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New material and evaluation of the chronostratigraphic position of Daphoenictis tedfordi (Mammalia, Carnivora, Amphicyonidae), a cat-like carnivoran from the latest Eocene of northwestern Nebraska, USA

Grant S. Boardman and Robert M. Hunt, Jr.

Plain Language Abstract

The cat-like beardog, Daphoenictis tedfordi, is known now from 12 specimens. The specimen described herein is a nearly complete right lower jaw that further elucidates our understanding of the dental morphology and chronostratigraphic position of this species. Known specimens are confined to the latest Eocene Epoch (Chadronian land mammal age) and were discovered in Saskatchewan, Montana, Colorado, Wyoming, and Nebraska. The majority of the specimens come from Nebraska.

Resumen en Español

Materiales nuevos y evaluación de la posición cronoestratigráfica de Daphoenictis tedfordi (Mammalia, Carnivora, Amphicyonidae), un carnívoro de apariencia felina del Eoceno tardío cuspidal del noroeste de Nebraska, EE.UU.

Uno de los anficiónidos más enigmáticos, el carnívoro de apariencia felina Daphoenictis tedfordi, se conoce ahora a partir de 12 especímenes cráneo-dentales de Norteamérica. El espécimen más recientemente recuperado, una hemimandíbula derecha parcial (UNSM 27015) aquí descripta, contribuye considerablemente al conocimiento de este taxón, y rivaliza en completitud con el holotipo de la especie.

Daphoenictis tedfordi se distribuye desde Saskatchewan hasta Montana, continuando hasta Nebraska, Colorado y Wyoming, con casi el 50% de los especímenes provenientes del noroeste de Nebraska. La cronoestratigrafía y lugar geográfico del hipodigma de Nebraska es el foco de este trabajo. UNSM 27015 une los fósiles fragmentarios del hipodigma de Nebraska con el holotipo (Cypress Hills, Saskatchewan). La evidencia cronológica indica que esta especie se encuentra restringida a la edad cadroniana (Eoceno tardío). Las calibraciones astronómicas recientes aplicadas a tufitas eocenas tardías-oligocenas ubica a esta especie enteramente en el Cadroniano medio con un único individuo hallado en el biocrón Cadroniano temprano tardío.

Palabras clave: Carnivora; Anficiónido; Cadroniano; geocronología; Grandes Llanuras (Nebraska)

Traducción: Diana Elizabeth Fernández

Résumé en Français

Nouveau matériel et estimation de la position chronostratigraphique de Daphoenictis tedfordi (Mammalia, Carnivora, Amphicyonidae), un Carnivore de l'Éocène terminal du nord-ouest du Nebraska, États-Unis, morphologiquement convergent avec les félidés

Un des Carnivores amphicyonidés les plus énigmatiques, l'espèce Daphoenictis tedfordi, morphologiquement convergente avec les félidés, est à présent connue par 12 spécimens crânio-mandibulaires et dentaires en Amérique du Nord. Le spécimen le plus récemment obtenu, une hémi-mandibule partielle droite (UNSM 27015), est décrit ici. Il augmente considérablement notre connaissance de ce taxon et représente le seul spécimen aussi complet que l'holotype de l'espèce.

La répartition géographique de Daphoenictis tedfordi inclut le Saskatchewan, le Montana, le Nebraska, le Colorado, et le Wyoming, avec presque 50% des spécimens provenant du nord-ouest du Nebraska. Le point central de ce rapport concerne la chronostratigraphie et la répartition géographique de la partie de l'hypodigme provenant du Nebraska. Le spécimen UNSM 27015 permet de faire le lien entre les fossiles fragmentaires de la partie de l'hypodigme provenant du Nébraska et l'holotype (Cypress Hills, Saskatchewan). Les données chronologiques indiquent que cette espèce est restreinte à des dépôts d'âge chadronien (Éocène récent). La calibration astronomique récemment appliquée aux tuffs de l'Éocène récent et de l'Oligocène place cette espèce presque entièrement dans le Chadronien moyen avec un seul individu trouvé dans le biochrone du Chadronien ancien récent.

