Hans C. Bjerring

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Hans Christian Bjerring (born May 30, 1931) is a Danish-Swedish vertebrate paleontologist and comparative anatomist. He has spent his career at the Swedish Museum of Natural History in Stockholm, Sweden, as curator at the Department of Palaeozoology.

Bjerring's research is mainly about the fundamental structure of the head in vertebrate evolution. His studies are based on detailed analyses of models of the crania of the sarcopterygian fishes Eusthenopteron foordi and Glyptolepis groenlandica from the Devonian as well as serially-sectioned embryos of fishes and urodeles. He belongs to the Stockholm school of paleontology together with, among others, Erik Stensiö, Erik Jarvik, Gunnar Säve-Söderbergh, and Tor Ørvig.

A recurrent theme in Bjerring’s research is that much of the vertebrate head is formed by a complex intertwining of serially homologous anatomical segments.[1] According to Bjerring, this holds both for the distribution and composition of cranial nerves,[2][3][4][5] the pharyngeal arches and their contributions to the braincase[6][7][8][9][10] organs and structures derived from the pharyngeal clefts[11] as well as muscles and cartilages at the base of the skull.[12]

Bjerring has also discussed a number of classical problems in comparative anatomy. Like Erik Jarvik, he has argued that the three ear ossicles of mammals can be derived from components of the hyoid branchial arch of osteolepiforms rather than from both the mandibular and hyoid arches as claimed by the Reichert–Gaupp theory.[13][14] Another classical problem is which one of two pairs of large dermal bones in the skull roof of sarcopterygian fishes that is homologous to the parietal bone of tetrapods. Here, Bjerring has proposed that neither alternative is correct; rather, the confusion may stem from the fact that, owing to the enormous expansion of the telencephalon in therians, one of the bone pairs has been displaced and forms the tentorium cerebelli below the skull roof.[15] He has also analysed the basic structure of the paired limbs by comparing the pectoral and pelvic fins of the Eusthenopteron with the hindleg of the Devonian tetrapod Ichthyostega and embryonic humans.[16]

Bichirs are a small group of aberrant bony fish whose anatomy has been explored by Bjerring. He identified a pair of intracranial ligaments that hold their brains in place,[17] variations in the structure of the vomer,[18] the structure of the olfactory organ in bichir embryos,[19] and reported a spinobulbar cistern resembling the cerebellomedullar cistern of mammals.[20]. Bjerring has disputed the common view that bichirs are actinopterygians, mainly because some alleged homologies between the cranial bones of bichirs and actinopterygians are dubious.[21][22]

Bjerring has named the temnospondyls Selenocara[23] and Aquiloniferus[24] from the Lower Triassic of East Greenland. His papers are richly illustrated and characterized by a pregnant, sometimes polemic style.[25] He has also written popular scientific articles.[26][27][28]


