A fossil bird from Denmark is helping researchers understand how the unusual feet of modern trogons evolved.
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feet → help → trogons
The fossil belongs to a species called Daniatrogon kochi, which lived about 55 million years ago during the Early Eocene.
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which → belong → Eocene
Researchers found the fossil in 1989 on the Danish island of Mors in the Fur Formation.
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Researchers → find → Formation
According to the study published in the Journal of Systematic Palaeontology titled ‘
Evolution of a morphological novelty: exceptional skeleton of an early Eocene trogon (Aves: Trogoniformes) elucidates the origin of a unique foot morphology’, the specimen is one of the oldest known trogoniforms and preserves a foot that differs from other known trogoniforms.
uncertain
that → accord → trogoniforms
What does the 55-million-year-old fossil reveal about trogon feet
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fossil → reveal → feet
The nearly complete skeleton of Daniatrogon kochi was found on a beach on the Danish island of Mors in 1989 by fossil collector Karsten Koch, whose name is also reflected in the species name.
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name → find → name
The fossil comes from the Early Eocene Fur Formation and is exceptionally well preserved.
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fossil → come → Formation
The presence of medullary bone shows that the specimen was a breeding female.
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specimen → show → bone
A phylogenetic analysis places Daniatrogon kochi as the earliest diverging member, though the analysis did not fully resolve how several early trogons are related to each other.
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trogons → place → other
Its foot also sets it apart from other known trogoniforms because the second toe was not fully reversed (it may have been slightly rotated inward).
uncertain
it → set → trogoniforms
Modern trogons have a permanently reversed second toe that works with the big toe against the other two front toes.
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that → have → toes
This distinctive arrangement is known as a heterodactyl foot.
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arrangement → know → foot
PC: Journal of Systematic Palaeontology
How did the unusual trogon foot evolve over time
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foot → evolve → time
The unusual foot of Daniatrogon kochi helps show how the distinctive trogon foot developed.
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foot → help → kochi
Modern trogons have a heterodactyl foot in which the second toe is permanently reversed.
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toe → have → which
The same arrangement is also found in other known fossil trogons.
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arrangement → find → trogons
It has generally been considered an adaptation for perching that helped compensate for a weak big toe.
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that → consider → toe
Daniatrogon kochi, however, had a very long big toe.
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kochi → have → toe
The study also notes that the Messel trogon, Masillatrogon had a long big toe.
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trogon → note → toe
Together, these fossils show that the big toe was reduced later in the lineage.
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toe → show → lineage
The findings indicate that the reversed second toe developed before the big toe shrank, providing a clearer sequence for the evolution of the distinctive trogon foot.
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toe → indicate → foot
Evolution of trogon beaks
Daniatrogon kochi also differed from living trogons in the shape of its beak.
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kochi → differ → beak
The fossil had a narrower beak, a feature also seen in other stem-group trogoniforms such as Eotrogon and Primotrogon.
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fossil → have → Eotrogon
Living trogons have wider beaks that they use to excavate nesting cavities in soft, rotting wood.
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they → live → wood
The narrower beaks of these early forms may suggest that they used existing holes for nesting or dug nesting cavities in soil with their feet.
uncertain
they → suggest → feet
The study places the change in the foot before the widening of the beak.
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study → place → beak
This provides another detail about the early history of trogoniforms and shows that their distinctive features developed at different stages.
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features → provide → stages
How did early trogoniforms move differently from modern trogons
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trogoniforms → move → trogons
The study also examines how early trogoniforms may have differed from living trogons.
uncertain
trogoniforms → examine → trogons
Modern trogons are relatively sedentary birds that search for food by making short flights from perches.
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that → search → perches
Stem-group trogoniforms may have moved more actively through branches and vegetation while feeding.
uncertain
trogoniforms → move → branches
Their stronger grasping feet would have helped with this movement.
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feet → grasp → movement
The later reduction of the big toe may have been linked to a more sedentary lifestyle, when the reversed second toe was enough for perching.
uncertain
toe → link → perching
Early trogoniforms also had more varied beak and foot shapes than their living relatives, which the study takes to mean they were ecologically more varied.
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they → have → which
The Aporia
