Bipedal dinosaurs

@article{crossref1899recent,
    title = "Recent Work in Comparative Myology",
    year = "1899",
    journal = "Nature",
    url = "https://doi.org/10.1038/059229a0",
    doi = "10.1038/059229a0",
    number = "1523",
    openalex = "W4242856318",
    pages = "229-229",
    volume = "59"
}

@article{dunlap1960the,
    author = "Dunlap, Donald G.",
    title = "The comparative myology of the pelvic appendage in the salientia",
    year = "1960",
    journal = "Journal of Morphology",
    url = "https://doi.org/10.1002/jmor.1051060102",
    doi = "10.1002/jmor.1051060102",
    number = "1",
    openalex = "W1992458910",
    pages = "1-76",
    volume = "106",
    references = "doi101002jmor1050970203, doi101007bf02117707, doi101007bf02117712, doi101007bf02119515, doi1023071436128, doi105962bhlpart8625, doi105962bhltitle29468, doi105962bhltitle82448, openalexw103505795, openalexw432885516"
}

@article{perle1985comparative1,
    author = "Perle, A",
    title = "Comparative myology of the pelvic-femoral region in bipedal dinosaurs",
    year = "1985",
    journal = "Palaeontological Journal, v. 19, p. 105-109",
    note = "talkorigins\_source = {true}; raw\_reference = {Perle, A., 1985, Comparative myology of the pelvic-femoral region in bipedal dinosaurs: Palaeontological Journal, v. 19, p. 105-109.}"
}

@article{lockley1999some,
    author = "Lockley, Martin G and Matsukawa, Masaki",
    title = "Some observations on trackway evidence for gregarious behavior among small bipedal dinosaurs",
    year = "1999",
    journal = "Palaeogeography, Palaeoclimatology, Palaeoecology",
    url = "https://doi.org/10.1016/s0031-0182(99)00005-x",
    doi = "10.1016/s0031-0182(99)00005-x",
    number = "1-2",
    pages = "25-31",
    volume = "150"
}

Substantial differences in pelvic osteology and soft tissues separate crown group crocodylians (Crocodylia) and birds (Neornithes). A phylogenetic perspective including fossils reveals that these disparities arose in a stepwise pattern along the line to extant birds, with major changes occurring both within and outside Aves. Some character states that preceded the origin of Neornithes are only observable or inferable in extinct taxa. These transitional states are important for recognizing the derived traits of neornithines. Palaeontological and neontological data are vital for reconstructing the sequence of pelvic changes along the line to Neornithes. Soft tissue correlation with osteological structures allows changes in soft tissue anatomy to be traced along a phylogenetic framework, and adds anatomical significance to systematic characters from osteology. Explicitly addressing homologies of bone surfaces reveals many subtleties in pelvic evolution that were previously unrecognized or implicit. I advocate that many anatomical features often treated as independent characters should be interpreted as different character states of the same character. Relatively few pelvic character states are unique to Neornithes. Indeed, many features evolved quite early along the line to Neornithes, blurring the distinction between 'avian' and 'non-avian' anatomy.

@article{doi101006zjls20000254,
    author = "Hutchinson, John R.",
    title = "The evolution of pelvic osteology and soft tissues on the line to extant birds (Neornithes)",
    year = "2001",
    journal = "Zoological Journal of the Linnean Society",
    abstract = "Substantial differences in pelvic osteology and soft tissues separate crown group crocodylians (Crocodylia) and birds (Neornithes). A phylogenetic perspective including fossils reveals that these disparities arose in a stepwise pattern along the line to extant birds, with major changes occurring both within and outside Aves. Some character states that preceded the origin of Neornithes are only observable or inferable in extinct taxa. These transitional states are important for recognizing the derived traits of neornithines. Palaeontological and neontological data are vital for reconstructing the sequence of pelvic changes along the line to Neornithes. Soft tissue correlation with osteological structures allows changes in soft tissue anatomy to be traced along a phylogenetic framework, and adds anatomical significance to systematic characters from osteology. Explicitly addressing homologies of bone surfaces reveals many subtleties in pelvic evolution that were previously unrecognized or implicit. I advocate that many anatomical features often treated as independent characters should be interpreted as different character states of the same character. Relatively few pelvic character states are unique to Neornithes. Indeed, many features evolved quite early along the line to Neornithes, blurring the distinction between 'avian' and 'non-avian' anatomy.",
    url = "https://doi.org/10.1006/zjls.2000.0254",
    doi = "10.1006/zjls.2000.0254",
    openalex = "W3021374638",
    references = "crossref1976allosaurus, doi10108002724634199710011027, doi101111j109583121976tb00244x, doi101111j109600311988tb00514x, doi101111j109600311991tb00045x, doi101139e93179, doi1023072413134, doi10230730135049, doi105860choice392183, openalexw3184837389"
}

In this article, we develop a new reconstruction of the pelvic and hindlimb muscles of the large theropod dinosaur Tyrannosaurus rex. Our new reconstruction relies primarily on direct examination of both extant and fossil turtles, lepidosaurs, and archosaurs. These observations are placed into a phylogenetic context and data from extant taxa are used to constrain inferences concerning the soft-tissue structures in T. rex. Using this extant phylogenetic bracket, we are able to offer well-supported inferences concerning most of the hindlimb musculature in this taxon. We also refrain from making any inferences for certain muscles where the resulting optimizations are ambiguous. This reconstruction differs from several previous attempts and we evaluate these discrepancies. In addition to providing a new and more detailed understanding of the hindlimb morphology of T. rex--the largest known terrestrial biped--this reconstruction also helps to clarify the sequence of character-state change along the line to extant birds.

