Notes on palaeornithology and on a new bird from the early Tertiary North Sea region

Ella Hoch, Geologisk Museum of Copenhagen University, Øster Voldgade 5-7, 1350 Copenhagen, Denmark

Cenozoic birds are structurally modern, but Recent bird taxa can not with certainty be traced back into the Paleocene. As an example, Sphenisciformes, the penguins, a well defined order from the Eocene through to the Quaternary, may be represented by a “proto-penguin” of latest Paleocene / earliest Eocene age from South Island, New Zealand, “more primitive than any described penguin, possessing a mix of features intermediate between flying birds and the penguins” (Fordyce, in Peat 1992; see also Fordyce 1991).

Bird fossils from the latest Paleocene / earliest Eocene, marine Ølst and Fur Formations in northern Jutland, Denmark, comprise complete or incomplete single bones and interarticulated skeletal parts. These may be preserved in concretionary material or in the form of imprints in the diatomite of the Fur Formation, the so-called mo-clay or (Danish) molér. Isolated or associated with the bones are organic residues (or imprints in the diatomite) of feathers, horny sheaths of beaks and claws, and of the thickened skinstructure of the foot. Some morphological characters of the single bone parts are reminiscent of those of comparable bones in extant birds suggesting close relationship (compare, e.g., Baird & Vickers-Rich 1997). The more comprehensive parts of skeletons, however, typically exhibit character mosaics preventing assignment of the specimens to extant taxa below the ordinal level or to extant orders.

As an introduction to the presentation of a new bird fossil from the lower part of the Fur Formation or the subjacent lower Ølst Formation (Thomsen & Danielsen 1995), attention is directed to the remarkable Danish zoologist Herluf Winge (1857-1923) and his perception of nature. Mention will also be made of other Nordic contributors to (palae)ornithology.

Among several works, mainly on mammals, Winge collected all hitherto recorded information on the birds of Greenland and published it in “Conspectus Faunæ Groenlandica. Grønlands Fugle” (the Birds of Greenland) in 1898. 129 species were listed, followed by a thorough review of the ecological conditions of each species in Greenland. Winge’s informants were such personalities as Ivar Baardsøn, a mid-14th century principal at the Gardar bishop’s residence (near present day Qaqortoq, Julianehåb in West Greenland); Hans Egede, royal missionary who landed at Godthåb, the present Nuuk, in 1721; Karl Ludwig Giesecke, actor, mineral collector and from 1813 professor of mineralogy in Dublin; and the Norwegian explorer, scientist and diplomat Fridtjof Nansen – to mention just a few. Outstanding was the missionary, naturalist and linguist Otto Fabricius (1744-1822), some of whose observations of birds, published in “Fauna Groenlandica” (1780), were made on journeys with the Eskimos around Frederikshåb, now Paamiut, along the coast of West Greenland. He gave a fine description of the then extant garefowl or great auk, Alca impennis.

Herluf Winge represented Danish vertebrate palaeontology in the late 19th – early 20th century. A scholarly naturalist, besides describing extant birds and mammals in great and vivid detail, he quested for the antecedent conditions (a main work of his is the description of the late Tertiary-Quaternary mammals from the famous P.W. Lund collection of Brazilian cave fossils, 1888-1906). So he writes (1898:65), of interest to workers on the fauna and flora from the Ølst and Fur Formations, in my attempted, literal translation: “That Greenland in the Tertiary had luxuriant forests is well known. That its birdlife was correspondingly teeming can be hypothesized. Although, until now, not a single Tertiary piece of bone has been found in Greenland, it is almost demonstrated that birds occurred there in great numbers. In any case there was a continuous exchange of mammals between Europe-Asia and North America in the Tertiary, so that the mammal faunas of the Old and the New Worlds to some extent were almost similar. That the same was true for the birds has been established by finds, albeit few until now”.

Modern palaeontological and other evidence supports the presence of a geologically relatively short-lived “landbridge” connecting the biota of Greenland(-North America) with the biota of northwestern Europe around the Paleocene/Eocene boundary. Its existence may have been caused by tectonic doming associated with the onset of rifting of the Euramerican continent along East Greenland at this time. The area was formerly covered by an epicontinental seaway.

New palaeontological investigations in the accessible outcrops of contemporaneous sediments in East Greenland have added further species to the already known early Tertiary flora (Boyd 1990; Hoch 1992), supporting the impression of luxuriant forests propounded by Winge. Bones, teeth or other parts of animals have not been found in these sediments and may not be preserved. But the birds of the Ølst and Fur Formations evidence, albeit indirectly, the wealth of Greenland’s birdlife around the Paleocene/Eocene boundary, separated by a distance much shorter than at the present time.

