Prolibythea vagabunda

Jong, Rienk De, 2017, Fossil butterflies, calibration points and the molecular clock (Lepidoptera: Papilionoidea), Zootaxa 4270 (1), pp. 1-63 : 41

vagabunda . Prolibythea vagabunda Scudder, 1889

Nymphalidae , Libytheinae (based on similarity rather than on apomorphy).

USA, Colorado , Teller County, Florissant; late Priabonian, late Eocene.

Depository: MCZH (holotype, no. 16353).

Published figures Scudder (1889: Pl. LIII Figs. 4 –9); Emmel et al. (1992: Fig. 1 /43); Murata (1998: Figs 44, 45); Kawahara (2013: Fig. 63).

The rather poorly preserved specimen shares at least one apomorphic character with Nymphalidae , tricarinate antennae. The very long palps are shared with the Libytheinae , but are also found in some other nymphalids (see above under Barbarothea florissanti ). The relatively broad abdomen suggests a female, also indicated by the foreleg bearing complete tarsal claws. The latter is a plesiomorphic character, but in the Nymphalidae found only in Libytheinae , a feature in agreement with palpal characters. As far as visible the venation shows plesiomorphic characters, with a radial vein formula 1, 2, 3+(4+5), but large segments of the veins cannot be made out. Hindwing costa apically extended as in recent Libythea celtis (Fuessly) . Apomorphic character states unique for the Libytheinae are not visible in the fossil, so its assignment to the Libytheinae , in agreement with Emmel et al. (1992), must be based on similarity only. Scudder emphasized that the fossil is more similar to Old World than to New World Libytheinae . Kawahara (2009, 2013) discussed the fossil at length. On the basis of a phylogenetic analysis of all taxa of Libytheinae , fossil and recent, he placed the fossil in the extant genus Libytheana , together with another fossil from the same fossil bed, Barbarothea florissanti (= Oligodonta florissantensis ) (see comments under these names.). The difference between Libytheana vagabunda and L. florissanti is that in the latter the forewing apex is less strongly falcate. Indeed, the relatively strong falcation in L. vagabunda is not an observation, but Scudder's reconstruction, indicated by a dashed line. The insects were fossilized ca 34 Ma in a lake environment. The area has been suitable for fossilization of butterflies for a long period, a million to several million years ( Smith et al. 2008). Consequently, Libytheana vagabunda and L. florissanti may have fossilized at times separated long enough for differences to evolve, possibly even at species level.

L. vagabunda as well as L. florissanti were used as calibration point for the molecular clock of the Nymphalidae by Wahlberg et al. (2009), the first also employed by Misof et al. (2014) in their paper on insect evolution for calibrating Macrolepidoptera. See also the section on Fossils and calibrating the molecular clock.

Figures

FIGURE 1. Localities of fossil butterflies plotted ion a modern map. See Table 1 for further, complementary information.

FIGURES 3 – 4. Wing venation of (A) Pareronia Bingham, 1907 (Pieridae), and (B) Hasora Moore, 1881 (Hesperiidae). See text for explanation.