Early dinosaurs

@article{roper1891the,
    author = "Roper, G.",
    title = "The Supposed Dicynodont from the Elgin Trias",
    year = "1891",
    journal = "Geological Magazine",
    url = "https://doi.org/10.1017/s0016756800199315",
    doi = "10.1017/s0016756800199315",
    number = "9",
    openalex = "W1997646769",
    pages = "430-430",
    volume = "8"
}

Descriptions are given of various reptilian remains obtained by Mr. William Taylor, J. P., of Lhanbryde, in the Triassic sandstone quarries at Lossiemouth, near Elgin. Thanks to the kind permission of Dr. A. S. Woodward, the fossils were further developed in the Geological Department of the British Museum by Mr. Hall. The remains described belong to three different reptiles.

@article{boulenger1904on,
    author = "Boulenger, George Albert",
    title = "On reptilian remains from the trias of Elgin",
    year = "1904",
    journal = "Proceedings of the Royal Society of London",
    abstract = "Descriptions are given of various reptilian remains obtained by Mr. William Taylor, J. P., of Lhanbryde, in the Triassic sandstone quarries at Lossiemouth, near Elgin. Thanks to the kind permission of Dr. A. S. Woodward, the fossils were further developed in the Geological Department of the British Museum by Mr. Hall. The remains described belong to three different reptiles.",
    url = "https://doi.org/10.1098/rspl.1903.0015",
    doi = "10.1098/rspl.1903.0015",
    number = "477-486",
    openalex = "W2335604474",
    pages = "55-58",
    volume = "72"
}

I. Hyperodapedon Gordoni, Huxley. The reptile from the Elgin sandstone on which Huxley bestowed this name in 1859, and which had so great a bearing on the determination of the age of the deposits in which it was found, has lately been the object of further investigation on the part of Professor R. Burckhardt, who, after a study of the specimen from which Huxley drew up his second account, gave a new interpretation to some of the bones of the skull. It was very much to be desired that further remains should be discovered in order to bring fresh light on the litigious points. I was therefore highly gratified at hearing from my friend Mr. William Taylor, J. P., of Lhanbryde, of the discovery of two new skulls at Lossiemouth, near Elgin, and 1 gladly accepted his kind offer to send me the specimens for examination. I have not been disappointed in my expectation, and it will be seen that the new material affords a substantial supplement to our knowledge of the Triassic Rhynchocephalians.

@article{boulenger1904vion,
    author = "Boulenger, George Albert",
    title = "VI.—On reptilian remains from the trias of Elgin",
    year = "1904",
    journal = "Philosophical Transactions of the Royal Society of London. Series B, Containing Papers of a Biological Character",
    abstract = "I. Hyperodapedon Gordoni, Huxley. The reptile from the Elgin sandstone on which Huxley bestowed this name in 1859, and which had so great a bearing on the determination of the age of the deposits in which it was found, has lately been the object of further investigation on the part of Professor R. Burckhardt, who, after a study of the specimen from which Huxley drew up his second account, gave a new interpretation to some of the bones of the skull. It was very much to be desired that further remains should be discovered in order to bring fresh light on the litigious points. I was therefore highly gratified at hearing from my friend Mr. William Taylor, J. P., of Lhanbryde, of the discovery of two new skulls at Lossiemouth, near Elgin, and 1 gladly accepted his kind offer to send me the specimens for examination. I have not been disappointed in my expectation, and it will be seen that the new material affords a substantial supplement to our knowledge of the Triassic Rhynchocephalians.",
    url = "https://doi.org/10.1098/rstb.1904.0006",
    doi = "10.1098/rstb.1904.0006",
    number = "214-224",
    openalex = "W2076490785",
    pages = "175-189",
    volume = "196"
}

@article{huene1905die,
    author = "Huene, Roland von",
    title = "Die Trias-Dinosaurier Europas",
    year = "1905",
    journal = "Monatsberichte der Deutschen Geologischen Gesellschaft",
    url = "https://doi.org/10.1127/mbzdgg/57/1905/345",
    doi = "10.1127/mbzdgg/57/1905/345",
    number = "9",
    openalex = "W4401913029",
    pages = "345-349",
    volume = "57"
}

Althought so many types of reptiles have been obtained during recent years from the Triassic sandstones of Elgin, Mr. William Taylor has lately discovered two examples of a new form which represents still another group. Through his kindness I have had the privilege of studying these two specimens and comparing them with two more imperfect skeletons of the same animal, which occur on a slab of Elgin Sandstone in the late Mr. James Grant's collection, now in the British Museum (No. R 3.146). All the specimens show merely impressions of bones in the rock, but they occur in counterpart slabs, and many of their most important features can be readily understood with the aid of wax-squeezes taken from the cavities. The four individuals of this new reptile already known are approximately of the same size, each measuring about a decimetre in length to the root of the tail, which is long and slender. They therefore represent a comparatively-diminutive species; and the lightness of the skeleton, with its hollow bones, suggests an animal of remarkable agility (see the accompanying text-figure, p. 141). The head is relatively large, and the neck short. The fore-limbs are small and delicate; while the hind-limbs are very. large, and evidently adapted for a bipedal running or leaping gait. The more important measurements, in millimetres, are as follows:— The large head viewed from above or below, as in the type-specimen (P1. IX, fig. 1), is elongate-triangular in shape, with a sharply-pointed snout. None of its external

