hyaenid, living or extinct, to exhibit an extremely reduced dentition related to its termite-specializing diet. The fossil record of extant aardwolves extends to 2 to 4 million years ago, but records that inform its evolutionary origins are essentially nonexistent. Such circumstance renders it diffi...
Mammals are the most encephalized vertebrates, with the largest brains relative to body size. Placental mammals have particularly enlarged brains, with expanded neocortices for sensory integration, the origins of which are unclear. We used computed tomography scans of newly discovered Paleocene fossils to show that contrary to the convention that m...
The Tibetan antelope (Pantholops hodgsonii) is an endemic bovid of the Tibetan Plateau, which was, until recently, considered an endangered species. Researchers have long speculated on the evolutionary origin of Pantholops, suggesting a connection to the rare fossil bovid Qurliqnoria. However, the lack of adequate fossil samples has prevented the t...
The Tibetan antelope (Pantholops hodgsonii) is an endemic bovid of the Tibetan Plateau, which was, until recently, considered an endangered species. Researchers have long speculated on the evolutionary origin of Pantholops, suggesting a connection to the rare fossil bovid Qurliqnoria. However, the lack of adequate fossil samples has prevented the t...
We name a rare, hypercarnivorous and durophagous mustelid Sonitictis moralesi, new genus and species, in honour of Jorge Morales for his contributions to carnivore palaeontology. Sonitictis moralesi is from the middle Miocene Tunggur Formation of Inner Mongolia, China (Tunggurian Land Mammal age). S. moralesi has a short and robust jaw that deepens...
Background
Bite marks attributed to adult Tyrannosaurus rex have been subject to numerous studies. However, few bite marks attributed to T. rex have been traced to juveniles, leaving considerable gaps in understanding ontogenetic changes in bite mechanics and force, and the paleoecological role of juvenile tyrannosaurs in the late Cretaceous.
Meth...
In the past 15 years, the finite element (FE) method has become a ubiquitous tool in the repertoire of evolutionary biologists. The method is used to estimate and compare biomechanical performance implicated as selective factors in the evolution of morphological structures. A feature common to many comparative studies using 3D FE simulations is sma...
More than 200 years since its initial exploration, Zanda Basin, a high-elevation (3,800–4,500 m above sea), intermountain basin at the foothills of the Himalaya, is the site to some of the earliest fossil discoveries, including the holotype of extinct Tibetan antelope, Qurliqnoria hundesiensis. These fossils also hold the record, in 1823, as the fi...
We document new materials of TungurictisColbert, 1939, a basal hyaenid (hyena family), from the Junggar Basin in northern Xinjiang Uygur Autonomous Region, northwestern China, and recognize a new species, T. peignei, n. sp., from the top of the Suosuoquan Formation through the top of the overlying Halamagai Formation. Associated upper and lower tee...
Finite element analysis has been an increasingly widely applied biomechanical modeling method in many different science and engineering fields over the last decade. In the biological sciences, there are many examples of FEA in areas such as paleontology and functional morphology. Despite this common use, the modeling of trabecular bone remains a ke...
Finite element analysis has been an increasingly widely used tool in many different science and engineering fields over the last decade. In the biological sciences, there are many examples of its use in areas as paleontology and functional morphology. Despite this common use, the modeling of porous structures such as trabecular bone remains a key i...
Finite element analysis has been an increasingly widely used tool in many different science and engineering fields over the last decade. In the biological sciences, there are many examples of its use in areas as paleontology and functional morphology. Despite this common use, the modeling of porous structures such as trabecular bone remains a key i...
The northern region of Beringia is ecologically and biogeographically significant as a corridor for biotic dispersals between the Old and New Worlds. Large mammalian predators from Beringia are exceedingly rare in the fossil record, even though carnivore diversity in the past was much higher than it is in this region at present. Here we report the...
Variations in craniodental morphology have been correlated to feeding adaptations in living organisms and used as proxies for paleodiet reconstruction. Within the mammalian order Carnivora, the Miocene fossil musteloid Leptarctus has been variably interpreted as a carnivore, frugivore, herbivore, omnivore, or insectivore based on morphological comp...
Because overall cranial morphology-biomechanics linkage in carnivorans is significantly influenced by both feeding and non-feeding ecological variables, whole-skull mechanical performance measures may be less sensitive to feeding ecology than regional characteristics within the skull. The temporomandibular joint could be one regional characteristic...
