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.

Denmark constitutional monarchy in Europe

Denmark, officially the Kingdom of Denmark, is a Nordic country and the southernmost of the Scandinavian nations. Denmark lies southwest of Sweden and south of Norway, and is bordered to the south by Germany. The Kingdom of Denmark also comprises two autonomous constituent countries in the North Atlantic Ocean: the Faroe Islands and Greenland. Denmark proper consists of a peninsula, Jutland, and an archipelago of 443 named islands, with the largest being Zealand, Funen and the North Jutlandic Island. The islands are characterised by flat, arable land and sandy coasts, low elevation and a temperate climate. Denmark has a total area of 42,924 km2 (16,573 sq mi), land area of 42,394 km2 (16,368 sq mi), and the total area including Greenland and the Faroe Islands is 2,210,579 km2 (853,509 sq mi), and a population of 5.8 million.

Sweden constitutional monarchy in Northern Europe

Sweden, officially the Kingdom of Sweden, is a Scandinavian Nordic country in Northern Europe. It borders Norway to the west and north and Finland to the east, and is connected to Denmark in the southwest by a bridge-tunnel across the Öresund, a strait at the Swedish-Danish border. At 450,295 square kilometres (173,860 sq mi), Sweden is the largest country in Northern Europe, the third-largest country in the European Union and the fifth largest country in Europe by area. Sweden has a total population of 10.2 million of which 2.4 million has a foreign background. It has a low population density of 22 inhabitants per square kilometre (57/sq mi). The highest concentration is in the southern half of the country.

Vertebrate subphylum of chordates

Vertebrates comprise all species of animals within the subphylum Vertebrata. Vertebrates represent the overwhelming majority of the phylum Chordata, with currently about 69,276 species described. Vertebrates include the jawless fishes and jawed vertebrates, which include the cartilaginous fishes and the bony fishes. The bony fishes in turn, cladistically speaking, also include the tetrapods, which include amphibians, reptiles, birds and mammals.

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.

Head cephalic part of an animal

A head is the part of an organism which usually includes the ears, brain, forehead, cheeks, chin, eyes, nose, and mouth, each of which aid in various sensory functions such as sight, hearing, smell, and taste, respectively. Some very simple animals may not have a head, but many bilaterally symmetric forms do, regardless of size.

Evolution Change in the heritable characteristics of biological populations over successive generations

Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes that are passed on from parent to offspring during reproduction. Different characteristics tend to exist within any given population as a result of mutation, genetic recombination and other sources of genetic variation. Evolution occurs when evolutionary processes such as natural selection and genetic drift act on this variation, resulting in certain characteristics becoming more common or rare within a population. It is this process of evolution that has given rise to biodiversity at every level of biological organisation, including the levels of species, individual organisms and molecules.

<i>Eusthenopteron</i> species of fish (fossil)

Eusthenopteron is a genus of prehistoric sarcopterygian which has attained an iconic status from its close relationships to tetrapods. The name derives from two Greek stems—eustheno- "strength" and -pteron "wing" and thus "strongly developed fins". Early depictions of this animal show it emerging onto land; however, paleontologists now widely agree that it was a strictly aquatic animal. The genus Eusthenopteron is known from several species that lived during the Late Devonian period, about 385 million years ago. Eusthenopteron was first described by J. F. Whiteaves in 1881, as part of a large collection of fishes from Miguasha, Quebec. Some 2,000 Eusthenopteron specimens have been collected from Miguasha, one of which was the object of intensely detailed study and several papers from the 1940s to the 1990s by paleoichthyologist Erik Jarvik.

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]

Homology (biology) existence of shared ancestry between a pair of structures, or genes, in different taxa

In biology, homology is the existence of shared ancestry between a pair of structures, or genes, in different taxa. A common example of homologous structures is the forelimbs of vertebrates, where the wings of bats, the arms of primates, the front flippers of whales and the forelegs of dogs and horses are all derived from the same ancestral tetrapod structure. Evolutionary biology explains homologous structures adapted to different purposes as the result of descent with modification from a common ancestor. The term was first applied to biology in a non-evolutionary context by the anatomist Richard Owen in 1843. Homology was later explained by Charles Darwin's theory of evolution in 1859, but had been observed before this, from Aristotle onwards, and it was explicitly analysed by Pierre Belon in 1555.

Cranial nerves nerves that emerge directly from the brain and the brainstem

Cranial nerves are the nerves that emerge directly from the brain, in contrast to spinal nerves. 10 of the cranial nerves originate in the brainstem. Cranial nerves relay information between the brain and parts of the body, primarily to and from regions of the head and neck.

