Temnocyon fingeruti Hunt 2011
- Dataset
- Evolution Of Large Carnivores During The Mid-Cenozoic Of North America: The Temnocyonine Radiation (Mammalia, Amphicyonidae)
- Rank
- SPECIES
- Published in
- Hunt, Robert M. (2011): Evolution Of Large Carnivores During The Mid-Cenozoic Of North America: The Temnocyonine Radiation (Mammalia, Amphicyonidae). Bulletin of the American Museum of Natural History 2011 (358): 1-153, DOI: 10.1206/358.1, URL: http://www.bioone.org/doi/abs/10.1206/358.1
Classification
- kingdom
- Animalia
- phylum
- Chordata
- class
- Mammalia
- order
- Carnivora
- family
- Amphicyonidae
- genus
- Temnocyon
- species
- Temnocyon fingeruti
description
DESCRIPTION: The skull of NM 280 / 61 is elongate (basilar length, 25 cm, table 7) as are the known skulls of T. ferox and T. subferox but differs from the short, broad skull of Delotrochanter oryktes. Cranial size and proportions are similar to those of T. ferox except for the much greater frontal sinus inflation and entirely different form of P 4 – M 2 and p 4 – m 2 in T. fingeruti. Despite smaller size, a narrower snout and clearly dissimilar dentition, the profile of NM 280 / 61 compares with the skull form of Mammacyon ferocior. NM 280 / 61 approximates a large male wolf (Canis lupus) in rostral proportions and palatal dimensions but shows a longer postorbital cranium with broader basicranium, greater frontal sinus inflation, and smaller braincase volume. Although the teeth are similar in occlusal dimensions to those of a wolf, NM 280 / 61 has larger canines, more robust premolars, with a proportionately smaller shearing m 1 and a longer m 2 – 3 crushing platform. As with other John Day crania, sutures and anatomical detail are obscured by diagenetic alteration of bone. The orbital region preserves the orbital foramina nested in the elongate depression previously descibed for T. altigenis (UCMP 1549). An orbital foramen, sphenorbital fissure, and anterior opening for the alisphenoid canal (the foramen rotundum opening internally into the canal) are situated as in that plesiomorphic species, and it is apparent that this anatomical pattern is common to all temnocyonines where the orbital region has been preserved. The basicranium and auditory region are exceptional and are discussed in the section on Basicranial Anatomy. The mandible is gracile and slender (depth beneath m 1, 32 mm; below p 2, 27 mm) with toothrow length (p 1 – m 3) of 110 mm. These teeth are worn, indicating a mature but not aged individual; the canines, particularly the lower pair, reflect some damage, with the right lower canine beveled to a rounded stub suggesting it had been broken and smoothed by abrasion during life. Lower incisors of temnocyonines rarely survive but are preserved in T. fingeruti. The i 1 – 3 were quite small; there is little room (, 1 cm) for them between the canines. During feeding these incisors would have been of little use. A somewhat larger i 3 (length, 6.4 mm; width, 3.7 mm) contrasts with i 2 (length, 5.9 mm; width, 2.9 mm) represented only by a broken root. There is no evidence of i 1 that if present was placed in front of and below i 2. The canine measures, 19 mm in length ,, 10 mm in width, measured at the enamel base; the symphyseal width is narrow, only 30 mm measured across the base of the canines. The p 1 is a small, peglike tooth (length, 6.9 mm; width, 4.0 mm) and is much worn. The p 2 (length, 12.1 mm; width, 5.6 mm) is much larger than p 1 with its posterior slope somewhat longer than the anterior slope. A thin enamel ridge travels down both the anterior face to the anterolingual corner and the posterior face to the posterolabial cingulum. There are no accessory cusps. The p 3 (length, 15.3 mm; width, 6.6 mm) is a larger replica of p 2 with a small posterior cingular shelf and a tiny basal cusp; the shelf is indented by wear on the left p 3, less so on the right. There are no evident accessory cusps. The p 4 (length, 19.3 mm; width, 8.7 mm) is quite long relative to p 3. There is a prominent labially situated posterior accessory cusp above a cingular shelf. The principal cusps of p 2 – 4 are worn flat by apical abrasion. The p 2 – 3 are not tall relative to those in the large durophagous species of Mammacyon and Delotrochanter. They compare with p 2 – 4 of T. altigenis but are much larger teeth. The m 1 (length, 24.7 mm; width, 10.6 mm) is a narrow, shearing carnassial that in this individual shows apical wear on trigonid and talonid cusps. Although the mandible of T. fingeruti and the wolf are of similar size, m 1 is much smaller and the premolars larger in the beardog. The paraconid is mesially advanced to form a shear plane with the tall protoconid. A prominent metaconid is situated posterolingual to the protoconid. The talonid is filled by a large hypoconid; this cusp does not attain the height of the paraconid as in Mammacyon and Delotrochanter. A sinuous labial cingulum is present on the