Sunday, 2 October 2016

Septencoracias morsensis: A Roller from the Early Eocene of Denmark.

Rollers, Coracii, are large-headed, large-beaked insectivorous Birds related to Kingfishers, Bee-eaters, Hoopoes and Hornbills. They are restricted to the Old World today, with a but two species found the tropics or subtropics, but appear to have been more widely distributed in the past. Like many living Bird-groups, they appear to have arisen shortly after the End Cretaceous extinction (before which Avian faunas were dominated by the extinct Toothed Birds), though precisely where and when is unclear due to a lack of good Bird-producing sites from the Palaeocene. Fossil Rollers have been described from the Early Eocene Messel Shale and Green River Formation of Wyoming, as well as the Late Eocene Quercy deposits of France, and fragmentary remains not described to species level from the Early Eocene of Condé-en-Brie, also in France.

In a paper published in the journal Scientific Reports on 27 September 2016, Estelle Bourdon of The Natural History Museum of Denmark and Section of Biosystematics at the University of Copenhagen, Anette Kristoffersen of the Department of Geosciences and Natural ResourceManagement at the University of Copenhagen and Niels Bonde, also of The Natural History Museum of Denmark and Section of Biosystematics at the University of Copenhagen, as well as the Fur Museum (MuserumSalling), describe a new species of Roller from the Early Eocene Fur Formation of Klovbakker Quarry on the Island of Mors, off northwestern Jutland.

The Fur Formation is a marine diatomite, i.e. a sedimentary rock formed from the tests (shells) of planktonic Diatoms; such diatomites can form in both marine and lake deposits, but only far enough from the shore that the Diatom tests are able to build up without significant input of sediments from terrestrial environments. These deposits are noted for the production of numerous Insects and Vertebrates, the later including Fish, Turtles and Birds. Importantly the Fur Formation also included numerous layers of volcanic ash, allowing very precise radiometric dating of the deposits.

The new Bird is named Septencoracias morsensis, where 'Septencoracias' means 'Northern Roller' and 'morsensis' means 'from Mors'. It is described from a single, largely-intact, three-dimensionally preserved specimen, which also has preserved stomach contents. The living Bird would have been about 25 cm in length, towards the minimum end of the size range seen in living Rollers.

Septencoracias morsensis. (a) Photograph of whole specimen. (b) 3D white light scanning of the whole specimen. (c) Interpretative drawing with damaged areas of the skull, fish remains and soft tissues represented in dark grey. Abbreviations: al1–2, phalanges of alular digit; ap, narial opening; at, atlas; ax, axis; c, cervical vertebrae; ca, carpometacarpus; cd1–7, caudal vertebrae; co, vertebral costae; cp, costal process; cr, cranium; d, damage in the skull area; dm, phalanx of minor digit; dM1, proximal phalanx of major digit; dM2, distal phalanx of major digit; ec, ectethmoid; f, femur; fi, fish remains; ft, foramina intertransversaria; fv, fish vertebra; h, humerus; if, ilioischiadic foramen; is, ischium; md, mandibula; me, mesethmoid; mx, maxilla; mI, metatarsal I; pa, palatine; pb, pubis; po, postacetabular wing of ilium; pr, preacetabular wing of ilium; pt, pterygoid; pu, uncinate process; py, pygostyle; ra, radius; rd, radial carpal bone; sc, scapula; st, soft tissues; sy, synsacrum; ta, tarsometatarsus; tb, tibiotarsus; u, ulna; ul, ulnar carpal bone; I1–2, phalanges of pedal digit I; II1–3, phalanges of pedal digit II; III1–4, phalanges of pedal digit III; IV1–5, phalanges of pedal digit IV. The ‘r’ and ‘l’ prefixes indicate right and left, respectively. Estelle Bourdon in Bourdon et al. (2016).

The specimen was found directly above an ash layer dated to 54.04 million years ago, making it about 54 million years old. This makes it the oldest known Roller, and places it directly after the Early Eocene Thermal Maximum, a time when tropical climates could be found as far north as Denmark. Since other fossil Rollers found in northerly locations in Europe and America also come from warm Eocene deposits, it is likely that the preference for hot climates seen in modern Rollers arose early in the history of the group.

 Septencoracias morsensis. (a) Skull in left lateral view. (b) Right foot in medial view. (c) Left foot in dorsal view. (d) Right humerus in cranial view. (e) Right carpometacarpus in ventral view. Bourdon et al. (2016).

The stomach contents of Septencoracias morsensis comprise the skeletons of at least two Argentinoid Fish. These Fish reached about 10 cm in size, and are very abundant in the Mors Formation, apparently having been a food source for many of the other animals found there. The consumption of Fish is outside the behaviour of modern Rollers, and may suggest some unrollerlike habits for Septencoracias morsensis. However this does not necessarily mean the Bird was capable of hunting Fish like a Kingfisher; most Birds will scavenge opportunistically when the opertunity arises, and the consumption of Fish may have been an example of such behaviour in a Roller with more conventional habits.

 Life reconstruction of Septencoracias morsensis. Salient diagnostic features of the new fossil relative to other rollers include the larger skull and the small, ovoid and dorsally positioned narial openings. Septencoracias is represented with a brownish and bluish plumage, because brownish and/or bluish feathers occur in all species of Rollers and most species of Ground-rollers, and are probably primitive within the Coracii. Estelle Bourdon in Bourdon et al. (2016).

See also...

http://sciencythoughts.blogspot.co.uk/2014/06/phorusrhacid-terror-birds-from-middle.htmlPhorusrhacid ‘Terror Birds’ from the Middle Eocene of Western Europe.                        The Phorusrhacid ‘Terror Birds’ were large, carnivorous flightless Birds that appear to have held the role of top terrestrial predators in South America throughout much of the Cenozoic. They are known to have colonized parts of North America, during...
http://sciencythoughts.blogspot.co.uk/2014/06/a-flower-visiting-bird-from-middle.htmlA flower-visiting Bird from the Middle Eocene Messel Shale of Germany.                          Several groups of modern Birds are known to feed by visiting flowers to collect nectar, and in the process serve as pollinators for the plants. Most notable are...
http://sciencythoughts.blogspot.co.uk/2014/05/fossil-romainvilliine-geese-from-late.htmlFossil Romainvilliine Geese from the Late Eocene of Xinjiang Province, China.            The Romainvilliines are an extinct group of large Waterfowl known from Late Eocene and Early Oligocene of France, Belgium and England. They... 
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