Polyphyly

Evidence relating to dinosaur origins, dinosaur physiology and bird ancestry is reviewed. The thesis that birds evolved directly from theropod dinosaurs is perfectly acceptable. There is no convincing evidence to support the view that dinosaurs were endotherms, with an avian system of thermo-regulation, and the biological success of dinosaurs is explicable in terms of straightforward anatomical adaptations (particularly the development of an enarthrodial hip joint). There is considerable evidence in favour of dinosaurian polyphyly. The dinosaur order Saurischia is apparently diphyletic - sauropods and prosauropods having descended from proterosuchian thecodonts, and theropods probably having evolved from pseudosuchian thecodonts. The ancestry of the dinosaur order Ornithischia remains a matter for speculation. The tarsal and pelvic structures of pseudosuchian thecodonts are not irreconcilable with those of dinosaurs, and the differences that do exist are not sufficient to debar pseudosuchians from consideration as dinosaur ancestors. The common pattern of limb joint structure in Triassic dinosaurs is not conclusive evidence of dinosaur monophyly, and is probably nothing more than a consequence of parallel evolution across the thecodontian- dinosaurian boundary. A new classification of archosaurs and birds is presented, wherein the theropod ancestors of birds are transferred to the class Aves while all other dinosaurs (sauropods, prosauropods and ornithischians) are retained in the reptilian subclass Archosauria. This scheme places full emphasis on the dinosaurian ancestry of birds but still manages to retain the stability of conventional classifications.

@article{thulborn1975dinosaur,
    author = "Thulborn, RA",
    title = "Dinosaur polyphyly and the classification of Archosaurs and birds",
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    journal = "Australian Journal of Zoology",
    abstract = "Evidence relating to dinosaur origins, dinosaur physiology and bird ancestry is reviewed. The thesis that birds evolved directly from theropod dinosaurs is perfectly acceptable. There is no convincing evidence to support the view that dinosaurs were endotherms, with an avian system of thermo-regulation, and the biological success of dinosaurs is explicable in terms of straightforward anatomical adaptations (particularly the development of an enarthrodial hip joint). There is considerable evidence in favour of dinosaurian polyphyly. The dinosaur order Saurischia is apparently diphyletic - sauropods and prosauropods having descended from proterosuchian thecodonts, and theropods probably having evolved from pseudosuchian thecodonts. The ancestry of the dinosaur order Ornithischia remains a matter for speculation. The tarsal and pelvic structures of pseudosuchian thecodonts are not irreconcilable with those of dinosaurs, and the differences that do exist are not sufficient to debar pseudosuchians from consideration as dinosaur ancestors. The common pattern of limb joint structure in Triassic dinosaurs is not conclusive evidence of dinosaur monophyly, and is probably nothing more than a consequence of parallel evolution across the thecodontian- dinosaurian boundary. A new classification of archosaurs and birds is presented, wherein the theropod ancestors of birds are transferred to the class Aves while all other dinosaurs (sauropods, prosauropods and ornithischians) are retained in the reptilian subclass Archosauria. This scheme places full emphasis on the dinosaurian ancestry of birds but still manages to retain the stability of conventional classifications.",
    url = "https://doi.org/10.1071/zo9750249",
    doi = "10.1071/zo9750249",
    number = "2",
    pages = "249-270",
    volume = "23"
}

@article{thulborn1975dinosaur1,
    author = "Thulborn, R. A",
    title = "Dinosaur polyphyly and the classification of archosaurs and birds",
    year = "1975",
    journal = "Aust. Journal Zoology, v. 23, p. 249-270",
    note = "talkorigins\_source = {true}; raw\_reference = {Thulborn, R. A., 1975, Dinosaur polyphyly and the classification of archosaurs and birds: Aust. Journal Zoology, v. 23, p. 249-270.}"
}

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}

In the early 1990s some isolated finds of strange bird-like dinosaurs from Argentina and Mongolia threw a spanner in the works of determining bird origins. The discovery of partial skeletons of Alvarezsaurus from Argentina and Mononykus from Mongolia revealed that the boundary between bipedal running dinosaurs and flightless birds was totally blurred. Then the discovery of more complete remains of a similar beast, Shuvuuia from Mongolia, revealed the true nature of these strange beasts. They had long legs, curved, delicate necks, small, gracile heads with tiny teeth, and short, powerful arms each with one very large claw and two remnant smaller claws.