@article{doi101144gsljgs1907063010412,
    author = "Woodward, Arthur Smith",
    title = "On a New Dinosaurian Reptile (Scleromochlus Taylori, gen. et sp. nov.) from the Trias of Lossiemouth, Elgin",
    year = "1907",
    journal = "Quarterly Journal of the Geological Society",
    abstract = "Althought so many types of reptiles have been obtained during recent years from the Triassic sandstones of Elgin, Mr. William Taylor has lately discovered two examples of a new form which represents still another group. Through his kindness I have had the privilege of studying these two specimens and comparing them with two more imperfect skeletons of the same animal, which occur on a slab of Elgin Sandstone in the late Mr. James Grant's collection, now in the British Museum (No. R 3.146). All the specimens show merely impressions of bones in the rock, but they occur in counterpart slabs, and many of their most important features can be readily understood with the aid of wax-squeezes taken from the cavities. The four individuals of this new reptile already known are approximately of the same size, each measuring about a decimetre in length to the root of the tail, which is long and slender. They therefore represent a comparatively-diminutive species; and the lightness of the skeleton, with its hollow bones, suggests an animal of remarkable agility (see the accompanying text-figure, p. 141). The head is relatively large, and the neck short. The fore-limbs are small and delicate; while the hind-limbs are very. large, and evidently adapted for a bipedal running or leaping gait. The more important measurements, in millimetres, are as follows:— The large head viewed from above or below, as in the type-specimen (P1. IX, fig. 1), is elongate-triangular in shape, with a sharply-pointed snout. None of its external",
    url = "https://doi.org/10.1144/gsl.jgs.1907.063.01-04.12",
    doi = "10.1144/gsl.jgs.1907.063.01-04.12",
    openalex = "W2168571875"
}

The fore limb of Ornithosuchus woodwardi is shown in a specimen in the Manchester Museum. It is small, only about one-half the size of the hind leg. The scapula is much expanded at both ends, and is indistinguishably fused with the coracoid. The latter bone is pierced by a large foramen. The humerus is a slender bone, somewhat twisted, but not much expanded at the ends; it has a distinct ectepicondylar groove. The ulna is very broad at the proximal end, but narrows distally; its proximal portion forms a thin plate of bone. The radius crosses the ulna, its proximal end lying entirely in front of it, while the distal ends of the two bones lie side by side. The carpus cannot be made out. Only metacarpals 1, 2, and 3 are functional; but a possible representative of 4 lies closely pressed to the back of the other three. Both phalanges of digit 1 are preserved, the last being a strong claw. Ornithosuchus is restored as an animal walking on all fours, with the head carried rather low. The proportions are identical with those of Ætosaurus. A description is given of the skeleton of a very small reptile, interesting as recalling Ætosaurus in its armour, and because it shows the whole of the animal except the tail.

@article{watson1909on,
    author = "Watson, D. M. S.",
    title = "On some Reptilian Remains from the Trias of Lossiemouth (Elgin)",
    year = "1909",
    journal = "Quarterly Journal of the Geological Society of London",
    abstract = "The fore limb of Ornithosuchus woodwardi is shown in a specimen in the Manchester Museum. It is small, only about one-half the size of the hind leg. The scapula is much expanded at both ends, and is indistinguishably fused with the coracoid. The latter bone is pierced by a large foramen. The humerus is a slender bone, somewhat twisted, but not much expanded at the ends; it has a distinct ectepicondylar groove. The ulna is very broad at the proximal end, but narrows distally; its proximal portion forms a thin plate of bone. The radius crosses the ulna, its proximal end lying entirely in front of it, while the distal ends of the two bones lie side by side. The carpus cannot be made out. Only metacarpals 1, 2, and 3 are functional; but a possible representative of 4 lies closely pressed to the back of the other three. Both phalanges of digit 1 are preserved, the last being a strong claw. Ornithosuchus is restored as an animal walking on all fours, with the head carried rather low. The proportions are identical with those of Ætosaurus. A description is given of the skeleton of a very small reptile, interesting as recalling Ætosaurus in its armour, and because it shows the whole of the animal except the tail.",
    url = "https://doi.org/10.1144/gsl.jgs.1909.065.01-04.26",
    doi = "10.1144/gsl.jgs.1909.065.01-04.26",
    number = "1-4",
    openalex = "W2090470009",
    pages = "440-440",
    volume = "65"
}

