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PARROTS, HOATZINS & DEINONYCHUS
This year's Palaeontological Association meeting finished last
Friday: twas a great success and enjoyed by all, the meal
especially:) Those of us interested in tetrapods had our own little
bird symposium.. by some strange quirk of fate, we not only had
Gareth Dyke, Paul Davis and Alan Gishlick in attendance, but Craig
Jones (New Zealand penguins) and Julian Hume (Mascarene and Hawaiian
birds). Stig Walsh and I, both residents at the department, are also
As you'd (I hope) expect, the vast majority of talks were concerned
with invertebrates, faunas and trends. Several on fishes, ranging
from teleosts to agnathans: a highlight was Mark Purnell's
remodelling of a certain Peter Benchley book cover such that the
letters 'LESS' were added, and a great big heterostracan was located
in place of the _Carcharodon_. Several talks on conodonts - the
latest cladograms (Donoghue, Forey and Aldridge) are putting
conodonts amongst gnathostomes!
Alan Gishlick (Yale) gave an excellent and very nicely illustrated
talk on the form and function of the hand in _Deinonychus_. Locking
mechanisms at the proximal ends of the manual phalanges prevent
'upwards' bending (extension) of the dromaeosaurid digits, unlike in
other types of theropods, and when digit III is flexed it actually
rotates medially and approaches the thumb. *Maybe* the third digit
can therefore act as a ventral brace to the robust second digit, and
*maybe* this has something to do with the famous crossed digits of
some of the _Archaeopteryx_ specimens. Feather fans will be pleased
to hear that Gishlick speculated that primary feathers were growing
from digit II in _Deinonychus_: this idea is backed up by well
preserved hand skeletons of _Confuciusornis_ where the phalanges
in digit II have flattened out mediolaterally and clearly support
some flight feathers. Digit III in _Confuciusornis_ is still slim,
mobile and probably capable of excursion beneath digit II.
This was a very good talk. With regard to John Jackson's earlier
post, Gishlick did not in fact say...
> "Whatever Sankar Chattergee or Greg Paul may say, we now know that
> bird flight evolved in cursorial ....."
His words were..
"[The discovery of _Deinonychus_ showed that bird ancestors were]
cursorial, terrestrial animals - that's despite the attempts of Greg
Paul and Sankar Chatterjee to put this thing in a tree"
Trust me, I have a photographic memory. John's question to Gishlick
about why pre-dromaeosaurid small theropods had not evolved elongate
hands seemed a waste of time to me, sorry John. To paraphrase Tom
Holtz, you may as well ask why Oligocene primates had not evolved the
enormous brains and plantigrade feet of hominin hominids.
The second _Deinonychus_ talk was given by Cynthia Marshall (Daniel
Brinkman, Richard Lau and Karl Bowman were non-attending
co-speakers). It concerned a horribly broken penultimate phalanx
recovered from digit II of a _Deinonychus_ foot: normally this bone
is a boring little rectangle with well developed distal condyles and
an extensive intercondylar groove. In this specimen, this bone was a
warped, sideways-expanded, transversely fractured element. The animal
must have received some severe damage to this digit (figures of more
than 1000 Newtons worth of force were mentioned) and had gone through
some painful rehealing: in Marshall's words "If it was a horse, I'd
shoot it" [audience laughs]. I'm not so confident that the survival
of this individual indicated sociality in its species - Marshall was
very cautious about this however. I got to examine the cast of the
bone she was carrying about with her.
Bird talks: David Martill spoke about the Crato Fm feather covered
with ectoparasite eggs. This was covered in _Nature_ recently so I
won't go into all the details. Gareth Dyke spoke about new work he
is doing on Eocene London Clay birds and the relevance it has for the
evolution of all neognathans. _Prophaethon_ is a pelecaniform after
all (according to Gareth's current analysis) and is well nested in
the group, being close to sulids and other advanced taxa. Bird
phylogeny afficianados will be very interested to hear that Gareth
finds _Balaeniceps_ to be within the pelecaniforms.
Parrots got special attention as Gareth and Gerald Mayr are currently
writing up a London Clay bird which has clear diagnostic psittaciform
synapomorphies. These include an unusual acrocoracoid morphology and
full zygodactyly with the fully reversed trochlea IV. Such characters
are missing from _Palaeopsittacus_ Harrison 1982, previously the
oldest supposed psittaciform record (it is London Clay), and Gareth
showed by way of quantitative analysis of the supposedly associated
_Palaeopsittacus_ elements that the taxon does not represent a single
As you may well predict, Stidham's Lance Fm parrot specimen was
bought up in the question session. In terms of new information on the
parrot fossil record, this specimen really does not fit as Eocene and
Oligocene parrots are not like the psittaciform crown group
(Psittacidae, though some might prefer to name it Psittacoidea) in
cranial morphology. The new paper on this is:
MAYR, G. and DANIELS, M. 1998. Eocene parrots from Messel (Hessen,
Germany) and the London Clay of Walton-on-the-Naze (Essex, England).
_Senckenbergiana lethaea_ 78: 157-177.
The new Middle Eocene parrot _Psittacopes_ is described in this
paper. Clear psittaciform characters are evident in the postcrania
(wing proportions are different from crown-group parrots though), but
what is remarkable is the skull: very like that of a coly. That is,
longer and lower than extant parrots, with only a gently curved
rostrum and a lower jaw nowhere near as deep, or which such a massive
coronoid, as in psittacids. Parrot cladograms therefore indicate
that the modern parrot skull did not evolve until after
quercypsittids, _Psittacopes_ and other primitive taxa: in other
words, until the Oligocene-Miocene. The Lance Fm element is
discordant with the phylogeny. I am just unable to give an opinion on
it so will shut up now.
With regard to another thread, _Archaeopteryx_ is not closely related
to any living bird. And, specifically, it has no special
relationship whatsoever with _Opisthocomus_, the living hoatzin
(which some of you might prefer to pronounced what-zin).
_Opisthocomus_ (whose specific name is not _cristatus_ as per
Chatterjee's _The Rise of Birds_ (it is _hoazin_)) is definitely a
neognath bird, a group very distant in evolutionary terms from
_Archaeopteryx_, and any similarities it may have with the latter are
purely superficial. Hand claws in _Opisthocomus_ are no big deal, as
such structures are widespread throughout birds.
However, exactly what _Opisthocomus_ IS is another matter. Previously
it has been allied both with galliforms (the chicken-grouse group),
with cuculiforms (cuckoos), with certain birds of prey (Olson 1985),
and even with cariamids and phorusrhacoids. Clearly more work needs
to be done.
"We are borg"
"I'll take that as a yes"