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    abstract = "In the early 1990s some isolated finds of strange bird-like dinosaurs from Argentina and Mongolia threw a spanner in the works of determining bird origins. The discovery of partial skeletons of Alvarezsaurus from Argentina and Mononykus from Mongolia revealed that the boundary between bipedal running dinosaurs and flightless birds was totally blurred. Then the discovery of more complete remains of a similar beast, Shuvuuia from Mongolia, revealed the true nature of these strange beasts. They had long legs, curved, delicate necks, small, gracile heads with tiny teeth, and short, powerful arms each with one very large claw and two remnant smaller claws.",
    url = "https://doi.org/10.1093/oso/9780195372663.003.0009",
    doi = "10.1093/oso/9780195372663.003.0009",
    pages = "25-28"
}

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@article{crossref2016first,
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@article{farré2016novel,
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@article{nesbitt2017the,
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@article{watson2017dinosaur,
    author = "Watson, Traci",
    title = "Dinosaur trio roosted together like birds",
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}

Dinosaurs thrived and reproduced in various regions worldwide, including the Arctic. In order to understand their nesting in diverse or extreme environments, the relationships between nests, nesting environments, and incubation methods in extant archosaurs were investigated. Statistical analyses reveal that species of extant covered nesters (i.e., crocodylians and megapodes) preferentially select specific sediments/substrates as a function of their nesting style and incubation heat sources. Relationships between dinosaur eggs and the sediments in which they occur reveal that hadrosaurs and some sauropods (i.e., megaloolithid eggs) built organic-rich mound nests that relied on microbial decay for incubation, whereas other sauropods (i.e., faveoloolithid eggs) built sandy in-filled hole nests that relied on solar or potentially geothermal heat for incubation. Paleogeographic distribution of mound nests and sandy in-filled hole nests in dinosaurs reveals these nest types produced sufficient incubation heat to be successful up to mid latitudes (≤47°), 10° higher than covered nesters today. However, only mound nesting and likely brooding could have produced sufficient incubation heat for nesting above the polar circle (>66°). As a result, differences in nesting styles may have placed restrictions on the reproduction of dinosaurs and their dispersal at high latitudes.

@article{tanaka2018nest,
    author = "Tanaka, Kohei and Zelenitsky, Darla K. and Therrien, François and Kobayashi, Yoshitsugu",
    title = "Nest substrate reflects incubation style in extant archosaurs with implications for dinosaur nesting habits",
    year = "2018",
    journal = "Scientific Reports",
    abstract = "Dinosaurs thrived and reproduced in various regions worldwide, including the Arctic. In order to understand their nesting in diverse or extreme environments, the relationships between nests, nesting environments, and incubation methods in extant archosaurs were investigated. Statistical analyses reveal that species of extant covered nesters (i.e., crocodylians and megapodes) preferentially select specific sediments/substrates as a function of their nesting style and incubation heat sources. Relationships between dinosaur eggs and the sediments in which they occur reveal that hadrosaurs and some sauropods (i.e., megaloolithid eggs) built organic-rich mound nests that relied on microbial decay for incubation, whereas other sauropods (i.e., faveoloolithid eggs) built sandy in-filled hole nests that relied on solar or potentially geothermal heat for incubation. Paleogeographic distribution of mound nests and sandy in-filled hole nests in dinosaurs reveals these nest types produced sufficient incubation heat to be successful up to mid latitudes (≤47°), 10° higher than covered nesters today. However, only mound nesting and likely brooding could have produced sufficient incubation heat for nesting above the polar circle (>66°). As a result, differences in nesting styles may have placed restrictions on the reproduction of dinosaurs and their dispersal at high latitudes.",
    url = "https://doi.org/10.1038/s41598-018-21386-x",
    doi = "10.1038/s41598-018-21386-x",
    number = "1",
    volume = "8"
}