@misc{huene1910ein1,
    author = "Huene, F. R. von",
    title = "Ein primitiver Dinosaurier aus der mittleren Trias von Elgin",
    year = "1910",
    howpublished = "Geologie und Palaeontologie, Abh., v. 8, p. 315-322",
    note = "talkorigins\_source = {true}; raw\_reference = {Huene, F. R. von, 1910, Ein primitiver Dinosaurier aus der mittleren Trias von Elgin: Geologie und Palaeontologie, Abh., v. 8, p. 315-322.}"
}

@article{thulborn1978aestivation,
    author = "Thulborn, Richard A.",
    title = "Aestivation among ornithopod dinosaurs of the African Trias",
    year = "1978",
    journal = "Lethaia",
    url = "https://doi.org/10.1111/j.1502-3931.1978.tb01226.x",
    doi = "10.1111/j.1502-3931.1978.tb01226.x",
    number = "3",
    openalex = "W2116370468",
    pages = "185-198",
    volume = "11",
    references = "doi101038130791a0, doi1010381961074a0, doi101038scientificamerican0459105, doi101098rstb19650003, doi101111j146979981973tb04654x, doi101111j155856461971tb01922x, doi1023072406945, doi102475ajs2628975, doi105962bhltitle52196, openalexw3126336940"
}

@article{tietze1982zur,
    author = "Tietze, Klaus-Werner",
    title = "Zur Geometrie einiger Flüsse im Mittleren Buntsandstein (Trias)",
    year = "1982",
    journal = "Geologische Rundschau",
    url = "https://doi.org/10.1007/bf01821105",
    doi = "10.1007/bf01821105",
    number = "3",
    openalex = "W2005481581",
    pages = "813-828",
    volume = "71",
    references = "doi101007bf01820816, doi101007bf01821101, doi101007bf01821104, doi101007bf01989593, doi101017s0016756800036098, doi10130674d72a272b2111d78648000102c1865d, doi104324978020337108412, openalexw1566381105, openalexw1912927042, openalexw616953834"
}

@article{schultze1986wirbeltierreste,
    author = "Schultze, Hans-Peter and Kansas, Lawrence and Möller, HeIko",
    title = "Wirbeltierreste aus dem mittleren muschelkalk (trias) von göttingen, west-deutschland",
    year = "1986",
    journal = "Paläontologische Zeitschrift",
    url = "https://doi.org/10.1007/bf02989426",
    doi = "10.1007/bf02989426",
    number = "1-2",
    openalex = "W235002700",
    pages = "109-129",
    volume = "60",
    references = "doi101007978364275829422, doi101007bf01803031, doi101007bf02987700, doi101007bf03160419, doi105962bhltitle159141, doi105962p313860, openalexw1486658933, openalexw2225079715, openalexw2938517358"
}

Lizards, snakes and amphisbaenians together constitute the Squamata, the largest and most diverse group of living reptiles. Despite their current success, the early squamate fossil record is extremely patchy. The last major survey of squamate palaeontology and evolution was published 20 years ago. Since then, there have been major changes in systematic theory and methodology, as well as a steady trickle of new fossil finds. This review examines our current understanding of the first 150 million years of squamate evolution in the light of the new data and changing ideas. Contrary to previous reports, no squamate fossils are currently documented before the Jurassic. Nonetheless, indirect evidence predicts that squamates had evolved by at least the middle Triassic, and had diversified into existing major lineages before the end of this period. There is thus a major gap in the squamate record at a time when key morphological features were evolving. With the exception of fragmentary remains from Africa and India, Jurassic squamates are known only from localities in northern continents (Laurasia). The situation improves in the Early Cretaceous, but the southern (Gondwanan) record remains extremely poor. This constrains palaeobiogeographic discussion and makes it difficult to predict centres of origin for major squamate clades on the basis of fossil evidence alone. Preliminary mapping of morphological characters onto a consensus tree demonstrates stages in the sequence of acquisition for some characters of the skull and postcranial skeleton, but many crucial stages--most notably those relating to the acquisition of squamate skull kinesis--remain unclear.

