Masillaraptor

Only one species of Masillaraptor is known: M. parvunguis

Masillaraptor comes from the Latin word Masilla, which is the old name for the town of Messel, and raptor is a New Latin suffix used to indicate a predator (from rapere, to catch) and in English it means bird of prey.

Specific epithet parvunguis is also Latin, coming from the word parvus which means small and feeble, while unguis means claw.

The name refers to the fact that the specimen's claws are small in comparison to those of other raptors.

The genus Masillaraptor is different from all other known avian taxa. It possesses a combination of characters that distinguishes it from all others.

1. The beak is almost as long as the cranium itself, with equal height over much of its length and a straight dorsal ridge. The beak curves just before its tip, restricting the nasal openings to the rear half of the beak.

2. The tibiotarsus is the longest bone in the leg.

3. On the second toe the first phalanx is shortened, whereas on the fourth toe the second and third phalanges are shortened.

4. The claws of Masillaraptor are small and weak compared to other falconiform birds with abbreviated pedal phalanges.

Characters (1) and (3) are derived within neornithine birds and also found in modern Accipitres, from which Masillaraptor is, however, distinguished in character (4).(Mayr, 2006.)

There are two specimens of Masillaraptor. Only one specimen was referenced for classification because the other is housed in an unknown private collection. Both specimens are a slab of rock containing a nearly complete, articulate but poorly preserved skeleton. The specimens are both believed to be adult members of the species. Both specimens were discovered in the Messel pit, an old shale mine known for the extremely well preserved fossils that have been discovered there.

Masillaraptor represents one of two members of Masillaraptoridae within the Falconiformes. The cladogram below displays the results of the phylogenetic analysis by Mayr & Kitchener (2022):[3]

	Chauna torquata (southern screamer) Australaves Falconiformes Caracara plancus (crested caracara) Masillaraptoridae Masillaraptor parvunguis Danielsraptor phorusrhacoides Cariamiformes Bathornis spp. Dynamopterus spp. Cariama cristata (red-legged seriema) Phorusrhacidae (terror birds) Llallawavis scagliai Psilopterus lemoinei Patagornis marshi

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