Wednesday, January 6, 2010

Tetrapods: 400ma coral lagoon ancestors

Tetrapod tracks
"Another key surprise from the research is the recognition that these tetrapods lived in a marine environment, perhaps a coral lagoon. The favoured origin before now for the emergence of tetrapods had been marshy environments, such as deltas or lakes where freshwater dominated. The team behind the latest research said the new explanation made sense because it would have allowed marine ancestors of tetrapods gradually to acquire terrestrial competence while accessing a new and essentially untouched resource of food washed up with the tides.

"In the intertidal setting, you've got a smorgasbord laid out twice a day," said Dr Ahlberg. "Every time the tide goes out, it leaves behind this drift-line of dead and moribund animals. All this was just left there for vertebrates - our ancestors - to emerge on to land and pick them off."
Cape clawless otter vs cape clawed toad?
Definition of Toads versus Frogs from the " Encyclopedia of Animals A complete Visual Guide"
Univ of Cal Press ISBN 0-520-24406-0
Toads family ( Bufonidae) have short legs for hopping, dry warty skin and are terrestrial. Frogs( Family Ranidae) have long, slender legs for leaping great distances, moist skin, and are aquatic. The use of the term "Toad" depends on the region of the world you are in. in Africa, the smooth and moist- skinned aquatic Cape clawed frog ( Xenopus gilli) is called a clawed Toad."

Sea otter: note similarity to human backfloating with arms behind head
sea otter

Swimming sloths: aqua-arboreal sloths

Size of eyes, Snake eyes
"The habits of Snakes can be seen in their eyes: small degenerate eyes suggest burrowers, vertical elliptical pupils are nocturnal/[crepuscular] species, large round eyes are active diurnal/[crepuscular?] predators that chase down their prey"
Posted by: Bob Michaels at Tet zoo

Neandertal eyes vs sapien eyes

Neandertal orbits were larger than modern human orbits, is this due to more nocturnal activity, as parallel in new world tarsier-like nocturnal owl monkeys vs other new world monkeys? Did neandertals specialize in crepuscular (early morning/late evening) ambushes at waterside? Was dark adaptation an aquatic feature, as seen in seals and sea lions with large orbits? See page 15 of this pdf:
them and us article

Perhaps erectines were more shellfish gatherers (dive partners at tropical lagoons) and only opportunistic hunters/scavengers, neandertals were more waterside ambushers (groups with jabbing spears in cooler climates) and sapiens were high-tech fishermen and trappers (including herding into traps/canyons).

Did neandertals have slit pupil eyes, like cats and some nocturnal primates (galagos, owl monkey)? The large orbit and occipital bun might indicate that. Note that aquatic animals do not have slit eyes, despite their dark hunting environment, since the refractive value of light in water differs from air.

Did neandertals retain a fur coat, growing longer in winter and shedding in spring, as in other paleoarctic fauna? Did only erectines lose this fur, due to basking on tropical shorelines? Did sapiens develop clothes and animal furs only as they moved away from the tropics, or in addition/substitution to body paints/perfumes for insect repellants?

Convergent evolution of echolocation in bats and whales
high freq hearing

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