@article{doi101017s1464793103006134,
    author = "Evans, Susan E.",
    title = "At the feet of the dinosaurs: the early history and radiation of lizards",
    year = "2003",
    journal = "Biological reviews/Biological reviews of the Cambridge Philosophical Society",
    abstract = "Lizards, snakes and amphisbaenians together constitute the Squamata, the largest and most diverse group of living reptiles. Despite their current success, the early squamate fossil record is extremely patchy. The last major survey of squamate palaeontology and evolution was published 20 years ago. Since then, there have been major changes in systematic theory and methodology, as well as a steady trickle of new fossil finds. This review examines our current understanding of the first 150 million years of squamate evolution in the light of the new data and changing ideas. Contrary to previous reports, no squamate fossils are currently documented before the Jurassic. Nonetheless, indirect evidence predicts that squamates had evolved by at least the middle Triassic, and had diversified into existing major lineages before the end of this period. There is thus a major gap in the squamate record at a time when key morphological features were evolving. With the exception of fragmentary remains from Africa and India, Jurassic squamates are known only from localities in northern continents (Laurasia). The situation improves in the Early Cretaceous, but the southern (Gondwanan) record remains extremely poor. This constrains palaeobiogeographic discussion and makes it difficult to predict centres of origin for major squamate clades on the basis of fossil evidence alone. Preliminary mapping of morphological characters onto a consensus tree demonstrates stages in the sequence of acquisition for some characters of the skull and postcranial skeleton, but many crucial stages--most notably those relating to the acquisition of squamate skull kinesis--remain unclear.",
    url = "https://doi.org/10.1017/s1464793103006134",
    doi = "10.1017/s1464793103006134",
    openalex = "W2170009771",
    references = "doi101002jmor1051110306, doi10108000222938400770131, doi10108002724634199210011475, doi101098rstb19830079, doi101111j109636421978tb00376x, doi101111j136531211990tb00103x, doi1016710272463420020220286lftlca20co2, doi105860choice325663, openalexw2261909166, openalexw337536883"
}

Abstract An accumulation of skeletons of the pre-dinosaur Silesaurus opolensis, gen. et sp. nov. is described from the Keuper (Late Triassic) claystone of Krasiejów in southern Poland. The strata are correlated with the late Carnian Lehrberg Beds and contain a diverse assemblage of tetrapods, including the phytosaur Paleorhinus, which in other regions of the world co-occurs with the oldest dinosaurs. A narrow pelvis with long pubes and the extensive development of laminae in the cervical vertebrae place S. opolensis close to the origin of the clade Dinosauria above Pseudolagosuchus, which agrees with its geological age. Among the advanced characters is the beak on the dentaries, and the relatively low tooth count. The teeth have low crowns and wear facets, which are suggestive of herbivory. The elongate, but weak, front limbs are probably a derived feature.

@article{doi101671a1097,
    author = "Dzik, Jerzy",
    title = "A beaked herbivorous archosaur with dinosaur affinities from the early Late Triassic of Poland",
    year = "2003",
    journal = "Journal of Vertebrate Paleontology",
    abstract = "Abstract An accumulation of skeletons of the pre-dinosaur Silesaurus opolensis, gen. et sp. nov. is described from the Keuper (Late Triassic) claystone of Krasiejów in southern Poland. The strata are correlated with the late Carnian Lehrberg Beds and contain a diverse assemblage of tetrapods, including the phytosaur Paleorhinus, which in other regions of the world co-occurs with the oldest dinosaurs. A narrow pelvis with long pubes and the extensive development of laminae in the cervical vertebrae place S. opolensis close to the origin of the clade Dinosauria above Pseudolagosuchus, which agrees with its geological age. Among the advanced characters is the beak on the dentaries, and the relatively low tooth count. The teeth have low crowns and wear facets, which are suggestive of herbivory. The elongate, but weak, front limbs are probably a derived feature.",
    url = "https://doi.org/10.1671/a1097",
    doi = "10.1671/a1097",
    openalex = "W2101751293",
    references = "doi101016s001669959880123x, doi101016s0031018298001175, doi101038361064a0, doi10108002724634199110011386, doi10108002724634199110011426, doi10108002724634199910011178, doi101098rstb19990489, doi10718895fylantbak30809522, openalexw2310875238, openalexw2788234611, openalexw606525048, openalexw616953834, sereno1997the"
}

