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Helochelydra bakewelli
Taxonomy
Trionyx bakewelli was named by Mantell (1833). Its type specimen is BMNH 2265, a carapace (isolated costal bone), and it is a 3D body fossil. Its type locality is Tilgate Forest, Cuckfield, which is in a Valanginian terrestrial sandstone in the Tunbridge Wells Sand Formation of the United Kingdom.
It was recombined as Tretosternum bakewelli by Lydekker (1889) and Delair (1958); it was recombined as Compsemys bakewelli by Joyce et al. (2011); it was recombined as Helochelydra bakewelli by Milner (2004), Milner (2011) and Joyce (2017).
It was recombined as Tretosternum bakewelli by Lydekker (1889) and Delair (1958); it was recombined as Compsemys bakewelli by Joyce et al. (2011); it was recombined as Helochelydra bakewelli by Milner (2004), Milner (2011) and Joyce (2017).
Synonymy list
| Year | Name and author |
|---|---|
| 1833 | Trionyx bakewelli Mantell |
| 1889 | Tretosternum bakewelli Lydekker p. 138 |
| 1958 | Tretosternum bakewelli Delair p. 50 |
| 2004 | Helochelydra bakewelli Milner p. 1457 figs. Text-figure 10B |
| 2011 | Compsemys bakewelli Joyce et al. p. 79 fig. 3A |
| 2011 | Helochelydra bakewelli Milner p. 299 fig. 23.3A |
| 2017 | Helochelydra bakewelli Joyce |
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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.
†Helochelydra bakewelli Mantell 1833
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Diagnosis
| Reference | Diagnosis | |
|---|---|---|
| G. A. Mantell 1833 | From the slight degree of convexity of the rib, it is clear that the original was of a flattened form, like the common turtle, 'Testudo mydas ; the shagreened surface proves its analogy to the trionyx ; but the impressions of the scales show that it cannot be identified with any recent species. | |
| A. R. Milner 2004 | Species of Helochelydra in which the hyoplastron has the following characters: ventral surface covered with low tubercles tending to coalesce into groups of 2–3; border with entoplastron is concave, suture with epiplastron is perpendicular to antero-posterior axis; suture with entoplastron occupies one third of width of anterior ramus of hyoplastron; border between humeral and pectoral scutes gently curves posteromedially to midline and touches posterior end of entoplastron. Most of the above characteristics distinguish it from H. nopcsai, but the coalescing tubercles and the margin between the humeral and pectoral scutes also distinguish it from H. anglica from Purbeck. | |
| W. G. Joyce et al. 2011 | Revised diagnosis using sculpturing only. A taxon defined exclusively by the surface pattern of its shell, which consists of low, rounded, robust tubercles that often coalesce into groups of twos and threes and fade towards the centre of the carapace. |
Measurements
No measurements are available
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| Source: c = class, subp = subphylum, uc = unranked clade | |||||
| References: Hendy et al. 2009, Carroll 1988 | |||||
Age range: base of the Valanginian to the top of the Late/Upper Valanginian or 139.80000 to 136.40000 Ma
Collections (3 total)
| Time interval | Ma | Country or state | Original ID and collection number |
|---|---|---|---|
| Late/Upper Valanginian | United Kingdom (England) | Compsemys bakewelli (123856) Trionyx bakewelli (type locality: 52258) | |
| Valanginian | United Kingdom (England) | Tretosternum sp. (123855) |