@article{doi101002jmor10018,
    author = "Carrano, Matthew T. and Hutchinson, John R.",
    title = "Pelvic and hindlimb musculature of Tyrannosaurus rex (Dinosauria: Theropoda)",
    year = "2002",
    journal = "Journal of Morphology",
    abstract = "In this article, we develop a new reconstruction of the pelvic and hindlimb muscles of the large theropod dinosaur Tyrannosaurus rex. Our new reconstruction relies primarily on direct examination of both extant and fossil turtles, lepidosaurs, and archosaurs. These observations are placed into a phylogenetic context and data from extant taxa are used to constrain inferences concerning the soft-tissue structures in T. rex. Using this extant phylogenetic bracket, we are able to offer well-supported inferences concerning most of the hindlimb musculature in this taxon. We also refrain from making any inferences for certain muscles where the resulting optimizations are ambiguous. This reconstruction differs from several previous attempts and we evaluate these discrepancies. In addition to providing a new and more detailed understanding of the hindlimb morphology of T. rex--the largest known terrestrial biped--this reconstruction also helps to clarify the sequence of character-state change along the line to extant birds.",
    url = "https://doi.org/10.1002/jmor.10018",
    doi = "10.1002/jmor.10018",
    openalex = "W2050159958",
    references = "doi101017s0094837300009866, doi101017s247526300000091x, doi10108002724634199710011027, doi101111j109636422001tb01313x, doi101111j109636422001tb01314x, doi101111j1469185x1997tb00024x, doi101139e72031, doi1016660094837320000260734aaateo20co2, doi1023072413454, doi105860choice326223, doi105860choice392183, openalexw1915591379"
}

@article{pontzer2009biomechanics,
    author = "Pontzer, Herman and Allen, Vivian and Hutchinson, John R.",
    title = "Biomechanics of Running Indicates Endothermy in Bipedal Dinosaurs",
    year = "2009",
    journal = "PLoS ONE",
    url = "https://doi.org/10.1371/journal.pone.0007783",
    doi = "10.1371/journal.pone.0007783",
    number = "11",
    openalex = "W2152815529",
    pages = "e7783",
    volume = "4",
    references = "doi101001jama196203050110085031, doi101038346265a0, doi101111j109600311988tb00514x, doi101111j146979981983tb04266x, doi101126science2740914, doi101126science28454232137, doi101126science493968, doi101146annurevnutr191247, doi1023071366368, openalexw2611511275"
}

@article{pontzer2009correction,
    author = "Pontzer, Herman and Allen, Vivian and Hutchinson, John R.",
    title = "Correction: Biomechanics of Running Indicates Endothermy in Bipedal Dinosaurs",
    year = "2009",
    journal = "PLoS ONE",
    url = "https://doi.org/10.1371/annotation/635e46fc-4be3-4f42-ad5c-ee3a276cd24f",
    doi = "10.1371/annotation/635e46fc-4be3-4f42-ad5c-ee3a276cd24f",
    number = "12",
    volume = "4"
}

This study aims to investigate functional disparity in the locomotor apparatus of bipedal archosaurs. We use reconstructions of hindlimb myology of extant and extinct archosaurs to generate musculoskeletal biomechanical models to test hypothesized convergence between bipedal crocodile-line archosaurs and dinosaurs. Quantitative comparison of muscle leverage supports the inference that bipedal crocodile-line archosaurs and non-avian theropods had highly convergent hindlimb myology, suggesting similar muscular mechanics and neuromuscular control of locomotion. While these groups independently evolved similar musculoskeletal solutions to the challenges of parasagittally erect bipedalism, differences also clearly exist, particularly the distinct hip and crurotarsal ankle morphology characteristic of many pseudosuchian archosaurs. Furthermore, comparative analyses of muscle design in extant archosaurs reveal that muscular parameters such as size and architecture are more highly adapted or optimized for habitual locomotion than moment arms. The importance of these aspects of muscle design, which are not directly retrievable from fossils, warns against over-extrapolating the functional significance of anatomical convergences. Nevertheless, links identified between posture, muscle moments and neural control in archosaur locomotion suggest that functional interpretations of osteological changes in limb anatomy traditionally linked to postural evolution in Late Triassic archosaurs could be constrained through musculoskeletal modelling.

@article{doi101098rsif20110687,
    author = "Bates, Karl T. and Schachner, Emma R.",
    title = "Disparity and convergence in bipedal archosaur locomotion",
    year = "2011",
    journal = "Journal of The Royal Society Interface",
    abstract = "This study aims to investigate functional disparity in the locomotor apparatus of bipedal archosaurs. We use reconstructions of hindlimb myology of extant and extinct archosaurs to generate musculoskeletal biomechanical models to test hypothesized convergence between bipedal crocodile-line archosaurs and dinosaurs. Quantitative comparison of muscle leverage supports the inference that bipedal crocodile-line archosaurs and non-avian theropods had highly convergent hindlimb myology, suggesting similar muscular mechanics and neuromuscular control of locomotion. While these groups independently evolved similar musculoskeletal solutions to the challenges of parasagittally erect bipedalism, differences also clearly exist, particularly the distinct hip and crurotarsal ankle morphology characteristic of many pseudosuchian archosaurs. Furthermore, comparative analyses of muscle design in extant archosaurs reveal that muscular parameters such as size and architecture are more highly adapted or optimized for habitual locomotion than moment arms. The importance of these aspects of muscle design, which are not directly retrievable from fossils, warns against over-extrapolating the functional significance of anatomical convergences. Nevertheless, links identified between posture, muscle moments and neural control in archosaur locomotion suggest that functional interpretations of osteological changes in limb anatomy traditionally linked to postural evolution in Late Triassic archosaurs could be constrained through musculoskeletal modelling.",
    url = "https://doi.org/10.1098/rsif.2011.0687",
    doi = "10.1098/rsif.2011.0687",
    openalex = "W2110060322",
    references = "doi101007s0011400804883, doi101666100041"
}

The study of pelvic and hind limb bones and muscles in basal dinosaurs is important for understanding the early evolution of bipedal locomotion in the group. The use of data from both extant and extinct taxa placed into a phylogenetic context allowed to make well-supported inferences concerning most of the hind limb musculature of the basal saurischian Staurikosaurus pricei Colbert, 1970 (Santa Maria Formation, Late Triassic of Rio Grande do Sul, Brazil). Two large concavities in the lateral surface of the ilium represent the origin of the muscles iliotrochantericus caudalis plus iliofemoralis externus (in the anterior concavity) and iliofibularis (in the posterior concavity). Muscle ambiens has only one head and originates from the pubic tubercle. The origin of puboischiofemoralis internus 1 possibly corresponds to a fossa in the ventral margin of the pré-acetabular iliac process. This could represent an intermediate stage prior to the origin of a true pré-acetabular fossa. Muscles caudofemorales longus et brevis were likely well developed, and Staurikosaurus is unique in bearing a posteriorly projected surface for the origin of caudofemoralis brevis.

