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Scientific Papers

Given the central role of scientific research in MRF, we have created a section for all of the peer reviewed scientific papers produced by MRF staff or papers using MRF material. Many MRF volunteers helped excavate many of the localities that are now being published on. There is a brief summary of each paper. A pdf of the paper can be downloaded by clicking on the reference.

Click on an item to read the full paper.

• A new baenid turtle from the early Paleocene (Torrejonian) of New Mexico and a species-level phylogenetic analysis of Baenidae

  Journal of Paleontology (2016)
  Tyler R. Lyson, Walter G. Joyce, Spencer G. Lucas and Robert M. Sullivan

  Summary
  New cranial and postcranial material of the baenid turtle Neurankylus from the Paleocene Nacimiento Formation (Torrejonian NALMA) of northwestern New Mexico represents a new species, Neurankylus torrejonensis. The material consists of a fragmented but mostly complete skull, a partial carapace and plastron, portions of both humeri, a partial pelvis, a complete right femur, and a distal phalanx.

• Fossorial Origin of the Turtle Shell

  Current Biology (2016)
  Tyler R. Lyson, Bruce S. Rubidge, Torsten M. Scheyer, Kevin de Queiroz, Emma R. Schachner, Roger M.H. Smith, Jennifer Botha-Brink, and G.S. Bever

  Summary
  The origin of the turtle shell is a major evolutionary transition whose initial function was unknown. Lyson et al. present a strongly supported idea that a burrowing ecology and adaptations related to digging favored the initial transformations on the road to the modern turtle shell. Only later was the shell coopted for protection.

  This paper inspired the article "Why Turtles Evolved Shells: It Wasn't for Protection" published in The Atlantic.

  

• New Cranial Material of Gilmoremys Lancensis (Testudines, Trionychidae) from the Hell Creek Formation of Southeastern Montana, U.S.A.

  Journal of Vertebrate Paleontology (2016)
  Walter G. Joyce, Tyler R. Lyson, and Scott Williams

  Summary
  We here describe two large skulls from the Upper Cretaceous (Maastrichtian) Hell Creek Formation of Carter County, Montana, that document the adult morphology of the plastomenid Gilmoremys lancensis.

• The amniote temporal roof and the diapsid origin of the turtle skull

  Zoology (2016)
  G.S. Bevera, Tyler R. Lyson, Daniel J. Field, Bhart-Anjan S. Bhullar

  Summary
  Two taxa, Eunotosaurus africanus and Pap- pochelys rosinae, were recently and independently described as long-anticipated stem turtles whose diapsid skulls would cement the evolutionary link between turtles and other modern reptile lineages. Detailed CT analysis of the stratigraphically older and phylogenetically stemward of the two, Euno- tosaurus, provides empirical insight into changing developmental trajectories that may have produced the anapsid cranial form of modern turtles and sets the stage for more comprehensive studies of early amniote cranial evolution.

• A Review of the Fossil Record of Turtles of the Clade Baenidae

  Bulletin of the Peabody Museum of Natural History (2015)
  Walter G. Joyce and Tyler R. Lyson

  Summary
  The fossil record of the turtle clade Baenidae ranges from the Early Cretaceous (Aptian–Albian) to the Eocene. The group is present throughout North America during the Early Cretaceous, but is restricted to the western portions of the continents in the Late Cretaceous and Paleogene. No credible remains of the clade have been reported outside of North America to date. Baenids were warm-adapted freshwater aquatic turtles that supported high levels of diversity at times through niche partitioning, particularly by adapting to a broad range of dietary preferences ranging from omnivorous to molluscivorous. Current phylogenies place Baenidae near the split of crown-group Testudines. Within Baenidae three more inclusive, named clades are recognized: Baenodda, Palatobaeninae and Eubaeninae. A taxonomic review of the group concludes that of 49 named taxa, 30 are nomina valida, 12 are nomina invalida and 7 are nomina dubia.
  

