GBIF Taxonomic Backbone & Wikipedia Registry Profile
DESCRIPTION: ACM 34 – 41 — Loomis (1936) only briefly described the upper dentition of this fine skull, and did not mention the wellpreserved basicranium. It is one of only three temnocyonine skulls in which some part of the auditory bulla is preserved, in this case a crescentic anterior portion formed largely or entirely by the ectotympanic (see Basicranial Anatomy). The left maxilla retains the canine, P 2 – M 2; on the right, I 3, P 2 – M 2. An alveolus for a single-rooted P 1 is present on the right, but other alveoli are distorted. The upper canine, blunted at the tip from wear, measures, 45 mm in length from the tip to the enamel base on the labial face. There is no evident wear groove produced by the lower canine. At the enamel base the canine measures 22.1 mm in anteroposterior length and 14.1 mm in width. The alveolus of P 1 measures 8.7 mm in length, 5.4 in width, and has been slightly distorted by crushing. P 2 measures 18.5 mm in length, the width anterior to the main cusp is 6.8 mm, and the width posterior to this cusp is 7.7 mm. A long posterior slope descends from the main cusp in contrast to the shorter anterior face, both devoid of accessory or cingular cusps. On all upper teeth the cingula are slightly developed basal swellings without sharp or distinct edges. On both P 2 and P 3 a weak, thin, enamel ridge runs from the main cusp anterolinguad to the cingulum on the anterior slope, and a similar ridge on the posterior slope runs to the posterolabial cingulum. P 3 is an enlarged version of P 2, measuring 20.3 mm in length; width anterior to main cusp, 8.2 mm; width posterior to this cusp, 10.6 mm. P 3 is somewhat more robust than P 2 and much more expanded at its base posterior to the main cusp. There are no accessory or cingular cusps. The anterior and posterior faces of P 3 are more nearly equal in length, and the tip of the main cusp shows flat apical wear. P 4 is a robust, massive tooth; M. obtusidens is the first of the larger temnocyonines to develop this crushing carnassial. P 4 has a short metastylar blade, an anteroposteriorly elongate stout paracone, and a greatly enlarged protocone that crushes against the p 4 heel. Shear is still accomplished to some degree by the lingual surfaces of the paracone and metastylar blade. The metastylar blade is directed outward at a 50 ° angle from the anteroposterior axis of the paracone. The blade measures 10.5 mm in length; the paracone measures 18.4 mm from the carnassial notch to its anterior base. A weak enamel ridge runs down the anterointernal face of the paracone to end in a tiny cingular cusp. Directly lingual to the paracone is the blunt, knoblike protocone: the protocone is separated from the paracone by a broad valley. Anteroposterior length of the protocone is 11 mm; greatest width of P 4 at the level of the protocone is 21.5 mm. Only a narrow embrasure (, 7 mm in length) remains between P 4 and M 1 to receive the trigonid of m 1, and a similarly reduced space also occurs in M. ferocior. M 1 measures 20.4 mm in length, 28.2 mm in width. In M. obtusidens the tooth comprises a labial part dominated by the paraand metacone, and an enlarged lingual half created by swelling of the lingual cingulum around the broad protocone region. Between the lingual and labial parts of the tooth is a prominent constriction, giving the tooth a ‘‘ waist’ ’ at the level of the protocone basin. The paracone is somewhat larger than the metacone; the parastyle, swollen labially and ventrally downturned, is more pronounced than the metastyle. Here, as in other large temnocyonines, M 1 has a ‘‘ folded’ ’ appearance as if the entire labial half were inwardly rotated toward the lingual half about an anteroposterior axis through the protocone basin. The protocone is centrally situated in a flat expanse of enamel. A preprotocrista runs from the protocone to the anterior cingulum but there is no postprotocrista nor para- and metaconules. A heavy swollen lingual cingulum, about equally developed throughout its extent, surrounds the protocone region. M 2 measures 10.5 mm in length, 17.9 mm in width. It is much smaller than M 1 and fits into the concavity on the posterior margin of the larger molar. The paracone is much larger than the abbreviated metacone, but only slightly taller. The stylar shelf and labial cingulum external to the paracone are better developed than these features labial to the metacone as a result of the reduction of the metacone. The protocone basin occurs at the constricted ‘‘ waist’ ’ of the tooth, and here also, as for M 1, the labial half of M 