@article{doi101590s000137652011000100005,
    author = "Grillo, Orlando Nelson and de Azevedo, Sergio Alex Kugland",
    title = "Pelvic and hind limb musculature of Staurikosaurus pricei (Dinosauria: Saurischia)",
    year = "2011",
    journal = "Anais da Academia Brasileira de Ciências",
    abstract = "The study of pelvic and hind limb bones and muscles in basal dinosaurs is important for understanding the early evolution of bipedal locomotion in the group. The use of data from both extant and extinct taxa placed into a phylogenetic context allowed to make well-supported inferences concerning most of the hind limb musculature of the basal saurischian Staurikosaurus pricei Colbert, 1970 (Santa Maria Formation, Late Triassic of Rio Grande do Sul, Brazil). Two large concavities in the lateral surface of the ilium represent the origin of the muscles iliotrochantericus caudalis plus iliofemoralis externus (in the anterior concavity) and iliofibularis (in the posterior concavity). Muscle ambiens has only one head and originates from the pubic tubercle. The origin of puboischiofemoralis internus 1 possibly corresponds to a fossa in the ventral margin of the pré-acetabular iliac process. This could represent an intermediate stage prior to the origin of a true pré-acetabular fossa. Muscles caudofemorales longus et brevis were likely well developed, and Staurikosaurus is unique in bearing a posteriorly projected surface for the origin of caudofemoralis brevis.",
    url = "https://doi.org/10.1590/s0001-37652011000100005",
    doi = "10.1590/s0001-37652011000100005",
    openalex = "W2002109633",
    references = "crossref1976allosaurus, doi101038261129a0, doi10108002724634199710011027, doi101111j146979981991tb04794x, doi101126science28454232137, doi101146annurevearth251435, doi1023071292217, doi105281zenodo16171435, doi105860choice326223, openalexw1535663436"
}

Ornithischia (the ‘bird‐hipped’ dinosaurs) encompasses bipedal, facultative quadrupedal and quadrupedal taxa. Primitive ornithischians were small bipeds, but large body size and obligate quadrupedality evolved independently in all major ornithischian lineages. Numerous pelvic and hind limb features distinguish ornithischians from the majority of other non‐avian dinosaurs. However, some of these features, notably a retroverted pubis and elongate iliac preacetabular process, appeared convergently in maniraptoran theropods, and were inherited by their avian descendants. During maniraptoran/avian evolution these pelvic modifications led to significant changes in the functions of associated muscles, involving alterations to the moment arms and the activation patterns of pelvic musculature. However, the functions of these features in ornithischians and their influence on locomotion have not been tested and remain poorly understood. Here, we provide quantitative tests of bipedal ornithischian muscle function using computational modelling to estimate 3D hind limb moment arms for the most complete basal ornithischian, Lesothosaurus diagnosticus. This approach enables sensitivity analyses to be carried out to explore the effects of uncertainties in muscle reconstructions of extinct taxa, and allows direct comparisons to be made with similarly constructed models of other bipedal dinosaurs. This analysis supports some previously proposed qualitative inferences of muscle function in basal ornithischians. However, more importantly, this work highlights ambiguities in the roles of certain muscles, notably those inserting close to the hip joint. Comparative analysis reveals that moment arm polarities and magnitudes in Lesothosaurus, basal tetanuran theropods and the extant ostrich are generally similar. However, several key differences are identified, most significantly in comparisons between the moment arms of muscles associated with convergent osteological features in ornithischians and birds. Craniad migration of the iliofemoralis group muscles in birds correlates with increased leverage and use of medial femoral rotation to counter stance phase adduction moments at the hip. In Lesothosaurus the iliofemoralis group maintains significantly higher moment arms for abduction, consistent with the hip abduction mode of lateral limb support hypothesized for basal dinosaurs. Sensitivity analysis highlights ambiguity in the role of musculature associated with the retroverted pubis (puboischiofemoralis externus group) in ornithischians. However, it seems likely that this musculature may have predominantly functioned similarly to homologous muscles in extant birds, activating during the swing phase to adduct the lower limb through lateral rotation of the femur. Overall the results suggest that locomotor muscle leverage in Lesothosaurus (and by inference basal ornithischians in general) was more similar to that of other non‐avian dinosaurs than the ostrich, representing what was probably the basal dinosaur condition. This work thereby contradicts previous hypotheses of ornithischian–bird functional convergence.

@article{doi101111j14697580201101469x,
    author = "Bates, K. and Maidment, S. and Allen, V. and Barrett, P.",
    title = "Computational modelling of locomotor muscle moment arms in the basal dinosaur Lesothosaurus diagnosticus: assessing convergence between birds and basal ornithischians",
    year = "2012",
    journal = "Journal of Anatomy",
    abstract = "Ornithischia (the ‘bird‐hipped’ dinosaurs) encompasses bipedal, facultative quadrupedal and quadrupedal taxa. Primitive ornithischians were small bipeds, but large body size and obligate quadrupedality evolved independently in all major ornithischian lineages. Numerous pelvic and hind limb features distinguish ornithischians from the majority of other non‐avian dinosaurs. However, some of these features, notably a retroverted pubis and elongate iliac preacetabular process, appeared convergently in maniraptoran theropods, and were inherited by their avian descendants. During maniraptoran/avian evolution these pelvic modifications led to significant changes in the functions of associated muscles, involving alterations to the moment arms and the activation patterns of pelvic musculature. However, the functions of these features in ornithischians and their influence on locomotion have not been tested and remain poorly understood. Here, we provide quantitative tests of bipedal ornithischian muscle function using computational modelling to estimate 3D hind limb moment arms for the most complete basal ornithischian, Lesothosaurus diagnosticus. This approach enables sensitivity analyses to be carried out to explore the effects of uncertainties in muscle reconstructions of extinct taxa, and allows direct comparisons to be made with similarly constructed models of other bipedal dinosaurs. This analysis supports some previously proposed qualitative inferences of muscle function in basal ornithischians. However, more importantly, this work highlights ambiguities in the roles of certain muscles, notably those inserting close to the hip joint. Comparative analysis reveals that moment arm polarities and magnitudes in Lesothosaurus, basal tetanuran theropods and the extant ostrich are generally similar. However, several key differences are identified, most significantly in comparisons between the moment arms of muscles associated with convergent osteological features in ornithischians and birds. Craniad migration of the iliofemoralis group muscles in birds correlates with increased leverage and use of medial femoral rotation to counter stance phase adduction moments at the hip. In Lesothosaurus the iliofemoralis group maintains significantly higher moment arms for abduction, consistent with the hip abduction mode of lateral limb support hypothesized for basal dinosaurs. Sensitivity analysis highlights ambiguity in the role of musculature associated with the retroverted pubis (puboischiofemoralis externus group) in ornithischians. However, it seems likely that this musculature may have predominantly functioned similarly to homologous muscles in extant birds, activating during the swing phase to adduct the lower limb through lateral rotation of the femur. Overall the results suggest that locomotor muscle leverage in Lesothosaurus (and by inference basal ornithischians in general) was more similar to that of other non‐avian dinosaurs than the ostrich, representing what was probably the basal dinosaur condition. This work thereby contradicts previous hypotheses of ornithischian–bird functional convergence.",
    url = "https://onlinelibrary.wiley.com/doi/pdfdirect/10.1111/j.1469-7580.2011.01469.x",
    doi = "10.1111/j.1469-7580.2011.01469.x",
    is_oa = "true",
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    pages = "212-232",
    semanticscholar_citation_count = "50",
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    volume = "220"
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@incollection{crossref2014comparative,
    title = "Comparative Myology of the Dog",
    year = "2014",
    booktitle = "Canine Rehabilitation and Physical Therapy",
    url = "https://doi.org/10.1016/b978-1-4377-0309-2.00049-1",
    doi = "10.1016/b978-1-4377-0309-2.00049-1",
    openalex = "W4237016532",
    pages = "e1-e18"
}

