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Hesperosaurus mjosi
Taxonomy
Hesperosaurus mjosi was named by Carpenter et al. (2001). Its type specimen is HMNS 14 (formerly HMNH 001), a skeleton, and it is a 3D body fossil. Its type locality is Buffalo Quarry, Smith Ranch, which is in a Kimmeridgian terrestrial sandstone in the Morrison Formation of Wyoming.
It was recombined as Stegosaurus mjosi by Maidment et al. (2008), Mateus et al. (2009), Maidment (2010) and Saitta (2015); it was considered a nomen dubium by Galton and Ayyasami (2017).
It was recombined as Stegosaurus mjosi by Maidment et al. (2008), Mateus et al. (2009), Maidment (2010) and Saitta (2015); it was considered a nomen dubium by Galton and Ayyasami (2017).
Synonymy list
| Year | Name and author |
|---|---|
| 2001 | Hesperosaurus mjosi Carpenter et al. |
| 2004 | Hesperosaurus mjosi Galton and Upchurch p. 344 |
| 2006 | Hesperosaurus mjosi Chure et al. p. 237 |
| 2006 | Hesperosaurus mjosi Mateus p. 231 |
| 2007 | Hesperosaurus mjosi Galton p. 25 |
| 2008 | Stegosaurus mjosi Maidment et al. p. 379 |
| 2009 | Stegosaurus mjosi Mateus et al. |
| 2010 | Hesperosaurus mjosi Billon-Bruyat et al. p. 147 |
| 2010 | Hesperosaurus mjosi Carpenter pp. 159-160 |
| 2010 | Hesperosaurus mjosi Christiansen and Tschopp p. 164 |
| 2010 | Hesperosaurus mjosi Galiano and Albersdörfer p. 5 |
| 2010 | Hesperosaurus mjosi Galton p. 195–196 |
| 2010 | Stegosaurus mjosi Maidment p. 203 |
| 2013 | Hesperosaurus mjosi Pereda-Suberbiola et al. p. 72 |
| 2014 | Hesperosaurus mjosi Ulansky p. 5 |
| 2015 | Stegosaurus mjosi Saitta p. 2 |
| 2016 | Hesperosaurus mjosi Borinder et al. p. 64 |
| 2016 | Hesperosaurus mjosi Galton and Carpenter p. 185 |
| 2018 | Hesperosaurus mjosi Maidment et al. p. 2 |
| 2018 | Hesperosaurus mjosi Tumanova and Alifanov p. 1772 fig. 1 |
| 2019 | Hesperosaurus mjosi Costa and Mateus p. 4 |
| 2021 | Hesperosaurus mjosi Breeden et al. p. 21 |
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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.
†Hesperosaurus mjosi Carpenter et al. 2001
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Diagnosis
| Reference | Diagnosis | |
|---|---|---|
| S. C. R. Maidment et al. 2008 | Stegosaurus mjosi differs from S. armatus as the former possesses the following primitive characters: atlas neural arches not fused to intercentrum in ontogenetically mature individuals, postzygapophyses not elevated significantly on posterior cervical vertebrae, neural arches of dorsal vertebrae not elongated above the neural canal, ossified epaxial tendons present, ribs distally expanded, caudal neural spines not bifurcated, enlargement of the distal end of the pubis. It also has the following autapomorphies: 11 dorsal vertebrae, fourth sacral vertebra not fused to sacrum, dorsal dermal plates longer anteroposteriorly than tall dorsoventrally. This combination of autapomorphies and retained plesiomorphies is not seen in any other stegosaur. | |
| K. Carpenter 2010 | Antorbital fenestra large versus very small in Stegosaurus stenops; maxilla short and deep, height equal to half of length, unlike S. stenops where height equals one-third of length; basisphenoid short, long in S. stenops; long-necked stegosaur with 13 cervicals versus 10 in S. stenops; short bodied with 13 dorsals versus 17 in S. stenops; neural arch of mid-dorsals low as in Huayangosaurus taibaii, not tall as in S. stenops; cervical ribs expanded distally, not expanded in S. stenops; tops of neural spines of proximal caudals rounded, not birfurcated as in S. stenops; dorsal edge of scapular blade with distinct step mid-length, no step (margins parallel) in S. stenops; preacetabular process strongly divergent, less so in S. stenops; distal end of prepubic process expanded vertically, unexpanded in S. stenops; distal end of postacetabular process swollen into knob-like structure, unswollen in S. stenops. Mid-dorsal to anterior caudal osteoderm plates vertically low and oval in shape, rather than tall and triangular as in S. stenops. | |
| S. C. R. Maidment et al. 2018 | Hesperosaurus mjosi possesses the following combination of plesiomorphic characters and autapomorphies (the latter marked with an ‘*’): (1) no contact between the lacrimal and prefrontal on the lateral surface of the skull; (2) ventral margin of axis upwardly concave in lateral view*; (3) postzygapophyses not elevated significantly on posterior cervical vertebrae; (4) prezygapophyses join ventrally and face dorsomedially in anterior dorsal vertebrae; (5) dorsal neural arch pedicels not elongated above the neural canal in mid-dorsal vertebrae; (6) dorsal ribs distally expanded; (7) ossified epaxial tendons present; (8) caudal neural spines not bifurcated; (9) dorsal dermal plates longer anteroposteriorly than tall dorsoventrally*. |
Measurements
No measurements are available
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| Source: o = order | |||||
| Reference: Marsh 1875 | |||||
Age range: Kimmeridgian or 157.30000 to 152.10000 Ma
Collections (6 total)
| Time interval | Ma | Country or state | Original ID and collection number |
|---|---|---|---|
| Late/Upper Oxfordian - Early/Lower Kimmeridgian | USA (Wyoming) | Hesperosaurus mjosi (126540) | |
| Kimmeridgian | USA (Wyoming) | Stegosauridae indet. (type locality: 55349) Stegosaurus sp. (38884 46465) | |
| Kimmeridgian | USA (Montana) | Hesperosaurus mjosi (49624) | |
| Kimmeridgian - Tithonian | USA (Montana) | Stegosaurus mjosi (215054) |