2 is rotated or ‘‘ folded’ ’ inward. The protocone is a small, low blunt cusp protruding from the enamel flat forming the lingual half of the tooth. It is surrounded by a swollen cingulum, which is considerably worn. M 3 was absent; there is no alveolus and there is no place on the maxilla posterior to M 2 for an M 3. The associated limb and vertebral elements are similar in form to skeletal elements of Mammacyon ferocior (F: AM 27562) from north of Keeline, Wyoming. Comparisons of the ulna, humerus, astragalus, and scapula show no differences other than size. The limb elements of M. ferocior, in association with its mandible, indicate a species larger than M. obtusidens (ACM 34 – 41). LACM 9194 — Only the complete left mandible is described here; the two isolated jaw fragments and canine only duplicate structure observable in the more complete lower jaw. LACM 9194 was initially described as Temnocyon percussor by Macdonald (1970: 61 – 62). The jaw is short and massive. Depth under the main cusp of p 2 is 38.4 mm, and 35.9 mm below the m 1 protoconid. Premolars and molars are large, robust teeth; the molars, especially m 2 – 3, are conspicuously tilted forward on the curvilinear margin of the ascending ramus. The inclined m 2 – 3 are characteristic of temnocyonines, consequently M 2 is often dorsally elevated relative to M 1 to accommodate this configuration of the lower molars. Such an M 2 is present in the holotype (ACM 34 - 41). The unworn teeth indicate a mature young adult. The canine is a large, recurved tooth, 38.9 mm in height from tip to enamel base, measured on the labial face. Its anteroposterior width is 19.1 mm measured at the base of the enamel; its labiolingual width is 12.6 mm. A wear groove produced by the upper canine begins near the tip on the posterior surface, continues down the posterior slope, trending slightly labiad, eventually terminating about 9.5 mm above the enamel base on the posterolabial face. Two fine enamel ridges traverse the tooth from tip to enamel base: the first courses down the center of the lingual face, the second traverses the posterolingual face. The single alveolus for p 1, although crushed, measures, 8 mm in length, 6.2 mm in width. Elongation of the large alveolus suggests that the tooth was directed anterolabially. The p 2 measures 14.4 mm in length, 5.8 mm in anterior width, and 6.4 mm in posterior width. There are no accessory or cingular cusps. A fine enamel ridge descends the somewhat steeper anterior face to the anterolingual corner of the tooth, and a similar ridge occupies the posterior face, ending at the posterolabial corner. The p 3 measures 17.7 mm in length, 6.4 mm in anterior width, and 7.8 mm in posterior width. There are no accessory cusps, but there is a small basal cusp situated at the center of the posterior cingulum. A thin enamel ridge descends the anterior face to the anterolingual corner; a second ridge traverses the posterior face to the basal cingulum cusp. The p 4 measures 20.4 mm in length, 7.5 mm in anterior width, and 9.7 mm in posterior width. A large posterior accessory cusp is labially situated half the distance down the posterior slope. A small basal cusp on the posterior cingulum lies below the posterior accessory cusp. A fine enamel ridge follows the anterior slope and ends in the anterolingual corner as in p 2 – 3, but a posterior ridge is largely obscured by development of the large posterior accessory cusp. The bases of P 3 and p 3 – 4 are posteriorly widened but this is less pronounced relative to M. ferocior or D. oryktes teeth where such widening of the posterior base is strongly developed. The m 1 measures 24.4 mm in length, 11.4 mm in posterior trigonid width, and 10.9 mm in greatest talonid width. Trigonid length is 17.4 mm. This is a robust, short, blunt-cusped carnassial that has lost the metaconid, although a small wear facet on the labial face of the protoconid shows that paraconid-protoconid shear is retained. The short, swollen paraconid blade is angled inward and is much lower in height than the principal cusp of p 4. The protoconid is compressed to form a blade running forward and downward to form the incisure with the paraconid. A short enamel ridge 4 mm in length descends the posterior surface of the protoconid to form the incisure with the hypoconid, a massive blunt cusp placed directly behind the protoconid and centrally situated on the talonid. There is also a low enamel swelling on the posterolingual wall of the protoconid that represents the vestige of the incisure once shared with the metaconid. Its presence indicates that the metaconid has probably been