The ontogeny of early-diverging dinosauromorphs is poorly understood because few ontogenetic series from the same species-level taxon are known and what is available has not been extensively documented. The large numbers of skeletal elements of the silesaurid Asilisaurus kongwe recently recovered from Tanzania provide an opportunity to examine the ontogenetic trajectory of the earliest known member of Ornithodira and one of the closest relatives to Dinosauria. We examined the ontogeny of the femur and the histology of a series of long bone elements. We observed bone scar variation in a series of femora (n = 27) of different lengths (73.8–177.2 mm). We hypothesize that most femora follow a similar developmental trajectory; however, we observed sequence polymorphism in the order of appearance and shape of bone scars, and we quantified this polymorphism using ontogenetic sequence analysis (OSA). Additionally, five femora, three tibiae, a fibula, and a humerus were thin-sectioned to examine osteological tissues. No lines of arrested growth (LAGs) are present in any specimen, and there is little histological information about the ontogenetic stage of femora, although none have slowed or ceased growth. The woven-fibered bone present in the cortex of elements sectioned is similar to that of the earliest dinosaurs. This sequence polymorphism provides an alternate hypothesis for the robust/gracile dichotomy found in early dinosaurs often interpreted as sexual dimorphism. The shared femoral features found in Asilisaurus and early dinosaurs suggest that this ontogenetic pattern is plesiomorphic for Dinosauria, and that size is a poor predictor of maturity in early dinosauriforms.SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVPCitation for this article: Griffin, C. T., and S. J. Nesbitt. 2016. The femoral ontogeny and long bone histology of the Middle Triassic (?late Anisian) dinosauriform Asilisaurus kongwe and implications for the growth of early dinosaurs. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2016.1111224.

@article{doi1010800272463420161111224,
    author = "Griffin, Christopher T. and Nesbitt, Sterling J.",
    title = "The femoral ontogeny and long bone histology of the Middle Triassic (?late Anisian) dinosauriform Asilisaurus kongwe and implications for the growth of early dinosaurs",
    year = "2016",
    journal = "Journal of Vertebrate Paleontology",
    abstract = "The ontogeny of early-diverging dinosauromorphs is poorly understood because few ontogenetic series from the same species-level taxon are known and what is available has not been extensively documented. The large numbers of skeletal elements of the silesaurid Asilisaurus kongwe recently recovered from Tanzania provide an opportunity to examine the ontogenetic trajectory of the earliest known member of Ornithodira and one of the closest relatives to Dinosauria. We examined the ontogeny of the femur and the histology of a series of long bone elements. We observed bone scar variation in a series of femora (n = 27) of different lengths (73.8–177.2 mm). We hypothesize that most femora follow a similar developmental trajectory; however, we observed sequence polymorphism in the order of appearance and shape of bone scars, and we quantified this polymorphism using ontogenetic sequence analysis (OSA). Additionally, five femora, three tibiae, a fibula, and a humerus were thin-sectioned to examine osteological tissues. No lines of arrested growth (LAGs) are present in any specimen, and there is little histological information about the ontogenetic stage of femora, although none have slowed or ceased growth. The woven-fibered bone present in the cortex of elements sectioned is similar to that of the earliest dinosaurs. This sequence polymorphism provides an alternate hypothesis for the robust/gracile dichotomy found in early dinosaurs often interpreted as sexual dimorphism. The shared femoral features found in Asilisaurus and early dinosaurs suggest that this ontogenetic pattern is plesiomorphic for Dinosauria, and that size is a poor predictor of maturity in early dinosauriforms.SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVPCitation for this article: Griffin, C. T., and S. J. Nesbitt. 2016. The femoral ontogeny and long bone histology of the Middle Triassic (?late Anisian) dinosauriform Asilisaurus kongwe and implications for the growth of early dinosaurs. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2016.1111224.",
    url = "https://doi.org/10.1080/02724634.2016.1111224",
    doi = "10.1080/02724634.2016.1111224",
    openalex = "W2291492864",
    references = "doi101002sici109746871996082292121aidjmor130co24, doi101016s0031018298001175, doi101017s247526300000091x, doi10108002724634199610011283, doi101080027246342010483632, doi101111j109636422001tb01314x, doi101111j10963642200600232x, doi101111j10963642200900631x, doi101144sp37916, doi1012063521, doi101371journalpone0007626, doi1016710272463420000200115lbhoth20co2, doi10230730135049, doi105281zenodo16171435, doi10560219780801881206, openalexw1565584485"
}

