Hornbills, toucans and the Cretaceous

Earlier
the large reptile tree (LRT, 1118 taxa) nested the toucan, Pteroglossus, between the stink bird, Opisthocomus, and the parrot Ara + the giant parrots, Dinornis and Gastornis. That seemed reasonable. They are all frugivores and the nostril is high on parrots and toucans. However, with the addition of two taxa (Figs 2-5), and the reexamination of several others (remember, I’m new to birds) toucans moved from parrots to between crows and ducks (Fig. 4).

Figure 1. Pteroglossus, the toucan shares many traits and nests with Buceros in the LRT.

Today
the hornbill, Buceros (Figs. 2,3) is added to the LRT. Traditionally hornbills and toucans do not nest together. All similarities have long been considered convergent. Here, in the LRT, toucans and hornbills do nest together. Very few traits distinguish the two in the LRT.

Figure 2. Buceros skeleton and in vivo image.
Figure 2. Buceros skeleton and in vivo image. Without the horn it does look like a big crow.

So,
toucans are New World hornbills and/or hornbills are Old World toucans. So far… Remember all hypotheses of relationships can be trumped with better and more data.

Pteroglossus aracari (Linneaus 1758) is the extant black-necked aracari, a type of toucan. Toucans are restricted to the New World. Like the parrot, the bill is deep. Unlike the parrot, the nares are dorsal. Like the parrot pedal digit 4 is reversed. Wikipedia reports that toucans are related to woodpeckers. Here toucans are related to hornbills between stink birds and parrots. Like hornbills, toucans nest in tree hollows and are omnivores.

Figure 3. Buceros skull in several views. The smaller drawing shows the nares and antorbital fenestra on a younger bird. Here the premaxilla and maxilla are fused together.

Buceros hydrocorax (Linneaus 1758) is the extant rufous hornbill. Hornbills are restricted to the Old World. Most studies find toucans and hornbills unrelated, similar only by convergence. The present study finds they are sister taxa. Nearly every trait in these two is identical to the other. The separation of toucans and hornbills had to happen by the Albian (Latest Early Cretaceous, 100 mya) based on the distance between the two continents at that time and the fact that these taxa are not long distance flyers.

Figure 1. Updated subset of the LRT focusing on crown birds. Colors indicate general body size and niche.
Figure 1. Updated subset of the LRT focusing on crown birds. Colors indicate general body size and niche.

The Piciformes question
Wikipedia , representing traditional systematics and taxonomy, nests toucans and barbets with woodpeckers, like Melanerpes, which nests here (Fig. 4) between swifts like Hirundo and dippers with Cinclus, all insect eaters, not frugivores. The LRT recovers a nearly completely different tree topology.

Also added:
Psilopogon pyrolophus (S. Müller 1836; 28 cm in length; SE Asia) is the extant fire-tufted barbet. This frugivore resides at the base of toucans + hornbills and it also uses tree cavities to nest and raise chicks in.

FIgure 5. Psilopogon, is a living barbet from SE Asia.
FIgure 5. Psilopogon, is a living barbet from SE Asia. Other barbets are found in the New World. A pretty little Corvimorph. Note the backward rotated fourth toe, not found in Old World hornbills, but is found in New World toucans.

Of added interest,
hornbills are restricted to the Old World, from Africa to Asia. Toucans are restricted to the New World. Since they shared a last common ancestor similar to both, the two clades must have separated when the continents separated, in the Albian (latest Early Cretaceous, 100 mya; Fig. 6). If true, this supports a growing realization that Neoaves did not radiate after the Cretaceous, but deep within that time period. Jungle taxa do not generally fossilize well. Even so, confirmation will be big news. Smaller barbets are found world wide.

Figure 4. South America and Africa during the Albian, 100 mya. This is when toucans and hornbills must have separated.
Figure 4. South America and Africa during the Albian, 100 mya. This is when toucans and hornbills must have separated.

References
Linnaeus C 1758. 
Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata.
Müller S 1836. Reizen en onderzoekingen in den Indischen archipel, gedaan op last der Nederlandsche Indische regering, tusschen de jaren 1828 en 1836, 1857

wiki/Black-necked_aracari
wiki/Toucan 
wiki/Rufous_hornbill
wiki/Fire-tufted_barbet

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