lost relatively recently in this lineage. There is no entoconid. The m 1 has a swollen, weakly differentiated cingulum, most evident on the labial side where it is sinuous: it rises below the protoconid, descends at the protoconid-hypoconid incisure, and rises again beneath the hypoconid (in contrast, the labial m 1 cingulum is straight in Delotrochanter). At the posterolingual corner of the m 1 talonid, the cingulum is slightly enlarged, creating a marked indentation of the cingulum anterior to this swelling (also found in M. ferocior). The elongate m 2 is diagnostic of the Mammacyon lineage in the Great Plains. Its length is 15.5 mm; greatest trigonid width, 9.6 mm; greatest talonid width, 8.7 mm: m 2 has a rectangular occlusal outline. The labially placed protoconid is the largest cusp. There is no metaconid but a small, distinct paraconid occupies the anterolingual corner of m 2. The only talonid cusp is a low, blunt, somewhat labially situated hypoconid. There is no entoconid. The pronounced inclination of m 2 (and m 3) on the edge of the ascending ramus of the mandible, tilted forward nearly 30 ° from the horizontal, further emphasizes the short toothrow and massive quality of the teeth. The m 3 is represented by a single alveolus, length 4.7 mm, width 4.1 mm, placed close against the posterior edge of m 2. Length of the toothrow from p 2 – m 2 is 86.2 mm; from the base of the enamel on the posterior face of the canine to the anterior rim of m 3 alveolus is 98.3 mm; from anterior rim of p 1 alveolus to posterior rim of m 3 alveolus is, 99 mm. LACM 5386 — I refer to M. obtusidens a partial maxilla with right P 4 – M 1 and the alveolus for the posterior root of P 3, from CIT Locality 29, Haystack Valley, Wheeler County, Oregon. It was found among unidentified material in the collection of the Los Angeles County Museum and has not been previously described. The teeth are most similar in form to ACM 34 - 41 (M. obtusidens) and F: AM 54134 (M. ferocior). This is the only specimen from the John Day beds assigned to Mammacyon; it represents a smaller individual than the holotype of M. obtusidens and is closer in size to LACM 9194. The alveolus (greatest width, 8.2 mm) for the posterior root of P 3 is very large, indicating a posteriorly broad premolar at least 9 mm in width. This alveolus indicates that P 3 was closely set against the base of P 4 as in the holotype. P 4 measures 21.8 mm in length, 18.2 mm in greatest width, and is characterized by the short yet robust metastylar blade relative to the large paracone and protocone. Metastylar blade length is 8.1 mm; width of the blade is 7.4 mm. The upper carnassial is nearly as wide as long, and shows blunted cusps with pronounced apical wear (there is only a weak vertical shear facet on the lingual face of the paracone-metastylar blade). The enormous protocone is responsible for the width of P 4: it extends as far toward the midline of the palate as does the M 1. An enlarged protocone is characteristic of Mammacyon; in Delotrochanter the P 4 protocone does not extend as far toward the midline. A slightly swollen cingulum surrounds P 4, and is somewhat more defined around the base of the metastylar blade than elsewhere on the tooth. A conspicuous valley separates the large blunted paracone from the much lower knoblike protocone. M 1 measures 17.8 mm in length, 24.8 mm estimated transverse width (the anterolingual cingulum is broken), and 13.1 mm in anteroposterior width of the protocone region. The form of the tooth is comparable to M 1 of ACM 34 - 41. The embrasure for m 1 between P 4 and M 1 is much reduced as in the holotype, thus there was probably no m 1 metaconid. In addition, the M 1 of LACM 5386 shows the ‘‘ folded’ ’ appearance in which the labial half of the tooth is rotated inward toward the lingual half as in ACM 34 - 41. The knoblike protocone of M 1 was isolated within the broadened protocone region and surrounded by a swollen lingual cingulum; a weak preprotocrista runs from protocone toward the anterior cingulum but no postprotocrista is apparent. Paracone, metacone, and protocone of M 1 are blunt cusps with flat apical wear surfaces. The paracone and metacone were once tall cusps but wear has reduced their height so that evidence of vertical shear on their lingual faces is equivocal. In mature individuals mastication emphasized the processing of hard food items, also suggested by the blunt, knoblike protocones of both M 1 and P 4. A vestige of the labial M 2 alveolus indicates that the tooth was small and fitted tightly against the posterior margin of M 1 in the same location as the holotype.