@article{doi101002ar23574,
    author = "Laitman, J. and Albertine, K.",
    title = "The Anatomical Record Marches on by Exploring Evolution in the Second Part of Our Special Issue on the Human Pelvis",
    year = "2017",
    journal = "The Anatomical Record",
    url = "https://onlinelibrary.wiley.com/doi/pdfdirect/10.1002/ar.23574",
    doi = "10.1002/ar.23574",
    is_oa = "true",
    number = "5",
    pages = "783-785",
    semanticscholar_id = "b2558fd1eb0d0b35a255143c4186b335f69be5a6",
    volume = "300"
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Bipedal ornithischian dinosaurs from the Upper Jurassic Morrison Formation are rare, forming only about 15% of the dinosaur specimens. Nevertheless, one of them was among the first dinosaurs named from what was then the ‘’Atlantosaurus Beds’’ of Colorado. Collecting and restudy for 140 years has in­creased the diversity from the initial 1877 discovery to the currently valid four genera and six species, viz., Fruitadens haagaroum, Nanosaurus agilis, Camptosaurus dispar, C. aphanoecetes, Dryosaurus altus, and D. elderae, which we briefly review. We demonstrate that the enigmatic Nanosaurus agilis is the senior name for Drinker nisti, Othnielosaurus consors, and Othnielia rex. In addition, a new species, Dryosaurus elderae is proposed for the Dryosaurus specimens from Dinosaur National Monument that are characterized by elongate cervical verebrae and a long, low ilium among other features.

@article{carpenter2018a,
    author = "Carpenter, Kenneth and Galton, Peter",
    title = "A photo documentation of bipedal ornithischian dinosaurs from the Upper Jurassic Morrison Formation, USA",
    year = "2018",
    journal = "Geology of the Intermountain West",
    abstract = "Bipedal ornithischian dinosaurs from the Upper Jurassic Morrison Formation are rare, forming only about 15\% of the dinosaur specimens. Nevertheless, one of them was among the first dinosaurs named from what was then the ‘’Atlantosaurus Beds’’ of Colorado. Collecting and restudy for 140 years has in­creased the diversity from the initial 1877 discovery to the currently valid four genera and six species, viz., Fruitadens haagaroum, Nanosaurus agilis, Camptosaurus dispar, C. aphanoecetes, Dryosaurus altus, and D. elderae, which we briefly review. We demonstrate that the enigmatic Nanosaurus agilis is the senior name for Drinker nisti, Othnielosaurus consors, and Othnielia rex. In addition, a new species, Dryosaurus elderae is proposed for the Dryosaurus specimens from Dinosaur National Monument that are characterized by elongate cervical verebrae and a long, low ilium among other features.",
    url = "https://doi.org/10.31711/giw.v5.pp167-207",
    doi = "10.31711/giw.v5.pp167-207",
    pages = "167-207",
    volume = "5"
}

The femoral fourth trochanter is the attachment site of the caudofemoralis musculature, which is the primary hindlimb retractor in most non-avian dinosaurs. Early ornithischian dinosaurs are uniquely characterized by a fourth trochanter with a prominent pendant process. Throughout the evolution of ornithischians, the fourth trochanter repeatedly converged on two major morphological changes: (1) the distal migration of the trochanter down the femoral shaft and (2) the loss of the pendant process. Both changes, as well as the original evolution of the pendant form, relate to a single major functional shift emphasizing caudofemoral leverage. Direct evidence of muscle scarring across the surface of the pendant process affirms that it served to extend the attachment of the primary caudofemoralis brevis tendon distally. A proximally located fourth trochanter is the basal condition in dinosaurs and other archosaurs, and the development of a pendant process lengthened the functional lever arm with regard to the insertion of the caudofemoralis. This adaptation afforded improved mechanical advantage, perhaps beneficial in the context of the newly assumed herbivorous diets of basal ornithischians. As some derived ornithischians increased in body size, a high-leverage system with a more distal caudofemoralis attachment evolved. In some groups, the fourth trochanter as a whole descended down the femur, eventually reaching a point where the pendant process was unnecessary. Sauropodomorphs, the other great lineage of dinosaur herbivores, converged on the same high-leverage distal fourth trochanter arrangement, but without first transitioning through a prominent pendant form. Anat Rec, 303:1146-1157, 2020. © 2019 Wiley Periodicals, Inc.

@article{doi101002ar24094,
    author = "Persons, W. Scott and Currie, Philip J.",
    title = "The Anatomical and Functional Evolution of the Femoral Fourth Trochanter in Ornithischian Dinosaurs",
    year = "2019",
    journal = "The Anatomical Record",
    abstract = "The femoral fourth trochanter is the attachment site of the caudofemoralis musculature, which is the primary hindlimb retractor in most non-avian dinosaurs. Early ornithischian dinosaurs are uniquely characterized by a fourth trochanter with a prominent pendant process. Throughout the evolution of ornithischians, the fourth trochanter repeatedly converged on two major morphological changes: (1) the distal migration of the trochanter down the femoral shaft and (2) the loss of the pendant process. Both changes, as well as the original evolution of the pendant form, relate to a single major functional shift emphasizing caudofemoral leverage. Direct evidence of muscle scarring across the surface of the pendant process affirms that it served to extend the attachment of the primary caudofemoralis brevis tendon distally. A proximally located fourth trochanter is the basal condition in dinosaurs and other archosaurs, and the development of a pendant process lengthened the functional lever arm with regard to the insertion of the caudofemoralis. This adaptation afforded improved mechanical advantage, perhaps beneficial in the context of the newly assumed herbivorous diets of basal ornithischians. As some derived ornithischians increased in body size, a high-leverage system with a more distal caudofemoralis attachment evolved. In some groups, the fourth trochanter as a whole descended down the femur, eventually reaching a point where the pendant process was unnecessary. Sauropodomorphs, the other great lineage of dinosaur herbivores, converged on the same high-leverage distal fourth trochanter arrangement, but without first transitioning through a prominent pendant form. Anat Rec, 303:1146-1157, 2020. © 2019 Wiley Periodicals, Inc.",
    url = "https://doi.org/10.1002/ar.24094",
    doi = "10.1002/ar.24094",
    openalex = "W2917848996",
    references = "doi101073pnas251548698, doi101111j109636421956tb02220x, doi101111j109636422001tb01314x, doi101111j1469185x200900094x, doi101111j1469185x201000137x, doi101126science2740914, doi101590s000137652011000100005, doi1016660022336020030770822mbatho20co2, doi1023071292217, doi105860choice326223, openalexw1484431148"
}

Locomotion has influenced the ecology, evolution, and extinction of species throughout history, yet studying locomotion in the fossil record is challenging. Computational biomechanics can provide novel insight by mechanistically relating observed anatomy to whole-animal function and behavior. Here, we leverage optimal control methods to generate the first fully predictive, three-dimensional, muscle-driven simulations of locomotion in an extinct terrestrial vertebrate, the bipedal non-avian theropod dinosaur Coelophysis. Unexpectedly, our simulations involved pronounced lateroflexion movements of the tail. Rather than just being a static counterbalance, simulations indicate that the tail played a crucial dynamic role, with lateroflexion acting as a passive, physics-based mechanism for regulating angular momentum and improving locomotor economy, analogous to the swinging arms of humans. We infer this mechanism to have existed in many other bipedal non-avian dinosaurs as well, and our methodology provides new avenues for exploring the functional diversity of dinosaur tails in the future.