The oldest unequivocal records of Dinosauria were unearthed from Late Triassic rocks (approximately 230 Ma) accumulated over extensional rift basins in southwestern Pangea. The better known of these are Herrerasaurus ischigualastensis, Pisanosaurus mertii, Eoraptor lunensis, and Panphagia protos from the Ischigualasto Formation, Argentina, and Staurikosaurus pricei and Saturnalia tupiniquim from the Santa Maria Formation, Brazil. No uncontroversial dinosaur body fossils are known from older strata, but the Middle Triassic origin of the lineage may be inferred from both the footprint record and its sister-group relation to Ladinian basal dinosauromorphs. These include the typical Marasuchus lilloensis, more basal forms such as Lagerpeton and Dromomeron, as well as silesaurids: a possibly monophyletic group composed of Mid-Late Triassic forms that may represent immediate sister taxa to dinosaurs. The first phylogenetic definition to fit the current understanding of Dinosauria as a node-based taxon solely composed of mutually exclusive Saurischia and Ornithischia was given as "all descendants of the most recent common ancestor of birds and Triceratops". Recent cladistic analyses of early dinosaurs agree that Pisanosaurus mertii is a basal ornithischian; that Herrerasaurus ischigualastensis and Staurikosaurus pricei belong in a monophyletic Herrerasauridae; that herrerasaurids, Eoraptor lunensis, and Guaibasaurus candelariensis are saurischians; that Saurischia includes two main groups, Sauropodomorpha and Theropoda; and that Saturnalia tupiniquim is a basal member of the sauropodomorph lineage. On the contrary, several aspects of basal dinosaur phylogeny remain controversial, including the position of herrerasaurids, E. lunensis, and G. candelariensis as basal theropods or basal saurischians, and the affinity and/or validity of more fragmentary taxa such as Agnosphitys cromhallensis, Alwalkeria maleriensis, Chindesaurus bryansmalli, Saltopus elginensis, and Spondylosoma absconditum. The identification of dinosaur apomorphies is jeopardized by the incompleteness of skeletal remains attributed to most basal dinosauromorphs, the skulls and forelimbs of which are particularly poorly known. Nonetheless, Dinosauria can be diagnosed by a suite of derived traits, most of which are related to the anatomy of the pelvic girdle and limb. Some of these are connected to the acquisition of a fully erect bipedal gait, which has been traditionally suggested to represent a key adaptation that allowed, or even promoted, dinosaur radiation during Late Triassic times. Yet, contrary to the classical "competitive" models, dinosaurs did not gradually replace other terrestrial tetrapods over the Late Triassic. In fact, the radiation of the group comprises at least three landmark moments, separated by controversial (Carnian-Norian, Triassic-Jurassic) extinction events. These are mainly characterized by early diversification in Carnian times, a Norian increase in diversity and (especially) abundance, and the occupation of new niches from the Early Jurassic onwards. Dinosaurs arose from fully bipedal ancestors, the diet of which may have been carnivorous or omnivorous. Whereas the oldest dinosaurs were geographically restricted to south Pangea, including rare ornithischians and more abundant basal members of the saurischian lineage, the group achieved a nearly global distribution by the latest Triassic, especially with the radiation of saurischian groups such as "prosauropods" and coelophysoids.

@article{doi101111j1469185x200900094x,
    author = "Langer, Max C. and Ezcurra, Martín D. and Bittencourt, Jonathas S. and Novas, Fernando E.",
    title = "The origin and early evolution of dinosaurs",
    year = "2009",
    journal = "Biological reviews/Biological reviews of the Cambridge Philosophical Society",
    abstract = {The oldest unequivocal records of Dinosauria were unearthed from Late Triassic rocks (approximately 230 Ma) accumulated over extensional rift basins in southwestern Pangea. The better known of these are Herrerasaurus ischigualastensis, Pisanosaurus mertii, Eoraptor lunensis, and Panphagia protos from the Ischigualasto Formation, Argentina, and Staurikosaurus pricei and Saturnalia tupiniquim from the Santa Maria Formation, Brazil. No uncontroversial dinosaur body fossils are known from older strata, but the Middle Triassic origin of the lineage may be inferred from both the footprint record and its sister-group relation to Ladinian basal dinosauromorphs. These include the typical Marasuchus lilloensis, more basal forms such as Lagerpeton and Dromomeron, as well as silesaurids: a possibly monophyletic group composed of Mid-Late Triassic forms that may represent immediate sister taxa to dinosaurs. The first phylogenetic definition to fit the current understanding of Dinosauria as a node-based taxon solely composed of mutually exclusive Saurischia and Ornithischia was given as "all descendants of the most recent common ancestor of birds and Triceratops". Recent cladistic analyses of early dinosaurs agree that Pisanosaurus mertii is a basal ornithischian; that Herrerasaurus ischigualastensis and Staurikosaurus pricei belong in a monophyletic Herrerasauridae; that herrerasaurids, Eoraptor lunensis, and Guaibasaurus candelariensis are saurischians; that Saurischia includes two main groups, Sauropodomorpha and Theropoda; and that Saturnalia tupiniquim is a basal member of the sauropodomorph lineage. On the contrary, several aspects of basal dinosaur phylogeny remain controversial, including the position of herrerasaurids, E. lunensis, and G. candelariensis as basal theropods or basal saurischians, and the affinity and/or validity of more fragmentary taxa such as Agnosphitys cromhallensis, Alwalkeria maleriensis, Chindesaurus bryansmalli, Saltopus elginensis, and Spondylosoma absconditum. The identification of dinosaur apomorphies is jeopardized by the incompleteness of skeletal remains attributed to most basal dinosauromorphs, the skulls and forelimbs of which are particularly poorly known. Nonetheless, Dinosauria can be diagnosed by a suite of derived traits, most of which are related to the anatomy of the pelvic girdle and limb. Some of these are connected to the acquisition of a fully erect bipedal gait, which has been traditionally suggested to represent a key adaptation that allowed, or even promoted, dinosaur radiation during Late Triassic times. Yet, contrary to the classical "competitive" models, dinosaurs did not gradually replace other terrestrial tetrapods over the Late Triassic. In fact, the radiation of the group comprises at least three landmark moments, separated by controversial (Carnian-Norian, Triassic-Jurassic) extinction events. These are mainly characterized by early diversification in Carnian times, a Norian increase in diversity and (especially) abundance, and the occupation of new niches from the Early Jurassic onwards. Dinosaurs arose from fully bipedal ancestors, the diet of which may have been carnivorous or omnivorous. Whereas the oldest dinosaurs were geographically restricted to south Pangea, including rare ornithischians and more abundant basal members of the saurischian lineage, the group achieved a nearly global distribution by the latest Triassic, especially with the radiation of saurischian groups such as "prosauropods" and coelophysoids.},
    url = "https://doi.org/10.1111/j.1469-185x.2009.00094.x",
    doi = "10.1111/j.1469-185x.2009.00094.x",
    openalex = "W2121596487",
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}

