Crows, hamerkops, pelicans and shoebills: related.

Figure 1. Pelecanus skeleton.

Figure 1. Pelecanus skeleton. We’ll come back to this below as a terminal taxon.

the large reptile tree (LRT, 1110 taxa) grew by one taxon, the pelican (Pelecanus, Fig. 1). It nested between the hamerkop (Scopus, Figs. 3, 4) and the shoebill (Balaeniceps, Fig. 5, 6) and all were derived from a taxon close the American crow, Corvus (Fig. 2).

Figure 1. Corvus is the basal taxon in the LRT for the taxa listed here and many, many more.

Figure 1. Corvus is the basal taxon in the LRT for the taxa listed here and many, many more.

Cornvus brachyrhynchos (Linneaus 1758) is the extant American crow. Derived from herons and cuckoos, Corvus is generalized bird basal to a long list of sea and land birds all with a long maxilla.

Figure 1. Scopus umbretta, the extant African hammerkop.

Figure 2. Scopus umbretta, the extant African hammerkop. The beak is primitively taller than wide and much longer than in Corvus. Note the elevation of the naris and the greater expanse of the maxilla (green).

Scopus umbretta (Brisson 1760, 56 cm tall) is the extant hamerkop, a mid-sized wading bird. It nests with the shoebill and pelican (below) in the large reptile tree. This clade nests between storks, like Threskiornis and petrels, like Macronectes all derived from a sister to Corvus the crow.

Figure 4. Scopus, the hammerkop, in vivo.

Figure 3. Scopus, the hammerkop, in vivo. The beak and legs are longer than in Corvus the crow.

So essentially,
the hamerkop is a long-legged wading crow with a long beak.

Figure 3. Balaeniceps, the shoebill stork.

Figure 4. Balaeniceps, the shoebill stork. Note the absence of an antorbital fenestra. The maxilla is larger here than on any other bird. Note the majority of the palate is composed of the premaxilla rimmed by the maxilla.

Balaeniceps rex (Gould 1850, up to 140 cm tall) is the extant shoebill stork. It has a broad beak, a flat head and robust cheek bones. Here it nests with the hamerkop and pelican.

Figure 4. Shoebill stork and skeleton.

Figure 5. Shoebill stork and skeleton. Here the beak was wider and the legs were longer.

So essentially
the shoebill is a longer-legged, broader-billed hamerkop.

Figure 1. Pelecanus skeleton.

Figure 1 again. Pelecanus skeleton has shorter legs than the hamerkop and shoebill, and a longer rostrum, retaining an antorbital fenestra.

Pelecanus onocrotalus (Linneaus 1758) is the extant great white pelican. It has a large skull, longer wings and shorter legs than its relatives, the hamerkop and shoebill.

So essentially
the pelican is a short-legged, long rostrum hamerkop.

Key point of today’s blog:
Just think of all the transitional taxa between these terminal extant specimens, now extinct. Pelicans (genus Pelecanus) go back at least 30 million years. Of course, that means the above list of taxa goes back much, much further. Someday we’ll find Late Cretaceous crows and maybe hamerkops, IMHO.

Brisson MJ 1760. Ornithologie, ou, Méthode contenant la division des oiseaux en ordres, sections, genres, especes & leurs variétés : a laquelle on a joint une description exacte de chaque espece, avec les citations des auteurs qui en ont traité, les noms quils leur ont donnés, ceux que leur ont donnés les différentes nations, & les noms vulgaires
Gould J 1850. The birds of Asia. Part I. London.
Linnaeus C 1758. Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata.




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