The Zygodactylidae revisited: Smith, DeBee and Clarke 2018

According to Smith, DeBee and Clarke 2018
“Zygodactylidae are an extinct lineage of perching birds characterized by distinct morphologies of the foot and wing elements.”

According to the LRT
(large reptile tree, 1137 taxa) zygodactyly (digits 1 and 4 retroverted) appeared several times by convergence in four unrelated bird clades, including toucansparrots, roadrunners and woodpeckers.

“Although the clade has a complex taxonomic history, current hypotheses place Zygodactylidae as the sister taxon to Passeriformes (i.e., songbirds).”

Earlier we learned that Eozygodactylus (Fig.1) nests with Geococcyx, the roadrunner. Among living zygodactylus birds, only parrots, like Ara, are close to the sparrow, Passer.

“Given the rather sparse fossil record of early passeriforms, the description of zygodactylid taxa is important for inferring potentially ancestral states in the largest radiation of living birds (i.e., the ~6,000 species of extant passeriforms).”

Actually
taxa related to Passer include only Passer at this point in the LRT. Other traditional passeriformes nest elsewhere.

“Despite the exceptional preservation of many specimens and considerable species diversity in Zygodactylidae, the relationships among species have not been previously evaluated in a phylogenetic context.”

Even so, 
the LRT has exposed a problem of taxon exclusion here.

“Herein, we …provide the first hypothesis of the species-level relationships among zygodactylids. The monophyly of Zygodactylidae is supported in these new analyses.”

Figure 2. Eozygodactylus reconstructed from figure 1.

Figure 2. Eozygodactylus reconstructed from figure 1. This represents  only one of four clades with a retroverted digit 4.

As defined by the authors,
“Zygodactylidae Brodkorb, 1971 is an extinct, comparatively species-rich clade of enigmatic birds that possess derived morphological features associated with a perching habitus (Mayr, 2008, 2009, 2015). Zygodactylidae is primarily characterized by a zygodactyl conformation of the pedal phalanges—possessing a retroverted fourth toe and associated accessory trochlea on the distal end of the tarsometatarsus (Olson & Feduccia, 1979).”

The authors chose woodpeckers (Piciformes) as the outgroup.
The unrelated basal barbet/toucan, Cyrilavis, nests at the first dichotomy along with the unrelated Nestor, the parrot. If you are starting to sense yet another case of taxon exclusion, then we are thinking along the same lines.

On the plus side, Botelho et al. 2014 reported
the zygodactyl foot evolved independently in different extant bird taxa.

References
Botelho JF, Smith-Paredes D, Nuñez-Leon D, Soto-Acuña and Vargas AO 2014. The developmental origin of zygodactyl feet and its possible loss in the evolution of Passeriformes.  Proceedings Biological Sciences 281(1788):20140765. doi: 10.1098/rspb.2014.0765.
Smith NA, DeBee AM and Clarke JA 2018.  Systematics and phylogeny of the Zygodactylidae (Aves, Neognathae) with description of a new species from the early Eocene of Wyoming, USA. PeerJ 6:e4950 doi: https://doi.org/10.7717/peerj.4950

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The sand grouse (genus: Pterocles) revisited

The spark for this blogpost:
A PH reader considered the nesting of the sandgrouse Pterocles with the horned screamer, Anhima, a mismatch. And it is a mismatch in terms of size, color, feet, legs, etc. The thing is… in the LRT, where only skeletal traits are tested, no other tested taxon nested closer to Anhima than Pterocles.

Figure 1. Anhima adult and chick compared to Pterocles adults

Figure 1. Anhima adult and chick compared to Pterocles adults

Earlier I only had skull data (Fig. 4) for the genus Pterocles (Figs. 1–3) and with that heretically nested Pteroclesthe sand grouse, with Anhima, the screamer (Fig. 2). Sand grouse have traditionally been nested with pigeons and chickens, or between pigeons and chickens (Shufeldt 1901), which are not related to one another in the large reptile tree (LRT, 1236 taxa).

Figure 1. Skeleton of Pterocles, the extant sand grouse. Note the 'calcaneal' tubers and manual digit zero, along with the very tiny clavicle/furcula (green).

Figure 2. Skeleton of Pterocles orientalis arenarius, the extant black-bellied sand grouse. Note the ‘calcaneal’ tubers and manual digit zero, along with the very tiny clavicle/furcula (green). This is a different species than the skull shown in figure 3, hence the different mandible ventral margin shape and other differences.

Pterocles is phylogenetically miniaturized
compared to its larger sister, Anhima, the horned screamer (Fig. 2). Even so, and despite the much larger sternum and much smaller feet, Pterocles retains a digit zero process that also includes a spike in Anhima. Both taxa have a large ‘calcaneal heel’ behind the distal tibia, rare to absent in other birds. In Pterocles pedal digit 1 does not reach the substrate and the furcula is much smaller. Both share more traits with each other than with any other taxa among the 1236 taxa in the LRT.