@incollection{crossref2014early,
    title = "Early Trias(sic)",
    year = "2014",
    booktitle = "Dictionary Geotechnical Engineering/Wörterbuch GeoTechnik",
    url = "https://doi.org/10.1007/978-3-642-41714-6\_50017",
    doi = "10.1007/978-3-642-41714-6\_50017",
    openalex = "W4252730834",
    pages = "445-445"
}

Triassic predatory guild evolution reflects a period of ecological flux spurred by the catastrophic end-Permian mass extinction and terminating with the global ecological dominance of dinosaurs in the early Jurassic. In responding to this dynamic ecospace, terrestrial predator diversity attained new levels, prompting unique trophic webs with a seeming overabundance of carnivorous taxa and the evolution of entirely new predatory clades. Key among these was Crocodylomorpha, the largest living reptiles and only one of two archosaurian lineages that survive to the present day. In contrast to their existing role as top, semi-aquatic predators, the earliest crocodylomorphs were generally small-bodied, terrestrial faunivores, occupying subsidiary (meso) predator roles. Here we describe Carnufex carolinensis a new, unexpectedly large-bodied taxon with a slender and ornamented skull from the Carnian Pekin Formation (~231 Ma), representing one of the oldest and earliest diverging crocodylomorphs described to date. Carnufex bridges a problematic gap in the early evolution of pseudosuchians by spanning key transitions in bauplan evolution and body mass near the origin of Crocodylomorpha. With a skull length of >50 cm, the new taxon documents a rare instance of crocodylomorphs ascending to top-tier predator guilds in the equatorial regions of Pangea prior to the dominance of dinosaurs.

@article{doi101038srep09276,
    author = "Zanno, Lindsay E. and Drymala, Susan and Nesbitt, Sterling J. and Schneider, Vincent P.",
    title = "Early crocodylomorph increases top tier predator diversity during rise of dinosaurs",
    year = "2015",
    journal = "Scientific Reports",
    abstract = "Triassic predatory guild evolution reflects a period of ecological flux spurred by the catastrophic end-Permian mass extinction and terminating with the global ecological dominance of dinosaurs in the early Jurassic. In responding to this dynamic ecospace, terrestrial predator diversity attained new levels, prompting unique trophic webs with a seeming overabundance of carnivorous taxa and the evolution of entirely new predatory clades. Key among these was Crocodylomorpha, the largest living reptiles and only one of two archosaurian lineages that survive to the present day. In contrast to their existing role as top, semi-aquatic predators, the earliest crocodylomorphs were generally small-bodied, terrestrial faunivores, occupying subsidiary (meso) predator roles. Here we describe Carnufex carolinensis a new, unexpectedly large-bodied taxon with a slender and ornamented skull from the Carnian Pekin Formation (\textasciitilde 231 Ma), representing one of the oldest and earliest diverging crocodylomorphs described to date. Carnufex bridges a problematic gap in the early evolution of pseudosuchians by spanning key transitions in bauplan evolution and body mass near the origin of Crocodylomorpha. With a skull length of >50 cm, the new taxon documents a rare instance of crocodylomorphs ascending to top-tier predator guilds in the equatorial regions of Pangea prior to the dominance of dinosaurs.",
    url = "https://doi.org/10.1038/srep09276",
    doi = "10.1038/srep09276",
    openalex = "W2061422371",
    references = "doi101144sp3794"
}

