Friday, July 3, 2009
Aquatic frog of the Congo
The African dwarf frog, a member of the Pipidae, is an aquatic animal living its life entirely underwater, but needs to rise to the surface to breathe atmospheric air because they have lungs and not gills. They "breathe" water in through their skin. They are fairly small in size and don’t weigh more than a few ounces. (Wikipedia)
They produce vocal clicks and trills, rather than the more typical croaks of more terrestrial/arboreal frogs, due to a lack of long extensible tongue and throat sac.
Jamaican tree frog lacks vocal sac yet vocalizes
"Hyla marianae lacks a vocal sac" yet calls during mating season in arboreal wet bromeliads.
Treefrog without throat sac
So we see a precise parallel regarding water & foraging:
benthic foraging frogs & humans lack throat sac, lack tail
surface foraging frogs & large apes have throat sac, lack tail
arboreal foraging frogs & canopy gibbons lack throat sac, lack tail
benthic foraging salamanders & monkeys lack throat sac, have tail
arboreal foraging salamanders & *monkeys lack throat sac, have tail
*atellid howler monkey.
all wading/swimming/diving monkeys have medium or long tails.
Clicking for echolocation by dolphins and humans
Frog hydrodynamic streamlining:
Not linear in their resting position, no, but well streamlined and linear at
times when leaping and swimming.
The frogs legs can spread wide, then clap together while pushing against the water.
Some frogs/toads walk or gallop briefly rather than hop. Many treefrogs mostly climb on 4 limbs, boreal toads tend to walk more than hop on the ground. The natterjack ground gallops briefly on all four, and burrows into drying salt-mires with forelimbs initially and then rear limbs.
This parallels primates/hominoids again, the change from ancestral long-tail locomotion (monkeys/salamanders) to non-tail hydrostatic foraging results in modified locomotion (leaping/swinging) which in some species returns to near-ancestral qpal locomotion in some species (natterjack/knucklewalking apes). The only missing parallel remaining is the possible frog which developed bipedal gait, so far not found in nature. Possibly long-tailed proto-archosaurs (ancestors of crocs, T rex, birds) developed from a coastal arboreal salamandrid, which in the avian line lost the long tail after branch vertical perching and reversed toe evolved.