Mots-clés : Carnivora ; Amphicyonidae ; Éocène récent ; Chadronien ; géochronologie ; Grandes Plaines (Nebraska)

Translator: Antoine Souron

Deutsche Zusammenfassung

Neues Material und Evaluation der chronostratigrafischen Position von Daphoenictis tedfordi (Mammalia, Carnivora, Amphicyonidae), ein katzenartiger Karnivore aus dem späten Eozän von Nordwest-Nebraska, USA

Einer der rätselhaftesten amphicyoniden Karnivoren, der katzenartige Daphoenictis tedfordi, ist nun mit 12 cranio-dentalen Stücken aus Nordamerika bekannt. Das zuletzt gefundene Stück, eine partielle Hemimandibel (UNSM 27015), die hier beschrieben wird, ergänzt unser Wissen über dieses Taxon erheblich und konkurriert mit dem Holotypus der Art. Daphoenictis tedfordi ist in Saskatchewan und Montana verbreitet bis hin nach Nebraska, Colorado und Wyoming, wobei beinahe 50% der Stücke aus Nordwest-Nebraska kommen. Die Chronostratigraphie und der geografische Ort des Nebraska-Hypodigmus ist der Fokus dieses Berichts. UNSM 27015 verbindet die fragmentarischen Fossilien des Nebraska-Hypodigmus mit dem Holotypus (Cypress Hills, Saskatchewan). Chronologische Nachweise weisen darauf hin, dass diese Art auf das Chadronium (spätes Eozän) beschränkt ist. Jüngste astronomische Kalibrierung an spät-Eozänen-Oligozänen Tuffen positioniert die Art komplett in das mittlere Chadronium mit einem einzigen Individuum in der späten frühen Chadronium-Biochron.

Schlüsselwörter: Carnivora; Amphicyonide; spätes Eozän; Chadronium; Geochronologie; Great Plains (Nebraska)

Translator: Eva Gebauer

Arabic

Translator: Ashraf M.T. Elewa

 

 

FIGURE 1. Right hemimandible of Daphoenictis tedfordi (UNSM 27015) with canine, 3-m2, and broken base of p2 and single-rooted p1, middle Chadronian, Chadron Formation, section 31, T34N, R53W, Orella 7.5-minute topographic quadrangle, Sioux Co., Nebraska. 1, buccal view; 2, lingual view; 3, occlusal view.

figure 1

FIGURE 2. Topographic map of the Toadstool Park-Raben Ranch-Orella Buttes area, Sioux County, Nebraska. Chadron Formation outcrops here have yielded most fossils of Daphoenictis tedfordi in North America, including UNSM 27015 that closely compares with the Cypress Hills holotype, Saskatchewan. 1, ravine in sec. 31, T34N, R53W, site of the Raben Ranch local fauna and probable collecting locality of UNSM 27015; 2, stratotype of the Big Cottonwood Creek Member of the Chadron Formation (Terry and LaGarry, 1998); 3, approximate limit of the “1 mile northwest of UNSM collecting district Sx-41,” stated in the UNSM locality designation for UNSM 27015 (see Site of Collection); RAM 4906 and RAM 4907, Ray Alf Museum sites where D. tedfordi was collected.

figure 2

FIGURE 3. Stratigraphic section of the Chadron Formation including RAM Locality 4906, SE1/4, sec. 31, T34N, R53W, Sioux Co., Nebraska, measured by R.H. Tedford in 1964. Note the LPW (Lower Purple-White) and UPW (Upper Purple-White) ashes relative to the faunal horizon.

figure 3

FIGURE 4. Stratigraphic section of the Chadron Formation from Ostrander (1985, fig. 5) in W1/2, NE1/4, sec. 31, T34N, R53W, with the Raben Ranch local fauna and the fossiliferous interval above and below the “pond limestone” that corresponds to the stratigraphic interval that produced the UNSM assemblage with Daphoenictis.

figure 4

 

Chronologic history of the Daphoenictis hypodigm: 1937-1980

In 1950, paleontologist Raymond Alf and students from the Webb School, Claremont, California, explored Chadron Formation badlands northwest of Toadstool Park in the NW corner, SE1/4, sec. 5, T33N, R53W, Sioux County, Nebraska (Figure 2). Among the numerous Chadronian mammals collected was a partial hemimandible with cat-like dentition (UCMP 311018, previously UCR 11018), which at that time was referred to the felid “cf. Pseudaelurus ” (Hough and Alf, 1956). Also, two mandibular fragments with dentition (UCMP 311021, 311022, previously UCR 11021, 11022), representing this same carnivoran, were collected from Chadron Formation outcrops ~1 mile northwest of the previous locality in the SE1/4, sec. 31, T34N, R53W, but these were neither identified nor described.