Dinosaurs dominated Mesozoic terrestrial ecosystems for ∼160 million years, but their biogeographic origin remains poorly understood. The earliest unequivocal dinosaur fossils appear in the Carnian (∼230 Ma) of southern South America and Africa, leading most authors to propose southwestern Gondwana as the likely center of origin. However, the high taxonomic and morphological diversity of these earliest assemblages suggests a more ancient evolutionary history that is currently unsampled. Phylogenetic uncertainty at the base of Dinosauria, combined with the subsequent appearance of dinosaurs throughout Laurasia in their early evolutionary history, further complicates this picture. Here, we estimate the distribution of early dinosaurs and their archosaurian relatives under a phylogenetic maximum likelihood framework, testing alternative topological arrangements and incorporating potential abiotic barriers to dispersal into our biogeographic models. For the first time, we include spatiotemporal sampling heterogeneity in these models, which frequently supports a low-latitude Gondwanan origin for dinosaurs. These results are best supported when silesaurids are constrained as early-diverging ornithischians, which is likely because this topology accounts for the otherwise substantial ornithischian ghost lineage, explaining the group's absence from the fossil record prior to the Early Jurassic. Our results suggest that the archosaur radiation also took place within low-latitude Gondwana following the end-Permian extinction before lineages dispersed across Pangaea into ecologically and climatically distinct provinces during the Late Triassic. Mesozoic terrestrial vertebrates are under-sampled at low paleolatitudes, and our findings suggest that heterogeneous sampling has hitherto obscured the true paleobiogeographic origin of dinosaurs and their kin.

@article{doi101016jcub202412053,
    author = "Heath, Joel A and Cooper, Natalie and Upchurch, Paul and Mannion, Philip D.",
    title = "Accounting for sampling heterogeneity suggests a low paleolatitude origin for dinosaurs",
    year = "2025",
    journal = "Current Biology",
    abstract = "Dinosaurs dominated Mesozoic terrestrial ecosystems for ∼160 million years, but their biogeographic origin remains poorly understood. The earliest unequivocal dinosaur fossils appear in the Carnian (∼230 Ma) of southern South America and Africa, leading most authors to propose southwestern Gondwana as the likely center of origin. However, the high taxonomic and morphological diversity of these earliest assemblages suggests a more ancient evolutionary history that is currently unsampled. Phylogenetic uncertainty at the base of Dinosauria, combined with the subsequent appearance of dinosaurs throughout Laurasia in their early evolutionary history, further complicates this picture. Here, we estimate the distribution of early dinosaurs and their archosaurian relatives under a phylogenetic maximum likelihood framework, testing alternative topological arrangements and incorporating potential abiotic barriers to dispersal into our biogeographic models. For the first time, we include spatiotemporal sampling heterogeneity in these models, which frequently supports a low-latitude Gondwanan origin for dinosaurs. These results are best supported when silesaurids are constrained as early-diverging ornithischians, which is likely because this topology accounts for the otherwise substantial ornithischian ghost lineage, explaining the group's absence from the fossil record prior to the Early Jurassic. Our results suggest that the archosaur radiation also took place within low-latitude Gondwana following the end-Permian extinction before lineages dispersed across Pangaea into ecologically and climatically distinct provinces during the Late Triassic. Mesozoic terrestrial vertebrates are under-sampled at low paleolatitudes, and our findings suggest that heterogeneous sampling has hitherto obscured the true paleobiogeographic origin of dinosaurs and their kin.",
    url = "https://doi.org/10.1016/j.cub.2024.12.053",
    doi = "10.1016/j.cub.2024.12.053",
    openalex = "W4406758949",
    references = "doi101016jjsames2021103341, doi101016jpgeola202307002, doi101038s4158602205133x, doi101073pnas1319091111, doi101093bioinformaticsbty633, doi101093sysbio461195, doi101093sysbiosys029, doi101093sysbiosyt040, doi101093sysbiosyu056, doi101109tac19741100705, doi101111j2041210x201100169x, doi1021425f55419694, doi1023073802723"
}

Abstract Known from exquisitely preserved specimens from early Norian beds of southern Brazil, Macrocollum itaquii is a crucial taxon for understanding sauropodomorph evolution. This species provides a glimpse at the transition between the earliest sauropodomorphs and the classic ‘prosauropods’. To date, the appendicular anatomy of this taxon has not been described in detail. Therefore, in this contribution we present a detailed description of its appendicular skeleton. As expected from its chronostratigraphic position, the limbs of M. itaquii exhibit a combination of plesiomorphic (e.g. absence of a radial fossa, ossified proximal carpals, iliac acetabular wall not fully open) and derived traits (e.g. metacarpal I inset into the carpus, sub-triangular preacetabular process, straight femur). Phylogenetic analyses support the classification of this taxon, along with two or three other Norian taxa, as members of Unaysauridae, an early radiation of plateosaurian sauropodomorphs. An articulated wrist offers rare insights into this region, confirming that sauropodomorphs (like other dinosaur groups) ancestrally possessed at least nine carpals. This finding enhances our understanding of carpal morphology and evolution within sauropodomorphs. Macrocollum itaquii reveals the presence of a unique third phalanx of manual digit V, raising questions about the confidence we can infer the phalangeal counts of the outermost digits.