Branchial arch

Branchial arches, or gill arches, are a series of bony "loops" present in fish, which support the gills. As gills are the primitive condition of vertebrates, all vertebrate embryos develop pharyngeal arches, though the eventual fate of these arches varies between taxa. In jawed fish, the first arch develops into the jaws, the second into the hyomandibular complex, with the posterior arches supporting gills. In amphibians and reptiles, many elements are lost including the gill arches, resulting in only the oral jaws and a hyoid apparatus remaining. In mammals and birds, the hyoid is still more simplified.

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]

Comparative anatomy

Comparative anatomy is the study of similarities and differences in the anatomy of different species. It is closely related to evolutionary biology and phylogeny.

Erik Jarvik paleontologist

Anders Erik Vilhelm Jarvik was a Swedish paleontologist who worked extensively on the sarcopterygian fish Eusthenopteron. In a career that spanned some 60 years, Jarvik produced some of the most detailed anatomical work on this fish, making it arguably the best known fossil vertebrate.

A dermal bone or membrane bone is a bony structure derived from intramembranous ossification forming components of the vertebrate skeleton including much of the skull, jaws, gill covers, shoulder girdle and fin spines rays (lepidotrichia), and the shell. In contrast to endochondral bone, dermal bone does not form from cartilage that then calcifies, and it is often ornamented. Dermal bone is formed within the dermis and grows by accretion only – the outer portion of the bone is deposited by osteoblasts.

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]

Bichir family of fishes

Bichirs and the reedfish comprise Polypteridae, a family of archaic-looking ray-finned fishes and the only family in the order Polypteriformes.

A ligament is the fibrous connective tissue that connects bones to other bones. It is also known as articular ligament, articular larua, fibrous ligament, or true ligament. Other ligaments in the body include the:

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]

Selenocara is an extinct genus of mastodonsauroid temnospondyl. The type species is Selenocara groenlandica, described by Gunnar Säve-Söderbergh in 1935 on the basis of skull bones from the Lower Triassic Wordie Creek Formation of Greenland. Säve-Söderbergh originally described it as a new species of Wetlugasaurus.

The Triassic is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.9 million years ago (Mya), to the beginning of the Jurassic Period 201.3 Mya. The Triassic is the first and shortest period of the Mesozoic Era. Both the start and end of the period are marked by major extinction events.

Greenland autonomous country within the Kingdom of Denmark

Greenland is an autonomous constituent country of the Kingdom of Denmark between the Arctic and Atlantic oceans, east of the Canadian Arctic Archipelago. Though physiographically a part of the continent of North America, Greenland has been politically and culturally associated with Europe for more than a millennium. The majority of its residents are Inuit, whose ancestors began migrating from the Canadian mainland in the 13th century, gradually settling across the island.

Related Research Articles

Chordate phylum of animals

A chordate is an animal constituting the phylum Chordata. During some period of their life cycle, chordates possess a notochord, a dorsal nerve cord, pharyngeal slits, an endostyle, and a post-anal tail: these five anatomical features define this phylum. Chordates are also bilaterally symmetric; and have a coelom, metameric segmentation, and a circulatory system.

Craniate Clade of chordates

A craniate is a member of the Craniata, a proposed clade of chordate animals with a skull of hard bone or cartilage. Living representatives are the Myxini (hagfishes), Hyperoartia, and the much more numerous Gnathostomata. Formerly distinct from vertebrates by excluding hagfish, molecular and anatomical research in the 21st century has led to the reinclusion of hagfish, making living craniates synonymous with living vertebrates.

<i>Polypterus</i> genus of fishes

Polypterus is a genus of freshwater fish in the bichir family (Polypteridae) of order Polypteriformes. The type species is the Nile bichir. Fishes in this genus live in various areas in Africa. Polypterus is the only known vertebrate to have lungs, but no trachea.

Batrachomorpha subclass of tetrapods, whose living forms include frogs, toads, salamanders, newts and caecilians

Batrachomorpha is a name traditionally given to recent and extinct amphibians that are more closely related to modern amphibians than they are to reptiles. It most often includes the extinct groups Temnospondyli and Lepospondyli. The first tetrapods were all amphibians in the physiological sense that they laid their eggs in water, and are colloquially sometimes refereed to as labyrinthodonts or stegocephalians. In this scheme, batrachomorphs composed one branch of these early amphibians, while the reptiliomorphs composed the other. While the actual phylogeny of the modern amphibians is not well understood, their ancestors are descended from one line of batrachomorphs. All other living tetrapods are descended from one branch of reptiliomorphs, the amniotes. Amniotes achieved dominance, while all other reptiliomorphs and most batrachomorphs have gone extinct.