• Evolutionary origin of the turtle skull

  Nature (2015)
  G. S. Bever, Tyler R. Lyson, Daniel J. Field, and Bhart-Anjan S. Bhullar

  Summary
  Here we use high-resolution com- puted tomography and a novel character/taxon matrix to study the skull of Eunotosaurus africanus, a 260-million-year-old fossil rep- tile from the Karoo Basin of South Africa, whose distinctive post- cranial skeleton shares many unique features with the shelled body plan of turtles.

  Watch the video illustration!

• Calibration uncertainty in molecular dating analyses: there is no substitute for the prior evaluation of time priors

  Proceedings of the Royal Society B (2014)
  Rachel C. M. Warnock, James F. Parham, Walter G. Joyce, Tyler R. Lyson, Philip C. J. Donoghue

  Summary
  Calibration is the rate-determining step in every molecular clock analysis and, hence, considerable effort has been expended in the development of approaches to distinguish good from bad calibrations. These can be categorized into a priori evaluation of the intrinsic fossil evidence, and a posteriori evaluation of congru- ence through cross-validation. We contrasted these competing approaches and explored the impact of different interpretations of the fossil evidence upon Bayesian divergence time estimation.
  

• Origin of the unique ventilatory apparatus of turtles

  Nature Communications (2014)
  Tyler R. Lyson, Emma R. Schachner, Jennifer Botha-Brink, Torsten M. Scheyer, Markus Lambertz, G.S. Bever, Bruce S. Rubidge, Kevin de Queiroz

  Summary
  We show through broadly comparative anatomical and histological analyses that an early member of the turtle stem lineage has several turtle-specific ventilation characters: rigid ribcage, inferred loss of inter- costal muscles and osteological correlates of the primary expiratory muscle. Our results suggest that the ventilation mechanism of turtles evolved through a division of labour between the ribs and muscles of the trunk in which the abdominal muscles took on the primary ventilatory function.
  

• Toward consilience in reptile phylogeny: miRNAs support an archosaur, not lepidosaur, affinity for turtles

  Evolution & Development (2014)
  Daniel J. Field, Jacques A. Gauthier, Benjamin L. King, Davide Pisani, Tyler R. Lyson, and Kevin J. Peterson

  Summary
  Previously, a study using miRNAs (miRNAs) placed turtles inside diapsids, but as sister to lepidosaurs (lizards and Sphenodon) rather than archosaurs. Here, we test this hypothesis with an expanded miRNA presence/absence dataset, and employ more rigorous criteria for miRNA annotation.
  

• Breathing Life Into Dinosaurs: Tackling Challenges of Soft-Tissue Restoration and Nasal Airflow in Extinct Species

  The Anatomical Record (2014)
  Jason M. Bourke, Wm. Ruger Porter, Ryan C. Ridgely, Tyler R. Lyson, Emma R. Schachner, Phil R. Bell, Lawrence M. Witmer

  Summary
  The nasal region plays a key role in sensory, thermal, and respiratory physiology, but exploring its evolution is hampered by a lack of preservation of soft-tissue structures in extinct vertebrates. As a test case, we investi- gated members of the “bony-headed” ornithischian dinosaur clade Pachyce- phalosauridae (particularly Stegoceras validum) because of their small body size (which mitigated allometric concerns) and their tendency to preserve nasal soft tissues within their hypermineralized skulls.
  

• A New Large-Bodied Oviraptorosaurian Theropod Dinosaur from the Latest Cretaceous of Western North America

  PLOS ONE (2014)
  Matthew C. Lamanna, Hans-Dieter Sues, Emma R. Schachner, Tyler R. Lyson

  Summary
  The oviraptorosaurian theropod dinosaur clade Caenagnathidae has long been enigmatic due to the incomplete nature of nearly all described fossils. Here we describe Anzu wyliei gen. et sp. nov., a new taxon of large-bodied caenagnathid based primarily on three well-preserved partial skeletons. The specimens were recovered from the uppermost Cretaceous (upper Maastrichtian) Hell Creek Formation of North and South Dakota, and are therefore among the stratigraphically youngest known oviraptorosaurian remains. Read more at: Washington Post, Pittsburgh Post-Gazette, and Slate.
  