@article{doi101126sciadvabi7348,
    author = "Bishop, Peter J. and Falisse, Antoine and Groote, Friedl De and Hutchinson, John R.",
    title = "Predictive simulations of running gait reveal a critical dynamic role for the tail in bipedal dinosaur locomotion",
    year = "2021",
    journal = "Science Advances",
    abstract = "Locomotion has influenced the ecology, evolution, and extinction of species throughout history, yet studying locomotion in the fossil record is challenging. Computational biomechanics can provide novel insight by mechanistically relating observed anatomy to whole-animal function and behavior. Here, we leverage optimal control methods to generate the first fully predictive, three-dimensional, muscle-driven simulations of locomotion in an extinct terrestrial vertebrate, the bipedal non-avian theropod dinosaur Coelophysis. Unexpectedly, our simulations involved pronounced lateroflexion movements of the tail. Rather than just being a static counterbalance, simulations indicate that the tail played a crucial dynamic role, with lateroflexion acting as a passive, physics-based mechanism for regulating angular momentum and improving locomotor economy, analogous to the swinging arms of humans. We infer this mechanism to have existed in many other bipedal non-avian dinosaurs as well, and our methodology provides new avenues for exploring the functional diversity of dinosaur tails in the future.",
    url = "https://doi.org/10.1126/sciadv.abi7348",
    doi = "10.1126/sciadv.abi7348",
    openalex = "W3199760390",
    references = "doi101002jmor20973, doi101016jgr202008003, doi101371journalpone0192172"
}

@article{farlow2021pedal,
    author = "Farlow, James O. and Falkingham, Peter L. and Therrien, François",
    title = "Pedal proportions of small and large hadrosaurs and other potentially bipedal ornithischian dinosaurs",
    year = "2021",
    journal = "Cretaceous Research",
    url = "https://doi.org/10.1016/j.cretres.2021.104945",
    doi = "10.1016/j.cretres.2021.104945",
    pages = "104945",
    volume = "127"
}

@article{farlow2022pedal,
    author = "Farlow, James O. and Lallensack, Jens N. and Müller, Rodrigo T. and Hyatt, James A.",
    title = "Pedal Skeletal Proportions of Bipedal and Potentially Bipedal Dinosaurs and Other Archosaurs: Interpreting the Makers of Early Mesozoic Footprints",
    year = "2022",
    journal = "Bulletin of the Peabody Museum of Natural History",
    url = "https://doi.org/10.3374/014.063.0201",
    doi = "10.3374/014.063.0201",
    number = "2",
    openalex = "W4298139039",
    volume = "63",
    references = "doi101002ar24199, doi1010079789400904095, doi1010160191814188901083, doi101023a1010933404324, doi101038nature21700, doi101093bioinformaticsbtr597, doi101111j15023931201100276x, doi101111pala12502, doi101111pala12584, doi101126science1198467, doi1018637jssv045i03, doi107312lock90868, openalexw114509570"
}

We present the pelvic and hindlimb musculature of the abelisaurid Skorpiovenator bustingorryi, constituting the most comprehensive muscle reconstruction to date in ceratosaur theropods. Using extant phylogenetic bracket method, we reconstructed 39 muscles that can commonly found in extant archosaurs. Through the identification of bone correlates, we recognized thigh and hindlimb muscles including knee extensors, m. iliofibularis, m. flexor tibialis externus, mm. caudofemorales, mm. puboischiofemorales, and crus muscles important in foot extension and flexion (e.g., m. tibialis anterior, mm. gastrocnemii). Also, autopodial intrinsic muscles were reconstructed whose function involve extension (m. extensor digiti 2-4), flexion (mm. flexor digitorum brevis superficialis), interdigital adduction (m. interosseus dorsalis) and abduction (m. interosseous plantaris, m. abductor 4). Abelisaurids like Skorpiovenator show a deep pre- and postacetabular blade of the ilia and enlarged cnemial crests, which would have helped increasing the moment arm of muscles related to hip flexion and hindlimb extension. Also, pedal muscles related to pronation were probably present but reduced (e.g., m. pronator profundus). Despite some gross differences in the autopodial morphology in extant outgroups (e.g., crocodilian metatarsus and avian tarsometatarsus), the present study allows us to hypothesize several pedal muscles in Skorpiovenator. These muscles would not be arranged in tendinous bundles as in Neornithes, but rather the condition would be similar to that of crocodilians with several layers formed by fleshy bellies on the plantar and dorsal aspects of the metatarsus. The musculature of Skorpiovenator is key for future studies concerning abelisaurid biomechanics, including the integration of functional morphology and ichnological data.