In this case, at least,
the addition of the post-cranial data changed nothing in the LRT tree topology. It would have been less ‘trouble’ to have Pterocles nest with pigeons, or chickens, but a good scientist reports results, no matter how they differ from tradition.

FIgure 2. The larger Anhima compared to its smaller sister, Pterocles.

FIgure 3. The larger Anhima compared to its smaller sister, Pterocles. Note the digit zero spur on the manus along with the ‘calcaneal tuber’ behind the distal tibia.

Back in 1901
Shufeldt reported, “the sand grouse constitute a small assemblage of forms, related on one hand to the gallinaceous (chicken-like) birds, and on the other to the pigeons.” The two clades are not related to one another in the LRT. And that statement was made before the invention of the airplane, computer and PAUP.

Figure 1. Pterocles, the chestnut-bellied sandgrouse is not related to pigeons, despite convergent appearances, but more closely related to the screamer, Anhima.

Figure 4. Pterocles, the chestnut-bellied sandgrouse is not related to pigeons, despite convergent appearances, but more closely related to the screamer, Anhima.

The Fulica, Anhima, Petrolcles clade
is a basal one, probably extending back to the Early Cretaceous. It is a sister clade to the chicken/sparrow/parrot clade, far from the New World vulture/pigeon clade.

References
Shufeldt RW 1901. On the systematic position of the sand grouse (Pterocles: Syrrhaptes). The American Naturalist 35 (409):11–16.

 

Is a sandgrouse almost a pigeon? Is a sandgrouse almost a grouse?

No. And No.
No matter what you may read, a sandgrouse (genus: Pterocles) does not nest with pigeons in the large reptile tree (LRT, 1235 taxa), but with the screamer, Anhima. And those two do not nest with Tetrao tretix, the black grouse, which nests between chickens and sparrows in the LRT.

Figure 1. Pterocles, the chestnut-bellied sandgrouse is not related to pigeons, despite convergent appearances, but more closely related to the screamer, Anhima.

Figure 1. Pterocles, the chestnut-bellied sandgrouse is not related to pigeons, despite convergent appearances, but more closely related to the screamer, Anhima.

Pterocles exustus (Temminck 1815) is the extant chestnut-bellied sandgrouse. This vegetarian prefers bushy, arid lands.

References
Timminck CJ 1825. Atlas des oiseaux d’Europe, pour servir de complément au Manuel d’ornithologie de M. Temminck. Belin, Paris 1826–42.

wiki/Chauna
wiki/Fulica
wiki/Pterocles

Hello, Robin! Where do you nest?

Short answer:
Turdus migratorius (Linneaus 1758) nests between the crow (Corvus) and the jay (Cyanocritta) in the large reptile tree (LRT, 1232 taxa) based on skeletal traits. 

Figure 1. Turdus migratorius, the American robin, nests between the crow (Corvus) and the blue jay (Cyanocritta).

Figure 1. Turdus migratorius, the American robin, nests between the crow (Corvus) and the blue jay (Cyanocritta).

According to Prum et al. 2015
which tests DNA sequences, Turdus nests with 13 taxa not tested in the LRT along with Corvus, the crow. So there is some agreement here. However, the basal taxon in this subclade within a larger clade, Passeriformes, is Menura, the lyrebird.

By contrast,
in the LRT, Menura nests with cuckoos, apart from crows and jays.

Ironically,
the genus Passer (the sparrow) was not included in the Prum et al. study. In the LRT, Passer nests between chickens and parrots, apart from lyrebirds, robins, crows, and jays. So the Prum et al. study does not tell us if Passer is a passeriform or not. In the LRT, the lyrebird, crow and robin are not related to Passer.

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.

Hello Robin Cookies

 

The curassow (genus: Mitu/Crax) another chicken cousin

Mitu tuberosum aka Crax turberosa (Linneaus 1758, Spix 1825; 85 cm) is the extant razor-billed curassow, a pheasant-like galliform from the Amazon. Only two eggs are laid per year. Precocious young are feathered and mobile after hatching. Omnivorous. Sexes are similar.

Figure 1. Crax tuberosa skeleton and invivo. This basal neognath bird prefers to walk than fly.

Figure 1. The curassow, Mitu tuberosum/Crax tuberosa, skeleton and invivo. This basal neognath bird prefers to walk than fly.

In the large reptile tree (LRT, 1127 taxa) the curassow (genus Mitu or Crax) nests with the Early Cretaceous bird, Eogranivora, and this clade nests with the chicken (Gallus) and the peafowl (Pavo).

Figure 1. Crax tuberosa skull in three views.

Figure 2. The curassow, Crax tuberosa, skull in three views. Note the slender postorbital (yellow) descending from the robust postfrontal (orange).

The helmeted curassow (genus: Pauxi pauxi) has a casque convergent with the cassowary (Casuarius).