[edit] References

  1. ^ Bjerring, H. C. (1977). A contribution to structural analysis of the head of craniate animals. The orbit and its contents in 20-22 mm embryos of the North American actinopterygian Amia calva L., with particular reference to the evolutionary significance of an aberrant, nonocular, orbital muscle innervated by the oculomotor nerve and notes on the metameric character of the head in craniates. Zoologica Scripta, 6, 127–183.
  2. ^ Bjerring, H. C. (1970). Nervus tenuis, a hitherto unknown cranial nerve of the fourth metamere. Acta Zoologica, 51, 107-114.
  3. ^ Bjerring. H. C. (1971). The nerve supply to the second metamere basicranial muscle in osteolepiform vertebrates, with some remarks on the basic composition of the endocranium. Acta Zoologica, 52, 189–225.
  4. ^ Bjerring, H. C. (1972). The nervus rarus in coelacanthiform phylogeny. Zoologica Scripta, 1, 57–68.
  5. ^ Bjerring, H. C. (1993). Yet another interpretation of the coelacanthiform basicranial muscle and its innervation. Acta Zoologica, 74, 289-299.
  6. ^ Bjerring, H. C. (1993). A reflection on the evolutionary origin of the tegmen tympani. Palaeontographica (A), 228, 129-142.
  7. ^ Bjerring, H. C. (1994). The evolutionary origin and homologues of the supracochlear lamina: a contribution to our knowledge of mammalian ancestry. Acta Zoologica, 75, 359-369.
  8. ^ Bjerring, H. C. (1995). The question of a homology between the reptilian processus basipterygoideus and the mammalian processus alaris. Palaeontographica (A), 235, 79-96.
  9. ^ Bjerring, H. C. (2000). The basicranial alar process: an evolutionary perspective. In: Ichthyology: Recent Research Advances (ed. D. N. Saksena), pp. 1-10. Enfield, New Hampshire: Science Publishers.
  10. ^ Bjerring, H. C. (2002). The anuran jaw apparatus in an evolutional light. Palaeontographica (A), 266, 93-119.
  11. ^ Bjerring, H. C. (1989). Apertures of craniate olfactory organs. Acta Zoologica, 70, 71-85.
  12. ^ Bjerring, H. C. (1967). Does a homology exist between the basicranial muscle and the polar cartilage? Colloques Internationaux du Centre National de la Recherche Scientifique, 163, 223-267.
  13. ^ Bjerring, H. C. (1977). A contribution to structural analysis of the head of craniate animals. Zoologica Scripta, 6, 127–183.
  14. ^ Bjerring, H. C. (1993). A reflection on the evolutionary origin of the tegmen tympani. Palaeontographica (A), 228, 129-142.
  15. ^ Bjerring , H. C. (1995). The parietal problem: how to cut this Gordian knot? Acta Zoologica, 76, 193–203.
  16. ^ Bjerring, H. C. (1985). Facts and thoughts on piscine phylogeny. In: Evolutionary Biology of Primitive Fishes (eds. R. E. Foreman, A. Gorbman, J. M. Dodd och R. Olsson), pp. 31-57. NATO Advanced Science Institutes Series A: Life Sciences, Vol. 103. New York: Plenum Press.
  17. ^ Bjerring, H. C. (1991). Two intracranial ligaments supporting the brain of the brachiopterygian fish Polypterus senegalus. Acta Zoologica, 72, 41-47.
  18. ^ Bjerring, H. C. (1991). The question of a vomer in brachiopterygian fish. Acta Zoologica, 72, 223-232.
  19. ^ Bjerring, H. C. (1988). The morphology of the organum olfactus of a 32 mm embryo of the brachiopterygian fish Polypterus senegalus. Acta Zoologica, 69, 47-54.
  20. ^ Bjerring, H. C. (1985). Facts and thoughts on piscine phylogeny. In: Evolutionary Biology of Primitive Fishes (eds. R. E. Foreman, A. Gorbman, J. M. Dodd och R. Olsson), pp. 31-57. NATO Advanced Science Institutes Series A: Life Sciences, Vol. 103. New York: Plenum Press.
  21. ^ Bjerring H. C. (1985). The question of a presupracleithrum in brachiopterygian fishes. Acta Zoologica, 66, 171-174.
  22. ^ Bjerring, H. C. (1986). The question of a dermohyal in brachiopterygian fishes. Acta Zoologica, 67, 1-4.
  23. ^ Bjerring, H. C. (1997). The question of the Eotriassic tetrapod genus Wetlugasaurus in Greenland and thoughts on the fossa coniformis entopterygoidea. Meddelelser om Grønland, Geosciences 34, 1-25.
  24. ^ Bjerring H. C. (1999). A new amphibious tetrapod from the Greenlandic Eotriassic. Meddelelser om Grønland, Geosciences 38, 1–42.
  25. ^ Bjerring H. C. (1978). The 'intracranial joint' versus the 'ventral otic fissure'. Acta Zoologica, 59, 203-214.
  26. ^ Bjerring, H. C. (1986). Tofsstjärtfiskarnas elsinnesorgan - 'ett sjätte sinne'. Fauna och Flora, 81, 215-222. [In Swedish.]
  27. ^ Bjerring, H. C. (1988). Armar och ben i utvecklingshistorisk belysning. Fauna och Flora, 83, 58-73. [In Swedish.]
  28. ^ Bjerring, H. C. (1989). Svalg- och gälspringor - deras ursprung och vidare öden. In: Naturen berättar. Utveckling och forskning vid Naturhistoriska riksmuseet (ed. K. Engström), pp. 131-140. Stockholm: Naturhistoriska riksmuseet. [In Swedish.]
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