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RE: pterosaur femora sprawl



David Marjanovic wrote:


> Remember *Onychonycteris*. It seems, to some degree, have used all five 
> fingers.


Yes, exactly.  The paper that David (Marjanovic) is referring to - and which 
David (Peters) really needs to read - is...   


Nancy B. Simmons, Kevin L. Seymour, Jörg Habersetzer, & Gregg F. Gunnell 
(2007).  Primitive Early Eocene bat from Wyoming and the evolution of flight 
and echolocation.  Nature 451: 818-821 


Abstract: "Bats (Chiroptera) represent one of the largest and most diverse 
radiations of mammals, accounting for one-fifth of extant species.  Although 
recent studies unambiguously support bat monophyly and consensus is rapidly 
emerging about evolutionary relationships among extant lineages, the fossil 
record of bats extends over 50 million years, and early evolution of the group 
remains poorly understood.  Here we describe a new bat from the Early Eocene 
Green River Formation of Wyoming, USA, with features that are more primitive 
than seen in any previously known bat.  The evolutionary pathways that led to 
flapping flight and echolocation in bats have been in dispute, and until now 
fossils have been of limited use in documenting transitions involved in this 
marked change in lifestyle.  Phylogenetically informed comparisons of the new 
taxon with other bats and non-flying mammals reveal that critical morphological 
and functional changes evolved incrementally.  Forelimb anatomy
 indicates that the new bat was capable of powered flight like other Eocene 
bats, but ear morphology suggests that it lacked their echolocation abilities, 
supporting a 'flight first' hypothesis for chiropteran evolution.  The shape of 
the wings suggests that an undulating gliding–fluttering flight style may be 
primitive for bats, and the presence of a long calcar indicates that a broad 
tail membrane evolved early in Chiroptera, probably functioning as an 
additional airfoil rather than as a prey-capture device.  Limb proportions and 
retention of claws on all digits indicate that the new bat may have been an 
agile climber that employed quadrupedal locomotion and under-branch hanging 
behaviour."


This paragraph (from the body of the paper) is also helpful...


"The discovery of _Onychonycteris_ indicates that claws on digits III–V were 
lost after powered flight evolved. [snip] Reduction in the relative size of the 
hind limbs also continued after the evolution of powered flight.  The limb 
proportions, the robust fibula and the retention of wing claws seen in 
_Onychonycteris_ suggest that it was probably capable of more agile non-volant 
locomotion (climbing either along tree branches or under them) than most other 
bats, including other Eocene taxa, and may have incorporated quadrupedal 
locomotion and under-branch hanging into its locomotory and roosting behaviour."




Cheers

Tim

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