A few additional specimens of this enigmatic cat-like species accumulated in Chadronian collections of the Frick Laboratory (AMNH) in the 1950s but failed to attract notice. A mandibular fragment with m2 and damaged m1 (F:AM 25242) was found by M.F. Skinner in 1953 at Brecht Ranch, southwest of Chadron, Nebraska. In 1958, a second mandibular fragment with m1 trigonid and m2-m3 (F:AM 76205) and a posterior cranium were collected in Chadronian White River beds at Flagstaff Rim, in central Wyoming, by Skinner, T. Galusha, R. J. Emry, and C. Elfgren. The cranium and mandibular fragment, found together, were given a common field number (BH28-650) and considered to belong to the same individual.

Identification of this carnivoran came about through publication of a hemimandible with p3-m2 (NMC 9205) recovered in 1937 from Chadronian deposits of the Cypress Hills, Saskatchewan (Russell, 1972). Russell assigned the jaw to the “canid” Daphoenus. Importantly, the molars of the Flagstaff Rim jaw and the teeth of the previously unrecognized jaw fragments from Nebraska were seen to match the intact teeth in Russell’s Cypress Hills jaw, and it was then discovered that the Flagstaff Rim cranium exhibited amphicyonid basicranial features (Hunt, 1974). As a result the fossils were assigned to a new genus and species, Daphoenictis tedfordi, and placed in the Amphicyonidae. The Cypress Hill jaw was designated the species holotype.

No upper teeth of this carnivoran were known until, in the early1970s, a high-altitude outlier of the White River Group in northwest Wyoming produced a Chadronian fauna (McKenna, 1972) that included a partial maxilla with a tall dagger-like P3 (AMNH 56351). This distinctive P3 was later recognized in another maxilla that preserved P3-M1 (USNM 214642) from Chadronian sediments at Flagstaff Rim. Because its upper teeth evidenced the trenchant form suggested by the lower dentition, the maxilla was referred to Daphoenictis (Emry and Hunt, 1980). These authors also included in Daphoenictis an unrecognized isolated m1 from Chadronian beds at Pipestone Springs (Main Locality), Montana, collected in 1948 (USNM 215031).

The intact hemimandible of Daphoenictis tedfordi (UNSM 27015) described in this report was discovered in 1962 near the locations in northwestern Nebraska where Raymond Alf collected the specimens in 1950 later referred to Daphoenictis. With the addition of UNSM 27015, the Chadronian badlands of the White River Group northwest of Toadstool Park become the principal geographic area yielding fossils of Daphoenictis. This district includes the Chadronian Raben Ranch local fauna preserving one of the few North American occurrences of latest Eocene multituberculates and other relict early Paleogene taxa (Ostrander, 1983, 1984, 1985).

 

gsbGrant S. Boardman
Department of Physics, Astronomy and Geology
Berry College
Mount Berry, Georgia 30149
USA
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Dr. Boardman is a vertebrate paleontologist and stable isotope geochemist. He received his Ph.D. in Geology from the University of Nebraska in 2013, and has been a Visiting Assistant Professor of Geology at Berry College (Mount Berry, Georgia) since leaving Nebraska. Dr. Boardman’s research centers on late Paleogene ungulates and problems in paleoclimatology and paleoecology that can be addressed with the use of stable isotopes.

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rhRobert M. Hunt, Jr.
Department of Earth and Atmospheric Sciences
University of Nebraska
Lincoln, Nebraska 68588
USA
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Dr. Hunt is a vertebrate paleontologist and emeritus professor in the Department of Earth and Atmospheric Sciences, University of Nebraska. His research has examined the paleontology and geologic setting of mid-Cenozoic nonmarine deposits and the paleobiology of mammalian carnivorans.

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