Uchkudukodon nessovi ( McKenna, Kielan−Jaworowska, and Meng, 2000 )

Archibald, J. David & Averianov, Alexander O., 2006, Late Cretaceous asioryctitherian eutherian mammals from Uzbekistan and phylogenetic analysis of Asioryctitheria, Acta Palaeontologica Polonica 51 (2), pp. 351-376 : 361-364

Uchkudukodon nessovi ( McKenna, Kielan−Jaworowska, and Meng, 2000)

Figs. 5–7 , Tables 1, 2.

1991 Proteutheria [indet.]; Nessov and Kielan−Jaworowska 1991: fig. 1.

1993 Eutheria gen. and sp. nov.; Nessov 1993: fig. 1(4).

1995 Proteutheria gen. and sp. nov.; Nessov 1995: pl. 11: 7.

1997 Placentalia, probably Daulestes sp. nov.; Nessov 1997: pl. 48: 1. 2000 Eutheria [indet.]; Averianov 2000: fig. 30.8A, B.

2000 Daulestes nessovi sp. nov.; McKenna et al. 2000: 6, figs. 2–19.

Holotype: ZIN 79066 , a skull with occluded dentaries of a sub−adult, see McKenna et al. 2000 for a more complete description. Found in 1989.

Type locality and horizon: CBI−5a, Dzharakuduk, Kyzylkum Desert, Uzbekistan. Bissekty Formation, Upper Cretaceous (Turonian).

Referred specimens.— URBAC 04−221, skull fragment with right P5, M1–3, broken P2 and root for P4 (CBI−14); URBAC 98−124, left maxilla with M1 and alveoli or partial alveoli for P5 and M2 (CBI−14); URBAC 98−125, right M1 (CBI−14); URBAC 03−213, right M2 (CBI−14); ZIN 84968, right dentary with damaged p4–5, m1–2, and m 3 in matrix and roots for p2 (CDZH−17a, 1978[1983]); URBAC 04−181, right dentary with m2 and alveoli for p5, m1, 3 (CBI−14); ZIN 84967, right dentary with worn m2 and alveoli for m3 (CBI−14); URBAC 98−122, right dentary with worn m3 (CBI−14); URBAC 97−9, right dentary with erupting m3, posterior alveolus for p4 and alveoli for p5, m1–2 (CBI−14, 1997); URBAC 03−205, right dentary with talonid of erupting m3 and alveoli for p5 and m1–2 (CBI−14); URBAC 98−25, left dentary with talonid of erupting m3, posterior alveolus for m2 and parts of coronoid and angular processes (CBI−14); URBAC 03−203, left dentary with m3 erupting and alveoli for m1–2 (CBI−14); URBAC 98−123, right dentary with erupting m3 and alveoli for m1–2 (CBI−14); URBAC 04−42, right denary with alveoli for p2–5, m1–3 and angular process (CBI−14); URBAC 04−131, left dentary with posterior alveolus for p2 and alveoli for p4–5, m1–3 (CBI−14); ZIN 88443, right dentary with alveoli for p5, m1–3 (CBI−14, 1985); ZIN 88444, right dentary with alveoli for p5, m1–3 (CBI−14, 1987); URBAC 03−106, left dentary with alveoli for p5, m1–3 (CBI−14); URBAC 03−1, left dentary with alveoli for m1–2 and erupting m3, and parts of coronoid and angular processes (CBI−14); URBAC 03−3, right dentary with alveoli for m1–3 (CBI−14); URBAC 03−159, right dentary with alveoli for m1–3 (CBI−14); URBAC 03−191, left dentary with alveoli for m1–3 (CBI−4e); URBAC 97−11, right dentary with alveoli for m2–3 (CBI−14); URBAC 98−145, right dentary with alveoli for m2–3 (CBI−14); URBAC 99−107, right dentary with alveoli for m2 and erupting m3 (CBI−14); URBAC 03−198, left dentary with alveoli for m2 and erupting m3 (CBI−14); ZIN 88445, left dentary with alveoli for m2 and erupting m3 (CBI−14, 1984−1985).

Diagnosis.—As for the genus.

Description.—Here we describe only newly collected material of Uckudukodon nessovi . Description of the holotype skull and dentition ( ZIN 79066) can be found in McKenna et al. (2000); the specimen is illustrated herein for comparative purposes ( Fig. 5B ). URBAC 04−221 is a skull fragment including the right maxilla and lacrimal, parts of the nasal, frontal, and orbitosphenoid, and bearing P2, 5, M1–3, and roots of P4 ( Fig. 5A ; the partial P4 was lost during preparation). A large infraorbital foramen lies dorsal to the anterior part of P5. On the labial side of URBAC 98−124 there appears to be a jugal facet, which extends anteriorly almost to the posterior alveolar border of M1.