talonid but subdued on the trigonid. There is no entoconid yet a very narrow lingual talonid shelf occurs. The elongate m 2 (length, 14.8 mm; width, 8.9 mm) displays a low paraconid anterolingual to the taller, rather blunt, labial protoconid; a small metaconid is present. The m 2 talonid has a low, more centrally placed hypoconid; there is no entoconid. The rectangular m 3 (length, 9.8 mm; width, 7.1 mm) has a distinct trigonid somewhat elevated above the talonid. The protoconid is connected by a curvilinear ridge to a very small metaconid. A low hypoconid is the only talonid cusp. A cingulum surrounds both the m 2 and m 3. The upper dentition is one of the most complete among temnocyonines. Both toothrows are intact: width of the transverse incisor row, 24.7 mm; width between canines, 24.9 mm; a narrow palate between P 1 – 2 (25.9 mm) widens between P 3 – 4 (36.8 mm), and reaches its maximum breadth (59 mm) between the embrasures of the P 4 – M 1 pair. Palatal length measured from I 1 along the midline to the posterior border of the palate is 13 cm. Toothrow length from P 1 – M 2 is 92.1 mm (P 2 – 4, 58.7 mm; M 1 – 2, 27.3 mm). I 1 (length, 5.5 mm; width, 2.4 mm) and I 2 (length, 6.5 mm; width, 2.7 mm) are quite small, their apices worn flat. I 3 is larger (length, 10.0 mm; width, 5.4 mm), heavily worn to a stub. There are short diastemata between I 3 and the canine (4.8 mm), between C – P 1 (3.6 mm), P 1 – 2 (3.9 mm), P 2 – 3 (7.0 mm), and P 3 – 4 (2.0 mm). The small I 3 of T. fingeruti contrasts in size with the huge I 3 s of D. oryktes and M. ferocior. Wear on the upper incisors of T. fingeruti shows that they occluded with i 1 – 3 in a grasping or nipping role. The canine (length, 17.3 mm; width, 12.3 mm, measured at enamel-dentine contact) is broken and worn, but it was more robust than a wolf canine from a similarly sized skull. P 1 is a small peglike tooth (length, 7.6 mm; width, 4.7 mm) with a low vertical anterior face and a posterior slope lacking accessory cusps. P 2 is a larger triangular tooth (length, 13.4 mm; width, 5.7 mm) with a posterior slope slightly longer than the anterior face. There are no accessory cusps. P 3 is somewhat larger (length, 16.1 mm; width, 7.0 mm) than P 2 with anterior and posterior faces as in P 2 but having a broader heel than P 2. Heavy wear on the posterior slope prevents identification of an accessory cusp but it was probably not present. P 4 is a short carnassial (length, 22.0 mm; width, 15.4 mm) with a prominent shear plane beveling the lingual faces of paracone and metastylar blade. A blunt protocone is situated directly lingual to the paracone. The posterior half of the protocone occluded against the m 1 paraconid, evidenced by an elliptical wear facet, whereas the anterior face of the protocone was abraded by the p 4 accessory cusp. Labial and lingual cingula are present but the anterior face of P 4 and the adjacent heel of P 3 were deeply worn by the principal and accessory cusps of the large p 4. The principal cusps of P 1 – 3 exhibit flat apical wear facets. This blunting of cusps also occurred on the M 1 paracone and metacone (with minor apical wear on M 2 paracone) and the paracone and metastylar blade of P 4. P 4 wear included a shear component that extended posteriorly along the lingual faces of the M 1 paracone-metacone and M 2 paracone, evidenced by shear facets on these molars. M 1 (length, 17.1 mm; width, 22.4 mm) retains a plesiomorphic occlusal form little different from that of T. altigenis. The paracone and slightly smaller metacone are bordered by a labial cingulum with developed parastyle. The cingulum thins on the margins of M 1 at the level of the protocone basin but then thickens to form a prominent posterolingual cingulum around the protocone, which does not equal the strongly swollen M 1 lingual cingula observed for Mammacyon and Delotrochanter. The protocone is situated near the anterior margin of the tooth and is more sharp-crested and less bunodont. A preprotocrista runs anterolabially from the protocone to the anterior cingulum, and a short weak postprotocrista intersects the posterior cingulum. M 2 (length, 9.6 mm; width, 17.4 mm) is smaller and of a different form than M 1; the anterior margin is convex, the posterior concave. The paracone is much larger than the low reduced metacone yet the lingual face of the two cusps forms a vertical shear plane. The labial and anterior sides of M 2 are bordered by a cingulum that thickens to form a wide lingual swelling. A minute protocone situated in the center of an enamel flat retains an anterolabially directed preprotocrista and a tiny postprotocrista. The posterior margin of M 2 is worn by the anterior face of m 3 since there is no M 3. In T. fingeruti, crushing / shearing occlusion was accomplished by p 4 – m 2 and P 3 – M 2. More anterior teeth served to grasp the food and, via the action of the tongue, passed it back to the carnassials and molars.