• A snapshot into the terrestrial ecosystem of an exceptionally well- preserved dinosaur (Hadrosauridae) from the Upper Cretaceous of North Dakota, USA

  Cretaceous Research (2013)
  Vivi Vajda, Tyler R. Lyson, Antoine Bercovici, Jessamy H. Doman, Dean A. Pearson

  Summary
  A palynological investigation of sedimentary rocks enclosing an exceptionally well-preserved fossil dinosaur (Hadrosauridae) discovered in the upper part of the Hell Creek Formation in south western North Dakota was conducted in order to document the immediate paleoenvironment of this dinosaur. The specimen, an Edmontosaurus annectens is remarkable in having exceptional three-dimensional preservation of soft tissue around the skeleton, indicating rapid burial....

• Homology of the enigmatic nuchal bone reveals novel reorganization of the shoulder girdle in the evolution of the turtle shell

  Evolution & Development (2013)
  Tyler R. Lyson, Bhart‐Anjan S. Bhullar, Gabe S. Bever, Walter G. Joyce, Kevin de Queiroz, Arhat Abzhanov, and Jacques A. Gauthier

  Summary
  Evolution of the shoulder girdle based on developmental and morphological (fossil and extant) data.

  Animation by Stroma Studios: Evolution of the Turtle Shoulder Girdle

  The animation is based on the work of Dr. Tyler Lyson, currently at the Smithsonian Institution. The animation shows how the bone at the front and center of the turtle shell is derived from paired shoulder girdle bones (cleithra, blue). In addition, three of the bones found in the plastron (belly shell) are also derived from shoulder girdle bones (clavicles, pink; and interclavicle, green). The animation takes you through known fossil taxa that help bridge the morphological gap separating the highly modified shoulder girdle found in turtles from the more generalized shoulder girdle.

  Article published in Evolution & Development

• Evolutionary Origin of the Turtle Shell

  Current Biology (2013)
  Tyler R. Lyson, Gabe S. Bever, Torsten M. Scheyer, Allison Y. Hsiang, and Jacques A. Gauthier

  Summary
  Animations by Stroma Studios: Evolution of the Turtle Shell and same, illustrated

  Evolution of the turtle shell based on developmental and fossil data. This animation is based on the work of Dr. Tyler Lyson, currently at the Smithsonian Institution. The animation shows how various fossils, particularly Eunotosaurus and Odontochelys, bridge the morphological gap between a generalized animal body plan to the highly modified body plan found in living turtles.

  News reports about this in Smithsonian Science, British Broadcasting Corporation, and Elsevier Connect.

  Published in Current Biology.

• The hooked element in the pes of turtles (Testudines): a global approach to exploring primary and secondary homology

  Journal of Anatomy (2013)
  Walter G. Joyce, Ingmar Werneburg, and Tyler R. Lyson

  Summary
  The hooked element in the pes of turtles was historically identified by most palaeontologists and embryologists as a modified fifth metatarsal, and often used as evidence to unite turtles with other reptiles with a hooked element. Some recent embryological studies, however, revealed that this element might represent an enlarged fifth distal tarsal. We herein provide extensive new myological and developmental observations on the hooked element of turtles, and re-evaluate its primary and secondary homology using all available lines of evidence....

• The girdles of the oldest fossil turtle, Proterochersis robusta, and the age of the turtle crown

  BMC Evolutionary Biology (2013)
  Walter G Joyce, Rainer R Schoch, and Tyler R Lyson

  Summary
  Proterochersis robusta from the Late Triassic (Middle Norian) of Germany is the oldest known fossil turtle (i.e. amniote with a fully formed turtle shell), but little is known about its anatomy. A newly prepared, historic specimen provides novel insights into the morphology of the girdles and vertebral column of this taxon and the opportunity to reassess its phylogenetic position.

