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Anchisaurus polyzelus

Reptilia

Taxonomy
Megadactylus polyzelus was named by Hitchcock (1865). It is a 3D body fossil. Its type locality is Springfield Armory, which is in a Hettangian/Sinemurian terrestrial sandstone in the Portland Formation of Massachusetts. It is the type species of Anchisaurus, Amphisaurus, Megadactylus.

It was recombined as Amphisaurus polyzelus by Marsh (1882); it was recombined as Thecodontosaurus polyzelus by Huene (1906), Huene (1914), Huene (1914), Huene (1926), Kuhn (1939) and Huene (1940); it was recombined as Anchisaurus polyzelus by Marsh (1885), Marsh (1896), Nopcsa (1901), Hay (1902), Hay (1910), Lull (1912), Lull (1915), Lull (1917), Hay (1930), Lull (1953), Steel (1970), Galton (1971), Galton (1973), Galton (1976), Galton and Cluver (1976), Attridge et al. (1985), Fedak (2003), Galton and Upchurch (2004), Weishampel (2006), Fedak and Galton (2007), Upchurch et al. (2007), Galton (2007), Barrett et al. (2007), Smith and Pol (2007), Nesbitt et al. (2007), Yates (2010), Tweet and Santucci (2011) and Apaldetti et al. (2011).