Herluf Winge believed in morphological modification of the organisms through time, however not in Darwinian evolution. Darwin’s “On the Origin of Species” (1859) and “The Descent of Man” (1871; 2nd ed. 1874) had been translated and were available to non-anglophone Danes together with several articles on Darwinism by J.P. Jacobsen from the 1870s. Besides translator, writer and propagator of Darwinian ideas, J.P. Jacobsen (1847-1885) is father of the naturalistic psychological novel in Denmark and became influential. Winge, the naturalist, however, was and remained a Lamarckian.

Lamarckism is not solely a complex of ideas asserting the transformation of the shape of animals and plants as a reaction to their needs or desires. Lamarckism is a philosophy of life. A chapter in “Journey to Armenia” (1933) by the Russian poet Osip Mandelshtam, entitled “Around the naturalists”, begins: “Lamarck fought for the honour of living Nature, sword in hand. You think, perhaps, that he reconciled himself with Evolution as easily as the scientific savages of the 19th century? … Lamarck cried his eyes out over the magnifying glass. He is the only Shakespeare figure in Science”.

Herluf Winge had related mental features which reveal themselves in his book on Greenland’s birds as a deep care for the birds he treats. Leaving out of consideration here his more extreme Lamarckian reasonings, his descriptions are such as to create in the reader’s mind a comprehension of the organisms in nature. Such aptitude is, ideally, fundamental to the palaeontologist permitting him or her to recreate in the abstract sense extinct organisms from fossils and personal insight.

Winge (1898:39), on the ptarmigan: “Being a galliform, the ptarmigan (Lagopus mutus) no doubt belongs to the more original birds, those which in their structure preserve many features of similarity to their ancestors among the reptiles; but within Galliformes it belongs to the highest; the form of its mandible, sternum, carpometacarpus and several other elements shows it to be among those that have acquired the widest degree of the transformation characteristic of the galliforms; it belongs to those that won the greatest ability to live from the hardest digestible food such as buds and twigs, and it is among those that have acquired the foremost skills in digging. …..”.

The new early Tertiary bird, as presently exposed (incompletely prepared) on a depositional plane of a calcareous siltstone block, shows parts of the anterior body and wing skeleton and interarticulated proximal bones of the left hind limb surrounded by a residue of plumage (Fig.1). The specimen was found in a fragmented state on the beach at Sundby, the island of Mors, northern Jutland, Denmark. Posterior parts of the skeleton are preserved in unprepared siltstone (not figured), and the distal left wing elements, the neck and the skull may be preserved under remaining matrix of the figured specimen. Judging from the preservation state and from the stratification pattern of the matrix the fossil is believed to represent a more or less complete bird carcass which became embedded in low-oxygen or anoxic bottom sediments.

As exposed, the skeleton is seen in oblique dorsal view. Compressional flattening caused fragmentation of the bones to various degrees. A certain amount of pyritization has occurred in and on the skeletal elements leaving open, however, the pneumatic and other major cavities of the bones. Visible are the proximal elements of right and left folded wings interarticulated with the scapulae in natural relative positions. A ridge-like structure between them is tentatively interpreted as representing the co-ossified spinal processes of dorsal vertebrae posteriorly flanked by remnants of the ilia (pelvis). A circum-acetabular fragment of the pelvis is preserved lining the vertical fracture wall at the proximal end of the left femur. The femoral head is resting in the acetabulum. The femur interarticulates in a bent knee-joint with the fibula and tibiotarsus whose distal ends are lacking. At either side of these bones are structures representing bundles of leg muscle tendons, the more prominent of which are believed be the remains of ossified tendons (Fig.2). Such structures are rarely observed in avian fossils.

Intratendinous ossification of the long tendons of the limbs and vertebral column is found in several, not closely interrelated, extant birds (e.g. Vanden Berge & Storer 1995) and is also encountered within the dinosaurs. Particularly well-known is the tenostosis of Galliformes (including poultry and pheasants). The overall morphology and relative size of the observable bones in the new fossil bird skeleton, as expressed by their lengths (table below), is reminiscent of that in extant galliforms, such as Perdix perdix, the partridge. The ptarmigan, a strong flyer among the galliforms, has relatively longer wings (table).

