RE: likelyhood for these avian clades?

["John Pourtless" <vindexurvogel@hotmail.com>]

> From: "Brian Lauret" <zthemanvirus@hotmail.com>
> Reply-To: zthemanvirus@hotmail.com
> To: dinosaur@usc.edu
> Subject: likelyhood for these avian clades?
> Date: Thu, 20 May 2004 18:58:25 +0200
>
> There are a certain number of clades I've seen proposed on the net and I 
> wondered if these are really likely, or perhaps likely in a somewhat 
> altered form:
>
> clade (Psophiidae(Cariamidae(Opistocomidae(Musophagidae))))
> clade

This would indicate gruiform paraphyly, for which I see no evidence.  There 
is, however, an unquestionable relationship between Pshopiidae and 
Cariamidae.  Mayr & Clarke (2003) allied Gruidae and Psophiidae, but this is 
problematic given Mayr (2002) and the description of new material belonging 
to *Salmila robusta*, which firmly establishes a close relationship between 
these two families (contra Mayr & Clarke 2003, who allied Cariamidae with 
Opisthcomidae in an obviously polyphyletic Gruiformes).  The single most 
parsimonious tree resulting from a cladistic analysis of 35 characters 
scored for nine taxa recovered Psophiidae + Node 3, consisting of *Salmila* 
+ a node containing both *Idiornis* and Cariamidae.  Synapomorphies of this 
clade include:

1. Tip of beak more or less strongly hooked
2. Proximal end of minor metacarpal  dorsoventrally wide and bearing a well 
developed tubercle on ventral surface
3. Fenestra ischiopubica very narrow

Given these data the relationship between Psophiidae and Cariamidae can be 
considered quite robustly supported.  The question thus becomes what of 
cariamid affinity with Opisthocomidae?  Seebohm (1888b, 1895) was the first 
as far as I am aware, to not similarities between the hoatzin and gruiforms. 
 In 1888 he listed six character in which the hoatzin agreed most closely 
with Otididae (bustards).  Primarily, the hoatzin has been considered to 
either be a gallinaceous bird, a position for which there is very little 
evidence, or an aberrant cuckoo (e.g., Sibley & Ahlquist 1990).  
Mourer-Chauvire (1983) and Olson (1985a), based upon the fossil record of 
gruiforms and the anatomy of *Opisthocomus* regarded the hoatzin as most 
closely related to the Idiornithidae or Cariamidae, respectively.  Olson 
(1992b) described a primitive cuculiform from the Lower Eocene Green River 
formations, *Foro panarium* which resembles both Cuculidae and Musophagidae 
and Opisthocomidae, especially in the structure of the skull.  Thus, Sibley 
& Ahlquist's 1990 suggestion that the hoatzin is an aberrant neotropical 
cuckoo most closely allied with *Geococcyx*, *Crotophaga* and *Guira*, 
cannot be wholly ruled out.  Additional morphological evidence suggesting 
cuculiform affinity for the hoatzin includes the morphology and number of 
scleral rings (de Queiroz & Goodchild 1988) and additional molecular support 
comes from Sibley & Ahlquist (1972, 1973).  Mayr & Clarke (2003) supported 
the cariamid affinities of *Opisthocomus* with the following characters:

1. Caudal ends of vomer not fused or deeply cleft
2. Pneumatic foramina on dorsal end of caudal surface of otic process of 
quadrate present
3. Axis, corpus with pneumatic foramina on lateral surfaces
4. Caudal margin of sternum with two notches/fenestrae
5. Iliosynsacralis canal closed via fusion of cristae iliaceae dorsales with 
crista spinosa of synsacrum

Since it is readily apparent that the hoatzin is closely allied with 
Cariamidae, it becomes difficult to interpret potential similarities between 
the hoatzin and turacos and other cuckoos, to which they have as mentioned, 
been compared.  Streseman (1934) attributed such similarities to 
convergence, and Mayr & Clarke (2003) interpreted Gruiformes as 
polyphyletic, with Cariamidae apparently falling within Cuculiformes.  This 
conclusion, however, is difficult to substantiate.  It is conceivable that 
Cuculiformes is paraphyletic and that Cuculidae + Musophagidae are the 
sister group of Cariamidae + Opisthocomidae, falling within Gruiformes, but 
as far as I am aware, there have been no studies to ascertain if this is the 
case.  However, as cariamids are unquestionably more closely related to 
other gruiforms than they are to either Cuculidae or Musophagidae, this 
seems the only viable interpretation IF the topology suggested by Mayr and 
Clarke (2003), with Cariamidae + Opisthocomidae the sister clade of 
Cuculidae + Musophagidae is in fact correct.  It is perhaps more likely that 
as the hoatzin is more closely related to cariamids than cuckoos (at least 
morphologically), and the cariamids are more closely related to gruiforms 
than to cuckoos or turacos, that the similarities in the hoatzin, *Foro* and 
turacos and other cuckoos, are convergently acquired.

JGK

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