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Smitanosaurus agilis
Taxonomy
Morosaurus agilis was named by Marsh (1889). Its type specimen is USNM 5384, a partial skeleton (Braincase and partial skull roof, proatlases, and first three cervical vertebrae), and it is a 3D body fossil. Its type locality is Felch Quarry 1, Garden Park, which is in a Kimmeridgian/Tithonian channel sandstone/claystone in the Morrison Formation of Colorado.
It was recombined as Camarasaurus agilis by Hay (1930), Steel (1970); it was recombined as Camarosaurus agilis by Johnson (1931); it was recombined as Smitanosaurus agilis by Whitlock and Wilson Mantilla (2020).
It was recombined as Camarasaurus agilis by Hay (1930), Steel (1970); it was recombined as Camarosaurus agilis by Johnson (1931); it was recombined as Smitanosaurus agilis by Whitlock and Wilson Mantilla (2020).
Synonymy list
| Year | Name and author |
|---|---|
| 1889 | Morosaurus agilis Marsh p. 334 fig. 3 |
| 1890 | Morosaurus agilis Zittel p. 711 |
| 1897 | Morosaurus agilis Marsh p. 498 |
| 1898 | Morosaurus agilis Williston p. 173 |
| 1901 | Morosaurus agilis Nopcsa p. 206 |
| 1902 | Morosaurus agilis Hay p. 483 |
| 1910 | Morosaurus agilis Versluys p. 214 |
| 1916 | Morosaurus agilis Mook p. 139 |
| 1920 | Morosaurus agilis Pompeckj p. 113 |
| 1930 | Camarasaurus agilis Hay p. 191 |
| 1931 | Camarosaurus agilis Johnson p. 358 |
| 1970 | Camarasaurus agilis Steel p. 72 |
| 1999 | Morosaurus agilis Carpenter p. 9 |
| 2020 | Smitanosaurus agilis Whitlock and Wilson Mantilla p. 3–5 |
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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.
†Smitanosaurus agilis Marsh 1889
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Diagnosis
| Reference | Diagnosis | |
|---|---|---|
| J. A. Whitlock and J. A. Wilson Mantilla 2020 | Smitanosaurus agilis is diagnosed by an atlas lacking the ‘lip’ on the anteroventral margin (interpreted as a reversal), an axial neural spine that is both tall (height exceeds that of pedicle; convergently acquired by Amargasaurus and Dicraeosaurus) and subvertically oriented, and an axis with postzygapophyseal articular surfaces that face ventrally rather than posteroventrally. Presence of a small but conspicuous posteriorly projecting spur on the squamosal does not appear to be present in other dicraeosaurid taxa, but the feature is subtle and may not be immediately recognizable depending on preservation. Smitanosaurus agilis is distinguished from Suuwassea by supratemporal fenestrae that are narrower than the maximum height of foramen magnum, the presence of a sharp-lipped pneumatic fossa on the lateral surface of the axial intercentrum, and pleurocoels in anterior cervical vertebrae that extend onto the parapophyses. Smitanosaurus agilis is distinguished from Kaatedocus by the presence of a pineal foramen, a foramen magnum without contribution from the basioccipital, a relatively short, stubby posterior process of the proatlas, the presence of a ‘neck’ on the atlantal neural arch between the pedicle and the postzygapophyses, the presence of diapophyses on the atlantal neural arch, the presence of a strongly arcuate PODL on the axis, the subvertical neural spine of the axis (n.b., the axis associated with the holotype of Kaatedocus is not from the same individual and may not pertain to the same species: E. Tschopp, pers. comm.), the presence of an EPRL in post-axial cervical vertebrae, the absence of the ‘lateral spine cavity’ and an accessory lamina on the neural spine of cervical vertebra 3, the relatively more prominent, subvertical neural spine in cervical vertebra 3, and the absence of a concavity on the posterior ventral surface of the centrum in cervical vertebra 3. Smitanosaurus agilis is distinguished from diplodocids by the presence of a ventrally directed prong on the squamosal.
Upchurch et al. (2004:299) noted that Smitanosaurus agilis has “a craniodorsally directed neural spine of cervical 3.” The preserved anterior margin of the neural spine is indeed inclined anterodorsally, as in dicraeosaurids (Fig. 13), but the damaged posterior and dorsal margins make it difficult to interpret the orientation of the spine as a whole. |
Measurements
No measurements are available
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| Source: infrao = infraorder | |||||
| Reference: Marsh 1875 | |||||
Age range: base of the Late/Upper Kimmeridgian to the top of the Early/Lower Tithonian or 152.21000 to 145.06000 Ma
Collections: one only
| Time interval | Ma | Country or state | Original ID and collection number |
|---|---|---|---|
| Late/Upper Kimmeridgian - Early/Lower Tithonian | USA (Colorado) | Morosaurus agilis (type locality: 28366) |