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Fwd: Re: silly questions 2
>Hey, so I go away for a week and all the good questions start flying.
> 1> If feathers were present in archosaurs, did the development of fur and
>hair(not the same thing, as I understand it) occur in the same age as the
>development of feathers, or did one predate the other? If one came first,
>what was the span of time between our first representatives of true hair(or
>fur) and our first representives of true feathers?
Since neither fur nor feathers fossilize well, its difficult to say.
However, many of the advanced Late Permian and Early Triassic therapsids
("mammal-like reptiles") show evidence of whiskers, and thus perhaps fur.
Except for a few people out there, most suspect the evolution of
proto-feathers to have occurred after the split between the crurotarsian
(crocodiles and their relatives) and ornithodiran (dinosaurs and
pterosaurs) archosaurs, so probably not until the Early Triassic.
>2> for the FAQ thing.I have seen pictures of ichthyosaurs where they have
>been found giving birth to a fairly well developed baby. I know whales will
>give early births when killed by whalers. Are ichthyosaurs like whales? did
>they breathe air?
Yes, they most certainly did.
>What thecodont group developed into ichthyosaurs?
None. Ichthyosaurs most likely developed among the lepidosauromorphs (a
groups which today contains lizards, snakes, and the tuatara).
"Thecodonts" is a term used for archosaurs, which are not
>believe cetaceons developed from a bovine-type ancestor, were there
>similarities to their development in ichthyosaurs?
UGH! The Creationist hand at work. NO ONE but some mocking creationists
have suggested a "bovine" ancestor for whales. The ancestors of whales
were mesonychids, a group of omnivores also related to the ancestors of the
ungulates (the hoofed mammals). There are probably some similarities in
their evolution, mainly fully terrestrial animals developing better
swimming adaptations in order to get fish.
>3>what thecodont group developed into pterasaurs? was this of the group that
>had hair(or fur), or did the pterasaurs ever develope any body coverings on
Pterosaurian "fur" has been reported. It is probably similar to mammalian
fur in structure, but probably developed from scales (which hair did not
do, being a different tissue embryologically).
>4>on the conventialities of nomenclature...I went to the Museum at Blackhawk,
>in Danville. and they have a small museum on the mammal finds in the area.
> This is where I found out that Eohippus isn"t Eophippus anymore.
The rules are the same for all animals, mammals or dinosaurs, vertebrate or
invertebrate, living or extinct. In this case, the name Hyracotherium had
been around for years before Eohippus, and was a well known name, so it has
priority. Like Brontosaurus, the name Eohippus was perpetuated by some
prominent American museums and books written by people working at or
visiting the musuem.
>done by the same Commitee that does dinosaur nomenclature? does the renaming
>of Eohippus make sense to anybody? what is it called now? For that matter,
>Centrasaurus is now called Eocentrasaurus. What caused the name change here?
> Hugs and kisses
The Eucentrosaurus (true horned lizard, not dawn horned lizard) name was
suggested just in case the name Centrosaurus was considered occupied.
However, the older name Centrosaurus had not been used (outside of a list
of names) for five decades before the dinosaur was named, so the change is
probably not required.
Thomas R. Holtz, Jr.
Vertebrate Paleontologist in Exile
U.S. Geological Survey
Branch of Paleontology & Stratigraphy
MS 970 National Center
Reston, VA 22092