@article{doi101002ar25532,
    author = "Cerroni, Mauricio A. and Otero, Alejandro and Novas, Fernando E.",
    title = "Appendicular myology of Skorpiovenator bustingorryi: A first attempt to reconstruct pelvic and hindlimb musculature in an abelisaurid theropod",
    year = "2024",
    journal = "The Anatomical Record",
    abstract = "We present the pelvic and hindlimb musculature of the abelisaurid Skorpiovenator bustingorryi, constituting the most comprehensive muscle reconstruction to date in ceratosaur theropods. Using extant phylogenetic bracket method, we reconstructed 39 muscles that can commonly found in extant archosaurs. Through the identification of bone correlates, we recognized thigh and hindlimb muscles including knee extensors, m. iliofibularis, m. flexor tibialis externus, mm. caudofemorales, mm. puboischiofemorales, and crus muscles important in foot extension and flexion (e.g., m. tibialis anterior, mm. gastrocnemii). Also, autopodial intrinsic muscles were reconstructed whose function involve extension (m. extensor digiti 2-4), flexion (mm. flexor digitorum brevis superficialis), interdigital adduction (m. interosseus dorsalis) and abduction (m. interosseous plantaris, m. abductor 4). Abelisaurids like Skorpiovenator show a deep pre- and postacetabular blade of the ilia and enlarged cnemial crests, which would have helped increasing the moment arm of muscles related to hip flexion and hindlimb extension. Also, pedal muscles related to pronation were probably present but reduced (e.g., m. pronator profundus). Despite some gross differences in the autopodial morphology in extant outgroups (e.g., crocodilian metatarsus and avian tarsometatarsus), the present study allows us to hypothesize several pedal muscles in Skorpiovenator. These muscles would not be arranged in tendinous bundles as in Neornithes, but rather the condition would be similar to that of crocodilians with several layers formed by fleshy bellies on the plantar and dorsal aspects of the metatarsus. The musculature of Skorpiovenator is key for future studies concerning abelisaurid biomechanics, including the integration of functional morphology and ichnological data.",
    url = "https://doi.org/10.1002/ar.25532",
    doi = "10.1002/ar.25532",
    openalex = "W4400556926",
    references = "doi1010801477201920222093661, doi101098rsos230481, doi101111joa13382"
}

Theropods are obligate bipedal dinosaurs that appeared 230 million years ago and are still extant as birds. Their history is characterized by extreme variations in body mass, with gigantism evolving convergently between many lineages. However, no quantification of hindlimb functional morphology has shown if these body mass increases led to similar specializations between distinct lineages. Here we studied femoral shape variation across 41 species of theropods (n= 68 specimens) using a high-density 3D geometric morphometric approach. We demonstrated that the heaviest theropods evolved wider epiphyses and a more distally located fourth trochanter, as previously demonstrated in early archosaurs, along with an upturned femoral head and a mediodistal crest that extended proximally along the shaft. Phylogenetically informed analyses highlighted that these traits evolved convergently within six major theropod lineages, regardless of their maximum body mass. Conversely, the most gracile femora were distinct from the rest of the dataset, which we interpret as a femoral specialization to "miniaturization" evolving close to Avialae (bird lineage). Our results support a gradual evolution of known "avian" features, such as the fusion between lesser and greater trochanters and a reduction of the epiphyses' offset, independently from body mass variations, which may relate to a more "avian" type of locomotion (more knee-than hip-driven). The distinction between body mass variations and a more "avian" locomotion is represented by a decoupling in the mediodistal crest morphology, whose biomechanical nature should be studied to better understand the importance of its functional role in gigantism, miniaturization and higher parasagittal abilities.

@article{doi101017pab20246,
    author = "Pintore, Romain and Hutchinson, John R and Bishop, Peter J and Tsai, Henry P and Houssaye, Alexandra",
    title = "The evolution of femoral morphology in giant non-avian theropod dinosaurs.",
    year = "2024",
    journal = "Paleobiology",
    abstract = {Theropods are obligate bipedal dinosaurs that appeared 230 million years ago and are still extant as birds. Their history is characterized by extreme variations in body mass, with gigantism evolving convergently between many lineages. However, no quantification of hindlimb functional morphology has shown if these body mass increases led to similar specializations between distinct lineages. Here we studied femoral shape variation across 41 species of theropods (n= 68 specimens) using a high-density 3D geometric morphometric approach. We demonstrated that the heaviest theropods evolved wider epiphyses and a more distally located fourth trochanter, as previously demonstrated in early archosaurs, along with an upturned femoral head and a mediodistal crest that extended proximally along the shaft. Phylogenetically informed analyses highlighted that these traits evolved convergently within six major theropod lineages, regardless of their maximum body mass. Conversely, the most gracile femora were distinct from the rest of the dataset, which we interpret as a femoral specialization to "miniaturization" evolving close to Avialae (bird lineage). Our results support a gradual evolution of known "avian" features, such as the fusion between lesser and greater trochanters and a reduction of the epiphyses' offset, independently from body mass variations, which may relate to a more "avian" type of locomotion (more knee-than hip-driven). The distinction between body mass variations and a more "avian" locomotion is represented by a decoupling in the mediodistal crest morphology, whose biomechanical nature should be studied to better understand the importance of its functional role in gigantism, miniaturization and higher parasagittal abilities.},
    url = "https://pmc.ncbi.nlm.nih.gov/articles/PMC7616063/",
    doi = "10.1017/pab.2024.6",
    pmcid = "PMC7616063",
    pmid = "38846629",
    references = "doi101002ar25047"
}

Several sauropodomorph dinosaurs have been excavated from the Elliot Formation (EF) of Southern Africa which include important taxa such as Massospondylus, Melanorosaurus and Antetonitrus. The study of the bone microstructure of smaller, bipedal Sauropodomorpha and larger, quadrupedal Sauropoda allow us to infer how the growth dynamics changed during the evolution of gigantism. Historically, osteohistological studies of Sauropodomorpha tended to have focused on either early diverging taxa (e.g. Plateosaurus & Massospondylus) or on derived taxa (diplodocids & titanosaurs), whereas studies on the growth dynamics of the transitionary groups (i.e. Sauropodiformes & early Sauropoda) are poorly known. Here, we assess the palaeobiology of two sauropodiformes and an early sauropod by analysing their bone histology. Thin sections of the long bones of two indeterminate sauropodiformes NMQR 3314 and NMQR 1551, and an indeterminate sauropod SAM-PK-K382 were prepared. The general histology of the long bones of all three dinosaurs were similar. Rapid growth through the deposition of fibrolamellar bone tissue characterised their respective ontogenies. Lines of arrested growth (LAGs) were commonly located in the mid and outer cortex signalling the onset of uninterrupted growth. Differences in the histology of these dinosaurs were principally related to the pathological bone tissue evident in the femur of the sauropodiform NMQR 1551 and to the formation of annuli around LAGs in Sauropoda indet., as well as in the location of LAGs in the compacta. The number of LAGs in the cortex varied among the taxa but generally the outer regions of the cortex showed an accumulation of LAGs. The growth dynamics of our three sauropodomorph dinosaurs are similar to early sauropods such as Antetonitrus. It appears that the abundance of fibrolamellar bone tissue and uninterrupted growth at later ontogenetic stages are likely key traits in the early evolution of gigantism in Sauropoda, which supports the occurrence of a mosaic of growth dynamic patterns among transitionary Sauropodomorpha.