diagnosis
DIAGNOSIS: Wolf-sized species of Temnocyon (basilar skull length, 25 cm), distinguished from T. altigenis and T. subferox by much larger size, from T. macrogenys by smaller size; differs from similarly sized T. ferox by greater inflation of the frontal paranasal sinuses (relative to braincase width, table 7) and by different form and proportions of p 4 – m 2 and M 1 – 2 (tables 2, 3), including a more lingually extended M 1 – 2 with less expansion of M 1 protocone region (ratio A / B, table 6), a much larger M 2 and m 2, a longer m 2 (ratio E / F), and by a more robust, wider p 4. Temnocyon fingeruti differs from T. percussor in its much smaller M 1 (in the upper dentition of T. percussor only M 1 survives), more elongate m 1 – 2, stronger m 1 metaconid, and larger, rectangular m 2 with vestigial metaconid and more developed paraconid, and by the p 4 / m 1 ratio (0.78 in T. fingeruti vs. 0.84 in both T. percussor and T. ferox). Temnocyon fingeruti differs from T. altigenis, T. subferox, and probably T. ferox in P 4 proportions (ratio C / D, table 6); P 4 is not known in T. percussor and T. macrogenys. REFERRED SPECIMENS: None.
discussion
DISCUSSION: The skull and mandibles of NM 280 / 61 represent one of the bestpreserved North American temnocyonines. The species preserves the most wolflike dentition of any temnocyonine and exhibits an attritional dental wear pattern much like that known for Canis lupus. Despite some crushing of the skull that collapsed the zygomata and shifted the rostrum laterally relative to the frontal region, the cranium, teeth, and basicranial anatomy are exceptional. NM 280 / 61 demonstrates that a plesiomorphic temnocyonine dental pattern continued in the Pacific Northwest to very near the Oligocene-Miocene boundary, currently placed at 23.03 Ma (Gradstein et al., 2004). Because NM 280 / 61 occurs only, 20 m above a radiometric date of 23.8 Ma, its stratigraphic level places it in the latest Oligocene. NM 280 / 61 is the stratigraphically youngest John Day temnocyonine yet discovered; whether Great Plains early Miocene temnocyonines such as T. macrogenys and Delotrochanter existed in the Pacific Northwest is not known. Absence of early Miocene temnocyonines in the John Day beds could simply reflect the more limited representation of sediments of that age, which are often unfossilferous. However, large daphoenine and amphicyonine beardogs have been found in early Miocene John Day strata of early Hemingfordian age (Borocyon, Amphicyon: Hunt and Stepleton, 2004), suggesting that they replaced the temnocyonines.
distribution
DISTRIBUTION: Latest Oligocene, late midArikareean, John Day Formation, Wheeler County, Oregon.
etymology
ETYMOLOGY: The species name recognizes Michael Fingerut, who discovered and collected the holotype in the Balm Creek drainage, north-central Oregon.
materials_examined
TYPE: NM 280 / 61, a complete skull and lower jaws in articulation, the rostrum offset, 3 cm from the posterior cranium by sediment deformation after burial; both left and right I 1 – 3, C, P 1 – 4, M 1 – 2 and left i 3, c, p 2 – 4, m 1 – 3, right c, p 1 – 4, m 1 – 3, from the Haystack Valley Member (revised), John Day Formation, Oregon, Lower Beardog Section, E 1 / 2, NE 4, SW 4, SW 4, sec. 27, T 8 S, R 25 E, Kimberly 7.5 - minute quadrangle, from 96 ft stratigraphic level in appendix 1 – 6, Hunt and Stepleton (2004: 81); 62 ft above a radioisotopically dated horizon at, 23.8 Ma.
Name
- Homonyms
- Temnocyon fingeruti Hunt 2011