Browsing by Author "Lucas, Spencer G."
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Item Lower jaw of Spathites (Ammonoidea, Acanthoceratoidea) from the Upper Cretaceous (Turonian) of New Mexico. (American Museum novitates, no. 3925)(American Museum of Natural History., 2019-04-24) Landman, Neil H.; Sealey, Paul L.; Foley, Michael P.; Lucas, Spencer G.A lower jaw was recently discovered in a limestone concretion in association with the Late Cretaceous (Turonian) ammonite Spathites puercoensis (Herrick and Johnson, 1900) from the Carlile Member of the Mancos Shale in Sandoval County, New Mexico. It is nearly complete and comprises the aptychus with a hinge along the midline. The better-preserved plate, the left (according to its position in life), is roughly triangular in shape with a broadly rounded lateral margin, a narrowly rounded posterior margin, and a weakly concave anterior margin. It is 26.2 mm wide and 33.0 mm long. Together, the left and right plates form an escutcheonlike shape that projects slightly forward at the apex. The ratio of jaw width to length (26.2 mm x 2 / 33.0 mm) equals 1.59. The aptychus consists of yellow-orange calcite and is covered with comarginal ribs that parallel the lateral and posterior margins and become more prominent toward the posterior end. It is likely that this jaw belongs to the associated ammonite and would have comfortably fit inside the body chamber, based on a comparison of the length of the jaw and the whorl height, suggesting that it functioned as a jaw, rather than as an operculum. It is the first report of an ammonite jaw in the genus Spathites and the first reported occurrence of an ammonite jaw from New Mexico.Item A new brontothere (Brontotheriidae, Perissodactyla, Mammalia) from the Eocene of the Ily Basin of Kazakstan and a phylogeny of Asian "horned" brontotheres. American Museum novitates ; no. 3439(New York, NY : American Museum of Natural History, 2004) Mihlbachler, Matthew Christian, 1972-; Lucas, Spencer G.; Emry, Robert J.; Bayshashov, Bolat.A new genus and species of 'horned' brontothere, Aktautitan hippopotamopus, from the Ily Basin of Kazakstan is described from three skulls and nearly complete postcranial material. This material occurs in fluvio-lacustrine red beds of the upper part of the Eocene (Irdinmanhan) Kyzylbulak Formation at Aktau Mountain. Trackways occurring in the overlying layers are also attributed to this new brontothere. Additionally, several misleading problems in the taxonomy of Asian horned brontotheres are addressed. We conclude that Protitan khaitshinus Yanovskaya, 1980 is a junior objective synonym of Metatitan relictus Granger and Gregory, 1943. Protitan reshetovi Yanovskaya, 1980 is removed from the genus Protitan and possibly belongs within Metatitan. Brachydiastematherium transylvanicum Böckh and Maty, 1876, the only bona fide European brontothere, known from a single partial mandible, is morphologically consistent with Metatitan Granger and Gregory, 1943. Although B. transylvanicum is known from very fragmentary material, it is possible that Metatitan is a junior synonym of Brachydiastematherium. The first cladistic phylogeny of middle and late Eocene Asian horned brontotheres was constructed with 40 characters and 17 taxa. Aktautitan, Metatitan, Brachydiastematherium, and Embolotherium form a monophyletic clade, with Aktautitan hippopotamopus as the most basal member of this clade. Within this clade, there are two monophyletic trichotomies: a Metatitan relictus, M. primus, Brachydiastematherium transylvanicum clade and a 'Metatitan' progressus, Embolotherium andrewsi, E. grangeri clade. The cladogram topology suggests that the elevated frontonasal horns shared by Aktautitan and Metatitan represent the ancestral morphology of the bizarre 'battering-ram' of Embolotherium. We extend the subfamily name Embolotheriinae to include these taxa. The unusually shortened distal limb segments of A. hippopotamopus resemble those of a phylogenetically disparate group of large ungulates that have convergently evolved hippolike limb proportions. We conclude that these limb proportions probably do not indicate a semiaquatic lifestyle, as had been previously surmised.Item On the supposed presence of Miocene Tayassuidae and Dromomerycinae (Mammalia, Cetartiodactyla) in South America. (American Museum novitates, no. 3968)(New York, NY : American Museum of Natural History, 2021-03-19) Gasparini, Germán M.; Dutra, Rodrigo Parisi; Perini, Fernando A.; Croft, Darin A.; Cozzuol, Mario A.; Missagia, Rafaela V.; Lucas, Spencer G.The earliest record of North American mammals in South America is significant for constraining the timing of intercontinental faunal interchange. At present, the oldest securely dated remains of a North American terrestrial mammal in South America pertain to a late Miocene procyonid; a few other North American mammal groups are present in late Miocene and early Pliocene outcrops in South America, but most are not recorded until the late Pliocene or Pleistocene, after the complete emergence of the Panamanian Isthmus. This long-established pattern has recently been called into question by reports of a proboscidean, two tayassuids, and a dromomerycine cervoid in supposed late Miocene deposits of Peruvian Amazon. In this contribution, we analyze the taxonomic identities and stratigraphic provenances of the tayassuid and dromomerycine fossils in detail. We conclude that these specimens are not distinguishable from modern tayassuids (Tayassu pecari and Dicotyles tajacu) and cervids, and that previous taxonomic identifications are based on misinterpretation of characters or inadequate specimens. In addition, there is insufficient evidence to support a late Miocene age for these terrestrial cetartiodactyl fossils; the stratigraphic provenance of the specimens is highly dubious, and the fossils are likely Quaternary in age.Item Vertebrate fossils and their context : contributions in honor of Richard H. Tedford. Bulletin of the AMNH ; no. 279(New York, NY : American Museum of Natural History, 2003) Flynn, Lawrence J. (Lawrence John), 1932-; Tedford, Richard H.; Novacek, Michael J.; Woodburne, Michael O.; Hunt, Robert M., Jr., 1941-; Gould, Gina C.; Gaffney, Eugene S.; Qiu, Zhanxiang.; Demere, Thomas A.; Berta, Annalisa.; Adam, Peter J.; Wang, Banyue.; Baskin, Jon A.; Van Valkenburgh, Blaire.; Sacco, Tyson.; Wang, Xiaoming, 1957-; Stevens, Margaret Skeels.; Stevens, James Bowie.; Lindsay, Everett H.; Whistler, David P.; Lander, E. Bruce.; Morgan, Gary S.; Lucas, Spencer G.; Ferrusquia-Villafranca, Ismael.; Webb, S. David (Sawney David), 1936-; Beatty, Brian Lee.; Poinar, George.; MacFadden, Bruce J.; Repenning, Charles A.; Turnbull, William D.; Lundelius, Ernest L.; Archer, Michael, 1945-; Pledge, Neville S.; Rich, Thomas H. V.; Darragh, Thomas A.; Rich, Pat Vickers.; Ye, Jie.; Meng, Jin (Paleontologist); Wu, Wenyu.; Qiu, Zhuding.; Li, Chuan-Kuei.; Winkler, Alisa J.; Downs, Will.; Holec, Peter.; Emry, Robert J.; McKenna, Malcolm C.; Lofgren, Donald L.; Tong, Haiyan.