• A Divergence Dating Analysis of Turtles Using Fossil Calibrations: An Example of Best Practices

  Journal of Paleontology (2013)
  Walter G. Joyce, James F. Parham, Tyler R. Lyson, Rachel C. M. Warnock, and Philip C. J. Donoghue

  Summary
  Turtles have served as a model system for molecular divergence dating studies using fossil calibrations. However, because some parts of the fossil record of turtles are very well known, divergence age estimates from molecular phylogenies often do not differ greatly from those observed directly from the fossil record alone. Also, the phylogenetic position and age of turtle fossil calibrations used in previous studies have not been adequately justified. We provide the first explicitly justified minimum and soft maximum age constraints on 22 clades of turtles following best practice protocols....

• Evolution of the turtle bauplan: the topological relationship of the scapula relative to the ribcage

  Biology Letters (2012)
  Tyler R. Lyson and Walter G. Joyce

  Summary
  The turtle shell and the relationship of the shoulder girdle inside or ‘deep’ to the ribcage have puzzled neontologists and developmental biologists for more than a century. Recent devel- opmental and fossil data indicate that the shoulder girdle indeed lies inside the shell, but anterior to the ribcage. Developmental biologists compare this orientation to that found in the model organisms mice and chickens, whose scapula lies laterally on top of the ribcage....

• A New Box Turtle from the Miocene/Pliocene Boundary (Latest Hemphillian) of Oklahoma and A Refined Chronology of Box Turtle Diversification

  Journal of Paleontology (2012)
  Walter G. Joyce, Andrea Petričević, Tyler R. Lyson and Nicholas J. Czaplewski

• Boremys (Testudines, Baenidae) from the latest Cretaceous and early Paleocene of North Dakota: an 11-million-year range extension and an additional K/T survivor

  Journal of Vertebrate Paleontology (2011)
  Tyler R. Lyson, Walter G. Joyce, Georgia E. Knauss and Dean A. Pearson

  Summary
  

• Cranial Anatomy and Phylogenetic Placement of the Enigmatic Turtle Compsemys victa Leidy, 1856

  Journal of Paleontology (2011)
  Tyler R. Lyson and Walter G. Joyce

• Dinosaur extinction: closing the ‘3 m gap’

  Biology Letters (2011)
  Tyler R. Lyson, Antoine Bercovici, Stephen G. B. Chester, Eric J. Sargis, Dean Pearson and Walter G. Joyce

• MicroRNAs support a turtle + lizard clade

  Biology Letters (2011)
  Tyler R. Lyson, Erik A. Sperling, Alysha M. Heimberg, Jacques A. Gauthier, Benjamin L. King and Kevin J. Peterson

• A new baenid turtle from the upper Cretaceous (Maastrichtian) Hell Creek Formation of North Dakota and a preliminary taxonomic review of Cretaceous baenidae

  Journal of Vertebrate Paleontology (2010)
  Tyler R. Lyson and Walter G. Joyce

  Summary
  A fragmentary skull from the Hell Creek Formation (Maastrichtian) of southwestern North Dakota represents a new taxon of baenid turtle named herein Gamerabaena sonsalla. The length of the frontals, jugal contribution to the labial ridge, and convex contact between the vomer and the pterygoids indicate its affinities with the clade Palatobaena, but the new taxon clearly lacks the great posterior expansion of the triturating surface, complete absence of a lingual ridge, subrectangular skull, and wide angle between the maxillae that diagnose Palatobaena spp.

• A new kinosternoid from the Late Cretaceous Hell Creek Formation of North Dakota and Montana and the origin of the Dermatemys mawii lineage

  Paläontologische Zeitschrift (2010)
  Georgia E. Knauss, Walter G. Joyce, Tyler R. Lyson and Dean Pearson

  Summary
  A nearly complete turtle shell from the Late Cretaceous (Maastrichtian) Hell Creek Formation of Slope County, North Dakota, represents the most complete remains to date of a Mesozoic kinosternoid turtle and a new species, Hoplochelys clark nov. sp. The new taxon is diagnosable from other representatives of Hoplochelys by the plesiomorphic placement of the humeral/femoral sulcus behind the hyo/hypoplastral suture and the autapomorphic development of an interrupted median (neural) keel.