P2 is a two−rooted premolar with single−cusped low crown, heavily worn in URBAC 04−221. The posterior root is slightly longer than anterior root.

P5 is known only in URBAC 04−221. It is a semimolariform, three−rooted premolar. The paracone is large and occupies a central position on the crown. There is no metacone or metacone swelling, which may be a derived character for the genus. The ectoflexus is deep and the labial margin is almost symmetrical, with prominent metastylar and parastylar lobes. There is no stylocone or preparastyle and the preparacrista connects to the parastyle. The trigon is transversely wide and anteroposteriorly narrow, with a distinct protocone missing the posterior margin of the apex. There are no conules.

In addition to the M1s preserved in the skull ( ZIN 79066), M1 is known from three other specimens ( URBAC 98−124, 98−125 and 04−221), which are similar in morphology. The following description utilizes information from all specimens (see Fig. 6A ). The ectoflexus is shallow to moderately deep and the stylar shelf is about twice wider labial to the metacone than to the paracone. The parastylar lobe is large and anteriorly protruding, with a large parastyle and small preparastyle. The stylocone is intermediate in size between the parastyle and preparastyle. There are no distinct stylar cusps posterior to the stylocone. The metastylar lobe is close in size to the parastylar lobe, extending labially, but not very much posteriorly. The preparacrista is ridge−like but low, while the postmetacrista is ridge−like but higher. The metacone is smaller than the paracone and the bases of the cusps are merged. The conules are sharp, large, and winged; the paraconule is closer to the protocone than is the metaconule. The sharp internal cristae divide the trigon basin into concave conular basins and a deeper, concave primary trigon basin. The preparaconule crista, and to a lesser extent, the postmetaconule crista protrude beyond the margins of the crown creating lobe−like conules. The preparaconule crista extends anterolabially to the preparastyle forming a well−developed paracingulum. The postmetaconule crista is shorter and terminates dorsal to the posterior margin of the metacone. The protocone is lower than the paracone, but close in height to the metacone. The protocone ranges from quite narrow anteroposteriorly ( URBAC 04−221) to slightly expanded ( URBAC 98−124). In URBAC 98−125 there are very faint pre− and postcingula.

M2 is known from the holotype skull fragment, URBAC 04−221 , and an isolated tooth, URBAC 03−213 ( Fig. 6B ) . It differs from M1 mostly in its more symmetrical stylar lobes, a parastylar lobe that protrudes anterolabially rather than anteriorly, deeper ectoflexus, and a relatively longer preparacrista. The metastylar lobe is large, being only slightly smaller than the parastylar lobe in URBAC 03−213 , but is considerably smaller than the parastylar lobe in URBAC 04−221 .

M3 is known only in URBAC 04−221 ( Fig. 5A ). It is similar in morphology to CCMGE 12/12176, the holotype of Bulaklestes kezbe . The parastylar lobe is very wide (about a third of the tooth width) and protrudes much more labially than anteriorly (more anterolabially in D. kezbe ). The metacone is only half the size of the paracone (broken), but is still a distinct cusp. The paraconule is larger and is closer to the protocone than is the metaconule.

Ten of 21 specimens that preserve the posterior portion of the dentary come from individuals with m 3 in some stage of eruption. In these specimens the dentary is swollen surrounding the m3 alveoli, which are positioned sufficiently posteriorly so that they are on the anterior slope of the coronoid process. In adult specimens there is space between the m3 and the coronoid process. The depth of the dentary increases markedly with age (deepest in URBAC 03−106 at 2.2 mm). The posterior mental foramen is ventral to the anterior root of p5 (holotype, ZIN 84986), between the roots of p5 ( URBAC 04−131), ventral to the posterior root of p5 ( URBAC 97−9, 04−181), or between p5 and m1 ( URBAC 04−42). The masseteric fossa is deep and the coronoid is high. Usually there are more than two very small to small masseteric foramina, one of which is usually distinctly larger than others ( URBAC 03−1, 03−3, 04−42, 04−181, ZIN 88443, 88444, 84967). On the medial side of the coronoid process ( URBAC 98−25, 03−3, 04−181) there is a distinct, nearly horizontal line below the level of the alveolar border, delimiting ventrally the area for attachment of the temporalis muscle (“medial flange” of Kielan−Jaworowska 1981, but not of Kermack et al. 1973). URBAC 98−25 and 03−1 preserve the base of the mandibular angle and a large oval−shaped and posteriorly directed mandibular foramen.