Synonyms
Synonymy list
YearName and author
1865Megadactylus polyzelus Hitchcock p. 40
1870Megadactylus polyzelus Cope pp. 122-E–122-F
1882Amphisaurus polyzelus Marsh
1882Megadactylus polyzelus Quenstedt p. 130
1885Anchisaurus polyzelus Marsh
1889Anchisaurus major Marsh pp. 331-332 fig. 1
1890Anchisaurus major Zittel p. 730
1891Ammosaurus major Marsh p. 267
1891Anchisaurus colurus Marsh pp. 267-268
1892Anchisaurus solus Marsh p. 545
1896Anchisaurus colurus Gaudry p. 94
1896Anchisaurus polyzelus Marsh pp. 147-148
1896Ammosaurus major Marsh p. 148
1896Anchisaurus colurus Marsh p. 150
1896Anchisaurus solus Marsh p. 151
1898Megadactylus polyzelus Hitchcock p. 405
1898Anchisaurus colurus Woodward p. 197
1901Anchisaurus coelurus Gadow p. 421
1901Ammosaurus major Nopcsa p. 196
1901Anchisaurus colurus Nopcsa p. 196
1901Anchisaurus polyzelus Nopcsa p. 196
1901Anchisaurus solus Nopcsa p. 196
1902Ammosaurus major Hay p. 491
1902Anchisaurus colurus Hay p. 491
1902Anchisaurus polyzelus Hay p. 491
1902Anchisaurus solus Hay p. 491
1902Anchisaurus colurus Mansel-Pleydell p. lxxix
1904Anchisaurus colurus Lull p. 470
1906Thecodontosaurus polyzelus Huene
1908Anchisaurus colurus Abel p. 210
1910Anchisaurus colurus Hay p. 12
1910Anchisaurus polyzelus Hay p. 19
1910Anchisaurus colurus Versluys p. 205
1911Anchisaurus major von Zittel p. 280
1912Ammosaurus major Lull p. 411
1912Anchisaurus colurus Lull p. 411
1912Anchisaurus polyzelus Lull p. 411
1912Anchisaurus solus Lull p. 411
1914Ammosaurus major Huene p. 13
1914Anchisaurus colurus Huene p. 13
1914Anchisaurus solus Huene p. 13
1914Thecodontosaurus polyzelus Huene p. 13
1914Anchisaurus colurus Huene p. 69
1914Ammosaurus major Huene p. 74
1914Thecodontosaurus polyzelus Huene p. 75
1914Anchisaurus colurus Huene p. 156
1915Anchisaurus polyzelus Lull p. 119
1915Anchisaurus colurus Lull p. 130
1915Anchisaurus solus Lull p. 144
1915Ammosaurus major Lull pp. 148-149
1917Ammosaurus major Lull p. 111
1917Anchisaurus colurus Lull p. 111
1917Anchisaurus polyzelus Lull p. 111
1917Anchisaurus solus Lull p. 111
1920Anchisaurus solus Van Hoepen p. 92
1922Anchisaurus coelurus Case p. 80
1926Anchisaurus colurus Huene p. 6
1926Anchisaurus solus Huene p. 6
1926Thecodontosaurus polyzelus Huene p. 6
1928Anchisaurus major Perrier p. 3087
1930Anchisaurus polyzelus Hay p. 170
1930Ammosaurus major Hay p. 171
1930Anchisaurus colurus Hay p. 171
1930Anchisaurus solus Hay p. 171
1932Ammosaurus solus Huene
1932Yaleosaurus colurus Huene pp. 119-120
1939Ammosaurus major Kuhn p. 33
1939Ammosaurus solus Kuhn p. 33
1939Thecodontosaurus polyzelus Kuhn p. 61
1939Yaleosaurus colurus Kuhn p. 63
1940Thecodontosaurus polyzelus Huene p. 37
1941Yaleosaurus colurus Huene p. 141
1941Yaleosaurus colurus Young p. 206
1952Yaleosaurus colurus Bock p. 405
1953Anchisaurus polyzelus Lull p. 99
1953Yaleosaurus colurus Lull p. 107
1953Anchisaurus solus Lull p. 120
1953Ammosaurus major Lull pp. 124-125
1958Ammosaurus major Kuhn p. 22
1958Yaleosaurus solus Kuhn p. 22
1964Ammosaurus major Tatarinov p. 530
1964Anchisaurus colurus Tatarinov p. 541
1967Ammosaurus major Charig p. 713
1967Ammosaurus solus Charig p. 713
1970Ammosaurus major Demathieu p. 153
1970Yaleosaurus colurus Demathieu p. 153
1970Ammosaurus major Steel p. 48
1970Ammosaurus solus Steel p. 48
1970Anchisaurus polyzelus Steel p. 48
1970Yaleosaurus colurus Steel p. 52
1971Anchisaurus polyzelus Galton p. 782
1973Ammosaurus major Benedetto
1973Anchisaurus polyzelus Galton p. 247
1976Anchisaurus polyzelus Galton p. 88
1976Anchisaurus polyzelus Galton and Cluver p. 132
1976Ammosaurus major Galton and Cluver p. 143
1984Ammosaurus major Olsen and Galton p. 93
1985Ammosaurus major Attridge et al. p. 128
1985Anchisaurus polyzelus Attridge et al. p. 128
2003Anchisaurus polyzelus Fedak p. 49A
2004Ammosaurus major Galton and Upchurch p. 234
2004Anchisaurus polyzelus Galton and Upchurch p. 234
2006Anchisaurus polyzelus Weishampel p. 138
2006Ammosaurus major Weishampel p. 139
2007Anchisaurus polyzelus Barrett et al. p. 321
2007Anchisaurus polyzelus Fedak and Galton p. 248
2007Anchisaurus polyzelus Galton p. 517
2007Anchisaurus polyzelus Nesbitt et al. p. 236
2007Anchisaurus polyzelus Smith and Pol p. 669
2007Ammosaurus major Upchurch et al. p. 75
2007Anchisaurus polyzelus Upchurch et al. p. 75
2009Ammosaurus major Bittencourt and Kellner p. 34
2010Anchisaurus polyzelus Yates p. 744
2011Anchisaurus polyzelus Apaldetti et al. p. 4
2011Anchisaurus polyzelus Tweet and Santucci p. 78
2011Ammosaurus major Tweet and Santucci p. 79

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RankNameAuthor
kingdomAnimalia()
Bilateria
EubilateriaAx 1987
Deuterostomia
phylumChordataHaeckel 1874
subphylumVertebrata
superclassGnathostomata
Osteichthyes()
subclassSarcopterygii()
subclassDipnotetrapodomorpha(Nelson 2006)
subclassTetrapodomorpha()
Tetrapoda
Reptiliomorpha
Anthracosauria
subclassAmphibiosauriaKuhn 1967
Cotylosauria()
Amniota
Sauropsida
classReptilia
RankNameAuthor
subclassEureptilia()
Romeriida
Diapsida()
Archosauromorpha(Huene 1946)
Crocopoda
ArchosauriformesGauthier 1986
Eucrocopoda
Archosauria()
informalAvemetatarsalia
Ornithodira
Dinosauromorpha
Dinosauriformes
Dinosauria()
Saurischia()
Eusaurischia
Sauropodomorpha(Huene 1932)
Massopoda
genusAnchisaurus
speciespolyzelus()

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.

