Saturday, January 12, 2008

New World Old World Vultures?

Quite a while ago I discussed the fossil history (and perhaps origin) of the cathartids or "New World" vultures in the Old World - and hinted at a "tale for another day". The cathartids are of rather uncertain taxonomic placement (a distinct order?) while the "Old World" vultures are placed in order Falconiformes* in the family Accipitridae and sub-family Aegypiinae. BUT - and there always is one regarding classification these days - this should be "Aegypiinae" since genetic evidence suggests that Gypaetus (Bearded vulture), Neophron (Egyptian vulture), Gypohierax (Palm-nut vulture) and perhaps Polyboroides (Harrier-Hawks) form a clade rather distanced from the remaining 6 genera of "vultures" (Griffiths et al., 2007). So Aegypiinae is apparently both para- and polyphyletic, huh. As the photos suggested, the three genera of "vultures" are superficially rather aberrant looking so perhaps this is not too much of a shock. Siebold & Helbig 1995 suggested the sub-family Gypaetinae for Gypaetus and Neophron; and I'll use Aegypiinae for the remaining and more conventional "vultures".

*Or Accipitriformes, Griffiths et al. 2007 placed Falco pretty far away. I probably shouldn't get into this.

Why go through all this trouble? Reportedly, both Gypaetinae and Aegypiinae have occupied the New World at some point of time. This is rather remarkable on top of the vulturids/cathartids living there and caracaras (Polyborinae). Marabou stork relatives (Leptophilini) were also present, but there's nothing to suggest they were scavengers (Jabiru isn't). Oh and teratorns don't appear to have been scavengers, despite their common depiction as super-condors.

Anyways, let's take a look at these New World Old World vultures:


Neophrontops is a genus with five species related to Neophron that lived in North America from the mid-Miocene to upper Pleistocene (Fedducia, 1974), so it certainly did not have a very casual appearance. I should note that Fedducia's described species, Neophrontops slaughteri, was named for, ehem, one Bob Slaughter. Fedducia's vulture species did not appear to overlap chronologically but a later study (Rich, 1977) showed that two species (N. americanus and N. vallecitoensis) were both present in the mid-Pleistocene with different sizes (the latter was larger); this could make it a radiation of sorts, albeit a rather brief one. Fedducia notes that Neophron fossils have not been found in Africa (this still appears to be true) and suggests that, gulp, the current species is the result of an invasion of Old World vultures to the Old World from the New World perhaps as recently as the Pleistocene. The genetic grouping with Old World species may not be entirely inconsistent, although it would require this lineage to be oddly invasion prone.


While the Neophron/Neophrontops relation appears to be rather unambiguous one, larger reported New World Old World vultures are rather, well, problematic. Two genera have been classified in Aegypiinae: Palaeoborus and Neogyps. In the description of a new Palaeoborus species by Miller & Compton 1939, it (well, its ulna) is noted as being similar to Neogyps except for differences in the shape of the condyle; oh and it is somewhat comparable to Haliaeetus. Why does this stick out to me? Hertel 1995 notes that Neogyps, the "Errant eagle" was originally considered an eagle with vulturine habits, then re-classified in Aegypiinae; but skull indices used to determine diet classified it as a mammalivore, possibly a generalized one. I unfortunately couldn't find Patricia Rich's book on the subject of fossil vultures, but the book The Origin and Evolution of Birds* by Alan Fedducia (partially available here, p. 299-300) notes that she couldn't conclude on their relations and raised the possibility that they are one or more separate branches of hawks or eagles.

*Oh, and it mentions that Ciconia maltha was the ecological equivalent of the marabou stork. I haven't seen this confirmed elsewhere.

I haven't seen any more recent work on the phylogenetics of these species, although that would be difficult seeing as how Accipitridae is currently undergoing upheavals. Are the genera related? Palaeoborus is from the Upper Miocene to Lower Pliocene and Neogyps is from the Upper Pleistocene (Fedducia, 1974), so there is only a mild ghost lineage. Fedducia hinted at the possibility of Old World vultures having New World origins, but we'd have to assume that eagle-like characteristics were due to the basal nature of the genera. These seem to be rather ambiguous species here, so it doesn't seem as if we can do much aside from speculating on their relations. I guess for now that we'll have to conclude that there is no unambiguous evidence for New World members of Aegypiinae.

Not having Rich's book has made this post difficult, but it appears that nothing more definitive can be known. I for one thought things were a little more definitive before starting this post for one thing, but I learned better. Well, at least we got New World Old World "vultures" of a sort.

Next time I think I'll blog on something less old and ambiguous.



Fedducia, Alan. 1974. Another Old World Vulture from the New World. The Wilson Bulletin. Vol. 83, No. 3. Available (for free).

Griffiths, Carole S. et al. 2007. Phylogeny, diversity, and classification of the Accipitridae based on DNA sequences of the RAG-1 exon. J. Avian Biol. 38: 587- 602.

Hertel, Fritz. 1995. Ecomorphological Indicators of Feeding Behavior in Recent and Fossil Raptors. The Auk, Vol. 112, No. 4., pp. 890-903.

Miller, Alden H. & Compton, Lawrence V. 1939. Two Fossil Birds from the Lower Miocene of South Dakota. The Condor, Vol. 41, No. 4., pp. 153-156.

Siebold, Ingrid & Helbig, Andreas. 1995. Philosophical Transactions : Biological Sciences, Vol. 350, No. 1332, pp. 163-178

Rich, Patricia Vickers. 1977. Temporal range extension of Neophrontops americanus (Accipitridae). The Condor, 79: 494-509. Available (for free)

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