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.
von Spix JBR 1825. Avium species novae, quas in itinere per Brasiliam annis MDCCXVII – MDCCCXX […] collegit et descripsit. Franc. Seraph. Hübschmann, Monachii [Munich], 1, [VII], 90 pp., 91 pls.

wiki/Crax
wiki/Mitu
wiki/Razor-billed_curassow

The origin of hummingbirds from sea gulls, part 2

I was looking for a small seagull,
as a transitional taxon leading toward hummingbirds, but I could not find one better than Eocypelus (Fig. 1) from the Eocene. Then I looked for a giant hummingbird. That’s when I found Patagona gigas (Fig. 1).

Earlier, with 100 fewer taxa,
the large reptile tree (LRT, 1227 taxa) nested hummingbirds with Chroicocephalus, the extant seagull (Fig. 1) here.

Figure 1. The origin of hummingbirds from the sea gull, Chroicocephalus.

Figure 1. The origin of hummingbirds from the sea gull, Chroicocephalus. Patagona is a giant hummingbird. Archilochus is a mid-sized ruby-throated hummingbird. Mellisuga is the bee hummingbird, the smallest adult bird, theropod and dinosaur. Patagona skull from Digimorph.org and used with permission.

Phylogenetic miniaturization
(also called the Lilliput effect), is a key driver in the genesis of new clades. This neotonous trend also brought us hummingbirds… and tiny hummingbirds, including the smallest of all birds, the bee hummingbird (genus: Mellisuga, Fig. 1). Eocypselus more clearly represents phylogenetic miniaturization due to its short rostrum. Thereafter the descendants of Eocypselus leading toward hummingbirds developed a longer rostrum, like that of Patagona. Otherwise their skulls are about the same size. Perhaps this was the transition point leading to nectar feeding, rather than sea dipping.

Figure 2. Patagona gigas, the giant hummingbird.

Figure 2. Patagona gigas, the giant hummingbird.

Patagona has a relatively slow wing beat
while hovering, only 15 wing beats per second. According to Wikipedia, “Hummingbird muscle fibres are filled with mitochondria (50% by volume) enabling high frequency wing beats to be sustained over extended periods using oxidative energy.” The range of this genus extends along the Pacific side of the Andes from Ecuador to mid-Chile.

The Andean gull (Chroicocephalus serranus) has a similar range and, unusual for a gull, breeds inland in mountain areas and can be found around rivers, lakes, marshes and pasturelands. It is an insectivore, sometimes aerially and otherwise on fields and grasslands. Distinct from hummingbirds, the Andean gull swims like a duck. But hummingbirds do like bird baths.

References

wiki/Hummingbird
wiki/Archilochus
wki/Eocypselus_rowei
wiki/Patagona
wiki/Mellisuga
wiki/Black-headed_gull

Tiny Pumiliornis: enigma no longer

Pumiliornis tesellatus
is a wren-sized (shown larger than actual size) Messel pit bird that was originally (Mayr 1999) considered an enigma and later (Mayr 2008) allied with cuckoos. In the large reptile tree (LRT, 1225 taxa) tiny Pumiliornis nests with Platalea, the spoonbill (Fig. 2) as a phylogenetic miniature, close to, but not quite related to the parallel, short-legged genesis of ducks and geese.

Presbyornis, currently at the base of ducks, still has long legs and a long neck. More derived taxa in the duck branch lose their long legs, although some, like the swan and goose, retain a long neck.

Figure 1. Pumiliornis is a phylogenetic miniature related to the spoonbill, Platalea, at the genesis of ducks.

Figure 1. Pumiliornis is a phylogenetic miniature related to the spoonbill, Platalea, at the genesis of ducks.

Pumiliornis tessellatus (Mayr 1999, 2008; 6cm long; middle Eocene). This wren-sized relative to spoonbills and ancestor to ducks has a spatulate beak tip. This is a neotonous form of the long-legged spoonbill with juvenile size and proporitons representing the genesis of a new clade. This fossil contains fossil grains in the cloacal area (white box). Note that no webbing is preserved between the toes. Spoonbills also lack webbed toes.

Figure 1. The roseate spoonbill (genus: Platalea) in vivo. Traditionally spoonbills and storks have been nested together. Here it nests between storks and ducks.

Figure 2. The roseate spoonbill (genus: Platalea) in vivo. Traditionally spoonbills and storks have been nested together. Here the spoonbill nests between the ibis, Threskiornis, and ducks.

Figure 4. Subset of the LRT focusing on the crown bird clade. Brown taxa are all long-legged. Neotony produces the smaller, shorter-legged, arboreal taxa.

Figure 4. Subset of the LRT focusing on the crown bird clade. Brown taxa are all long-legged. Neotony produces the smaller, shorter-legged, arboreal taxa.

References
Mayr G 1999. Pumiliornis tessellatus n. gen. n. sp., a new enigmatic bird from the Middle Eocene of Grube Messel (Hessen, Germany). Courier Forschungsinstitut Senckenberg, 216: 31–73, Frankfurt a.M. 1999.
Mayr G 2008. Pumiliornis tessellatus MAYR, 1999 revisited – new data on the osteology and possible phylogenetic affinities of an enigmatic Middle Eocene bird. Palfontologische Zeitschrift. 82/3: 247–253.

wiki/Platalea
wiki/Pumiliornis