[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Re: "Feathery fossil shows birds aren't dinosaurs"
>Now, if the earliest archosaurs include small, arboreal or acronomic forms,
>and modern birds include small, arboreal and acronomic forms, what do we
>large, cursorial, ground-dwelling dinosaurs for?
That is like arguing that mosasaurs and other marine reptiles must have
always been aquatic. After all, if the earliest tetrapods were aquatic, and
mosasaurs were aquatic, what do we need terrestrial lizard intermediaries
for? Clearly all terrestrial squamates must have descended from aquatic
forms, with iguanas, anoles, and gekkos descending from iguana-like,
anole-like and gekko-like marine lizards that just haven't turned up in the
fossil record yet.
If you look at most archosaur cladograms, you have Euparkeria and
erythrosuchids as consecutive outgroups near the base, with ornithosuchians,
rauisuhians, and crocodylomorphs coming out in the Pseudosuchia. The
implication is that the carnivorous big headed, long-bodied, short legged
and VERY short fingered design is the plesiomorphic ancestral strain of of
archosaurs being largely retained in these groups, remaining the ancestral
strain into Pseudosuchia. That would also imply that that this design was
not lost in the dinosaur-bird lineage until after Ornithosuchia/Ornithodira
split with Pseudosuchia. If the arboreal lifestyle of birds goes all the
way back to early archosaurs, then you have to have something built like
Euparkeria as your arboreal ancestor, climbing around in trees and
itermittantly tossing off the larger bodied cursorial forms (like your
dinobirds tossing off big theropods), and waiting until the split with
Pseudosuchia before developing the bipedal and long-fingered design you
claim was more better specialized for an arboreal lifestyle. Where do
Longisquama and Cosesaurus fit into that?
>BCF meets the big problem the ornithologists have with cladistics head on:
>birds are dinosaur descendants, why are all the most birdlike dinosaurs in
>the fossil record >after< Archaeopteryx? The answer is that these are
>ground-dwelling, flightless maniraptorans, just as ostriches are
>ground-dwelling paleognath birds. There is no conflict or contradiction
>between BCF and the fossil record.
If all the most birdlike theropods being known after Archaeopteryx
means that they couldn't have been its ancestor, then BCF is every bit as
flawed. Where are the fossils of the middle-late Jurassic dinobirds that
immediately proceeded Archaeopteryx? If the birdlike theropods don't show
up in the fossil record till later, the dinobirds haven't shown up at all!
At the very least, even if things like Longisquama and Cosesaurus do
represent early relatives or members of the dino-bird lineage, there is a
stratagraphic gap between them and Archaeopteryx no smaller then the one
between Cretaceous birdlike theropods and Archaeopteryx. You either have to
hypothesize a few tens of millions of years of missing fossils before the
known Cretaceous theropods or a few tens of millions of years after
Longisquama. As far as the fossil record is concerned, BCF has no edge at
all. Something has to have been around longer then its known fossil record
implies, or Archaeopteryx evolved from nothing.
You have to study a great deal to know a little.
-Baron de Montesquieu
They may forget what you said, but they will never forget the way you made
-Carl W. Buehner
Jeffrey W. Martz
3002 4th St. #C26