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Psephophorus polygonus
Taxonomy
Psephophorus polygonus was named by von Meyer (1847). Its type specimen is NHMW 2011/0330/0001 (neotype), a partial shell (a slab containing ridge and non-ridge ossicles), and it is a 3D body fossil.
Synonyms
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Synonymy list
| Year | Name and author |
|---|---|
| 1847 | Psephophorus polygonus von Meyer |
| 1909 | Psephophorus calvertensis Palmer |
| 1930 | Psephophorus calvertensis Hay p. 69 |
| 1930 | Psephophorus polygonus Hay p. 69 |
| 1995 | Psephophorus calvertensis Köhler |
| 1995 | Psephophorus polygonus Köhler |
| 2006 | Psephophorus polygonus Chesi and Delfino p. 102 |
| 2013 | Psephophorus polygonus Delfino et al. |
| 2019 | Psephophorus polygonus Peters et al. p. 126 |
| 2023 | Psephophorus polygonus Weems |
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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.
†Psephophorus polygonus von Meyer 1847
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Invalid names: Psephophorus calvertensis Palmer 1909 [synonym]
Diagnosis
| Reference | Diagnosis | |
|---|---|---|
| M. Delfino et al. 2013 | Because only shell fragments are known from the type locality, this diagnosis is based only on the morphology and arrangement of the ossicles forming the shell. P. polygonus differs from all the other dermochelyid turtles provided with an ‘epithecal’ shell formed by several small bony ossicles based on the following combination of characters: thick ossicles; ossicles not greatly varying in size and shape; ossicle edges with reduced sutural structures; ossicles not arranged in the ‘sunflower’ pattern typical of Natemys; largest ossicles arranged in several longitudinal ridges; ridge-forming ossicles often viscerally flat (ridge expressed only on the external surface) and dorsally arched in cross-section, but in some cases viscerally concave (the ridge is also expressed on the visceral surface) and tectiform in cross-section; ridge ossicles characterized by variable thicknesses but without evident external keels (present in Dermochelys; compare Fig. 1 with Fig. 2); presence of peaks and valleys on the longitudinal ridges; peaks and bottom of the valleys corresponding to the sutures among ossicles; neighbouring longitudinal ridges separated by at least five ossicles (which are 13 on average in the remains from Southern Italy; Chesi et al. 2007).
From a histological perspective, P. polygonus differs at least from D. coriacea in having shell ossicles that retain the diploe structure with an internal cortical coarse fibrous meshwork throughout ontogeny (the ossicles of D. coriacea do not have the internal cortex). | |
| M. E. Peters et al. 2019 | see p. 129-130 | |
| R. E. Weems 2023 | On the basis of the following combination of characters (adapted from Delfino et al., 2013), P. polygonus differs from other dermochelyid turtles possessing an “epithecal” shield formed by numerous small bony ossicles: thick ossicles; ossicles not greatly varying in size and shape; ossicles edges with reduced sutural structures; ossicles not arranged in the “sunflower” pattern typical of Natemys; largest ossicles arranged in several longitudinal ridges, dorsally arched in cross section and often viscerally flat (i.e., ridge is expressed only on the dorsal surface), although sometimes viscerally concave (i.e., the ridge curvature is also expressed on the visceral surface) and tectiform in cross section; ridge ossicles characterized by variable thicknesses but lacking true external keels like those present in Dermochelys; “peaks and valleys” are present along the longitudinal ridges, with peaks and bottoms of the valleys corresponding to ossicle suture boundaries; neighboring longitudinal ridges separated by at least five and often many more than five ossicles. |
Measurements
No measurements are available
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| Source: f = family, c = class, subp = subphylum | |||||
| References: Uetz 2005, Carroll 1988, Hendy et al. 2009 | |||||
Age range: base of the Burdigalian to the top of the Tortonian or 20.44000 to 7.24600 Ma
Collections (13 total)
| Time interval | Ma | Country or state | Original ID and collection number |
|---|---|---|---|
| Burdigalian | USA (Maryland) | Psephophorus calvertensis (70817) Psephophorus polygonus (71810) | |
| Burdigalian - Messinian | Italy (Apulia) | Psephophorus polygonus (47125) | |
| Langhian | USA (Maryland) | Psephophorus polygonus (70818) | |
| Langhian | USA (Virginia) | Psephophorus calvertensis (79793) | |
| Langhian - Serravallian | Italy (Benevento) | Psephophorus sp. (190853) | |
| Serravallian | USA (Maryland) | Psephophorus polygonus (71533 97475) | |
| Badenian | Slovakia | Psephophorus polygonus (73137) | |
| Tortonian | USA (Virginia) | Psephophorus calvertensis (152251) | |
| Tortonian | USA (Maryland) | Psephophorus polygonus (219172 221449) | |
| Tortonian | Netherlands | Psephophorus polygonus (190169) |