<i>Panderichthys</i> genus of fishes (fossil)

Panderichthys is a genus of extinct sarcopterygian from the late Devonian period, about 380 Mya. Panderichthys, which was recovered from Frasnian deposits in Latvia, is represented by two species. P. stolbovi is known only from some snout fragments and an incomplete lower jaw. P. rhombolepis is known from several more complete specimens. Although it probably belongs to a sister group of the earliest tetrapods, Panderichthys exhibits a range of features transitional between tristichopterid lobe-fin fishes and early tetrapods. It is named after the German-Baltic paleontologist Christian Heinrich Pander. A recent study uncovered tetrapod tracks dating back to before the appearance of Panderichthys in the fossil record, which suggests that Panderichthys is not a transitional fossil, but nonetheless shows the traits that evolved during the fish-tetrapod evolution

<i>Hynerpeton</i> basal carnivorous tetrapod of the Late Devonian

Hynerpeton is an extinct genus of early four-limbed vertebrate that lived in the rivers and ponds of Pennsylvania during the Late Devonian period, around 365 to 363 million years ago. The only known species of Hynerpeton is H. bassetti, named after the describer's grandfather, city planner Edward Bassett. Hynerpeton is known for being the first Devonian four-limbed vertebrate discovered in the United States, as well as possibly being one of the first to have lost internal (fish-like) gills.

<i>Tiktaalik</i> genus of fishes (fossil)

Tiktaalik is a monospecific genus of extinct sarcopterygian from the Late Devonian Period, about 375 Ma, having many features akin to those of tetrapods.

<i>Gerrothorax</i> genus of reptiles (fossil)

Gerrothorax is an extinct genus of temnospondyl amphibian from the Triassic period of Greenland, Germany, Sweden, and possibly Thailand. It is known from a single species, G. pulcherrimus, although several other species such as G. pustuloglomeratus have been named in the past.

Edward B. 'Ted' Daeschler is an American vertebrate paleontologist and Associate Curator and Chair of Vertebrate Biology at the Academy of Natural Sciences in Philadelphia. He is a specialist in fish paleontology, especially in the Late Devonian, and in the development of the first limbed vertebrates. He is the discoverer of the transitional fossil tetrapod Hynerpeton bassetti, and a Devonian fish-like specimen of Sauripterus taylorii with fingerlike appendages, and was also part of a team of researchers that discovered the transitional fossil Tiktaalik.

A digit is one of several most distal parts of a limb, such as fingers or toes, present in many vertebrates.

Cranial kinesis is the term for significant movement of skull bones relative to each other in addition to movement at the joint between the upper and lower jaw. It is usually taken to mean relative movement between the upper jaw and the braincase.

<i>Marsdenichthys</i> genus of Sarcopterygii

Marsdenichthys is an extinct genus of Devonian tetrapodomorph. Fossils have been found from Mount Howitt in Victoria, Australia from strata that are Givetian-Frasnian in age. Mount Howitt is an important site that has been the source of many tetrapodomorph fossils, including Beelarongia and Howittichthys, both of which were first described from the locality.

Ganoine

Ganoine or ganoin is a glassy, often multi-layered mineralized tissue that covers the scales, cranial bones and fin rays in some non-teleost ray-finned fishes, such as gars, bichirs, and coelacanths. It is composed of rod-like, pseudoprismatic apatite crystallites, with less than 5% of organic matter. Existing fish groups featuring ganoin are bichirs and gars, but ganoin is also characteristic of several extinct taxa. It is a characteristic component of ganoid scales.

Cosmine is a spongy, bony material that makes up the dentine-like layers in the scales of the lobe-finned fishes of the class Sarcopterygii. Fish scales that include layers of cosmine are known as cosmoid scales.

Innovations conventionally associated with terrestrially first appeared in aquatic elpistostegalians such as Panderichthys rhombolepis, Elpistostege watsoni, and Tiktaalik roseae. Phylogenetic analyses distribute the features that developed along the tetrapod stem and display a stepwise process of character acquisition, rather than abrupt. The complete transition occurred over a period of 25 million years beginning with the tetrapodomorph diversification in the Middle Devonian.

Sam Giles paleontologist

Sam Giles is a palaeobiologist at the University of Birmingham. Her research combines modern imaging with fossils to understand the evolution of life and in 2015 "rewrote" the vertebrate family tree. She was a 2017 L'Oréal-UNESCO Rising Star and won the 2019 Geological Society of London Lyell Fund.

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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