Regressions from uniform branch length configuration analyses.
(XLSX)
Ecological traits compiled from PanTHERIA database.
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Allometry analysis results from uniform branch length configuration analyses.
(XLSX)
Borophagine canids have long been hypothesized to be North American ecological ‘avatars’ of living hyenas in Africa and Asia, but direct fossil evidence of hyena-like bone consumption is hitherto unknown. We report rare coprolites (fossilized feces) of Borophagus parvus from the late Miocene of California and, for the first time, describe unambiguo...
158708 bin=4 Avizo file (plus data folder): Segmentation file for LACM 158708 in Avizo software (ThermoFisher Scientific).
Voxel size has been downgraded to 108 micrometers on a side to reduce file size. Segmentation in Avizo Lite 9.2 by Stuart C. White.
Skull shape convergence is pervasive among vertebrates. Although this is frequently inferred to indicate similar functional underpinnings, neither the specific structure-function linkages nor the selective environments in which the supposed functional adaptations arose are commonly identified and tested. We demonstrate that nonfeeding factors relat...
The recent discovery of a fossil of Enhydritherium terraenovae in upper Miocene fluvial deposits in Juchipila (Mexico), nearly 200 km away from the nearest coast, together with other known occurrences of the same species in Florida and California, made possible to envision an alternative to the Panamanian and Polar routes of migration through fluvi...
At 50 kg in estimated weight, the extinct Siamogale melilutra is larger than all living otters, and ranks among the largest fossil otters. The biomechanical capability of S. melilutra jaws as related to their large size is unknown but crucial to reconstructing the species’ potentially unique ecological niche. Here we compare the mandibular biomecha...
The North American fossil otter Enhydritherium terraenovae is thought to be partially convergent in ecological niche with the living sea otter Enhydra lutris, both having low-crowned crushing teeth and a close association with marine environments. Fossil records of Enhydritherium are found in mostly marginal marine deposits in California and Florid...
A central premise of bioclimatic envelope modeling is the assumption of niche conservatism. Whereas such assumptions are testable in modern populations, it is unclear whether niche conservatism holds over deeper time spans and over very large geographic ranges. Hyaenids occupied a diversity of ecological niches over time and space, and until the en...
The Middle to Late Eocene sediments of Texas have yielded a wealth of fossil material that offers a rare window on a diverse and highly endemic mammalian fauna from that time in the southern part of North America. These faunal data are particularly significant because the narrative of mammalian evolution in the Paleogene of North America has tradit...
Sabertooth cats were extinct carnivorans that have attracted great attention and controversy because of their unique dental morphology representing an entirely extinct mode of feeding specialization. Some of them are lion-sized or tiger-sized carnivorans who are widely interpreted as hunters of larger and more powerful preys than those of their mod...
Mammalian molluscivores feed mainly by shell-crushing or suction-feeding. The extinct marine arctoid, Kolponomos, has been interpreted as an otter-like shell-crusher based on similar dentitions. However, neither the masticatory biomechanics of the shell-crushing adaptation nor the way Kolponomos may have captured hard-shelled prey have been tested....
The Zanda Basin in the western Tibet Autonomous Region, China, produces fossils of Miocene–Pleistocene age. Proximity of the basin to the Himalaya Range makes Zanda an important region for understanding vertebrate evolution and dispersal in and around the Tibetan Plateau. Five field seasons of prospecting in the basin have resulted in a rich collec...
New material of Hipparion (Baryhipparion) tchikoicum from Baogeda Ula in Abag, Inner Mongolia, China is described. The latest Miocene (∼6 Ma) occurrence of the species is an important chronological reference for the stratigraphy of Baogeda Ula. Furthermore, the Baogeda Ula Hipparion connects the distribution of this species in the Yushe Basin and M...
Citation for this article: Tseng, Z. J., and J. H. Geisler. 2016. The first fossil record of borophagine dogs (Mammalia, Carnivora) from South Carolina, U.S.A. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2015.1062022.
The bony labyrinth provides a proxy for the morphology of the inner ear, a primary cognitive organ involved in hearing, body perception in space, and balance in vertebrates. Bony labyrinth shape variations often are attributed to phylogenetic and ecological factors. Here we use three-dimensional (3D) geometric morphometrics to examine the phylogene...
