Mid-Pliocene bald ibis (Geronticus cf. calvus; Aves: Threskiornithidae) from the Cradle of Humankind, Gauteng, South Africa and its environmental and evolutionary implications
We document the presence of the bald ibis genus Geronticus Wagler, 1832 (Aves: Threskiornithidae) from the mid-Pliocene (ca. 3–3.5 Ma) of South Africa based on an incomplete skull from the Bolt’s Farm Cave System (Cradle of Humankind, Gauteng, South Africa). The fossil cranium is distinct on morphom...
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Veröffentlicht in: | Paläontologische Zeitschrift 2017-06, Vol.91 (2), p.237-243 |
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Sprache: | eng |
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Zusammenfassung: | We document the presence of the bald ibis genus
Geronticus
Wagler,
1832
(Aves: Threskiornithidae) from the mid-Pliocene (ca. 3–3.5 Ma) of South Africa based on an incomplete skull from the Bolt’s Farm Cave System (Cradle of Humankind, Gauteng, South Africa). The fossil cranium is distinct on morphometric and structural grounds from
Geronticus apelex
, the only other Pliocene
Geronticus
described from Southern Africa, but is very close in dimensions and general morphology to the extant
G. calvus
of South Africa, and the Bolt’s Farm fossil ibis is therefore attributed to
G.
cf.
calvus
. Modern
Geronticus
ibises are localised to temperate, open grasslands and semi-arid steppe, and nest exclusively on cliffs and similar rocky eminences. Given its attribution as
G.
cf.
calvus
, the Bolt’s Farm ibis was likely similar in ecology to the extant
G. calvus
, suggesting that the habitat surrounding the Bolt’s Farm fossil site during the mid-Pliocene featured open grassland and presence of cliffs. This record constrains the divergence between
G. calvus
and its putative ancestor
G. apelex
to the mid-Pliocene and implies that
G. calvus
has possibly been subject to “evolutionary/morphological stasis” for more than 3 million years. This postulated stasis would be consistent with the notion that extant genera with few species (i.e. high genus-to-species ratios) show low rates of phenotypic diversification and change through the Neogene. |
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ISSN: | 0031-0220 1867-6812 |
DOI: | 10.1007/s12542-017-0346-8 |