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Re: New review of bird origins and evolution in Naturwissenschaften

Ben Creisler wrote-

> Zhonghe Zhou. The origin and early evolution of birds:
> discoveries, disputes, and perspectives from fossil
> evidence.
> Naturwissenschaften online publication Sept. 8, 2004.

Where are the reviewers?

"All known enantiornithines appear to be perching forms, as indicated by
their large and curved pedal claws and toe proportions adapted to an
arboreal life."
What about Longirostravis (which is mentioned shortly afterward),
Yungavolucris, Lectavis and possibly Halimornis?

"These forms include the Spanish birds Concornis (Sanz and Buscalioni 1992;
Sanz et al. 1995), Iberomesornis (Sanz and Bonaparte 1992; Sereno 2000), and
Neuquenornis (Chiappe and Lacasa-Ruiz 2002)."
That last is a typo for Noguerornis.

Pygostylia is incorrectly placed as a clade including Jeholornis, Sapeornis,
confuciusornithids and more derived birds.  The definition is
(Confuciusornis + modern birds) (Chiappe, 2001) or (fused distal caudal
vertebrae homologous with Vultur gryphus) (Gauthier and de Qeiroz, 2001).
So Pygostylia should be either the Sapeornis+ node or the
Confuciusornithidae+ node on his cladogram.

"Since several other enantiornithine birds (e.g., Eoalulavis and
Eoenantiornis: Sanz et al. 1996; Hou et al. 1999a) also possess an alula, it
is most likely that this advanced flight feature appeared at the origin of
the Enantiornithes."
Or more parsimoniously, at the origin of Ornithothoraces.

Apsaravis is placed as a carinate, contra the more recent study by Clarke
and Norell (2002) (not in the bibliography).

"... none of the Cretaceous ornithurines can be regarded as crown group
Ignoring Hope (2002), and references within, though it is in the

"Confuciusornis is the oldest bird known to possess a horny beak..."
Should be tied with Jixiangornis and Changchengornis.

"Several species of Confuciusornis have been described (Hou 1997)."
.. but later synonymized into C. sanctus by Chiappe et al. (1999).

"Confuciusornis has a fully opposable foot, as in Archaeopteryx, ..."
The latter has been disputed by Middleton (2003), and even Confuciusornis'
hallux was only medially directed.

"As will be explained below, all known long-tailed birds have a relatively
advanced wing, albeit not necessarily as advanced as in an ornithurine
Even archaeopterygids?

"The elongated prezygopophyses and chevrons of the caudal vertebrae bear a
close resemblance to those of dromaeosaurs, confirming a close link between
birds and this lineage of non-avian theropod dinosaurs."
The prezygopophyses are no more elongated than in 'typical' tetanurines
(e.g. Allosaurus, ornithomimids) and the chevrons are far shorter than
dromaeosaurs' as well, resembling those of troodontids (Currie and Dong,
2001) more.

"As discussed above, one of the more contentious issues raised by the study
of the feathered dinosaurs and their close relatives is that some of them
(e.g., oviraptorosaurids and dromaeosaurids) have been proposed to be
flightless birds."
This is discussed below, not above.

"A recent report of possible Triassic avian footprints merits attention, as
the tracks show a clearly preserved hallux, which is currently known only in
birds (Melchor et al. 2002). "
A clearly preserved REVERSED hallux, perhaps.

"The holotype of Vorona was represented only by hindlimbs; however, Vorona
is clearly a much more advanced bird, probably an enantiornithine (Feduccia
1999a), and it is distinctively different from Rahonavis."
Uh.. no.  Vorona is an ornithuromorph (by definition, even) (Chiappe, 2002).

"Many paleontologists are tempted to declare the end of the debate on the
origin of birds (Prum 2002), stating that birds are dinosaurs just as humans
are mammals. On the other hand, there is still disagreement. For instance,
Alan Feduccia, who is one of the strongest opponents of the dinosaurian
origin of birds, added a new chapter to his book (Feduccia 1999a) entitled
T. rex was no four-ton roadrunner and other revelations. It is clear that
the debate is not over (Feduccia 2002; Galis et al. 2003)."
I don't know.  I have yet to see a rebuttal from Feduccia, Hou, et al. in
response to Prum's assertions their arguments aren't scientific.  And Galis
et al. (2003) support a theropod origin of birds.

