Papers by Randall L Nydam
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The origin of snakes remains one of the most contentious evolutionary transitions in vertebrate e... more The origin of snakes remains one of the most contentious evolutionary transitions in vertebrate evolution. The discovery of snake fossils with well-formed hind limbs provided new insights into the phylogenetic and ecological origin of snakes. In 2015, a fossil from the Early Cretaceous Crato Formation of Brazil was described as the first known snake with fore- and hind limbs (<i>Tetrapodophis amplectus</i>), and was proposed to be fossorial, to exhibit large gape feeding adaptations (macrostomy) and to possess morphologies suggesting constriction behaviours. First-hand examination of <i>T. amplectus</i>, including its undescribed counterpart, provides new evidence refuting it as a snake. We find: a long rostrum; straight mandible; teeth not hooked zygosphenes/zygantra absent; neural arch and spines present and tall with apical epiphyses; rib heads not tubercular; synapophyses simple; and lymphapophyses absent. Claimed traits not preserved include: braincase/d...
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STL file of the whole body of Megachirella
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STL file of the skull of Megachirella
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Log file and CT scan slices (8-bit tiff format) of the whole body of the holotype of Megachirella... more Log file and CT scan slices (8-bit tiff format) of the whole body of the holotype of Megachirella wachtleri
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Video of the whole skeleton of Megachirella wachtleri
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Collection of movies of the segmented skull and whole skeleton, along with the tomographic slices... more Collection of movies of the segmented skull and whole skeleton, along with the tomographic slices for the skull and whole skeleton of the fossil lizard Megachirella wachtleri.
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New data on the dentition of the scincomorphan lizard
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Journal of Osteopathic Medicine, 2021
Context The thoracic spine is a common area of focus in osteopathic manipulative medicine (OMM) f... more Context The thoracic spine is a common area of focus in osteopathic manipulative medicine (OMM) for a variety of conditions. Thoracic spine somatic dysfunction diagnosis is achieved by palpating for asymmetry at the tips of the transverse processes (TPs). Previous studies reveal that instead of following the rule of threes, the TPs of a given thoracic vertebra generally align with the spinous process (SP) of the vertebra above. Ultrasonography has been widely utilized as a diagnostic tool to monitor musculoskeletal conditions; it does not utilize ionizing radiation, and it has comparable results to gold-standard modalities. In the case of thoracic somatic dysfunction, ultrasound (US) can be utilized to determine the location of each vertebral TP and its relationship with the SP. Previous studies have investigated the correlation between OMM and ultrasonography of the cervical, lumbar, and sacral regions. However, there has been no study yet that has compared osteopathic structural e...
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Science Advances, 2019
New fossils from the legged snake Najash reveal the evolutionary origins of key features of the m... more New fossils from the legged snake Najash reveal the evolutionary origins of key features of the modern snake skull and body.
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The previous oldest known fossil snakes date from B100 million year old sediments (Upper Cretaceo... more The previous oldest known fossil snakes date from B100 million year old sediments (Upper Cretaceous) and are both morphologically and phylogenetically diverse, indicating that snakes underwent a much earlier origin and adaptive radiation. We report here on snake fossils that extend the record backwards in time by an additional B70 million years (Middle Jurassic-Lower Cretaceous). These ancient snakes share features with fossil and modern snakes (for example, recurved teeth with labial and lingual carinae, long toothed suborbital ramus of maxillae) and with lizards (for example, pronounced subdental shelf/gutter). The paleobiogeography of these early snakes is diverse and complex, suggesting that snakes had undergone habitat differentiation and geographic radiation by the mid-Jurassic. Phylogenetic analysis of squamates recovers these early snakes in a basal polytomy with other fossil and modern snakes, where Najash rionegrina is sister to this clade. Ingroup analysis finds them in a...
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The Iron Springs Formation represents a braidplain consisting of sediments shed from the eastward... more The Iron Springs Formation represents a braidplain consisting of sediments shed from the eastward advancing Sevier orogenic belt, and the fauna it contains is the most proximal, relative to the orogenic belt, of those recovered from the Cretaceous of southern Utah. The fauna spans the Cenomanian into Santonian (and possibly the early Campanian). Among the taxa of fishes, the fauna includes four elasmobranch, one rhinobatoid, two neopterygian, two teleost, and one dipnoan. The lissamphibians are quite diverse and include anurans (at least 1 taxon), urodeles (at least 6 taxa), and albanerpetontids (at least 1 taxon). The squamates are of surprising low diversity, represented by only three taxa. Theropod dinosaurs are present including two taxa of dromaeosaurs, two taxa of coelurosaurs, and an unknown taxon. Among ornithiscians, an ankylosaur, an ornithopod, and possibly a ceratopsian are present. Sixteen mammalian taxa including multituberculates, marsupials, a spalacotheriid, and a symmetrodont are present. This is a relatively high diversity fauna from a small sample suggesting that the upland fauna was not greatly different from those recovered from adjacent plateaus (Markagunt, Paunsaugunt, and Kaiparowits) to the east. The diversity represented by this small sample suggests the potential for more extensive research in the Iron Springs Formation.
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Paläontologische Zeitschrift, 2014
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Nature Communications, 2015
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Journal of Vertebrate Paleontology, 2010
Page 1. Journal of Vertebrate Paleontology 30(4):10901099, July 2010 © 2010 by the Society of Ve... more Page 1. Journal of Vertebrate Paleontology 30(4):10901099, July 2010 © 2010 by the Society of Vertebrate Paleontology ARTICLE BORIOTEIIOIDEAN LIZARD SKULLS FROM KLESKUN HILL (WAPITI FORMATION; UPPER ...
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Journal of Vertebrate Paleontology, 2002
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Journal of Vertebrate Paleontology, 2002
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Journal of Paleontology, 2007
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Proceedings of the …, 1996
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Papers by Randall L Nydam