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Dear Darren,

Xenicibis xympithecus wasn't described by Olson and Wetmore, but by Olson
and Steadman:

Storrs L. Olson & David W. Steadman, 1977
A New Genus of Flightless Ibis (Threskiornithidae) and Other fossil Birds
from Cave Deposits in Jamaica 
Proceedings of the Biological Society of Washington 90(2): 23-27

Type: Xenicibis xympithecus

Holotype: Proximal half of left tarsometatarsus, AMNH 11006.,

Paratypes:  8 other specimen: coracoid, coracoid, shaft humerus (AMNH
11031), proximal end femur, proximal end tibiotarsus, distal 1/3
tibiotarsus, 2/3 tibiotarsus and pedal phalanx 1 digit IV. Noteworthy is
that Olson and Steadman state: that possibly the humerus doesn't have the
same data as the holotype (collected 16 or 17 Januari 1920 by H. E. Anthony
at Long Mile Cave, Windsor, Trelawny Parish, Jamaica.), they go on giving
some measurements (for the humerus
: width and depth of the shaft at distal end of the attachment of latissimus
dorsi postoralis 6.2, 6.4 (I hope mm.). Here they don't mention nything
about quadrupedallity., But things are becomming more interestingly:

In 1979 there was an additional paper by the same authors:

Storrs L. Olson & David W. Steadman, 1979
The Humerus of Xenicibis, the Extinct Flightless Ibis of Jamaica 
Proceedings of the Biological Society of Washington 92: 23-27

I will give the abstract:

The first known complewte humerus of the extinct fossil Ibis Xenicibis
xympithecus is reported from a new locality in Jamaica. The specimen
exhibits many of the morphological characteristics seen in flightless birds
and possesses a number of characters which distinguish it readely from all
other ibises.

If there was even a suggestion of quadrupedallity, I guess it would be
mentioned. I haven't read this paper since 4 years, but if I remember
correctly (IIRC!, yes I learn!), there wasn't any suggestion in ths paper in
that direction.

I do not know of any other paper about Xenicibis. But if there is any, and
certainly one about Xenicibis being a quadrupedal, please, please let me
know with full reference.

>Ron asked me to send more information on _Xenicibis_, possibly the 
>only facultatively quadrupedal bird ever, so here goes. I do not have the 
>literature to hand, nor have I in fact seen the paper where Olson 
>suggests quadrupedality in this animal: I'm going from what I learnt off 
>Julian Hume (an ornithologist who specialises in Mascarene birds: see 
>_Smithsonian_ 30 (12), March 2000). 
>_Xenicibis xympithecus_ Olson and Wetmore 1976 is from Jamaica.

Well here you are. Of coure did Olson and Wetmore descibe an ibis in 1976,
but it wasn't Xenicibis and it wasn't from Jamaica. It was, of course
Apteribis glenos from Hawaii:

Storrs L. Olson & Alexander Wetmore, 1976
Preliminary Diagnoses of Extraordinary New Genera of Birds from Pleistocene
Deposits in te Hawaiian Isands 
Proceedings of the Biological Society of Washington 89(18): 247-258

One of the paratypes was a right humerus (BBM-X 147240, Bishop Museum))

In the remarks Olson and Wetmore mention the fact that (at that time) it was
the only lightless ibis, and also the only flightless member of the

Of course the stiry of Apteribis doesn't end here.

In 1991 Storrs Olson and Helen James described thirty-two new species from
Hawaii. Amonf them there was, of course Apteribis glenos Olson and Wetmore,
1976, but also a new species of Apteribis: Apteribis brevis Olson & James, 1991.
But here also, no mentioning of quadrupedallity. So again, what is the
complete reference for your statement? I know about quadrupedal pterosaurs,
but ibises?, please , let me know. I know birds are amazing, but quadrupedal?

Hope it helps,


>apparently resembled other robust ibises but for its wings. These are 
>really peculiar, with uniquely modified ulnae and carpometacarpi. The 
>ulnae have markedly attenuated distal ends and are fairly straight; the 
>carpometacarpi are large fused clubs, totally unlike those of any other 
>bird. Accordingly, Olson suggested that these might have been used in 
>supporting the animal in a quadrupedal pose. I understand this was 
>published in a short paper (or extended abstract?) presented at an 
>American ornithological convention. The idea is not mentioned in the 
>_Proc. Biol. Soc. Washington_ paper that first described this bird.
>>From the global perspective, what's interesting about _Xenicibis_ is 
>that it has helped demonstrate the weirdness potential of ibises. For 
>decades, all known ibises were pretty much the same, and despite their 
>geographical and ecological success, they all looked pretty similar. It is 
>only within the last 20 years that extinct island endemics have changed 
>this view - we now know that ibises evolved flightlessness on the 
>Hawaiian islands (_Apteribis_) and in the Caribbean. The Mascarene 
>form _Borbonibis_, now regarded as the origin of the Reunion 
>solitaire (_Ornithaptera_/_Victoriornis_) myth (more on that to appear 
>in print soon), was not flightless and has recently been regarded as 
>possibly congeneric with _Threskiornis_. At least some of these forms, 
>like _Xenicibis_, were morphologically absurd as birds go. 
>Finally, what are ibises? Most recent parsinomy analyses of Cainozoic 
>bird taxa find that the traditional clades of Gadow and Wetmore (e.g., 
>Gruiformes, Coraciiformes, Pelecaniformes) are supported 
>empirically, whereas rather more unorthodox alternatives (e.g., that 
>falconids are closest to musophagids, that herons are gruiforms, that 
>anseriforms are charadriiforms etc.) are not. To my knowlegde no 
>study has yet been holistic enough to look at ciconiiforms as well as 
>palaeognaths, gruiforms and other groups, but I suppose people are 
>working on it. Where ibises fall into all this will be interesting - and 
>here we go back to the polyphyletic ratites thing - because Olson has 
>suggested that kiwis might be modified ibises. I suppose I should also 
>note that we might consider spoonbills as modified ibises too.
>Finally finally, are there any onychophoran experts out there?
>School of Earth, Environmental & Physical Sciences
>Burnaby Building
>Burnaby Road                           email: darren.naish@port.ac.uk
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