Browsing by Author "Lundberg, John G."
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Item The caudal skeleton of the catfishes, order Siluriformes. American Museum novitates ; no. 2398(New York, N.Y. : American Museum of Natural History, 1969) Lundberg, John G.; Baskin, Jonathan N."To achieve a better understanding of the evolution of catfishes, comparative studies of single character complexes throughout the entire order is believed to be a rewarding approach. A survey of the caudal skeleton of the Siluriformes reveals 10 basic features which, taken together, distinguish catfishes from other fishes. Of these the most diagnostic are: 1) bases of hypurals 3 and 4 fused with a distinct U[subscript]2 chordacentrum in the young and with a usually reduced second ural centrum in the adults; 2) a secondary hypurapophysis; 3) principal rays of the caudal fin fewer than 10+9, with upper principal rays equal to, or fewer than, the lower rays. Within the Siluriformes four features of the caudal skeleton are found to exhibit group specific patterns of variation and trends from primitive to advanced conditions, and may thus be useful in determining relationships: 1. In the trend from the primitive condition of six separate hypurals to the most advanced condition of complete fusion of caudal elements, various groups have reached different structural levels. In this process the sixth hypural is lost. 2. The trend toward elaboration of the sites of caudal muscle origin (hypurapophysis and secondary hypurapophysis) has involved the formation and elaboration of shelves from originally distinct projections, and a subsequent dorsal shift of these sites. 3. While the most primitive principal caudal fin ray number in siluriforms is 9+9, most groups have 8+9. The trend toward a reduction of principal rays always involves loss of an upper ray before loss of a lower so that upper principal rays are never more numerous than lower ones. 4. A separate U[subscript]2 chordacentrum is present in the young of all Ostariophysi except the Loricariidae, Plotosidae, and probably the Chacidae. In the adults of the majority of catfishes a reduced second ural centrum fused with one or more hypurals lies in the cavity on the posterior face of the compound centrum, PU[subscript]1+ U[subscript]l. In some groups the second ural centrum fuses to the compound centrum. In the Loricariidae and Plotosidae the second ural centrum is fused with PU[subscript]1+U[subscript]l, in early development. A separate, well-developed second ural autocentrum occurs in some members of four specialized and unrelated families. This is interpreted as independent redevelopment of a presumedly primitive pre-ostariophysan condition. The advanced conditions of each of these four features of the caudal skeleton tend to occur together in forms which are also regarded as advanced in most other parts of their anatomy. The primitive character states of these features tend to be retained together in a number of families, i.e. Diplomystidae, Ictaluridae, Bagridae, Cranoglanididae, Schilbeidae, Pangasiidae, and Cetopsidae. Advanced features in the caudal skeleton indicate a relationship between the Clariidae and Heteropneustidae, the Doradidae and Auchenipteridae, the Loricariidae, Astroblepidae, and Callichthyidae, and the Plotosidae and Chacidae. The siluriform caudal skeleton shares many features with that of the cypriniforms but it is consistently more advanced. The ostariophysan caudal skeleton is similar to that of the clupeoids, but it resembles the caudal skeleton of the Gonorynchiformes more closely than that of any other group"--P. 45-46.Item Early Pleistocene pre-glacial and glacial rocks and faunas of north-central Nebraska. Bulletin of the AMNH ; v. 148, article 1(New York : [American Museum of Natural History], 1972) Skinner, Morris F.; Hibbard, Claude William, 1905-1973.; Gutentag, Edwin D., 1931-; Smith, G. R.; Lundberg, John G.; Holman, J. Alan.; Feduccia, Alan.; Rich, Pat Vickers."A study of the early Pleistocene rocks of the non-glaciated region of north-central Nebraska shows that a paleovalley fill (Keim Formation, new name) that contained the Sand Draw local fauna was preglacial. The stratigraphic position of the overlying Long Pine Formation, new name, is significant because it is the first evidence of a fluvioglacial outwash in the area. Two later sets of deposits overlie the Long Pine formation: Duffy and Pettijohn formations, new names. The source of the gravel in the Long Pine Formation has been a matter of conjecture, some geologists believing it to be the Black Hills, and others the Rocky Mountains. Supporting evidence for either provenience is lacking. Devonian fossils in the Long Pine Gravel indicate that the source was to the north-northeast near Lake Winnepegosis in Manitoba. The Sand Draw local fauna, previously considered Nebraskan (first continental glacier) or Aftonian (first interstadial), correlates with other Blancan faunas, and is the most diverse and northern known of Blancan time. The following groups comprise the fauna: 42 taxa of molluscs, 14 taxa of ostracodes, 10 taxa of fishes (Chaenobryttus serratus, new species), four taxa of amphibians, 14 taxa of reptiles (Geochelone oelrichi, new species), at least 10 taxa of birds, and 35 taxa of mammals. The mammalian fauna has these new forms: a shrew, Planisorex dixonensis, new genus; four rodents, Spermophilus boothi, new species; Spermophilus meltoni, new species; Ophiomys magilli, new species; Ophiomys fricki, new species; and a mustelid, Buisnictis burrowsi, new species. Some of these fossils indicate that the early Pleistocene climate was warmer than the present one, sub-humid, with evapo-transpiration about equal to average annual precipitation. Presence of the large land tortoise, Geochelone, is evidence that the temperature seldom, if ever, dropped below 0°C. Pollen from the Keim Formation is definaitely not of glacial type"--P. 11.