Restoring the skull of the basal bat, Onychonycteris

Short one today,
more ‘show’ than ‘tell’ as one picture and a caption pretty much tell the tale.

Figure 1. Onychonycteris is known from an articulated but crushed bottom half of the skull. Uncrushing it and giving it a suitable top half (Myzopoda) provides a restoration with some possibility of resemblance to theo original.

Figure 1. Onychonycteris is known from an articulated but crushed bottom half of the skull. Uncrushing it and giving it a suitable top half (Myzopoda) provides a restoration with some possibility of resemblance to theo original. Images from Simmons et al. 2010. The skull could have been less crushed than imagined here, so may have been proportionately shorter. The hole in the braincase of Myzopoda (above) may be a surgical opening to remove brain tissue. If natural, I do not know what it is.

And a cladogram
for phylogenetic context (Fig. 2).

Figure 1. Subset of the LRT focusing on the resurrected clade Volitantia, including dermopterans, pangolins, bats and their extinct kin.

Figure 2. Subset of the LRT focusing on the resurrected clade Volitantia, including dermopterans, pangolins, bats and their extinct kin.

Onychonycteris finneyi (Simmons, Seymour, Habersetze and Gunnell 2008) Eocene (~52mya), ~27 cm in length, is the most primitive known bat. It retained unguals (claws) on all five digits, a primitive trait not shared with other bats. Derived from a sister to ChriacusOnychonycteris phylogenetically preceded IcaronycterisMyotis and Pteropus in the LRT (subset Fig. 2).

Figure 2. Chriacus and Onychonycteris nest as a sister to the undiscovered bat ancestor and a basal bat. Miniaturization was part of the transition. So was enlargement of the manus. It is still a mystery why the transitional form decided to start flapping.

Figure 3. Chriacus and Onychonycteris nest as a sister to the undiscovered bat ancestor and a basal bat. Miniaturization was part of the transition. So was enlargement of the manus. It is still a mystery why the transitional form decided to start flapping.

Onychonycteris is smaller than Chriacus,
but the preserved portions of the skull and teeth are similar in proportion and morphology (Fig. 3). So… perhaps the proportions of the missing portion of the Chriacus skull are similar (fig. 1). More fossils will tell.

Veselka et al. 2010
concluded that O. finneyi may have been capable of echolocation.

By contrast, Simmons et al. 2010
argued that O. finneyi was probably not an echolocating bat.


References
Simmon NB, Seymour KL, Habersetzer J, Gunnell GF 2008. Primitive Early Eocene bat from Wyoming and the evolution of flight and echolocation. Nature 451 (7180): 818–21. doi:10.1038/nature06549. PMID 18270539.
Simmons NB, Seymour KL, Habersetzer J and Gunnell GF 2010. Inferring echolation in ancient bats. Nature 466: E8.
Veselka et al. (8 co-authors) 2010. A bony connection signals larygenal echolocation in bats.Nature 463: 939–942.

wiki/Onychonycteris

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