@article{doi101111joa14229,
    author = "Toefy, Fay-Yaad and Krupandan, Emil and Chinsamy, Anusuya",
    title = "Palaeobiology and osteohistology of South African sauropodomorph dinosaurs.",
    year = "2025",
    journal = "Journal of anatomy",
    abstract = "Several sauropodomorph dinosaurs have been excavated from the Elliot Formation (EF) of Southern Africa which include important taxa such as Massospondylus, Melanorosaurus and Antetonitrus. The study of the bone microstructure of smaller, bipedal Sauropodomorpha and larger, quadrupedal Sauropoda allow us to infer how the growth dynamics changed during the evolution of gigantism. Historically, osteohistological studies of Sauropodomorpha tended to have focused on either early diverging taxa (e.g. Plateosaurus \& Massospondylus) or on derived taxa (diplodocids \& titanosaurs), whereas studies on the growth dynamics of the transitionary groups (i.e. Sauropodiformes \& early Sauropoda) are poorly known. Here, we assess the palaeobiology of two sauropodiformes and an early sauropod by analysing their bone histology. Thin sections of the long bones of two indeterminate sauropodiformes NMQR 3314 and NMQR 1551, and an indeterminate sauropod SAM-PK-K382 were prepared. The general histology of the long bones of all three dinosaurs were similar. Rapid growth through the deposition of fibrolamellar bone tissue characterised their respective ontogenies. Lines of arrested growth (LAGs) were commonly located in the mid and outer cortex signalling the onset of uninterrupted growth. Differences in the histology of these dinosaurs were principally related to the pathological bone tissue evident in the femur of the sauropodiform NMQR 1551 and to the formation of annuli around LAGs in Sauropoda indet., as well as in the location of LAGs in the compacta. The number of LAGs in the cortex varied among the taxa but generally the outer regions of the cortex showed an accumulation of LAGs. The growth dynamics of our three sauropodomorph dinosaurs are similar to early sauropods such as Antetonitrus. It appears that the abundance of fibrolamellar bone tissue and uninterrupted growth at later ontogenetic stages are likely key traits in the early evolution of gigantism in Sauropoda, which supports the occurrence of a mosaic of growth dynamic patterns among transitionary Sauropodomorpha.",
    url = "https://pmc.ncbi.nlm.nih.gov/articles/PMC12397067/",
    doi = "10.1111/joa.14229",
    pmcid = "PMC12397067",
    pmid = "39960138",
    references = "doi101098rsbl20230245"
}

Before human settlement, New Zealand's avian fauna comprised numerous large flightless birds along with aerial predators, including the formidable Haast's eagle (Hieraaetus moorei). This species vanished concurrently with other New Zealand megafauna, likely due to competition with humans for food resources. The hypothesis that ecological changes drove the extinction of Haast's eagle is grounded in assumptions about its foraging ecology, previously inferred from skeletal morphology. The present study enhances the understanding of the eagle's feeding behavior by reconstructing the muscles and ligaments of its hindlimbs. While structurally similar to other eagles, the hindlimbs of show adaptations for capturing and processing large prey. Notably, the femoral retractors and supinators were significantly enlarged, and the pronators mm. iliotrochanterici originated from a broader pelvic region compared to other species of Accipitridae. Enlarged tubercles on basal phalanges provided an attachment area for larger m. abductor digiti 2 and m. abductor digiti 4 muscles, enhancing the eagle's ability to handle large carcasses. These reconstructions corroborate prior assertions that Haast's eagle was highly adapted for hunting large prey, with its extinction to have likely resulted from an inability to adapt to diminishing megafauna populations.

@article{doi107868s3034545625100026,
    author = "Zinoviev, A. V.",
    title = "HINDLIMB MYOLOGY AND SYNDESMOLOGY OF HAAST'S EAGLE (HIERAAETUS MOOREI, AVES, ACCIPITRIDAE) WITH COMPARATIVE AND FUNCTIONAL NOTES",
    year = "2025",
    journal = "Зоологический журнал / Russian Journal of Zoology",
    abstract = "Before human settlement, New Zealand's avian fauna comprised numerous large flightless birds along with aerial predators, including the formidable Haast's eagle (Hieraaetus moorei). This species vanished concurrently with other New Zealand megafauna, likely due to competition with humans for food resources. The hypothesis that ecological changes drove the extinction of Haast's eagle is grounded in assumptions about its foraging ecology, previously inferred from skeletal morphology. The present study enhances the understanding of the eagle's feeding behavior by reconstructing the muscles and ligaments of its hindlimbs. While structurally similar to other eagles, the hindlimbs of show adaptations for capturing and processing large prey. Notably, the femoral retractors and supinators were significantly enlarged, and the pronators mm. iliotrochanterici originated from a broader pelvic region compared to other species of Accipitridae. Enlarged tubercles on basal phalanges provided an attachment area for larger m. abductor digiti 2 and m. abductor digiti 4 muscles, enhancing the eagle's ability to handle large carcasses. These reconstructions corroborate prior assertions that Haast's eagle was highly adapted for hunting large prey, with its extinction to have likely resulted from an inability to adapt to diminishing megafauna populations.",
    url = "https://www.semanticscholar.org/paper/534f0f40c5a25acfefa0b7a5c6b1202a6e9f8fe2",
    doi = "10.7868/s3034545625100026",
    is_oa = "true",
    number = "10",
    pages = "13",
    semanticscholar_id = "534f0f40c5a25acfefa0b7a5c6b1202a6e9f8fe2",
    volume = "104"
}

@misc{crossrefNonefigure,
    title = "Figure 5: Vertical distribution of air temperature in summer maize canopy.",
    year = "None",
    url = "https://doi.org/10.7717/peerj.12891/fig-5",
    doi = "10.7717/peerj.12891/fig-5"
}

@misc{crossrefNonesupplemental,
    title = "Supplemental Information 6: Pelvic myology of Ornithomimidae indet",
    year = "None",
    url = "https://doi.org/10.7717/peerj.10855/supp-6",
    doi = "10.7717/peerj.10855/supp-6"
}