JEPSEN, GLENN LOWELL

(b. Lead, South Dakota, 4March 1903; d. princeton, New Jersey, 15 October 1974)

Paleontology.

Jepsen was the second son of Victor Theodore Jepsen and Kittie Gallup Jepsen. He received his schooling in Rapid City, South Dakota, where his family moved when he was four years old, After a year’s study at the University of Michigan, he returned to Rapid City and taught English at the South Dakota School of Mines (1923–1925) while continuing his studies there, An early interest in fossils was nourished by visits to the American Museum of Natural History’s excavations at Agate, Nebraska, and by collecting in the Badlands. On one of these trips Jepsen met Prof. William J. Sinclair, who persuaded him to enroll at Princeton University, from which he graduated with highest honors in geology in 1927 and received his Ph.D. in 1930. He was appointed instructor in geology at Princeton in 1930; successive promotions led to the Sinclair professorship of vertebrate paleontology in 1946. Jepsen was named curator of vertebrate paleontology in 1935 and director of the Princeton Museum of Natural History in 1940; he became professor emeritus in 1971.

Jepsen married Janet E. Mayo on 14 June 1934; they had one daughter and were divorced in1953. He held memberships and offices in numerous scientific societies, including presidency of the Society of Vertebrate Paleontology in 1944 and 1945. In 1962 he received the Addison Verrill Medal of the Peabody Museum of Natural History at Yale.

While still an undergraduate at Princeton. Jepsen published on fossil collecting in the Badlands of South Dakota and on the oldest known cat; other papers on Oligocene saber-toothed cats followed in 1927 and 1933; in 1934 he described Sinclairella, a specialized insectivore from the White River beds, and separated the apatemyid insectivores from plesiadapid primates. From 1936 to 1941 Jepsen edited, with William B. Scott, a series of monographs on the mammalian fauna of the White River Oligocene, to which he contributed the section on Insectivora and Carnivora, These early studies of Oil gocene mammals influenced his attitudes toward the interpretation of phylogenetic series of fossils, the recognition of species in paleontology, and the significance of fossil vertebrates for stratigraphic correlation.

In 1927, under Sinclair, Jepsen began intensive studies of the geology and vertebrate faunas of Tertiary deposits of the Bighorn Basin in Wyoming. which he continued for more than forty years. From the Polecat Bench he described four successive mammalian assemblages below the well-known Lower Eocene fauna, the most complete sequence of fossiliferous Paleocene continental deposits known at that time in North America. The lowest mammals came from sandstones that had been mapped as Cretaceous but contained no remains of dinosaurs, In later years he commented on the inadequacy of the “absence of dinosaurs” as a criterion for the Cretaceous-Tertiary boundary.

Continued fieldwork produced additional specimens and previously unknown forms. Jepsen’s 1940 study of the multituberculates from this area proposed new methods to classify these mostly mousesized mammals. Other treasures of his Paleocene collections remained undescribed in his closely guarded cabinets at Princeton, while each year the patient search in the sparsely fossiliferous beds continued during the field seasons. Jepsen was a field paleontologist par excellence who recognized how our limited knowledge of the history of life could be improved only by a better knowledge of the fossil record. His desire for the most complete possible representation of the fauna of this important epoch in the early history of mammals kept him and his students at the difficult and tedious search for the tiny fossils.

Jepsen also was alert to exploit unusual opportunities, such as the discovery of a rich bed of Triassic fishes during excavation for the Firestone Library on the Princeton campus in 1946 and the Horner paleo-Indian buffalo-hunt site near Cody. Wyoming (1948–1962). Many accounts of the trials and pleasures of collecting fossils flowed from his pen. His most prized find was the complete articulated skeleton of an early Eocene bat (1966), to which he devoted thousands of hours of painstaking preparation under the binocular microscope.

Concern with problem of evolution and the fossil record is discernible in Jepsen’s systematic papers of the 1930’s. His 1944 essay “Phylogenetic Trees” foreshadows the synthetic theory of evolution that emerged at the 1947 princeton bicentennial conference on genetics, paleontology, and evolution. which he organized with Ernst Mayr and George G. Simpson, “selection, ‘Orthogenesis’ and the Fossil Record” (1949) traces the history of conflicting uses of the term “orthogenesis” and its relationship to concepts of irreversibility and evolutionary momentum. and conculedes that fossil vertebrates provide no valid examples of the friendly of the supposed phenomenon.

