[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
>Aren't tetrapods sarcopterygians?
>Wouldn't "Choanata" be the same as Sarcopterygii?
Uuuhhhhh, no. Sarcopterygii contains some fish without a true choana
such as coelacanths and lungfish. It should be noted, though, that in
1981 Don Rosen and collegues (one of whom was Brian Gardiner) argued
that lungfish primitively had a true choana and were the closest group
to tetrapods rather than osteolepoformes and relatives. Anyway, I think
that some still hold to the dipnoan+tetrapod arrangement rather than the
better-supported panderichthyid+tetrapod arrangement (panderichthyids
show a true choana, but this was disputed by Rosen's group in 1991).
Another note should be made. Chan Mee-Mann (sp?) has argued that
tetrapods form a sister-group to the groups that typically form the
choanates as well the lungfish. She argues that the only creatures with
a true choana are tetrapods and not any other group. She also proposes
a dipnoan+porolepoformes relationship, placing dipnoans deep within the
animals typically called choanates.
My personal opinion is that panderichthyids are the sister-group to
tetrapods and they (and their relatives) did show a choana. As for the
dipnoan-tetrapod link? I like the correlation and I wish there was more
evidence for it, but unfortunately there is not. (However, Forey, one
of the original Rosen et al. authors, argued that panderichthyids
bridege the gap between dipnoans and tetrapods. I don't buy it, but it
Get Your Private, Free Email at http://www.hotmail.com