"Since 1996, a total of eight species of feathered dinosaurs have been
reported from the lacustrine Early Cretaceous deposits of Liaoning
Also Yixianosaurus longimanus (Xu and Wang, 2003), Cryptovolans pauli
(Czerkas et al., 2002), Scansoriopteryx heilmanni (Czerkas and Yuan, 2002)
and Epidendrosaurus ningchengensis (Zhang et al., 2002).

"... Protarchaeopteryx is not known but is thought to lie among
Coelurosaurians or coelurosaurs, or more precisely, maniraptorans.
"... present in many oviraptorosaurids ..."
Oviraptorosaurians or oviraptorosaurs.  The same mistake for both clade
names is made several other times in the paper.

"including uncinate processes on the ribs in dromaeosaurids (Clark et al.
1999; Xu et al. 2003), oviraptorosaurids (Caudipteryx and oviraptorids)
(Zhou and Wang 2000; Zhou et al. 2000; Lü 2002), and therizinosaurs,"
What's the therizinosaur reference, I wonder.

In the "List of some most remarkable bird features in theropod dinosaurs", I
would add-
Furcula (wishbone)- coelophysids, spinosaurids, allosaurids, tyrannosaurids,
compsognathids, therizinosaurs.
Retroverted pubis- alvarezsaurids, therizinosaurs.
Nesting behavior- troodontids.

"Although most of the bird-related theropod dinosaurs are known from the
Late Cretaceous, there are some earlier records. For instance, a non-avian
maniraptoran fossil was reported from the Late Jurassic Morrison Formation
in the USA (Jensen and Padian 1989) and dromaeosaurs from the Jurassic in
Europe (P. Barrett, personal communication)."
There are also more convincing records- Koparion (Chure, 1994), the
Guimarota troodontids and dromaeosaurs (Zinke, 1998; Rauhut, 2000), Morrison
dromaeosaurs (Britt, 1991); in addition to undescribed Morrison (Chure et
al., 1993; Turner and Patterson, 1999), Ethiopian (Goodwin et al., 1999) and
Russian (Novikov et al., 1998) Jurassic dromaeosaurs.

"It should be noted that the hallux is reversed in all known basal birds but
it has not been confirmed in any dinosaurs. Therefore, the character of the
opposable hallux of the foot is still one of the few characters unique to
birds. No evidence indicates that this character was developed for any
adaptation other than an arboreal life style."
See Middleton (2002; 2003), who demonstrates the position of halluces in
two-dimensionally preserved fossils like Archaeopteryx is not representative
of their position in life, as shown by the amount of twist in the first
metatarsal.  Archaeopteryx, Rahonavis and Patagopteryx have unreversed
halluces like more basal theropods, while confuciusornithids and most
enantiornithines have an intermediate condition between that and modern
birds.  Avisaurids and hesprornithines have highly specialized conditions.

"Following the recognition of several arboreal theropods, and the arboreal
nature of most basal birds, the large, curved and sharp pedal claws of small
sized dromaeosaurids are probably better explained as arboreal, rather than
predatory, adaptations."
I'd say ",in addition to predatory, adaptations."

"... the partially posteriorly directed hallux, the sharp and strongly
curved pedal unguals, and elongated penultimate phalanges of Microraptor
zhaoianus ..."
There's no evidence for even a partially reversed hallux in Microraptor
zhaoianus (Hwang et al., 2002; Middleton, 2003).

"However, no firm conclusions may be drawn because we do not know whether or
not hindlimb feathers were common in theropod dinosaurs or whether they were
simply a specialization of Microraptor gui."
No mention of Christiansen and Bonde (2004), who show Archaeopteryx has
short leg remiges as well.

"Padian (2001a) insisted that claw shape is not a good indicator of habits
because some large-sized non-avian theropods also have similar features. It
is notable that one of his assumptions is that these large-sized, non-avian
theropods could not climb."
What would Utahraptor or Allosaurus be climbing exactly? ;)

And a few other issues I have with the paper-
- Other specimens being referred to Liaoxiornis, when its supposed
apomorphies are juvenile characters.
- The assignment of Chaoyangia and Liaoningornis to Ornithurae (contra
Clarke, 2002).
- Placement of yanornthids basal to Patagopteryx (contra Clarke, 2002; Clark
et al., 2002).

Mickey Mortimer
Undergraduate, Earth and Space Sciences
University of Washington
The Theropod Database - http://students.washington.edu/eoraptor/Home.html