Anchisaurus polyzelus Hitchcock 1865
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Invalid names: Ammosaurus major Marsh 1889 [synonym], Ammosaurus solus Marsh 1892 [synonym], Anchisaurus colurus Marsh 1891 [synonym]
Diagnosis
ReferenceDiagnosis
A. M. Yates 2010the following four characters remain as valid autapomorphies of Anchisaurus polyzelus.
1. A lateral pit on the lateral distal surface of the quadrate, just above the articular condyle (Yates 2004, fig. 4). This character is only observable in YPM 1883.
2. Foramen, or pit, opening ventrally on the base of the second sacral rib (Yates 2004, fig. 1). Originally described as a foramen, Sereno (2007) pointed out that it has not been demonstrated to penetrate deeply into the cortex of the bone. Nevertheless, the feature remains distinctive and it stands as a valid autapomorphy. It is visible in YPM 208 and YPM 1883.
3. A long, narrow preacetabular lobe of the ilium that is at least twice as long as it is high at its base (Galton 1976, fig. 19a, 26e). This character can be observed in YPM 208 and YPM 1883.
4. Dorsoventrally flattened ischial blades (mid-blade depth is less than 75 per cent of its width) with the long axis 7. of the cross-section set at a low angle to the horizontal (Text-fig. 2). This character is described above and replaces the ‘flat, coplanar ischial blades’ listed by
Yates (2004, p. 7). This character can be observed in the holotype, AM 41⁄109, YPM 208 and YPM 209.
In addition to these characters, a further three new autapomorphies can be added:
5. Transversely expanded ventral ramus of the postorbital
(Yates 2004, fig. 8). This character was included by me in the list of derived character states that linked Anchisaurus to the sauropod clade, albeit with an ambiguous distribution. However, plesiomorphic, unexpanded postorbital ventral rami are now known to be present in sauropodomorphs closer to Sauropoda than Anchisaurus is (e.g. Melanorosaurus readi, Yates 2007b; Aardonyx celestae, Yates et al. 2010) and in basal sauropods (e.g. Tazoudasaurus naimi, Allain and Aquesbi 2008; Shunosaurus lii, Wilson and Sereno 1998). Thus, the ambiguity of this character is now clearly resolved in favour of an independant derivation in Anchisaurus and eusauropods more derived than Shunosaurus. Thus, the character is an autapomorphy for Anchisaurus convergent in derived Eusauropods. Of the Anchisaurus specimens the character is only visible in YPM 1883.
Posterior dorsal centra approximately twice as long as the height of the centrum face (Galton 1976, fig. 15i, j). This autapomorphy was suggested by Sereno (2007) and can be observed in YPM 208, YPM 209 and YPM 1883. The proportions of dorsal centra do vary with size within Sauropodomorpha with smaller individuals tending to have more elongate dorsal centra (Yates 2007b, discussion of character 151 in Table 2). Nevertheless, similar sized posterior dorsal centra of Thecodontosaurus antiquus (BRSUG unnumbered; centrum length: 34 mm) and Massospondylus carinatus (BP ⁄ 1 ⁄ 5143; centrum length 42 mm) have a length : height ratio well under 2 (1.38 and 1.35, respectively), indicating that the proportions of Anchisaurus are unusual even for its small size and qualify as an autapomorphy.
Slender first sacral rib with a base occupying less than half of the length of the first sacral centrum (Text-fig. 3). This novel character is discussed above. It can be observed in AM 41 ⁄ 109, YPM 208 and YPM 1883.