In URBAC 04−42 there is a distinct diastema between two−rooted alveoli for p2 and p4, with a small round hole in the middle, apparently representing the partially filled alveolus for the unreplaced dp3 ( Fig. 7B ). In ZIN 84968 there are two roots for p2 and double−rooted p4 and p5, each lacking the protoconid apices. The p5 appears to be shorter than p4, although its length cannot be accurately measured as this tooth is not fully erupted and it remains partially encrusted with matrix. The labial side of p5 is exposed, showing that the talonid is expanded to the greatest labial extent of the crown.

The m1–2 are similar in structure, except that m1 has a smaller and more labially placed paraconid and a more open trigonid lingually. The m2 is longer than m 1 in ZIN 84968 and in the right ramus of the holotype, but shorter than m 1 in the left ramus of the holotype ( Table 2). The trigonid is twice the height of the talonid on unworn m1s and m2s. The protoconid is considerably higher than the metaconid. The paraconid is smaller than the metaconid and more labial in position on m1 compared to m2. There is a distinct, flat−bottomed, triangular trigonid basin, which is open lingually between the paraconid and metaconid bases. The precingulid is short, narrow, and terminates at (m1) or lingual to the paracristid notch (m2). The talonid is narrower than the trigonid. The hypoflexid is deep. The cristid obliqua terminates at the protocristid notch on m1 and at or slightly lingual to this notch on m2. The talonid basin is deep, especially in its anterolingual corner, where it received the protocone during centric occlusion. The hypoconid is the largest and tallest of the talonid cusps and the entoconid is the smallest. The hypoconulid is equidistant from the other talonid cusps and is ( URBAC 04−181 , Fig. 7A ) or is not ( ZIN 84967 , Fig. 7C ) posteriorly projecting .

The m3 was not known previously for Uchkudukodon nessovi . In the new sample it is represented by four specimens, but fully erupted only in URBAC 98−122 ( Fig. 7D ). The trigonid is much higher than the talonid, showing little anteroposterior compression, with a relatively large paraconid. The trigonid basin is distinct and open lingually between the paraconid and metaconid. The talonid is narrower and longer than the trigonid, with a rather small talonid basin and a deep hypoflexid. The cristid obliqua attaches to the trigonid at the protocristid notch and extends only slightly dorsal along the posterior trigonid wall. The talonid cusps are roughly equal in size and equidistant, and the hypoconulid is posteriorly projecting .

Measurements.—See Tables 1 and 2.

Figures

Fig. 5. Uchkudukodon nessovi (McKenna, Kielan−Jaworowska, and Meng, 2000); Dzharakuduk, Uzbekistan, Late Cretaceous (Turonian). A. URBAC 04−221, skull fragment with right (reversed in A2 and A3) P5, M1–3, broken P2 and root for P4, in occlusal (A1, stereopair) and labial (A2, stereopair) views; A3, labeled labial drawing showing P4 fragment before loss during preparation. B. ZIN 79066, a skull with occluded dentaries of a sub−adult, type, only left anterior two−thirds of skull shown here, in occlusal (B1, stereopair, reversed) and labial (B2, stereopair) views; B3, labeled labial drawing.

Fig. 6. Stereopairs of Uchkudukodon nessovi (McKenna, Kielan−Jaworowska, and Meng, 2000); Dzharakuduk, Uzbekistan, Late Cretaceous (Turonian). A. URBAC 98−124, M1 from left maxilla with M1 and alveoli or partial alveoli for P5 and M2, in occlusal (A1), labial (A2), and anterior (A3) views. B. URBAC 03−213, right M2, in occlusal (B1), labial (B2), and anterior (B3) views.

Fig. 7. Stereopairs of Uchkudukodon nessovi (McKenna, Kielan−Jaworowska, and Meng, 2000); Dzharakuduk, Uzbekistan, Late Cretaceous (Turonian). A. URBAC 04−181, m2 from right dentary with m2 and alveoli for p5, m1, 3; in lingual (A1), occlusal (A2), and labial (A3) views. B. URBAC 04−42, right denary with alveoli for p2–5, m1–3 and angular process, in occlusal view. C. ZIN 84967, m2 from right dentary with worn m2 and alveoli for m3; occlusal. D. URBAC 98−122, m3 from right dentary with worn m3, in occlusal view.