The spread of open grassy habitats and the evolution of long-legged herbivorous mammals with high-crowned cheek teeth have been viewed as an example of coevolution. Previous studies indicate that specialized predatory techniques in carnivores do not correlate with the spread of open habitats in North America. Here we analyse new data on elbow-joint...
Despite the superb fossil record of the saber-toothed cat, Smilodon fatalis, ontogenetic age determination for this and other ancient species remains a challenge. The present study utilizes a new technique, a combination of data from stable oxygen isotope analyses and micro-computed tomography, to establish the eruption rate for the permanent upper...
Morphology serves as a ubiquitous proxy in macroevolutionary studies to identify potential adaptive processes and patterns. Inferences of functional significance of phenotypes or their evolution are overwhelmingly based on data from living taxa. Yet, correspondence between form and function has been tested in only a few model species, and those lin...
Due to its lofty height, the Tibetan Plateau features some of the harshest environments in the world with extreme coldness, low oxygen, high UV radiation, and in places, severe aridity. These harsh environments have served as the main driver of vertebrate evolution during the Cenozoic that produced a low productivity, low diversity, high endemicity...
Performance of the masticatory system directly influences feeding and survival, so adaptive hypotheses often are proposed to explain craniodental evolution via functional morphology changes. However, the prevalence of "many-to-one" association of cranial forms and functions in vertebrates suggests a complex interplay of ecological and evolutionary...
We conducted convergence analyses of finite element models of a mongoose skull.•Results show that higher resolution models did not provide more stable outputs.•Convergence patterns varied by model resolution but also bite position simulated.•We used a jackknife approach to analyze robustness of outputs in sub-datasets.•The best sub-dataset sampled...
The Kunlun Pass Basin, at the foothill of Yuzhu Mountain (6224 m asl and the highest peak of the Kunlun Range), records Plio-Pleistocene fine-grained sediments sandwiched between glacial moraines. We document a new vertebrate fossil assemblage, the Yuzhu Fauna, with 16 mammal and 2 fish species that provide insights into basin chronology as well as...
The 'third pole' of the world is a fitting metaphor for the Himalayan-Tibetan Plateau, in allusion to its vast frozen terrain, rivalling the Arctic and Antarctic, at high altitude but low latitude. Living Tibetan and arctic mammals share adaptations to freezing temperatures such as long and thick winter fur in arctic muskox and Tibetan yak, and for...
The red (Ailurus fulgens) and giant (Ailuropoda melanoleuca) pandas are mammalian carnivores convergently adapted to a bamboo feeding diet. However, whereas Ailurus forages almost entirely on younger leaves, fruits and tender trunks, Ailuropoda relies more on trunks and stems. Such difference in foraging mode is considered a strategy for resource p...
Pantherine felids ('big cats') include the largest living cats, apex predators in their respective ecosystems. They are also the earliest diverging living cat lineage, and thus are important for understanding the evolution of all subsequent felid groups. Although the oldest pantherine fossils occur in Africa, molecular phylogenies point to Asia as...
Recent field work in the late Cenozoic Zanda Basin in southwestern Tibetan Plateau has provided new fossil evidence of vertebrate faunas spanning the late Miocene to Pleistocene, which represents new occurrences hitherto unknown in that region of Asia. In this paper we describe a new species of the cursorial hyaenid Chasmaporthetes, C. gangsriensis...
A mid-Pliocene fauna (4.2-3.1 Ma) was recently uncovered in the Zanda (Zhada) Basin in the southwestern Himalaya, at an elevation of about 4200 m above sea level. These fossil materials provide a unique window for examining the linkage among tectonic, climatic and biotic changes. Here we report the results from isotopic analyses of this fauna and o...
In this article, we investigate convergent evolution toward durophagy in carnivoran skull shape using geometric morphometrics in a sample of living and extinct species. Principal components analysis indicate that, in spite of the different dietary resources consumed by durophages-that is, bone-crackers and bamboo-feeders-both groups of carnivorans...
Morphological convergence is a well documented phenomenon in mammals, and adaptive explanations are commonly employed to infer similar functions for convergent characteristics. I present a study that adopts aspects of theoretical morphology and engineering optimization to test hypotheses about adaptive convergent evolution. Bone-cracking ecomorphol...
