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Features of the dorsal-fin spine of Chrysichthys auratus collected from Lake Nasser, Egypt
| Characters | 100 – 200 mm TL, n = 10 | 201 – 300 mm TL, n = 10 | 301 – 400 mm TL, n = 10 |
|---|---|---|---|
| Median foramen, shape and size | Small, rounded, with no edges | Large, rounded, with high edges | Large, oval, with high edges |
| Shape of the articular head | Triangular in shape. The middle part is narrow and levelled with the wings, which are separated from the middle part by shallow grooves | Triangular in shape, with middle part is levelled with the wings. No grooves | Triangular in shape. Broad middle part, with edges and deep grooves separating it from the wings. The middle part is higher than the wings |
| Presence or absence of striations on the lateral sides of the spine, their shape and size | No striations are present on the sides of the spine | Deep striations present towards the posterior edge of the spine and shallow anteriorly. Diminish towards the tip of the spine. | |
| Ornamentations on crest | Smooth, no ornamentations | Mainly smooth, with slight irregularities in the surface near the head | Presence of a few tubercles irregularly arranged near the articular head and smooth on the remaining surface of the crest. They are variable in size. |
| Ratio of width of the articular head/width of the spine at its base | 1.46 | 2.0 | 1.74 |
| Ratio of the width of the median foramen/ width of the articular head | 0.15 | 0.13 | 0.14 |
| Average angle made by the lateral border of each wing of the articular head with the corresponding lateral border in ventral view | 119° | 101.5° | 109° |
| Posterior surface of the median crest | No grooves. Tubercles are small | Presence of shallow grooves and tubercles getting larger towards the tip of the spine | Presence of deep grooves, tubercles getting larger towards the tip of the spine |
| Posterior blocking processes | Poorly developed directed posteriorly | Well-developed, pointed directed laterally | Broad, well-developed, posteriorly directed. |
Features of the dorsal-fin spine of Synodontis schall collected from Lake Nasser, Egypt
| Characters | 200 – 250 mm TL, n = 10 | 251 – 300 mm TL, n = 10 | 301 – 350 mm TL, n = 10 | 351 – 400 mm TL, n = 10 |
|---|---|---|---|---|
| Median foramen, shape and size | Small, rounded, with high edges at dorsal side | Large, elongated dorsal ventrally, with ridges at the dorsal side | Small, rounded, with low edges | Large, rounded, with high edges |
| Shape of the articular head | Triangular in shape. The middle part broad and wider than the wings. Rounded edged wings, with notch at their lateral base | Triangular in shape. The middle part with rounded edges and shorter than the wings. The left wing with triangular left head and rounded right head. | Triangular in shape. The middle part broad. The wings with rounded edges. Presence of deep groove separating middle part and the wings. | Triangular in shape. The middle part broad levelled with wings. Presence of a deep groove separating wings and the middle part. |
| Presence or absence of striations on the lateral sides of the spine, their shape and size | Presence of a shallow striations diminish towards the tip of the spine | Presence of a deep striations at the lateral sides decrease in number towards the tip of the spine. | Presence of a deep curved striations decrease in number towards the tip of the spine. | |
| Ornamentations on crest | Presence of a small sized tubercles confined to the anterior base of the spine | Smooth, with longitudinal keel traversing over the length of the spine | Smooth, with slight irregularities near the articular head. | Irregular surface, with no tubercles. |
| Ratio of width of the articular head/width of the spine at its base | 1.7 | 1.14 | 1.9 | 2.3 |
| Ratio of the width of the median foramen/width of the articular head | 0.1 | 0.08 | 0.29 | 0.27 |
| Average angle made by the lateral border of each wing of the articular head with the corresponding lateral border in ventral view | 134° | 122° | 127.5° | 138° |
| Posterior surface of the median crest | Presence of a shallow groove, with curved dentations getting larger towards the tip of the spine | Presence of a deep groove, with long and curved dentations getting longer towards the tip of the spine. Regularly spaced. | Presence of a deep groove, with large and dentations curved downward. Large dentations located near the tip of the spine. | |
| Posterior blocking processes | Broad, not produced directed posteriorly | Broad, not produced, with wavy edge directed posteriorly. | Broad, not produced and directed posteriorly. | |
Features of the dorsal-fin spine of Synodontis serratus collected from Lake Nasser, Egypt
| Characters | 200 – 400 mm TL, n = 10 | 401 – 600 mm TL, n = 10 |
|---|---|---|
| Median foramen, shape and size | Small, rounded, with dorsal edge | Large, rounded, with course ridges dorsally |
| Shape of the articular head | Triangular in shape, with the middle part has rounded lower edge, higher than the wings which have rounded edges and well-separated from the middle part. | Triangular in shape, with middle part broad, rounded and larger than wings. Rounded wings, well-separated from the middle part |
| Presence or absence of striations on the lateral sides of the spine, their shape and size | Presence of a shallow striations traversing over most of the length of the spine and diminish towards the tip. | Deep and irregular striations diminish towards the tip of the spine |
| Ornamentations on crest | Presence of an irregular ridges along the length of the crest | Presence of an irregular dentations getting larger towards the tip of the spine and irregularly separated |
| Ratio of width of the articular head/width of the spine at its base | 1.82 | 2.65 |
| Ratio of the width of the median foramen/width of the articular head | 0.15 | 0.05 |
| Average angle made by the lateral border of each wing of the articular head with the corresponding lateral border in ventral view | 114° | 137.7° |
| Posterior surface of the median crest | Presence of an irregular pores along the length of the median crest. | Presence of curved down dentations getting larger towards the tip of the spine |
| Posterior blocking processes | Well-developed, broad, with curved posterior edge directed posteriorly | Well-developed, with straight edge directed posteriorly |