• A neglected lineage of North American turtle fills a major gap in the fossil record

  Palaeontology (2010)
  Walter G. Joyce and Tyler R. Lyson

  Summary
  The fossil record of the two primary subclades of softshell turtles (Trionychidae) is exceedingly asymmetric, as a result of a ghost range of total clade Cyclanorbinae that is estimated at 80 Ma. Herein, we present the first phylogenetic analysis of Trionychidae that includes a representative of the poorly studied taxon Plastomenidae, which is known from the Campanian to Eocene of North America.

• Spatial niche partitioning in dinosaurs from the latest Cretaceous (Maastrichtian) of North America

  Proceedings of the Royal Society (2010)
  Tyler R. Lyson and Nicholas R. Longrich

  Summary
  We examine patterns of occurrence of associated dinosaur specimens (n = 343) from the North American Upper Cretaceous Hell Creek Formation and equivalent beds, by comparing their relative abundance in sandstone and mudstone.

• Transitional fossils and the origin of turtles

  Biology Letters (2010)
  Tyler R. Lyson, Gabe S. Bever, Bhart-Anjan S. Bhullar, Walter G. Joyce and Jacques A. Gauthier

  Summary
  The origin of turtles is one of the most conten- tious issues in systematics with three currently viable hypotheses: turtles as the extant sister to (i) the crocodile–bird clade, (ii) the lizard– tuatara clade, or (iii) Diapsida (a clade composed of (i) and (ii)). We reanalysed a recent dataset that allied turtles with the lizard–tuatara clade and found that the inclusion of the stem turtle Proganochelys quenstedti and the 'parareptile' Eunotosaurus africanus results in a single over-riding morphological signal, with turtles outside Diapsida. This result reflects the importance of transitional fossils when long branches separate crown clades, and highlights unexplored issues such as the role of topological congruence when using fossils to calibrate molecular clocks.

• Pangshura tatrotia, a new species of pond turtle (Testudinoidea) from the Pliocene Siwaliks of Pakistan

  Journal of Systematic Palaeontology (2010)
  Walter G. Joyce and Tyler R. Lyson

  Summary
  We describe a new species of fossil testudinoid from the Indian subcontinent, Pangshura tatrotia sp. nov., and suggest a new clade name, Palatochelydia, for the monophyletic assemblage of South Asian turtles to which it belongs. A combined analysis using recent molecular data and an updated morphological dataset confidently places P.tatrotia as sister to the extant turtle P. tecta. The holotype specimen is unique relative to most previously described palatochelydian material in that it is associated with good quality locality information.

• Two New Plastomenine Softshell Turtles from the Paleocene of Montana and Wyoming

  Bulletin of the Peabody Museum of Natural History (2009)
  Walter G. Joyce, Ariel Revan, Tyler R. Lyson, and Igor G. Danilov

  Summary
  Two new species of soft-shelled (Trionychidae) turtles are described and their paleoecology discussed. The subgroup of trionychids described, Plastomenidae, are unusual in that they have a well-ossified bottom shell (plastron). The group is thought to be part of the lineage that gave rise to modern day flap shelled turtles (Cyclanorbinae).

• Virtual Palaeontology: Gait Reconstruction of Extinct Vertebrates Using High Performance Computing

  Palaeontologia Electronica (2009)
  William I. Sellers, Phillip L. Manning, Tyler R. Lyson, Kent Stevens, and Lee Margetts

  Summary
  Were hadrosaur dinosaurs running on two or four legs at top speed? This paper uses computer simulations to try and address this question. An 8000 core computer was used to produce mechanically and physiologically plausible gaits and trackway patterns for an Edmontosaur annectens dinosaur. Galloping was determined to be the most plausible and fastest (16 ms-1) gait, followed by bipedal running (14ms-1).

  Watch the Edmontosaur gallop (mov, 11MB), run (mov, 10.5MB), and even hop (mov, 8MB)!