Fossil bird Perdix perdix Lagopus lagopus
Femur 42 mm 52 mm 58 mm
Humerus 40 mm 48 mm 62.5 mm
Ulna 38 mm 44 mm 61 mm
Radius 34 mm 39.5 mm 54.5 mm
Scapula >36.5 mm 55.5 mm 64 mm

Table. Lengths of limb bones in the new early Tertiary bird and in single individuals of partridge and ptarmigan.

The general impression conveyed by the fossil specimen, as it is presently exposed, is that of a small groundliving bird adapted for scratching and digging in the ground in search of food, and also capable of flying as a means of short distance transportation. The detailed morphology of the humerus is different from that in the galliforms, appearing less “degenerate” and possibly reflecting a more elaborate power of flight. Further analysis awaits the complete preparation of the specimen.

Pyrite is frequent in the lower Ølst and Fur Formations (Nielsen 1994), but, according to Pedersen & Buchardt (1996), pyritized fossils have not been reported from the Fur Formation. The so-called cement-stone or (Danish) cementsten, calcareous concretions from the latter formation, grew in little compacted diatom ooze securing a nearly undisturbed, three-dimensional preservation of the embedded skeletal parts (ibid.). The pyritization and the relatively high degree of compressional fragmentation of the bones in the fossil support the impression noted by the finder, Mr Bent Søe Mikkelsen, based on the general appearance of the matrix, that the specimen derives from a stratigraphic level low in the mo-clay or below it, thus is possibly of latest Paleocene age (Thomsen & Danielsen 1995).

Literature

Boyd, A. 1990. The Thyra Ø flora: toward an understanding of the climate and vegetation during the Early Tertiary in the high Arctic. Review of Palaeobotany and Palynology 62, 189-203.

Baird, R.F. & Vickers-Rich, P. 1997. Eutreptodactylus itaboraiensis gen. et sp. nov., an early cuckoo (Aves: Cuculidae) from the Late Paleocene of Brazil. Alcheringa 21, 123-127.

Fordyce, R.E. 1991. A new look at the fossil vertebrate record of New Zealand. Pp 1191-1316 in P. Vickers-Rich, J.M. Monaghan, R.F. Baird & T.H. Rich (eds), Vertebrate palaeontology of Australasia.

Hoch, E. 1992. Palaeontology of the North Atlantic region: data and inferences on life in the Kangerdlugssuaq area before the continent severed. Pp 104-111 in C.K. Brooks, E. Hoch & A.K. Brantsen (eds), Kangerdlugssuaq Studies. Processes at a Rifted Continental Margin III.

Nielsen, O.B. 1994. Lithostratigraphy and sedimentary petrography of the Paleocene and Eocene sediments from the Harre borehole, Denmark. Aarhus Geoscience 1, 15-34.

Peat, N. 1992. Penguins from the past. Forest & Bird February, 32-34.

Pedersen, G.K. & Buchardt, B. 1996. The calcareous concretions (cementsten) in the Fur Formation: isotopic evidence of early diagenetic growth. Bulletin of the Geological Society of Denmark 43, 78-86.

Thomsen, E. & Danielsen, M. 1995. Transitional Palaeocene-Eocene ash-bearing diatomite in the eastern North Sea. Tertiary Research 15, 111-120.

Vanden Berge, J.C. & Storer, R.W. 1995. Intratendinous ossification in birds: a review. Journal of Morphology 226, 47-77.

ols_hoch1

Figure 1. Unnamed bird of latest Paleocene age from the isle of Mors, northern Denmark (MGUH.VP.3467A, Geological Museum, University of Copenhagen) (see text for discussion of age and geological environment). In its present state of incomplete preparation the specimen shows parts of the anterior body and limb skeleton in oblique dorsal view and associated left hind limb (proximal part); residues of the plumage; and remains of leg muscle tendons (see also Figure 2). Abbreviations: l. and r. indicates left and right side; fe, femur; fi, fibula; h, humerus; p, circum-acetabular fragment of pelvis; r, radius; s, scapula; te, tendons, the preservation state of which suggests intratendinous ossification; ti, tibiotarsus; u, ulna; w, distal wing bones (poorly preserved). (Photo. Ole Bang Berthelsen)

ols_hoch2

Figure 2. Detail og figure 1, showing proximal bones of left hind limb with fossilized distal tendons of musculus gastrocnemius pars externa. These tendons are believed to have been ossified. Imprints of other tendons, interpreted as proximal tendons of the same muscle and distal tendons of musculus peroneus longus, are difficult to discern on the photograph. fe, femur; fi, fibula; p, circum-acetabular fragment of pelvis; ti, tibiotarsus. Length of femur, 42 mm. (Photo: Ole Bang Berthelsen).


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