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Yimenosaurus youngi
Taxonomy
Yimenosaurus youngi was named by Bai et al. (1990). Its type specimen is YXV 8701 and is a 3D body fossil. Its type locality is Jiaojiadian (YXV), which is in a Hettangian terrestrial mudstone in the Fengjiahe Formation of China.
Synonymy list
| Year | Name and author |
|---|---|
| 1990 | Yimenosaurus youngi Bai et al. pp. 14-15 figs. 1-3, Pl. 1 |
| 2004 | Yimenosaurus youngi Galton and Upchurch p. 236 |
| 2007 | Yimenosaurus youngi Lü et al. p. 13 |
| 2011 | Yimenosaurus youngi Apaldetti et al. p. 4 |
| 2020 | Yimenosaurus youngi Peyre de Fabrègues et al. p. 4 fig. 4 |
| 2022 | Yimenosaurus yangi Yao et al. p. 4 |
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If no rank is listed, the taxon is considered an unranked clade in modern classifications. Ranks may be repeated or presented in the wrong order because authors working on different parts of the classification may disagree about how to rank taxa.
†Yimenosaurus youngi Bai et al. 1990
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Diagnosis
| Reference | Diagnosis | |
|---|---|---|
| Z. Bai et al. 1990 | A moderate to large prosauropod which may attain nine meters in length, skull
height-length proportion is moderate with length of skull approximately 1.65 its height (including mandible), and cranial construction is relatively delicate with elements composing the skull, being relatively long and gracile. External nares are elliptical and relatively large, orbits are subcircular and moderate in size, and antorbital fenestra is triangular and large. Premaxilla and ascending process of the maxilla are relatively well developed but the ventral dental margin is rather shortened anteroposteriorly. The mandible is relatively delicately constructed, medial portion of the ramus is relatively high, mandibular fenestra is well developed, articular process lies ventral to the plane of the dentition, and the articular is relatively weak but well developed. Dentition is relatively long with dental formula as: Premaxilla: 4, Maxilla: 17-18, Dentary: 21-23. Dentition is compact, crowns are relatively high, slightly spoon-shaped with a gently convex labial margin, gently concave lingual margin, medial ridge is not well developed, but teeth are all conspicuously striated, and anterior and posterior margins have well developed denticles. Presacral vertebral endochondral construction is compact and with the exception of the atlas and axis, all vertebrae are amphicoelous. A proatlas is present, associated with a slightly elongated intercentrum, and the neural arch and two well developed lophs of the postzygopophyses are relatively well developed. Cervical vertebrae are relatively elongated, medial cervicals are rather reduced, pleurocoels are undeveloped, there is a conspicuous ventral keel, and neural arch and spine are low and simply constructed. Dorsal vertebrae are relatively long and rather laterally compressed with low neural arches and spines shaped as thin plated crests. Three amphiplatyan sacral vertebrae are present with strong centra which maintain low and thinly walled neural arches and spines, while ribs and zygopophyses are fused to compose a robust sacral yoke supporting a powerful ilium. Anterior caudals are short, robust, and amphicoelous; neural arches and spines are relatively low, diapophyses are relatively well developed, haemal arches are particularly well developed, anterior haemal arches are spinous and particularly robust with club-shaped distal ends. Scapula is straight and thick but with an intense medial curvature and a relatively narrow anterior oblique depression. The coracoid is short with a thickened margin. Its proximal end contacts the anterior scapula to compose a broad and spacious glenoid fossa. Humerus is short three-fifths the length of the femur, thick, lacks curvature, has a well developed medial head, and a strong deltopectoral crest. The sacrum is robust with a relatively low ilium that maintains well developed pubic and ischiac peduncles. Pubis and ischium are long, obturator foramen is large and open, and a relatively large and inflated distal crest on the pubis is present for enhanced muscle attachment. Ischium is relatively short and thick, possesses a well developed proximal puboischiatic plate for contact with the pubis, distal ends are relatively elongated, expanded, and fused, and there is a coarsened crest for enhanced muscle attachment. The femur is robust with a conspicuous sinuous curvature, shaft is subcircular in cross section with thickened walls, a distinct neck between head and shaft is absent, greater trochanter is well developed, lesser trochanter is inconspicuous, fourth trochanter is well developed and located posterodorsally on the midshaft, distal condyles are not exceptionally defined, and intercondylar notch is shallow. Tibia and fibula are nearly equivalent in length, and the tibia is two-thirds the length of the femur. The astragalus is massive, the two proximal articular facets are relatively well developed, the distal astragalar process is well developed, and the mediolateral breadth of the foot exceeds the anteroposterior length. Calcaneum is small and thick with a long and spherical proximal end. Five long and robust metatarsals are present but phalanges are rather short and thick. Pes formula is 1-2-3-4-1. Digit V is reduced, the ungual on digit I is robust but unguals on the remaining digits II, III, and IV are weakened and reduced. (Translated by W. Downs.) |
Measurements
No measurements are available
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| Source: infrao = infraorder, c = class, subp = subphylum | |||||
| References: Hendy et al. 2009, Carroll 1988, Norman and Weishampel 1991 | |||||
Age range: Hettangian or 201.40000 to 199.50000 Ma
Collections: one only
| Time interval | Ma | Country or state | Original ID and collection number |
|---|---|---|---|
| Hettangian | China (Yunnan) | Yimenosaurus youngi (type locality: 56155) |