• Mineralized soft-tissue structure and chemistry in a mummified hadrosaur from Hell Creek Formation, North Dakota

  Proceedings of The Royal Society B (2009)
  Phillip L. Manning, Peter M. Morris, Adam McMahon, Emrys Jones, Andy Gize, Joe H. S. Macquaker, George Wolff, Anu Thompson, Jim Marshall, Kevin G. Taylor, Tyler Lyson, Simon Gaskell, Onrapak Reamtong, William I. Sellers, Bart E. van Dongen, Mike Buckley and Roy A. Wogelius

  Summary
  This is the first of a series of papers on the mummified dinosaur "Dakota." This paper was selected by Discover Magazine as one of the top 100 best scientific papers of 2009 (ranking 46). The paper goes through a number of geochemical analyses in search of original biomolecules from "Dakota." In addition, the paper discusses how "Dakota" was preserved and describes the 3-D preservation of the skin.

• Evolution of the Respiratory System in Nonavian Theropods: Evidence from Rib and Vertebral Morphology

  The Anatomical Record (2009)
  Emma R. Schachner, Tyler R. Lyson, and Peter Dodson

  Summary
  This study analyzes rib and vertebral anatomy of carnivorous dinosaurs in order to help determine the type of respiratory system present in carnivorous dinosaurs. Did carnivorous dinosaurs have a flow-through ventilation system as in birds? Or did they have a more crocodilian-like hepatic-piston respiratory system? The study shows that a crocodilian-like hepatic-piston lung would be functionally and biomechanically untenable and that carnivorous dinosaurs share respiratory anatomical characters with birds (i.e. air sacs) and likely had a more bird-like respiratory system.

• A New Species of Palatobaena (Testudines: Baenidae) and a Maximum Parsimony and Bayesian Phylogenetic Analysis of Baenidae

  Journal of Paleontology (2009)
  Tyler R. Lyson and Walter G. Joyce

  Summary
  This is the first of a series of papers on Marmarth Research Foundation's Turtle Graveyard and Turtle Ridge localities. These localities are the world's most diverse and largest fossil turtle quarries. They have produced a number of new species, including the one described in this paper: Palatobaena cohen. This enigmatic turtle was named after MRF board of director and longtime volunteer Steven Cohen. The paper discusses the geology of the Turtle Graveyard locality, a detailed description of the skull and shell, and a phylogenetic analysis of the group of turtle to which Pa. cohen belongs, Baenidae. Hundreds of MRF volunteers have helped excavate this locality and found the material described in this paper including John Akerly (shell), Pam Hollocher (shell), Lou Tremblay (skull and lower jaw), and Norman Gardiner (skull).

• A Revision of Plesiobaena (Testudines: Baenidae) and an Assessment of Baenid Ecology Across the K/T Boundary

  Journal of Paleontology (2009)
  Tyler R. Lyson and Walter G. Joyce

  Summary
  A new species of baenid turtle is described from the Hell Creek Formation. Material of this new species, Peckemys brinkman, was found at MRF's Turtle Graveyard locality. This locality is unusual in that it represents a true snapshot in time (i.e. it is constrained both temporally and spatially). The locality is the most diverse fossil turtle assemblage. Much of the material described in this paper was found by MRF volunteers. The paper discusses the diversity of turtles found at this locality as well as the number of baenid turtles that go extinct at the K/T boundary. Baenid turtles do surprisingly well across the boundary, with seven of nine baenids surviving into the Paleocene. Interestingly, four of the seven survivors are interpreted as having a mollusk and snail type diet.

• Turtles all the way down: loggerheads at the root of the chelonian tree

  Evolution and Development (2009)
  Tyler Lyson and Scott F. Gilbert

  Summary
  This paper discusses the amazing turtle with teeth and half a shell from China, Odontochelys semitestacea. This amazing turtle surprised the scientific community and reopened up several important questions regarding the origin of turtles, the origin of the turtle shell, and their original paleoecology (aquatic or terrestrial).