Jepsen was widely known and admired in the profession as a friendly, urbane, and witty gentleman a menticulous scholar, and an inspiring undergraduate teacher. His elegant lectures attracted many excellents student to the field of vertebrate paleontology. He placed great stress on laboratory work and fieldwork and demanded high standards of performance. He allowed his graduate students little freedom and was secretive about his specimens, which he guarded in locked cabinets.At times he could be ferocious toward his assistants and co-workers. For many years he stood in adversarial relationship to his curator.

In later years he published very little about his main collection from the Paleocene of Wyoming and often appeared despondent and withdrawn. At times he emerged from this mood to deliver animated and provocative lectures on diverse aspects of vertebrate history. His emphasis was on the incompleteness of our knowledge of past life, problems of extinction (“Dinosaurs never intended to become extinct”), and the fallacious explanations too often offered to smooth over difficulties or ignorance.

BIBLIOGRAPHY

I.Original Works.Jepsen’s, s publications on fossil vertebrates are listed in Charles L.Camp et al.comps. “Bibliographies of fossil vertebrates.”in Special Papers of the Geological society of American, 27 (1940) and 42 (1942):and Memoirs of the Geological Society of America37 (1949).57 (1953), 84 (1961), 92 (1964).117 (1968), 134 (1972), and 141 (1973).Other articles are in Jepsen’s “Princeton University Museum of Natural History 1964” (princeton.1964).appendix c(mimeographed).A selected list of titles is in Erling Dort, “Memorial to Glenn Lowell Jepsen,” in Geological society of America Memorials, 6 (1977)

On evolution. see “Phylogenetic tress.”in Transactions of the New york Academy of science. 2nd ser.6 (1944). 81–92:“selection. ‘Orthogenesis.’and the Fossil Record.” in Proceedings of the American Philosophical Society, 93 (1949).479–500;and edited with Ernst Mary and George G.Simpon. Genetics.Paleeonotoly and Evolution (Princeton. 1949).See also Futures in Retrospect and “Riddle of the Terrible Lizards”(below)

His major descriptive works on fossil vertebrates are “New Vertebrate Fossils from the Lower Eocene of the Bighorn Basin Wyoming.” in processing of the American Philosophical society. 69 (1930).117–131:“Stratigraphy and Paleontology of the Paleocene of Northeastern Park country. Wyoming,” ibid.,463–528:“A Revision of the American Apatemyidae and the Description of a New Genus. Sinclairella. from the White River Oligocene of South Dakota.” ibid., 74 (1934).287–305:“The Mammalian Fauna of the White River Oligocene.” in Transactions of the Americian Philosophical msociety. 28 (1936–1941), edited with William B. Scott; and “Paleocene Faunas of the Polecat Bench Formation, Park County.Wyoming, Part I.” in Proceedings of the American Philosophical Society, 83 (1940), 217–340.

Jepsen’s philosophy of paleontological research is presented in Futures in Retrospect (New Haven, 1962) and “Riddles of the Terrible Lizards,” in American Scientist, 54 (1964), 227–246.

See also “Fossil cCllection in the Badlands.” in Black Hills Engineer, 14 (1926).77–86:“A Natural Library.” in Bulletin of the New Jersey State Museum. no.3 (1949): “Ancient Buffalo Hunter.”in Wyoming Archaeologist. 5. no.3 (1962), 2–7;“Early Eocene Bat from Wyoming.” in Science, 154 (1966). 1333–1338; “Bat Origins and Evolution,” in William A. Wimsatt, ed., Biology of Bats. 1 (New York. 1970). 1–64.

II. Secondary Literature. Besides the Dorf memorial cited above. See Farish A. Jenkins. Jr.. “Obituary. Glenn Lowell Jepsen 1903–1974,” in News Bulletin of the Society of Vertebrate Paleontology. no. 103 (1975). 89–92; and Sheldon Judson, “Biographical Memoir; Glenn Lowell Jepsen (1903–1974),” in American Philosophical society Yearbook 1976 (1977). 85–99. The collection of fishes unearthed during construction of the Firestone Library is described in Bobb Schaeffer, “The Triassic Coelacanth Fish Diplurus, with Observations on the Evolution of the Coelacanthini,” in Bulletin of the American Museum of Natural History, 99 (1952), 25–78.

Joseph T. Gregory