Cranium ratio measurements of extant east African carnivorans. For abbreviations see Table S1 legend.
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Cranium ratio measurements of fossil canids. Institutional abbreviations: AMNH, American Museum of Natural History, New York; F:AM, Frick Collection, American Museum of Natural History, New York; HMV, Hezheng Paleozoology Museum, Gansu, China; IVPP, Institute of Vertebrate Paleontology and Paleoanthropology, Beijing, China; LACM, Natural History Mu...
Cranium ratio measurements of fossil hyaenids and percrocutids. For abbreviations see Table S1 legend.
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Finite element model parameters of actual fossil and extant carnivorans analyzed in the study. The number of elements were kept as close to 1,000,000 elements as possible for both actual and theoretical models. Three models had lower counts of elements (P. brunnea, P. cristata, C. lupus), but no correlation of MA or SE values to lower element count...
Cranium ratio measurements of extant North American carnivorans. For abbreviations see Table S1 legend.
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Theoretical models and their parameters. D∶L, skull depth to length ratio; W∶L, skull width to length ratio; elements: number of four-noded tetrahedral finite elements in model; SE, skull strain energy (in Joules); adjSE, strain energy adjusted by model volume; Fout, output bite force (in Newtons); MA, mechanical advantage; S.T., solution time requ...
This chapter describes the Neogene mammalian biostratigraphy and geochronology of the Tibetan Plateau. The interior Tibetan Plateau features a unique assemblage of living land mammals, roughly fifty percent of which are endemic. The Himalaya Range and its lateral extensions form the most impenetrable zoogeographic barrier within a continent, as wel...
Several recent studies have clarified the link between microwear features and diet among living carnivorans, but it is still unclear whether previously interpreted evolutionary trends for dietary specialization, based on examination of enamel microstructure, are consistent with such insights from microwear analysis. This study examined the relation...
Elaine Anderson first established in the early 1970s a close relationship between the late Miocene Chinese Martes palaeosinensis and living North American fisher M. pennanti, based on their shared presence of an external rootlet on the upper carnassial. Such a recognition paved the way for their elevated status as a distinct genus of their own, Pek...
a b s t r a c t The timing history and driving mechanisms of C4 expansion and Tibetan uplift are hotly debated issues. Paleoenvironmental evidence from within the Tibetan Plateau is essential to help resolve these issues. Here we report results of stable C and O isotope analyses of tooth enamel samples from a variety of late Cenozoic mammals, inclu...
The Tibetan Plateau is the youngest and highest plateau on Earth, and its elevation reaches one-third of the height of the troposphere, with profound dynamic and thermal effects on atmospheric circulation and climate. The uplift of the Tibetan Plateau was an important factor of global climate change during the late Cenozoic and strongly influenced...
Fossil species of the family Hyaenidae represent a wide range of ecomorphological diversity not observed in living representatives of this carnivoran group. Among them, the cursorial meat-and-bone specialists are of particular interest not only because they were the most cursorial of the hyaenids, but also because they were the only members of this...
A mid-Pliocene fauna (3.1-4.0 Ma) was recently discovered in the Zanda
Basin in western Himalaya, at an elevation of about 4200 m above sea
level. These fossil materials provide a unique window for examining the
linkage among tectonic, climatic and biotic changes. Here we report the
initial results from isotopic analyses of this fauna and of modern...
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Reconstruction of paleoenvironments in the Tibetan region is important
to understanding the linkage between tectonic force and climate change.
Here we report new isotope data from the Qaidam Basin, China, which is
located on the northeastern Tibetan Plateau, including stable C and O
isotope analyses of a wide variety of late Cenozoic mammalian toot...
Ice Age megafauna have long been known to be associated with global cooling during the Pleistocene, and their adaptations to cold environments, such as large body size, long hair, and snow-sweeping structures, are best exemplified by the woolly mammoths and woolly rhinos. These traits were assumed to have evolved as a response to the ice sheet expa...
The discovery by Birger Bohlin of a series of vertebrate fossil sites in the twin lakes region (Tuosu Nor and Keluke Nor) of eastern Qaidam Basin during the Sino-Swedish Expedition in 1931 and 1932 was a major milestone in vertebrate paleontology for the Tibetan Plateau. Qaidam fossil mammals collected by Bohlin still represent the best collections...
