IV. Ornithodira The Ornithodira are the bird-like archosaurs and they include dinosaurs, pterosaurs and incompletely known forms. As stated before their shared derived characteristic is a mesotarsal ankle.
The Pterosauria are the most completely known of the non-dinosaurian ornithodirans to arise in the Triassic. Their earliest appearance is from the Late Triassic of northern Italy, Germany, and Greenland.
Their shared derived character is the very elongate finger that supports a wing. We will look at them in more detail in the next lecture.
Another early ornithodiran is Lagosuchus, known from several partial skeletons from the Ischigualasto Formation. It is a small lightly built animal with very long legs.
Reconstruction of the skeleton of Lagosuchus, after Paul (1988). The brown color indicates the distribution of light armor and the manus is not preserved in the existing material (green).
Pelvis of Lagosuchus; after Arcucci (1996).
Phytosauria (Onderorde) Familie Phytosauridae
Ornithosuchida (Onderorde) Familie Ornithosuchidae
This list of crurotarsans is a comprehensive listing of all genera that have ever been included in the clade Crurotarsi, excluding purely vernacular terms. Under some definitions Crurotarsi includes all archosaurs, but this list excludes archosaur genera that are included in Avemetatarsalia (pterosaurs, nonavian dinosaurs, and birds). The list includes all commonly accepted genera, but also genera that are now considered invalid, doubtful (nomen dubium), or were not formally published (nomen nudum), as well as junior synonyms of more established names, and genera that are no longer considered crurotarsan. Extinct taxa are denoted with a dagger (†). The list contains 527 names, of which approximately 422 are considered either valid crurotarsan genera or nomina dubia.
There is no official, canonical list of crurotarsan genera, but one of the most thorough attempts can be found on the Crurotarsi section of Mikko Haaramo's Phylogeny Archive. That list has been supplemented with the Paleofile listing for Crocodylomorpha.
Naming conventions and terminology follow the International Code of Zoological Nomenclature. Technical terms used include:
Junior synonym: A name which describes the same taxon as a previously published name. If two or more genera are formally designated and the type specimens are later assigned to the same genus, the first to be published (in chronological order) is the senior synonym, and all other instances are junior synonyms. Senior synonyms are generally used, except by special decision of the ICZN, but junior synonyms cannot be used again, even if deprecated. Junior synonymy is often subjective, unless the genera described were both based on the same type specimen.
Nomen nudum (Latin for "naked name"): A name that has appeared in print but has not yet been formally published by the standards of the ICZN. Nomina nuda (the plural form) are invalid, and are therefore not italicized as a proper generic name would be. If the name is later formally published, that name is no longer a nomen nudum and will be italicized on this list. Often, the formally published name will differ from any nomina nuda that describe the same specimen. In this case, these nomina nuda will be deleted from this list in favor of the published name.
Preoccupied name: A name that is formally published, but which has already been used for another taxon. This second use is invalid (as are all subsequent uses) and the name must be replaced. As preoccupied names are not valid generic names, they will also go unitalicized on this list.
Nomen dubium (Latin for "dubious name"): A name describing a fossil with no unique diagnostic features. This can be an extremely subjective and controversial designation and is to be used cautiously.