The fossil record of crown group birds (Neornithes) prior to the Cretaceous-Paleogene boundary is scarce and fragmentary. Early Cenozoic bird fossils are more abundant, but are typically disarticulated and/or flattened. Here we report the oldest roller (Coracii), Septencoracias morsensis gen. et sp. nov. (Primobucconidae), based on a new specimen from the Early Eocene (about 54 million years ago) Fur Formation of Denmark. The new fossil is a nearly complete, three-dimensionally preserved and articulated skeleton. It lies at the lower end of the size range for extant rollers. Salient diagnostic features of Septencoracias relative to other Coracii include the proportionally larger skull and the small, ovoid and dorsally positioned narial openings. Our discovery adds to the evidence that the Coracii had a widespread northern hemisphere distribution in the Eocene. Septencoracias is the oldest substantial record of the Picocoraciae and provides a reliable calibration point for molecular phylogenetic studies.
Coracii sensu Clarke et al.
Primobucconidae Feduccia and Martin, 1976
Septencoracias morsensis gen. et sp. nov.
Etymology: From the Latin word ‘septentrio’ meaning north, and the genus name ‘Coracias’. The specific epithet refers to the Island of Mors, from where the fossil bird came.
Holotype: MGUH.VP 9509, 3-D preserved skeleton lacking sternum and most shoulder girdle elements.
Type locality and horizon: Moclay pit (Klovbakker), Island of Mors, north-western Jutland, Denmark (Fig. S1). Fur Formation, Ypresian, Early Eocene, ca. 54 MA; marine diatomite layer right above ash layer +30 in the mid part of the formation (Fig. S2).
Diagnosis: Septencoracias morsensis is a small roller that differs from all other Coracii (i.e., Primobucco, Paracoracias, Eocoracias, Geranopterus and crown group Coracii) in the small, ovoid and dorsally positioned narial openings (unknown in Geranopterus) and in the significantly larger skull. Septencoracias also differs from all Coracii except Paracoracias in the equal distal extent of major and minor metacarpals.
Septencoracias is assigned to the Primobucconidae based on the following derived characteristics: unossified nasal septum; strongly developed deltopectoral crest of humerus; alular claw present. Moreover, the morphology of the tarsometatarsus of Septencoracias matches well with that of the Primobucconidae. However, Septencoracias differs from Primobucco in many characters: culmen evenly curved; mandibular symphysis longer and more ventrally projected; triangular pygostyle with tall and craniocaudally narrow lamina; acromion of scapula smaller; deltopectoral crest of humerus more prominent; bicipital crest straighter and shorter in distal extent; terminal process of ischium shorter; first phalanx of hallux markedly longer.
Septencoracias differs from Eocoracias in the following characteristics: longer beak; hand skeleton longer relative to the other wing elements; femur shorter and tarsometatarsus longer relative to the tibiotarsus. Septencoracias differs from Paracoracias in the following features: extensor process of carpometacarpus larger; minor metacarpal thicker; first phalanx of hallux longer. Septencoracias differs from Geranopterus in the following characters: acromion of scapula not bifurcated; process on ventral side of proximal end of minor metacarpal smaller; plantarly projected metatarsal trochlea II.
Estelle Bourdon, Anette V. Kristoffersen and Niels Bonde. 2016. A Roller-like Bird (Coracii) from the Early Eocene of Denmark. Scientific Reports. 6, Article number: 34050. DOI: 10.1038/srep34050 @NHM_Denmark