@article{doi101093zoolinneanzlaf100,
    author = "Fonseca, André O. and de, Fabiula Prestes and Müller, Rodrigo Temp",
    title = "Osteology of the appendicular skeleton of Macrocollum itaquii (Dinosauria: Sauropodomorpha) sheds light on early dinosaur wrist evolution",
    year = "2025",
    journal = "Zoological Journal of the Linnean Society",
    abstract = "Abstract Known from exquisitely preserved specimens from early Norian beds of southern Brazil, Macrocollum itaquii is a crucial taxon for understanding sauropodomorph evolution. This species provides a glimpse at the transition between the earliest sauropodomorphs and the classic ‘prosauropods’. To date, the appendicular anatomy of this taxon has not been described in detail. Therefore, in this contribution we present a detailed description of its appendicular skeleton. As expected from its chronostratigraphic position, the limbs of M. itaquii exhibit a combination of plesiomorphic (e.g. absence of a radial fossa, ossified proximal carpals, iliac acetabular wall not fully open) and derived traits (e.g. metacarpal I inset into the carpus, sub-triangular preacetabular process, straight femur). Phylogenetic analyses support the classification of this taxon, along with two or three other Norian taxa, as members of Unaysauridae, an early radiation of plateosaurian sauropodomorphs. An articulated wrist offers rare insights into this region, confirming that sauropodomorphs (like other dinosaur groups) ancestrally possessed at least nine carpals. This finding enhances our understanding of carpal morphology and evolution within sauropodomorphs. Macrocollum itaquii reveals the presence of a unique third phalanx of manual digit V, raising questions about the confidence we can infer the phalangeal counts of the outermost digits.",
    url = "https://doi.org/10.1093/zoolinnean/zlaf100",
    doi = "10.1093/zoolinnean/zlaf100",
    openalex = "W4414011209",
    references = "doi105852ejt20239132375"
}

Over 230 million years of Earth's history, dinosaurs became a major terrestrial animal clade and produced one of the most species-rich living tetrapod lineages: birds. Yet, largely because of uncertainty surrounding the phylogeny of early dinosaurs, the tempo and mode of their emergence and initial radiation remain poorly constrained. Here, we reconstruct the initial diversification of dinosaurs through Bayesian tip-dating analyses. Using nine morphological datasets, we estimate that dinosaurs emerged between 250 and 240 Ma, 10 million years before the earliest unambiguous dinosaur fossils. The emergence of the dinosaurs was followed by the rapid appearance and diversification of all major lineages, coinciding with a burst of morphological evolution that peaked in the early Late Triassic. The patterns that we infer are consistent with the expectations under a scenario of evolutionary radiation, in which ecologically disparate lineages rapidly diversify from a single common ancestor. In turn, our results provide a biological explanation for the instability surrounding early dinosaur phylogeny and suggest that the diversity of dinosaurs has been sculpted by multiple rapid radiations following successive mass extinctions in deep time.

@article{doi101098rspb20260102,
    author = "Brownstein, Chase Doran and Griffin, Christopher Thomas",
    title = "An early burst of skeletal evolution at the origin of dinosaurs.",
    year = "2026",
    journal = "Proceedings. Biological sciences",
    abstract = "Over 230 million years of Earth's history, dinosaurs became a major terrestrial animal clade and produced one of the most species-rich living tetrapod lineages: birds. Yet, largely because of uncertainty surrounding the phylogeny of early dinosaurs, the tempo and mode of their emergence and initial radiation remain poorly constrained. Here, we reconstruct the initial diversification of dinosaurs through Bayesian tip-dating analyses. Using nine morphological datasets, we estimate that dinosaurs emerged between 250 and 240 Ma, 10 million years before the earliest unambiguous dinosaur fossils. The emergence of the dinosaurs was followed by the rapid appearance and diversification of all major lineages, coinciding with a burst of morphological evolution that peaked in the early Late Triassic. The patterns that we infer are consistent with the expectations under a scenario of evolutionary radiation, in which ecologically disparate lineages rapidly diversify from a single common ancestor. In turn, our results provide a biological explanation for the instability surrounding early dinosaur phylogeny and suggest that the diversity of dinosaurs has been sculpted by multiple rapid radiations following successive mass extinctions in deep time.",
    url = "https://pubmed.ncbi.nlm.nih.gov/42014084/",
    doi = "10.1098/rspb.2026.0102",
    pmid = "42014084"
}