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Re: Two questions on the dino-fleas



On 3/12/2012 12:03 AM, Tim Williams wrote:

Martin Baeker<martin.baeker@tu-bs.de>  wrote:

1. It is stated that "feathered dinosaurs became well-known from this
period" - but only two references are given, one relating to the
cretaceous, the other being the paper where Epidexipteryx is
described. However, Epidexipteryx seems a bit small to host a
2cm-flea. So what are the supposed hosts during the jurassic? Are
there any known fuzzy dinos from that period? Pterosaurs perhaps? Or
do these fleas hint at the existence of large feathered dinos we don't
know about?

Using phylogenetic bracketing, we could infer that a large chunk of
the Theropoda included forms that had some form of filamentous
integumentary
covering.  For example, the 1.6-to-2 m long tyrannosauroid _Dilong_
had 'protofeathers' - albeit larger and more derived tyrannosauroids
may not have had an extensive (if any) covering of these structures.

1) a 2 cm flea would not likely last long on a dog; those that busy incisors did not destroy in hedge-clipper fashion, vigorous cycling of the claws on the hind leg would.

2) a short proboscis in a proto-flea would limit exploitation of animals with thick hides.

3) large herbivorous dinos might provide a scorpionfly equipped with a long proboscis a relatively safe and incremental transition from plant-based fluids to animal blood -- even excluding the likely dino-sweat, the area around the presumed cloaca would provide fluids originally derived from plants, mixed with fluids of animal origin.

The idea that fleas got their start on large dinosaurs, and were initially relatively large, seems very logical.

What I do not quite understand is the unstated presumption that "filamentous body coverings" would be advantageous or necessary to proto-fleas -- I would speculate that thick dino-fuzz might difficult for a 2 cm flea to navigate, whereas the wrinkles, cracks and crevices of basal dinosaurs would provide a suitable, if sometimes disgusting, habitat in the _absence_ of a dense covering.

Isn't it more reasonable to speculate that an early advantage of dense dinofuzz was that it impeded exploitation of dinos by giant fleas by 1) making the skin difficult to access, 2) enhancing the host's ability to sense moving parasites 3) generally impeding mobility, and 4) (possibly) even clogging spiracles with 'feather-dust'?

And further, that fleas became smaller, and started jumping, as an adaptive response to dense body-coverings?