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Re: [dinosaur] Versperopterylus, new anurognathid from Cretaceous of China, with evidence of perching behavior
Ben Creisler <firstname.lastname@example.org> wrote:
> A new paper:
> Versperopterylus lamadongensis gen. et sp. nov.
> Junchang Lü, Qingjin Meng, Baopeng Wang, Di Liu, Caizhi Shen and Yuguang
> Zhang (2017)
> Short note on a new anurognathid pterosaur with evidence of perching
> behaviour from Jianchang of Liaoning Province, China.
> Geological Society, London, Special Publication SP455: New Perspectives on
> Pterosaur Palaeobiology (advance online publication)
Honestly, where to begin.
First, the name _Versperopterylus_. It sucks. It's a real dog's
breakfast of a name. The authors' etymology for _Versperopterylus_ is:
"Versper - Latin word for 'dusk' implying that the new pterosaur may
seek food at dusk; -pteryl, Latin word for 'wing'." Both parts of the
name look wrong to me. I think the first part of the name is supposed
to be _vesper_, not _versper_ (probably a misspelling). And strictly
speaking, _vesper_ doesn't actually mean 'dusk' in Latin - it means
'evening' (it also means 'evening star' and 'west', being cognate with
the ancient Greek _hesperos_). I don't know where on earth they got
'pterylus' from - it's not Latin for 'wing'. 'Pterylus' recalls
pteryla, the tracts of skin where feathers are arranged in birds; the
word pteryla is formed from two Greek words (_pteron_ feather + _hula_
forest); but there's no connection between pteryla and the genus name.
Is 'pterylus' intended to be a contraction of 'pterodactylus'?
Interesting, in the Supplementary materials the genus is called
'Versperopterus', which is slightly less atrocious.
Enough with the crap name... on to the description of the beastie
itself. The study claims that _Versperopterylus_ had a reversed first
toe, and was therefore an arboreal percher. I'd charitably
characterize the evidence as flimsy. The interpretation of a reversed
first toe is based on the preserved orientation of the pedal digits in
the _Versperopterylus_ specimen: "The tips of the pedal unguals of
digits II, III and IV are pointed in the same direction, whilst the
tip of the first toe is pointed in the opposite direction in both
pedes; thus, it is inferred that the first toe is reversed."
Historically, the same assumption was once applied to specimens of
many fossil theropods, incuding _Archaeopteryx_, which were thought to
show a "reversed" first toe based on the preserved orientation. In
the London specimen of _Archaeopteryx_, for example, the tip of first
toe (hallux) is preserved facing in the opposite direction to the tips
of the other three toes, leading to the reconstruction of a grasping
foot with an opposable first toe. But as many studies have noted
(e.g., Mayr et al. 2007 DOI: 10.1111/j.1096-3642.2006.00245.x), the
"reversed" first toe in this (and other) specimens is likely to be an
artifact of preservation. Retroversion of the hallux in birds is
actually quite a complex business, entailing modification of the
articulation of metatarsal I on the tarsometatarsus, plus (more
critically) twisting or bending of the shaft of metatarsal I.
Metatarsal I cannot simply be shifted to the back of the
tarsometatarsus, due to the passage of the flexor tendons along the
posterior (caudal) surface of the tarsometatarsus. A similar
constraint might have occurred in pterosaur anatomy; so if
_Versperopterylus_ did have a truly reversed toe, the articulation
and/or shape of metatarsal I might be expected to be highly modified.
Simply arguing that the first toe is reversed based on how it's
preserved in a fossil specimen is insufficient evidence by itself.
It wouldn't be at all surprising that a pterosaur like
_Versperopterylus_ was arboreal, spending part of its life in trees.
But it didn't need to perch - it could hang bat-like upside down from
branches, as depicted in Fig. 5 (although here the first toe is shown
opposable to the middle three toes, grasping a branch in anisodactyl,
bird-like fashion). The tiny (juvenile?) pterosaur _Nemicolopterus_
has been described as arboreal, based on the curved and elongated
penultimate pedal phalanges (Wang et al., 2008 doi:
10.1073/pnas.0707728105), but there's no evidence of anisodactyl
perching adaptations. [I know that D.Peters has argued that pterosaurs
had a perching foot, with digit V (yep, the clawless fifth toe,
believe it or not) supposedly opposing the other digits... but the
less said about this the better.]